[PATCH] drm/sched: Declare entity idle only after HW submission

[Boris Brezillon]

On Mon, 28 Jun 2021 11:46:08 +0200
Lucas Stach <l.stach at pengutronix.de> wrote:

> Am Donnerstag, dem 24.06.2021 um 16:08 +0200 schrieb Boris Brezillon:
> > The panfrost driver tries to kill in-flight jobs on FD close after
> > destroying the FD scheduler entities. For this to work properly, we
> > need to make sure the jobs popped from the scheduler entities have
> > been queued at the HW level before declaring the entity idle, otherwise
> > we might iterate over a list that doesn't contain those jobs.
> > 
> > Suggested-by: Lucas Stach <l.stach at pengutronix.de>
> > Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
> > Cc: Lucas Stach <l.stach at pengutronix.de>  
> 
> Not sure how much it's worth to review my own suggestion, but the
> implementation looks correct to me.
> I don't see any downsides for the existing drivers and it solves the
> race window for drivers that want to cancel jobs on the HW submission
> queue, without introducing yet another synchronization point.
> 
> Reviewed-by: Lucas Stach <l.stach at pengutronix.de>

Queued to drm-misc-next.

Thanks,

Boris

> 
> > ---
> >  drivers/gpu/drm/scheduler/sched_main.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> > index 81496ae2602e..aa776ebe326a 100644
> > --- a/drivers/gpu/drm/scheduler/sched_main.c
> > +++ b/drivers/gpu/drm/scheduler/sched_main.c
> > @@ -811,10 +811,10 @@ static int drm_sched_main(void *param)
> >  
> >  		sched_job = drm_sched_entity_pop_job(entity);
> >  
> > -		complete(&entity->entity_idle);
> > -
> > -		if (!sched_job)
> > +		if (!sched_job) {
> > +			complete(&entity->entity_idle);
> >  			continue;
> > +		}
> >  
> >  		s_fence = sched_job->s_fence;
> >  
> > @@ -823,6 +823,7 @@ static int drm_sched_main(void *param)
> >  
> >  		trace_drm_run_job(sched_job, entity);
> >  		fence = sched->ops->run_job(sched_job);
> > +		complete(&entity->entity_idle);
> >  		drm_sched_fence_scheduled(s_fence);
> >  
> >  		if (!IS_ERR_OR_NULL(fence)) {  
> 
>