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

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

On Tue, Nov 9, 2021 at 9:47 PM Jens Axboe wrote:
> On 11/8/21 10:44 PM, Ammar Faizi wrote:
>> 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.
>
> This one is still triggering in the current tree, I'd prefer waiting with
> queueing it up until it's fixed. I can park it in another branch until
> that happens.
>

Understand, thanks!

-- 
Ammar Faizi