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

[Jens Axboe <axboe@kernel.dk>]

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.

-- 
Jens Axboe