Re: [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed_work

[Jarek Poplawski <jarkao2@o2.pl>]

On Thu, Apr 19, 2007 at 01:07:11PM -0400, Chuck Ebbert wrote:
> Jarek Poplawski wrote:
> > Hi,
> > 
> > IMHO cancel_rearming_delayed_work is dangerous place:
> > 
> > - it assumes a work function always rearms (with no exception),
> > which probably isn't explained enough now (but anyway should
> > be checked in such loops);
> > 
> > - probably possible (theoretical) scenario: a few work
> > functions rearm themselves with very short, equal times;
> > before flush_workqueue ends, their timers are already
> > fired, so cancel_delayed_work has nothing to do.
> > 
> > Maybe this patch could check, if I'm not dreaming...
> > 
> > PS: of course the counter value below is a question of taste
> 
> Okay, an easy test for it: insmod netconsole ; rmmod netconsole
> 
> In 2.6.20.x it loops forever and cancel_rearming_delayed_work()
> is part of the trace...
 
Sure, but the dreaming test is more needed for the second
point - I mean - if it's theoretical only? The first scenario
is in my opinion assured logically - there was only a question,
whether it could be detected by other means - and it seems not.

Cheers,
Jarek P.