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@vger.kernel.org Reported-by: Joakim Hassila joj@mac.com Signed-off-by: Pavel Begunkov asml.silence@gmail.com

---

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;
  

  }