[PATCH] drm/i915/selftests: Use preemption timeout on cleanup

[Janusz Krzysztofik]

Hi Andi,

On Tuesday, 17 December 2024 18:12:08 CET Andi Shyti wrote:
> Hi Janusz,
> 
> ...
> 
> > > > +
> > > >  		cond_resched();
> > > >  
> > > > -		if (intel_gt_wait_for_idle(gt, HZ * 3) == -ETIME) {
> > > > +		if (intel_gt_wait_for_idle(gt, HZ * timeout_ms / 500) == -
> > ETIME) {
> > > 
> > > where is this 500 coming from?
> > 
> > / 1000 would convert it to seconds as needed, and / 500 used instead was 
> > supposed to to mean that we are willing to wait for preempt_timeout_ms * 
2.  
> > Sorry for that shortcut.  Would you like me to provide a clarifying 
comment, 
> > or maybe better use explicit 2 * preempt_timeout / 1000 ?
> 
> It was clear that you were doubling it, but what's more
> interesting to know (perhaps in a comment) is why you are
> choosing to use the double of the timeout_ms instead of other
> values.
> 
> Makes sense?

Yes, good question.

Is it possible for more than one bb to hang?  If yes then should we wait 
longer than the longest preemption timeout?  Before I assumed that maybe we 
should, just in case, but now, having that revisited and reconsidered, I tend 
to agree that the longest preempt timeout, perhaps with a small margin (let's 
say +100ms) should be enough to recover from a single failing test case.  Let 
me verify if that works for the linked case.

Thanks,
Janusz

> 
> Thanks,
> Andi
>