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

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Date:   Tue, 9 Feb 2021 20:02:11 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>,
        syzbot <syzbot+695b03d82fa8e4901b06@...kaller.appspotmail.com>,
        io-uring@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        viro@...iv.linux.org.uk
Subject: Re: INFO: task hung in io_uring_cancel_task_requests

On 2/9/21 7:57 PM, Pavel Begunkov wrote:
> On 10/02/2021 00:54, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    dd86e7fa Merge tag 'pci-v5.11-fixes-2' of git://git.kernel..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=13e43f90d00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=e83e68d0a6aba5f6
>> dashboard link: https://syzkaller.appspot.com/bug?extid=695b03d82fa8e4901b06
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1490f0d4d00000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17aedf1cd00000
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+695b03d82fa8e4901b06@...kaller.appspotmail.com
> 
> It looks like SQPOLL. I wonder if that's due to parked SQPOLL task that
> won't be able to do task_work run, and so reap poll-cancelled requests
> killed by io_put_deferred().
> 
> I'll test it out tomorrow.

It is indeed SQPOLL. From a quick look, it's doing a POLL_ADD on the ring
fd itself.

-- 
Jens Axboe