Re: [PATCH] drm/sched: Remove redundant entity->rq initialization and checks

[Philipp Stanner <phasta@mailbox.org>]

On Tue, 2026-06-02 at 16:33 +0100, Tvrtko Ursulin wrote:
> Commit
> 28c5bf28763d ("drm/sched: Disallow initializing entities with no schedulers")
> failed to notice clearing of entity->rq in drm_sched_entity_init() is now

By clearing you also mean the setting to NULL?

I'd just use "initialization" consistently, like in the commit title.

> redundant and can be removed.
> 
> Given that entity->rq can now never be NULL, we also remove two impossible
> checks, from drm_sched_entity_kill() and drm_sched_entity_flush()
> respectively.
> 
> Similarly, we can also remove the !entity->rq check in
> drm_sched_job_init(). And for the better, given that the error message, if
> it ever triggered, would have dereferenced the yet un-initialized job->
> sched (only initialized later in drm_sched_job_arm()). This appears to
> have been theoretically broken ever since commit
> 56e449603f0a ("drm/sched: Convert the GPU scheduler to variable number of run-queues")
> .
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Philipp Stanner <phasta@kernel.org>
> ---
>  drivers/gpu/drm/scheduler/sched_entity.c | 11 ++---------
>  drivers/gpu/drm/scheduler/sched_main.c   |  9 ---------
>  2 files changed, 2 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
> index 4ebb513255ed..c51101ec70c1 100644
> --- a/drivers/gpu/drm/scheduler/sched_entity.c
> +++ b/drivers/gpu/drm/scheduler/sched_entity.c
> @@ -129,7 +129,6 @@ int drm_sched_entity_init(struct drm_sched_entity *entity,
>  		return -ENOMEM;
>  
>  	INIT_LIST_HEAD(&entity->list);
> -	entity->rq = NULL;

It would seem that has always been redundant because of the memset(0)
directly above.

>  	entity->guilty = guilty;
>  	entity->priority = priority;
>  	entity->last_user = current->group_leader;
> @@ -280,9 +279,6 @@ void drm_sched_entity_kill(struct drm_sched_entity *entity)
>  	struct drm_sched_job *job;
>  	struct dma_fence *prev;
>  
> -	if (!entity->rq)
> -		return;
> -
>  	spin_lock(&entity->lock);
>  	entity->stopped = true;
>  	drm_sched_rq_remove_entity(entity->rq, entity);
> @@ -329,14 +325,11 @@ EXPORT_SYMBOL(drm_sched_entity_kill);
>   */
>  long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout)
>  {
> -	struct drm_gpu_scheduler *sched;
> +	struct drm_gpu_scheduler *sched =
> +		container_of(entity->rq, typeof(*sched), rq);
>  	struct task_struct *last_user;
>  	long ret = timeout;
>  
> -	if (!entity->rq)
> -		return 0;
> -
> -	sched = container_of(entity->rq, typeof(*sched), rq);
>  	/*
>  	 * The client will not queue more jobs during this fini - consume
>  	 * existing queued ones, or discard them on SIGKILL.
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 818d3d4434b5..d2ca01b31ee4 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -588,15 +588,6 @@ int drm_sched_job_init(struct drm_sched_job *job,
>  		       u32 credits, void *owner,
>  		       uint64_t drm_client_id)
>  {
> -	if (!entity->rq) {
> -		/* This will most likely be followed by missing frames
> -		 * or worse--a blank screen--leave a trail in the
> -		 * logs, so this can be debugged easier.
> -		 */
> -		dev_err(job->sched->dev, "%s: entity has no rq!\n", __func__);
> -		return -ENOENT;
> -	}
> -
>  	if (unlikely(!credits)) {
>  		pr_err("*ERROR* %s: credits cannot be 0!\n", __func__);
>  		return -EINVAL;

But overall a very nice cleanup


P.