Pavel Begunkov 1d5f5ea7cb io-wq: remove worker to owner tw dependency
INFO: task iou-wrk-6609:6612 blocked for more than 143 seconds.
      Not tainted 5.15.0-rc5-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:iou-wrk-6609    state:D stack:27944 pid: 6612 ppid:  6526 flags:0x00004006
Call Trace:
 context_switch kernel/sched/core.c:4940 [inline]
 __schedule+0xb44/0x5960 kernel/sched/core.c:6287
 schedule+0xd3/0x270 kernel/sched/core.c:6366
 schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1857
 do_wait_for_common kernel/sched/completion.c:85 [inline]
 __wait_for_common kernel/sched/completion.c:106 [inline]
 wait_for_common kernel/sched/completion.c:117 [inline]
 wait_for_completion+0x176/0x280 kernel/sched/completion.c:138
 io_worker_exit fs/io-wq.c:183 [inline]
 io_wqe_worker+0x66d/0xc40 fs/io-wq.c:597
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

io-wq worker may submit a task_work to the master task and upon
io_worker_exit() wait for the tw to get executed. The problem appears
when the master task is waiting in coredump.c:

468                     freezer_do_not_count();
469                     wait_for_completion(&core_state->startup);
470                     freezer_count();

Apparently having some dependency on children threads getting everything
stuck. Workaround it by cancelling the taks_work callback that causes it
before going into io_worker_exit() waiting.

p.s. probably a better option is to not submit tw elevating the refcount
in the first place, but let's leave this excercise for the future.

Cc: stable@vger.kernel.org
Reported-and-tested-by: syzbot+27d62ee6f256b186883e@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/142a716f4ed936feae868959059154362bfa8c19.1635509451.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-10-29 09:49:33 -06:00
..
2021-10-07 11:20:08 -07:00
2021-08-19 09:02:55 +09:00
2021-04-12 15:04:29 +02:00
2021-07-06 11:06:04 -07:00
2021-09-02 12:32:12 -07:00
2021-09-07 12:18:29 -07:00
2021-08-26 22:28:02 +02:00
2021-10-07 10:18:36 -05:00
2021-09-22 09:21:02 -07:00
2021-09-04 10:25:26 -07:00
2021-09-10 09:46:48 -07:00
2021-06-30 12:21:16 -07:00
2021-09-03 15:33:47 -07:00
2021-08-16 10:50:32 -06:00
2021-08-19 09:02:55 +09:00
2021-10-18 06:17:36 -06:00
2021-08-31 11:13:35 -07:00
2021-10-18 06:17:35 -06:00
2021-09-09 13:25:49 -07:00
2021-09-11 14:48:42 -07:00
2021-10-19 05:49:54 -06:00
2021-08-31 11:06:32 -07:00
2021-06-29 10:53:48 -07:00
2021-08-18 22:08:24 +02:00
2021-08-10 17:57:22 +02:00