Re: [PATCH 0/1] PCI/MSI: add NULL check before use of msi_desc

[Hiraku Toyooka]

Hello Lorenzo,

Thank you for telling me.
I missed the patch.

Best regards,
Hiraku Toyooka

2018-01-16 18:30 GMT+09:00 Lorenzo Pieralisi <lorenzo.pieral...@arm.com>:
> On Tue, Jan 16, 2018 at 06:15:46PM +0900, Hiraku Toyooka wrote:
>> Hello,
>>
>> I found a NULL pointer dereference in PCI/MSI when I tried to run kdump
>> kernel on i.MX6(MCIMX6Q-SDB). This error occurs when masking MSI irq
>> which does not have msi_desc.
>> I added NULL check to avoid the error, and kdump worked fine. But I'm
>> not sure this is correct way. What do you think about this fix?
>
> It has been reported and it is being handled:
>
> https://marc.info/?l=linux-kernel=151321815226439=2
>
>> My environment:
>>  - Board:  MCIMX6Q-SDB
>>  - Kernel: 4.15.0-rc5 (commit: 464e1d5f23)
>>- used also as kdump kernel
>>- CONFIG_CRASH_DUMP and CONFIG_DEBUG_INFO are enabled based on 
>> imx_v6_v7_defconfig
>>  - U-Boot: u-boot-fslc (2017.11+fslc branch)
>>- built with meta-freescale (commit: bf7fd9cfe0)
>>
>>
>> Console log in failure case (patch not applied):
>>
>> root@imx6qdlsabresd:~# cat /proc/cmdline
>> console=ttymxc0,115200 root=PARTUUID=6c7357c5-02 rootwait rw quiet 
>> crashkernel=96M
>> root@imx6qdlsabresd:~# kexec --type zImage -p /boot/zImage 
>> --dtb=/boot/imx6q-sabresd.dtb --append="console=ttymxc0,115200 
>> root=/dev/mmcblk1p2 rootwait rw 3 maxcpus=1 reset_devices earlycon"
>> root@imx6qdlsabresd:~# echo c > /proc/sysrq-trigger
>> [   27.590895] sysrq: SysRq : Trigger a crash
>> [   27.595250] Unable to handle kernel NULL pointer dereference at virtual 
>> address 
>> ...(snip)...
>> [   27.808001] Backtrace:
>> [   27.810502] [] (sysrq_handle_crash) from [] 
>> (__handle_sysrq+0xd8/0x258)
>> [   27.818877]  r5:0063 r4:c101a6b0
>> [   27.822489] [] (__handle_sysrq) from [] 
>> (write_sysrq_trigger+0x78/0x90)
>> [   27.830871]  r10: r9:0002 r8: r7:e6490c00 r6: 
>> r5:01ced738
>> [   27.838719]  r4:0002
>> [   27.841290] [] (write_sysrq_trigger) from [] 
>> (proc_reg_write+0x68/0x90)
>> [   27.849664]  r5: r4:c04d2610
>> [   27.853277] [] (proc_reg_write) from [] 
>> (__vfs_write+0x34/0x134)
>> [   27.861050]  r9:0002 r8:01ced738 r7:0002 r6:e71a9f78 r5:c0297954 
>> r4:e6a49cc0
>> [   27.868824] [] (__vfs_write) from [] 
>> (vfs_write+0xa8/0x170)
>> [   27.876162]  r9:0002 r8:01ced738 r7:e71a9f78 r6:01ced738 r5:e6a49cc0 
>> r4:0002
>> [   27.883936] [] (vfs_write) from [] 
>> (SyS_write+0x44/0x98)
>> [   27.891014]  r9:0002 r8:01ced738 r7: r6: r5:e6a49cc0 
>> r4:e6a49cc0
>> [   27.898797] [] (SyS_write) from [] 
>> (ret_fast_syscall+0x0/0x28)
>> [   27.906395]  r9:e71a8000 r8:c01081a4 r7:0004 r6:b6f7eda8 r5:01ced738 
>> r4:0002
>> [   27.914169] Code: e3a04000 e5835000 ee074f9a ebf11af2 (e5c45000)
>> [   27.920332] CPU 1 will stop doing anything useful since another CPU has 
>> crashed
>> [   27.920342] CPU 0 will stop doing anything useful since another CPU has 
>> crashed
>> [   27.920351] CPU 2 will stop doing anything useful since another CPU has 
>> crashed
>> [   27.949670] Unable to handle kernel NULL pointer dereference at virtual 
>> address 0028
>> [   27.957798] pgd = c30fc51b
>> [   27.960529] [0028] *pgd=4a140831
>> [   27.964144] Internal error: Oops: 17 [#2] SMP ARM
>> [   27.968869] Modules linked in:
>> [   27.971962] CPU: 3 PID: 399 Comm: sh Not tainted 4.15.0-rc5-g3630470 #15
>> [   27.978685] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
>> [   27.985248] PC is at msi_set_mask_bit+0x18/0x6c
>> [   27.989805] LR is at pci_msi_mask_irq+0x14/0x18
>> [   27.994358] pc : []lr : []psr: a193
>> [   28.000647] sp : e71a9bb0  ip : e71a9bc8  fp : e71a9bc4
>> [   28.005892] r10: e000  r9 : e682e400  r8 : c101a72c
>> [   28.011140] r7 : e71a9c00  r6 : c102a504  r5 : 012f  r4 : 
>> [   28.017690] r3 : e642b400  r2 : 0001  r1 : 0001  r0 : e642b414
>> [   28.024241] Flags: NzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment 
>> none
>> [   28.031486] Control: 10c5387d  Table: 36ef804a  DAC: 0051
>> [   28.037255] Process sh (pid: 399, stack limit = 0x61f128fb)
>> [   28.042849] Stack: (0xe71a9bb0 to 0xe71aa000)
>> ...(snip)...
>> [   28.334445] Backtrace:
>> [   28.336937] [] (msi_set_mask_bit) from [] 
>> (pci_msi_mask_irq+0x14/0x18)
>> [   28.345224]  r5:012f r4:e642b

Re: [PATCH 0/1] PCI/MSI: add NULL check before use of msi_desc

[Hiraku Toyooka]

Hello Lorenzo,

Thank you for telling me.
I missed the patch.

Best regards,
Hiraku Toyooka

2018-01-16 18:30 GMT+09:00 Lorenzo Pieralisi :
> On Tue, Jan 16, 2018 at 06:15:46PM +0900, Hiraku Toyooka wrote:
>> Hello,
>>
>> I found a NULL pointer dereference in PCI/MSI when I tried to run kdump
>> kernel on i.MX6(MCIMX6Q-SDB). This error occurs when masking MSI irq
>> which does not have msi_desc.
>> I added NULL check to avoid the error, and kdump worked fine. But I'm
>> not sure this is correct way. What do you think about this fix?
>
> It has been reported and it is being handled:
>
> https://marc.info/?l=linux-kernel=151321815226439=2
>
>> My environment:
>>  - Board:  MCIMX6Q-SDB
>>  - Kernel: 4.15.0-rc5 (commit: 464e1d5f23)
>>- used also as kdump kernel
>>- CONFIG_CRASH_DUMP and CONFIG_DEBUG_INFO are enabled based on 
>> imx_v6_v7_defconfig
>>  - U-Boot: u-boot-fslc (2017.11+fslc branch)
>>- built with meta-freescale (commit: bf7fd9cfe0)
>>
>>
>> Console log in failure case (patch not applied):
>>
>> root@imx6qdlsabresd:~# cat /proc/cmdline
>> console=ttymxc0,115200 root=PARTUUID=6c7357c5-02 rootwait rw quiet 
>> crashkernel=96M
>> root@imx6qdlsabresd:~# kexec --type zImage -p /boot/zImage 
>> --dtb=/boot/imx6q-sabresd.dtb --append="console=ttymxc0,115200 
>> root=/dev/mmcblk1p2 rootwait rw 3 maxcpus=1 reset_devices earlycon"
>> root@imx6qdlsabresd:~# echo c > /proc/sysrq-trigger
>> [   27.590895] sysrq: SysRq : Trigger a crash
>> [   27.595250] Unable to handle kernel NULL pointer dereference at virtual 
>> address 
>> ...(snip)...
>> [   27.808001] Backtrace:
>> [   27.810502] [] (sysrq_handle_crash) from [] 
>> (__handle_sysrq+0xd8/0x258)
>> [   27.818877]  r5:0063 r4:c101a6b0
>> [   27.822489] [] (__handle_sysrq) from [] 
>> (write_sysrq_trigger+0x78/0x90)
>> [   27.830871]  r10: r9:0002 r8: r7:e6490c00 r6: 
>> r5:01ced738
>> [   27.838719]  r4:0002
>> [   27.841290] [] (write_sysrq_trigger) from [] 
>> (proc_reg_write+0x68/0x90)
>> [   27.849664]  r5: r4:c04d2610
>> [   27.853277] [] (proc_reg_write) from [] 
>> (__vfs_write+0x34/0x134)
>> [   27.861050]  r9:0002 r8:01ced738 r7:0002 r6:e71a9f78 r5:c0297954 
>> r4:e6a49cc0
>> [   27.868824] [] (__vfs_write) from [] 
>> (vfs_write+0xa8/0x170)
>> [   27.876162]  r9:0002 r8:01ced738 r7:e71a9f78 r6:01ced738 r5:e6a49cc0 
>> r4:0002
>> [   27.883936] [] (vfs_write) from [] 
>> (SyS_write+0x44/0x98)
>> [   27.891014]  r9:0002 r8:01ced738 r7: r6: r5:e6a49cc0 
>> r4:e6a49cc0
>> [   27.898797] [] (SyS_write) from [] 
>> (ret_fast_syscall+0x0/0x28)
>> [   27.906395]  r9:e71a8000 r8:c01081a4 r7:0004 r6:b6f7eda8 r5:01ced738 
>> r4:0002
>> [   27.914169] Code: e3a04000 e5835000 ee074f9a ebf11af2 (e5c45000)
>> [   27.920332] CPU 1 will stop doing anything useful since another CPU has 
>> crashed
>> [   27.920342] CPU 0 will stop doing anything useful since another CPU has 
>> crashed
>> [   27.920351] CPU 2 will stop doing anything useful since another CPU has 
>> crashed
>> [   27.949670] Unable to handle kernel NULL pointer dereference at virtual 
>> address 0028
>> [   27.957798] pgd = c30fc51b
>> [   27.960529] [0028] *pgd=4a140831
>> [   27.964144] Internal error: Oops: 17 [#2] SMP ARM
>> [   27.968869] Modules linked in:
>> [   27.971962] CPU: 3 PID: 399 Comm: sh Not tainted 4.15.0-rc5-g3630470 #15
>> [   27.978685] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
>> [   27.985248] PC is at msi_set_mask_bit+0x18/0x6c
>> [   27.989805] LR is at pci_msi_mask_irq+0x14/0x18
>> [   27.994358] pc : []lr : []psr: a193
>> [   28.000647] sp : e71a9bb0  ip : e71a9bc8  fp : e71a9bc4
>> [   28.005892] r10: e000  r9 : e682e400  r8 : c101a72c
>> [   28.011140] r7 : e71a9c00  r6 : c102a504  r5 : 012f  r4 : 
>> [   28.017690] r3 : e642b400  r2 : 0001  r1 : 0001  r0 : e642b414
>> [   28.024241] Flags: NzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment 
>> none
>> [   28.031486] Control: 10c5387d  Table: 36ef804a  DAC: 0051
>> [   28.037255] Process sh (pid: 399, stack limit = 0x61f128fb)
>> [   28.042849] Stack: (0xe71a9bb0 to 0xe71aa000)
>> ...(snip)...
>> [   28.334445] Backtrace:
>> [   28.336937] [] (msi_set_mask_bit) from [] 
>> (pci_msi_mask_irq+0x14/0x18)
>> [   28.345224]  r5:012f r4:e642b400
>> [   28.348844] [] (pci_msi_ma

[PATCH 0/1] PCI/MSI: add NULL check before use of msi_desc

[Hiraku Toyooka]

[   28.466423] 9e00:  0001 c10359a0  0004 0002 
 e71a9e54
[   28.474627] 9e20: e71a9e30 e71a9e40 c0118694 c04d1aa8 6013 
[   28.481268]  r8:0004 r7:e71a9e24 r6: r5:6013 r4:c04d1aa8
[   28.488012] [] (sysrq_handle_crash) from [] 
(__handle_sysrq+0xd8/0x258)
[   28.496385]  r5:0063 r4:c101a6b0
[   28.45] [] (__handle_sysrq) from [] 
(write_sysrq_trigger+0x78/0x90)
[   28.508375]  r10: r9:0002 r8: r7:e6490c00 r6: 
r5:01ced738
[   28.516223]  r4:0002
[   28.518791] [] (write_sysrq_trigger) from [] 
(proc_reg_write+0x68/0x90)
[   28.527164]  r5: r4:c04d2610
[   28.530774] [] (proc_reg_write) from [] 
(__vfs_write+0x34/0x134)
[   28.538547]  r9:0002 r8:01ced738 r7:0002 r6:e71a9f78 r5:c0297954 
r4:e6a49cc0
[   28.546320] [] (__vfs_write) from [] 
(vfs_write+0xa8/0x170)
[   28.553658]  r9:0002 r8:01ced738 r7:e71a9f78 r6:01ced738 r5:e6a49cc0 
r4:0002
[   28.561433] [] (vfs_write) from [] (SyS_write+0x44/0x98)
[   28.568511]  r9:0002 r8:01ced738 r7: r6: r5:e6a49cc0 
r4:e6a49cc0
[   28.576291] [] (SyS_write) from [] 
(ret_fast_syscall+0x0/0x28)
[   28.583890]  r9:e71a8000 r8:c01081a4 r7:0004 r6:b6f7eda8 r5:01ced738 
r4:0002
[   28.591662] Code: e24cb004 e590300c e1a02001 e5934008 (e5d43028)
[   28.597788] ---[ end trace b7f10c526986d6ea ]---
[   28.602430] Kernel panic - not syncing: Fatal exception
[   28.607716] ---[ end Kernel panic - not syncing: Fatal exception


Console log in success case (patch applied):

root@imx6qdlsabresd:~# cat /proc/cmdline
console=ttymxc0,115200 root=PARTUUID=6c7357c5-02 rootwait rw quiet 
crashkernel=96M
root@imx6qdlsabresd:~# kexec --type zImage -p /boot/zImage 
--dtb=/boot/imx6q-sabresd.dtb --append="console=ttymxc0,115200 
root=/dev/mmcblk1p2 rootwait rw 3 maxcpus=1 reset_devices earlycon"
root@imx6qdlsabresd:~# echo c > /proc/sysrq-trigger
[   42.951366] sysrq: SysRq : Trigger a crash
[   42.955711] Unable to handle kernel NULL pointer dereference at virtual 
address 
...(snip)...
[   43.167849] Backtrace:
[   43.170314] [] (sysrq_handle_crash) from [] 
(__handle_sysrq+0xd8/0x258)
[   43.178671]  r5:0063 r4:c101a6b0
[   43.182258] [] (__handle_sysrq) from [] 
(write_sysrq_trigger+0x78/0x90)
[   43.190617]  r10: r9:0002 r8: r7:e6490c00 r6: 
r5:003b2738
[   43.198450]  r4:0002
[   43.200995] [] (write_sysrq_trigger) from [] 
(proc_reg_write+0x68/0x90)
[   43.209350]  r5: r4:c04d2614
[   43.212937] [] (proc_reg_write) from [] 
(__vfs_write+0x34/0x134)
[   43.220688]  r9:0002 r8:003b2738 r7:0002 r6:e6f33f78 r5:c0297954 
r4:e6b47680
[   43.228439] [] (__vfs_write) from [] 
(vfs_write+0xa8/0x170)
[   43.235756]  r9:0002 r8:003b2738 r7:e6f33f78 r6:003b2738 r5:e6b47680 
r4:0002
[   43.243508] [] (vfs_write) from [] (SyS_write+0x44/0x98)
[   43.250564]  r9:0002 r8:003b2738 r7: r6: r5:e6b47680 
r4:e6b47680
[   43.258320] [] (SyS_write) from [] 
(ret_fast_syscall+0x0/0x28)
[   43.265896]  r9:e6f32000 r8:c01081a4 r7:0004 r6:b6f0eda8 r5:003b2738 
r4:0002
[   43.273647] Code: e3a04000 e5835000 ee074f9a ebf11af1 (e5c45000)
[   43.279767] CPU 3 will stop doing anything useful since another CPU has 
crashed
[   43.279771] CPU 2 will stop doing anything useful since another CPU has 
crashed
[   43.279775] CPU 0 will stop doing anything useful since another CPU has 
crashed
[   43.301962] Loading crashdump kernel...
[   43.305886] Bye!
[0.00] Booting Linux on physical CPU 0x1
[0.00] Linux version 4.15.0-rc5-g13f566e (miracle@ar) (gcc version 
5.4.0 20160609 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.4)) #14 SMP Tue Jan 16 
06:33:27 UTC 2018


Hiraku Toyooka (1):
  PCI/MSI: add NULL check before use of msi_desc

 drivers/pci/msi.c | 3 +++
 1 file changed, 3 insertions(+)

-- 
2.7.4

[PATCH 0/1] PCI/MSI: add NULL check before use of msi_desc

[Hiraku Toyooka]

[   28.466423] 9e00:  0001 c10359a0  0004 0002 
 e71a9e54
[   28.474627] 9e20: e71a9e30 e71a9e40 c0118694 c04d1aa8 6013 
[   28.481268]  r8:0004 r7:e71a9e24 r6: r5:6013 r4:c04d1aa8
[   28.488012] [] (sysrq_handle_crash) from [] 
(__handle_sysrq+0xd8/0x258)
[   28.496385]  r5:0063 r4:c101a6b0
[   28.45] [] (__handle_sysrq) from [] 
(write_sysrq_trigger+0x78/0x90)
[   28.508375]  r10: r9:0002 r8: r7:e6490c00 r6: 
r5:01ced738
[   28.516223]  r4:0002
[   28.518791] [] (write_sysrq_trigger) from [] 
(proc_reg_write+0x68/0x90)
[   28.527164]  r5: r4:c04d2610
[   28.530774] [] (proc_reg_write) from [] 
(__vfs_write+0x34/0x134)
[   28.538547]  r9:0002 r8:01ced738 r7:0002 r6:e71a9f78 r5:c0297954 
r4:e6a49cc0
[   28.546320] [] (__vfs_write) from [] 
(vfs_write+0xa8/0x170)
[   28.553658]  r9:0002 r8:01ced738 r7:e71a9f78 r6:01ced738 r5:e6a49cc0 
r4:0002
[   28.561433] [] (vfs_write) from [] (SyS_write+0x44/0x98)
[   28.568511]  r9:0002 r8:01ced738 r7: r6: r5:e6a49cc0 
r4:e6a49cc0
[   28.576291] [] (SyS_write) from [] 
(ret_fast_syscall+0x0/0x28)
[   28.583890]  r9:e71a8000 r8:c01081a4 r7:0004 r6:b6f7eda8 r5:01ced738 
r4:0002
[   28.591662] Code: e24cb004 e590300c e1a02001 e5934008 (e5d43028)
[   28.597788] ---[ end trace b7f10c526986d6ea ]---
[   28.602430] Kernel panic - not syncing: Fatal exception
[   28.607716] ---[ end Kernel panic - not syncing: Fatal exception


Console log in success case (patch applied):

root@imx6qdlsabresd:~# cat /proc/cmdline
console=ttymxc0,115200 root=PARTUUID=6c7357c5-02 rootwait rw quiet 
crashkernel=96M
root@imx6qdlsabresd:~# kexec --type zImage -p /boot/zImage 
--dtb=/boot/imx6q-sabresd.dtb --append="console=ttymxc0,115200 
root=/dev/mmcblk1p2 rootwait rw 3 maxcpus=1 reset_devices earlycon"
root@imx6qdlsabresd:~# echo c > /proc/sysrq-trigger
[   42.951366] sysrq: SysRq : Trigger a crash
[   42.955711] Unable to handle kernel NULL pointer dereference at virtual 
address 
...(snip)...
[   43.167849] Backtrace:
[   43.170314] [] (sysrq_handle_crash) from [] 
(__handle_sysrq+0xd8/0x258)
[   43.178671]  r5:0063 r4:c101a6b0
[   43.182258] [] (__handle_sysrq) from [] 
(write_sysrq_trigger+0x78/0x90)
[   43.190617]  r10: r9:0002 r8: r7:e6490c00 r6: 
r5:003b2738
[   43.198450]  r4:0002
[   43.200995] [] (write_sysrq_trigger) from [] 
(proc_reg_write+0x68/0x90)
[   43.209350]  r5: r4:c04d2614
[   43.212937] [] (proc_reg_write) from [] 
(__vfs_write+0x34/0x134)
[   43.220688]  r9:0002 r8:003b2738 r7:0002 r6:e6f33f78 r5:c0297954 
r4:e6b47680
[   43.228439] [] (__vfs_write) from [] 
(vfs_write+0xa8/0x170)
[   43.235756]  r9:0002 r8:003b2738 r7:e6f33f78 r6:003b2738 r5:e6b47680 
r4:0002
[   43.243508] [] (vfs_write) from [] (SyS_write+0x44/0x98)
[   43.250564]  r9:0002 r8:003b2738 r7: r6: r5:e6b47680 
r4:e6b47680
[   43.258320] [] (SyS_write) from [] 
(ret_fast_syscall+0x0/0x28)
[   43.265896]  r9:e6f32000 r8:c01081a4 r7:0004 r6:b6f0eda8 r5:003b2738 
r4:0002
[   43.273647] Code: e3a04000 e5835000 ee074f9a ebf11af1 (e5c45000)
[   43.279767] CPU 3 will stop doing anything useful since another CPU has 
crashed
[   43.279771] CPU 2 will stop doing anything useful since another CPU has 
crashed
[   43.279775] CPU 0 will stop doing anything useful since another CPU has 
crashed
[   43.301962] Loading crashdump kernel...
[   43.305886] Bye!
[0.00] Booting Linux on physical CPU 0x1
[0.00] Linux version 4.15.0-rc5-g13f566e (miracle@ar) (gcc version 
5.4.0 20160609 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.4)) #14 SMP Tue Jan 16 
06:33:27 UTC 2018


Hiraku Toyooka (1):
  PCI/MSI: add NULL check before use of msi_desc

 drivers/pci/msi.c | 3 +++
 1 file changed, 3 insertions(+)

-- 
2.7.4

[PATCH 1/1] PCI/MSI: add NULL check before use of msi_desc

[Hiraku Toyooka]

On starting kdump kernel in arm, arm64 and powerpc, chip->irq_mask() is
called for each irq_data to mask interrupts. For MSI irqs,
pci_msi_mask_irq() is called even when the irq_data doesn't have a link
to msi_desc. This results in a NULL pointer dereference.

This patch fixes the above error by avoiding NULL msi_desc use.

Signed-off-by: Hiraku Toyooka <hiraku.toyo...@cybertrust.co.jp>
Cc: Bjorn Helgaas <bhelg...@google.com>
Cc: Richard Zhu <hongxing@nxp.com>
Cc: Lucas Stach <l.st...@pengutronix.de>
Cc: Jingoo Han <jingooh...@gmail.com>
Cc: Joao Pinto <joao.pi...@synopsys.com>
Cc: Lorenzo Pieralisi <lorenzo.pieral...@arm.com>
Cc: Russell King <li...@armlinux.org.uk>
Cc: Will Deacon <will.dea...@arm.com>
---
 drivers/pci/msi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index e066071..a6ee274 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -227,6 +227,9 @@ static void msi_set_mask_bit(struct irq_data *data, u32 
flag)
 {
struct msi_desc *desc = irq_data_get_msi_desc(data);
 
+   if (!desc)
+   return;
+
if (desc->msi_attrib.is_msix) {
msix_mask_irq(desc, flag);
readl(desc->mask_base); /* Flush write to device */
-- 
2.7.4

[PATCH 1/1] PCI/MSI: add NULL check before use of msi_desc

[Hiraku Toyooka]

On starting kdump kernel in arm, arm64 and powerpc, chip->irq_mask() is
called for each irq_data to mask interrupts. For MSI irqs,
pci_msi_mask_irq() is called even when the irq_data doesn't have a link
to msi_desc. This results in a NULL pointer dereference.

This patch fixes the above error by avoiding NULL msi_desc use.

Signed-off-by: Hiraku Toyooka 
Cc: Bjorn Helgaas 
Cc: Richard Zhu 
Cc: Lucas Stach 
Cc: Jingoo Han 
Cc: Joao Pinto 
Cc: Lorenzo Pieralisi 
Cc: Russell King 
Cc: Will Deacon 
---
 drivers/pci/msi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index e066071..a6ee274 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -227,6 +227,9 @@ static void msi_set_mask_bit(struct irq_data *data, u32 
flag)
 {
struct msi_desc *desc = irq_data_get_msi_desc(data);
 
+   if (!desc)
+   return;
+
if (desc->msi_attrib.is_msix) {
msix_mask_irq(desc, flag);
readl(desc->mask_base); /* Flush write to device */
-- 
2.7.4

[PATCH 1/5] ramoops: use persistent_ram_free() instead of kfree() for freeing prz

[Hiraku Toyooka]

persistent_ram_zone(=prz) structures are allocated by
persistent_ram_new(), which includes vmap() or ioremap(). But they
are currently freed by kfree(). We should use persistent_ram_free()
to correct this asymmetry usage.

Signed-off-by: Hiraku Toyooka 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: Tony Luck 
Cc: linux-kernel@vger.kernel.org
---
 fs/pstore/ram.c |6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 6c26c4d..6363768 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -567,11 +567,11 @@ fail_buf:
kfree(cxt->pstore.buf);
 fail_clear:
cxt->pstore.bufsize = 0;
-   kfree(cxt->mprz);
+   persistent_ram_free(cxt->mprz);
 fail_init_mprz:
-   kfree(cxt->fprz);
+   persistent_ram_free(cxt->fprz);
 fail_init_fprz:
-   kfree(cxt->cprz);
+   persistent_ram_free(cxt->cprz);
 fail_init_cprz:
ramoops_free_przs(cxt);
 fail_out:

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[PATCH 3/5] pstore: support multiple pmsg instances

[Hiraku Toyooka]

This patch enables pmsg to deal with multiple instances. One possible
use is content priority control on limited persistent store space. By
using different buffers, we can prevent important messages from being
overwritten by less important messages.

When a pstore backend module specifies the number of instances (num_pmsg)
in pstore_info, multiple /dev/pmsg[ID] appear. (ID is an integer
starting at 0. It corresponds to minor number of the each char device.)
Writes to each /dev/pmsg[ID] are isolated each other. After reboot, the
contents are available in /sys/fs/pstore/pmsg-[backend]-[ID].

Signed-off-by: Hiraku Toyooka 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: Tony Luck 
Cc: linux-kernel@vger.kernel.org
---
 fs/pstore/pmsg.c   |   20 ++--
 include/linux/pstore.h |1 +
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/fs/pstore/pmsg.c b/fs/pstore/pmsg.c
index feb5dd2..3467d63 100644
--- a/fs/pstore/pmsg.c
+++ b/fs/pstore/pmsg.c
@@ -50,8 +50,8 @@ static ssize_t write_pmsg(struct file *file, const char 
__user *buf,
vfree(buffer);
return -EFAULT;
}
-   psinfo->write_buf(PSTORE_TYPE_PMSG, 0, , 0, buffer, 0, c,
- psinfo);
+   psinfo->write_buf(PSTORE_TYPE_PMSG, 0, ,
+ iminor(file->f_inode), buffer, 0, c, psinfo);
 
i += c;
}
@@ -83,6 +83,7 @@ static char *pmsg_devnode(struct device *dev, umode_t *mode)
 void pstore_register_pmsg(void)
 {
struct device *pmsg_device;
+   int i = 0;
 
pmsg_major = register_chrdev(0, PMSG_NAME, _fops);
if (pmsg_major < 0) {
@@ -103,9 +104,24 @@ void pstore_register_pmsg(void)
pr_err("failed to create device\n");
goto err_device;
}
+
+   /* allocate additional /dev/pmsg[ID] */
+   for (i = 1; i < psinfo->num_pmsg; i++) {
+   struct device *pmsg_device;
+
+   pmsg_device = device_create(pmsg_class, NULL,
+   MKDEV(pmsg_major, i), NULL, "%s%d",
+   PMSG_NAME, i);
+   if (IS_ERR(pmsg_device)) {
+   pr_err("failed to create device\n");
+   goto err_device;
+   }
+   }
return;
 
 err_device:
+   for (i--; i >= 0; i--)
+   device_destroy(pmsg_class, MKDEV(pmsg_major, i));
class_destroy(pmsg_class);
 err_class:
unregister_chrdev(pmsg_major, PMSG_NAME);
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index 8e7a25b..7cffc9d 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -54,6 +54,7 @@ struct pstore_info {
size_t  bufsize;
struct mutexread_mutex; /* serialize open/read/close */
int flags;
+   unsigned intnum_pmsg;
int (*open)(struct pstore_info *psi);
int (*close)(struct pstore_info *psi);
ssize_t (*read)(u64 *id, enum pstore_type_id *type,

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[PATCH 2/5] ramoops: introduce generic init/free functions for prz

[Hiraku Toyooka]

We modifies initialization and freeing code for prz for generic usage.
This change

 * add generic function __ramoops_init_prz() to reduce redundancy
   between ramoops_init_prz() and ramoops_init_przs().
 * rename 'przs' member in struct ramoops_context to 'dprzs' so that
   it stands for 'dump przs'.
 * rename ramoops_init_prz() to ramoops_init_dprzs().
 * change parameter of ramoops_free_przs() from struct ramoops_context *
   into struct persistent_ram_zone * in order to make it available for
   all prz array.

Signed-off-by: Hiraku Toyooka 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: Tony Luck 
Cc: linux-kernel@vger.kernel.org
---
 fs/pstore/ram.c |   63 +++
 1 file changed, 35 insertions(+), 28 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 6363768..89cc90e 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -83,7 +83,7 @@ MODULE_PARM_DESC(ramoops_ecc,
"bytes ECC)");
 
 struct ramoops_context {
-   struct persistent_ram_zone **przs;
+   struct persistent_ram_zone **dprzs;
struct persistent_ram_zone *cprz;
struct persistent_ram_zone *fprz;
struct persistent_ram_zone *mprz;
@@ -199,7 +199,7 @@ static ssize_t ramoops_pstore_read(u64 *id, enum 
pstore_type_id *type,
 
/* Find the next valid persistent_ram_zone for DMESG */
while (cxt->dump_read_cnt < cxt->max_dump_cnt && !prz) {
-   prz = ramoops_get_next_prz(cxt->przs, >dump_read_cnt,
+   prz = ramoops_get_next_prz(cxt->dprzs, >dump_read_cnt,
   cxt->max_dump_cnt, id, type,
   PSTORE_TYPE_DMESG, 1);
if (!prz_ok(prz))
@@ -314,10 +314,10 @@ static int notrace ramoops_pstore_write_buf(enum 
pstore_type_id type,
if (part != 1)
return -ENOSPC;
 
-   if (!cxt->przs)
+   if (!cxt->dprzs)
return -ENOSPC;
 
-   prz = cxt->przs[cxt->dump_write_cnt];
+   prz = cxt->dprzs[cxt->dump_write_cnt];
 
hlen = ramoops_write_kmsg_hdr(prz, compressed);
if (size + hlen > prz->buffer_size)
@@ -339,7 +339,7 @@ static int ramoops_pstore_erase(enum pstore_type_id type, 
u64 id, int count,
case PSTORE_TYPE_DMESG:
if (id >= cxt->max_dump_cnt)
return -EINVAL;
-   prz = cxt->przs[id];
+   prz = cxt->dprzs[id];
break;
case PSTORE_TYPE_CONSOLE:
prz = cxt->cprz;
@@ -371,21 +371,24 @@ static struct ramoops_context oops_cxt = {
},
 };
 
-static void ramoops_free_przs(struct ramoops_context *cxt)
+static void ramoops_free_przs(struct persistent_ram_zone **przs)
 {
int i;
 
-   cxt->max_dump_cnt = 0;
-   if (!cxt->przs)
+   if (!przs)
return;
 
-   for (i = 0; !IS_ERR_OR_NULL(cxt->przs[i]); i++)
-   persistent_ram_free(cxt->przs[i]);
-   kfree(cxt->przs);
+   for (i = 0; i < !IS_ERR_OR_NULL(przs[i]); i++)
+   persistent_ram_free(przs[i]);
+   kfree(przs);
 }
 
-static int ramoops_init_przs(struct device *dev, struct ramoops_context *cxt,
-phys_addr_t *paddr, size_t dump_mem_sz)
+static int __ramoops_init_prz(struct device *dev, struct ramoops_context *cxt,
+ struct persistent_ram_zone **prz,
+ phys_addr_t *paddr, size_t sz, u32 sig, bool zap);
+
+static int ramoops_init_dprzs(struct device *dev, struct ramoops_context *cxt,
+ phys_addr_t *paddr, size_t dump_mem_sz)
 {
int err = -ENOMEM;
int i;
@@ -402,29 +405,24 @@ static int ramoops_init_przs(struct device *dev, struct 
ramoops_context *cxt,
if (!cxt->max_dump_cnt)
return -ENOMEM;
 
-   cxt->przs = kzalloc(sizeof(*cxt->przs) * cxt->max_dump_cnt,
+   cxt->dprzs = kcalloc(cxt->max_dump_cnt, sizeof(*cxt->dprzs),
 GFP_KERNEL);
-   if (!cxt->przs) {
+   if (!cxt->dprzs) {
dev_err(dev, "failed to initialize a prz array for dumps\n");
goto fail_prz;
}
 
for (i = 0; i < cxt->max_dump_cnt; i++) {
-   cxt->przs[i] = persistent_ram_new(*paddr, cxt->record_size, 0,
- >ecc_info,
- cxt->memtype);
-   if (IS_ERR(cxt->przs[i])) {
-   err = PTR_ERR(cxt->przs[i]);
-   dev_err(dev, "failed to request mem region 
(0x%zx@0x%llx): %d\n",
-   cxt->record_size, (unsigned long long)*pad

[PATCH 5/5] selftests/pstore: add testcases for multiple pmsg instances

[Hiraku Toyooka]

To test multiple pmsg, we should check that /dev/pmsg[N] (N > 0) is
available. After reboot, we should check that pmsg-[backend]-[N] which
keeps content is detected even if pmsg-[backend]-[N-M] (0 < M <= N)
doesn't exist due to lack of contents.

So we add the following testcases.
 - pstore_tests
   - Write unique string to the last /dev/pmsgN
 - pstore_post_reboot_tests
   - Check the last pmsg area is detected

Signed-off-by: Hiraku Toyooka 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: Shuah Khan 
Cc: Tony Luck 
Cc: linux-...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 tools/testing/selftests/pstore/common_tests|   21 ++--
 .../selftests/pstore/pstore_post_reboot_tests  |   27 +++-
 tools/testing/selftests/pstore/pstore_tests|   16 ++--
 3 files changed, 47 insertions(+), 17 deletions(-)

diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
index 3ea64d7..566a25d 100755
--- a/tools/testing/selftests/pstore/common_tests
+++ b/tools/testing/selftests/pstore/common_tests
@@ -27,9 +27,9 @@ show_result() { # result_value
 }
 
 check_files_exist() { # type of pstorefs file
-if [ -e ${1}-${backend}-0 ]; then
+if [ -e ${1}0 ]; then
prlog "ok"
-   for f in `ls ${1}-${backend}-*`; do
+   for f in `ls ${1}*`; do
 prlog -e "\t${f}"
done
 else
@@ -53,6 +53,23 @@ operate_files() { # tested value, files, operation
 fi
 }
 
+check_pmsg_content() { # pmsg filename
+prev_uuid=`cat $TOP_DIR/prev_uuid`
+if [ $? -eq 0 ]; then
+   nr_matched=`grep -c "$TEST_STRING_PATTERN" $1`
+   if [ "$nr_matched" = "1" ]; then
+   grep -q "$TEST_STRING_PATTERN"$prev_uuid $1
+   show_result $?
+   else
+   prlog "FAIL"
+   rc=1
+   fi
+else
+   prlog "FAIL"
+   rc=1
+fi
+}
+
 # Parameters
 TEST_STRING_PATTERN="Testing pstore: uuid="
 UUID=`cat /proc/sys/kernel/random/uuid`
diff --git a/tools/testing/selftests/pstore/pstore_post_reboot_tests 
b/tools/testing/selftests/pstore/pstore_post_reboot_tests
index 6ccb154..272498f 100755
--- a/tools/testing/selftests/pstore/pstore_post_reboot_tests
+++ b/tools/testing/selftests/pstore/pstore_post_reboot_tests
@@ -35,13 +35,13 @@ fi
 cd ${mount_point}
 
 prlog -n "Checking dmesg files exist in pstore filesystem ... "
-check_files_exist dmesg
+check_files_exist dmesg-${backend}-
 
 prlog -n "Checking console files exist in pstore filesystem ... "
-check_files_exist console
+check_files_exist console-${backend}-
 
 prlog -n "Checking pmsg files exist in pstore filesystem ... "
-check_files_exist pmsg
+check_files_exist pmsg-${backend}-
 
 prlog -n "Checking dmesg files contain oops end marker"
 grep_end_trace() {
@@ -54,16 +54,19 @@ prlog -n "Checking console file contains oops end marker 
... "
 grep -q "\---\[ end trace" console-${backend}-0
 show_result $?
 
-prlog -n "Checking pmsg file properly keeps the content written before crash 
... "
-prev_uuid=`cat $TOP_DIR/prev_uuid`
-if [ $? -eq 0 ]; then
-nr_matched=`grep -c "$TEST_STRING_PATTERN" pmsg-${backend}-0`
-if [ $nr_matched -eq 1 ]; then
-   grep -q "$TEST_STRING_PATTERN"$prev_uuid pmsg-${backend}-0
-   show_result $?
+prlog -n "Checking pmsg-"${backend}"-0 properly keeps the content written 
before crash ... "
+check_pmsg_content pmsg-${backend}-0
+
+prlog -n "Checking the last pmsg area is detected "
+last_num_pmsg=`ls -v pmsg-* | tail -n1 | sed -e 
"s/^pmsg-${backend}-\([0-9]*\).*$/\1/"`
+last_num_devpmsg=`ls -v /dev/pmsg* | tail -n1 | sed -e 
"s/^\/dev\/pmsg\([0-9]*\).*$/\1/"`
+#checks the last number of pmsg-*-* and /dev/pmsg* correspond.
+if [ "$last_num_pmsg" -eq "$last_num_devpmsg" ]; then
+if [ "$last_num_pmsg" = "0" ]; then
+   prlog "... No multiple pmsg-*-* exists. We skip this testcase."
 else
-   prlog "FAIL"
-   rc=1
+   prlog -n "(pmsg-${backend}-${last_num_pmsg}) ... "
+   check_pmsg_content pmsg-${backend}-${last_num_pmsg}
 fi
 else
 prlog "FAIL"
diff --git a/tools/testing/selftests/pstore/pstore_tests 
b/tools/testing/selftests/pstore/pstore_tests
index f25d2a3..5abf0e5 100755
--- a/tools/testing/selftests/pstore/pstore_tests
+++ b/tools/testing/selftests/pstore/pstore_tests
@@ -13,9 +13,8 @@ prlog -n "Checking pstore console is registered ... "
 dmesg | grep -q "console \[pstore"
 show_result $?
 
-prlog -n "Checking /dev/pmsg0 exists ... "
-test -e /dev/pmsg0
-show_result $?
+prlog -n "Checking /dev/pmsg files exist ... "
+check_fil

[PATCH 0/5] pstore: ramoops: support multiple pmsg instances

[Hiraku Toyooka]

The following series implements multiple pmsg. This feature allows
userspace program to control individual content aging or priority.

If a pstore backend module(e.g. ramoops) requires the multiple pmsg
instances when registering itself to pstore, multiple /dev/pmsg[ID]
are created. Writes to each /dev/pmsg[ID] are isolated each other. After
reboot, the contents are available in /sys/fs/pstore/pmsg-[backend]-[ID].

In addition, we add multiple pmsg support for ramoops. We can
specify multiple pmsg area size by its module parameter as follows.

 pmsg_size=0x1000,0x2000,...

---

Hiraku Toyooka (5):
  ramoops: use persistent_ram_free() instead of kfree() for freeing prz
  ramoops: introduce generic init/free functions for prz
  pstore: support multiple pmsg instances
  ramoops: support multiple pmsg instances
  selftests/pstore: add testcases for multiple pmsg instances


 Documentation/ramoops.txt  |   22 ++
 fs/pstore/pmsg.c   |   20 ++
 fs/pstore/ram.c|  213 +++-
 include/linux/pstore.h |1 
 include/linux/pstore_ram.h |8 +
 tools/testing/selftests/pstore/common_tests|   21 ++
 .../selftests/pstore/pstore_post_reboot_tests  |   27 +--
 tools/testing/selftests/pstore/pstore_tests|   16 +-
 8 files changed, 257 insertions(+), 71 deletions(-)

--
Hiraku Toyooka
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[PATCH 4/5] ramoops: support multiple pmsg instances

[Hiraku Toyooka]

This patch enables ramoops to deal with multiple pmsg instances.
We can configure the size of each buffers by its module parameter
as follows.

  pmsg_size=0x1000,0x2000,...

Then, the ramoops allocates multiple buffers and tells the number
of buffers to pstore to create multiple /dev/pmsg[ID].

Signed-off-by: Hiraku Toyooka 
Cc: Jonathan Corbet 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: Tony Luck 
Cc: linux-...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 Documentation/ramoops.txt  |   22 +++
 fs/pstore/ram.c|  146 ++--
 include/linux/pstore_ram.h |8 ++
 3 files changed, 154 insertions(+), 22 deletions(-)

diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
index 5d86756..cff6ac7 100644
--- a/Documentation/ramoops.txt
+++ b/Documentation/ramoops.txt
@@ -126,3 +126,25 @@ file. Here is an example of usage:
  0 811d9c54  8101a7a0  __const_udelay <- 
native_machine_emergency_restart+0x110/0x1e0
  0 811d9c34  811d9c80  __delay <- __const_udelay+0x30/0x40
  0 811d9d14  811d9c3f  delay_tsc <- __delay+0xf/0x20
+
+6. Pmsg support
+
+Ramoops supports pmsg - logging userspace mesages in persistent store. By
+default, one pmsg area becomes available in ramoops. You can write data into
+/dev/pmsg0, e.g.:
+
+ # echo foo > /dev/pmsg0
+
+After reboot, the stored data can be read from pmsg-ramoops-0 on the pstore
+filesystem.
+
+You can specify size of the pmsg area by additional kernel command line, e.g.:
+
+ "ramoops.pmsg_size=0x1000"
+
+You can also use multiple pmsg areas, e.g.:
+
+ "ramoops.pmsg_size=0x1000,0x2000,..."
+
+Then, pmsg0, pmsg1, ... will appear on /dev. This is useful to control
+individual content aging or priority.
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 89cc90e..1d1378c 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -51,8 +51,8 @@ static ulong ramoops_ftrace_size = MIN_MEM_SIZE;
 module_param_named(ftrace_size, ramoops_ftrace_size, ulong, 0400);
 MODULE_PARM_DESC(ftrace_size, "size of ftrace log");
 
-static ulong ramoops_pmsg_size = MIN_MEM_SIZE;
-module_param_named(pmsg_size, ramoops_pmsg_size, ulong, 0400);
+static char *ramoops_pmsg_size_str;
+module_param_named(pmsg_size, ramoops_pmsg_size_str, charp, 0400);
 MODULE_PARM_DESC(pmsg_size, "size of user space message log");
 
 static ulong mem_address;
@@ -86,14 +86,14 @@ struct ramoops_context {
struct persistent_ram_zone **dprzs;
struct persistent_ram_zone *cprz;
struct persistent_ram_zone *fprz;
-   struct persistent_ram_zone *mprz;
+   struct persistent_ram_zone **mprzs;
phys_addr_t phys_addr;
unsigned long size;
unsigned int memtype;
size_t record_size;
size_t console_size;
size_t ftrace_size;
-   size_t pmsg_size;
+   size_t *pmsg_size;
int dump_oops;
struct persistent_ram_ecc_info ecc_info;
unsigned int max_dump_cnt;
@@ -103,6 +103,7 @@ struct ramoops_context {
unsigned int console_read_cnt;
unsigned int ftrace_read_cnt;
unsigned int pmsg_read_cnt;
+   unsigned int num_pmsg;
struct pstore_info pstore;
 };
 
@@ -220,9 +221,10 @@ static ssize_t ramoops_pstore_read(u64 *id, enum 
pstore_type_id *type,
if (!prz_ok(prz))
prz = ramoops_get_next_prz(>fprz, >ftrace_read_cnt,
   1, id, type, PSTORE_TYPE_FTRACE, 0);
-   if (!prz_ok(prz))
-   prz = ramoops_get_next_prz(>mprz, >pmsg_read_cnt,
-  1, id, type, PSTORE_TYPE_PMSG, 0);
+   while (cxt->pmsg_read_cnt < cxt->num_pmsg && !prz)
+   prz = ramoops_get_next_prz(cxt->mprzs, >pmsg_read_cnt,
+  cxt->num_pmsg, id, type,
+  PSTORE_TYPE_PMSG, 0);
if (!prz_ok(prz))
return 0;
 
@@ -286,9 +288,11 @@ static int notrace ramoops_pstore_write_buf(enum 
pstore_type_id type,
persistent_ram_write(cxt->fprz, buf, size);
return 0;
} else if (type == PSTORE_TYPE_PMSG) {
-   if (!cxt->mprz)
+   if (part >= cxt->num_pmsg)
+   return -EINVAL;
+   if (!cxt->mprzs || !cxt->mprzs[part])
return -ENOMEM;
-   persistent_ram_write(cxt->mprz, buf, size);
+   persistent_ram_write(cxt->mprzs[part], buf, size);
return 0;
}
 
@@ -348,7 +352,9 @@ static int ramoops_pstore_erase(enum pstore_type_id type, 
u64 id, int count,
prz = cxt->fprz;
break;
case PSTORE_TYPE_PMSG:
-   prz = cxt->mprz;
+   if (

[PATCH 2/5] ramoops: introduce generic init/free functions for prz

[Hiraku Toyooka]

We modifies initialization and freeing code for prz for generic usage.
This change

 * add generic function __ramoops_init_prz() to reduce redundancy
   between ramoops_init_prz() and ramoops_init_przs().
 * rename 'przs' member in struct ramoops_context to 'dprzs' so that
   it stands for 'dump przs'.
 * rename ramoops_init_prz() to ramoops_init_dprzs().
 * change parameter of ramoops_free_przs() from struct ramoops_context *
   into struct persistent_ram_zone * in order to make it available for
   all prz array.

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.aguchi...@hitachi.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: linux-kernel@vger.kernel.org
---
 fs/pstore/ram.c |   63 +++
 1 file changed, 35 insertions(+), 28 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 6363768..89cc90e 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -83,7 +83,7 @@ MODULE_PARM_DESC(ramoops_ecc,
"bytes ECC)");
 
 struct ramoops_context {
-   struct persistent_ram_zone **przs;
+   struct persistent_ram_zone **dprzs;
struct persistent_ram_zone *cprz;
struct persistent_ram_zone *fprz;
struct persistent_ram_zone *mprz;
@@ -199,7 +199,7 @@ static ssize_t ramoops_pstore_read(u64 *id, enum 
pstore_type_id *type,
 
/* Find the next valid persistent_ram_zone for DMESG */
while (cxt->dump_read_cnt < cxt->max_dump_cnt && !prz) {
-   prz = ramoops_get_next_prz(cxt->przs, >dump_read_cnt,
+   prz = ramoops_get_next_prz(cxt->dprzs, >dump_read_cnt,
   cxt->max_dump_cnt, id, type,
   PSTORE_TYPE_DMESG, 1);
if (!prz_ok(prz))
@@ -314,10 +314,10 @@ static int notrace ramoops_pstore_write_buf(enum 
pstore_type_id type,
if (part != 1)
return -ENOSPC;
 
-   if (!cxt->przs)
+   if (!cxt->dprzs)
return -ENOSPC;
 
-   prz = cxt->przs[cxt->dump_write_cnt];
+   prz = cxt->dprzs[cxt->dump_write_cnt];
 
hlen = ramoops_write_kmsg_hdr(prz, compressed);
if (size + hlen > prz->buffer_size)
@@ -339,7 +339,7 @@ static int ramoops_pstore_erase(enum pstore_type_id type, 
u64 id, int count,
case PSTORE_TYPE_DMESG:
if (id >= cxt->max_dump_cnt)
return -EINVAL;
-   prz = cxt->przs[id];
+   prz = cxt->dprzs[id];
break;
case PSTORE_TYPE_CONSOLE:
prz = cxt->cprz;
@@ -371,21 +371,24 @@ static struct ramoops_context oops_cxt = {
},
 };
 
-static void ramoops_free_przs(struct ramoops_context *cxt)
+static void ramoops_free_przs(struct persistent_ram_zone **przs)
 {
int i;
 
-   cxt->max_dump_cnt = 0;
-   if (!cxt->przs)
+   if (!przs)
return;
 
-   for (i = 0; !IS_ERR_OR_NULL(cxt->przs[i]); i++)
-   persistent_ram_free(cxt->przs[i]);
-   kfree(cxt->przs);
+   for (i = 0; i < !IS_ERR_OR_NULL(przs[i]); i++)
+   persistent_ram_free(przs[i]);
+   kfree(przs);
 }
 
-static int ramoops_init_przs(struct device *dev, struct ramoops_context *cxt,
-phys_addr_t *paddr, size_t dump_mem_sz)
+static int __ramoops_init_prz(struct device *dev, struct ramoops_context *cxt,
+ struct persistent_ram_zone **prz,
+ phys_addr_t *paddr, size_t sz, u32 sig, bool zap);
+
+static int ramoops_init_dprzs(struct device *dev, struct ramoops_context *cxt,
+ phys_addr_t *paddr, size_t dump_mem_sz)
 {
int err = -ENOMEM;
int i;
@@ -402,29 +405,24 @@ static int ramoops_init_przs(struct device *dev, struct 
ramoops_context *cxt,
if (!cxt->max_dump_cnt)
return -ENOMEM;
 
-   cxt->przs = kzalloc(sizeof(*cxt->przs) * cxt->max_dump_cnt,
+   cxt->dprzs = kcalloc(cxt->max_dump_cnt, sizeof(*cxt->dprzs),
 GFP_KERNEL);
-   if (!cxt->przs) {
+   if (!cxt->dprzs) {
dev_err(dev, "failed to initialize a prz array for dumps\n");
goto fail_prz;
}
 
for (i = 0; i < cxt->max_dump_cnt; i++) {
-   cxt->przs[i] = persistent_ram_new(*paddr, cxt->record_size, 0,
- >ecc_info,
- cxt->memtype);
-   if (IS_ERR(cxt->przs[i])) {
-   err = PTR_ERR(cxt->prz

[PATCH 0/5] pstore: ramoops: support multiple pmsg instances

[Hiraku Toyooka]

The following series implements multiple pmsg. This feature allows
userspace program to control individual content aging or priority.

If a pstore backend module(e.g. ramoops) requires the multiple pmsg
instances when registering itself to pstore, multiple /dev/pmsg[ID]
are created. Writes to each /dev/pmsg[ID] are isolated each other. After
reboot, the contents are available in /sys/fs/pstore/pmsg-[backend]-[ID].

In addition, we add multiple pmsg support for ramoops. We can
specify multiple pmsg area size by its module parameter as follows.

 pmsg_size=0x1000,0x2000,...

---

Hiraku Toyooka (5):
  ramoops: use persistent_ram_free() instead of kfree() for freeing prz
  ramoops: introduce generic init/free functions for prz
  pstore: support multiple pmsg instances
  ramoops: support multiple pmsg instances
  selftests/pstore: add testcases for multiple pmsg instances


 Documentation/ramoops.txt  |   22 ++
 fs/pstore/pmsg.c   |   20 ++
 fs/pstore/ram.c|  213 +++-
 include/linux/pstore.h |1 
 include/linux/pstore_ram.h |8 +
 tools/testing/selftests/pstore/common_tests|   21 ++
 .../selftests/pstore/pstore_post_reboot_tests  |   27 +--
 tools/testing/selftests/pstore/pstore_tests|   16 +-
 8 files changed, 257 insertions(+), 71 deletions(-)

--
Hiraku Toyooka
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[PATCH 1/5] ramoops: use persistent_ram_free() instead of kfree() for freeing prz

[Hiraku Toyooka]

persistent_ram_zone(=prz) structures are allocated by
persistent_ram_new(), which includes vmap() or ioremap(). But they
are currently freed by kfree(). We should use persistent_ram_free()
to correct this asymmetry usage.

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.aguchi...@hitachi.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: linux-kernel@vger.kernel.org
---
 fs/pstore/ram.c |6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 6c26c4d..6363768 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -567,11 +567,11 @@ fail_buf:
kfree(cxt->pstore.buf);
 fail_clear:
cxt->pstore.bufsize = 0;
-   kfree(cxt->mprz);
+   persistent_ram_free(cxt->mprz);
 fail_init_mprz:
-   kfree(cxt->fprz);
+   persistent_ram_free(cxt->fprz);
 fail_init_fprz:
-   kfree(cxt->cprz);
+   persistent_ram_free(cxt->cprz);
 fail_init_cprz:
ramoops_free_przs(cxt);
 fail_out:

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[PATCH 3/5] pstore: support multiple pmsg instances

[Hiraku Toyooka]

This patch enables pmsg to deal with multiple instances. One possible
use is content priority control on limited persistent store space. By
using different buffers, we can prevent important messages from being
overwritten by less important messages.

When a pstore backend module specifies the number of instances (num_pmsg)
in pstore_info, multiple /dev/pmsg[ID] appear. (ID is an integer
starting at 0. It corresponds to minor number of the each char device.)
Writes to each /dev/pmsg[ID] are isolated each other. After reboot, the
contents are available in /sys/fs/pstore/pmsg-[backend]-[ID].

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.aguchi...@hitachi.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: linux-kernel@vger.kernel.org
---
 fs/pstore/pmsg.c   |   20 ++--
 include/linux/pstore.h |1 +
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/fs/pstore/pmsg.c b/fs/pstore/pmsg.c
index feb5dd2..3467d63 100644
--- a/fs/pstore/pmsg.c
+++ b/fs/pstore/pmsg.c
@@ -50,8 +50,8 @@ static ssize_t write_pmsg(struct file *file, const char 
__user *buf,
vfree(buffer);
return -EFAULT;
}
-   psinfo->write_buf(PSTORE_TYPE_PMSG, 0, , 0, buffer, 0, c,
- psinfo);
+   psinfo->write_buf(PSTORE_TYPE_PMSG, 0, ,
+ iminor(file->f_inode), buffer, 0, c, psinfo);
 
i += c;
}
@@ -83,6 +83,7 @@ static char *pmsg_devnode(struct device *dev, umode_t *mode)
 void pstore_register_pmsg(void)
 {
struct device *pmsg_device;
+   int i = 0;
 
pmsg_major = register_chrdev(0, PMSG_NAME, _fops);
if (pmsg_major < 0) {
@@ -103,9 +104,24 @@ void pstore_register_pmsg(void)
pr_err("failed to create device\n");
goto err_device;
}
+
+   /* allocate additional /dev/pmsg[ID] */
+   for (i = 1; i < psinfo->num_pmsg; i++) {
+   struct device *pmsg_device;
+
+   pmsg_device = device_create(pmsg_class, NULL,
+   MKDEV(pmsg_major, i), NULL, "%s%d",
+   PMSG_NAME, i);
+   if (IS_ERR(pmsg_device)) {
+   pr_err("failed to create device\n");
+   goto err_device;
+   }
+   }
return;
 
 err_device:
+   for (i--; i >= 0; i--)
+   device_destroy(pmsg_class, MKDEV(pmsg_major, i));
class_destroy(pmsg_class);
 err_class:
unregister_chrdev(pmsg_major, PMSG_NAME);
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index 8e7a25b..7cffc9d 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -54,6 +54,7 @@ struct pstore_info {
size_t  bufsize;
struct mutexread_mutex; /* serialize open/read/close */
int flags;
+   unsigned intnum_pmsg;
int (*open)(struct pstore_info *psi);
int (*close)(struct pstore_info *psi);
ssize_t (*read)(u64 *id, enum pstore_type_id *type,

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[PATCH 4/5] ramoops: support multiple pmsg instances

[Hiraku Toyooka]

This patch enables ramoops to deal with multiple pmsg instances.
We can configure the size of each buffers by its module parameter
as follows.

  pmsg_size=0x1000,0x2000,...

Then, the ramoops allocates multiple buffers and tells the number
of buffers to pstore to create multiple /dev/pmsg[ID].

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Jonathan Corbet <cor...@lwn.net>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.aguchi...@hitachi.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: linux-...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 Documentation/ramoops.txt  |   22 +++
 fs/pstore/ram.c|  146 ++--
 include/linux/pstore_ram.h |8 ++
 3 files changed, 154 insertions(+), 22 deletions(-)

diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
index 5d86756..cff6ac7 100644
--- a/Documentation/ramoops.txt
+++ b/Documentation/ramoops.txt
@@ -126,3 +126,25 @@ file. Here is an example of usage:
  0 811d9c54  8101a7a0  __const_udelay <- 
native_machine_emergency_restart+0x110/0x1e0
  0 811d9c34  811d9c80  __delay <- __const_udelay+0x30/0x40
  0 811d9d14  811d9c3f  delay_tsc <- __delay+0xf/0x20
+
+6. Pmsg support
+
+Ramoops supports pmsg - logging userspace mesages in persistent store. By
+default, one pmsg area becomes available in ramoops. You can write data into
+/dev/pmsg0, e.g.:
+
+ # echo foo > /dev/pmsg0
+
+After reboot, the stored data can be read from pmsg-ramoops-0 on the pstore
+filesystem.
+
+You can specify size of the pmsg area by additional kernel command line, e.g.:
+
+ "ramoops.pmsg_size=0x1000"
+
+You can also use multiple pmsg areas, e.g.:
+
+ "ramoops.pmsg_size=0x1000,0x2000,..."
+
+Then, pmsg0, pmsg1, ... will appear on /dev. This is useful to control
+individual content aging or priority.
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 89cc90e..1d1378c 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -51,8 +51,8 @@ static ulong ramoops_ftrace_size = MIN_MEM_SIZE;
 module_param_named(ftrace_size, ramoops_ftrace_size, ulong, 0400);
 MODULE_PARM_DESC(ftrace_size, "size of ftrace log");
 
-static ulong ramoops_pmsg_size = MIN_MEM_SIZE;
-module_param_named(pmsg_size, ramoops_pmsg_size, ulong, 0400);
+static char *ramoops_pmsg_size_str;
+module_param_named(pmsg_size, ramoops_pmsg_size_str, charp, 0400);
 MODULE_PARM_DESC(pmsg_size, "size of user space message log");
 
 static ulong mem_address;
@@ -86,14 +86,14 @@ struct ramoops_context {
struct persistent_ram_zone **dprzs;
struct persistent_ram_zone *cprz;
struct persistent_ram_zone *fprz;
-   struct persistent_ram_zone *mprz;
+   struct persistent_ram_zone **mprzs;
phys_addr_t phys_addr;
unsigned long size;
unsigned int memtype;
size_t record_size;
size_t console_size;
size_t ftrace_size;
-   size_t pmsg_size;
+   size_t *pmsg_size;
int dump_oops;
struct persistent_ram_ecc_info ecc_info;
unsigned int max_dump_cnt;
@@ -103,6 +103,7 @@ struct ramoops_context {
unsigned int console_read_cnt;
unsigned int ftrace_read_cnt;
unsigned int pmsg_read_cnt;
+   unsigned int num_pmsg;
struct pstore_info pstore;
 };
 
@@ -220,9 +221,10 @@ static ssize_t ramoops_pstore_read(u64 *id, enum 
pstore_type_id *type,
if (!prz_ok(prz))
prz = ramoops_get_next_prz(>fprz, >ftrace_read_cnt,
   1, id, type, PSTORE_TYPE_FTRACE, 0);
-   if (!prz_ok(prz))
-   prz = ramoops_get_next_prz(>mprz, >pmsg_read_cnt,
-  1, id, type, PSTORE_TYPE_PMSG, 0);
+   while (cxt->pmsg_read_cnt < cxt->num_pmsg && !prz)
+   prz = ramoops_get_next_prz(cxt->mprzs, >pmsg_read_cnt,
+  cxt->num_pmsg, id, type,
+  PSTORE_TYPE_PMSG, 0);
if (!prz_ok(prz))
return 0;
 
@@ -286,9 +288,11 @@ static int notrace ramoops_pstore_write_buf(enum 
pstore_type_id type,
persistent_ram_write(cxt->fprz, buf, size);
return 0;
} else if (type == PSTORE_TYPE_PMSG) {
-   if (!cxt->mprz)
+   if (part >= cxt->num_pmsg)
+   return -EINVAL;
+   if (!cxt->mprzs || !cxt->mprzs[part])
return -ENOMEM;
-   persistent_ram_write(cxt->mprz, buf, size);
+   persistent_ram_write(cxt->mprzs[part], buf, size);
return 0;
}
 
@@ -348,7 +352,9 @@ s

[PATCH 5/5] selftests/pstore: add testcases for multiple pmsg instances

[Hiraku Toyooka]

To test multiple pmsg, we should check that /dev/pmsg[N] (N > 0) is
available. After reboot, we should check that pmsg-[backend]-[N] which
keeps content is detected even if pmsg-[backend]-[N-M] (0 < M <= N)
doesn't exist due to lack of contents.

So we add the following testcases.
 - pstore_tests
   - Write unique string to the last /dev/pmsgN
 - pstore_post_reboot_tests
   - Check the last pmsg area is detected

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.aguchi...@hitachi.com>
Cc: Shuah Khan <shua...@osg.samsung.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: linux-...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 tools/testing/selftests/pstore/common_tests|   21 ++--
 .../selftests/pstore/pstore_post_reboot_tests  |   27 +++-
 tools/testing/selftests/pstore/pstore_tests|   16 ++--
 3 files changed, 47 insertions(+), 17 deletions(-)

diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
index 3ea64d7..566a25d 100755
--- a/tools/testing/selftests/pstore/common_tests
+++ b/tools/testing/selftests/pstore/common_tests
@@ -27,9 +27,9 @@ show_result() { # result_value
 }
 
 check_files_exist() { # type of pstorefs file
-if [ -e ${1}-${backend}-0 ]; then
+if [ -e ${1}0 ]; then
prlog "ok"
-   for f in `ls ${1}-${backend}-*`; do
+   for f in `ls ${1}*`; do
 prlog -e "\t${f}"
done
 else
@@ -53,6 +53,23 @@ operate_files() { # tested value, files, operation
 fi
 }
 
+check_pmsg_content() { # pmsg filename
+prev_uuid=`cat $TOP_DIR/prev_uuid`
+if [ $? -eq 0 ]; then
+   nr_matched=`grep -c "$TEST_STRING_PATTERN" $1`
+   if [ "$nr_matched" = "1" ]; then
+   grep -q "$TEST_STRING_PATTERN"$prev_uuid $1
+   show_result $?
+   else
+   prlog "FAIL"
+   rc=1
+   fi
+else
+   prlog "FAIL"
+   rc=1
+fi
+}
+
 # Parameters
 TEST_STRING_PATTERN="Testing pstore: uuid="
 UUID=`cat /proc/sys/kernel/random/uuid`
diff --git a/tools/testing/selftests/pstore/pstore_post_reboot_tests 
b/tools/testing/selftests/pstore/pstore_post_reboot_tests
index 6ccb154..272498f 100755
--- a/tools/testing/selftests/pstore/pstore_post_reboot_tests
+++ b/tools/testing/selftests/pstore/pstore_post_reboot_tests
@@ -35,13 +35,13 @@ fi
 cd ${mount_point}
 
 prlog -n "Checking dmesg files exist in pstore filesystem ... "
-check_files_exist dmesg
+check_files_exist dmesg-${backend}-
 
 prlog -n "Checking console files exist in pstore filesystem ... "
-check_files_exist console
+check_files_exist console-${backend}-
 
 prlog -n "Checking pmsg files exist in pstore filesystem ... "
-check_files_exist pmsg
+check_files_exist pmsg-${backend}-
 
 prlog -n "Checking dmesg files contain oops end marker"
 grep_end_trace() {
@@ -54,16 +54,19 @@ prlog -n "Checking console file contains oops end marker 
... "
 grep -q "\---\[ end trace" console-${backend}-0
 show_result $?
 
-prlog -n "Checking pmsg file properly keeps the content written before crash 
... "
-prev_uuid=`cat $TOP_DIR/prev_uuid`
-if [ $? -eq 0 ]; then
-nr_matched=`grep -c "$TEST_STRING_PATTERN" pmsg-${backend}-0`
-if [ $nr_matched -eq 1 ]; then
-   grep -q "$TEST_STRING_PATTERN"$prev_uuid pmsg-${backend}-0
-   show_result $?
+prlog -n "Checking pmsg-"${backend}"-0 properly keeps the content written 
before crash ... "
+check_pmsg_content pmsg-${backend}-0
+
+prlog -n "Checking the last pmsg area is detected "
+last_num_pmsg=`ls -v pmsg-* | tail -n1 | sed -e 
"s/^pmsg-${backend}-\([0-9]*\).*$/\1/"`
+last_num_devpmsg=`ls -v /dev/pmsg* | tail -n1 | sed -e 
"s/^\/dev\/pmsg\([0-9]*\).*$/\1/"`
+#checks the last number of pmsg-*-* and /dev/pmsg* correspond.
+if [ "$last_num_pmsg" -eq "$last_num_devpmsg" ]; then
+if [ "$last_num_pmsg" = "0" ]; then
+   prlog "... No multiple pmsg-*-* exists. We skip this testcase."
 else
-   prlog "FAIL"
-   rc=1
+   prlog -n "(pmsg-${backend}-${last_num_pmsg}) ... "
+   check_pmsg_content pmsg-${backend}-${last_num_pmsg}
 fi
 else
 prlog "FAIL"
diff --git a/tools/testing/selftests/pstore/pstore_tests 
b/tools/testing/selftests/pstore/pstore_tests
index f25d2a3..5abf0e5 100755
--- a/tools/testing/selftests/pstore/pstore_tests
+++ b/tools/testing/selftests/pstore/pstore_tests
@@ -13,9 +13,8 @@ prlog -n "Checking pstore console is registered 

Re: [RFD] pstore: pmsg: ramoops: add multiple pmsg instances

[Hiraku Toyooka]

Hello Mark,

(I'm sorry for my late reply.)

Mark Salyzyn wrote:
>> I'm trying to make the feature of multiple pmsg instances for ramoops.
> I like it, in fact I encourage it.

Thank you.

> Multiple instances does allow one to control individual content aging or
> priority, I agree with your assessment, but make sure that you have a
> bona fide user for it (even if it is just for yourself)?

Yes. There are embedded devices which have limited NVRAM and no
HDD/SSD. Especially in our usage, the devices are industrial
machinery. When we catch a system failure, for fixing the root cause of
the failure, we often have to distinguish if it happend suddenly or if
there were signs long before the failure. Multiple pmsg can help this
kind of cause analysis with small NVRAM because higher priority
messages are preserved for a long time.

> NB: ToDo: device tree support for pstore configuration

Would you mean pstore backend's configuration (e.g.'mem_address' in
ramoops)?

Best regards,
Hiraku Toyooka

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Re: [RFD] pstore: pmsg: ramoops: add multiple pmsg instances

[Hiraku Toyooka]

Hello Mark,

(I'm sorry for my late reply.)

Mark Salyzyn wrote:
>> I'm trying to make the feature of multiple pmsg instances for ramoops.
> I like it, in fact I encourage it.

Thank you.

> Multiple instances does allow one to control individual content aging or
> priority, I agree with your assessment, but make sure that you have a
> bona fide user for it (even if it is just for yourself)?

Yes. There are embedded devices which have limited NVRAM and no
HDD/SSD. Especially in our usage, the devices are industrial
machinery. When we catch a system failure, for fixing the root cause of
the failure, we often have to distinguish if it happend suddenly or if
there were signs long before the failure. Multiple pmsg can help this
kind of cause analysis with small NVRAM because higher priority
messages are preserved for a long time.

> NB: ToDo: device tree support for pstore configuration

Would you mean pstore backend's configuration (e.g.'mem_address' in
ramoops)?

Best regards,
Hiraku Toyooka

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[RFD] pstore: pmsg: ramoops: add multiple pmsg instances

[Hiraku Toyooka]

Hello,

I'm trying to make the feature of multiple pmsg instances for ramoops.
I would like to discuss a possible way of getting the feature added to
mainline.

The reason to add the multiple pmsg is to preserve particular
messages over a long time, which are useful for failure analysis.

Currently, we can use /dev/pmsg0 to log userspace messages into pstore.
It is useful but we can use only one pstore buffer even if pstore
backend module (e.g. ramoops) can create multiple buffers. When one
messages happen to be generated repeatedly, old messages are
overwritten by them regardless of the importance of the messages.

Multiple pmsg will solves the problem. If we have two pmsg files:
/dev/pmsg{0,1}, we can write all messages into /dev/pmsg0, while
writing important ones into /dev/pmsg1. It can also be used for
preserving important kernel messages selected by an userspace daemon.

We have two types of files for pmsg. /dev/pmsg0 is for logging and
/sys/fs/pstore/pmsg-$backend-0 is for read. We can extend these files
like pmsg{0,1,2,...}, pmsg-$backend-{0,1,2,...}.

To realize this /dev/pmsgN interface, pstore backend modules which
manage multiple buffers for pmsg should tell the necessary numbers of
buffer to pstore_register_pmsg() via pstore_info. In addition, for
ramoops, I think the following works for ram.c are necessary at least.

* Parse multiple pmsg size in module parameter, for example,
  pmsg_size=0x2000,0x1000,...

* Change pmsg_size in ramoops_platform_data to a pointer of size
  array.

 struct ramoops_platform_data {
...
-   unsigned long   pmsg_size;
+   unsigned long   *pmsg_size;
...
 };

  When a ramoops's backend driver registers the platform_data and want
  pmsg buffers, it should allocate an array of size for pmsg_size.
  (Although there is no ramoops's backend which uses pmsg currently)

* Give an ID for each pmsg buffer, and modify some functions related to
  buffer allocation.

What do you think about this idea?

Best regards,
Hiraku Toyooka


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[RFD] pstore: pmsg: ramoops: add multiple pmsg instances

[Hiraku Toyooka]

Hello,

I'm trying to make the feature of multiple pmsg instances for ramoops.
I would like to discuss a possible way of getting the feature added to
mainline.

The reason to add the multiple pmsg is to preserve particular
messages over a long time, which are useful for failure analysis.

Currently, we can use /dev/pmsg0 to log userspace messages into pstore.
It is useful but we can use only one pstore buffer even if pstore
backend module (e.g. ramoops) can create multiple buffers. When one
messages happen to be generated repeatedly, old messages are
overwritten by them regardless of the importance of the messages.

Multiple pmsg will solves the problem. If we have two pmsg files:
/dev/pmsg{0,1}, we can write all messages into /dev/pmsg0, while
writing important ones into /dev/pmsg1. It can also be used for
preserving important kernel messages selected by an userspace daemon.

We have two types of files for pmsg. /dev/pmsg0 is for logging and
/sys/fs/pstore/pmsg-$backend-0 is for read. We can extend these files
like pmsg{0,1,2,...}, pmsg-$backend-{0,1,2,...}.

To realize this /dev/pmsgN interface, pstore backend modules which
manage multiple buffers for pmsg should tell the necessary numbers of
buffer to pstore_register_pmsg() via pstore_info. In addition, for
ramoops, I think the following works for ram.c are necessary at least.

* Parse multiple pmsg size in module parameter, for example,
  pmsg_size=0x2000,0x1000,...

* Change pmsg_size in ramoops_platform_data to a pointer of size
  array.

 struct ramoops_platform_data {
...
-   unsigned long   pmsg_size;
+   unsigned long   *pmsg_size;
...
 };

  When a ramoops's backend driver registers the platform_data and want
  pmsg buffers, it should allocate an array of size for pmsg_size.
  (Although there is no ramoops's backend which uses pmsg currently)

* Give an ID for each pmsg buffer, and modify some functions related to
  buffer allocation.

What do you think about this idea?

Best regards,
Hiraku Toyooka


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[PATCH v2 2/2] selftests/pstore: add pstore test scripts going with reboot

[Hiraku Toyooka]

To test pstore in earnest, we have to cause kernel crash and check
pstore filesystem after reboot.

We add two scripts:
 - pstore_crash_test
 This script causes kernel crash and reboot. It is executed by
 'make run_pstore_crash' in selftests. It can also be used with kdump.
 - pstore_post_reboot_tests
 This script includes test cases which check pstore's behavior after
 crash and reboot. It is executed together with pstore_tests by
 'make run_tests [-C pstore]' in selftests.

The test cases in pstore_post_reboot_tests are currently following.

- Check pstore backend is registered
- Mount pstore filesystem
- Check dmesg/console/pmsg files exist in pstore filesystem
- Check dmesg/console files contain oops end marker
- Check pmsg file properly keeps the content written before crash
- Remove all files in pstore filesystem

Example usage is following.

  (before reboot)
  # cd /path/to/selftests
  # make run_tests -C pstore
  === Pstore unit tests (pstore_tests) ===
  UUID=b49b02cf-b0c2-4309-be43-b08c3971e37f
  ...
  selftests: pstore_tests [PASS]
  === Pstore unit tests (pstore_post_reboot_tests) ===
  UUID=953eb1bc-8e03-48d7-b27a-6552b24c5b7e
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  pstore_crash_test has not been executed yet. we skip further tests.
  selftests: pstore_post_reboot_tests [PASS]

  # make run_pstore_crash
  === Pstore unit tests (pstore_crash_test) ===
  UUID=93c8972d-1466-430b-8c4a-28d8681e74c6
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  Causing kernel crash ...
  (kernel crash and reboot)
  ...

  (after reboot)
  # make run_tests -C pstore
  === Pstore unit tests (pstore_tests) ===
  UUID=8e511e77-2285-499f-8bc0-900d9af1fbcc
  ...
  selftests: pstore_tests [PASS]
  === Pstore unit tests (pstore_post_reboot_tests) ===
  UUID=2dcc2132-4f3c-45aa-a38f-3b54bff8cef1
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  Mounting pstore filesystem ... ok
  Checking dmesg files exist in pstore filesystem ... ok
  dmesg-ramoops-0
  dmesg-ramoops-1
  Checking console files exist in pstore filesystem ... ok
  console-ramoops-0
  Checking pmsg files exist in pstore filesystem ... ok
  pmsg-ramoops-0
  Checking dmesg files contain oops end marker
  dmesg-ramoops-0 ... ok
  dmesg-ramoops-1 ... ok
  Checking console file contains oops end marker ... ok
  Checking pmsg file properly keeps the content written before crash ... ok
  Removing all files in pstore filesystem
  console-ramoops-0 ... ok
  dmesg-ramoops-0 ... ok
  dmesg-ramoops-1 ... ok
  pmsg-ramoops-0 ... ok
  selftests: pstore_post_reboot_tests [PASS]

Signed-off-by: Hiraku Toyooka 
Cc: Shuah Khan 
Cc: Tony Luck 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
 tools/testing/selftests/Makefile   |3 +
 tools/testing/selftests/pstore/Makefile|7 +-
 tools/testing/selftests/pstore/common_tests|   28 +++
 tools/testing/selftests/pstore/pstore_crash_test   |   30 
 .../selftests/pstore/pstore_post_reboot_tests  |   77 
 5 files changed, 143 insertions(+), 2 deletions(-)
 create mode 100755 tools/testing/selftests/pstore/pstore_crash_test
 create mode 100755 tools/testing/selftests/pstore/pstore_post_reboot_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 1a8fb99..2458288 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -66,6 +66,9 @@ clean_hotplug:
make -C $$TARGET clean; \
done;
 
+run_pstore_crash:
+   make -C pstore run_crash
+
 INSTALL_PATH ?= install
 INSTALL_PATH := $(abspath $(INSTALL_PATH))
 ALL_SCRIPT := $(INSTALL_PATH)/run_kselftest.sh
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
index 48623f7..bd7abe2 100644
--- a/tools/testing/selftests/pstore/Makefile
+++ b/tools/testing/selftests/pstore/Makefile
@@ -3,10 +3,13 @@
 
 all:
 
-TEST_PROGS := pstore_tests
-TEST_FILES := common_tests
+TEST_PROGS := pstore_tests pstore_post_reboot_tests
+TEST_FILES := common_tests pstore_crash_test
 
 include ../lib.mk
 
+run_crash:
+   @sh pstore_crash_test || { echo "pstore_crash_test: [FAIL]"; exit 1; }
+
 clean:
rm -rf logs/* *uuid
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing

[PATCH v2 0/2] selftests/pstore: add pstore test script

[Hiraku Toyooka]

These scripts include test cases which check pstore behavior. This
is useful to avoid regressions of pstore.

Changes since v1:
 * Exit with 1 in pstore/Makefile when pstore_crash_test failed.
 * Create helper functions to make the tests much more readable.
 * Use /sys/module/pstore/parameters/backend to check pstore backend is
   registered.
 * Show content of /sys/module/.../backend and /proc/cmdline for debug
 * Give UUID to each execution of test script.
 * Write unique test string with UUID into pmsg.
 * Check only one test string pattern appears in pmsg after crash.
 * Check UUID written to pmsg matches across crash.
 * Don't touch panic_on_oops because it is not necessary for reboot on crash

(v1: http://www.kernelhub.org/?msg=831044=2)

I also confirmed that these scripts work fine with kdump reboot with
kernel boot parameter 'crash_kexec_post_notifiers'.

---

Hiraku Toyooka (2):
  selftests/pstore: add pstore test script for pre-reboot
  selftests/pstore: add pstore test scripts going with reboot


 tools/testing/selftests/Makefile   |4 +
 tools/testing/selftests/pstore/Makefile|   15 
 tools/testing/selftests/pstore/common_tests|   83 
 tools/testing/selftests/pstore/pstore_crash_test   |   30 +++
 .../selftests/pstore/pstore_post_reboot_tests  |   77 +++
 tools/testing/selftests/pstore/pstore_tests|   30 +++
 6 files changed, 239 insertions(+)
 create mode 100644 tools/testing/selftests/pstore/Makefile
 create mode 100755 tools/testing/selftests/pstore/common_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_crash_test
 create mode 100755 tools/testing/selftests/pstore/pstore_post_reboot_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_tests

--
Hiraku Toyooka
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[PATCH v2 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

The pstore_tests script includes test cases which check pstore's
behavior before crash (and reboot).

The test cases are currently following.

- Check pstore backend is registered
- Check pstore console is registered
- Check /dev/pmsg0 exists
- Write unique string to /dev/pmsg0

The unique string written to /dev/pmsg includes UUID. The UUID is also
left in 'uuid' file in order to enable us to check if the pmsg keeps the
string correctly after reboot.

Example usage is following.

  # cd /path/to/selftests
  # make run_tests -C pstore (or just .pstore/pstore_tests)
  make: Entering directory '/path/to/selftests/pstore'
  === Pstore unit tests (pstore_tests) ===
  UUID=b49b02cf-b0c2-4309-be43-b08c3971e37f
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  Checking pstore console is registered ... ok
  Checking /dev/pmsg0 exists ... ok
  Writing unique string to /dev/pmsg0 ... ok
  selftests: pstore_tests [PASS]
  make: Leaving directory '/path/to/selftests/pstore'

We can also see test logs later.

  # cat 
pstore/logs/20151001-072718_b49b02cf-b0c2-4309-be43-b08c3971e37f/pstore_tests.log
  Thu Oct  1 07:27:18 UTC 2015
  === Pstore unit tests (pstore_tests) ===
  UUID=b49b02cf-b0c2-4309-be43-b08c3971e37f
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  Checking pstore console is registered ... ok
  Checking /dev/pmsg0 exists ... ok
  Writing unique string to /dev/pmsg0 ... ok

Signed-off-by: Hiraku Toyooka 
Cc: Shuah Khan 
Cc: Tony Luck 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
 tools/testing/selftests/Makefile|1 
 tools/testing/selftests/pstore/Makefile |   12 ++
 tools/testing/selftests/pstore/common_tests |   55 +++
 tools/testing/selftests/pstore/pstore_tests |   30 +++
 4 files changed, 98 insertions(+)
 create mode 100644 tools/testing/selftests/pstore/Makefile
 create mode 100755 tools/testing/selftests/pstore/common_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index cfe1213..1a8fb99 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -13,6 +13,7 @@ TARGETS += mount
 TARGETS += mqueue
 TARGETS += net
 TARGETS += powerpc
+TARGETS += pstore
 TARGETS += ptrace
 TARGETS += seccomp
 TARGETS += size
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
new file mode 100644
index 000..48623f7
--- /dev/null
+++ b/tools/testing/selftests/pstore/Makefile
@@ -0,0 +1,12 @@
+# Makefile for pstore selftests.
+# Expects pstore backend is registered.
+
+all:
+
+TEST_PROGS := pstore_tests
+TEST_FILES := common_tests
+
+include ../lib.mk
+
+clean:
+   rm -rf logs/* *uuid
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
new file mode 100755
index 000..b1c3757
--- /dev/null
+++ b/tools/testing/selftests/pstore/common_tests
@@ -0,0 +1,55 @@
+#!/bin/sh
+
+# common_tests - Shell script commonly used by pstore test scripts
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka 
+#
+# Released under the terms of the GPL v2.
+
+# Utilities
+errexit() { # message
+echo "Error: $1" 1>&2
+exit 1
+}
+
+absdir() { # file_path
+(cd `dirname $1`; pwd)
+}
+
+show_result() { # result_value
+if [ $1 -eq 0 ]; then
+   prlog "ok"
+else
+   prlog "FAIL"
+   rc=1
+fi
+}
+
+# Parameters
+TEST_STRING_PATTERN="Testing pstore: uuid="
+UUID=`cat /proc/sys/kernel/random/uuid`
+TOP_DIR=`absdir $0`
+LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`_${UUID}/
+
+# Preparing logs
+LOG_FILE=$LOG_DIR/`basename $0`.log
+mkdir -p $LOG_DIR || errexit "Failed to make a log directory: $LOG_DIR"
+date > $LOG_FILE
+prlog() { # messages
+/bin/echo "$@" | tee -a $LOG_FILE
+}
+
+# Starting tests
+rc=0
+prlog "=== Pstore unit tests (`basename $0`) ==="
+prlog "UUID="$UUID
+
+prlog -n "Checking pstore backend is registered ... "
+backend=`cat /sys/module/pstore/parameters/backend`
+show_result $?
+prlog -e "\tbackend=${backend}"
+prlog -e "\tcmdline=`cat /proc/cmdline`"
+if [ $rc -ne 0 ]; then
+exit 1
+fi
diff --git a/tools/testing/selftests/pstore/pstore_tests 
b/tools/testing/selftests/pstore/pstore_tests
new file mode 100755
index 000..f25d2a3
--- /dev/null
+++ b/tools/testing/selftests/pstore/pstore_tests
@@ -0,0 +1,30 @@
+#!/bin/sh
+
+# pstore_

[PATCH v2 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

The pstore_tests script includes test cases which check pstore's
behavior before crash (and reboot).

The test cases are currently following.

- Check pstore backend is registered
- Check pstore console is registered
- Check /dev/pmsg0 exists
- Write unique string to /dev/pmsg0

The unique string written to /dev/pmsg includes UUID. The UUID is also
left in 'uuid' file in order to enable us to check if the pmsg keeps the
string correctly after reboot.

Example usage is following.

  # cd /path/to/selftests
  # make run_tests -C pstore (or just .pstore/pstore_tests)
  make: Entering directory '/path/to/selftests/pstore'
  === Pstore unit tests (pstore_tests) ===
  UUID=b49b02cf-b0c2-4309-be43-b08c3971e37f
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  Checking pstore console is registered ... ok
  Checking /dev/pmsg0 exists ... ok
  Writing unique string to /dev/pmsg0 ... ok
  selftests: pstore_tests [PASS]
  make: Leaving directory '/path/to/selftests/pstore'

We can also see test logs later.

  # cat 
pstore/logs/20151001-072718_b49b02cf-b0c2-4309-be43-b08c3971e37f/pstore_tests.log
  Thu Oct  1 07:27:18 UTC 2015
  === Pstore unit tests (pstore_tests) ===
  UUID=b49b02cf-b0c2-4309-be43-b08c3971e37f
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  Checking pstore console is registered ... ok
  Checking /dev/pmsg0 exists ... ok
  Writing unique string to /dev/pmsg0 ... ok

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Shuah Khan <shua...@osg.samsung.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.aguchi...@hitachi.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
 tools/testing/selftests/Makefile|1 
 tools/testing/selftests/pstore/Makefile |   12 ++
 tools/testing/selftests/pstore/common_tests |   55 +++
 tools/testing/selftests/pstore/pstore_tests |   30 +++
 4 files changed, 98 insertions(+)
 create mode 100644 tools/testing/selftests/pstore/Makefile
 create mode 100755 tools/testing/selftests/pstore/common_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index cfe1213..1a8fb99 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -13,6 +13,7 @@ TARGETS += mount
 TARGETS += mqueue
 TARGETS += net
 TARGETS += powerpc
+TARGETS += pstore
 TARGETS += ptrace
 TARGETS += seccomp
 TARGETS += size
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
new file mode 100644
index 000..48623f7
--- /dev/null
+++ b/tools/testing/selftests/pstore/Makefile
@@ -0,0 +1,12 @@
+# Makefile for pstore selftests.
+# Expects pstore backend is registered.
+
+all:
+
+TEST_PROGS := pstore_tests
+TEST_FILES := common_tests
+
+include ../lib.mk
+
+clean:
+   rm -rf logs/* *uuid
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
new file mode 100755
index 000..b1c3757
--- /dev/null
+++ b/tools/testing/selftests/pstore/common_tests
@@ -0,0 +1,55 @@
+#!/bin/sh
+
+# common_tests - Shell script commonly used by pstore test scripts
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
+#
+# Released under the terms of the GPL v2.
+
+# Utilities
+errexit() { # message
+echo "Error: $1" 1>&2
+exit 1
+}
+
+absdir() { # file_path
+(cd `dirname $1`; pwd)
+}
+
+show_result() { # result_value
+if [ $1 -eq 0 ]; then
+   prlog "ok"
+else
+   prlog "FAIL"
+   rc=1
+fi
+}
+
+# Parameters
+TEST_STRING_PATTERN="Testing pstore: uuid="
+UUID=`cat /proc/sys/kernel/random/uuid`
+TOP_DIR=`absdir $0`
+LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`_${UUID}/
+
+# Preparing logs
+LOG_FILE=$LOG_DIR/`basename $0`.log
+mkdir -p $LOG_DIR || errexit "Failed to make a log directory: $LOG_DIR"
+date > $LOG_FILE
+prlog() { # messages
+/bin/echo "$@" | tee -a $LOG_FILE
+}
+
+# Starting tests
+rc=0
+prlog "=== Pstore unit tests (`basename $0`) ==="
+prlog "UUID="$UUID
+
+prlog -n "Checking pstore backend is registered ... "
+backend=`cat /sys/module/pstore/parameters/backend`
+show_result $?
+prlog -e "\tbackend=${backend}"
+prlog -e "\tcmdline=`cat /proc/cmdline`"
+if [ $rc -ne 0 ]; the

[PATCH v2 2/2] selftests/pstore: add pstore test scripts going with reboot

[Hiraku Toyooka]

To test pstore in earnest, we have to cause kernel crash and check
pstore filesystem after reboot.

We add two scripts:
 - pstore_crash_test
 This script causes kernel crash and reboot. It is executed by
 'make run_pstore_crash' in selftests. It can also be used with kdump.
 - pstore_post_reboot_tests
 This script includes test cases which check pstore's behavior after
 crash and reboot. It is executed together with pstore_tests by
 'make run_tests [-C pstore]' in selftests.

The test cases in pstore_post_reboot_tests are currently following.

- Check pstore backend is registered
- Mount pstore filesystem
- Check dmesg/console/pmsg files exist in pstore filesystem
- Check dmesg/console files contain oops end marker
- Check pmsg file properly keeps the content written before crash
- Remove all files in pstore filesystem

Example usage is following.

  (before reboot)
  # cd /path/to/selftests
  # make run_tests -C pstore
  === Pstore unit tests (pstore_tests) ===
  UUID=b49b02cf-b0c2-4309-be43-b08c3971e37f
  ...
  selftests: pstore_tests [PASS]
  === Pstore unit tests (pstore_post_reboot_tests) ===
  UUID=953eb1bc-8e03-48d7-b27a-6552b24c5b7e
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  pstore_crash_test has not been executed yet. we skip further tests.
  selftests: pstore_post_reboot_tests [PASS]

  # make run_pstore_crash
  === Pstore unit tests (pstore_crash_test) ===
  UUID=93c8972d-1466-430b-8c4a-28d8681e74c6
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  Causing kernel crash ...
  (kernel crash and reboot)
  ...

  (after reboot)
  # make run_tests -C pstore
  === Pstore unit tests (pstore_tests) ===
  UUID=8e511e77-2285-499f-8bc0-900d9af1fbcc
  ...
  selftests: pstore_tests [PASS]
  === Pstore unit tests (pstore_post_reboot_tests) ===
  UUID=2dcc2132-4f3c-45aa-a38f-3b54bff8cef1
  Checking pstore backend is registered ... ok
  backend=ramoops
  cmdline=console=ttyS0,115200 root=/dev/mmcblk0p2 rw rootwait mem=768M 
ramoops.mem_address=0x3000 ramoops.mem_size=0x1
  Mounting pstore filesystem ... ok
  Checking dmesg files exist in pstore filesystem ... ok
  dmesg-ramoops-0
  dmesg-ramoops-1
  Checking console files exist in pstore filesystem ... ok
  console-ramoops-0
  Checking pmsg files exist in pstore filesystem ... ok
  pmsg-ramoops-0
  Checking dmesg files contain oops end marker
  dmesg-ramoops-0 ... ok
  dmesg-ramoops-1 ... ok
  Checking console file contains oops end marker ... ok
  Checking pmsg file properly keeps the content written before crash ... ok
  Removing all files in pstore filesystem
  console-ramoops-0 ... ok
  dmesg-ramoops-0 ... ok
  dmesg-ramoops-1 ... ok
  pmsg-ramoops-0 ... ok
  selftests: pstore_post_reboot_tests [PASS]

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Shuah Khan <shua...@osg.samsung.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.aguchi...@hitachi.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
 tools/testing/selftests/Makefile   |3 +
 tools/testing/selftests/pstore/Makefile|7 +-
 tools/testing/selftests/pstore/common_tests|   28 +++
 tools/testing/selftests/pstore/pstore_crash_test   |   30 
 .../selftests/pstore/pstore_post_reboot_tests  |   77 
 5 files changed, 143 insertions(+), 2 deletions(-)
 create mode 100755 tools/testing/selftests/pstore/pstore_crash_test
 create mode 100755 tools/testing/selftests/pstore/pstore_post_reboot_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 1a8fb99..2458288 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -66,6 +66,9 @@ clean_hotplug:
make -C $$TARGET clean; \
done;
 
+run_pstore_crash:
+   make -C pstore run_crash
+
 INSTALL_PATH ?= install
 INSTALL_PATH := $(abspath $(INSTALL_PATH))
 ALL_SCRIPT := $(INSTALL_PATH)/run_kselftest.sh
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
index 48623f7..bd7abe2 100644
--- a/tools/testing/selftests/pstore/Makefile
+++ b/tools/testing/selftests/pstore/Makefile
@@ -3,10 +3,13 @@
 
 all:
 
-TEST_PROGS := pstore_tests
-TEST_FILES := common_tests
+TEST_PROGS := pstore_tests pstore_post_reboot_tests
+TEST_FILES := common_tests pstore_crash_tes

[PATCH v2 0/2] selftests/pstore: add pstore test script

[Hiraku Toyooka]

These scripts include test cases which check pstore behavior. This
is useful to avoid regressions of pstore.

Changes since v1:
 * Exit with 1 in pstore/Makefile when pstore_crash_test failed.
 * Create helper functions to make the tests much more readable.
 * Use /sys/module/pstore/parameters/backend to check pstore backend is
   registered.
 * Show content of /sys/module/.../backend and /proc/cmdline for debug
 * Give UUID to each execution of test script.
 * Write unique test string with UUID into pmsg.
 * Check only one test string pattern appears in pmsg after crash.
 * Check UUID written to pmsg matches across crash.
 * Don't touch panic_on_oops because it is not necessary for reboot on crash

(v1: http://www.kernelhub.org/?msg=831044=2)

I also confirmed that these scripts work fine with kdump reboot with
kernel boot parameter 'crash_kexec_post_notifiers'.

---

Hiraku Toyooka (2):
  selftests/pstore: add pstore test script for pre-reboot
  selftests/pstore: add pstore test scripts going with reboot


 tools/testing/selftests/Makefile   |4 +
 tools/testing/selftests/pstore/Makefile|   15 
 tools/testing/selftests/pstore/common_tests|   83 
 tools/testing/selftests/pstore/pstore_crash_test   |   30 +++
 .../selftests/pstore/pstore_post_reboot_tests  |   77 +++
 tools/testing/selftests/pstore/pstore_tests|   30 +++
 6 files changed, 239 insertions(+)
 create mode 100644 tools/testing/selftests/pstore/Makefile
 create mode 100755 tools/testing/selftests/pstore/common_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_crash_test
 create mode 100755 tools/testing/selftests/pstore/pstore_post_reboot_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_tests

--
Hiraku Toyooka
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Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

Hello,

I'm sorry for my late reply.

Mark Salyzyn wrote:

Perfectly match is an issue, since something else might be using pmsg.
For instance, one of the applications that uses this interface
packetizes the messages so they can be picked out from other sources
that do not comply with the header (count, magic number etc). In this
case, should that daemon be active, your content would be ignores, but
your content would also be buried, but can be needled out with grep.

What you should do is grep for your string pattern within some
acceptable regex, and one should be found and no other, and it should
match perfectly. This would prevent another daemon's content from
disrupting your test and causing a false negative.


OK. I think that the following method suit your intention.
By splitting unique test string into TEST_STRING_PATTERN part and UUID
part, we can check both the non-existence of previous content and the
unique match on reboot-comparison run.
I'll include this in v2.

# before crash
TEST_STRING_PATTERN="Testing pstore: uuid="
UUID=`cat /proc/sys/kernel/random/uuid`
echo "$TEST_STRING_PATTERN""$UUID" > /dev/pmsg0
echo "$UUID" > uuid

# after crash
prlog -n "Checking pmsg file properly keeps the content written before 
crash ... "

nr_matched=`grep -c "$TEST_STRING_PATTERN" pmsg-${backend}-0`
if [ $nr_matched -eq 1 ]; then
grep -q "$TEST_STRING_PATTERN"`cat uuid` pmsg-${backend}-0
if [ $? -eq 0 ]; then
prlog "ok"
else
prlog "FAIL"
else
prlog "FAIL"
fi


Best regards,
Hiraku Toyooka

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Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

Hello,

I'm sorry for my late reply.

Mark Salyzyn wrote:

Perfectly match is an issue, since something else might be using pmsg.
For instance, one of the applications that uses this interface
packetizes the messages so they can be picked out from other sources
that do not comply with the header (count, magic number etc). In this
case, should that daemon be active, your content would be ignores, but
your content would also be buried, but can be needled out with grep.

What you should do is grep for your string pattern within some
acceptable regex, and one should be found and no other, and it should
match perfectly. This would prevent another daemon's content from
disrupting your test and causing a false negative.


OK. I think that the following method suit your intention.
By splitting unique test string into TEST_STRING_PATTERN part and UUID
part, we can check both the non-existence of previous content and the
unique match on reboot-comparison run.
I'll include this in v2.

# before crash
TEST_STRING_PATTERN="Testing pstore: uuid="
UUID=`cat /proc/sys/kernel/random/uuid`
echo "$TEST_STRING_PATTERN""$UUID" > /dev/pmsg0
echo "$UUID" > uuid

# after crash
prlog -n "Checking pmsg file properly keeps the content written before 
crash ... "

nr_matched=`grep -c "$TEST_STRING_PATTERN" pmsg-${backend}-0`
if [ $nr_matched -eq 1 ]; then
grep -q "$TEST_STRING_PATTERN"`cat uuid` pmsg-${backend}-0
if [ $? -eq 0 ]; then
prlog "ok"
else
prlog "FAIL"
else
prlog "FAIL"
fi


Best regards,
Hiraku Toyooka

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Re: [PATCH 2/2] selftests/pstore: add pstore test scripts going with reboot

[Hiraku Toyooka]

Hello,

>> +prlog "Causing kernel crash ..."
>> +
>> +# enable all functions triggered by sysrq
>> +echo 1 > /proc/sys/kernel/sysrq
>> +# setting to reboot in 3 seconds after panic
>> +echo 3 > /proc/sys/kernel/panic
>> +# setting to cause panic when oops occurs
>> +echo 1 > /proc/sys/kernel/panic_on_oops
>> +
>> +# create a file as reboot flag
>> +touch $REBOOT_FILE
>> +sync
>> +
>> +# cause crash
>> +echo c > /proc/sysrq-trigger
>
> Do you need to stop kdump service before the sysrq?

Yes, I should check /sys/kernel/kexec_crash_loaded. If the value is
1, this script should try to unload kexec kernel.

> Or, does it cover oops and kdump case?

No, not yet. I think we should support oops case at first.

Best regards,
Hiraku Toyooka

阿口誠司 / AGUCHI，SEIJI wrote:



+prlog "Causing kernel crash ..."
+
+# enable all functions triggered by sysrq
+echo 1 > /proc/sys/kernel/sysrq
+# setting to reboot in 3 seconds after panic
+echo 3 > /proc/sys/kernel/panic
+# setting to cause panic when oops occurs
+echo 1 > /proc/sys/kernel/panic_on_oops
+
+# create a file as reboot flag
+touch $REBOOT_FILE
+sync
+
+# cause crash
+echo c > /proc/sysrq-trigger


Do you need to stop kdump service before the sysrq?
Or, does it cover oops and kdump case?

Seiji


-Original Message-
From: 豊岡拓 / Toyooka，Hiraku
Sent: Tuesday, September 15, 2015 11:42 AM
To: Kees Cook
Cc: LKML; Tony Luck; Linux API; Anton Vorontsov; Shuah Khan; Mark Salyzyn; 
Colin Cross; 阿口誠司 / AGUCHI，SEIJI
Subject: Re: [PATCH 2/2] selftests/pstore: add pstore test scripts going with 
reboot

Hello Kees,

  >> +run_crash:
  >> +   @sh pstore_crash_test || echo "pstore_crash_test: [FAIL]"
  >
  > This is probably better written to exit 1 on failure, otherwise it
  > just _says_ it fails. (Though lots of selftests in the tree already
  > have this problem, it's best to avoid the pattern for new stuff.)
  > Maybe something like:
  >
  >  @sh pstore_crash_test || { echo "pstore_crash_test: [FAIL]";
exit 1; }

OK. I'll add the "exit 1".

  >> +prlog -n "Checking dmesg files exist in pstore filesystem ... "
  >> +if [ -e dmesg-${backend}-0 ]; then
  >> +prlog "ok"
  >> +for f in `ls dmesg-${backend}-*`; do
  >> +   prlog -e "\t${f}"
  >> +done
  >> +else
  >> +prlog "FAIL"
  >> +rc=1
  >> +fi
  >
  > This test pattern is repeated a lot. Maybe better to create a helper
  > function instead? It could make the tests much more readable.

Yes, I should make a helper function in v2.

Best regards,
Hiraku Toyooka


--
Hiraku Toyooka
Systems Productivity Research Dept. / Linux Technology Center
Center for Technology Innovation - Systems Engineering, Hitachi Ltd.
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Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

Hello,

> It may be good if you can log  "/sys/module/pstore/parameters/backend/"
> or /proc/cmdline in failure case.
>
> It makes debug easy.

OK, I'll have the script log the information in v2.

Best regards,
Hiraku Toyooka

阿口誠司 / AGUCHI，SEIJI wrote:

Hi,


+prlog -n "Checking pstore backend is registered ... "
+be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as persistent store 
backend$"`
+if [ $? -eq 0 ]; then
+backend=`echo ${be_msg} | sed -e 's/^.*Registered\ \([a-zA-z0-9-]\+\)\ 
as.*$/\1/g'`
+prlog "ok"
+else
+prlog "FAIL"
+exit 1


It may be good if you can log  "/sys/module/pstore/parameters/backend/"
or /proc/cmdline in failure case.

It makes debug easy.

Seiji


+fi




-Original Message-
From: 豊岡拓 / Toyooka，Hiraku
Sent: Tuesday, September 15, 2015 11:31 AM
To: Kees Cook
Cc: LKML; Tony Luck; Linux API; Anton Vorontsov; Shuah Khan; Mark Salyzyn; 
Colin Cross; 阿口誠司 / AGUCHI，SEIJI
Subject: Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

Hello, Kees,

Thank you for your advise.

  >> +be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as
persistent store backend$"`
...
  > This seems unstable if the system hasn't booted recently or if stuff
  > is spamming dmesg. What about examining /sys/module/pstore instead?

OK, I'll update in that way.

Best regards,
Hiraku Toyooka

Kees Cook wrote:

On Tue, Sep 8, 2015 at 4:06 AM, Hiraku Toyooka
 wrote:

The pstore_tests script includes test cases which check pstore's
behavior before crash (and reboot).

The test cases are currently following.

- Check pstore backend is registered
- Check pstore console is registered
- Check /dev/pmsg0 exists
- Write string to /dev/pmsg0

Example usage is following.

make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
pstore_crash_test has not been executed yet. we skip further tests.
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'

We can also see test logs later.

Signed-off-by: Hiraku Toyooka 
Cc: Shuah Khan 
Cc: Tony Luck 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
   tools/testing/selftests/Makefile|1 +
   tools/testing/selftests/pstore/Makefile |   12 +++
   tools/testing/selftests/pstore/common_tests |   45 
+++
   tools/testing/selftests/pstore/pstore_tests |   42 +
   4 files changed, 100 insertions(+)
   create mode 100644 tools/testing/selftests/pstore/Makefile
   create mode 100755 tools/testing/selftests/pstore/common_tests
   create mode 100755 tools/testing/selftests/pstore/pstore_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 24ae9e8..b58c72e 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -12,6 +12,7 @@ TARGETS += mount
   TARGETS += mqueue
   TARGETS += net
   TARGETS += powerpc
+TARGETS += pstore
   TARGETS += ptrace
   TARGETS += seccomp
   TARGETS += size
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
new file mode 100644
index 000..40b887d
--- /dev/null
+++ b/tools/testing/selftests/pstore/Makefile
@@ -0,0 +1,12 @@
+# Makefile for pstore selftests.
+# Expects pstore backend is registered.
+
+all:
+
+TEST_PROGS := pstore_tests
+TEST_FILES := common_tests
+
+include ../lib.mk
+
+clean:
+   rm -rf logs/*
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
new file mode 100755
index 000..98611c5
--- /dev/null
+++ b/tools/testing/selftests/pstore/common_tests
@@ -0,0 +1,45 @@
+#!/bin/sh
+
+# common_tests - Shell script commonly used by pstore test scripts
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka 
+#
+# Released under the terms of the GPL v2.
+
+# Utilities
+errexit() { # message
+  echo "Error: $1" 1>&2
+  exit 1
+}
+
+absdir() { # file_path
+  (cd `dirname $1`; pwd)
+}
+
+# Parameters
+TOP_DIR=`absdir $0`
+LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`/
+TEST_STRING="Testing pstore"
+
+# Preparing logs
+LOG_FILE=$LOG_DIR/`basename $0`.log
+mkdir -p $LOG_DIR || errexit "Failed to make a log directory: $LOG_DIR"
+date > $LOG_FILE
+prlog() { # messages
+  /bin/echo "$@" | tee -a $LOG_FILE
+}
+prlog "=== Pstore unit tests (`basename $0`)==="
+
+# Starting tests
+rc=0
+
+prlog -n "Checking pstore backend is regist

Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

Hello,

> It may be good if you can log  "/sys/module/pstore/parameters/backend/"
> or /proc/cmdline in failure case.
>
> It makes debug easy.

OK, I'll have the script log the information in v2.

Best regards,
Hiraku Toyooka

阿口誠司 / AGUCHI，SEIJI wrote:

Hi,


+prlog -n "Checking pstore backend is registered ... "
+be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as persistent store 
backend$"`
+if [ $? -eq 0 ]; then
+backend=`echo ${be_msg} | sed -e 's/^.*Registered\ \([a-zA-z0-9-]\+\)\ 
as.*$/\1/g'`
+prlog "ok"
+else
+prlog "FAIL"
+exit 1


It may be good if you can log  "/sys/module/pstore/parameters/backend/"
or /proc/cmdline in failure case.

It makes debug easy.

Seiji


+fi




-Original Message-
From: 豊岡拓 / Toyooka，Hiraku
Sent: Tuesday, September 15, 2015 11:31 AM
To: Kees Cook
Cc: LKML; Tony Luck; Linux API; Anton Vorontsov; Shuah Khan; Mark Salyzyn; 
Colin Cross; 阿口誠司 / AGUCHI，SEIJI
Subject: Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

Hello, Kees,

Thank you for your advise.

  >> +be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as
persistent store backend$"`
...
  > This seems unstable if the system hasn't booted recently or if stuff
  > is spamming dmesg. What about examining /sys/module/pstore instead?

OK, I'll update in that way.

Best regards,
Hiraku Toyooka

Kees Cook wrote:

On Tue, Sep 8, 2015 at 4:06 AM, Hiraku Toyooka
<hiraku.toyooka...@hitachi.com> wrote:

The pstore_tests script includes test cases which check pstore's
behavior before crash (and reboot).

The test cases are currently following.

- Check pstore backend is registered
- Check pstore console is registered
- Check /dev/pmsg0 exists
- Write string to /dev/pmsg0

Example usage is following.

make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
pstore_crash_test has not been executed yet. we skip further tests.
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'

We can also see test logs later.

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Shuah Khan <shua...@osg.samsung.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.agu...@hds.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
   tools/testing/selftests/Makefile|1 +
   tools/testing/selftests/pstore/Makefile |   12 +++
   tools/testing/selftests/pstore/common_tests |   45 
+++
   tools/testing/selftests/pstore/pstore_tests |   42 +
   4 files changed, 100 insertions(+)
   create mode 100644 tools/testing/selftests/pstore/Makefile
   create mode 100755 tools/testing/selftests/pstore/common_tests
   create mode 100755 tools/testing/selftests/pstore/pstore_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 24ae9e8..b58c72e 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -12,6 +12,7 @@ TARGETS += mount
   TARGETS += mqueue
   TARGETS += net
   TARGETS += powerpc
+TARGETS += pstore
   TARGETS += ptrace
   TARGETS += seccomp
   TARGETS += size
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
new file mode 100644
index 000..40b887d
--- /dev/null
+++ b/tools/testing/selftests/pstore/Makefile
@@ -0,0 +1,12 @@
+# Makefile for pstore selftests.
+# Expects pstore backend is registered.
+
+all:
+
+TEST_PROGS := pstore_tests
+TEST_FILES := common_tests
+
+include ../lib.mk
+
+clean:
+   rm -rf logs/*
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
new file mode 100755
index 000..98611c5
--- /dev/null
+++ b/tools/testing/selftests/pstore/common_tests
@@ -0,0 +1,45 @@
+#!/bin/sh
+
+# common_tests - Shell script commonly used by pstore test scripts
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
+#
+# Released under the terms of the GPL v2.
+
+# Utilities
+errexit() { # message
+  echo "Error: $1" 1>&2
+  exit 1
+}
+
+absdir() { # file_path
+  (cd `dirname $1`; pwd)
+}
+
+# Parameters
+TOP_DIR=`absdir $0`
+LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`/
+TEST_STRING="Testing pstore"
+
+# Preparing logs
+LOG_FILE=$LOG_DIR/`basename $0`.log
+

Re: [PATCH 2/2] selftests/pstore: add pstore test scripts going with reboot

[Hiraku Toyooka]

Hello,

>> +prlog "Causing kernel crash ..."
>> +
>> +# enable all functions triggered by sysrq
>> +echo 1 > /proc/sys/kernel/sysrq
>> +# setting to reboot in 3 seconds after panic
>> +echo 3 > /proc/sys/kernel/panic
>> +# setting to cause panic when oops occurs
>> +echo 1 > /proc/sys/kernel/panic_on_oops
>> +
>> +# create a file as reboot flag
>> +touch $REBOOT_FILE
>> +sync
>> +
>> +# cause crash
>> +echo c > /proc/sysrq-trigger
>
> Do you need to stop kdump service before the sysrq?

Yes, I should check /sys/kernel/kexec_crash_loaded. If the value is
1, this script should try to unload kexec kernel.

> Or, does it cover oops and kdump case?

No, not yet. I think we should support oops case at first.

Best regards,
Hiraku Toyooka

阿口誠司 / AGUCHI，SEIJI wrote:



+prlog "Causing kernel crash ..."
+
+# enable all functions triggered by sysrq
+echo 1 > /proc/sys/kernel/sysrq
+# setting to reboot in 3 seconds after panic
+echo 3 > /proc/sys/kernel/panic
+# setting to cause panic when oops occurs
+echo 1 > /proc/sys/kernel/panic_on_oops
+
+# create a file as reboot flag
+touch $REBOOT_FILE
+sync
+
+# cause crash
+echo c > /proc/sysrq-trigger


Do you need to stop kdump service before the sysrq?
Or, does it cover oops and kdump case?

Seiji


-Original Message-
From: 豊岡拓 / Toyooka，Hiraku
Sent: Tuesday, September 15, 2015 11:42 AM
To: Kees Cook
Cc: LKML; Tony Luck; Linux API; Anton Vorontsov; Shuah Khan; Mark Salyzyn; 
Colin Cross; 阿口誠司 / AGUCHI，SEIJI
Subject: Re: [PATCH 2/2] selftests/pstore: add pstore test scripts going with 
reboot

Hello Kees,

  >> +run_crash:
  >> +   @sh pstore_crash_test || echo "pstore_crash_test: [FAIL]"
  >
  > This is probably better written to exit 1 on failure, otherwise it
  > just _says_ it fails. (Though lots of selftests in the tree already
  > have this problem, it's best to avoid the pattern for new stuff.)
  > Maybe something like:
  >
  >  @sh pstore_crash_test || { echo "pstore_crash_test: [FAIL]";
exit 1; }

OK. I'll add the "exit 1".

  >> +prlog -n "Checking dmesg files exist in pstore filesystem ... "
  >> +if [ -e dmesg-${backend}-0 ]; then
  >> +prlog "ok"
  >> +for f in `ls dmesg-${backend}-*`; do
  >> +   prlog -e "\t${f}"
  >> +done
  >> +else
  >> +prlog "FAIL"
  >> +rc=1
  >> +fi
  >
  > This test pattern is repeated a lot. Maybe better to create a helper
  > function instead? It could make the tests much more readable.

Yes, I should make a helper function in v2.

Best regards,
Hiraku Toyooka


--
Hiraku Toyooka
Systems Productivity Research Dept. / Linux Technology Center
Center for Technology Innovation - Systems Engineering, Hitachi Ltd.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH 2/2] selftests/pstore: add pstore test scripts going with reboot

[Hiraku Toyooka]

Hello Kees,

>> +run_crash:
>> +   @sh pstore_crash_test || echo "pstore_crash_test: [FAIL]"
>
> This is probably better written to exit 1 on failure, otherwise it
> just _says_ it fails. (Though lots of selftests in the tree already
> have this problem, it's best to avoid the pattern for new stuff.)
> Maybe something like:
>
>  @sh pstore_crash_test || { echo "pstore_crash_test: [FAIL]"; 
exit 1; }


OK. I'll add the "exit 1".

>> +prlog -n "Checking dmesg files exist in pstore filesystem ... "
>> +if [ -e dmesg-${backend}-0 ]; then
>> +prlog "ok"
>> +for f in `ls dmesg-${backend}-*`; do
>> +   prlog -e "\t${f}"
>> +done
>> +else
>> +prlog "FAIL"
>> +rc=1
>> +fi
>
> This test pattern is repeated a lot. Maybe better to create a helper
> function instead? It could make the tests much more readable.

Yes, I should make a helper function in v2.

Best regards,
Hiraku Toyooka
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

Hello, Kees,

Thank you for your advise.

>> +be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as 
persistent store backend$"`

...
> This seems unstable if the system hasn't booted recently or if stuff
> is spamming dmesg. What about examining /sys/module/pstore instead?

OK, I'll update in that way.

Best regards,
Hiraku Toyooka

Kees Cook wrote:

On Tue, Sep 8, 2015 at 4:06 AM, Hiraku Toyooka
 wrote:

The pstore_tests script includes test cases which check pstore's
behavior before crash (and reboot).

The test cases are currently following.

- Check pstore backend is registered
- Check pstore console is registered
- Check /dev/pmsg0 exists
- Write string to /dev/pmsg0

Example usage is following.

make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
pstore_crash_test has not been executed yet. we skip further tests.
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'

We can also see test logs later.

Signed-off-by: Hiraku Toyooka 
Cc: Shuah Khan 
Cc: Tony Luck 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
  tools/testing/selftests/Makefile|1 +
  tools/testing/selftests/pstore/Makefile |   12 +++
  tools/testing/selftests/pstore/common_tests |   45 +++
  tools/testing/selftests/pstore/pstore_tests |   42 +
  4 files changed, 100 insertions(+)
  create mode 100644 tools/testing/selftests/pstore/Makefile
  create mode 100755 tools/testing/selftests/pstore/common_tests
  create mode 100755 tools/testing/selftests/pstore/pstore_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 24ae9e8..b58c72e 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -12,6 +12,7 @@ TARGETS += mount
  TARGETS += mqueue
  TARGETS += net
  TARGETS += powerpc
+TARGETS += pstore
  TARGETS += ptrace
  TARGETS += seccomp
  TARGETS += size
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
new file mode 100644
index 000..40b887d
--- /dev/null
+++ b/tools/testing/selftests/pstore/Makefile
@@ -0,0 +1,12 @@
+# Makefile for pstore selftests.
+# Expects pstore backend is registered.
+
+all:
+
+TEST_PROGS := pstore_tests
+TEST_FILES := common_tests
+
+include ../lib.mk
+
+clean:
+   rm -rf logs/*
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
new file mode 100755
index 000..98611c5
--- /dev/null
+++ b/tools/testing/selftests/pstore/common_tests
@@ -0,0 +1,45 @@
+#!/bin/sh
+
+# common_tests - Shell script commonly used by pstore test scripts
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka 
+#
+# Released under the terms of the GPL v2.
+
+# Utilities
+errexit() { # message
+  echo "Error: $1" 1>&2
+  exit 1
+}
+
+absdir() { # file_path
+  (cd `dirname $1`; pwd)
+}
+
+# Parameters
+TOP_DIR=`absdir $0`
+LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`/
+TEST_STRING="Testing pstore"
+
+# Preparing logs
+LOG_FILE=$LOG_DIR/`basename $0`.log
+mkdir -p $LOG_DIR || errexit "Failed to make a log directory: $LOG_DIR"
+date > $LOG_FILE
+prlog() { # messages
+  /bin/echo "$@" | tee -a $LOG_FILE
+}
+prlog "=== Pstore unit tests (`basename $0`)==="
+
+# Starting tests
+rc=0
+
+prlog -n "Checking pstore backend is registered ... "
+be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as persistent store 
backend$"`
+if [ $? -eq 0 ]; then
+backend=`echo ${be_msg} | sed -e 's/^.*Registered\ \([a-zA-z0-9-]\+\)\ 
as.*$/\1/g'`
+prlog "ok"
+else
+prlog "FAIL"
+exit 1
+fi


This seems unstable if the system hasn't booted recently or if stuff
is spamming dmesg. What about examining /sys/module/pstore instead?


diff --git a/tools/testing/selftests/pstore/pstore_tests 
b/tools/testing/selftests/pstore/pstore_tests
new file mode 100755
index 000..cbf613c
--- /dev/null
+++ b/tools/testing/selftests/pstore/pstore_tests
@@ -0,0 +1,42 @@
+#!/bin/sh
+
+# pstore_tests - Check pstore's behavior before crash/reboot
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka 
+#
+# Released under the terms of the GPL v2.
+
+. ./common_tests
+
+prlog -n "Checking pstore console is registered ... "
+dmesg | grep -q "console \[pstore"
+if [ $? -eq 0 ]; then
+prlog "ok"
+else
+prlog "FAIL"
+fi
+
+prlog -n &q

Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

Hello Mark,

Thank you for your advise.

>> +prlog -n "Checking pmsg file contains TEST_STRING ... "
> Mark this as 'wish to have'

OK. I'll change it to "Checking pmsg file wishes to have TEST_STRING
... ". Should I change other messages in the same way?

> Can TEST_STRING be given an unique value each run, so that on the the
> reboot-comparison run it can be found to be an unique match?

Yes. I'll append /proc/sys/kernel/random/uuid content to TEST_STRING.
I'll also change log directory name from date to the uuid.

> Also confirm that any previous content (which may be binary) is not
> present after reboot, and that totally new content is present.

OK.
As for pmsg, they are possible by checking if the /sys/fs/pstore/pmsg
content perfectly matches the TEST_STRING which was written to /dev/pmsg
before reboot. (The TEST_STRING can be left to a regular file before
reboot as well as reboot_flag.) Is it OK?

Best regards,
Hiraku Toyooka


--
Hiraku Toyooka
Systems Productivity Research Dept. / Linux Technology Center
Center for Technology Innovation - Systems Engineering, Hitachi Ltd.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

Hello, Kees,

Thank you for your advise.

>> +be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as 
persistent store backend$"`

...
> This seems unstable if the system hasn't booted recently or if stuff
> is spamming dmesg. What about examining /sys/module/pstore instead?

OK, I'll update in that way.

Best regards,
Hiraku Toyooka

Kees Cook wrote:

On Tue, Sep 8, 2015 at 4:06 AM, Hiraku Toyooka
<hiraku.toyooka...@hitachi.com> wrote:

The pstore_tests script includes test cases which check pstore's
behavior before crash (and reboot).

The test cases are currently following.

- Check pstore backend is registered
- Check pstore console is registered
- Check /dev/pmsg0 exists
- Write string to /dev/pmsg0

Example usage is following.

make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
pstore_crash_test has not been executed yet. we skip further tests.
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'

We can also see test logs later.

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Shuah Khan <shua...@osg.samsung.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.agu...@hds.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
  tools/testing/selftests/Makefile|1 +
  tools/testing/selftests/pstore/Makefile |   12 +++
  tools/testing/selftests/pstore/common_tests |   45 +++
  tools/testing/selftests/pstore/pstore_tests |   42 +
  4 files changed, 100 insertions(+)
  create mode 100644 tools/testing/selftests/pstore/Makefile
  create mode 100755 tools/testing/selftests/pstore/common_tests
  create mode 100755 tools/testing/selftests/pstore/pstore_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 24ae9e8..b58c72e 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -12,6 +12,7 @@ TARGETS += mount
  TARGETS += mqueue
  TARGETS += net
  TARGETS += powerpc
+TARGETS += pstore
  TARGETS += ptrace
  TARGETS += seccomp
  TARGETS += size
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
new file mode 100644
index 000..40b887d
--- /dev/null
+++ b/tools/testing/selftests/pstore/Makefile
@@ -0,0 +1,12 @@
+# Makefile for pstore selftests.
+# Expects pstore backend is registered.
+
+all:
+
+TEST_PROGS := pstore_tests
+TEST_FILES := common_tests
+
+include ../lib.mk
+
+clean:
+   rm -rf logs/*
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
new file mode 100755
index 000..98611c5
--- /dev/null
+++ b/tools/testing/selftests/pstore/common_tests
@@ -0,0 +1,45 @@
+#!/bin/sh
+
+# common_tests - Shell script commonly used by pstore test scripts
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
+#
+# Released under the terms of the GPL v2.
+
+# Utilities
+errexit() { # message
+  echo "Error: $1" 1>&2
+  exit 1
+}
+
+absdir() { # file_path
+  (cd `dirname $1`; pwd)
+}
+
+# Parameters
+TOP_DIR=`absdir $0`
+LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`/
+TEST_STRING="Testing pstore"
+
+# Preparing logs
+LOG_FILE=$LOG_DIR/`basename $0`.log
+mkdir -p $LOG_DIR || errexit "Failed to make a log directory: $LOG_DIR"
+date > $LOG_FILE
+prlog() { # messages
+  /bin/echo "$@" | tee -a $LOG_FILE
+}
+prlog "=== Pstore unit tests (`basename $0`)==="
+
+# Starting tests
+rc=0
+
+prlog -n "Checking pstore backend is registered ... "
+be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as persistent store 
backend$"`
+if [ $? -eq 0 ]; then
+backend=`echo ${be_msg} | sed -e 's/^.*Registered\ \([a-zA-z0-9-]\+\)\ 
as.*$/\1/g'`
+prlog "ok"
+else
+prlog "FAIL"
+exit 1
+fi


This seems unstable if the system hasn't booted recently or if stuff
is spamming dmesg. What about examining /sys/module/pstore instead?


diff --git a/tools/testing/selftests/pstore/pstore_tests 
b/tools/testing/selftests/pstore/pstore_tests
new file mode 100755
index 000..cbf613c
--- /dev/null
+++ b/tools/testing/selftests/pstore/pstore_tests
@@ -0,0 +1,42 @@
+#!/bin/sh
+
+# pstore_tests - Check pstore's behavior before crash/reboot
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hira

Re: [PATCH 2/2] selftests/pstore: add pstore test scripts going with reboot

[Hiraku Toyooka]

Hello Kees,

>> +run_crash:
>> +   @sh pstore_crash_test || echo "pstore_crash_test: [FAIL]"
>
> This is probably better written to exit 1 on failure, otherwise it
> just _says_ it fails. (Though lots of selftests in the tree already
> have this problem, it's best to avoid the pattern for new stuff.)
> Maybe something like:
>
>  @sh pstore_crash_test || { echo "pstore_crash_test: [FAIL]"; 
exit 1; }


OK. I'll add the "exit 1".

>> +prlog -n "Checking dmesg files exist in pstore filesystem ... "
>> +if [ -e dmesg-${backend}-0 ]; then
>> +prlog "ok"
>> +for f in `ls dmesg-${backend}-*`; do
>> +   prlog -e "\t${f}"
>> +done
>> +else
>> +prlog "FAIL"
>> +rc=1
>> +fi
>
> This test pattern is repeated a lot. Maybe better to create a helper
> function instead? It could make the tests much more readable.

Yes, I should make a helper function in v2.

Best regards,
Hiraku Toyooka
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Re: [PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

Hello Mark,

Thank you for your advise.

>> +prlog -n "Checking pmsg file contains TEST_STRING ... "
> Mark this as 'wish to have'

OK. I'll change it to "Checking pmsg file wishes to have TEST_STRING
... ". Should I change other messages in the same way?

> Can TEST_STRING be given an unique value each run, so that on the the
> reboot-comparison run it can be found to be an unique match?

Yes. I'll append /proc/sys/kernel/random/uuid content to TEST_STRING.
I'll also change log directory name from date to the uuid.

> Also confirm that any previous content (which may be binary) is not
> present after reboot, and that totally new content is present.

OK.
As for pmsg, they are possible by checking if the /sys/fs/pstore/pmsg
content perfectly matches the TEST_STRING which was written to /dev/pmsg
before reboot. (The TEST_STRING can be left to a regular file before
reboot as well as reboot_flag.) Is it OK?

Best regards,
Hiraku Toyooka


--
Hiraku Toyooka
Systems Productivity Research Dept. / Linux Technology Center
Center for Technology Innovation - Systems Engineering, Hitachi Ltd.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
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Please read the FAQ at  http://www.tux.org/lkml/

[PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

The pstore_tests script includes test cases which check pstore's
behavior before crash (and reboot).

The test cases are currently following.

- Check pstore backend is registered
- Check pstore console is registered
- Check /dev/pmsg0 exists
- Write string to /dev/pmsg0

Example usage is following.

make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
pstore_crash_test has not been executed yet. we skip further tests.
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'

We can also see test logs later.

Signed-off-by: Hiraku Toyooka 
Cc: Shuah Khan 
Cc: Tony Luck 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
 tools/testing/selftests/Makefile|1 +
 tools/testing/selftests/pstore/Makefile |   12 +++
 tools/testing/selftests/pstore/common_tests |   45 +++
 tools/testing/selftests/pstore/pstore_tests |   42 +
 4 files changed, 100 insertions(+)
 create mode 100644 tools/testing/selftests/pstore/Makefile
 create mode 100755 tools/testing/selftests/pstore/common_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 24ae9e8..b58c72e 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -12,6 +12,7 @@ TARGETS += mount
 TARGETS += mqueue
 TARGETS += net
 TARGETS += powerpc
+TARGETS += pstore
 TARGETS += ptrace
 TARGETS += seccomp
 TARGETS += size
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
new file mode 100644
index 000..40b887d
--- /dev/null
+++ b/tools/testing/selftests/pstore/Makefile
@@ -0,0 +1,12 @@
+# Makefile for pstore selftests.
+# Expects pstore backend is registered.
+
+all:
+
+TEST_PROGS := pstore_tests
+TEST_FILES := common_tests
+
+include ../lib.mk
+
+clean:
+   rm -rf logs/*
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
new file mode 100755
index 000..98611c5
--- /dev/null
+++ b/tools/testing/selftests/pstore/common_tests
@@ -0,0 +1,45 @@
+#!/bin/sh
+
+# common_tests - Shell script commonly used by pstore test scripts
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka 
+#
+# Released under the terms of the GPL v2.
+
+# Utilities
+errexit() { # message
+  echo "Error: $1" 1>&2
+  exit 1
+}
+
+absdir() { # file_path
+  (cd `dirname $1`; pwd)
+}
+
+# Parameters
+TOP_DIR=`absdir $0`
+LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`/
+TEST_STRING="Testing pstore"
+
+# Preparing logs
+LOG_FILE=$LOG_DIR/`basename $0`.log
+mkdir -p $LOG_DIR || errexit "Failed to make a log directory: $LOG_DIR"
+date > $LOG_FILE
+prlog() { # messages
+  /bin/echo "$@" | tee -a $LOG_FILE
+}
+prlog "=== Pstore unit tests (`basename $0`)==="
+
+# Starting tests
+rc=0
+
+prlog -n "Checking pstore backend is registered ... "
+be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as persistent store 
backend$"`
+if [ $? -eq 0 ]; then
+backend=`echo ${be_msg} | sed -e 's/^.*Registered\ \([a-zA-z0-9-]\+\)\ 
as.*$/\1/g'`
+prlog "ok"
+else
+prlog "FAIL"
+exit 1
+fi
diff --git a/tools/testing/selftests/pstore/pstore_tests 
b/tools/testing/selftests/pstore/pstore_tests
new file mode 100755
index 000..cbf613c
--- /dev/null
+++ b/tools/testing/selftests/pstore/pstore_tests
@@ -0,0 +1,42 @@
+#!/bin/sh
+
+# pstore_tests - Check pstore's behavior before crash/reboot
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka 
+#
+# Released under the terms of the GPL v2.
+
+. ./common_tests
+
+prlog -n "Checking pstore console is registered ... "
+dmesg | grep -q "console \[pstore"
+if [ $? -eq 0 ]; then
+prlog "ok"
+else
+prlog "FAIL"
+fi
+
+prlog -n "Checking /dev/pmsg0 exists ... "
+if [ -e "/dev/pmsg0" ]; then
+prlog "ok"
+else
+prlog "FAIL"
+rc=1
+fi
+
+prlog -n "Writing TEST_STRING to /dev/pmsg0 ... "
+if [ -e "/dev/pmsg0" ]; then
+echo "${TEST_STRING}" > /dev/pmsg0
+if [ $? -eq 0 ]; then
+   prlog "ok"
+else
+   prlog "FAIL"
+   rc=1
+fi
+else
+prlog "FAIL"
+rc=1
+fi
+
+exit $rc

--
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[PATCH 2/2] selftests/pstore: add pstore test scripts going with reboot

[Hiraku Toyooka]

To test pstore in earnest, we have to cause kernel crash and check
pstore filesystem mouted after reboot.

We add two scripts:
 - pstore_crash_test
 This script to cause crash and reboot easily. It is executed by
 'make run_pstore_crash' in selftests.
 - pstore_post_reboot_tests
 This script includes test cases which check pstore's behavior after
 crash and reboot. It is executed together with pstore_tests by
 'make run_tests [-C pstore]' in selftests.

The test cases in pstore_post_reboot_tests are currently following.

- Check pstore backend is registered
- Mount pstore filesystem
- Check dmesg files exist in pstore filesystem
- Check console file exist in pstore filesystem
- Check pmsg file exist in pstore filesystem
- Check dmesg files contain oops end marker
- Check console file contain oops end marker
- Check pmsg file contain the string written before crash
- Remove all files in pstore filesystem

Example usage is following.

...
(kernel crash and reboot)
...
make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
Mounting pstore filesystem ... ok
Checking dmesg files exist in pstore filesystem ... ok
dmesg-ramoops-0
dmesg-ramoops-1
Checking console files exist in pstore filesystem ... ok
console-ramoops-0
Checking pmsg files exist in pstore filesystem ... ok
pmsg-ramoops-0
Checking dmesg files contains oops end marker
dmesg-ramoops-0 ... ok
dmesg-ramoops-1 ... ok
Checking console file contains oops end marker ... ok
Checking pmsg file contains TEST_STRING ... ok
Removing all files in pstore filesystem
console-ramoops-0 ... ok
dmesg-ramoops-0 ... ok
dmesg-ramoops-1 ... ok
pmsg-ramoops-0 ... ok
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'

Signed-off-by: Hiraku Toyooka 
Cc: Shuah Khan 
Cc: Tony Luck 
Cc: Anton Vorontsov 
Cc: Colin Cross 
Cc: Kees Cook 
Cc: Mark Salyzyn 
Cc: Seiji Aguchi 
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
 tools/testing/selftests/pstore/Makefile|7 +
 tools/testing/selftests/pstore/common_tests|1 
 tools/testing/selftests/pstore/pstore_crash_test   |   27 
 .../selftests/pstore/pstore_post_reboot_tests  |  126 
 4 files changed, 159 insertions(+), 2 deletions(-)
 create mode 100755 tools/testing/selftests/pstore/pstore_crash_test
 create mode 100755 tools/testing/selftests/pstore/pstore_post_reboot_tests

diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
index 40b887d..32c408c 100644
--- a/tools/testing/selftests/pstore/Makefile
+++ b/tools/testing/selftests/pstore/Makefile
@@ -3,10 +3,13 @@
 
 all:
 
-TEST_PROGS := pstore_tests
-TEST_FILES := common_tests
+TEST_PROGS := pstore_tests pstore_post_reboot_tests
+TEST_FILES := common_tests pstore_crash_test
 
 include ../lib.mk
 
+run_crash:
+   @sh pstore_crash_test || echo "pstore_crash_test: [FAIL]"
+
 clean:
rm -rf logs/*
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
index 98611c5..8003760 100755
--- a/tools/testing/selftests/pstore/common_tests
+++ b/tools/testing/selftests/pstore/common_tests
@@ -20,6 +20,7 @@ absdir() { # file_path
 # Parameters
 TOP_DIR=`absdir $0`
 LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`/
+REBOOT_FILE=$TOP_DIR/reboot_flag
 TEST_STRING="Testing pstore"
 
 # Preparing logs
diff --git a/tools/testing/selftests/pstore/pstore_crash_test 
b/tools/testing/selftests/pstore/pstore_crash_test
new file mode 100755
index 000..6d0c422
--- /dev/null
+++ b/tools/testing/selftests/pstore/pstore_crash_test
@@ -0,0 +1,27 @@
+#!/bin/sh
+
+# pstore_crash_test - Pstore test shell script which causes crash and reboot
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka 
+#
+# Released under the terms of the GPL v2.
+
+# exit if pstore backend is not registered
+. ./common_tests
+
+prlog "Causing kernel crash ..."
+
+# enable all functions triggered by sysrq
+echo 1 > /proc/sys/kernel/sysrq
+# setting to reboot in 3 seconds after panic
+echo 3 > /proc/sys/kernel/panic
+# setting to cause panic when oops occurs
+echo 1 > /proc/sys/kernel/panic_on_oops
+
+# create a file as reboot flag
+touch $REBOOT_FILE
+sync
+
+# cause crash
+echo c > /proc/sysrq-trigger
diff --git a/tools/testing/selftests/pstore/pstore_post_reboot_tests 
b/tools/testing/selftests/pstore/pstore_post_reboot_tests
new file mode 100755
index 000..0e33366
--- /dev/null
+++ b/tools/testing/selftests/pstore/pstore_post

[PATCH 0/2] selftests/pstore: add pstore test script

[Hiraku Toyooka]

These scripts include test cases which check pstore behavior. This
is useful to avoid regressions of pstore.

Pstore is used across kernel crash, so these test cases are split
into three parts.

 - pstore_tests: check pstore behavior before crash
 - pstore_post_reboot_tests: check pstore behavior after crash and reboot
 - pstore_crash_test: cause kernel crash and reboot

The pstore_test and the pstore_post_reboot_tests are the actual scripts
for testing pstore and are executed in usual selftest's "run_test" target.
On the other hand, the pstore_crash_test is to cause kernel panic and reboot,
so it is executed in new "run_pstore_crash" target which is specified ad-hoc
by users. In addition, there is a "common_tests" script which includes
utilities and test cases used commonly in these scripts.

When the pstore_crash_test is executed, it creates a file as a reboot flag.
The pstore_post_reboot_tests detects whether the file exists or not. If the
file doesn't exists, the test cases are skipped.

These scripts expect that one pstore backend is registered before the
scripts are executed.
Assumed use case is following.

# cd linux/tools/testing/selftests
# make run_tests -C pstore
make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
pstore_crash_test has not been executed yet. we skip further tests.
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'
# make run_pstore_crash
...
(kernel crash and reboot)
...
# make run_tests -C pstore
make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
Mounting pstore filesystem ... ok
Checking dmesg files exist in pstore filesystem ... ok
dmesg-ramoops-0
dmesg-ramoops-1
Checking console files exist in pstore filesystem ... ok
console-ramoops-0
Checking pmsg files exist in pstore filesystem ... ok
pmsg-ramoops-0
Checking dmesg files contains oops end marker
dmesg-ramoops-0 ... ok
dmesg-ramoops-1 ... ok
Checking console file contains oops end marker ... ok
Checking pmsg file contains TEST_STRING ... ok
Removing all files in pstore filesystem 
console-ramoops-0 ... ok
dmesg-ramoops-0 ... ok
dmesg-ramoops-1 ... ok
pmsg-ramoops-0 ... ok
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'


We can also see test logs later.

# cat pstore/logs/20150903-58/pstore_tests.log
...

---

Hiraku Toyooka (2):
  selftests/pstore: add pstore test script for pre-reboot
  selftests/pstore: add pstore test scripts going with reboot


 tools/testing/selftests/Makefile   |1 
 tools/testing/selftests/pstore/Makefile|   15 ++
 tools/testing/selftests/pstore/common_tests|   46 +++
 tools/testing/selftests/pstore/pstore_crash_test   |   27 
 .../selftests/pstore/pstore_post_reboot_tests  |  126 
 tools/testing/selftests/pstore/pstore_tests|   42 +++
 6 files changed, 257 insertions(+)
 create mode 100644 tools/testing/selftests/pstore/Makefile
 create mode 100755 tools/testing/selftests/pstore/common_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_crash_test
 create mode 100755 tools/testing/selftests/pstore/pstore_post_reboot_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_tests

--
Hiraku Toyooka
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[PATCH 1/2] selftests/pstore: add pstore test script for pre-reboot

[Hiraku Toyooka]

The pstore_tests script includes test cases which check pstore's
behavior before crash (and reboot).

The test cases are currently following.

- Check pstore backend is registered
- Check pstore console is registered
- Check /dev/pmsg0 exists
- Write string to /dev/pmsg0

Example usage is following.

make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
pstore_crash_test has not been executed yet. we skip further tests.
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'

We can also see test logs later.

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Shuah Khan <shua...@osg.samsung.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.agu...@hds.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
 tools/testing/selftests/Makefile|1 +
 tools/testing/selftests/pstore/Makefile |   12 +++
 tools/testing/selftests/pstore/common_tests |   45 +++
 tools/testing/selftests/pstore/pstore_tests |   42 +
 4 files changed, 100 insertions(+)
 create mode 100644 tools/testing/selftests/pstore/Makefile
 create mode 100755 tools/testing/selftests/pstore/common_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_tests

diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile
index 24ae9e8..b58c72e 100644
--- a/tools/testing/selftests/Makefile
+++ b/tools/testing/selftests/Makefile
@@ -12,6 +12,7 @@ TARGETS += mount
 TARGETS += mqueue
 TARGETS += net
 TARGETS += powerpc
+TARGETS += pstore
 TARGETS += ptrace
 TARGETS += seccomp
 TARGETS += size
diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
new file mode 100644
index 000..40b887d
--- /dev/null
+++ b/tools/testing/selftests/pstore/Makefile
@@ -0,0 +1,12 @@
+# Makefile for pstore selftests.
+# Expects pstore backend is registered.
+
+all:
+
+TEST_PROGS := pstore_tests
+TEST_FILES := common_tests
+
+include ../lib.mk
+
+clean:
+   rm -rf logs/*
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
new file mode 100755
index 000..98611c5
--- /dev/null
+++ b/tools/testing/selftests/pstore/common_tests
@@ -0,0 +1,45 @@
+#!/bin/sh
+
+# common_tests - Shell script commonly used by pstore test scripts
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
+#
+# Released under the terms of the GPL v2.
+
+# Utilities
+errexit() { # message
+  echo "Error: $1" 1>&2
+  exit 1
+}
+
+absdir() { # file_path
+  (cd `dirname $1`; pwd)
+}
+
+# Parameters
+TOP_DIR=`absdir $0`
+LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`/
+TEST_STRING="Testing pstore"
+
+# Preparing logs
+LOG_FILE=$LOG_DIR/`basename $0`.log
+mkdir -p $LOG_DIR || errexit "Failed to make a log directory: $LOG_DIR"
+date > $LOG_FILE
+prlog() { # messages
+  /bin/echo "$@" | tee -a $LOG_FILE
+}
+prlog "=== Pstore unit tests (`basename $0`)==="
+
+# Starting tests
+rc=0
+
+prlog -n "Checking pstore backend is registered ... "
+be_msg=`dmesg | grep "pstore: Registered [a-zA-Z0-9]\+ as persistent store 
backend$"`
+if [ $? -eq 0 ]; then
+backend=`echo ${be_msg} | sed -e 's/^.*Registered\ \([a-zA-z0-9-]\+\)\ 
as.*$/\1/g'`
+prlog "ok"
+else
+prlog "FAIL"
+exit 1
+fi
diff --git a/tools/testing/selftests/pstore/pstore_tests 
b/tools/testing/selftests/pstore/pstore_tests
new file mode 100755
index 000..cbf613c
--- /dev/null
+++ b/tools/testing/selftests/pstore/pstore_tests
@@ -0,0 +1,42 @@
+#!/bin/sh
+
+# pstore_tests - Check pstore's behavior before crash/reboot
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
+#
+# Released under the terms of the GPL v2.
+
+. ./common_tests
+
+prlog -n "Checking pstore console is registered ... "
+dmesg | grep -q "console \[pstore"
+if [ $? -eq 0 ]; then
+prlog "ok"
+else
+prlog "FAIL"
+fi
+
+prlog -n "Checking /dev/pmsg0 exists ... "
+if [ -e "/dev/pmsg0" ]; then
+prlog "ok"
+else
+prlog "FAIL"
+rc=1
+fi
+
+prlog -n "Writing TEST_STRING to /dev/pmsg0 ... "
+if [ -e "/dev/pmsg0" ]; then
+echo "${TEST_STRING}" &

[PATCH 2/2] selftests/pstore: add pstore test scripts going with reboot

[Hiraku Toyooka]

To test pstore in earnest, we have to cause kernel crash and check
pstore filesystem mouted after reboot.

We add two scripts:
 - pstore_crash_test
 This script to cause crash and reboot easily. It is executed by
 'make run_pstore_crash' in selftests.
 - pstore_post_reboot_tests
 This script includes test cases which check pstore's behavior after
 crash and reboot. It is executed together with pstore_tests by
 'make run_tests [-C pstore]' in selftests.

The test cases in pstore_post_reboot_tests are currently following.

- Check pstore backend is registered
- Mount pstore filesystem
- Check dmesg files exist in pstore filesystem
- Check console file exist in pstore filesystem
- Check pmsg file exist in pstore filesystem
- Check dmesg files contain oops end marker
- Check console file contain oops end marker
- Check pmsg file contain the string written before crash
- Remove all files in pstore filesystem

Example usage is following.

...
(kernel crash and reboot)
...
make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
Mounting pstore filesystem ... ok
Checking dmesg files exist in pstore filesystem ... ok
dmesg-ramoops-0
dmesg-ramoops-1
Checking console files exist in pstore filesystem ... ok
console-ramoops-0
Checking pmsg files exist in pstore filesystem ... ok
pmsg-ramoops-0
Checking dmesg files contains oops end marker
dmesg-ramoops-0 ... ok
dmesg-ramoops-1 ... ok
Checking console file contains oops end marker ... ok
Checking pmsg file contains TEST_STRING ... ok
Removing all files in pstore filesystem
console-ramoops-0 ... ok
dmesg-ramoops-0 ... ok
dmesg-ramoops-1 ... ok
pmsg-ramoops-0 ... ok
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'

Signed-off-by: Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
Cc: Shuah Khan <shua...@osg.samsung.com>
Cc: Tony Luck <tony.l...@intel.com>
Cc: Anton Vorontsov <an...@enomsg.org>
Cc: Colin Cross <ccr...@android.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Mark Salyzyn <saly...@android.com>
Cc: Seiji Aguchi <seiji.agu...@hds.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-...@vger.kernel.org
---
 tools/testing/selftests/pstore/Makefile|7 +
 tools/testing/selftests/pstore/common_tests|1 
 tools/testing/selftests/pstore/pstore_crash_test   |   27 
 .../selftests/pstore/pstore_post_reboot_tests  |  126 
 4 files changed, 159 insertions(+), 2 deletions(-)
 create mode 100755 tools/testing/selftests/pstore/pstore_crash_test
 create mode 100755 tools/testing/selftests/pstore/pstore_post_reboot_tests

diff --git a/tools/testing/selftests/pstore/Makefile 
b/tools/testing/selftests/pstore/Makefile
index 40b887d..32c408c 100644
--- a/tools/testing/selftests/pstore/Makefile
+++ b/tools/testing/selftests/pstore/Makefile
@@ -3,10 +3,13 @@
 
 all:
 
-TEST_PROGS := pstore_tests
-TEST_FILES := common_tests
+TEST_PROGS := pstore_tests pstore_post_reboot_tests
+TEST_FILES := common_tests pstore_crash_test
 
 include ../lib.mk
 
+run_crash:
+   @sh pstore_crash_test || echo "pstore_crash_test: [FAIL]"
+
 clean:
rm -rf logs/*
diff --git a/tools/testing/selftests/pstore/common_tests 
b/tools/testing/selftests/pstore/common_tests
index 98611c5..8003760 100755
--- a/tools/testing/selftests/pstore/common_tests
+++ b/tools/testing/selftests/pstore/common_tests
@@ -20,6 +20,7 @@ absdir() { # file_path
 # Parameters
 TOP_DIR=`absdir $0`
 LOG_DIR=$TOP_DIR/logs/`date +%Y%m%d-%H%M%S`/
+REBOOT_FILE=$TOP_DIR/reboot_flag
 TEST_STRING="Testing pstore"
 
 # Preparing logs
diff --git a/tools/testing/selftests/pstore/pstore_crash_test 
b/tools/testing/selftests/pstore/pstore_crash_test
new file mode 100755
index 000..6d0c422
--- /dev/null
+++ b/tools/testing/selftests/pstore/pstore_crash_test
@@ -0,0 +1,27 @@
+#!/bin/sh
+
+# pstore_crash_test - Pstore test shell script which causes crash and reboot
+#
+# Copyright (C) Hitachi Ltd., 2015
+#  Written by Hiraku Toyooka <hiraku.toyooka...@hitachi.com>
+#
+# Released under the terms of the GPL v2.
+
+# exit if pstore backend is not registered
+. ./common_tests
+
+prlog "Causing kernel crash ..."
+
+# enable all functions triggered by sysrq
+echo 1 > /proc/sys/kernel/sysrq
+# setting to reboot in 3 seconds after panic
+echo 3 > /proc/sys/kernel/panic
+# setting to cause panic when oops occurs
+echo 1 > /proc/sys/kernel/panic_on_oops
+
+# create a file as reboot flag
+touch $REBOOT_FILE
+sync
+
+# cause crash
+echo c 

[PATCH 0/2] selftests/pstore: add pstore test script

[Hiraku Toyooka]

These scripts include test cases which check pstore behavior. This
is useful to avoid regressions of pstore.

Pstore is used across kernel crash, so these test cases are split
into three parts.

 - pstore_tests: check pstore behavior before crash
 - pstore_post_reboot_tests: check pstore behavior after crash and reboot
 - pstore_crash_test: cause kernel crash and reboot

The pstore_test and the pstore_post_reboot_tests are the actual scripts
for testing pstore and are executed in usual selftest's "run_test" target.
On the other hand, the pstore_crash_test is to cause kernel panic and reboot,
so it is executed in new "run_pstore_crash" target which is specified ad-hoc
by users. In addition, there is a "common_tests" script which includes
utilities and test cases used commonly in these scripts.

When the pstore_crash_test is executed, it creates a file as a reboot flag.
The pstore_post_reboot_tests detects whether the file exists or not. If the
file doesn't exists, the test cases are skipped.

These scripts expect that one pstore backend is registered before the
scripts are executed.
Assumed use case is following.

# cd linux/tools/testing/selftests
# make run_tests -C pstore
make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
pstore_crash_test has not been executed yet. we skip further tests.
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'
# make run_pstore_crash
...
(kernel crash and reboot)
...
# make run_tests -C pstore
make: Entering directory '/home/root/selftests/pstore'
=== Pstore unit tests (pstore_tests)===
Checking pstore backend is registered ... ok
Checking pstore console is registered ... ok
Checking /dev/pmsg0 exists ... ok
Writing TEST_STRING to /dev/pmsg0 ... ok
selftests: pstore_tests [PASS]
=== Pstore unit tests (pstore_post_reboot_tests)===
Checking pstore backend is registered ... ok
Mounting pstore filesystem ... ok
Checking dmesg files exist in pstore filesystem ... ok
dmesg-ramoops-0
dmesg-ramoops-1
Checking console files exist in pstore filesystem ... ok
console-ramoops-0
Checking pmsg files exist in pstore filesystem ... ok
pmsg-ramoops-0
Checking dmesg files contains oops end marker
dmesg-ramoops-0 ... ok
dmesg-ramoops-1 ... ok
Checking console file contains oops end marker ... ok
Checking pmsg file contains TEST_STRING ... ok
Removing all files in pstore filesystem 
console-ramoops-0 ... ok
dmesg-ramoops-0 ... ok
dmesg-ramoops-1 ... ok
pmsg-ramoops-0 ... ok
selftests: pstore_post_reboot_tests [PASS]
make: Leaving directory '/home/root/selftests/pstore'


We can also see test logs later.

# cat pstore/logs/20150903-58/pstore_tests.log
...

---

Hiraku Toyooka (2):
  selftests/pstore: add pstore test script for pre-reboot
  selftests/pstore: add pstore test scripts going with reboot


 tools/testing/selftests/Makefile   |1 
 tools/testing/selftests/pstore/Makefile|   15 ++
 tools/testing/selftests/pstore/common_tests|   46 +++
 tools/testing/selftests/pstore/pstore_crash_test   |   27 
 .../selftests/pstore/pstore_post_reboot_tests  |  126 
 tools/testing/selftests/pstore/pstore_tests|   42 +++
 6 files changed, 257 insertions(+)
 create mode 100644 tools/testing/selftests/pstore/Makefile
 create mode 100755 tools/testing/selftests/pstore/common_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_crash_test
 create mode 100755 tools/testing/selftests/pstore/pstore_post_reboot_tests
 create mode 100755 tools/testing/selftests/pstore/pstore_tests

--
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[PATCH v2] ARM: socfpga: add smp_ops.cpu_kill to make kexec/kdump available

[Hiraku Toyooka]

Kexec_load syscall in ARM requires that machine-specific code
has the smp_ops.cpu_kill() before loading kernel image.
This patch adds the cpu_kill(), as a result, kexec reboot and
kernel crash dump become available in mach-socfpga.

Signed-off-by: Hiraku Toyooka 
Cc: Dinh Nguyen 
Cc: Russell King 
Cc: linux-arm-ker...@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
 arch/arm/mach-socfpga/platsmp.c |   12 
 1 file changed, 12 insertions(+)

diff --git a/arch/arm/mach-socfpga/platsmp.c b/arch/arm/mach-socfpga/platsmp.c
index c64d89b..3caf7c3 100644
--- a/arch/arm/mach-socfpga/platsmp.c
+++ b/arch/arm/mach-socfpga/platsmp.c
@@ -95,11 +95,23 @@ static void socfpga_cpu_die(unsigned int cpu)
cpu_do_idle();
 }
 
+/*
+ * We need a dummy function so that platform_can_cpu_hotplug() knows
+ * we support CPU hotplug. However, the function does not need to do
+ * anything, because CPUs going offline just do WFI. We could reset
+ * the CPUs but it would increase power consumption.
+ */
+static int socfpga_cpu_kill(unsigned int cpu)
+{
+   return 1;
+}
+
 struct smp_operations socfpga_smp_ops __initdata = {
.smp_init_cpus  = socfpga_smp_init_cpus,
.smp_prepare_cpus   = socfpga_smp_prepare_cpus,
.smp_boot_secondary = socfpga_boot_secondary,
 #ifdef CONFIG_HOTPLUG_CPU
.cpu_die= socfpga_cpu_die,
+   .cpu_kill   = socfpga_cpu_kill,
 #endif
 };

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[PATCH v2] ARM: socfpga: add smp_ops.cpu_kill to make kexec/kdump available

[Hiraku Toyooka]

Kexec_load syscall in ARM requires that machine-specific code
has the smp_ops.cpu_kill() before loading kernel image.
This patch adds the cpu_kill(), as a result, kexec reboot and
kernel crash dump become available in mach-socfpga.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Dinh Nguyen dingu...@opensource.altera.com
Cc: Russell King li...@arm.linux.org.uk
Cc: linux-arm-ker...@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
 arch/arm/mach-socfpga/platsmp.c |   12 
 1 file changed, 12 insertions(+)

diff --git a/arch/arm/mach-socfpga/platsmp.c b/arch/arm/mach-socfpga/platsmp.c
index c64d89b..3caf7c3 100644
--- a/arch/arm/mach-socfpga/platsmp.c
+++ b/arch/arm/mach-socfpga/platsmp.c
@@ -95,11 +95,23 @@ static void socfpga_cpu_die(unsigned int cpu)
cpu_do_idle();
 }
 
+/*
+ * We need a dummy function so that platform_can_cpu_hotplug() knows
+ * we support CPU hotplug. However, the function does not need to do
+ * anything, because CPUs going offline just do WFI. We could reset
+ * the CPUs but it would increase power consumption.
+ */
+static int socfpga_cpu_kill(unsigned int cpu)
+{
+   return 1;
+}
+
 struct smp_operations socfpga_smp_ops __initdata = {
.smp_init_cpus  = socfpga_smp_init_cpus,
.smp_prepare_cpus   = socfpga_smp_prepare_cpus,
.smp_boot_secondary = socfpga_boot_secondary,
 #ifdef CONFIG_HOTPLUG_CPU
.cpu_die= socfpga_cpu_die,
+   .cpu_kill   = socfpga_cpu_kill,
 #endif
 };

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Re: [PATCH] ARM: socfpga: add smp_ops.cpu_kill to make kexec/kdump available

[Hiraku Toyooka]

Hello, Russell,

On 2015/06/02 17:38, Russell King - ARM Linux wrote:
> I wasn't thinking of SPIs and PPIs, but SGIs - the IPI interrupts coming
> from the boot CPU.

All tasks in a CPU going offline are migrated to other CPUs(finally
CPU0) and the rq is marked with offline before the CPU entering WFI
loop. So IPI is not sent to the secondary CPU.

> If you have a way to reset CPU0, why are you not using this for hotplug
> when a CPU is hot-unplugged?

I think you mean "way to reset CPU1". If so, the reason is an increase
in power consumption in usual hotplug. This is discussed before between
Alan Tull and you. (https://lkml.org/lkml/2014/9/25/37)

Best regards,
Hiraku Toyooka
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Re: [PATCH] ARM: socfpga: add smp_ops.cpu_kill to make kexec/kdump available

[Hiraku Toyooka]

Hello, Russell,

On 2015/06/02 17:38, Russell King - ARM Linux wrote:
 I wasn't thinking of SPIs and PPIs, but SGIs - the IPI interrupts coming
 from the boot CPU.

All tasks in a CPU going offline are migrated to other CPUs(finally
CPU0) and the rq is marked with offline before the CPU entering WFI
loop. So IPI is not sent to the secondary CPU.

 If you have a way to reset CPU0, why are you not using this for hotplug
 when a CPU is hot-unplugged?

I think you mean way to reset CPU1. If so, the reason is an increase
in power consumption in usual hotplug. This is discussed before between
Alan Tull and you. (https://lkml.org/lkml/2014/9/25/37)

Best regards,
Hiraku Toyooka
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Please read the FAQ at  http://www.tux.org/lkml/

[PATCH] ARM: socfpga: add smp_ops.cpu_kill to make kexec/kdump available

[Hiraku Toyooka]

Kexec_load syscall in ARM checks that machine-specific code
has the smp_ops.cpu_kill() before loading kernel image.
This patch adds the cpu_kill(), as a result, kexec reboot and
kernel crash dump become available in mach-socfpga.

Signed-off-by: Hiraku Toyooka 
Cc: Dinh Nguyen 
Cc: Russell King 
Cc: linux-arm-ker...@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
 arch/arm/mach-socfpga/platsmp.c |   11 +++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm/mach-socfpga/platsmp.c b/arch/arm/mach-socfpga/platsmp.c
index c64d89b..a8f0f84 100644
--- a/arch/arm/mach-socfpga/platsmp.c
+++ b/arch/arm/mach-socfpga/platsmp.c
@@ -95,11 +95,22 @@ static void socfpga_cpu_die(unsigned int cpu)
cpu_do_idle();
 }
 
+/*
+ * We need a dummy function so that platform_can_cpu_hotplug() knows
+ * we support CPU hotplug. However, the function does not need to do
+ * anything, because CPUs going offline just do WFI.
+ */
+static int socfpga_cpu_kill(unsigned int cpu)
+{
+   return 1;
+}
+
 struct smp_operations socfpga_smp_ops __initdata = {
.smp_init_cpus  = socfpga_smp_init_cpus,
.smp_prepare_cpus   = socfpga_smp_prepare_cpus,
.smp_boot_secondary = socfpga_boot_secondary,
 #ifdef CONFIG_HOTPLUG_CPU
.cpu_die= socfpga_cpu_die,
+   .cpu_kill   = socfpga_cpu_kill,
 #endif
 };

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[PATCH] ARM: socfpga: add smp_ops.cpu_kill to make kexec/kdump available

[Hiraku Toyooka]

Kexec_load syscall in ARM checks that machine-specific code
has the smp_ops.cpu_kill() before loading kernel image.
This patch adds the cpu_kill(), as a result, kexec reboot and
kernel crash dump become available in mach-socfpga.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Dinh Nguyen dingu...@opensource.altera.com
Cc: Russell King li...@arm.linux.org.uk
Cc: linux-arm-ker...@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
 arch/arm/mach-socfpga/platsmp.c |   11 +++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm/mach-socfpga/platsmp.c b/arch/arm/mach-socfpga/platsmp.c
index c64d89b..a8f0f84 100644
--- a/arch/arm/mach-socfpga/platsmp.c
+++ b/arch/arm/mach-socfpga/platsmp.c
@@ -95,11 +95,22 @@ static void socfpga_cpu_die(unsigned int cpu)
cpu_do_idle();
 }
 
+/*
+ * We need a dummy function so that platform_can_cpu_hotplug() knows
+ * we support CPU hotplug. However, the function does not need to do
+ * anything, because CPUs going offline just do WFI.
+ */
+static int socfpga_cpu_kill(unsigned int cpu)
+{
+   return 1;
+}
+
 struct smp_operations socfpga_smp_ops __initdata = {
.smp_init_cpus  = socfpga_smp_init_cpus,
.smp_prepare_cpus   = socfpga_smp_prepare_cpus,
.smp_boot_secondary = socfpga_boot_secondary,
 #ifdef CONFIG_HOTPLUG_CPU
.cpu_die= socfpga_cpu_die,
+   .cpu_kill   = socfpga_cpu_kill,
 #endif
 };

--
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[tip:perf/urgent] tracing: update documentation of snapshot utility

[tip-bot for Hiraku Toyooka]

Commit-ID:  1abccd7419de9829bcdf9ab1f81d5f6cf74d55d3
Gitweb: http://git.kernel.org/tip/1abccd7419de9829bcdf9ab1f81d5f6cf74d55d3
Author: Hiraku Toyooka 
AuthorDate: Fri, 8 Mar 2013 16:32:25 +0900
Committer:  Steven Rostedt 
CommitDate: Fri, 8 Mar 2013 06:27:11 -0500

tracing: update documentation of snapshot utility

Now, "snapshot" file returns success on a reset of snapshot buffer
even if the buffer wasn't allocated, instead of returning EINVAL.
This patch updates snapshot desctiption according to the change.

Link: http://lkml.kernel.org/r/51399409.4090...@hitachi.com

Signed-off-by: Hiraku Toyooka 
Signed-off-by: Steven Rostedt 
---
 Documentation/trace/ftrace.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 53d6a3c..a372304 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1873,7 +1873,7 @@ feature:
 
status\input  | 0  | 1  |else|
--++++
-   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   not allocated |(do nothing)| alloc+swap |(do nothing)|
--++++
allocated |free|swap|   clear|
--++++
--
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[tip:perf/urgent] tracing: update documentation of snapshot utility

[tip-bot for Hiraku Toyooka]

Commit-ID:  1abccd7419de9829bcdf9ab1f81d5f6cf74d55d3
Gitweb: http://git.kernel.org/tip/1abccd7419de9829bcdf9ab1f81d5f6cf74d55d3
Author: Hiraku Toyooka hiraku.toyooka...@hitachi.com
AuthorDate: Fri, 8 Mar 2013 16:32:25 +0900
Committer:  Steven Rostedt rost...@goodmis.org
CommitDate: Fri, 8 Mar 2013 06:27:11 -0500

tracing: update documentation of snapshot utility

Now, snapshot file returns success on a reset of snapshot buffer
even if the buffer wasn't allocated, instead of returning EINVAL.
This patch updates snapshot desctiption according to the change.

Link: http://lkml.kernel.org/r/51399409.4090...@hitachi.com

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Signed-off-by: Steven Rostedt rost...@goodmis.org
---
 Documentation/trace/ftrace.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 53d6a3c..a372304 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1873,7 +1873,7 @@ feature:
 
status\input  | 0  | 1  |else|
--++++
-   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   not allocated |(do nothing)| alloc+swap |(do nothing)|
--++++
allocated |free|swap|   clear|
--++++
--
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Re: [PATCH 0/2] [GIT PULL][3.9] tracing: Fix in snapshot API

[Hiraku Toyooka]

Steven,

(03/08/2013 12:34 AM), Steven Rostedt wrote:

The second patch, returns success on a reset of the buffer even if
the buffer wasn't allocated. Returning -EINVAL is just confusing.


I realized we should update the snapshot documentation together with
this change.
I attached a patch to update the documentation. Could you include this
patch?

Thanks,
Hiraku Toyooka


From: Hiraku Toyooka 
Subject: [PATCH] tracing: update documentation of snapshot utility

Now, "snapshot" file returns success on a reset of snapshot buffer
even if the buffer wasn't allocated, instead of returning EINVAL.
This patch updates snapshot desctiption according to the change.

Signed-off-by: Hiraku Toyooka 
---
 Documentation/trace/ftrace.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 53d6a3c..a372304 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1873,7 +1873,7 @@ feature:

status\input  | 0  | 1  |else|
--++++
-   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   not allocated |(do nothing)| alloc+swap |(do nothing)|
--++++
allocated |free|swap|   clear|
--++++
--
1.7.11.7

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Re: [PATCH 0/2] [GIT PULL][3.9] tracing: Fix in snapshot API

[Hiraku Toyooka]

Steven,

(03/08/2013 12:34 AM), Steven Rostedt wrote:

The second patch, returns success on a reset of the buffer even if
the buffer wasn't allocated. Returning -EINVAL is just confusing.


I realized we should update the snapshot documentation together with
this change.
I attached a patch to update the documentation. Could you include this
patch?

Thanks,
Hiraku Toyooka


From: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Subject: [PATCH] tracing: update documentation of snapshot utility

Now, snapshot file returns success on a reset of snapshot buffer
even if the buffer wasn't allocated, instead of returning EINVAL.
This patch updates snapshot desctiption according to the change.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
---
 Documentation/trace/ftrace.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 53d6a3c..a372304 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1873,7 +1873,7 @@ feature:

status\input  | 0  | 1  |else|
--++++
-   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   not allocated |(do nothing)| alloc+swap |(do nothing)|
--++++
allocated |free|swap|   clear|
--++++
--
1.7.11.7

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Re: [RFC][PATCH 2/2] tracing: Do not return EINVAL in snapshot when not allocated

[Hiraku Toyooka]

(03/06/2013 10:49 PM), Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)"
> 
> To use the tracing snapshot feature, writing a '1' into the snapshot
> file causes the snapshot buffer to be allocated if it has not already
> been allocated and dose a 'swap' with the main buffer, so that the
> snapshot now contains what was in the main buffer, and the main buffer
> now writes to what was the snapshot buffer.
> 
> To free the snapshot buffer, a '0' is written into the snapshot file.
> 
> To clear the snapshot buffer, any number but a '0' or '1' is written
> into the snapshot file. But if the file is not allocated it returns
> -EINVAL error code. This is rather pointless. It is better just to
> do nothing and return success.
> 
> Cc: Hiraku Toyooka
> Signed-off-by: Steven Rostedt
> ---

Acked-by: Hiraku Toyooka 

>   kernel/trace/trace.c |2 --
>   1 file changed, 2 deletions(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 9e3120b..1f835a8 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -4167,8 +4167,6 @@ tracing_snapshot_write(struct file *filp, const char 
> __user *ubuf, size_t cnt,
>   default:
>   if (current_trace->allocated_snapshot)
>   tracing_reset_online_cpus(_tr);
> - else
> - ret = -EINVAL;
>   break;
>   }
>   
> -- 1.7.10.4 .
> 

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Re: [RFC][PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty

[Hiraku Toyooka]

(03/06/2013 10:49 PM), Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)"
> 
> When cat'ing the snapshot file, instead of showing an empty trace
> header like the trace file does, show how to use the snapshot
> feature.
> 
> Also, this is a good place to show if the snapshot has been allocated
> or not. Users may want to "pre allocate" the snapshot to have a fast
> "swap" of the current buffer. Otherwise, a swap would be slow and might
> fail as it would need to allocate the snapshot buffer, and that might
> fail under tight memory constraints.
> 
> Here's what it looked like before:
> 
>   # tracer: nop
>   #
>   # entries-in-buffer/entries-written: 0/0   #P:4
>   #
>   #  _-=> irqs-off
>   # / _=> need-resched
>   #| / _---=> hardirq/softirq
>   #|| / _--=> preempt-depth
>   #||| / delay
>   #   TASK-PID   CPU#  TIMESTAMP  FUNCTION
>   #  | |   |      | |
> 
> Here's what it looks like now:
> 
>   # tracer: nop
>   #
>   #
>   # * Snapshot is freed *
>   #
>   # Snapshot commands:
>   # echo 0 > snapshot : Clears and frees snapshot buffer
>   # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
>   #  Takes a snapshot of the main buffer.
>   # echo 2 > snapshot : Clears snapshot buffer (but does not allocate)
>   #  (Doesn't have to be '2' works with any number that
>   #   is not a '0' or '1')
> 
> Cc: Hiraku Toyooka
> Signed-off-by: Steven Rostedt
> ---

Acked-by: Hiraku Toyooka 

>   kernel/trace/trace.c |   25 -
>   1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index c2e2c23..9e3120b 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -2400,6 +2400,27 @@ static void test_ftrace_alive(struct seq_file *m)
>   seq_printf(m, "#  MAY BE MISSING FUNCTION EVENTS\n");
>   }
>   
> +#ifdef CONFIG_TRACER_MAX_TRACE
> +static void print_snapshot_help(struct seq_file *m, struct trace_iterator 
> *iter)
> +{
> + if (iter->trace->allocated_snapshot)
> + seq_printf(m, "#\n# * Snapshot is allocated *\n#\n");
> + else
> + seq_printf(m, "#\n# * Snapshot is freed *\n#\n");
> +
> + seq_printf(m, "# Snapshot commands:\n");
> + seq_printf(m, "# echo 0 > snapshot : Clears and frees snapshot 
> buffer\n");
> + seq_printf(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not 
> already allocated.\n");
> + seq_printf(m, "#  Takes a snapshot of the main 
> buffer.\n");
> + seq_printf(m, "# echo 2 > snapshot : Clears snapshot buffer (but does 
> not allocate)\n");
> + seq_printf(m, "#  (Doesn't have to be '2' works 
> with any number that\n");
> + seq_printf(m, "#   is not a '0' or '1')\n");
> +}
> +#else
> +/* Should never be called */
> +static inline void print_snapshot_help(struct seq_file *m, struct 
> trace_iterator *iter) { }
> +#endif
> +
>   static int s_show(struct seq_file *m, void *v)
>   {
>   struct trace_iterator *iter = v;
> @@ -2411,7 +2432,9 @@ static int s_show(struct seq_file *m, void *v)
>   seq_puts(m, "#\n");
>   test_ftrace_alive(m);
>   }
> - if (iter->trace && iter->trace->print_header)
> + if (iter->snapshot && trace_empty(iter))
> + print_snapshot_help(m, iter);
> + else if (iter->trace && iter->trace->print_header)
>   iter->trace->print_header(m);
>   else
>   trace_default_header(m);
> -- 1.7.10.4 .
> 

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Re: snapshot error on non allocated buffer?

[Hiraku Toyooka]

Hi Steven,

(03/06/2013 12:50 AM), Steven Rostedt wrote:

Hi Hiraku,

I'm doing a lot of reconstruction of ftrace's buffering, and I'm also
modifying a lot of the snapshot feature to work with the new stuff
that's coming.



Many thanks. I'm trying your multi-buffer patches.


I'm looking at the -EINVAL when you write something other than '0' or
'1' into the snapshot file when the snapshot is not allocated. I'm
thinking that it should just return as if it succeeded. I don't
understand why it should return -EINVAL?



I thought that it might be a little strange if the clear operation
succeeded in spite of the non-allocated buffer.
(Actually, I simply implemented as you said, though.)

But I don't have trouble even if it succeeds, so I'll modify the I/F
to make it return successfully.


Now if you want to know if the snapshot is allocated or not, I have a
patch that shows how to use the snapshot feature when the snapshot is
empty, and also give the status of the snapshot itself:

[root] # cat /debug/tracing/snapshot
# tracer: nop
#
#
# * Snapshot is freed *
#
# Snapshot commands:
# echo 0 > snapshot : Clears and frees snapshot buffer
# echo 1 > snapshot : Allocates snapshot buffer, if not already
allocated.
#  Takes a snapshot of the main buffer.
# echo 2 > snapshot : Clears snapshot buffer (but does not allocate)
#  (Doesn't have to be '2' works with any number
that
#   is not a '0' or '1')

[root] # echo 1 > /debug/tracing/snapshot
[root] # echo 2 > /debug/tracing/snapshot
[root] # cat /debug/tracing/snapshot
# tracer: nop
#
#
# * Snapshot is allocated *
#
# Snapshot commands:
# echo 0 > snapshot : Clears and frees snapshot buffer
# echo 1 > snapshot : Allocates snapshot buffer, if not already
allocated.
#  Takes a snapshot of the main buffer.
# echo 2 > snapshot : Clears snapshot buffer (but does not allocate)
#  (Doesn't have to be '2' works with any number
that
#   is not a '0' or '1')



This seems good for me and also users.



As this is a new feature for 3.9, and we are still in -rc1, I think this
might be a good thing to add now. As well as not returning -EINVAL on
writing to the file when the snapshot buffer isn't allocated.

What do you think?



I think it's OK.
I'll send a patch to make the file not return -EINVAL. Does it need to
be based on 3.9-rc1 or tip tree?

Thanks,
Hiraku Toyooka

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Re: snapshot error on non allocated buffer?

[Hiraku Toyooka]

Hi Steven,

(03/06/2013 12:50 AM), Steven Rostedt wrote:

Hi Hiraku,

I'm doing a lot of reconstruction of ftrace's buffering, and I'm also
modifying a lot of the snapshot feature to work with the new stuff
that's coming.



Many thanks. I'm trying your multi-buffer patches.


I'm looking at the -EINVAL when you write something other than '0' or
'1' into the snapshot file when the snapshot is not allocated. I'm
thinking that it should just return as if it succeeded. I don't
understand why it should return -EINVAL?



I thought that it might be a little strange if the clear operation
succeeded in spite of the non-allocated buffer.
(Actually, I simply implemented as you said, though.)

But I don't have trouble even if it succeeds, so I'll modify the I/F
to make it return successfully.


Now if you want to know if the snapshot is allocated or not, I have a
patch that shows how to use the snapshot feature when the snapshot is
empty, and also give the status of the snapshot itself:

[root] # cat /debug/tracing/snapshot
# tracer: nop
#
#
# * Snapshot is freed *
#
# Snapshot commands:
# echo 0  snapshot : Clears and frees snapshot buffer
# echo 1  snapshot : Allocates snapshot buffer, if not already
allocated.
#  Takes a snapshot of the main buffer.
# echo 2  snapshot : Clears snapshot buffer (but does not allocate)
#  (Doesn't have to be '2' works with any number
that
#   is not a '0' or '1')

[root] # echo 1  /debug/tracing/snapshot
[root] # echo 2  /debug/tracing/snapshot
[root] # cat /debug/tracing/snapshot
# tracer: nop
#
#
# * Snapshot is allocated *
#
# Snapshot commands:
# echo 0  snapshot : Clears and frees snapshot buffer
# echo 1  snapshot : Allocates snapshot buffer, if not already
allocated.
#  Takes a snapshot of the main buffer.
# echo 2  snapshot : Clears snapshot buffer (but does not allocate)
#  (Doesn't have to be '2' works with any number
that
#   is not a '0' or '1')



This seems good for me and also users.



As this is a new feature for 3.9, and we are still in -rc1, I think this
might be a good thing to add now. As well as not returning -EINVAL on
writing to the file when the snapshot buffer isn't allocated.

What do you think?



I think it's OK.
I'll send a patch to make the file not return -EINVAL. Does it need to
be based on 3.9-rc1 or tip tree?

Thanks,
Hiraku Toyooka

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Re: [RFC][PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty

[Hiraku Toyooka]

(03/06/2013 10:49 PM), Steven Rostedt wrote:
 From: Steven Rostedt (Red Hat)srost...@redhat.com
 
 When cat'ing the snapshot file, instead of showing an empty trace
 header like the trace file does, show how to use the snapshot
 feature.
 
 Also, this is a good place to show if the snapshot has been allocated
 or not. Users may want to pre allocate the snapshot to have a fast
 swap of the current buffer. Otherwise, a swap would be slow and might
 fail as it would need to allocate the snapshot buffer, and that might
 fail under tight memory constraints.
 
 Here's what it looked like before:
 
   # tracer: nop
   #
   # entries-in-buffer/entries-written: 0/0   #P:4
   #
   #  _-= irqs-off
   # / _= need-resched
   #| / _---= hardirq/softirq
   #|| / _--= preempt-depth
   #||| / delay
   #   TASK-PID   CPU#  TIMESTAMP  FUNCTION
   #  | |   |      | |
 
 Here's what it looks like now:
 
   # tracer: nop
   #
   #
   # * Snapshot is freed *
   #
   # Snapshot commands:
   # echo 0  snapshot : Clears and frees snapshot buffer
   # echo 1  snapshot : Allocates snapshot buffer, if not already allocated.
   #  Takes a snapshot of the main buffer.
   # echo 2  snapshot : Clears snapshot buffer (but does not allocate)
   #  (Doesn't have to be '2' works with any number that
   #   is not a '0' or '1')
 
 Cc: Hiraku Toyookahiraku.toyooka...@hitachi.com
 Signed-off-by: Steven Rostedtrost...@goodmis.org
 ---

Acked-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com

   kernel/trace/trace.c |   25 -
   1 file changed, 24 insertions(+), 1 deletion(-)
 
 diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
 index c2e2c23..9e3120b 100644
 --- a/kernel/trace/trace.c
 +++ b/kernel/trace/trace.c
 @@ -2400,6 +2400,27 @@ static void test_ftrace_alive(struct seq_file *m)
   seq_printf(m, #  MAY BE MISSING FUNCTION EVENTS\n);
   }
   
 +#ifdef CONFIG_TRACER_MAX_TRACE
 +static void print_snapshot_help(struct seq_file *m, struct trace_iterator 
 *iter)
 +{
 + if (iter-trace-allocated_snapshot)
 + seq_printf(m, #\n# * Snapshot is allocated *\n#\n);
 + else
 + seq_printf(m, #\n# * Snapshot is freed *\n#\n);
 +
 + seq_printf(m, # Snapshot commands:\n);
 + seq_printf(m, # echo 0  snapshot : Clears and frees snapshot 
 buffer\n);
 + seq_printf(m, # echo 1  snapshot : Allocates snapshot buffer, if not 
 already allocated.\n);
 + seq_printf(m, #  Takes a snapshot of the main 
 buffer.\n);
 + seq_printf(m, # echo 2  snapshot : Clears snapshot buffer (but does 
 not allocate)\n);
 + seq_printf(m, #  (Doesn't have to be '2' works 
 with any number that\n);
 + seq_printf(m, #   is not a '0' or '1')\n);
 +}
 +#else
 +/* Should never be called */
 +static inline void print_snapshot_help(struct seq_file *m, struct 
 trace_iterator *iter) { }
 +#endif
 +
   static int s_show(struct seq_file *m, void *v)
   {
   struct trace_iterator *iter = v;
 @@ -2411,7 +2432,9 @@ static int s_show(struct seq_file *m, void *v)
   seq_puts(m, #\n);
   test_ftrace_alive(m);
   }
 - if (iter-trace  iter-trace-print_header)
 + if (iter-snapshot  trace_empty(iter))
 + print_snapshot_help(m, iter);
 + else if (iter-trace  iter-trace-print_header)
   iter-trace-print_header(m);
   else
   trace_default_header(m);
 -- 1.7.10.4 .
 

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Re: [RFC][PATCH 2/2] tracing: Do not return EINVAL in snapshot when not allocated

[Hiraku Toyooka]

(03/06/2013 10:49 PM), Steven Rostedt wrote:
 From: Steven Rostedt (Red Hat)srost...@redhat.com
 
 To use the tracing snapshot feature, writing a '1' into the snapshot
 file causes the snapshot buffer to be allocated if it has not already
 been allocated and dose a 'swap' with the main buffer, so that the
 snapshot now contains what was in the main buffer, and the main buffer
 now writes to what was the snapshot buffer.
 
 To free the snapshot buffer, a '0' is written into the snapshot file.
 
 To clear the snapshot buffer, any number but a '0' or '1' is written
 into the snapshot file. But if the file is not allocated it returns
 -EINVAL error code. This is rather pointless. It is better just to
 do nothing and return success.
 
 Cc: Hiraku Toyookahiraku.toyooka...@hitachi.com
 Signed-off-by: Steven Rostedtrost...@goodmis.org
 ---

Acked-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com

   kernel/trace/trace.c |2 --
   1 file changed, 2 deletions(-)
 
 diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
 index 9e3120b..1f835a8 100644
 --- a/kernel/trace/trace.c
 +++ b/kernel/trace/trace.c
 @@ -4167,8 +4167,6 @@ tracing_snapshot_write(struct file *filp, const char 
 __user *ubuf, size_t cnt,
   default:
   if (current_trace-allocated_snapshot)
   tracing_reset_online_cpus(max_tr);
 - else
 - ret = -EINVAL;
   break;
   }
   
 -- 1.7.10.4 .
 

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[tip:perf/core] tracing: Add documentation of snapshot utility

[tip-bot for Hiraku Toyooka]

Commit-ID:  c1043fcda1b9e8e5144cfdaee7be262c50dbdead
Gitweb: http://git.kernel.org/tip/c1043fcda1b9e8e5144cfdaee7be262c50dbdead
Author: Hiraku Toyooka 
AuthorDate: Wed, 26 Dec 2012 11:53:09 +0900
Committer:  Steven Rostedt 
CommitDate: Wed, 30 Jan 2013 11:02:07 -0500

tracing: Add documentation of snapshot utility

This patch adds snapshot description in ftrace documentation.
This description includes what the snapshot is and how to use it.

Link: http://lkml.kernel.org/r/20121226025309.3252.150.stgit@liselsia

Cc: Rob Landley 
Signed-off-by: Hiraku Toyooka 
Signed-off-by: Steven Rostedt 
---
 Documentation/trace/ftrace.txt | 83 ++
 1 file changed, 83 insertions(+)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 6f51fed..53d6a3c 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1842,6 +1842,89 @@ an error.
  # cat buffer_size_kb
 85
 
+Snapshot
+
+CONFIG_TRACER_SNAPSHOT makes a generic snapshot feature
+available to all non latency tracers. (Latency tracers which
+record max latency, such as "irqsoff" or "wakeup", can't use
+this feature, since those are already using the snapshot
+mechanism internally.)
+
+Snapshot preserves a current trace buffer at a particular point
+in time without stopping tracing. Ftrace swaps the current
+buffer with a spare buffer, and tracing continues in the new
+current (=previous spare) buffer.
+
+The following debugfs files in "tracing" are related to this
+feature:
+
+  snapshot:
+
+   This is used to take a snapshot and to read the output
+   of the snapshot. Echo 1 into this file to allocate a
+   spare buffer and to take a snapshot (swap), then read
+   the snapshot from this file in the same format as
+   "trace" (described above in the section "The File
+   System"). Both reads snapshot and tracing are executable
+   in parallel. When the spare buffer is allocated, echoing
+   0 frees it, and echoing else (positive) values clear the
+   snapshot contents.
+   More details are shown in the table below.
+
+   status\input  | 0  | 1  |else|
+   --++++
+   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   --++++
+   allocated |free|swap|   clear|
+   --++++
+
+Here is an example of using the snapshot feature.
+
+ # echo 1 > events/sched/enable
+ # echo 1 > snapshot
+ # cat snapshot
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 71/71   #P:8
+#
+#  _-=> irqs-off
+# / _=> need-resched
+#| / _---=> hardirq/softirq
+#|| / _--=> preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  -0 [005] d...  2440.603828: sched_switch: 
prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2242 next_prio=120
+   sleep-2242  [005] d...  2440.603846: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2242 prev_prio=120 prev_state=R ==> 
next_comm=kworker/5:1 next_pid=60 next_prio=120
+[...]
+  -0 [002] d...  2440.707230: sched_switch: 
prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2229 next_prio=120
+
+ # cat trace
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 77/77   #P:8
+#
+#  _-=> irqs-off
+# / _=> need-resched
+#| / _---=> hardirq/softirq
+#|| / _--=> preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  -0 [007] d...  2440.707395: sched_switch: 
prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2243 next_prio=120
+ snapshot-test-2-2229  [002] d...  2440.707438: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2229 prev_prio=120 prev_state=S ==> 
next_comm=swapper/2 next_pid=0 next_prio=120
+[...]
+
+
+If you try to use this snapshot feature when current tracer is
+one of the latency tracers, you will get the following results.
+
+ # echo wakeup > current_tracer
+ # echo 1 > snapshot
+bash: echo: write error: Device or resource busy
+ # cat snapshot
+cat: snapshot: Device or resource busy
+
 ---
 
 More details can be found in the source code, in the
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[tip:perf/core] tracing: Make a snapshot feature available from userspace

[tip-bot for Hiraku Toyooka]

Commit-ID:  debdd57f5145f3c6a4b3f8d0126abd1a2def7fc6
Gitweb: http://git.kernel.org/tip/debdd57f5145f3c6a4b3f8d0126abd1a2def7fc6
Author: Hiraku Toyooka 
AuthorDate: Wed, 26 Dec 2012 11:53:00 +0900
Committer:  Steven Rostedt 
CommitDate: Wed, 30 Jan 2013 11:02:06 -0500

tracing: Make a snapshot feature available from userspace

Ftrace has a snapshot feature available from kernel space and
latency tracers (e.g. irqsoff) are using it. This patch enables
user applictions to take a snapshot via debugfs.

Add "snapshot" debugfs file in "tracing" directory.

  snapshot:
This is used to take a snapshot and to read the output of the
snapshot.

 # echo 1 > snapshot

This will allocate the spare buffer for snapshot (if it is
not allocated), and take a snapshot.

 # cat snapshot

This will show contents of the snapshot.

 # echo 0 > snapshot

This will free the snapshot if it is allocated.

Any other positive values will clear the snapshot contents if
the snapshot is allocated, or return EINVAL if it is not allocated.

Link: http://lkml.kernel.org/r/20121226025300.3252.86850.stgit@liselsia

Cc: Jiri Olsa 
Cc: David Sharp 
Signed-off-by: Hiraku Toyooka 
[
   Fixed irqsoff selftest and also a conflict with a change
   that fixes the update_max_tr.
]
Signed-off-by: Steven Rostedt 
---
 include/linux/ftrace_event.h |   3 +
 kernel/trace/Kconfig |  10 +++
 kernel/trace/trace.c | 166 ---
 kernel/trace/trace.h |   1 +
 4 files changed, 154 insertions(+), 26 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 6f8d0b7..13a54d0 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -83,6 +83,9 @@ struct trace_iterator {
longidx;
 
cpumask_var_t   started;
+
+   /* it's true when current open file is snapshot */
+   boolsnapshot;
 };
 
 enum trace_iter_flags {
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index cdc9d28..3656756 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -253,6 +253,16 @@ config FTRACE_SYSCALLS
help
  Basic tracer to catch the syscall entry and exit events.
 
+config TRACER_SNAPSHOT
+   bool "Create a snapshot trace buffer"
+   select TRACER_MAX_TRACE
+   help
+ Allow tracing users to take snapshot of the current buffer using the
+ ftrace interface, e.g.:
+
+ echo 1 > /sys/kernel/debug/tracing/snapshot
+ cat snapshot
+
 config TRACE_BRANCH_PROFILING
bool
select GENERIC_TRACER
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2c72466..70dce64 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -710,12 +710,11 @@ update_max_tr(struct trace_array *tr, struct task_struct 
*tsk, int cpu)
 
WARN_ON_ONCE(!irqs_disabled());
 
-   /* If we disabled the tracer, stop now */
-   if (current_trace == _trace)
-   return;
-
-   if (WARN_ON_ONCE(!current_trace->use_max_tr))
+   if (!current_trace->allocated_snapshot) {
+   /* Only the nop tracer should hit this when disabling */
+   WARN_ON_ONCE(current_trace != _trace);
return;
+   }
 
arch_spin_lock(_max_lock);
 
@@ -743,10 +742,8 @@ update_max_tr_single(struct trace_array *tr, struct 
task_struct *tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace->use_max_tr) {
-   WARN_ON_ONCE(1);
+   if (WARN_ON_ONCE(!current_trace->allocated_snapshot))
return;
-   }
 
arch_spin_lock(_max_lock);
 
@@ -866,10 +863,13 @@ int register_tracer(struct tracer *type)
 
current_trace = type;
 
-   /* If we expanded the buffers, make sure the max is expanded 
too */
-   if (ring_buffer_expanded && type->use_max_tr)
-   ring_buffer_resize(max_tr.buffer, trace_buf_size,
-   RING_BUFFER_ALL_CPUS);
+   if (type->use_max_tr) {
+   /* If we expanded the buffers, make sure the max is 
expanded too */
+   if (ring_buffer_expanded)
+   ring_buffer_resize(max_tr.buffer, 
trace_buf_size,
+  RING_BUFFER_ALL_CPUS);
+   type->allocated_snapshot = true;
+   }
 
/* the test is responsible for initializing and enabling */
pr_info("Testing tracer %s: ", type->name);
@@ -885,10 +885,14 @@ int register_tracer(struct tracer *type)
/* Only reset on passing, to avoid touching corrupted buffers */
tracing_reset_online_cpus(tr);
 
-   /

[tip:perf/core] tracing: Replace static old_tracer check of tracer name

[tip-bot for Hiraku Toyooka]

Commit-ID:  2fd196ec1eab2623096e7fc7e6f3976160392bce
Gitweb: http://git.kernel.org/tip/2fd196ec1eab2623096e7fc7e6f3976160392bce
Author: Hiraku Toyooka 
AuthorDate: Wed, 26 Dec 2012 11:52:52 +0900
Committer:  Steven Rostedt 
CommitDate: Wed, 30 Jan 2013 11:02:05 -0500

tracing: Replace static old_tracer check of tracer name

Currently the trace buffer read functions use a static variable
"old_tracer" for detecting if the current tracer changes. This
was suitable for a single trace file ("trace"), but to add a
snapshot feature that will use the same function for its file,
a check against a static variable is not sufficient.

To use the output functions for two different files, instead of
storing the current tracer in a static variable, as the trace
iterator descriptor contains a pointer to the original current
tracer's name, that pointer can now be used to check if the
current tracer has changed between different reads of the trace
file.

Link: http://lkml.kernel.org/r/20121226025252.3252.9276.stgit@liselsia

Signed-off-by: Hiraku Toyooka 
Signed-off-by: Steven Rostedt 
---
 kernel/trace/trace.c | 22 +-
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 90a1c71..2c72466 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1948,18 +1948,20 @@ void tracing_iter_reset(struct trace_iterator *iter, 
int cpu)
 static void *s_start(struct seq_file *m, loff_t *pos)
 {
struct trace_iterator *iter = m->private;
-   static struct tracer *old_tracer;
int cpu_file = iter->cpu_file;
void *p = NULL;
loff_t l = 0;
int cpu;
 
-   /* copy the tracer to avoid using a global lock all around */
+   /*
+* copy the tracer to avoid using a global lock all around.
+* iter->trace is a copy of current_trace, the pointer to the
+* name may be used instead of a strcmp(), as iter->trace->name
+* will point to the same string as current_trace->name.
+*/
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace && iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
-   }
mutex_unlock(_types_lock);
 
atomic_inc(_record_cmdline_disabled);
@@ -3494,7 +3496,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
  size_t cnt, loff_t *ppos)
 {
struct trace_iterator *iter = filp->private_data;
-   static struct tracer *old_tracer;
ssize_t sret;
 
/* return any leftover data */
@@ -3506,10 +3507,8 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace && iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
-   }
mutex_unlock(_types_lock);
 
/*
@@ -3665,7 +3664,6 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
.ops= _pipe_buf_ops,
.spd_release= tracing_spd_release_pipe,
};
-   static struct tracer *old_tracer;
ssize_t ret;
size_t rem;
unsigned int i;
@@ -3675,10 +3673,8 @@ static ssize_t tracing_splice_read_pipe(struct file 
*filp,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace && iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
-   }
mutex_unlock(_types_lock);
 
mutex_lock(>mutex);
--
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[tip:perf/core] tracing: Replace static old_tracer check of tracer name

[tip-bot for Hiraku Toyooka]

Commit-ID:  2fd196ec1eab2623096e7fc7e6f3976160392bce
Gitweb: http://git.kernel.org/tip/2fd196ec1eab2623096e7fc7e6f3976160392bce
Author: Hiraku Toyooka hiraku.toyooka...@hitachi.com
AuthorDate: Wed, 26 Dec 2012 11:52:52 +0900
Committer:  Steven Rostedt rost...@goodmis.org
CommitDate: Wed, 30 Jan 2013 11:02:05 -0500

tracing: Replace static old_tracer check of tracer name

Currently the trace buffer read functions use a static variable
old_tracer for detecting if the current tracer changes. This
was suitable for a single trace file (trace), but to add a
snapshot feature that will use the same function for its file,
a check against a static variable is not sufficient.

To use the output functions for two different files, instead of
storing the current tracer in a static variable, as the trace
iterator descriptor contains a pointer to the original current
tracer's name, that pointer can now be used to check if the
current tracer has changed between different reads of the trace
file.

Link: http://lkml.kernel.org/r/20121226025252.3252.9276.stgit@liselsia

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Signed-off-by: Steven Rostedt rost...@goodmis.org
---
 kernel/trace/trace.c | 22 +-
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 90a1c71..2c72466 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1948,18 +1948,20 @@ void tracing_iter_reset(struct trace_iterator *iter, 
int cpu)
 static void *s_start(struct seq_file *m, loff_t *pos)
 {
struct trace_iterator *iter = m-private;
-   static struct tracer *old_tracer;
int cpu_file = iter-cpu_file;
void *p = NULL;
loff_t l = 0;
int cpu;
 
-   /* copy the tracer to avoid using a global lock all around */
+   /*
+* copy the tracer to avoid using a global lock all around.
+* iter-trace is a copy of current_trace, the pointer to the
+* name may be used instead of a strcmp(), as iter-trace-name
+* will point to the same string as current_trace-name.
+*/
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace  iter-trace-name != current_trace-name))
*iter-trace = *current_trace;
-   }
mutex_unlock(trace_types_lock);
 
atomic_inc(trace_record_cmdline_disabled);
@@ -3494,7 +3496,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
  size_t cnt, loff_t *ppos)
 {
struct trace_iterator *iter = filp-private_data;
-   static struct tracer *old_tracer;
ssize_t sret;
 
/* return any leftover data */
@@ -3506,10 +3507,8 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace  iter-trace-name != current_trace-name))
*iter-trace = *current_trace;
-   }
mutex_unlock(trace_types_lock);
 
/*
@@ -3665,7 +3664,6 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
.ops= tracing_pipe_buf_ops,
.spd_release= tracing_spd_release_pipe,
};
-   static struct tracer *old_tracer;
ssize_t ret;
size_t rem;
unsigned int i;
@@ -3675,10 +3673,8 @@ static ssize_t tracing_splice_read_pipe(struct file 
*filp,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace  iter-trace-name != current_trace-name))
*iter-trace = *current_trace;
-   }
mutex_unlock(trace_types_lock);
 
mutex_lock(iter-mutex);
--
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Please read the FAQ at  http://www.tux.org/lkml/

[tip:perf/core] tracing: Make a snapshot feature available from userspace

[tip-bot for Hiraku Toyooka]

Commit-ID:  debdd57f5145f3c6a4b3f8d0126abd1a2def7fc6
Gitweb: http://git.kernel.org/tip/debdd57f5145f3c6a4b3f8d0126abd1a2def7fc6
Author: Hiraku Toyooka hiraku.toyooka...@hitachi.com
AuthorDate: Wed, 26 Dec 2012 11:53:00 +0900
Committer:  Steven Rostedt rost...@goodmis.org
CommitDate: Wed, 30 Jan 2013 11:02:06 -0500

tracing: Make a snapshot feature available from userspace

Ftrace has a snapshot feature available from kernel space and
latency tracers (e.g. irqsoff) are using it. This patch enables
user applictions to take a snapshot via debugfs.

Add snapshot debugfs file in tracing directory.

  snapshot:
This is used to take a snapshot and to read the output of the
snapshot.

 # echo 1  snapshot

This will allocate the spare buffer for snapshot (if it is
not allocated), and take a snapshot.

 # cat snapshot

This will show contents of the snapshot.

 # echo 0  snapshot

This will free the snapshot if it is allocated.

Any other positive values will clear the snapshot contents if
the snapshot is allocated, or return EINVAL if it is not allocated.

Link: http://lkml.kernel.org/r/20121226025300.3252.86850.stgit@liselsia

Cc: Jiri Olsa jo...@redhat.com
Cc: David Sharp dhsh...@google.com
Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
[
   Fixed irqsoff selftest and also a conflict with a change
   that fixes the update_max_tr.
]
Signed-off-by: Steven Rostedt rost...@goodmis.org
---
 include/linux/ftrace_event.h |   3 +
 kernel/trace/Kconfig |  10 +++
 kernel/trace/trace.c | 166 ---
 kernel/trace/trace.h |   1 +
 4 files changed, 154 insertions(+), 26 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 6f8d0b7..13a54d0 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -83,6 +83,9 @@ struct trace_iterator {
longidx;
 
cpumask_var_t   started;
+
+   /* it's true when current open file is snapshot */
+   boolsnapshot;
 };
 
 enum trace_iter_flags {
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index cdc9d28..3656756 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -253,6 +253,16 @@ config FTRACE_SYSCALLS
help
  Basic tracer to catch the syscall entry and exit events.
 
+config TRACER_SNAPSHOT
+   bool Create a snapshot trace buffer
+   select TRACER_MAX_TRACE
+   help
+ Allow tracing users to take snapshot of the current buffer using the
+ ftrace interface, e.g.:
+
+ echo 1  /sys/kernel/debug/tracing/snapshot
+ cat snapshot
+
 config TRACE_BRANCH_PROFILING
bool
select GENERIC_TRACER
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2c72466..70dce64 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -710,12 +710,11 @@ update_max_tr(struct trace_array *tr, struct task_struct 
*tsk, int cpu)
 
WARN_ON_ONCE(!irqs_disabled());
 
-   /* If we disabled the tracer, stop now */
-   if (current_trace == nop_trace)
-   return;
-
-   if (WARN_ON_ONCE(!current_trace-use_max_tr))
+   if (!current_trace-allocated_snapshot) {
+   /* Only the nop tracer should hit this when disabling */
+   WARN_ON_ONCE(current_trace != nop_trace);
return;
+   }
 
arch_spin_lock(ftrace_max_lock);
 
@@ -743,10 +742,8 @@ update_max_tr_single(struct trace_array *tr, struct 
task_struct *tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace-use_max_tr) {
-   WARN_ON_ONCE(1);
+   if (WARN_ON_ONCE(!current_trace-allocated_snapshot))
return;
-   }
 
arch_spin_lock(ftrace_max_lock);
 
@@ -866,10 +863,13 @@ int register_tracer(struct tracer *type)
 
current_trace = type;
 
-   /* If we expanded the buffers, make sure the max is expanded 
too */
-   if (ring_buffer_expanded  type-use_max_tr)
-   ring_buffer_resize(max_tr.buffer, trace_buf_size,
-   RING_BUFFER_ALL_CPUS);
+   if (type-use_max_tr) {
+   /* If we expanded the buffers, make sure the max is 
expanded too */
+   if (ring_buffer_expanded)
+   ring_buffer_resize(max_tr.buffer, 
trace_buf_size,
+  RING_BUFFER_ALL_CPUS);
+   type-allocated_snapshot = true;
+   }
 
/* the test is responsible for initializing and enabling */
pr_info(Testing tracer %s: , type-name);
@@ -885,10 +885,14 @@ int register_tracer(struct tracer *type)
/* Only reset on passing, to avoid touching corrupted buffers

[tip:perf/core] tracing: Add documentation of snapshot utility

[tip-bot for Hiraku Toyooka]

Commit-ID:  c1043fcda1b9e8e5144cfdaee7be262c50dbdead
Gitweb: http://git.kernel.org/tip/c1043fcda1b9e8e5144cfdaee7be262c50dbdead
Author: Hiraku Toyooka hiraku.toyooka...@hitachi.com
AuthorDate: Wed, 26 Dec 2012 11:53:09 +0900
Committer:  Steven Rostedt rost...@goodmis.org
CommitDate: Wed, 30 Jan 2013 11:02:07 -0500

tracing: Add documentation of snapshot utility

This patch adds snapshot description in ftrace documentation.
This description includes what the snapshot is and how to use it.

Link: http://lkml.kernel.org/r/20121226025309.3252.150.stgit@liselsia

Cc: Rob Landley r...@landley.net
Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Signed-off-by: Steven Rostedt rost...@goodmis.org
---
 Documentation/trace/ftrace.txt | 83 ++
 1 file changed, 83 insertions(+)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 6f51fed..53d6a3c 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1842,6 +1842,89 @@ an error.
  # cat buffer_size_kb
 85
 
+Snapshot
+
+CONFIG_TRACER_SNAPSHOT makes a generic snapshot feature
+available to all non latency tracers. (Latency tracers which
+record max latency, such as irqsoff or wakeup, can't use
+this feature, since those are already using the snapshot
+mechanism internally.)
+
+Snapshot preserves a current trace buffer at a particular point
+in time without stopping tracing. Ftrace swaps the current
+buffer with a spare buffer, and tracing continues in the new
+current (=previous spare) buffer.
+
+The following debugfs files in tracing are related to this
+feature:
+
+  snapshot:
+
+   This is used to take a snapshot and to read the output
+   of the snapshot. Echo 1 into this file to allocate a
+   spare buffer and to take a snapshot (swap), then read
+   the snapshot from this file in the same format as
+   trace (described above in the section The File
+   System). Both reads snapshot and tracing are executable
+   in parallel. When the spare buffer is allocated, echoing
+   0 frees it, and echoing else (positive) values clear the
+   snapshot contents.
+   More details are shown in the table below.
+
+   status\input  | 0  | 1  |else|
+   --++++
+   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   --++++
+   allocated |free|swap|   clear|
+   --++++
+
+Here is an example of using the snapshot feature.
+
+ # echo 1  events/sched/enable
+ # echo 1  snapshot
+ # cat snapshot
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 71/71   #P:8
+#
+#  _-= irqs-off
+# / _= need-resched
+#| / _---= hardirq/softirq
+#|| / _--= preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  idle-0 [005] d...  2440.603828: sched_switch: 
prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R == 
next_comm=snapshot-test-2 next_pid=2242 next_prio=120
+   sleep-2242  [005] d...  2440.603846: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2242 prev_prio=120 prev_state=R == 
next_comm=kworker/5:1 next_pid=60 next_prio=120
+[...]
+  idle-0 [002] d...  2440.707230: sched_switch: 
prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R == 
next_comm=snapshot-test-2 next_pid=2229 next_prio=120
+
+ # cat trace
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 77/77   #P:8
+#
+#  _-= irqs-off
+# / _= need-resched
+#| / _---= hardirq/softirq
+#|| / _--= preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  idle-0 [007] d...  2440.707395: sched_switch: 
prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R == 
next_comm=snapshot-test-2 next_pid=2243 next_prio=120
+ snapshot-test-2-2229  [002] d...  2440.707438: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2229 prev_prio=120 prev_state=S == 
next_comm=swapper/2 next_pid=0 next_prio=120
+[...]
+
+
+If you try to use this snapshot feature when current tracer is
+one of the latency tracers, you will get the following results.
+
+ # echo wakeup  current_tracer
+ # echo 1  snapshot
+bash: echo: write error: Device or resource busy
+ # cat snapshot
+cat: snapshot: Device or resource busy
+
 ---
 
 More details can be found in the source code, in the
--
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[tip:perf/core] tracing: Add checks if tr-> buffer is NULL in tracing_reset{_online_cpus}

[tip-bot for Hiraku Toyooka]

Commit-ID:  a54164114b96b4693b42cdb553260eec41ea4393
Gitweb: http://git.kernel.org/tip/a54164114b96b4693b42cdb553260eec41ea4393
Author: Hiraku Toyooka 
AuthorDate: Wed, 19 Dec 2012 16:02:34 +0900
Committer:  Steven Rostedt 
CommitDate: Mon, 21 Jan 2013 13:22:32 -0500

tracing: Add checks if tr->buffer is NULL in tracing_reset{_online_cpus}

max_tr->buffer could be NULL in the tracing_reset{_online_cpus}. In this
case, a NULL pointer dereference happens, so we should return immediately
from these functions.

Note, the current code does not call tracing_reset*() with max_tr when
its buffer is NULL, but future code will. This patch is needed to prevent
the future code from crashing.

Link: http://lkml.kernel.org/r/20121219070234.31200.93863.stgit@liselsia

Signed-off-by: Hiraku Toyooka 
Signed-off-by: Steven Rostedt 
---
 kernel/trace/trace.c | 6 ++
 1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f8b7c62..72b171b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -922,6 +922,9 @@ void tracing_reset(struct trace_array *tr, int cpu)
 {
struct ring_buffer *buffer = tr->buffer;
 
+   if (!buffer)
+   return;
+
ring_buffer_record_disable(buffer);
 
/* Make sure all commits have finished */
@@ -936,6 +939,9 @@ void tracing_reset_online_cpus(struct trace_array *tr)
struct ring_buffer *buffer = tr->buffer;
int cpu;
 
+   if (!buffer)
+   return;
+
ring_buffer_record_disable(buffer);
 
/* Make sure all commits have finished */
--
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Please read the FAQ at  http://www.tux.org/lkml/

[tip:perf/core] tracing: Add checks if tr- buffer is NULL in tracing_reset{_online_cpus}

[tip-bot for Hiraku Toyooka]

Commit-ID:  a54164114b96b4693b42cdb553260eec41ea4393
Gitweb: http://git.kernel.org/tip/a54164114b96b4693b42cdb553260eec41ea4393
Author: Hiraku Toyooka hiraku.toyooka...@hitachi.com
AuthorDate: Wed, 19 Dec 2012 16:02:34 +0900
Committer:  Steven Rostedt rost...@goodmis.org
CommitDate: Mon, 21 Jan 2013 13:22:32 -0500

tracing: Add checks if tr-buffer is NULL in tracing_reset{_online_cpus}

max_tr-buffer could be NULL in the tracing_reset{_online_cpus}. In this
case, a NULL pointer dereference happens, so we should return immediately
from these functions.

Note, the current code does not call tracing_reset*() with max_tr when
its buffer is NULL, but future code will. This patch is needed to prevent
the future code from crashing.

Link: http://lkml.kernel.org/r/20121219070234.31200.93863.stgit@liselsia

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Signed-off-by: Steven Rostedt rost...@goodmis.org
---
 kernel/trace/trace.c | 6 ++
 1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f8b7c62..72b171b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -922,6 +922,9 @@ void tracing_reset(struct trace_array *tr, int cpu)
 {
struct ring_buffer *buffer = tr-buffer;
 
+   if (!buffer)
+   return;
+
ring_buffer_record_disable(buffer);
 
/* Make sure all commits have finished */
@@ -936,6 +939,9 @@ void tracing_reset_online_cpus(struct trace_array *tr)
struct ring_buffer *buffer = tr-buffer;
int cpu;
 
+   if (!buffer)
+   return;
+
ring_buffer_record_disable(buffer);
 
/* Make sure all commits have finished */
--
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Please read the FAQ at  http://www.tux.org/lkml/

[PATCH v4 -tip 3/3] tracing: add description of snapshot to Documentation/trace/ftrace.txt

[Hiraku Toyooka]

This patch adds snapshot description in ftrace documentation.
This description includes what the snapshot is and how to use it.

Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Rob Landley 
Cc: linux-...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 Documentation/trace/ftrace.txt |   83 
 1 file changed, 83 insertions(+)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 6f51fed..53d6a3c 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1842,6 +1842,89 @@ an error.
  # cat buffer_size_kb
 85
 
+Snapshot
+
+CONFIG_TRACER_SNAPSHOT makes a generic snapshot feature
+available to all non latency tracers. (Latency tracers which
+record max latency, such as "irqsoff" or "wakeup", can't use
+this feature, since those are already using the snapshot
+mechanism internally.)
+
+Snapshot preserves a current trace buffer at a particular point
+in time without stopping tracing. Ftrace swaps the current
+buffer with a spare buffer, and tracing continues in the new
+current (=previous spare) buffer.
+
+The following debugfs files in "tracing" are related to this
+feature:
+
+  snapshot:
+
+   This is used to take a snapshot and to read the output
+   of the snapshot. Echo 1 into this file to allocate a
+   spare buffer and to take a snapshot (swap), then read
+   the snapshot from this file in the same format as
+   "trace" (described above in the section "The File
+   System"). Both reads snapshot and tracing are executable
+   in parallel. When the spare buffer is allocated, echoing
+   0 frees it, and echoing else (positive) values clear the
+   snapshot contents.
+   More details are shown in the table below.
+
+   status\input  | 0  | 1  |else|
+   --++++
+   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   --++++
+   allocated |free|swap|   clear|
+   --++++
+
+Here is an example of using the snapshot feature.
+
+ # echo 1 > events/sched/enable
+ # echo 1 > snapshot
+ # cat snapshot
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 71/71   #P:8
+#
+#  _-=> irqs-off
+# / _=> need-resched
+#| / _---=> hardirq/softirq
+#|| / _--=> preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  -0 [005] d...  2440.603828: sched_switch: 
prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2242 next_prio=120
+   sleep-2242  [005] d...  2440.603846: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2242 prev_prio=120 prev_state=R ==> 
next_comm=kworker/5:1 next_pid=60 next_prio=120
+[...]
+  -0 [002] d...  2440.707230: sched_switch: 
prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2229 next_prio=120
+
+ # cat trace
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 77/77   #P:8
+#
+#  _-=> irqs-off
+# / _=> need-resched
+#| / _---=> hardirq/softirq
+#|| / _--=> preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  -0 [007] d...  2440.707395: sched_switch: 
prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2243 next_prio=120
+ snapshot-test-2-2229  [002] d...  2440.707438: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2229 prev_prio=120 prev_state=S ==> 
next_comm=swapper/2 next_pid=0 next_prio=120
+[...]
+
+
+If you try to use this snapshot feature when current tracer is
+one of the latency tracers, you will get the following results.
+
+ # echo wakeup > current_tracer
+ # echo 1 > snapshot
+bash: echo: write error: Device or resource busy
+ # cat snapshot
+cat: snapshot: Device or resource busy
+
 ---
 
 More details can be found in the source code, in the

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[PATCH v4 -tip 2/3] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

Ftrace has a snapshot feature available from kernel space and
latency tracers (e.g. irqsoff) are using it. This patch enables
user applictions to take a snapshot via debugfs.

Add "snapshot" debugfs file in "tracing" directory.

  snapshot:
This is used to take a snapshot and to read the output of the
snapshot.

 # echo 1 > snapshot

This will allocate the spare buffer for snapshot (if it is
not allocated), and take a snapshot.

 # cat snapshot

This will show contents of the snapshot.

 # echo 0 > snapshot

This will free the snapshot if it is allocated.

Any other positive values will clear the snapshot contents if
the snapshot is allocated, or return EINVAL if it is not allocated.

Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Jiri Olsa 
Cc: David Sharp 
Cc: linux-kernel@vger.kernel.org
---
 include/linux/ftrace_event.h |3 +
 kernel/trace/Kconfig |   10 +++
 kernel/trace/trace.c |  134 ++
 kernel/trace/trace.h |1 
 4 files changed, 136 insertions(+), 12 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index a3d4895..9bebadd 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -84,6 +84,9 @@ struct trace_iterator {
longidx;
 
cpumask_var_t   started;
+
+   /* it's true when current open file is snapshot */
+   boolsnapshot;
 };
 
 enum trace_iter_flags {
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 5d89335..82a8ff5 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -250,6 +250,16 @@ config FTRACE_SYSCALLS
help
  Basic tracer to catch the syscall entry and exit events.
 
+config TRACER_SNAPSHOT
+   bool "Create a snapshot trace buffer"
+   select TRACER_MAX_TRACE
+   help
+ Allow tracing users to take snapshot of the current buffer using the
+ ftrace interface, e.g.:
+
+ echo 1 > /sys/kernel/debug/tracing/snapshot
+ cat snapshot
+
 config TRACE_BRANCH_PROFILING
bool
select GENERIC_TRACER
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1787304..9522af0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -709,7 +709,7 @@ update_max_tr(struct trace_array *tr, struct task_struct 
*tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace->use_max_tr) {
+   if (!current_trace->allocated_snapshot) {
WARN_ON_ONCE(1);
return;
}
@@ -739,7 +739,7 @@ update_max_tr_single(struct trace_array *tr, struct 
task_struct *tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace->use_max_tr) {
+   if (!current_trace->allocated_snapshot) {
WARN_ON_ONCE(1);
return;
}
@@ -1964,7 +1964,11 @@ static void *s_start(struct seq_file *m, loff_t *pos)
*iter->trace = *current_trace;
mutex_unlock(_types_lock);
 
-   atomic_inc(_record_cmdline_disabled);
+   if (iter->snapshot && iter->trace->use_max_tr)
+   return ERR_PTR(-EBUSY);
+
+   if (!iter->snapshot)
+   atomic_inc(_record_cmdline_disabled);
 
if (*pos != iter->pos) {
iter->ent = NULL;
@@ -2003,7 +2007,11 @@ static void s_stop(struct seq_file *m, void *p)
 {
struct trace_iterator *iter = m->private;
 
-   atomic_dec(_record_cmdline_disabled);
+   if (iter->snapshot && iter->trace->use_max_tr)
+   return;
+
+   if (!iter->snapshot)
+   atomic_dec(_record_cmdline_disabled);
trace_access_unlock(iter->cpu_file);
trace_event_read_unlock();
 }
@@ -2438,7 +2446,7 @@ static const struct seq_operations tracer_seq_ops = {
 };
 
 static struct trace_iterator *
-__tracing_open(struct inode *inode, struct file *file)
+__tracing_open(struct inode *inode, struct file *file, bool snapshot)
 {
long cpu_file = (long) inode->i_private;
struct trace_iterator *iter;
@@ -2471,10 +2479,11 @@ __tracing_open(struct inode *inode, struct file *file)
if (!zalloc_cpumask_var(>started, GFP_KERNEL))
goto fail;
 
-   if (current_trace && current_trace->print_max)
+   if ((current_trace && current_trace->print_max) || snapshot)
iter->tr = _tr;
else
iter->tr = _trace;
+   iter->snapshot = snapshot;
iter->pos = -1;
mutex_init(>mutex);
iter->cpu_file = cpu_file;
@@ -2491,8 +2500,9 @@ __tracing_open(struct inode *inode, struct file *file)
if (trace_clocks[trace_clock_id].in_ns)
 

[PATCH v4 -tip 1/3] tracing: replace static old_tracer with trace iterator's pointer to the original tracer's name

[Hiraku Toyooka]

Currently the trace buffer read functions use a static variable
"old_tracer" for detecting if the current tracer changes. This
was suitable for a single trace file ("trace"), but to add a
snapshot feature that will use the same function for its file,
a check against a static variable is not sufficient.

To use the output functions for two different files, instead of
storing the current tracer in a static variable, as the trace
iterator descriptor contains a pointer to the original current
tracer's name, that pointer can now be used to check if the
current tracer has changed between different reads of the trace
file.

Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: linux-kernel@vger.kernel.org
---
 kernel/trace/trace.c |   22 +-
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a8ce008..1787304 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1948,18 +1948,20 @@ void tracing_iter_reset(struct trace_iterator *iter, 
int cpu)
 static void *s_start(struct seq_file *m, loff_t *pos)
 {
struct trace_iterator *iter = m->private;
-   static struct tracer *old_tracer;
int cpu_file = iter->cpu_file;
void *p = NULL;
loff_t l = 0;
int cpu;
 
-   /* copy the tracer to avoid using a global lock all around */
+   /*
+* copy the tracer to avoid using a global lock all around.
+* iter->trace is a copy of current_trace, the pointer to the
+* name may be used instead of a strcmp(), as iter->trace->name
+* will point to the same string as current_trace->name.
+*/
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace && iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
-   }
mutex_unlock(_types_lock);
 
atomic_inc(_record_cmdline_disabled);
@@ -3481,7 +3483,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
  size_t cnt, loff_t *ppos)
 {
struct trace_iterator *iter = filp->private_data;
-   static struct tracer *old_tracer;
ssize_t sret;
 
/* return any leftover data */
@@ -3493,10 +3494,8 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace && iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
-   }
mutex_unlock(_types_lock);
 
/*
@@ -3652,7 +3651,6 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
.ops= _pipe_buf_ops,
.spd_release= tracing_spd_release_pipe,
};
-   static struct tracer *old_tracer;
ssize_t ret;
size_t rem;
unsigned int i;
@@ -3662,10 +3660,8 @@ static ssize_t tracing_splice_read_pipe(struct file 
*filp,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace && iter->trace->name != current_trace->name))
*iter->trace = *current_trace;
-   }
mutex_unlock(_types_lock);
 
mutex_lock(>mutex);

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[PATCH v4 -tip 0/3] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

Hi, Steven,

I updated the patch which replaces static variable 'old_tracer'.

v3->v4:
 [1/3] tracing: replace static old_tracer with trace iterator's pointer to the
   original tracer's name
- changed to comparison between pointers instead of strcmp

(v3: https://lkml.org/lkml/2012/12/19/35)

---

Hiraku Toyooka (3):
  tracing: replace static old_tracer with trace iterator's pointer to the 
original tracer's name
  tracing: make a snapshot feature available from userspace
  tracing: add description of snapshot to Documentation/trace/ftrace.txt


 Documentation/trace/ftrace.txt |   83 +
 include/linux/ftrace_event.h   |3 +
 kernel/trace/Kconfig   |   10 +++
 kernel/trace/trace.c   |  156 ++--
 kernel/trace/trace.h   |1 
 5 files changed, 228 insertions(+), 25 deletions(-)

-- 
Hiraku TOYOOKA
Linux Technology Center
Yokohama Research Laboratory
Hitachi Ltd.
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Please read the FAQ at  http://www.tux.org/lkml/

[PATCH v4 -tip 0/3] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

Hi, Steven,

I updated the patch which replaces static variable 'old_tracer'.

v3-v4:
 [1/3] tracing: replace static old_tracer with trace iterator's pointer to the
   original tracer's name
- changed to comparison between pointers instead of strcmp

(v3: https://lkml.org/lkml/2012/12/19/35)

---

Hiraku Toyooka (3):
  tracing: replace static old_tracer with trace iterator's pointer to the 
original tracer's name
  tracing: make a snapshot feature available from userspace
  tracing: add description of snapshot to Documentation/trace/ftrace.txt


 Documentation/trace/ftrace.txt |   83 +
 include/linux/ftrace_event.h   |3 +
 kernel/trace/Kconfig   |   10 +++
 kernel/trace/trace.c   |  156 ++--
 kernel/trace/trace.h   |1 
 5 files changed, 228 insertions(+), 25 deletions(-)

-- 
Hiraku TOYOOKA
Linux Technology Center
Yokohama Research Laboratory
Hitachi Ltd.
--
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Please read the FAQ at  http://www.tux.org/lkml/

[PATCH v4 -tip 1/3] tracing: replace static old_tracer with trace iterator's pointer to the original tracer's name

[Hiraku Toyooka]

Currently the trace buffer read functions use a static variable
old_tracer for detecting if the current tracer changes. This
was suitable for a single trace file (trace), but to add a
snapshot feature that will use the same function for its file,
a check against a static variable is not sufficient.

To use the output functions for two different files, instead of
storing the current tracer in a static variable, as the trace
iterator descriptor contains a pointer to the original current
tracer's name, that pointer can now be used to check if the
current tracer has changed between different reads of the trace
file.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Steven Rostedt rost...@goodmis.org
Cc: Frederic Weisbecker fweis...@gmail.com
Cc: Ingo Molnar mi...@redhat.com
Cc: linux-kernel@vger.kernel.org
---
 kernel/trace/trace.c |   22 +-
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a8ce008..1787304 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1948,18 +1948,20 @@ void tracing_iter_reset(struct trace_iterator *iter, 
int cpu)
 static void *s_start(struct seq_file *m, loff_t *pos)
 {
struct trace_iterator *iter = m-private;
-   static struct tracer *old_tracer;
int cpu_file = iter-cpu_file;
void *p = NULL;
loff_t l = 0;
int cpu;
 
-   /* copy the tracer to avoid using a global lock all around */
+   /*
+* copy the tracer to avoid using a global lock all around.
+* iter-trace is a copy of current_trace, the pointer to the
+* name may be used instead of a strcmp(), as iter-trace-name
+* will point to the same string as current_trace-name.
+*/
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace  iter-trace-name != current_trace-name))
*iter-trace = *current_trace;
-   }
mutex_unlock(trace_types_lock);
 
atomic_inc(trace_record_cmdline_disabled);
@@ -3481,7 +3483,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
  size_t cnt, loff_t *ppos)
 {
struct trace_iterator *iter = filp-private_data;
-   static struct tracer *old_tracer;
ssize_t sret;
 
/* return any leftover data */
@@ -3493,10 +3494,8 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace  iter-trace-name != current_trace-name))
*iter-trace = *current_trace;
-   }
mutex_unlock(trace_types_lock);
 
/*
@@ -3652,7 +3651,6 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
.ops= tracing_pipe_buf_ops,
.spd_release= tracing_spd_release_pipe,
};
-   static struct tracer *old_tracer;
ssize_t ret;
size_t rem;
unsigned int i;
@@ -3662,10 +3660,8 @@ static ssize_t tracing_splice_read_pipe(struct file 
*filp,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace  iter-trace-name != current_trace-name))
*iter-trace = *current_trace;
-   }
mutex_unlock(trace_types_lock);
 
mutex_lock(iter-mutex);

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Please read the FAQ at  http://www.tux.org/lkml/

[PATCH v4 -tip 2/3] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

Ftrace has a snapshot feature available from kernel space and
latency tracers (e.g. irqsoff) are using it. This patch enables
user applictions to take a snapshot via debugfs.

Add snapshot debugfs file in tracing directory.

  snapshot:
This is used to take a snapshot and to read the output of the
snapshot.

 # echo 1  snapshot

This will allocate the spare buffer for snapshot (if it is
not allocated), and take a snapshot.

 # cat snapshot

This will show contents of the snapshot.

 # echo 0  snapshot

This will free the snapshot if it is allocated.

Any other positive values will clear the snapshot contents if
the snapshot is allocated, or return EINVAL if it is not allocated.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Steven Rostedt rost...@goodmis.org
Cc: Frederic Weisbecker fweis...@gmail.com
Cc: Ingo Molnar mi...@redhat.com
Cc: Jiri Olsa jo...@redhat.com
Cc: David Sharp dhsh...@google.com
Cc: linux-kernel@vger.kernel.org
---
 include/linux/ftrace_event.h |3 +
 kernel/trace/Kconfig |   10 +++
 kernel/trace/trace.c |  134 ++
 kernel/trace/trace.h |1 
 4 files changed, 136 insertions(+), 12 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index a3d4895..9bebadd 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -84,6 +84,9 @@ struct trace_iterator {
longidx;
 
cpumask_var_t   started;
+
+   /* it's true when current open file is snapshot */
+   boolsnapshot;
 };
 
 enum trace_iter_flags {
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 5d89335..82a8ff5 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -250,6 +250,16 @@ config FTRACE_SYSCALLS
help
  Basic tracer to catch the syscall entry and exit events.
 
+config TRACER_SNAPSHOT
+   bool Create a snapshot trace buffer
+   select TRACER_MAX_TRACE
+   help
+ Allow tracing users to take snapshot of the current buffer using the
+ ftrace interface, e.g.:
+
+ echo 1  /sys/kernel/debug/tracing/snapshot
+ cat snapshot
+
 config TRACE_BRANCH_PROFILING
bool
select GENERIC_TRACER
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1787304..9522af0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -709,7 +709,7 @@ update_max_tr(struct trace_array *tr, struct task_struct 
*tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace-use_max_tr) {
+   if (!current_trace-allocated_snapshot) {
WARN_ON_ONCE(1);
return;
}
@@ -739,7 +739,7 @@ update_max_tr_single(struct trace_array *tr, struct 
task_struct *tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace-use_max_tr) {
+   if (!current_trace-allocated_snapshot) {
WARN_ON_ONCE(1);
return;
}
@@ -1964,7 +1964,11 @@ static void *s_start(struct seq_file *m, loff_t *pos)
*iter-trace = *current_trace;
mutex_unlock(trace_types_lock);
 
-   atomic_inc(trace_record_cmdline_disabled);
+   if (iter-snapshot  iter-trace-use_max_tr)
+   return ERR_PTR(-EBUSY);
+
+   if (!iter-snapshot)
+   atomic_inc(trace_record_cmdline_disabled);
 
if (*pos != iter-pos) {
iter-ent = NULL;
@@ -2003,7 +2007,11 @@ static void s_stop(struct seq_file *m, void *p)
 {
struct trace_iterator *iter = m-private;
 
-   atomic_dec(trace_record_cmdline_disabled);
+   if (iter-snapshot  iter-trace-use_max_tr)
+   return;
+
+   if (!iter-snapshot)
+   atomic_dec(trace_record_cmdline_disabled);
trace_access_unlock(iter-cpu_file);
trace_event_read_unlock();
 }
@@ -2438,7 +2446,7 @@ static const struct seq_operations tracer_seq_ops = {
 };
 
 static struct trace_iterator *
-__tracing_open(struct inode *inode, struct file *file)
+__tracing_open(struct inode *inode, struct file *file, bool snapshot)
 {
long cpu_file = (long) inode-i_private;
struct trace_iterator *iter;
@@ -2471,10 +2479,11 @@ __tracing_open(struct inode *inode, struct file *file)
if (!zalloc_cpumask_var(iter-started, GFP_KERNEL))
goto fail;
 
-   if (current_trace  current_trace-print_max)
+   if ((current_trace  current_trace-print_max) || snapshot)
iter-tr = max_tr;
else
iter-tr = global_trace;
+   iter-snapshot = snapshot;
iter-pos = -1;
mutex_init(iter-mutex);
iter-cpu_file = cpu_file;
@@ -2491,8 +2500,9 @@ __tracing_open(struct inode *inode, struct file *file)
if (trace_clocks[trace_clock_id].in_ns)
iter-iter_flags

[PATCH v4 -tip 3/3] tracing: add description of snapshot to Documentation/trace/ftrace.txt

[Hiraku Toyooka]

This patch adds snapshot description in ftrace documentation.
This description includes what the snapshot is and how to use it.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Steven Rostedt rost...@goodmis.org
Cc: Frederic Weisbecker fweis...@gmail.com
Cc: Ingo Molnar mi...@redhat.com
Cc: Rob Landley r...@landley.net
Cc: linux-...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 Documentation/trace/ftrace.txt |   83 
 1 file changed, 83 insertions(+)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 6f51fed..53d6a3c 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1842,6 +1842,89 @@ an error.
  # cat buffer_size_kb
 85
 
+Snapshot
+
+CONFIG_TRACER_SNAPSHOT makes a generic snapshot feature
+available to all non latency tracers. (Latency tracers which
+record max latency, such as irqsoff or wakeup, can't use
+this feature, since those are already using the snapshot
+mechanism internally.)
+
+Snapshot preserves a current trace buffer at a particular point
+in time without stopping tracing. Ftrace swaps the current
+buffer with a spare buffer, and tracing continues in the new
+current (=previous spare) buffer.
+
+The following debugfs files in tracing are related to this
+feature:
+
+  snapshot:
+
+   This is used to take a snapshot and to read the output
+   of the snapshot. Echo 1 into this file to allocate a
+   spare buffer and to take a snapshot (swap), then read
+   the snapshot from this file in the same format as
+   trace (described above in the section The File
+   System). Both reads snapshot and tracing are executable
+   in parallel. When the spare buffer is allocated, echoing
+   0 frees it, and echoing else (positive) values clear the
+   snapshot contents.
+   More details are shown in the table below.
+
+   status\input  | 0  | 1  |else|
+   --++++
+   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   --++++
+   allocated |free|swap|   clear|
+   --++++
+
+Here is an example of using the snapshot feature.
+
+ # echo 1  events/sched/enable
+ # echo 1  snapshot
+ # cat snapshot
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 71/71   #P:8
+#
+#  _-= irqs-off
+# / _= need-resched
+#| / _---= hardirq/softirq
+#|| / _--= preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  idle-0 [005] d...  2440.603828: sched_switch: 
prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R == 
next_comm=snapshot-test-2 next_pid=2242 next_prio=120
+   sleep-2242  [005] d...  2440.603846: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2242 prev_prio=120 prev_state=R == 
next_comm=kworker/5:1 next_pid=60 next_prio=120
+[...]
+  idle-0 [002] d...  2440.707230: sched_switch: 
prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R == 
next_comm=snapshot-test-2 next_pid=2229 next_prio=120
+
+ # cat trace
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 77/77   #P:8
+#
+#  _-= irqs-off
+# / _= need-resched
+#| / _---= hardirq/softirq
+#|| / _--= preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  idle-0 [007] d...  2440.707395: sched_switch: 
prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R == 
next_comm=snapshot-test-2 next_pid=2243 next_prio=120
+ snapshot-test-2-2229  [002] d...  2440.707438: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2229 prev_prio=120 prev_state=S == 
next_comm=swapper/2 next_pid=0 next_prio=120
+[...]
+
+
+If you try to use this snapshot feature when current tracer is
+one of the latency tracers, you will get the following results.
+
+ # echo wakeup  current_tracer
+ # echo 1  snapshot
+bash: echo: write error: Device or resource busy
+ # cat snapshot
+cat: snapshot: Device or resource busy
+
 ---
 
 More details can be found in the source code, in the

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Re: [PATCH v3 -tip 2/4] tracing: replace static old_tracer with strcmp

[Hiraku Toyooka]

Hi,

(12/21/2012 12:04 PM), Steven Rostedt wrote:

On Wed, 2012-12-19 at 16:02 +0900, Hiraku Toyooka wrote:

Currently, read functions for trace buffer use static "old_tracer"
for detecting changes of current tracer. This is because we can
assume that these functions are used from only one file ("trace").

But we are adding snapshot feature for ftrace, then those functions
are called from two files. So we remove all static "old_tracer", and
replace those with string comparison between current and previous
tracers.


I reworded what you wrote:



Thank you very much.


---
Currently the trace buffer read functions use a static variable
"old_tracer" for detecting if the current tracer changes. This was
suitable for a single trace file ("trace"), but to add a snapshot
feature that will use the same function for its file, a check against
a static variable is not sufficient.

To use the output functions for two different files, instead of storing
the current tracer in a static variable, as the trace iterator
descriptor
contains a pointer to the original current tracer's name, that pointer
can now be used to check if the current tracer has changed between
different reads of the trace file.
---

And I also realized a more efficient approach.



Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: linux-kernel@vger.kernel.org
---
  kernel/trace/trace.c |   18 ++
  1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a8ce008..8d05a44 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1948,7 +1948,6 @@ void tracing_iter_reset(struct trace_iterator *iter, int 
cpu)
  static void *s_start(struct seq_file *m, loff_t *pos)
  {
struct trace_iterator *iter = m->private;
-   static struct tracer *old_tracer;
int cpu_file = iter->cpu_file;
void *p = NULL;
loff_t l = 0;
@@ -1956,10 +1955,9 @@ static void *s_start(struct seq_file *m, loff_t *pos)

/* copy the tracer to avoid using a global lock all around */
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace &&
+strcmp(iter->trace->name, current_trace->name) != 0))
*iter->trace = *current_trace;


As iter->trace is a copy of current_trace, it points to everything that
the current_trace pointed to. As the current_trace->name is a pointer to
a const char string that never changes, we don't need to do the strcmp()
you can simply do a direct comparison:

if (unlikely(current_trace && iter->trace->name != 
current_trace->name)) {



Yes. I'll update my patch to use this efficient way.


I would add a comment about that too:
/*
 * iter->trace is a copy of current_trace, the pointer to the
 * name may be used instead of a strcmp(), as iter->trace->name
 * will point to the same string as current_trace->name.
 */


OK. I'll include this comment in my patch.


Thanks,
Hiraku Toyooka

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Re: [PATCH v3 -tip 2/4] tracing: replace static old_tracer with strcmp

[Hiraku Toyooka]

Hi,

(12/21/2012 12:04 PM), Steven Rostedt wrote:

On Wed, 2012-12-19 at 16:02 +0900, Hiraku Toyooka wrote:

Currently, read functions for trace buffer use static old_tracer
for detecting changes of current tracer. This is because we can
assume that these functions are used from only one file (trace).

But we are adding snapshot feature for ftrace, then those functions
are called from two files. So we remove all static old_tracer, and
replace those with string comparison between current and previous
tracers.


I reworded what you wrote:



Thank you very much.


---
Currently the trace buffer read functions use a static variable
old_tracer for detecting if the current tracer changes. This was
suitable for a single trace file (trace), but to add a snapshot
feature that will use the same function for its file, a check against
a static variable is not sufficient.

To use the output functions for two different files, instead of storing
the current tracer in a static variable, as the trace iterator
descriptor
contains a pointer to the original current tracer's name, that pointer
can now be used to check if the current tracer has changed between
different reads of the trace file.
---

And I also realized a more efficient approach.



Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Steven Rostedt rost...@goodmis.org
Cc: Frederic Weisbecker fweis...@gmail.com
Cc: Ingo Molnar mi...@redhat.com
Cc: linux-kernel@vger.kernel.org
---
  kernel/trace/trace.c |   18 ++
  1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a8ce008..8d05a44 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1948,7 +1948,6 @@ void tracing_iter_reset(struct trace_iterator *iter, int 
cpu)
  static void *s_start(struct seq_file *m, loff_t *pos)
  {
struct trace_iterator *iter = m-private;
-   static struct tracer *old_tracer;
int cpu_file = iter-cpu_file;
void *p = NULL;
loff_t l = 0;
@@ -1956,10 +1955,9 @@ static void *s_start(struct seq_file *m, loff_t *pos)

/* copy the tracer to avoid using a global lock all around */
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace 
+strcmp(iter-trace-name, current_trace-name) != 0))
*iter-trace = *current_trace;


As iter-trace is a copy of current_trace, it points to everything that
the current_trace pointed to. As the current_trace-name is a pointer to
a const char string that never changes, we don't need to do the strcmp()
you can simply do a direct comparison:

if (unlikely(current_trace  iter-trace-name != 
current_trace-name)) {



Yes. I'll update my patch to use this efficient way.


I would add a comment about that too:
/*
 * iter-trace is a copy of current_trace, the pointer to the
 * name may be used instead of a strcmp(), as iter-trace-name
 * will point to the same string as current_trace-name.
 */


OK. I'll include this comment in my patch.


Thanks,
Hiraku Toyooka

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Please read the FAQ at  http://www.tux.org/lkml/

[PATCH v3 -tip 4/4] tracing: add description of snapshot to Documentation/trace/ftrace.txt

[Hiraku Toyooka]

This patch adds snapshot description in ftrace documentation.
This description includes what the snapshot is and how to use it.

Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Rob Landley 
Cc: linux-...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 Documentation/trace/ftrace.txt |   83 
 1 file changed, 83 insertions(+)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 6f51fed..53d6a3c 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1842,6 +1842,89 @@ an error.
  # cat buffer_size_kb
 85
 
+Snapshot
+
+CONFIG_TRACER_SNAPSHOT makes a generic snapshot feature
+available to all non latency tracers. (Latency tracers which
+record max latency, such as "irqsoff" or "wakeup", can't use
+this feature, since those are already using the snapshot
+mechanism internally.)
+
+Snapshot preserves a current trace buffer at a particular point
+in time without stopping tracing. Ftrace swaps the current
+buffer with a spare buffer, and tracing continues in the new
+current (=previous spare) buffer.
+
+The following debugfs files in "tracing" are related to this
+feature:
+
+  snapshot:
+
+   This is used to take a snapshot and to read the output
+   of the snapshot. Echo 1 into this file to allocate a
+   spare buffer and to take a snapshot (swap), then read
+   the snapshot from this file in the same format as
+   "trace" (described above in the section "The File
+   System"). Both reads snapshot and tracing are executable
+   in parallel. When the spare buffer is allocated, echoing
+   0 frees it, and echoing else (positive) values clear the
+   snapshot contents.
+   More details are shown in the table below.
+
+   status\input  | 0  | 1  |else|
+   --++++
+   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   --++++
+   allocated |free|swap|   clear|
+   --++++
+
+Here is an example of using the snapshot feature.
+
+ # echo 1 > events/sched/enable
+ # echo 1 > snapshot
+ # cat snapshot
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 71/71   #P:8
+#
+#  _-=> irqs-off
+# / _=> need-resched
+#| / _---=> hardirq/softirq
+#|| / _--=> preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  -0 [005] d...  2440.603828: sched_switch: 
prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2242 next_prio=120
+   sleep-2242  [005] d...  2440.603846: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2242 prev_prio=120 prev_state=R ==> 
next_comm=kworker/5:1 next_pid=60 next_prio=120
+[...]
+  -0 [002] d...  2440.707230: sched_switch: 
prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2229 next_prio=120
+
+ # cat trace
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 77/77   #P:8
+#
+#  _-=> irqs-off
+# / _=> need-resched
+#| / _---=> hardirq/softirq
+#|| / _--=> preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  -0 [007] d...  2440.707395: sched_switch: 
prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2243 next_prio=120
+ snapshot-test-2-2229  [002] d...  2440.707438: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2229 prev_prio=120 prev_state=S ==> 
next_comm=swapper/2 next_pid=0 next_prio=120
+[...]
+
+
+If you try to use this snapshot feature when current tracer is
+one of the latency tracers, you will get the following results.
+
+ # echo wakeup > current_tracer
+ # echo 1 > snapshot
+bash: echo: write error: Device or resource busy
+ # cat snapshot
+cat: snapshot: Device or resource busy
+
 ---
 
 More details can be found in the source code, in the

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Please read the FAQ at  http://www.tux.org/lkml/

[PATCH v3 -tip 2/4] tracing: replace static old_tracer with strcmp

[Hiraku Toyooka]

Currently, read functions for trace buffer use static "old_tracer"
for detecting changes of current tracer. This is because we can
assume that these functions are used from only one file ("trace").

But we are adding snapshot feature for ftrace, then those functions
are called from two files. So we remove all static "old_tracer", and
replace those with string comparison between current and previous
tracers.

Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: linux-kernel@vger.kernel.org
---
 kernel/trace/trace.c |   18 ++
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a8ce008..8d05a44 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1948,7 +1948,6 @@ void tracing_iter_reset(struct trace_iterator *iter, int 
cpu)
 static void *s_start(struct seq_file *m, loff_t *pos)
 {
struct trace_iterator *iter = m->private;
-   static struct tracer *old_tracer;
int cpu_file = iter->cpu_file;
void *p = NULL;
loff_t l = 0;
@@ -1956,10 +1955,9 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace &&
+strcmp(iter->trace->name, current_trace->name) != 0))
*iter->trace = *current_trace;
-   }
mutex_unlock(_types_lock);
 
atomic_inc(_record_cmdline_disabled);
@@ -3481,7 +3479,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
  size_t cnt, loff_t *ppos)
 {
struct trace_iterator *iter = filp->private_data;
-   static struct tracer *old_tracer;
ssize_t sret;
 
/* return any leftover data */
@@ -3493,10 +3490,9 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace &&
+strcmp(iter->trace->name, current_trace->name) != 0))
*iter->trace = *current_trace;
-   }
mutex_unlock(_types_lock);
 
/*
@@ -3652,7 +3648,6 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
.ops= _pipe_buf_ops,
.spd_release= tracing_spd_release_pipe,
};
-   static struct tracer *old_tracer;
ssize_t ret;
size_t rem;
unsigned int i;
@@ -3662,10 +3657,9 @@ static ssize_t tracing_splice_read_pipe(struct file 
*filp,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(_types_lock);
-   if (unlikely(old_tracer != current_trace && current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace &&
+strcmp(iter->trace->name, current_trace->name) != 0))
*iter->trace = *current_trace;
-   }
mutex_unlock(_types_lock);
 
mutex_lock(>mutex);

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[PATCH v3 -tip 3/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

Ftrace has a snapshot feature available from kernel space and
latency tracers (e.g. irqsoff) are using it. This patch enables
user applictions to take a snapshot via debugfs.

Add "snapshot" debugfs file in "tracing" directory.

  snapshot:
This is used to take a snapshot and to read the output of the
snapshot.

 # echo 1 > snapshot

This will allocate the spare buffer for snapshot (if it is
not allocated), and take a snapshot.

 # cat snapshot

This will show contents of the snapshot.

 # echo 0 > snapshot

This will free the snapshot if it is allocated.

Any other positive values will clear the snapshot contents if
the snapshot is allocated, or return EINVAL if it is not allocated.

Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Jiri Olsa 
Cc: David Sharp 
Cc: linux-kernel@vger.kernel.org
---
 include/linux/ftrace_event.h |3 +
 kernel/trace/Kconfig |   10 +++
 kernel/trace/trace.c |  134 ++
 kernel/trace/trace.h |1 
 4 files changed, 136 insertions(+), 12 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index a3d4895..9bebadd 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -84,6 +84,9 @@ struct trace_iterator {
longidx;
 
cpumask_var_t   started;
+
+   /* it's true when current open file is snapshot */
+   boolsnapshot;
 };
 
 enum trace_iter_flags {
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 5d89335..82a8ff5 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -250,6 +250,16 @@ config FTRACE_SYSCALLS
help
  Basic tracer to catch the syscall entry and exit events.
 
+config TRACER_SNAPSHOT
+   bool "Create a snapshot trace buffer"
+   select TRACER_MAX_TRACE
+   help
+ Allow tracing users to take snapshot of the current buffer using the
+ ftrace interface, e.g.:
+
+ echo 1 > /sys/kernel/debug/tracing/snapshot
+ cat snapshot
+
 config TRACE_BRANCH_PROFILING
bool
select GENERIC_TRACER
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8d05a44..0e5abce 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -709,7 +709,7 @@ update_max_tr(struct trace_array *tr, struct task_struct 
*tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace->use_max_tr) {
+   if (!current_trace->allocated_snapshot) {
WARN_ON_ONCE(1);
return;
}
@@ -739,7 +739,7 @@ update_max_tr_single(struct trace_array *tr, struct 
task_struct *tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace->use_max_tr) {
+   if (!current_trace->allocated_snapshot) {
WARN_ON_ONCE(1);
return;
}
@@ -1960,7 +1960,11 @@ static void *s_start(struct seq_file *m, loff_t *pos)
*iter->trace = *current_trace;
mutex_unlock(_types_lock);
 
-   atomic_inc(_record_cmdline_disabled);
+   if (iter->snapshot && iter->trace->use_max_tr)
+   return ERR_PTR(-EBUSY);
+
+   if (!iter->snapshot)
+   atomic_inc(_record_cmdline_disabled);
 
if (*pos != iter->pos) {
iter->ent = NULL;
@@ -1999,7 +2003,11 @@ static void s_stop(struct seq_file *m, void *p)
 {
struct trace_iterator *iter = m->private;
 
-   atomic_dec(_record_cmdline_disabled);
+   if (iter->snapshot && iter->trace->use_max_tr)
+   return;
+
+   if (!iter->snapshot)
+   atomic_dec(_record_cmdline_disabled);
trace_access_unlock(iter->cpu_file);
trace_event_read_unlock();
 }
@@ -2434,7 +2442,7 @@ static const struct seq_operations tracer_seq_ops = {
 };
 
 static struct trace_iterator *
-__tracing_open(struct inode *inode, struct file *file)
+__tracing_open(struct inode *inode, struct file *file, bool snapshot)
 {
long cpu_file = (long) inode->i_private;
struct trace_iterator *iter;
@@ -2467,10 +2475,11 @@ __tracing_open(struct inode *inode, struct file *file)
if (!zalloc_cpumask_var(>started, GFP_KERNEL))
goto fail;
 
-   if (current_trace && current_trace->print_max)
+   if ((current_trace && current_trace->print_max) || snapshot)
iter->tr = _tr;
else
iter->tr = _trace;
+   iter->snapshot = snapshot;
iter->pos = -1;
mutex_init(>mutex);
iter->cpu_file = cpu_file;
@@ -2487,8 +2496,9 @@ __tracing_open(struct inode *inode, struct file *file)
if (trace_clocks[trace_clock_id].in_ns)
 

[PATCH v3 -tip 1/4] tracing: add checks if tr->buffer is NULL in tracing_reset{_online_cpus}

[Hiraku Toyooka]

max_tr->buffer could be NULL in the tracing_reset{_online_cpus}. In this
case, a NULL pointer dereference happens, so we should return immediately
from these functions.

Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: linux-kernel@vger.kernel.org
---
 kernel/trace/trace.c |6 ++
 1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c705c7a..a8ce008 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -922,6 +922,9 @@ void tracing_reset(struct trace_array *tr, int cpu)
 {
struct ring_buffer *buffer = tr->buffer;
 
+   if (!buffer)
+   return;
+
ring_buffer_record_disable(buffer);
 
/* Make sure all commits have finished */
@@ -936,6 +939,9 @@ void tracing_reset_online_cpus(struct trace_array *tr)
struct ring_buffer *buffer = tr->buffer;
int cpu;
 
+   if (!buffer)
+   return;
+
ring_buffer_record_disable(buffer);
 
/* Make sure all commits have finished */

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[PATCH v3 -tip 0/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

Hi, Steven,

Thank you for your review.
I applied your review comments.

These patches depend on the next patch.

tracing: Add a resize function to make one buffer equivalent to another buffer
http://lkml.kernel.org/r/20121017025616.2627.91226.stgit@falsita

v2->v3:
 [1/4] tracing: add checks if tr->buffer is NULL in tracing_reset{_online_cpus}
- (new patch)
 [2/4] tracing: replace static old_tracer with strcmp
- (new patch)
 [3/4] tracing: make a snapshot feature available from userspace
- changed snapshot file I/F (removed "snapshot_allocate")
- changed CONFIG_TRACER_SNAPSHOT's location and description
- changed an integer flag of __tracing_open() to bool
- switched to use seq_read() directly for reading snapshot
 [4/4] tracing: add description of snapshot to Documentation/trace/ftrace.txt
- updated documentation of the snapshot

ToDo:
 - adding "trace_snapshot" kernel parameter to allocate spare buffer on boot. 

(v1: https://lkml.org/lkml/2012/10/2/67)
(v2: https://lkml.org/lkml/2012/10/16/585)

---

Hiraku Toyooka (4):
  tracing: add checks if tr->buffer is NULL in tracing_reset{_online_cpus}
  tracing: replace static old_tracer with strcmp
  tracing: make a snapshot feature available from userspace
  tracing: add description of snapshot to Documentation/trace/ftrace.txt


 Documentation/trace/ftrace.txt |   83 +
 include/linux/ftrace_event.h   |3 +
 kernel/trace/Kconfig   |   10 +++
 kernel/trace/trace.c   |  158 ++--
 kernel/trace/trace.h   |1 
 5 files changed, 231 insertions(+), 24 deletions(-)

-- 
Hiraku TOYOOKA
Linux Technology Center
Yokohama Research Laboratory
Hitachi Ltd.
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[PATCH v3 -tip 0/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

Hi, Steven,

Thank you for your review.
I applied your review comments.

These patches depend on the next patch.

tracing: Add a resize function to make one buffer equivalent to another buffer
http://lkml.kernel.org/r/20121017025616.2627.91226.stgit@falsita

v2-v3:
 [1/4] tracing: add checks if tr-buffer is NULL in tracing_reset{_online_cpus}
- (new patch)
 [2/4] tracing: replace static old_tracer with strcmp
- (new patch)
 [3/4] tracing: make a snapshot feature available from userspace
- changed snapshot file I/F (removed snapshot_allocate)
- changed CONFIG_TRACER_SNAPSHOT's location and description
- changed an integer flag of __tracing_open() to bool
- switched to use seq_read() directly for reading snapshot
 [4/4] tracing: add description of snapshot to Documentation/trace/ftrace.txt
- updated documentation of the snapshot

ToDo:
 - adding trace_snapshot kernel parameter to allocate spare buffer on boot. 

(v1: https://lkml.org/lkml/2012/10/2/67)
(v2: https://lkml.org/lkml/2012/10/16/585)

---

Hiraku Toyooka (4):
  tracing: add checks if tr-buffer is NULL in tracing_reset{_online_cpus}
  tracing: replace static old_tracer with strcmp
  tracing: make a snapshot feature available from userspace
  tracing: add description of snapshot to Documentation/trace/ftrace.txt


 Documentation/trace/ftrace.txt |   83 +
 include/linux/ftrace_event.h   |3 +
 kernel/trace/Kconfig   |   10 +++
 kernel/trace/trace.c   |  158 ++--
 kernel/trace/trace.h   |1 
 5 files changed, 231 insertions(+), 24 deletions(-)

-- 
Hiraku TOYOOKA
Linux Technology Center
Yokohama Research Laboratory
Hitachi Ltd.
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[PATCH v3 -tip 1/4] tracing: add checks if tr-buffer is NULL in tracing_reset{_online_cpus}

[Hiraku Toyooka]

max_tr-buffer could be NULL in the tracing_reset{_online_cpus}. In this
case, a NULL pointer dereference happens, so we should return immediately
from these functions.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Steven Rostedt rost...@goodmis.org
Cc: Frederic Weisbecker fweis...@gmail.com
Cc: Ingo Molnar mi...@redhat.com
Cc: linux-kernel@vger.kernel.org
---
 kernel/trace/trace.c |6 ++
 1 file changed, 6 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c705c7a..a8ce008 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -922,6 +922,9 @@ void tracing_reset(struct trace_array *tr, int cpu)
 {
struct ring_buffer *buffer = tr-buffer;
 
+   if (!buffer)
+   return;
+
ring_buffer_record_disable(buffer);
 
/* Make sure all commits have finished */
@@ -936,6 +939,9 @@ void tracing_reset_online_cpus(struct trace_array *tr)
struct ring_buffer *buffer = tr-buffer;
int cpu;
 
+   if (!buffer)
+   return;
+
ring_buffer_record_disable(buffer);
 
/* Make sure all commits have finished */

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[PATCH v3 -tip 2/4] tracing: replace static old_tracer with strcmp

[Hiraku Toyooka]

Currently, read functions for trace buffer use static old_tracer
for detecting changes of current tracer. This is because we can
assume that these functions are used from only one file (trace).

But we are adding snapshot feature for ftrace, then those functions
are called from two files. So we remove all static old_tracer, and
replace those with string comparison between current and previous
tracers.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Steven Rostedt rost...@goodmis.org
Cc: Frederic Weisbecker fweis...@gmail.com
Cc: Ingo Molnar mi...@redhat.com
Cc: linux-kernel@vger.kernel.org
---
 kernel/trace/trace.c |   18 ++
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a8ce008..8d05a44 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1948,7 +1948,6 @@ void tracing_iter_reset(struct trace_iterator *iter, int 
cpu)
 static void *s_start(struct seq_file *m, loff_t *pos)
 {
struct trace_iterator *iter = m-private;
-   static struct tracer *old_tracer;
int cpu_file = iter-cpu_file;
void *p = NULL;
loff_t l = 0;
@@ -1956,10 +1955,9 @@ static void *s_start(struct seq_file *m, loff_t *pos)
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace 
+strcmp(iter-trace-name, current_trace-name) != 0))
*iter-trace = *current_trace;
-   }
mutex_unlock(trace_types_lock);
 
atomic_inc(trace_record_cmdline_disabled);
@@ -3481,7 +3479,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
  size_t cnt, loff_t *ppos)
 {
struct trace_iterator *iter = filp-private_data;
-   static struct tracer *old_tracer;
ssize_t sret;
 
/* return any leftover data */
@@ -3493,10 +3490,9 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace 
+strcmp(iter-trace-name, current_trace-name) != 0))
*iter-trace = *current_trace;
-   }
mutex_unlock(trace_types_lock);
 
/*
@@ -3652,7 +3648,6 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
.ops= tracing_pipe_buf_ops,
.spd_release= tracing_spd_release_pipe,
};
-   static struct tracer *old_tracer;
ssize_t ret;
size_t rem;
unsigned int i;
@@ -3662,10 +3657,9 @@ static ssize_t tracing_splice_read_pipe(struct file 
*filp,
 
/* copy the tracer to avoid using a global lock all around */
mutex_lock(trace_types_lock);
-   if (unlikely(old_tracer != current_trace  current_trace)) {
-   old_tracer = current_trace;
+   if (unlikely(current_trace 
+strcmp(iter-trace-name, current_trace-name) != 0))
*iter-trace = *current_trace;
-   }
mutex_unlock(trace_types_lock);
 
mutex_lock(iter-mutex);

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[PATCH v3 -tip 3/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

Ftrace has a snapshot feature available from kernel space and
latency tracers (e.g. irqsoff) are using it. This patch enables
user applictions to take a snapshot via debugfs.

Add snapshot debugfs file in tracing directory.

  snapshot:
This is used to take a snapshot and to read the output of the
snapshot.

 # echo 1  snapshot

This will allocate the spare buffer for snapshot (if it is
not allocated), and take a snapshot.

 # cat snapshot

This will show contents of the snapshot.

 # echo 0  snapshot

This will free the snapshot if it is allocated.

Any other positive values will clear the snapshot contents if
the snapshot is allocated, or return EINVAL if it is not allocated.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Steven Rostedt rost...@goodmis.org
Cc: Frederic Weisbecker fweis...@gmail.com
Cc: Ingo Molnar mi...@redhat.com
Cc: Jiri Olsa jo...@redhat.com
Cc: David Sharp dhsh...@google.com
Cc: linux-kernel@vger.kernel.org
---
 include/linux/ftrace_event.h |3 +
 kernel/trace/Kconfig |   10 +++
 kernel/trace/trace.c |  134 ++
 kernel/trace/trace.h |1 
 4 files changed, 136 insertions(+), 12 deletions(-)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index a3d4895..9bebadd 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -84,6 +84,9 @@ struct trace_iterator {
longidx;
 
cpumask_var_t   started;
+
+   /* it's true when current open file is snapshot */
+   boolsnapshot;
 };
 
 enum trace_iter_flags {
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 5d89335..82a8ff5 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -250,6 +250,16 @@ config FTRACE_SYSCALLS
help
  Basic tracer to catch the syscall entry and exit events.
 
+config TRACER_SNAPSHOT
+   bool Create a snapshot trace buffer
+   select TRACER_MAX_TRACE
+   help
+ Allow tracing users to take snapshot of the current buffer using the
+ ftrace interface, e.g.:
+
+ echo 1  /sys/kernel/debug/tracing/snapshot
+ cat snapshot
+
 config TRACE_BRANCH_PROFILING
bool
select GENERIC_TRACER
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8d05a44..0e5abce 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -709,7 +709,7 @@ update_max_tr(struct trace_array *tr, struct task_struct 
*tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace-use_max_tr) {
+   if (!current_trace-allocated_snapshot) {
WARN_ON_ONCE(1);
return;
}
@@ -739,7 +739,7 @@ update_max_tr_single(struct trace_array *tr, struct 
task_struct *tsk, int cpu)
return;
 
WARN_ON_ONCE(!irqs_disabled());
-   if (!current_trace-use_max_tr) {
+   if (!current_trace-allocated_snapshot) {
WARN_ON_ONCE(1);
return;
}
@@ -1960,7 +1960,11 @@ static void *s_start(struct seq_file *m, loff_t *pos)
*iter-trace = *current_trace;
mutex_unlock(trace_types_lock);
 
-   atomic_inc(trace_record_cmdline_disabled);
+   if (iter-snapshot  iter-trace-use_max_tr)
+   return ERR_PTR(-EBUSY);
+
+   if (!iter-snapshot)
+   atomic_inc(trace_record_cmdline_disabled);
 
if (*pos != iter-pos) {
iter-ent = NULL;
@@ -1999,7 +2003,11 @@ static void s_stop(struct seq_file *m, void *p)
 {
struct trace_iterator *iter = m-private;
 
-   atomic_dec(trace_record_cmdline_disabled);
+   if (iter-snapshot  iter-trace-use_max_tr)
+   return;
+
+   if (!iter-snapshot)
+   atomic_dec(trace_record_cmdline_disabled);
trace_access_unlock(iter-cpu_file);
trace_event_read_unlock();
 }
@@ -2434,7 +2442,7 @@ static const struct seq_operations tracer_seq_ops = {
 };
 
 static struct trace_iterator *
-__tracing_open(struct inode *inode, struct file *file)
+__tracing_open(struct inode *inode, struct file *file, bool snapshot)
 {
long cpu_file = (long) inode-i_private;
struct trace_iterator *iter;
@@ -2467,10 +2475,11 @@ __tracing_open(struct inode *inode, struct file *file)
if (!zalloc_cpumask_var(iter-started, GFP_KERNEL))
goto fail;
 
-   if (current_trace  current_trace-print_max)
+   if ((current_trace  current_trace-print_max) || snapshot)
iter-tr = max_tr;
else
iter-tr = global_trace;
+   iter-snapshot = snapshot;
iter-pos = -1;
mutex_init(iter-mutex);
iter-cpu_file = cpu_file;
@@ -2487,8 +2496,9 @@ __tracing_open(struct inode *inode, struct file *file)
if (trace_clocks[trace_clock_id].in_ns)
iter-iter_flags

[PATCH v3 -tip 4/4] tracing: add description of snapshot to Documentation/trace/ftrace.txt

[Hiraku Toyooka]

This patch adds snapshot description in ftrace documentation.
This description includes what the snapshot is and how to use it.

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Cc: Steven Rostedt rost...@goodmis.org
Cc: Frederic Weisbecker fweis...@gmail.com
Cc: Ingo Molnar mi...@redhat.com
Cc: Rob Landley r...@landley.net
Cc: linux-...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 Documentation/trace/ftrace.txt |   83 
 1 file changed, 83 insertions(+)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 6f51fed..53d6a3c 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1842,6 +1842,89 @@ an error.
  # cat buffer_size_kb
 85
 
+Snapshot
+
+CONFIG_TRACER_SNAPSHOT makes a generic snapshot feature
+available to all non latency tracers. (Latency tracers which
+record max latency, such as irqsoff or wakeup, can't use
+this feature, since those are already using the snapshot
+mechanism internally.)
+
+Snapshot preserves a current trace buffer at a particular point
+in time without stopping tracing. Ftrace swaps the current
+buffer with a spare buffer, and tracing continues in the new
+current (=previous spare) buffer.
+
+The following debugfs files in tracing are related to this
+feature:
+
+  snapshot:
+
+   This is used to take a snapshot and to read the output
+   of the snapshot. Echo 1 into this file to allocate a
+   spare buffer and to take a snapshot (swap), then read
+   the snapshot from this file in the same format as
+   trace (described above in the section The File
+   System). Both reads snapshot and tracing are executable
+   in parallel. When the spare buffer is allocated, echoing
+   0 frees it, and echoing else (positive) values clear the
+   snapshot contents.
+   More details are shown in the table below.
+
+   status\input  | 0  | 1  |else|
+   --++++
+   not allocated |(do nothing)| alloc+swap |   EINVAL   |
+   --++++
+   allocated |free|swap|   clear|
+   --++++
+
+Here is an example of using the snapshot feature.
+
+ # echo 1  events/sched/enable
+ # echo 1  snapshot
+ # cat snapshot
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 71/71   #P:8
+#
+#  _-= irqs-off
+# / _= need-resched
+#| / _---= hardirq/softirq
+#|| / _--= preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  idle-0 [005] d...  2440.603828: sched_switch: 
prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R == 
next_comm=snapshot-test-2 next_pid=2242 next_prio=120
+   sleep-2242  [005] d...  2440.603846: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2242 prev_prio=120 prev_state=R == 
next_comm=kworker/5:1 next_pid=60 next_prio=120
+[...]
+  idle-0 [002] d...  2440.707230: sched_switch: 
prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R == 
next_comm=snapshot-test-2 next_pid=2229 next_prio=120
+
+ # cat trace
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 77/77   #P:8
+#
+#  _-= irqs-off
+# / _= need-resched
+#| / _---= hardirq/softirq
+#|| / _--= preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  idle-0 [007] d...  2440.707395: sched_switch: 
prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R == 
next_comm=snapshot-test-2 next_pid=2243 next_prio=120
+ snapshot-test-2-2229  [002] d...  2440.707438: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2229 prev_prio=120 prev_state=S == 
next_comm=swapper/2 next_pid=0 next_prio=120
+[...]
+
+
+If you try to use this snapshot feature when current tracer is
+one of the latency tracers, you will get the following results.
+
+ # echo wakeup  current_tracer
+ # echo 1  snapshot
+bash: echo: write error: Device or resource busy
+ # cat snapshot
+cat: snapshot: Device or resource busy
+
 ---
 
 More details can be found in the source code, in the

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Re: [PATCH v2 -tip 3/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

(12/15/2012 02:08 AM), Steven Rostedt wrote:

On Fri, 2012-12-07 at 11:07 +0900, Hiraku Toyooka wrote:

Hi, Steven,

(2012/11/30 23:17), Steven Rostedt wrote:
[snip]
  >
  > Actually, I would have:
  >
  >   status\input | 0  | 1  |else|
  >  --++++
  >  not allocated |(do nothing)| alloc+swap |   EINVAL   |
  >  --++++
  >allocated   |free|   swap |   clear|
  >  --++++
  >
  > Perhaps we don't need to do the clear on swap, just let the trace
  > continue where it left off? But in case we should swap...
  >

I think we don't need the clear on swap too.
I'll update my patches like this table.

  > There's a fast way to clear the tracer. Look at what the wakeup tracer
  > does. We can make that generic. If you want, I can write that code up
  > too. Hmm, maybe I'll do that, as it will speed things up for
  > everyone :-)
  >



BTW, any update on this? I really like to get this into 3.9.



I'm applying your review comment and rebasing now. So, I'll post the
updated patch series in a few days.

Thanks,
Hiraku Toyooka

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Re: [PATCH v2 -tip 3/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

(12/15/2012 02:08 AM), Steven Rostedt wrote:

On Fri, 2012-12-07 at 11:07 +0900, Hiraku Toyooka wrote:

Hi, Steven,

(2012/11/30 23:17), Steven Rostedt wrote:
[snip]
  
   Actually, I would have:
  
 status\input | 0  | 1  |else|
--++++
not allocated |(do nothing)| alloc+swap |   EINVAL   |
--++++
  allocated   |free|   swap |   clear|
--++++
  
   Perhaps we don't need to do the clear on swap, just let the trace
   continue where it left off? But in case we should swap...
  

I think we don't need the clear on swap too.
I'll update my patches like this table.

   There's a fast way to clear the tracer. Look at what the wakeup tracer
   does. We can make that generic. If you want, I can write that code up
   too. Hmm, maybe I'll do that, as it will speed things up for
   everyone :-)
  



BTW, any update on this? I really like to get this into 3.9.



I'm applying your review comment and rebasing now. So, I'll post the
updated patch series in a few days.

Thanks,
Hiraku Toyooka

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Re: [PATCH v2 -tip 3/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

old_tracer = current_trace;
>>   *iter->trace = *current_trace;
>>   }
>>   mutex_unlock(_types_lock);
>>
>> +if (iter->snapshot && iter->trace->use_max_tr)
>> +return ERR_PTR(-EBUSY);
>> +
>> ...
>> }
>>
>> static void s_stop(struct seq_file *m, void *p)
>> {
>>   struct trace_iterator *iter = m->private;
>>
>> +if (iter->snapshot && iter->trace->use_max_tr)
>> +return;
>
> This part shouldn't be needed, as if s_start fails it wont call
> s_stop(). But if you are paranoid (like I am ;-) then we can do:
>
> if (WARN_ON_ONCE(iter->snapshot && iter->trace->use_max_tr)
> return;

I think that seq_read() calls s_stop() even if s_start() failed.

seq_read()@fs/seq_file.c:

p = m->op->start(m, );
while (1) {
err = PTR_ERR(p);
if (!p || IS_ERR(p))
break;
...
}
m->op->stop(m, p);

So, I think we need the check in s_stop(), don't we?


Thanks,
Hiraku Toyooka
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Re: [PATCH v2 -tip 3/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

Hi, Steven,

(2012/11/30 23:17), Steven Rostedt wrote:
[snip]

 Actually, I would have:

   status\input | 0  | 1  |else|
  --++++
  not allocated |(do nothing)| alloc+swap |   EINVAL   |
  --++++
allocated   |free|   swap |   clear|
  --++++

 Perhaps we don't need to do the clear on swap, just let the trace
 continue where it left off? But in case we should swap...


I think we don't need the clear on swap too.
I'll update my patches like this table.

 There's a fast way to clear the tracer. Look at what the wakeup tracer
 does. We can make that generic. If you want, I can write that code up
 too. Hmm, maybe I'll do that, as it will speed things up for
 everyone :-)


(I looked over the wakeup tracer, but I couldn't find that code...)


 I think it is almost OK, but there is a problem.
 When we echo 1 to the allocated snapshot, the clear operation adds
 some delay because the time cost of tracing_reset_online_cpus() is in
 proportion to the number of CPUs.
 (It takes 72ms in my 8 CPU environment.)

 So, when the snapshot is already cleared by echoing else values, we
 can avoid the delay on echoing 1 by keeping cleared status
 internally. For example, we can add the cleared flag to struct tracer.
 What do you think about it?

  
   Also we can add a trace_snapshot to the kernel parameters to 
have it

   allocated on boot. But I can add that if you update these patches.
  

 OK, I'll update my patches.

 This part (kernel parameter) can be a separate patch.


Yes.


   Either test here, or better yet, put the test into
   tracing_reset_online_cpus().
  
   if (!buffer)
   return;
  

 I see. I'll add the test to tracing_reset_online_cpus(). Should I make a
 separated patch?

 It's a small change, you can add it to your patch or make it separate.
 I'll leave that up to you.


I see. Perhaps I'll make it separate.

 [snip]
   +static ssize_t tracing_snapshot_read(struct file *filp, char 
__user *ubuf,

   + size_t cnt, loff_t *ppos)
   +{
   +ssize_t ret = 0;
   +
   +mutex_lock(trace_types_lock);
   +if (current_trace  current_trace-use_max_tr)
   +ret = -EBUSY;
   +mutex_unlock(trace_types_lock);
  
   I don't like this, as it is racy. The current tracer could change 
after

   the unlock, and your back to the problem.
  

 You're right...
 This is racy.

   Now what we may be able to do, but it would take a little 
checking for
   lock ordering with trace_access_lock() and 
trace_event_read_lock(), but

   we could add the mutex to trace_types_lock to both s_start() and
   s_stop() and do the check in s_start() if iter-snapshot is true.
  

 If I catch your meaning, do s_start() and s_stop() become like following
 code?
 (Now, s_start() is used from two files - trace and snapshot, so we
 should change static old_tracer to per open-file.)

 Actually, lets nuke all the old_tracer totally, and instead do:

 if (unlikely(strcmp(iter-trace-name, current_trace-name) != 0)) {

 You can make this into a separate patch. You can add a check if
 current_trace is not NULL too, but I need to fix that, as current_trace
 should never be NULL (except for very early boot). But don't worry about
 that, I'll handle that.


O.K. I'll change all the old_tracer checking to the strcmp.

 Or I can write up this patch and send it to you, and you can include it
 in your series.

 static void *s_start(struct seq_file *m, loff_t *pos)
 {
   struct trace_iterator *iter = m-private;
 -static struct tracer *old_tracer;
 ...
   /* copy the tracer to avoid using a global lock all around */
   mutex_lock(trace_types_lock);
 -if (unlikely(old_tracer != current_trace  current_trace)) {
 -old_tracer = current_trace;
 +if (unlikely(iter-old_tracer != current_trace  current_trace)) {
 +iter-old_tracer = current_trace;
   *iter-trace = *current_trace;
   }
   mutex_unlock(trace_types_lock);

 +if (iter-snapshot  iter-trace-use_max_tr)
 +return ERR_PTR(-EBUSY);
 +
 ...
 }

 static void s_stop(struct seq_file *m, void *p)
 {
   struct trace_iterator *iter = m-private;

 +if (iter-snapshot  iter-trace-use_max_tr)
 +return;

 This part shouldn't be needed, as if s_start fails it wont call
 s_stop(). But if you are paranoid (like I am ;-) then we can do:

 if (WARN_ON_ONCE(iter-snapshot  iter-trace-use_max_tr)
 return;

I think that seq_read() calls s_stop() even if s_start() failed.

seq_read()@fs/seq_file.c:

p = m-op-start(m, pos);
while (1) {
err = PTR_ERR(p);
if (!p || IS_ERR(p))
break;
...
}
m-op-stop(m, p);

So, I think we need the check in s_stop(), don't we?


Thanks,
Hiraku Toyooka
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To unsubscribe

Re: [PATCH v2 -tip 3/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

ake a
separated patch?

[snip]
>> +static ssize_t tracing_snapshot_read(struct file *filp, char __user 
*ubuf,

>> + size_t cnt, loff_t *ppos)
>> +{
>> +ssize_t ret = 0;
>> +
>> +mutex_lock(_types_lock);
>> +if (current_trace && current_trace->use_max_tr)
>> +ret = -EBUSY;
>> +mutex_unlock(_types_lock);
>
> I don't like this, as it is racy. The current tracer could change after
> the unlock, and your back to the problem.
>

You're right...
This is racy.

> Now what we may be able to do, but it would take a little checking for
> lock ordering with trace_access_lock() and trace_event_read_lock(), but
> we could add the mutex to trace_types_lock to both s_start() and
> s_stop() and do the check in s_start() if iter->snapshot is true.
>

If I catch your meaning, do s_start() and s_stop() become like following
code?
(Now, s_start() is used from two files - "trace" and "snapshot", so we
should change static "old_tracer" to per open-file.)

static void *s_start(struct seq_file *m, loff_t *pos)
{
 struct trace_iterator *iter = m->private;
-static struct tracer *old_tracer;
...
 /* copy the tracer to avoid using a global lock all around */
 mutex_lock(_types_lock);
-if (unlikely(old_tracer != current_trace && current_trace)) {
-old_tracer = current_trace;
+if (unlikely(iter->old_tracer != current_trace && current_trace)) {
+iter->old_tracer = current_trace;
 *iter->trace = *current_trace;
 }
 mutex_unlock(_types_lock);

+if (iter->snapshot && iter->trace->use_max_tr)
+return ERR_PTR(-EBUSY);
+
...
}

static void s_stop(struct seq_file *m, void *p)
{
 struct trace_iterator *iter = m->private;

+if (iter->snapshot && iter->trace->use_max_tr)
+return;
...
}

> This means we can nuke the tracing_snapshot_read() and just use
> seq_read() directly.
>

Yes, I see.

Thanks,
Hiraku Toyooka


>> +if (ret < 0)
>> +return ret;
>> +
>> +ret = seq_read(filp, ubuf, cnt, ppos);
>> +
>> +return ret;
>> +}
>> +
>> +static ssize_t
>> +tracing_snapshot_write(struct file *filp, const char __user *ubuf,
size_t cnt,
>> +   loff_t *ppos)
>> +{
>> +unsigned long val = 0;
>> +int ret;
>> +
>> +ret = tracing_update_buffers();
>> +if (ret < 0)
>> +return ret;
>> +
>> +ret = kstrtoul_from_user(ubuf, cnt, 10, );
>> +if (ret)
>> +return ret;
>> +
>> +mutex_lock(_types_lock);
>> +
>> +if (current_trace->use_max_tr) {
>> +ret = -EBUSY;
>> +goto out;
>> +}
>
> Again, I would check the value of 'val' and if it is '1' then allocate
> the buffers, '0' free them, and anything else just clear them or return
> EINVAL if the buffers are not allocated.
>
> If it is '1' and the buffers are already allocated, then clear them too.
>
> Then we can just remove the 'snapshot_allocate' file.
>
> Thanks!
>
> -- Steve
>
>> +
>> +if (!current_trace->allocated_snapshot) {
>> +/* allocate spare buffer for snapshot */
>> +ret = resize_buffer_duplicate_size(_tr, _trace,
>> +   RING_BUFFER_ALL_CPUS);
>> +if (ret < 0)
>> +goto out;
>> +current_trace->allocated_snapshot = true;
>> +}
>> +
>> +if (val) {
>> +local_irq_disable();
>> +update_max_tr(_trace, current, smp_processor_id());
>> +local_irq_enable();
>> +} else
>> +tracing_reset_online_cpus(_tr);
>> +
>> +*ppos += cnt;
>> +ret = cnt;
>> +out:
>> +mutex_unlock(_types_lock);
>> +return ret;
>> +}
>> +
>> +static ssize_t
>> +tracing_snapshot_allocate_read(struct file *filp, char __user *ubuf,
>> +   size_t cnt, loff_t *ppos)
>> +{
>> +char buf[64];
>> +int r;
>> +
>> +r = sprintf(buf, "%d\n", current_trace->allocated_snapshot);
>> +return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
>> +}
>> +
>> +static ssize_t
>> +tracing_snapshot_allocate_write(struct file *filp, const char
__user *ubuf,
>> +size_t cnt, loff_t *ppos)
>> +{
>> +unsigned long val;
>> +int ret;
>> +
>> +ret = tracing_update_buffers();
>> +if (ret < 0)
>> +return ret;
>> +
>> +ret = kstrtoul_from_u

Re: [PATCH v2 -tip 3/4] tracing: make a snapshot feature available from userspace

[Hiraku Toyooka]

() is used from two files - trace and snapshot, so we
should change static old_tracer to per open-file.)

static void *s_start(struct seq_file *m, loff_t *pos)
{
 struct trace_iterator *iter = m-private;
-static struct tracer *old_tracer;
...
 /* copy the tracer to avoid using a global lock all around */
 mutex_lock(trace_types_lock);
-if (unlikely(old_tracer != current_trace  current_trace)) {
-old_tracer = current_trace;
+if (unlikely(iter-old_tracer != current_trace  current_trace)) {
+iter-old_tracer = current_trace;
 *iter-trace = *current_trace;
 }
 mutex_unlock(trace_types_lock);

+if (iter-snapshot  iter-trace-use_max_tr)
+return ERR_PTR(-EBUSY);
+
...
}

static void s_stop(struct seq_file *m, void *p)
{
 struct trace_iterator *iter = m-private;

+if (iter-snapshot  iter-trace-use_max_tr)
+return;
...
}

 This means we can nuke the tracing_snapshot_read() and just use
 seq_read() directly.


Yes, I see.

Thanks,
Hiraku Toyooka


 +if (ret  0)
 +return ret;
 +
 +ret = seq_read(filp, ubuf, cnt, ppos);
 +
 +return ret;
 +}
 +
 +static ssize_t
 +tracing_snapshot_write(struct file *filp, const char __user *ubuf,
size_t cnt,
 +   loff_t *ppos)
 +{
 +unsigned long val = 0;
 +int ret;
 +
 +ret = tracing_update_buffers();
 +if (ret  0)
 +return ret;
 +
 +ret = kstrtoul_from_user(ubuf, cnt, 10, val);
 +if (ret)
 +return ret;
 +
 +mutex_lock(trace_types_lock);
 +
 +if (current_trace-use_max_tr) {
 +ret = -EBUSY;
 +goto out;
 +}

 Again, I would check the value of 'val' and if it is '1' then allocate
 the buffers, '0' free them, and anything else just clear them or return
 EINVAL if the buffers are not allocated.

 If it is '1' and the buffers are already allocated, then clear them too.

 Then we can just remove the 'snapshot_allocate' file.

 Thanks!

 -- Steve

 +
 +if (!current_trace-allocated_snapshot) {
 +/* allocate spare buffer for snapshot */
 +ret = resize_buffer_duplicate_size(max_tr, global_trace,
 +   RING_BUFFER_ALL_CPUS);
 +if (ret  0)
 +goto out;
 +current_trace-allocated_snapshot = true;
 +}
 +
 +if (val) {
 +local_irq_disable();
 +update_max_tr(global_trace, current, smp_processor_id());
 +local_irq_enable();
 +} else
 +tracing_reset_online_cpus(max_tr);
 +
 +*ppos += cnt;
 +ret = cnt;
 +out:
 +mutex_unlock(trace_types_lock);
 +return ret;
 +}
 +
 +static ssize_t
 +tracing_snapshot_allocate_read(struct file *filp, char __user *ubuf,
 +   size_t cnt, loff_t *ppos)
 +{
 +char buf[64];
 +int r;
 +
 +r = sprintf(buf, %d\n, current_trace-allocated_snapshot);
 +return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
 +}
 +
 +static ssize_t
 +tracing_snapshot_allocate_write(struct file *filp, const char
__user *ubuf,
 +size_t cnt, loff_t *ppos)
 +{
 +unsigned long val;
 +int ret;
 +
 +ret = tracing_update_buffers();
 +if (ret  0)
 +return ret;
 +
 +ret = kstrtoul_from_user(ubuf, cnt, 10, val);
 +if (ret)
 +return ret;
 +
 +mutex_lock(trace_types_lock);
 +
 +if (current_trace-use_max_tr) {
 +ret = -EBUSY;
 +goto out;
 +}
 +
 +if (current_trace-allocated_snapshot == !val) {
 +if (val) {
 +/* allocate spare buffer for snapshot */
 +ret = resize_buffer_duplicate_size(max_tr,
 +global_trace, RING_BUFFER_ALL_CPUS);
 +if (ret  0)
 +goto out;
 +} else {
 +tracing_reset_online_cpus(max_tr);
 +ring_buffer_resize(max_tr.buffer, 1,
 +   RING_BUFFER_ALL_CPUS);
 +set_buffer_entries(max_tr, 1);
 +}
 +current_trace-allocated_snapshot = !!val;
 +}
 +
 +*ppos += cnt;
 +ret = cnt;
 +out:
 +mutex_unlock(trace_types_lock);
 +return ret;
 +}
 +#endif /* CONFIG_TRACER_SNAPSHOT */
 +
  static const struct file_operations tracing_max_lat_fops = {
  .open= tracing_open_generic,
  .read= tracing_max_lat_read,
 @@ -4092,6 +4233,23 @@ static const struct file_operations
trace_clock_fops = {
  .write= tracing_clock_write,
  };

 +#ifdef CONFIG_TRACER_SNAPSHOT
 +static const struct file_operations snapshot_fops = {
 +.open= tracing_snapshot_open,
 +.read= tracing_snapshot_read,
 +.write= tracing_snapshot_write,
 +.llseek= tracing_seek,
 +.release= tracing_release,
 +};
 +
 +static const struct file_operations snapshot_allocate_fops = {
 +.open   = tracing_open_generic,
 +.read   = tracing_snapshot_allocate_read,
 +.write  = tracing_snapshot_allocate_write,
 +.llseek = generic_file_llseek

[tip:perf/core] tracing: Change tracer's integer flags to bool

[tip-bot for Hiraku Toyooka]

Commit-ID:  f43c738bfa8608424610e4fc1aef4d4644e2ce11
Gitweb: http://git.kernel.org/tip/f43c738bfa8608424610e4fc1aef4d4644e2ce11
Author: Hiraku Toyooka 
AuthorDate: Tue, 2 Oct 2012 17:27:10 +0900
Committer:  Steven Rostedt 
CommitDate: Wed, 31 Oct 2012 16:45:25 -0400

tracing: Change tracer's integer flags to bool

print_max and use_max_tr in struct tracer are "int" variables and
used like flags. This is wasteful, so change the type to "bool".

Link: http://lkml.kernel.org/r/20121002082710.9807.86393.stgit@falsita

Signed-off-by: Hiraku Toyooka 
Signed-off-by: Steven Rostedt 
---
 kernel/trace/trace.h  |4 ++--
 kernel/trace/trace_irqsoff.c  |   12 ++--
 kernel/trace/trace_sched_wakeup.c |8 
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index c15f528..c56a233 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -285,8 +285,8 @@ struct tracer {
int (*set_flag)(u32 old_flags, u32 bit, int set);
struct tracer   *next;
struct tracer_flags *flags;
-   int print_max;
-   int use_max_tr;
+   boolprint_max;
+   booluse_max_tr;
 };
 
 
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 11edebd..5ffce7b 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -604,7 +604,7 @@ static struct tracer irqsoff_tracer __read_mostly =
.reset  = irqsoff_tracer_reset,
.start  = irqsoff_tracer_start,
.stop   = irqsoff_tracer_stop,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = irqsoff_print_header,
.print_line = irqsoff_print_line,
.flags  = _flags,
@@ -614,7 +614,7 @@ static struct tracer irqsoff_tracer __read_mostly =
 #endif
.open   = irqsoff_trace_open,
.close  = irqsoff_trace_close,
-   .use_max_tr = 1,
+   .use_max_tr = true,
 };
 # define register_irqsoff(trace) register_tracer()
 #else
@@ -637,7 +637,7 @@ static struct tracer preemptoff_tracer __read_mostly =
.reset  = irqsoff_tracer_reset,
.start  = irqsoff_tracer_start,
.stop   = irqsoff_tracer_stop,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = irqsoff_print_header,
.print_line = irqsoff_print_line,
.flags  = _flags,
@@ -647,7 +647,7 @@ static struct tracer preemptoff_tracer __read_mostly =
 #endif
.open   = irqsoff_trace_open,
.close  = irqsoff_trace_close,
-   .use_max_tr = 1,
+   .use_max_tr = true,
 };
 # define register_preemptoff(trace) register_tracer()
 #else
@@ -672,7 +672,7 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
.reset  = irqsoff_tracer_reset,
.start  = irqsoff_tracer_start,
.stop   = irqsoff_tracer_stop,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = irqsoff_print_header,
.print_line = irqsoff_print_line,
.flags  = _flags,
@@ -682,7 +682,7 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
 #endif
.open   = irqsoff_trace_open,
.close  = irqsoff_trace_close,
-   .use_max_tr = 1,
+   .use_max_tr = true,
 };
 
 # define register_preemptirqsoff(trace) register_tracer()
diff --git a/kernel/trace/trace_sched_wakeup.c 
b/kernel/trace/trace_sched_wakeup.c
index 2f6af78..bc64fc1 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -589,7 +589,7 @@ static struct tracer wakeup_tracer __read_mostly =
.reset  = wakeup_tracer_reset,
.start  = wakeup_tracer_start,
.stop   = wakeup_tracer_stop,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = wakeup_print_header,
.print_line = wakeup_print_line,
.flags  = _flags,
@@ -599,7 +599,7 @@ static struct tracer wakeup_tracer __read_mostly =
 #endif
.open   = wakeup_trace_open,
.close  = wakeup_trace_close,
-   .use_max_tr = 1,
+   .use_max_tr = true,
 };
 
 static struct tracer wakeup_rt_tracer __read_mostly =
@@ -610,7 +610,7 @@ static struct tracer wakeup_rt_tracer __read_mostly =
.start  = wakeup_tracer_start,
.stop   = wakeup_tracer_stop,
.wait_pipe  = poll_wait_pipe,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = wakeup_print_header,
.print_line = wakeup_print_line,
.flags  = _flags,
@@ -620,7 +620,7 @@ static struct tracer wakeup_rt_tracer __read_mostly =
 

[tip:perf/core] tracing: Change tracer's integer flags to bool

[tip-bot for Hiraku Toyooka]

Commit-ID:  f43c738bfa8608424610e4fc1aef4d4644e2ce11
Gitweb: http://git.kernel.org/tip/f43c738bfa8608424610e4fc1aef4d4644e2ce11
Author: Hiraku Toyooka hiraku.toyooka...@hitachi.com
AuthorDate: Tue, 2 Oct 2012 17:27:10 +0900
Committer:  Steven Rostedt rost...@goodmis.org
CommitDate: Wed, 31 Oct 2012 16:45:25 -0400

tracing: Change tracer's integer flags to bool

print_max and use_max_tr in struct tracer are int variables and
used like flags. This is wasteful, so change the type to bool.

Link: http://lkml.kernel.org/r/20121002082710.9807.86393.stgit@falsita

Signed-off-by: Hiraku Toyooka hiraku.toyooka...@hitachi.com
Signed-off-by: Steven Rostedt rost...@goodmis.org
---
 kernel/trace/trace.h  |4 ++--
 kernel/trace/trace_irqsoff.c  |   12 ++--
 kernel/trace/trace_sched_wakeup.c |8 
 3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index c15f528..c56a233 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -285,8 +285,8 @@ struct tracer {
int (*set_flag)(u32 old_flags, u32 bit, int set);
struct tracer   *next;
struct tracer_flags *flags;
-   int print_max;
-   int use_max_tr;
+   boolprint_max;
+   booluse_max_tr;
 };
 
 
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 11edebd..5ffce7b 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -604,7 +604,7 @@ static struct tracer irqsoff_tracer __read_mostly =
.reset  = irqsoff_tracer_reset,
.start  = irqsoff_tracer_start,
.stop   = irqsoff_tracer_stop,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = irqsoff_print_header,
.print_line = irqsoff_print_line,
.flags  = tracer_flags,
@@ -614,7 +614,7 @@ static struct tracer irqsoff_tracer __read_mostly =
 #endif
.open   = irqsoff_trace_open,
.close  = irqsoff_trace_close,
-   .use_max_tr = 1,
+   .use_max_tr = true,
 };
 # define register_irqsoff(trace) register_tracer(trace)
 #else
@@ -637,7 +637,7 @@ static struct tracer preemptoff_tracer __read_mostly =
.reset  = irqsoff_tracer_reset,
.start  = irqsoff_tracer_start,
.stop   = irqsoff_tracer_stop,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = irqsoff_print_header,
.print_line = irqsoff_print_line,
.flags  = tracer_flags,
@@ -647,7 +647,7 @@ static struct tracer preemptoff_tracer __read_mostly =
 #endif
.open   = irqsoff_trace_open,
.close  = irqsoff_trace_close,
-   .use_max_tr = 1,
+   .use_max_tr = true,
 };
 # define register_preemptoff(trace) register_tracer(trace)
 #else
@@ -672,7 +672,7 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
.reset  = irqsoff_tracer_reset,
.start  = irqsoff_tracer_start,
.stop   = irqsoff_tracer_stop,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = irqsoff_print_header,
.print_line = irqsoff_print_line,
.flags  = tracer_flags,
@@ -682,7 +682,7 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
 #endif
.open   = irqsoff_trace_open,
.close  = irqsoff_trace_close,
-   .use_max_tr = 1,
+   .use_max_tr = true,
 };
 
 # define register_preemptirqsoff(trace) register_tracer(trace)
diff --git a/kernel/trace/trace_sched_wakeup.c 
b/kernel/trace/trace_sched_wakeup.c
index 2f6af78..bc64fc1 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -589,7 +589,7 @@ static struct tracer wakeup_tracer __read_mostly =
.reset  = wakeup_tracer_reset,
.start  = wakeup_tracer_start,
.stop   = wakeup_tracer_stop,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = wakeup_print_header,
.print_line = wakeup_print_line,
.flags  = tracer_flags,
@@ -599,7 +599,7 @@ static struct tracer wakeup_tracer __read_mostly =
 #endif
.open   = wakeup_trace_open,
.close  = wakeup_trace_close,
-   .use_max_tr = 1,
+   .use_max_tr = true,
 };
 
 static struct tracer wakeup_rt_tracer __read_mostly =
@@ -610,7 +610,7 @@ static struct tracer wakeup_rt_tracer __read_mostly =
.start  = wakeup_tracer_start,
.stop   = wakeup_tracer_stop,
.wait_pipe  = poll_wait_pipe,
-   .print_max  = 1,
+   .print_max  = true,
.print_header   = wakeup_print_header,
.print_line = wakeup_print_line

[PATCH v2 -tip 2/4] tracing: add a resize function for making one buffer equivalent to the other buffer

[Hiraku Toyooka]

Trace buffer size is now per-cpu, so that there are following two
patterns in resize of the buffers.

  (1) resize per-cpu buffers to same given size
  (2) resize per-cpu buffers to the other trace_array's buffer size
  for each CPU (such as preparing the max_tr which is equivalent
  to the global_trace's size)

__tracing_resize_ring_buffer() can be used for (1), and had
implemented (2) inside it for resetting the global_trace to the
original size.

(2) was also implemented in other place. So this patch assembles
them in a new function - resize_buffer_duplicate_size().

Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: linux-kernel@vger.kernel.org
---

 kernel/trace/trace.c |   58 +++---
 1 files changed, 31 insertions(+), 27 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 08acf42..d71eee1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3017,6 +3017,31 @@ static void set_buffer_entries(struct trace_array *tr, 
unsigned long val)
tr->data[cpu]->entries = val;
 }
 
+/* resize @tr's buffer to the size of @size_tr's entries */
+static int resize_buffer_duplicate_size(struct trace_array *tr,
+   struct trace_array *size_tr, int cpu_id)
+{
+   int cpu, ret = 0;
+
+   if (cpu_id == RING_BUFFER_ALL_CPUS) {
+   for_each_tracing_cpu(cpu) {
+   ret = ring_buffer_resize(tr->buffer,
+   size_tr->data[cpu]->entries, cpu);
+   if (ret < 0)
+   break;
+   tr->data[cpu]->entries = size_tr->data[cpu]->entries;
+   }
+   } else {
+   ret = ring_buffer_resize(tr->buffer,
+   size_tr->data[cpu_id]->entries, cpu_id);
+   if (ret == 0)
+   tr->data[cpu_id]->entries =
+   size_tr->data[cpu_id]->entries;
+   }
+
+   return ret;
+}
+
 static int __tracing_resize_ring_buffer(unsigned long size, int cpu)
 {
int ret;
@@ -3037,23 +3062,8 @@ static int __tracing_resize_ring_buffer(unsigned long 
size, int cpu)
 
ret = ring_buffer_resize(max_tr.buffer, size, cpu);
if (ret < 0) {
-   int r = 0;
-
-   if (cpu == RING_BUFFER_ALL_CPUS) {
-   int i;
-   for_each_tracing_cpu(i) {
-   r = ring_buffer_resize(global_trace.buffer,
-   global_trace.data[i]->entries,
-   i);
-   if (r < 0)
-   break;
-   }
-   } else {
-   r = ring_buffer_resize(global_trace.buffer,
-   global_trace.data[cpu]->entries,
-   cpu);
-   }
-
+   int r = resize_buffer_duplicate_size(_trace,
+_trace, cpu);
if (r < 0) {
/*
 * AARGH! We are left with different
@@ -3191,17 +3201,11 @@ static int tracing_set_tracer(const char *buf)
 
topts = create_trace_option_files(t);
if (t->use_max_tr) {
-   int cpu;
/* we need to make per cpu buffer sizes equivalent */
-   for_each_tracing_cpu(cpu) {
-   ret = ring_buffer_resize(max_tr.buffer,
-   global_trace.data[cpu]->entries,
-   cpu);
-   if (ret < 0)
-   goto out;
-   max_tr.data[cpu]->entries =
-   global_trace.data[cpu]->entries;
-   }
+   ret = resize_buffer_duplicate_size(_tr, _trace,
+  RING_BUFFER_ALL_CPUS);
+   if (ret < 0)
+   goto out;
}
 
if (t->init) {

--
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[PATCH v2 -tip 4/4] tracing: add description of snapshot to Documentation/trace/ftrace.txt

[Hiraku Toyooka]

This patch adds snapshot description in ftrace documentation.
This description includes what the snapshot is and how to use it.

Signed-off-by: Hiraku Toyooka 
Cc: Steven Rostedt 
Cc: Frederic Weisbecker 
Cc: Ingo Molnar 
Cc: Rob Landley 
Cc: linux-...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---

 Documentation/trace/ftrace.txt |   97 
 1 files changed, 97 insertions(+), 0 deletions(-)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 6f51fed..68ac294 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1842,6 +1842,103 @@ an error.
  # cat buffer_size_kb
 85
 
+Snapshot
+
+CONFIG_TRACER_SNAPSHOT makes a generic snapshot feature
+available to all non latency tracers. (Latency tracers which
+record max latency, such as "irqsoff" or "wakeup", can't use
+this feature, since those are already using the snapshot
+mechanism internally.)
+
+Snapshot preserves a trace buffer at a particular point in time
+without stopping tracing. Ftrace swaps the current buffer with a
+spare buffer, and tracing continues in the (previous) spare
+buffer.
+
+The following debugfs files in "tracing" are related to this
+feature:
+
+  snapshot:
+
+   This is used to take a snapshot and to read the output
+   of the snapshot. Echo 1 into this file to allocate a
+   spare buffer and to take a snapshot, then read the
+   snapshot from the file in the same format as "trace"
+   (described above in the section "The File System"). Both
+   reads snapshot and tracing are executable in parallel.
+   Echoing 0 erases the snapshot contents.
+
+  snapshot_allocate:
+
+   This is used to pre-allocate or free a spare buffer.
+   Echo 1 into this file to pre-allocate a spare buffer if
+   you don't want to fail in the next snapshot due to
+   memory allocation failure, or if you don't want to lose
+   older trace data while allocating buffer. Echo 0 to free
+   the spare buffer when the snapshot becomes unnecessary.
+   If you take the next snapshot again, you can reuse the
+   buffer, then just erase the snapshot contents by echoing
+   1 into the "snapshot" file, instead of freeing the
+   buffer.
+
+   Reads from this file display whether the spare buffer is
+   allocated. When current_tracer is changed, the allocated
+   spare buffer is freed. If the next tracer is one of the
+   latency tracers, this value turns into 1 and can't be
+   changed, or else the value starts with 0.
+
+
+Here is an example of using the snapshot feature.
+
+ # echo 1 > snapshot_allocate (if you want to pre-allocate the spare buffer)
+ # echo 1 > events/sched/enable
+ # echo 1 > snapshot
+ # cat snapshot
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 71/71   #P:8
+#
+#  _-=> irqs-off
+# / _=> need-resched
+#| / _---=> hardirq/softirq
+#|| / _--=> preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  -0 [005] d...  2440.603828: sched_switch: 
prev_comm=swapper/5 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2242 next_prio=120
+   sleep-2242  [005] d...  2440.603846: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2242 prev_prio=120 prev_state=R ==> 
next_comm=kworker/5:1 next_pid=60 next_prio=120
+[...]
+  -0 [002] d...  2440.707230: sched_switch: 
prev_comm=swapper/2 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2229 next_prio=120
+ # cat trace
+# tracer: nop
+#
+# entries-in-buffer/entries-written: 77/77   #P:8
+#
+#  _-=> irqs-off
+# / _=> need-resched
+#| / _---=> hardirq/softirq
+#|| / _--=> preempt-depth
+#||| / delay
+#   TASK-PID   CPU#  TIMESTAMP  FUNCTION
+#  | |   |      | |
+  -0 [007] d...  2440.707395: sched_switch: 
prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R ==> 
next_comm=snapshot-test-2 next_pid=2243 next_prio=120
+ snapshot-test-2-2229  [002] d...  2440.707438: sched_switch: 
prev_comm=snapshot-test-2 prev_pid=2229 prev_prio=120 prev_state=S ==> 
next_comm=swapper/2 next_pid=0 next_prio=120
+[...]
+
+
+If you try to use this snapshot feature when current tracer is
+one of the latency tracers, you will get the following results.
+
+ # echo wakeup > current_tracer
+ # cat snapshot_allocate
+1
+ # echo 1 > snapshot_allocate
+bash: echo: write error: Device or resource bu