Re: [PATCH v3 5/6] drm/sched: Use parent fence instead of finished

[Andrey Grodzovsky]

Got it.

Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>

Andrey

On 2022-09-09 16:30, Yadav, Arvind wrote:
> On 9/9/2022 11:02 PM, Andrey Grodzovsky wrote:
> > What exactly is the scenario which this patch fixes in more detail 
> > please  ?
> GPU reset issue started after adding [PATCH 6/6].
>
> Root cause -> In drm_sched_get_cleanup_job(), We use the finished 
> fence status bit to check the job status dma_fence_is_signaled(). If a 
> job is signaled (DMA_FENCE_FLAG_SIGNALED_BIT is set), then we cancel 
> the reset worker thread.
>
> After applying [patch 6] now we are checking enable signaling in 
> dma_fence_is_signaled() by checking DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT 
> bit. but signaling is not enabled for the finished fence. As a result, 
> dma_fence_is_signaled() always returns false, and 
> drm_sched_get_cleanup_job() will not cancel the reset worker thread, 
> resulting in the GPU reset.
>
> To Fix the above issue  Christian suggested that we can use 
> parent(hardware) fence instead of finished fence because signaling 
> enabled by the calling of dma_fence_add_callback() for parent fence. 
> As a result, dma_fence_is_signaled() will return the correct fence 
> status and reset worker thread can be cancelled in 
> drm_sched_get_cleanup_job().
>
> ~arvind
>
> > Andrey
> >
> > On 2022-09-09 13:08, Arvind Yadav wrote:
> > > Using the parent fence instead of the finished fence
> > > to get the job status. This change is to avoid GPU
> > > scheduler timeout error which can cause GPU reset.
> > >
> > > Signed-off-by: Arvind Yadav <Arvind.Yadav@xxxxxxx>
> > > ---
> > >
> > > changes in v1,v2 - Enable signaling for finished fence in sche_main()
> > > is removed
> > >
> > > ---
> > >   drivers/gpu/drm/scheduler/sched_main.c | 4 ++--
> > >   1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/scheduler/sched_main.c 
> > > b/drivers/gpu/drm/scheduler/sched_main.c
> > > index e0ab14e0fb6b..2ac28ad11432 100644
> > > --- a/drivers/gpu/drm/scheduler/sched_main.c
> > > +++ b/drivers/gpu/drm/scheduler/sched_main.c
> > > @@ -829,7 +829,7 @@ drm_sched_get_cleanup_job(struct 
> > > drm_gpu_scheduler *sched)
> > >       job = list_first_entry_or_null(&sched->pending_list,
> > >                          struct drm_sched_job, list);
> > >   -    if (job && dma_fence_is_signaled(&job->s_fence->finished)) {
> > > +    if (job && dma_fence_is_signaled(job->s_fence->parent)) {
> > >           /* remove job from pending_list */
> > >           list_del_init(&job->list);
> > >   @@ -841,7 +841,7 @@ drm_sched_get_cleanup_job(struct 
> > > drm_gpu_scheduler *sched)
> > >             if (next) {
> > >               next->s_fence->scheduled.timestamp =
> > > -                job->s_fence->finished.timestamp;
> > > +                job->s_fence->parent->timestamp;
> > >               /* start TO timer for next job */
> > >               drm_sched_start_timeout(sched);
> > >           }