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

[Daniel Vetter]

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 :-)

> 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.

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.

> 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.
-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