drm/amdgpu: use a spinlock instead of a mutex for the rq

More appropriate and fixes some nasty lockdep warnings.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>

drivers/gpu/drm/amd/scheduler/gpu_scheduler.c

@@ -30,27 +30,27 @@
 /* Initialize a given run queue struct */
 static void amd_sched_rq_init(struct amd_sched_rq *rq)
 {
+	spin_lock_init(&rq->lock);
 	INIT_LIST_HEAD(&rq->entities);
-	mutex_init(&rq->lock);
 	rq->current_entity = NULL;
 }
 
 static void amd_sched_rq_add_entity(struct amd_sched_rq *rq,
 				    struct amd_sched_entity *entity)
 {
-	mutex_lock(&rq->lock);
+	spin_lock(&rq->lock);
 	list_add_tail(&entity->list, &rq->entities);
-	mutex_unlock(&rq->lock);
+	spin_unlock(&rq->lock);
 }
 
 static void amd_sched_rq_remove_entity(struct amd_sched_rq *rq,
 				       struct amd_sched_entity *entity)
 {
-	mutex_lock(&rq->lock);
+	spin_lock(&rq->lock);
 	list_del_init(&entity->list);
 	if (rq->current_entity == entity)
 		rq->current_entity = NULL;
-	mutex_unlock(&rq->lock);
+	spin_unlock(&rq->lock);
 }
 
 /**
@@ -61,12 +61,16 @@ static void amd_sched_rq_remove_entity(struct amd_sched_rq *rq,
 static struct amd_sched_entity *
 amd_sched_rq_select_entity(struct amd_sched_rq *rq)
 {
-	struct amd_sched_entity *entity = rq->current_entity;
+	struct amd_sched_entity *entity;
 
+	spin_lock(&rq->lock);
+
+	entity = rq->current_entity;
 	if (entity) {
 		list_for_each_entry_continue(entity, &rq->entities, list) {
 			if (!kfifo_is_empty(&entity->job_queue)) {
 				rq->current_entity = entity;
+				spin_unlock(&rq->lock);
 				return rq->current_entity;
 			}
 		}
@@ -76,6 +80,7 @@ amd_sched_rq_select_entity(struct amd_sched_rq *rq)
 
 		if (!kfifo_is_empty(&entity->job_queue)) {
 			rq->current_entity = entity;
+			spin_unlock(&rq->lock);
 			return rq->current_entity;
 		}
 
@@ -83,6 +88,8 @@ amd_sched_rq_select_entity(struct amd_sched_rq *rq)
 			break;
 	}
 
+	spin_unlock(&rq->lock);
+
 	return NULL;
 }
 
@@ -108,22 +115,6 @@ static bool is_scheduler_ready(struct amd_gpu_scheduler *sched)
 	return full;
 }
 
-/**
- * Select next entity from the kernel run queue, if not available,
- * return null.
-*/
-static struct amd_sched_entity *
-kernel_rq_select_context(struct amd_gpu_scheduler *sched)
-{
-	struct amd_sched_entity *sched_entity;
-	struct amd_sched_rq *rq = &sched->kernel_rq;
-
-	mutex_lock(&rq->lock);
-	sched_entity = amd_sched_rq_select_entity(rq);
-	mutex_unlock(&rq->lock);
-	return sched_entity;
-}
-
 /**
  * Select next entity containing real IB submissions
 */
@@ -132,21 +123,15 @@ select_context(struct amd_gpu_scheduler *sched)
 {
 	struct amd_sched_entity *wake_entity = NULL;
 	struct amd_sched_entity *tmp;
-	struct amd_sched_rq *rq;
 
 	if (!is_scheduler_ready(sched))
 		return NULL;
 
 	/* Kernel run queue has higher priority than normal run queue*/
-	tmp = kernel_rq_select_context(sched);
-	if (tmp != NULL)
-		goto exit;
-
-	rq = &sched->sched_rq;
-	mutex_lock(&rq->lock);
-	tmp = amd_sched_rq_select_entity(rq);
-	mutex_unlock(&rq->lock);
-exit:
+	tmp = amd_sched_rq_select_entity(&sched->kernel_rq);
+	if (tmp == NULL)
+		tmp = amd_sched_rq_select_entity(&sched->sched_rq);
+
 	if (sched->current_entity && (sched->current_entity != tmp))
 		wake_entity = sched->current_entity;
 	sched->current_entity = tmp;

drivers/gpu/drm/amd/scheduler/gpu_scheduler.h

@@ -63,7 +63,7 @@ struct amd_sched_entity {
  * the next entity to emit commands from.
 */
 struct amd_sched_rq {
-	struct mutex		lock;
+	spinlock_t		lock;
 	struct list_head	entities;
 	struct amd_sched_entity	*current_entity;
 };