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Date:   Sat, 2 Apr 2022 10:22:08 +0800
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Subject: Re: Question about kill a process group
From:   Zhang Qiao <zhangqiao22@huawei.com>
To:     lkml <linux-kernel@vger.kernel.org>
CC:     <ebiederm@xmission.com>
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ping...

Any suggestions for this problem？

thank!
Qiao


在 2022/3/29 16:07, Zhang Qiao 写道:
> hello everyone,
> 
> I got a hradlockup panic when run the ltp syscall testcases.
> 
> 348439.713178] NMI watchdog: Watchdog detected hard LOCKUP on cpu 32
> [348439.713236] irq event stamp: 0
> [348439.713237] hardirqs last  enabled at (0): [<0000000000000000>] 0x0
> [348439.713238] hardirqs last disabled at (0): [<ffffffff87cd1ea5>] copy_process+0x7f5/0x2160
> [348439.713239] softirqs last  enabled at (0): [<ffffffff87cd1ea5>] copy_process+0x7f5/0x2160
> [348439.713240] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [348439.713241] CPU: 32 PID: 1151212 Comm: fork12 Kdump: loaded Tainted: G S                5.10.0+ #1
> [348439.713242] Hardware name: Huawei RH2288H V3/BC11HGSA0, BIOS 3.35 10/20/2016
> [348439.713243] RIP: 0010:queued_write_lock_slowpath+0x4d/0x80
> [348439.713245] RSP: 0018:ffffa3a6bed4fe60 EFLAGS: 00000006
> [348439.713246] RAX: 0000000000000500 RBX: ffffffff892060c0 RCX: 00000000000000ff
> [348439.713247] RDX: 0000000000000500 RSI: 0000000000000100 RDI: ffffffff892060c0
> [348439.713248] RBP: ffffffff892060c4 R08: 0000000000000001 R09: 0000000000000000
> [348439.713249] R10: ffffa3a6bed4fde8 R11: 0000000000000000 R12: ffff96dfd3b68001
> [348439.713250] R13: ffff96dfd3b68000 R14: ffff96dfd3b68c38 R15: ffff96e2cf1f51c0
> [348439.713251] FS:  0000000000000000(0000) GS:ffff96edbc200000(0000) knlGS:0000000000000000
> [348439.713252] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [348439.713253] CR2: 0000000000416ea0 CR3: 0000002d91812004 CR4: 00000000001706e0
> [348439.713254] Call Trace:
> [348439.713255]  do_raw_write_lock+0xa9/0xb0
> [348439.713256]  _raw_write_lock_irq+0x5a/0x70
> [348439.713256]  do_exit+0x429/0xd00
> [348439.713257]  do_group_exit+0x39/0xb0
> [348439.713258]  __x64_sys_exit_group+0x14/0x20
> [348439.713259]  do_syscall_64+0x33/0x40
> [348439.713260]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [348439.713260] RIP: 0033:0x7f59295a7066
> [348439.713261] Code: Unable to access opcode bytes at RIP 0x7f59295a703c.
> [348439.713262] RSP: 002b:00007fff0afeac38 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> [348439.713264] RAX: ffffffffffffffda RBX: 00007f5929694530 RCX: 00007f59295a7066
> [348439.713265] RDX: 0000000000000002 RSI: 000000000000003c RDI: 0000000000000002
> [348439.713266] RBP: 0000000000000002 R08: 00000000000000e7 R09: ffffffffffffff80
> [348439.713267] R10: 0000000000000002 R11: 0000000000000246 R12: 00007f5929694530
> [348439.713268] R13: 0000000000000001 R14: 00007f5929697f68 R15: 0000000000000000
> [348439.713269] Kernel panic - not syncing: Hard LOCKUP
> [348439.713270] CPU: 32 PID: 1151212 Comm: fork12 Kdump: loaded Tainted: G S                5.10.0+ #1
> [348439.713272] Hardware name: Huawei RH2288H V3/BC11HGSA0, BIOS 3.35 10/20/2016
> [348439.713272] Call Trace:
> [348439.713273]  <NMI>
> [348439.713274]  dump_stack+0x77/0x97
> [348439.713275]  panic+0x10c/0x2fb
> [348439.713275]  nmi_panic+0x35/0x40
> [348439.713276]  watchdog_hardlockup_check+0xeb/0x110
> [348439.713277]  __perf_event_overflow+0x52/0xf0
> [348439.713278]  handle_pmi_common+0x21a/0x320
> [348439.713286]  intel_pmu_handle_irq+0xc9/0x1b0
> [348439.713287]  perf_event_nmi_handler+0x24/0x40
> [348439.713288]  nmi_handle+0xc3/0x2a0
> [348439.713289]  default_do_nmi+0x49/0xf0
> [348439.713289]  exc_nmi+0x146/0x160
> [348439.713290]  end_repeat_nmi+0x16/0x55
> [348439.713291] RIP: 0010:queued_write_lock_slowpath+0x4d/0x80
> [348439.713293] RSP: 0018:ffffa3a6bed4fe60 EFLAGS: 00000006
> [348439.713295] RAX: 0000000000000500 RBX: ffffffff892060c0 RCX: 00000000000000ff
> [348439.713296] RDX: 0000000000000500 RSI: 0000000000000100 RDI: ffffffff892060c0
> [348439.713296] RBP: ffffffff892060c4 R08: 0000000000000001 R09: 0000000000000000
> [348439.713297] R10: ffffa3a6bed4fde8 R11: 0000000000000000 R12: ffff96dfd3b68001
> [348439.713298] R13: ffff96dfd3b68000 R14: ffff96dfd3b68c38 R15: ffff96e2cf1f51c0
> [348439.713300]  </NMI>
> [348439.713301]  do_raw_write_lock+0xa9/0xb0
> [348439.713302]  _raw_write_lock_irq+0x5a/0x70
> [348439.713303]  do_exit+0x429/0xd00
> [348439.713303]  do_group_exit+0x39/0xb0
> [348439.713304]  __x64_sys_exit_group+0x14/0x20
> [348439.713305]  do_syscall_64+0x33/0x40
> [348439.713306]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [348439.713307] RIP: 0033:0x7f59295a7066
> [348439.713308] Code: Unable to access opcode bytes at RIP 0x7f59295a703c.
> 
> 
> when analyzing vmcore, i notice lots of fork12 processes are waiting for tasklist read lock or write
> lock (see the attachment file all_cpu_stacks.log)，and every fork12 process(belongs to the same
> process group) call kill(0, SIGQUIT) in their signal handler()[1], it will traverse all the processes in the
> same process group and send signal to them one by one, which is a very time-costly work and hold tasklist
> read lock long time. At the same time, other processes will exit after receive signal, they try to get
> the tasklist write lock at exit_notify().
> 
> [1] fork12 testcase: https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/fork/fork12.c
> 
> some processes call kill(0, SIGQUIT), wait for tasklist read lock:
> 
>  #5 [ffff972a9b16fd78] native_queued_spin_lock_slowpath at ffffffff9931ed47
>  #6 [ffff972a9b16fd78] queued_read_lock_slowpath at ffffffff99320a58
>  #7 [ffff972a9b16fd90] do_wait at ffffffff992bc17d
>  #8 [ffff972a9b16fdd0] kernel_wait4 at ffffffff992bd88d
>  #9 [ffff972a9b16fe58] __do_sys_wait4 at ffffffff992bd9e5
> #10 [ffff972a9b16ff30] do_syscall_64 at ffffffff9920432d
> #11 [ffff972a9b16ff50] entry_SYSCALL_64_after_hwframe at ffffffff99c000ad
> 
> As the same time, some processes are exiting, wait for tasklist write lock:
> 
>  #5 [ffff972aa49a7e60] native_queued_spin_lock_slowpath at ffffffff9931ecb0
>  #6 [ffff972aa49a7e60] queued_write_lock_slowpath at ffffffff993209e4
>  #7 [ffff972aa49a7e78] do_raw_write_lock at ffffffff99320834
>  #8 [ffff972aa49a7e88] do_exit at ffffffff992bcd78
>  #9 [ffff972aa49a7f00] do_group_exit at ffffffff992bd719
> #10 [ffff972aa49a7f28] __x64_sys_exit_group at ffffffff992bd7a4
> #11 [ffff972aa49a7f30] do_syscall_64 at ffffffff9920432d
> #12 [ffff972aa49a7f50] entry_SYSCALL_64_after_hwframe at ffffffff99c000ad
> 
> In this scenario,there are lots of process are waiting for tasklist read lock or the tasklist
> write lock, so they will queue. if the wait queue is long enough, it might cause a hardlockup issue when a
> process wait for taking the write lock at exit_notify().
> 
> I tried to solve this problem by avoiding traversing the process group multiple times when kill(0, xxxx)
> is called multiple times form the same process group, but it doesn't look like a good solution.
> 
> Is there any good idea for fixing this problem ?
> 
> Thanks!
> 
> Qiao
> .
>