linux-kernel - Re: [PATCH v4 1/2] timers: Don't wake ktimersoftd on every tick

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Date:   Thu, 12 Apr 2018 10:00:29 -0500
From:   Haris Okanovic <haris.okanovic@...com>
To:     Mike Galbraith <efault@....de>
Cc:     linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] timers: Don't wake ktimersoftd on every tick

Hi Mike,

I haven't tested the patch with wireshark until now. My system also 
hangs shortly after it starts. I'm pretty sure I hit workqueues in my 
earlier tests via the block driver, but it's clearly not whatever 
wireshark is using. I'll look at it and try to post a fix. CCing the 
list to avoid this patch until then.

Thanks,
Haris


On 04/09/2018 11:02 PM, Mike Galbraith wrote:
> Hi,
> 
> Are these patches dead, or are you planning another submission?  I ask
> because I discovered that with them applied, firing up wireshark hangs
> the box 100% repeatably, with wireshark never fully initializing.
> 
> Applying them to an otherwise virgin 4.14.20-rt17 to be sure...
> 
> crash> bt 6016PID: 6016   TASK: ffff95dd68572180  CPU: 2   COMMAND:
> "dumpcap"
>   #0 [ffffb490094f3bc0] __schedule at ffffffffa56d55b9
>   #1 [ffffb490094f3c40] schedule at ffffffffa56d5a03
>   #2 [ffffb490094f3c58] schedule_timeout at ffffffffa56d8467
>   #3 [ffffb490094f3cd8] wait_for_completion at ffffffffa56d6e34
>   #4 [ffffb490094f3d18] __wait_rcu_gp at ffffffffa50e59cd
>   #5 [ffffb490094f3d58] synchronize_rcu at ffffffffa50ec14e
>   #6 [ffffb490094f3d98] packet_set_ring at ffffffffc0c74da0 [af_packet]
>   #7 [ffffb490094f3e50] packet_setsockopt at ffffffffc0c75d23 [af_packet]
>   #8 [ffffb490094f3ef8] sys_setsockopt at ffffffffa558a5e2
>   #9 [ffffb490094f3f30] do_syscall_64 at ffffffffa5001b05
> #10 [ffffb490094f3f50] entry_SYSCALL_64_after_hwframe at ffffffffa5800065
>      RIP: 00007f3107a1cfaa  RSP: 00007ffc9745c2e8  RFLAGS: 00000246
>      RAX: ffffffffffffffda  RBX: 0000000000000001  RCX: 00007f3107a1cfaa
>      RDX: 0000000000000005  RSI: 0000000000000107  RDI: 0000000000000003
>      RBP: 000055ae1d8eb470   R8: 000000000000001c   R9: 0000000000000002
>      R10: 00007ffc9745c350  R11: 0000000000000246  R12: 00007ffc9745c350
>      R13: 0000000000000000  R14: 000055ae1d8eb200  R15: 000055ae1d8eb2d0
>      ORIG_RAX: 0000000000000036  CS: 0033  SS: 002b
> crash> dmesg
> ...
> [  483.808197] BUG: workqueue lockup - pool cpus=2 node=0 flags=0x0 nice=0 stuck for 52s!
> [  483.808204] Showing busy workqueues and worker pools:
> [  483.808206] workqueue events: flags=0x0
> [  483.808208]   pwq 4: cpus=2 node=0 flags=0x0 nice=0 active=1/256
> [  483.808211]     pending: check_corruption
> [  492.695124] sysrq: SysRq : Trigger a crash
>