From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org
Cc: syzbot+e3a3f84f5cecf61f0583@syzkaller.appspotmail.com
Subject: Re: [PATCH 5.12] io_uring: do ctx sqd ejection in a clear context
Date: Wed, 24 Mar 2021 06:55:36 -0600 [thread overview]
Message-ID: <e6444da0-ba50-e5ff-bcd8-90bf140b6c49@kernel.dk> (raw)
In-Reply-To: <e90df88b8ff2cabb14a7534601d35d62ab4cb8c7.1616496707.git.asml.silence@gmail.com>
On 3/23/21 4:52 AM, Pavel Begunkov wrote:
> WARNING: CPU: 1 PID: 27907 at fs/io_uring.c:7147 io_sq_thread_park+0xb5/0xd0 fs/io_uring.c:7147
> CPU: 1 PID: 27907 Comm: iou-sqp-27905 Not tainted 5.12.0-rc4-syzkaller #0
> RIP: 0010:io_sq_thread_park+0xb5/0xd0 fs/io_uring.c:7147
> Call Trace:
> io_ring_ctx_wait_and_kill+0x214/0x700 fs/io_uring.c:8619
> io_uring_release+0x3e/0x50 fs/io_uring.c:8646
> __fput+0x288/0x920 fs/file_table.c:280
> task_work_run+0xdd/0x1a0 kernel/task_work.c:140
> io_run_task_work fs/io_uring.c:2238 [inline]
> io_run_task_work fs/io_uring.c:2228 [inline]
> io_uring_try_cancel_requests+0x8ec/0xc60 fs/io_uring.c:8770
> io_uring_cancel_sqpoll+0x1cf/0x290 fs/io_uring.c:8974
> io_sqpoll_cancel_cb+0x87/0xb0 fs/io_uring.c:8907
> io_run_task_work_head+0x58/0xb0 fs/io_uring.c:1961
> io_sq_thread+0x3e2/0x18d0 fs/io_uring.c:6763
> ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
>
> May happen that last ctx ref is killed in io_uring_cancel_sqpoll(), so
> fput callback (i.e. io_uring_release()) is enqueued through task_work,
> and run by same cancellation. As it's deeply nested we can't do parking
> or taking sqd->lock there, because its state is unclear. So avoid
> ctx ejection from sqd list from io_ring_ctx_wait_and_kill() and do it
> in a clear context in io_ring_exit_work().
Applied, thanks.
--
Jens Axboe
prev parent reply other threads:[~2021-03-24 12:56 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-23 10:52 [PATCH 5.12] io_uring: do ctx sqd ejection in a clear context Pavel Begunkov
2021-03-24 12:55 ` Jens Axboe [this message]
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