Re: [Intel-gfx] [PATCH] drm/i915: Increment composite fence seqno

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Dec 14, 2021 at 10:17:48PM +0200, Jani Nikula wrote:
> On Tue, 14 Dec 2021, Matthew Brost <matthew.brost@intel.com> wrote:
> > Increment composite fence seqno on each fence creation.
> >
> > Fixes: 544460c33821 ("drm/i915: Multi-BB execbuf")
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> >  drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> > index 2213f7b613da..96cf8361b017 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> > @@ -3113,7 +3113,7 @@ eb_composite_fence_create(struct i915_execbuffer *eb, int out_fence_fd)
> >  	fence_array = dma_fence_array_create(eb->num_batches,
> >  					     fences,
> >  					     eb->context->parallel.fence_context,
> > -					     eb->context->parallel.seqno,
> > +					     eb->context->parallel.seqno++,
> >  					     false);
> >  	if (!fence_array) {
> >  		kfree(fences);
> 
> I have no idea what's going on, but the feeling I get from "code smells"
> just in this small snippet is that the seqno++ does not take the error
> path here into account.
> 

It does not take the error path into account, but it completely fine to
skip seqno numbers. As long as next valid seqno is greater than the last
valid seqno we should be fine.

Matt 

> 
> BR,
> Jani.
> 
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center