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SubjectRe: [PATCH] tty/vt: Touch NMI watchdog in vt_console_print
On Fri, Sep 20, 2019 at 04:57:26PM +0800, Qiujun Huang wrote:
> vt_console_print could trigger NMI watchdog in case writing slow:
>
> [2858736.789664] NMI watchdog: Watchdog detected hard LOCKUP on cpu 23
> ...
> [2858736.790194] CPU: 23 PID: 32504 Comm: tensorflow_mode Not tainted 4.4.131-1.el7.elrepo.x86_64 #1
> [2858736.790206] Hardware name: Huawei RH2288 V3/BC11HGSB0, BIOS 3.57 02/26/2017
> [2858736.790222] task: ffff881e0a191640 ti: ffff881fd73a8000 task.ti: ffff881fd73a8000
> [2858736.790358] RIP: 0010:[<ffffffff810cc06e>] [<ffffffff810cc06e>] native_queued_spin_lock_slowpath+0x15e/0x170
> [2858736.790363] RSP: 0018:ffff88203f043db0 EFLAGS: 00000002
> [2858736.790365] RAX: 00000000005c0101 RBX: 0000000000000246 RCX: 0000000000000001
> ...
> [2858736.790452] Call Trace:
> [2858736.790521] <IRQ>
> [2858736.790521] [<ffffffff8118ab28>] queued_spin_lock_slowpath+0xb/0xf
> [2858736.790552] [<ffffffff8170eca7>] _raw_spin_lock_irqsave+0x37/0x40
> [2858736.790653] [<ffffffff814c80a4>] scsi_end_request+0x104/0x1d0
> [2858736.790656] [<ffffffff814c9e13>] scsi_io_completion+0x153/0x650
> [2858736.790671] [<ffffffff814c1092>] scsi_finish_command+0xd2/0x120
> [2858736.790673] [<ffffffff814c9607>] scsi_softirq_done+0x127/0x150
> [2858736.790749] [<ffffffff8131973e>] blk_done_softirq+0x8e/0xc0
> [2858736.790811] [<ffffffff810857db>] __do_softirq+0xeb/0x2f0
> [2858736.790813] [<ffffffff81085c85>] irq_exit+0xf5/0x100
> [2858736.790867] [<ffffffff81051819>] smp_call_function_single_interrupt+0x39/0x40
> [2858736.790890] [<ffffffff8171055b>] call_function_single_interrupt+0x9b/0xa0
> [2858736.790973] <EOI>
> ...
>
> PID: 1793 TASK: ffff88103445c2c0 CPU: 32 COMMAND: "java"
> #0 [ffff88103fe88e38] crash_nmi_callback at ffffffff810504d7
> #1 [ffff88103fe88e48] nmi_handle at ffffffff8101c1f7
> #2 [ffff88103fe88ea0] default_do_nmi at ffffffff8101c7d0
> #3 [ffff88103fe88ec0] do_nmi at ffffffff8101c901
> #4 [ffff88103fe88ee8] end_repeat_nmi at ffffffff8171176a
> [exception RIP: cfb_imageblit+1167]
> RIP: ffffffff813bdf8f RSP: ffff880006823380 RFLAGS: 00000046
> RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000005
> RDX: 000000000000024d RSI: 00000000ff000000 RDI: 0000000000000001
> RBP: ffff8800068233f0 R8: ffffffff81785e80 R9: ffffc9000c843168
> R10: 0000000000000001 R11: 0000000000000000 R12: ffff882037a831ba
> R13: ffff882037a831af R14: ffffc9000c84316c R15: ffffc9000c843000
> ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
> --- <NMI exception stack> ---
> #5 [ffff880006823380] cfb_imageblit at ffffffff813bdf8f
> #6 [ffff880006823398] bit_putcs at ffffffff813b2307
> #7 [ffff8800068234d0] bit_cursor at ffffffff813b1fc8
> #8 [ffff8800068235f0] fbcon_scroll at ffffffff813aebda
> #9 [ffff880006823650] scrup at ffffffff81442600
> ...
>
> the cpu23 wait for the same blk queue_lock

Why is this acting "slow"?

Do we want to sprinkle this type of call everywhere in the console layer
(hint, I doubt it.)

This feels like something odd is wrong with your system, not with the
tty layer...

thanks,

greg k-h

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