linux-kernel - Re: [syzbot] INFO: task hung in io_ring_exit

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Date:   Thu, 08 Apr 2021 07:42:12 -0700
From:   syzbot <syzbot+93f72b3885406bb09e0d@...kaller.appspotmail.com>
To:     asml.silence@...il.com, axboe@...nel.dk, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] INFO: task hung in io_ring_exit_work

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in io_ring_exit_work

INFO: task kworker/u4:0:9 blocked for more than 143 seconds.
      Not tainted 5.12.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:0    state:D stack:26056 pid:    9 ppid:     2 flags:0x00004000
Workqueue: events_unbound io_ring_exit_work
Call Trace:
 context_switch kernel/sched/core.c:4324 [inline]
 __schedule+0x911/0x21b0 kernel/sched/core.c:5075
 schedule+0xcf/0x270 kernel/sched/core.c:5154
 schedule_timeout+0x1db/0x250 kernel/time/timer.c:1868
 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+0x168/0x270 kernel/sched/completion.c:138
 io_ring_exit_work+0x4e8/0x12d0 fs/io_uring.c:8616
 process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
INFO: task kworker/u4:1:25 blocked for more than 143 seconds.
      Not tainted 5.12.0-rc2-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:1    state:D stack:25560 pid:   25 ppid:     2 flags:0x00004000
Workqueue: events_unbound io_ring_exit_work
Call Trace:
 context_switch kernel/sched/core.c:4324 [inline]
 __schedule+0x911/0x21b0 kernel/sched/core.c:5075
 schedule+0xcf/0x270 kernel/sched/core.c:5154
 schedule_timeout+0x14a/0x250 kernel/time/timer.c:1892


Tested on:

commit:         a2a68d4c io_uring: signalling fun / syz test
git tree:       https://github.com/isilence/linux.git syz_test3
console output: https://syzkaller.appspot.com/x/log.txt?x=12eed711d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=86318203e865a02b
dashboard link: https://syzkaller.appspot.com/bug?extid=93f72b3885406bb09e0d
compiler: