[PATCH 06/22] drm/i915/execlists: Do not propagate errors to dependent fences

[Matthew Brost]

On Tue, Aug 17, 2021 at 11:21:27AM +0200, Daniel Vetter wrote:
> On Mon, Aug 16, 2021 at 06:51:23AM -0700, Matthew Brost wrote:
> > Progagating errors to dependent fences is wrong, don't do it. Selftest
> > in following patch exposes this bug.
> 
> Please explain what "this bug" is, it's hard to read minds, especially at
> a distance in spacetime :-)
> 

Not a very good explaination.

> > Fixes: 8e9f84cf5cac ("drm/i915/gt: Propagate change in error status to children on unhold")
> 
> I think it would be better to outright revert this, instead of just
> disabling it like this.
>

I tried revert and git did some really odd things that I couldn't
resolve, hence the new patch.
 
> Also please cite the dma_fence error propagation revert from Jason:
> 
> commit 93a2711cddd5760e2f0f901817d71c93183c3b87
> Author: Jason Ekstrand <jason at jlekstrand.net>
> Date:   Wed Jul 14 14:34:16 2021 -0500
> 
>     Revert "drm/i915: Propagate errors on awaiting already signaled fences"
> 
> Maybe in full, if you need the justification.
>

Will site.

> > Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> > Cc: <stable at vger.kernel.org>
> 
> Unless "this bug" is some real world impact thing I wouldn't put cc:
> stable on this.

Got it.

Matt

> -Daniel
> > ---
> >  drivers/gpu/drm/i915/gt/intel_execlists_submission.c | 4 ----
> >  1 file changed, 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> > index de5f9c86b9a4..cafb0608ffb4 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> > @@ -2140,10 +2140,6 @@ static void __execlists_unhold(struct i915_request *rq)
> >  			if (p->flags & I915_DEPENDENCY_WEAK)
> >  				continue;
> >  
> > -			/* Propagate any change in error status */
> > -			if (rq->fence.error)
> > -				i915_request_set_error_once(w, rq->fence.error);
> > -
> >  			if (w->engine != rq->engine)
> >  				continue;
> >  
> > -- 
> > 2.32.0
> > 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch