Re: [PATCH 2/2] drm/scheduler: stop setting rq to NULL

[Christian König <ckoenig.leichtzumerken@xxxxxxxxx>]

Am 02.08.2018 um 00:25 schrieb Andrey Grodzovsky:
> Thinking again about this change and 53d5f1e drm/scheduler: move idle 
> entities to scheduler with less load v2
>
> Looks to me like use case for which fc9a539 drm/scheduler: add NULL 
> pointer check for run queue (v2) was done
>
> will not work anymore.
>
> First of all in drm_sched_entity_push_job, 'if (!entity->rq)' will 
> never be true any more since we stopped entity->rq to NULL in
>
> drm_sched_entity_flush.

Good point, going to remove that.

> Second of all, even after we removed the entity from rq in 
> drm_sched_entity_flush to terminate any subsequent submissions
>
> to the queue the other thread doing push job can just acquire again a 
> run queue
>
> from drm_sched_entity_get_free_sched and continue submission

That is actually desired.

When another process is now using the entity to submit jobs adding it 
back to the rq is actually the right thing to do cause the entity is 
still in use.

Christian.

> so you can't substitute ' if (!entity->rq)' to 'if 
> (list_empty(&entity->list))'.
>
> What about adding a 'stopped' flag to drm_sched_entity to be set in 
> drm_sched_entity_flush and in
>
> drm_sched_entity_push_job check for  'if (!entity->stopped)' instead 
> of  ' if (!entity->rq)' ?
>
> Andrey
>
>
> On 07/30/2018 07:03 AM, Christian König wrote:
> > We removed the redundancy of having an extra scheduler field, so we
> > can't set the rq to NULL any more or otherwise won't know which
> > scheduler to use for the cleanup.
> >
> > Just remove the entity from the scheduling list instead.
> >
> > Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> >   drivers/gpu/drm/scheduler/gpu_scheduler.c | 35 
> > +++++++------------------------
> >   1 file changed, 8 insertions(+), 27 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/scheduler/gpu_scheduler.c 
> > b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> > index f563e4fbb4b6..1b733229201e 100644
> > --- a/drivers/gpu/drm/scheduler/gpu_scheduler.c
> > +++ b/drivers/gpu/drm/scheduler/gpu_scheduler.c
> > @@ -198,21 +198,6 @@ int drm_sched_entity_init(struct 
> > drm_sched_entity *entity,
> >   }
> >   EXPORT_SYMBOL(drm_sched_entity_init);
> >   -/**
> > - * drm_sched_entity_is_initialized - Query if entity is initialized
> > - *
> > - * @sched: Pointer to scheduler instance
> > - * @entity: The pointer to a valid scheduler entity
> > - *
> > - * return true if entity is initialized, false otherwise
> > -*/
> > -static bool drm_sched_entity_is_initialized(struct drm_gpu_scheduler 
> > *sched,
> > -                        struct drm_sched_entity *entity)
> > -{
> > -    return entity->rq != NULL &&
> > -        entity->rq->sched == sched;
> > -}
> > -
> >   /**
> >    * drm_sched_entity_is_idle - Check if entity is idle
> >    *
> > @@ -224,7 +209,8 @@ static bool drm_sched_entity_is_idle(struct 
> > drm_sched_entity *entity)
> >   {
> >       rmb();
> >   -    if (!entity->rq || spsc_queue_peek(&entity->job_queue) == NULL)
> > +    if (list_empty(&entity->list) ||
> > +        spsc_queue_peek(&entity->job_queue) == NULL)
> >           return true;
> >         return false;
> > @@ -279,8 +265,6 @@ long drm_sched_entity_flush(struct 
> > drm_sched_entity *entity, long timeout)
> >       long ret = timeout;
> >         sched = entity->rq->sched;
> > -    if (!drm_sched_entity_is_initialized(sched, entity))
> > -        return ret;
> >       /**
> >        * The client will not queue more IBs during this fini, consume 
> > existing
> >        * queued IBs or discard them on SIGKILL
> > @@ -299,7 +283,7 @@ long drm_sched_entity_flush(struct 
> > drm_sched_entity *entity, long timeout)
> >       last_user = cmpxchg(&entity->last_user, current->group_leader, 
> > NULL);
> >       if ((!last_user || last_user == current->group_leader) &&
> >           (current->flags & PF_EXITING) && (current->exit_code == 
> > SIGKILL))
> > -        drm_sched_entity_set_rq(entity, NULL);
> > +        drm_sched_rq_remove_entity(entity->rq, entity);
> >         return ret;
> >   }
> > @@ -320,7 +304,7 @@ void drm_sched_entity_fini(struct 
> > drm_sched_entity *entity)
> >       struct drm_gpu_scheduler *sched;
> >         sched = entity->rq->sched;
> > -    drm_sched_entity_set_rq(entity, NULL);
> > +    drm_sched_rq_remove_entity(entity->rq, entity);
> >         /* Consumption of existing IBs wasn't completed. Forcefully
> >        * remove them here.
> > @@ -416,15 +400,12 @@ void drm_sched_entity_set_rq(struct 
> > drm_sched_entity *entity,
> >       if (entity->rq == rq)
> >           return;
> >   -    spin_lock(&entity->rq_lock);
> > -
> > -    if (entity->rq)
> > -        drm_sched_rq_remove_entity(entity->rq, entity);
> > +    BUG_ON(!rq);
> >   +    spin_lock(&entity->rq_lock);
> > +    drm_sched_rq_remove_entity(entity->rq, entity);
> >       entity->rq = rq;
> > -    if (rq)
> > -        drm_sched_rq_add_entity(rq, entity);
> > -
> > +    drm_sched_rq_add_entity(rq, entity);
> >       spin_unlock(&entity->rq_lock);
> >   }
> >   EXPORT_SYMBOL(drm_sched_entity_set_rq);

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