drm/sched: Fix entities with 0 rqs.

Some blocks in amdgpu can have 0 rqs.

Job creation already fails with -ENOENT when entity->rq is NULL,
so jobs cannot be pushed. Without a rq there is no scheduler to
pop jobs, and rq selection already does the right thing with a
list of length 0.

So the operations we need to fix are:
  - Creation, do not set rq to rq_list[0] if the list can have length 0.
  - Do not flush any jobs when there is no rq.
  - On entity destruction handle the rq = NULL case.
  - on set_priority, do not try to change the rq if it is NULL.

Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index 4463d38..8e31b66 100644 (file)
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -52,12 +52,12 @@ int drm_sched_entity_init(struct drm_sched_entity *entity,
 {
        int i;
 
-       if (!(entity && rq_list && num_rq_list > 0 && rq_list[0]))
+       if (!(entity && rq_list && (num_rq_list == 0 || rq_list[0])))
                return -EINVAL;
 
        memset(entity, 0, sizeof(struct drm_sched_entity));
        INIT_LIST_HEAD(&entity->list);
-       entity->rq = rq_list[0];
+       entity->rq = NULL;
        entity->guilty = guilty;
        entity->num_rq_list = num_rq_list;
        entity->rq_list = kcalloc(num_rq_list, sizeof(struct drm_sched_rq *),
@@ -67,6 +67,10 @@ int drm_sched_entity_init(struct drm_sched_entity *entity,
 
        for (i = 0; i < num_rq_list; ++i)
                entity->rq_list[i] = rq_list[i];
+
+       if (num_rq_list)
+               entity->rq = rq_list[0];
+
        entity->last_scheduled = NULL;
 
        spin_lock_init(&entity->rq_lock);
@@ -165,6 +169,9 @@ long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout)
        struct task_struct *last_user;
        long ret = timeout;
 
+       if (!entity->rq)
+               return 0;
+
        sched = entity->rq->sched;
        /**
         * The client will not queue more IBs during this fini, consume existing
@@ -264,20 +271,24 @@ static void drm_sched_entity_kill_jobs(struct drm_sched_entity *entity)
  */
 void drm_sched_entity_fini(struct drm_sched_entity *entity)
 {
-       struct drm_gpu_scheduler *sched;
+       struct drm_gpu_scheduler *sched = NULL;
 
-       sched = entity->rq->sched;
-       drm_sched_rq_remove_entity(entity->rq, entity);
+       if (entity->rq) {
+               sched = entity->rq->sched;
+               drm_sched_rq_remove_entity(entity->rq, entity);
+       }
 
        /* Consumption of existing IBs wasn't completed. Forcefully
         * remove them here.
         */
        if (spsc_queue_peek(&entity->job_queue)) {
-               /* Park the kernel for a moment to make sure it isn't processing
-                * our enity.
-                */
-               kthread_park(sched->thread);
-               kthread_unpark(sched->thread);
+               if (sched) {
+                       /* Park the kernel for a moment to make sure it isn't processing
+                        * our enity.
+                        */
+                       kthread_park(sched->thread);
+                       kthread_unpark(sched->thread);
+               }
                if (entity->dependency) {
                        dma_fence_remove_callback(entity->dependency,
                                                  &entity->cb);
@@ -362,9 +373,11 @@ void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
        for (i = 0; i < entity->num_rq_list; ++i)
                drm_sched_entity_set_rq_priority(&entity->rq_list[i], priority);
 
-       drm_sched_rq_remove_entity(entity->rq, entity);
-       drm_sched_entity_set_rq_priority(&entity->rq, priority);
-       drm_sched_rq_add_entity(entity->rq, entity);
+       if (entity->rq) {
+               drm_sched_rq_remove_entity(entity->rq, entity);
+               drm_sched_entity_set_rq_priority(&entity->rq, priority);
+               drm_sched_rq_add_entity(entity->rq, entity);
+       }
 
        spin_unlock(&entity->rq_lock);
 }