Re: [PATCH v6 liburing] test: Add kworker-hang test

[Ammar Faizi <ammar.faizi@students.amikom.ac.id>]

On Sat, Nov 6, 2021 at 6:49 PM Ammar Faizi wrote:
>
> This is the reproducer for the kworker hang bug.
>
> Reproduction Steps:
>   1) A user task calls io_uring_queue_exit().
>
>   2) Suspend the task with SIGSTOP / SIGTRAP before the ring exit is
>      finished (do it as soon as step (1) is done).
>
>   3) Wait for `/proc/sys/kernel/hung_task_timeout_secs` seconds
>      elapsed.
>
>   4) We get a complaint from the khungtaskd because the kworker is
>      stuck in an uninterruptible state (D).
>
> The kworkers waiting on ring exit are not progressing as the task
> cannot proceed. When the user task is continued (e.g. get SIGCONT
> after SIGSTOP, or continue after SIGTRAP breakpoint), the kworkers
> then can finish the ring exit.
>
> We need a special handling for this case to avoid khungtaskd
> complaint. Currently we don't have the fix for this.
[...]
> Cc: Pavel Begunkov <asml.silence@gmail.com>
> Link: https://github.com/axboe/liburing/issues/448
> Signed-off-by: Ammar Faizi <ammar.faizi@students.amikom.ac.id>
> ---
>
>  v6:
>    - Fix missing call to restore_hung_entries() when fork() fails.
>
>  .gitignore          |   1 +
>  test/Makefile       |   1 +
>  test/kworker-hang.c | 323 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 325 insertions(+)
>  create mode 100644 test/kworker-hang.c

It's ready for review.

-- 
Ammar Faizi