Re: [syzbot] possible deadlock in p9_write_work

[Tetsuo Handa]

On 2022/03/30 11:29, Dominique Martinet wrote:
> Tetsuo Handa wrote on Wed, Mar 30, 2022 at 10:57:15AM +0900:
>>>> Please don't use schedule_work() if you need to use flush_scheduled_work().
>>>
>>> In this case we don't call flush_scheduled_work -- ext4 does.
>>
>> Yes, that's why I changed recipients to ext4 people.
> 
> Sorry, I hadn't noticed.
> 9p is the one calling schedule_work, so ultimately it really is the
> combinaison of the two, and not just ext4 that's wrong here.

Calling schedule_work() itself does not cause troubles (unless there are
too many pending works to make progress). Calling flush_scheduled_work()
causes troubles because it waits for completion of all works even if
some of works cannot be completed due to locks held by the caller of
flush_scheduled_work(). 9p is innocent for this report.