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

From: Haris Okanovic
Date: Thu Apr 12 2018 - 11:00:46 EST


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