On Sat, 25 Apr 2020 at 02:20, Doug Anderson <diand...@chromium.org> wrote: > > Hi, > > On Fri, Apr 24, 2020 at 4:11 AM Sumit Garg <sumit.g...@linaro.org> wrote: > > > > With pseudo NMIs support available its possible to configure SGIs to be > > triggered as pseudo NMIs running in NMI context. And kernel features > > such as kgdb relies on NMI support to round up CPUs which are stuck in > > hard lockup state with interrupts disabled. > > > > This patch-set adds support for IPI_CALL_NMI_FUNC which can be triggered > > as a pseudo NMI which in turn is leveraged via kgdb to round up CPUs. > > > > After this patch-set we should be able to get a backtrace for a CPU > > stuck in HARDLOCKUP. Have a look at an example below from a testcase run > > on Developerbox: > > > > $ echo HARDLOCKUP > /sys/kernel/debug/provoke-crash/DIRECT > > > > # Enter kdb via Magic SysRq > > > > [11]kdb> btc > > btc: cpu status: Currently on cpu 11 > > Available cpus: 0-10(I), 11, 12(I), 13, 14-23(I) > > <snip> > > Stack traceback for pid 623 > > 0xffff00086a644600 623 622 1 13 R 0xffff00086a644fc0 bash > > CPU: 13 PID: 623 Comm: bash Not tainted 5.7.0-rc2 #27 > > Hardware name: Socionext SynQuacer E-series DeveloperBox, BIOS build #73 > > Apr 6 2020 > > Call trace: > > dump_backtrace+0x0/0x198 > > show_stack+0x18/0x28 > > dump_stack+0xb8/0x100 > > kgdb_cpu_enter+0x5c0/0x5f8 > > kgdb_nmicallback+0xa0/0xa8 > > handle_IPI+0x190/0x200 > > gic_handle_irq+0x2b8/0x2d8 > > el1_irq+0xcc/0x180 > > lkdtm_HARDLOCKUP+0x8/0x18 > > direct_entry+0x124/0x1c0 > > full_proxy_write+0x60/0xb0 > > __vfs_write+0x1c/0x48 > > vfs_write+0xe4/0x1d0 > > ksys_write+0x6c/0xf8 > > __arm64_sys_write+0x1c/0x28 > > el0_svc_common.constprop.0+0x74/0x1f0 > > do_el0_svc+0x24/0x90 > > el0_sync_handler+0x178/0x2b8 > > el0_sync+0x158/0x180 > > <snip> > > > > Looking forward to your comments/feedback. > > > > Sumit Garg (4): > > arm64: smp: Introduce a new IPI as IPI_CALL_NMI_FUNC > > irqchip/gic-v3: Add support to handle SGI as pseudo NMI > > irqchip/gic-v3: Enable arch specific IPI as pseudo NMI > > arm64: kgdb: Round up cpus using IPI_CALL_NMI_FUNC > > > > arch/arm64/include/asm/hardirq.h | 2 +- > > arch/arm64/include/asm/smp.h | 1 + > > arch/arm64/kernel/kgdb.c | 15 +++++++++++++++ > > arch/arm64/kernel/smp.c | 36 +++++++++++++++++++++++++++++++++++- > > drivers/irqchip/irq-gic-v3.c | 36 +++++++++++++++++++++++++++++++----- > > 5 files changed, 83 insertions(+), 7 deletions(-) > > This is amazing! > > * picked your patches back to my current 5.4 tree > * turned on "CONFIG_ARM64_PSEUDO_NMI" > * set the "irqchip.gicv3_pseudo_nmi=1" command line > > ...and bam I can trace on the locked up CPU instead of being left in the dark. > > I'm not sure I'm going to be too much use in actually doing the review > of the code since I'm not really an expert at how SGIs work (it took > me a while to realize that it must stand for software generated > interrupts) nor the bowels of the GIC. I tried to do what little > review I could. > > In any case, I'll keep this in my local patch stack for now and keep > testing it to make sure I don't notice any weird problems.
Thanks for your review and testing. -Sumit > > -Doug _______________________________________________ Kgdb-bugreport mailing list Kgdb-bugreport@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kgdb-bugreport
