Re: [uml-devel] [PATCH v3 3/3] um: enable trace irqflags support
On Sun, Oct 19, 2014 at 5:14 PM, Thomas Meyer wrote:
> --- a/arch/um/kernel/um_arch.c
> +++ b/arch/um/kernel/um_arch.c
> @@ -251,6 +251,9 @@ static struct notifier_block panic_exit_notifier = {
>
> void uml_finishsetup(void)
> {
> +#ifdef CONFIG_LOCKDEP
> + lockdep_init();
> +#endif
The #ifdef is not needed. include/linux/lockdep.h provides a dummy
definition if !CONFIG_LOCKDEP.
Gr{oetje,eeting}s,
Geert
--
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Re: [uml-devel] [UM] Long loop in __getnsdayoftime() after resume from ram
On Sun, Oct 19, 2014 at 2:39 PM, Thomas Meyer wrote: > Hello, > > in UML kernel I get a long cpu using loop in __getnstimeofday() > (kernel/time/timekeeping.c:315) in the call of timespec_add_ns(), > when I left the host kernel suspended to ram for a few hours and resume > again. > this is because it seems like the tk->xtime_sec wasn't updated yet, but > the nsecs were. nsecs can be as high as 8111000111000111000l > > the function timespec_add_ns() (include/linux/time.h:266) will call > __iter_div_u64_rem() which has an optimized loop for the case > that the dividend is not much bigger as the divisior. > but this isn't the case for resume from ram on the host kernel. > > any ideas how to fix this? is it possible to intercept the resume from > ram and update the timekeeper->xtime_sec somehow? > or can the um arch somehow overwrite timespec_add_ns() to always use > div_u64_rem() instead? Hmm, does this always happen? At least on my notebook it did not happen. I've started an UML yesterday suspended it and after more than 12h it worked fine today. BTW: Do you see the issue also then freezing UML using the freezer cgroup? Would be easier to debug. :) -- Thanks, //richard -- Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho ___ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
Re: [uml-devel] [PATCH v3 3/3] um: enable trace irqflags support
- Original Message -
> From: "Thomas Meyer"
> To: "user-mode-linux-devel"
> Sent: Sunday, October 19, 2014 4:14:13 PM
> Subject: [uml-devel] [PATCH v3 3/3] um: enable trace irqflags support
>
> Add TRACE_IRQFLAGS_SUPPORT to UML.
> This enables LOCKDEP_SUPPORT and TRACING_SUPPORT.
FYI: I'm currently working on porting ftrace() support to
uml. It will take another week or two since I don't have enough
time to debug, and it isn't stable yet (read as is panic()ing randomly)
>
> Signed-off-by: Thomas Meyer
> ---
> diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common
> index 87bc868..6a33c3a 100644
> --- a/arch/um/Kconfig.common
> +++ b/arch/um/Kconfig.common
> @@ -28,10 +28,9 @@ config PCI
> config PCMCIA
> bool
>
> -# Yet to do!
> config TRACE_IRQFLAGS_SUPPORT
> bool
> - default n
> + default y
>
> config LOCKDEP_SUPPORT
> bool
> diff --git a/arch/um/include/asm/irqflags.h
> b/arch/um/include/asm/irqflags.h
> index c780d8a..c5b636e 100644
> --- a/arch/um/include/asm/irqflags.h
> +++ b/arch/um/include/asm/irqflags.h
> @@ -34,9 +34,9 @@ static inline unsigned long
> arch_local_irq_save(void)
> return flags;
> }
>
> -static inline bool arch_irqs_disabled(void)
> +static inline int arch_irqs_disabled_flags(unsigned long flags)
> {
> - return arch_local_save_flags() == 0;
> + return flags == 0;
> }
>
> #endif
I'm not sure if this is correct. I'd rather would have another function
implemented instead of removing the check for disabled irqs.
cheers,
daniel
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Re: [uml-devel] [UM] Long loop in __getnsdayoftime() after resume from ram
Am 20.10.2014 10:27 schrieb Richard Weinberger : > > On Sun, Oct 19, 2014 at 2:39 PM, Thomas Meyer wrote: > > Hello, > > > > in UML kernel I get a long cpu using loop in __getnstimeofday() > > (kernel/time/timekeeping.c:315) in the call of timespec_add_ns(), > > when I left the host kernel suspended to ram for a few hours and resume > > again. > > this is because it seems like the tk->xtime_sec wasn't updated yet, but > > the nsecs were. nsecs can be as high as 8111000111000111000l > > > > the function timespec_add_ns() (include/linux/time.h:266) will call > > __iter_div_u64_rem() which has an optimized loop for the case > > that the dividend is not much bigger as the divisior. > > but this isn't the case for resume from ram on the host kernel. > > > > any ideas how to fix this? is it possible to intercept the resume from > > ram and update the timekeeper->xtime_sec somehow? > > or can the um arch somehow overwrite timespec_add_ns() to always use > > div_u64_rem() instead? > > Hmm, does this always happen? Yes, my single core system seems to trigger this every time after resume from ram. > At least on my notebook it did not happen. I've started an UML yesterday > suspended it and after more than 12h it worked fine today. > > BTW: Do you see the issue also then freezing UML using the freezer cgroup? I'm not sure what do you mean by this. Do I need to enable some special configs for this in the host or uml kernel? > Would be easier to debug. :) > > -- > Thanks, > //richard -- Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho ___ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
Re: [uml-devel] [UM] Long loop in __getnsdayoftime() after resume from ram
Am 20.10.2014 um 11:51 schrieb Thomas Meyer: >> Hmm, does this always happen? > > Yes, my single core system seems to trigger this every time after resume from > ram. What is your host kernel? >> At least on my notebook it did not happen. I've started an UML yesterday >> suspended it and after more than 12h it worked fine today. >> >> BTW: Do you see the issue also then freezing UML using the freezer cgroup? > > I'm not sure what do you mean by this. Do I need to enable some special > configs for this in the host or uml kernel? Create on the host side a new freezer cgroup, put UML into it and freeze/thaw it. i.e. mkdir /sys/fs/cgroup/freezer/uml ; echo > /sys/fs/cgroup/freezer/uml/tasks. In the said shell run UML and then freeze it using echo FROZEN > /sys/fs/cgroup/freezer/uml/freezer.state. Later thaw it: echo THAWED > /sys/fs/cgroup/freezer/uml/freezer.state Thanks, //richard -- Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho ___ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
Re: [uml-devel] [PATCH v3 3/3] um: enable trace irqflags support
Am 20.10.2014 11:28 schrieb Daniel Walter :
>
> - Original Message -
> > From: "Thomas Meyer"
> > To: "user-mode-linux-devel"
> > Sent: Sunday, October 19, 2014 4:14:13 PM
> > Subject: [uml-devel] [PATCH v3 3/3] um: enable trace irqflags support
> >
> > Add TRACE_IRQFLAGS_SUPPORT to UML.
> > This enables LOCKDEP_SUPPORT and TRACING_SUPPORT.
>
>
> FYI: I'm currently working on porting ftrace() support to
> uml. It will take another week or two since I don't have enough
> time to debug, and it isn't stable yet (read as is panic()ing randomly)
Good to know :-)
Thanks for you stack trace support work!
BTW. When triggering a sysrq t with the uml console the stack trace is not
displayed, it says that the stack trace failed because a sigsegv happens in the
stack trace or something like that. Bug or feature?
>
> >
> > Signed-off-by: Thomas Meyer
> > ---
> > diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common
> > index 87bc868..6a33c3a 100644
> > --- a/arch/um/Kconfig.common
> > +++ b/arch/um/Kconfig.common
> > @@ -28,10 +28,9 @@ config PCI
> > config PCMCIA
> > bool
> >
> > -# Yet to do!
> > config TRACE_IRQFLAGS_SUPPORT
> > bool
> > - default n
> > + default y
> >
> > config LOCKDEP_SUPPORT
> > bool
> > diff --git a/arch/um/include/asm/irqflags.h
> > b/arch/um/include/asm/irqflags.h
> > index c780d8a..c5b636e 100644
> > --- a/arch/um/include/asm/irqflags.h
> > +++ b/arch/um/include/asm/irqflags.h
> > @@ -34,9 +34,9 @@ static inline unsigned long
> > arch_local_irq_save(void)
> > return flags;
> > }
> >
> > -static inline bool arch_irqs_disabled(void)
> > +static inline int arch_irqs_disabled_flags(unsigned long flags)
> > {
> > - return arch_local_save_flags() == 0;
> > + return flags == 0;
> > }
> >
> > #endif
>
> I'm not sure if this is correct. I'd rather would have another function
> implemented instead of removing the check for disabled irqs.
There is a default coding for arch_irqs_disabled which calls
arch_irqs_disabled_flags.
The logic after above change should be the same as before.
>
>
> cheers,
>
> daniel
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Re: [uml-devel] [PATCH v3 3/3] um: enable trace irqflags support
On Mon, Oct 20, 2014 at 1:18 PM, Thomas Meyer wrote: > Am 20.10.2014 11:28 schrieb Daniel Walter : >> >> - Original Message - >> > From: "Thomas Meyer" >> > To: "user-mode-linux-devel" >> > Sent: Sunday, October 19, 2014 4:14:13 PM >> > Subject: [uml-devel] [PATCH v3 3/3] um: enable trace irqflags support >> > >> > Add TRACE_IRQFLAGS_SUPPORT to UML. >> > This enables LOCKDEP_SUPPORT and TRACING_SUPPORT. >> >> >> FYI: I'm currently working on porting ftrace() support to >> uml. It will take another week or two since I don't have enough >> time to debug, and it isn't stable yet (read as is panic()ing randomly) > > Good to know :-) > > Thanks for you stack trace support work! > > BTW. When triggering a sysrq t with the uml console the stack trace is not > displayed, it says that the stack trace failed because a sigsegv happens in > the stack trace or something like that. Bug or feature? Huh? More details please. uml_mconsole's sysrq t works fine here with both x86 and x86_86 uml. -- Thanks, //richard -- Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho ___ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
Re: [uml-devel] [PATCH v3 3/3] um: enable trace irqflags support
Am 20.10.2014 um 14:13 schrieb Richard Weinberger: > On Mon, Oct 20, 2014 at 1:18 PM, Thomas Meyer wrote: >> Am 20.10.2014 11:28 schrieb Daniel Walter : >>> >>> - Original Message - From: "Thomas Meyer" To: "user-mode-linux-devel" Sent: Sunday, October 19, 2014 4:14:13 PM Subject: [uml-devel] [PATCH v3 3/3] um: enable trace irqflags support Add TRACE_IRQFLAGS_SUPPORT to UML. This enables LOCKDEP_SUPPORT and TRACING_SUPPORT. >>> >>> >>> FYI: I'm currently working on porting ftrace() support to >>> uml. It will take another week or two since I don't have enough >>> time to debug, and it isn't stable yet (read as is panic()ing randomly) >> >> Good to know :-) >> >> Thanks for you stack trace support work! >> >> BTW. When triggering a sysrq t with the uml console the stack trace is not >> displayed, it says that the stack trace failed because a sigsegv happens in >> the stack trace or something like that. Bug or feature? > > Huh? More details please. uml_mconsole's sysrq t works fine here with > both x86 and x86_86 uml. Hi, sorry about the fuss. everything seems to work correctly. Maybe I did see this while doing some testing with some fixes. sorry. > > -- > Thanks, > //richard -- Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho ___ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
Re: [uml-devel] [UM] Long loop in __getnsdayoftime() after resume from ram
Am Montag, den 20.10.2014, 11:56 +0200 schrieb Richard Weinberger: > Am 20.10.2014 um 11:51 schrieb Thomas Meyer: > >> Hmm, does this always happen? > > > > Yes, my single core system seems to trigger this every time after resume > > from ram. > > What is your host kernel? The standard Fedora kernel: 3.16.4-200.fc20.x86_64 > > >> At least on my notebook it did not happen. I've started an UML yesterday > >> suspended it and after more than 12h it worked fine today. > >> > >> BTW: Do you see the issue also then freezing UML using the freezer cgroup? > > > > I'm not sure what do you mean by this. Do I need to enable some special > > configs for this in the host or uml kernel? > > Create on the host side a new freezer cgroup, put UML into it and freeze/thaw > it. > i.e. mkdir /sys/fs/cgroup/freezer/uml ; echo > > /sys/fs/cgroup/freezer/uml/tasks. > In the said shell run UML and then freeze it using echo FROZEN > > /sys/fs/cgroup/freezer/uml/freezer.state. > Later thaw it: echo THAWED > /sys/fs/cgroup/freezer/uml/freezer.state > I'll try this. Thanks for this tip. with kind regards thomas -- Comprehensive Server Monitoring with Site24x7. Monitor 10 servers for $9/Month. Get alerted through email, SMS, voice calls or mobile push notifications. Take corrective actions from your mobile device. http://p.sf.net/sfu/Zoho ___ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
Re: [uml-devel] kernel stalls in balance_dirty_pages_ratelimited()
Am Sonntag, den 19.10.2014, 21:35 +0200 schrieb Thomas Meyer:
> Am Sonntag, den 19.10.2014, 17:02 +0100 schrieb Anton Ivanov:
> > On 19/10/14 15:59, Thomas Meyer wrote:
> > > Am Dienstag, den 14.10.2014, 08:31 +0100 schrieb Anton Ivanov:
> > >> I see a very similar stall on writeout to ubd with my patches (easy) and
> > >> without (difficult - takes running an IO soak for a few days).
> > >>
> > >> It stalls (usually) when trying to flush the journal file of ext4.
> > > any ideas?
> >
> > I had some suspicion of a race somewhere in the UML VM subsystem. I
> > sprinked barrier() all over it, nope not the case.
> >
I added this patch to the uml kernel:
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 82e7db7..7f35fa4 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -241,6 +241,10 @@ static inline void __inc_zone_state(struct zone *zone,
enum zone_stat_item item)
static inline void __dec_zone_state(struct zone *zone, enum zone_stat_item
item)
{
atomic_long_dec(&zone->vm_stat[item]);
+ if (&vm_stat[item] == &vm_stat[NR_FILE_DIRTY] &&
+ atomic_long_read(&vm_stat[item]) < 0) {
+ asm("int3");
+ }
atomic_long_dec(&vm_stat[item]);
}
And this is the backtrace leading to the negative nr_dirty value:
Program received signal SIGTRAP, Trace/breakpoint trap.
__dec_zone_state (item=, zone=) at
include/linux/vmstat.h:248
(gdb) bt
#0 __dec_zone_state (item=, zone=) at
include/linux/vmstat.h:248
#1 __dec_zone_page_state (item=, page=) at
include/linux/vmstat.h:260
#2 clear_page_dirty_for_io (page=0x628b7308) at mm/page-writeback.c:2333
#3 0x60188c36 in mpage_submit_page (mpd=0x808ebb90, page=) at fs/ext4/inode.c:1785
#4 0x6018917e in mpage_map_and_submit_buffers (mpd=0x808ebb90) at
fs/ext4/inode.c:1981
#5 0x6018d64a in mpage_map_and_submit_extent
(give_up_on_write=, mpd=, handle=)
at fs/ext4/inode.c:2123
#6 ext4_writepages (mapping=, wbc=) at
fs/ext4/inode.c:2428
#7 0x600f0838 in do_writepages (mapping=,
wbc=) at mm/page-writeback.c:2043
#8 0x60143d29 in __writeback_single_inode (inode=0x75e191a8,
wbc=0x808ebcb8) at fs/fs-writeback.c:461
#9 0x60144c00 in writeback_sb_inodes (sb=,
wb=0x80a92330, work=0x808ebe00) at fs/fs-writeback.c:688
#10 0x60144e0e in __writeback_inodes_wb (wb=0x808eb990,
work=0x628b7308) at fs/fs-writeback.c:733
#11 0x60144f8d in wb_writeback (wb=0x80a92330, work=0x808ebe00) at
fs/fs-writeback.c:864
#12 0x60145375 in wb_check_old_data_flush (wb=) at
fs/fs-writeback.c:979
#13 wb_do_writeback (wb=) at fs/fs-writeback.c:1014
#14 bdi_writeback_workfn (work=0x808eb990) at fs/fs-writeback.c:1044
#15 0x600690a2 in process_one_work (worker=0x808c3700, work=0x80a92340)
at kernel/workqueue.c:2023
#16 0x60069b5e in worker_thread (__worker=0x808eb990) at
kernel/workqueue.c:2155
#17 0x6006dd9f in kthread (_create=0x80822040) at kernel/kthread.c:207
#18 0x6003ab59 in new_thread_handler () at arch/um/kernel/process.c:129
#19 0x in ?? ()
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