Re: [syzbot] possible deadlock in worker_thread

[Fabio M. De Francesco]

On lunedì 14 febbraio 2022 04:44:25 CET Tejun Heo wrote:
> Hello,
> 
> On Mon, Feb 14, 2022 at 10:08:00AM +0900, Tetsuo Handa wrote:
> > +	destroy_workqueue(srp_tl_err_wq);
> > 
> > Then, we can call WARN_ON() if e.g. flush_workqueue() is called on system-wide workqueues.
> 
> Yeah, this is the right thing to do. It makes no sense at all to call
> flush_workqueue() on the shared workqueues as the caller has no idea what
> it's gonna end up waiting for. It was on my todo list a long while ago but
> slipped through the crack. If anyone wanna take a stab at it (including
> scrubbing the existing users, of course), please be my guest.
> 

Just to think and understand... what if the system-wide WQ were allocated as unbound 
ordered (i.e., as in alloc_ordered_workqueue()) with "max_active" of one?

1) Would it solve the locks dependency problem?
2) Would it introduce performance penalties (bottlenecks)?

Greetings,

Fabio

>
> Thanks.
> 
> -- 
> tejun
>