On 6/6/20 9:12 AM, Xiaoguang Wang wrote:
> While testing io_uring in our internal kernel, note it's not upstream
> kernel, we see below panic:
> [ 872.498723] x29: ffff00002d553cf0 x28: 0000000000000000
> [ 872.508973] x27: ffff807ef691a0e0 x26: 0000000000000000
> [ 872.519116] x25: 0000000000000000 x24: ffff0000090a7980
> [ 872.529184] x23: ffff000009272060 x22: 0000000100022b11
> [ 872.539144] x21: 0000000046aa5668 x20: ffff80bee8562b18
> [ 872.549000] x19: ffff80bee8562080 x18: 0000000000000000
> [ 872.558876] x17: 0000000000000000 x16: 0000000000000000
> [ 872.568976] x15: 0000000000000000 x14: 0000000000000000
> [ 872.578762] x13: 0000000000000000 x12: 0000000000000000
> [ 872.588474] x11: 0000000000000000 x10: 0000000000000c40
> [ 872.598324] x9 : ffff000008100c00 x8 : 000000007ffff000
> [ 872.608014] x7 : ffff80bee8562080 x6 : ffff80beea862d30
> [ 872.617709] x5 : 0000000000000000 x4 : ffff80beea862d48
> [ 872.627399] x3 : ffff80bee8562b18 x2 : 0000000000000000
> [ 872.637044] x1 : ffff0000090a7000 x0 : 0000000000208040
> [ 872.646575] Call trace:
> [ 872.653139] task_numa_work+0x4c/0x310
> [ 872.660916] task_work_run+0xb0/0xe0
> [ 872.668400] io_sq_thread+0x164/0x388
> [ 872.675829] kthread+0x108/0x138
>
> The reason is that once io_sq_thread has a valid mm, schedule subsystem
> may call task_tick_numa() adding a task_numa_work() callback, which will
> visit mm, then above panic will happen.>
> To fix this bug, only call task_work_run() before dropping mm.
That's a bug outside of io_uring, you'll want to backport this patch
from 5.7:
commit 18f855e574d9799a0e7489f8ae6fd8447d0dd74a
Author: Jens Axboe <axboe@xxxxxxxxx>
Date: Tue May 26 09:38:31 2020 -0600
sched/fair: Don't NUMA balance for kthreads
--
Jens Axboe
