Messages in this thread | | | From | Sumit Garg <> | Subject | [RFC Patch v1 0/4] arm64: Introduce new IPI as IPI_CALL_NMI_FUNC | Date | Fri, 24 Apr 2020 16:39:10 +0530 |
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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(-)
-- 2.7.4
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