On 13/04/2021 11:43, Pavel Begunkov wrote:
> [ 245.463317] INFO: task iou-sqp-1374:1377 blocked for more than 122 seconds.
> [ 245.463334] task:iou-sqp-1374 state:D flags:0x00004000
> [ 245.463345] Call Trace:
> [ 245.463352] __schedule+0x36b/0x950
> [ 245.463376] schedule+0x68/0xe0
> [ 245.463385] __io_uring_cancel+0xfb/0x1a0
> [ 245.463407] do_exit+0xc0/0xb40
> [ 245.463423] io_sq_thread+0x49b/0x710
> [ 245.463445] ret_from_fork+0x22/0x30
>
> It happens when sqpoll forgot to run park_task_work and goes to exit,
> then exiting user may remove ctx from sqd_list, and so corresponding
> io_sq_thread() -> io_uring_cancel_sqpoll() won't be executed. Hopefully
> it just stucks in do_exit() in this case.
fwiw, it's actually a 5.12 problem and I have a reliable enough
way to reproduce it.
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Joakim Hassila <joj@xxxxxxx>
> Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
> ---
> fs/io_uring.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index cadd7a65a7f4..f390914666b1 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -6817,6 +6817,9 @@ static int io_sq_thread(void *data)
> current->flags |= PF_NO_SETAFFINITY;
>
> mutex_lock(&sqd->lock);
> + /* a user may had exited before the thread wstarted */
> + io_run_task_work_head(&sqd->park_task_work);
> +
> while (!test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state)) {
> int ret;
> bool cap_entries, sqt_spin, needs_sched;
> @@ -6833,10 +6836,10 @@ static int io_sq_thread(void *data)
> }
> cond_resched();
> mutex_lock(&sqd->lock);
> - if (did_sig)
> - break;
> io_run_task_work();
> io_run_task_work_head(&sqd->park_task_work);
> + if (did_sig)
> + break;
> timeout = jiffies + sqd->sq_thread_idle;
> continue;
> }
>
--
Pavel Begunkov
