linux-kernel - Re: INFO: task hung in io_uring_cancel

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Date:   Mon, 3 May 2021 11:45:26 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Palash Oswal <oswalpalash@...il.com>
Cc:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        syzbot+11bf59db879676f59e52@...kaller.appspotmail.com
Subject: Re: INFO: task hung in io_uring_cancel_sqpoll

On 5/3/21 5:41 AM, Palash Oswal wrote:
> On Mon, May 3, 2021 at 3:42 AM Pavel Begunkov <asml.silence@...il.com> wrote:
>> The test might be very useful. Would you send a patch to
>> liburing? Or mind the repro being taken as a test?
> 
> Pavel,
> 
> I'm working on a PR for liburing with this test. Do you know how I can

Perfect, thanks

> address this behavior?

As the hang is sqpoll cancellations, it's most probably
fixed in 5.13 + again awaits to be taken for stable.

Don't know about segfaults, but it was so for long, and
syz reproducers are ofthen faults for me, and exit with 0
in the end. So, I wouldn't worry about it.

> root@...kaller:~/liburing/test# ./runtests.sh sqpoll-cancel-hang
> Running test sqp[   15.310997] Running test sqpoll-cancel-hang:
> oll-cancel-hang:
> [   15.333348] sqpoll-cancel-h[305]: segfault at 0 ip 000055ad00e265e3 sp]
> [   15.334940] Code: 89 d8 8d 34 90 8b 45 04 ba 03 00 00 00 c1 e0 04 03 46
> All tests passed
> 
> root@...kaller:~/liburing/test# ./sqpoll-cancel-hang
> [   13.572639] sqpoll-cancel-h[298]: segfault at 0 ip 00005634c4a455e3 sp]
> [   13.576506] Code: 89 d8 8d 34 90 8b 45 04 ba 03 00 00 00 c1 e0 04 03 46
> [   23.350459] random: crng init done
> [   23.352837] random: 7 urandom warning(s) missed due to ratelimiting
> [  243.090865] INFO: task iou-sqp-298:299 blocked for more than 120 secon.
> [  243.095187]       Not tainted 5.12.0 #142
> [  243.099800] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disable.
> [  243.105928] task:iou-sqp-298     state:D stack:    0 pid:  299 ppid:  4
> [  243.111044] Call Trace:
> [  243.112855]  __schedule+0xb1d/0x1130
> [  243.115549]  ? __sched_text_start+0x8/0x8
> [  243.118328]  ? io_wq_worker_sleeping+0x145/0x500
> [  243.121790]  schedule+0x131/0x1c0
> [  243.123698]  io_uring_cancel_sqpoll+0x288/0x350
> [  243.125977]  ? io_sq_thread_unpark+0xd0/0xd0
> [  243.128966]  ? mutex_lock+0xbb/0x130
> [  243.132572]  ? init_wait_entry+0xe0/0xe0
> [  243.135429]  ? wait_for_completion_killable_timeout+0x20/0x20
> [  243.138303]  io_sq_thread+0x174c/0x18c0
> [  243.140162]  ? io_rsrc_put_work+0x380/0x380
> [  243.141613]  ? init_wait_entry+0xe0/0xe0
> [  243.143686]  ? _raw_spin_lock_irq+0xa5/0x180
> [  243.145619]  ? _raw_spin_lock_irqsave+0x190/0x190
> [  243.147671]  ? calculate_sigpending+0x6b/0xa0
> [  243.149036]  ? io_rsrc_put_work+0x380/0x380
> [  243.150694]  ret_from_fork+0x22/0x30
> 
> Palash
> 

-- 
Pavel Begunkov