[PATCH 8/8] drm/sched: Further optimise drm_sched_entity_push_job

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>

Having removed one re-lock cycle on the entity->lock in a patch titled
"drm/sched: Optimise drm_sched_entity_push_job", with only a tiny bit
larger refactoring we can do the same optimisation on the rq->lock.
(Currently both drm_sched_rq_add_entity() and
drm_sched_rq_update_fifo_locked() take and release the same lock.)

To achieve this we rename drm_sched_rq_add_entity() to
drm_sched_rq_add_entity_locked(), making it expect the rq->lock to be
held, and also add the same expectation to
drm_sched_rq_update_fifo_locked().

For more stream-lining we also add the run-queue as an explicit parameter
to drm_sched_rq_remove_fifo_locked() to avoid both callers and callee
having to dereference entity->rq.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
Cc: Christian König <christian.koenig at amd.com>
Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: Luben Tuikov <ltuikov89 at gmail.com>
Cc: Matthew Brost <matthew.brost at intel.com>
Cc: Philipp Stanner <pstanner at redhat.com>
---
 drivers/gpu/drm/scheduler/sched_entity.c |  7 ++--
 drivers/gpu/drm/scheduler/sched_main.c   | 41 +++++++++++++-----------
 include/drm/gpu_scheduler.h              |  7 ++--
 3 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c
index b4c4f9923e0b..2102c726d275 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -614,11 +614,14 @@ void drm_sched_entity_push_job(struct drm_sched_job *sched_job)
 		sched = rq->sched;
 
 		atomic_inc(sched->score);
-		drm_sched_rq_add_entity(rq, entity);
+
+		spin_lock(&rq->lock);
+		drm_sched_rq_add_entity_locked(rq, entity);
 
 		if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
-			drm_sched_rq_update_fifo_locked(entity, submit_ts);
+			drm_sched_rq_update_fifo_locked(entity, rq, submit_ts);
 
+		spin_unlock(&rq->lock);
 		spin_unlock(&entity->lock);
 
 		drm_sched_wakeup(sched, entity);
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 937e7d1cfc49..1ccd2aed2d32 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -153,41 +153,44 @@ static __always_inline bool drm_sched_entity_compare_before(struct rb_node *a,
 	return ktime_before(ent_a->oldest_job_waiting, ent_b->oldest_job_waiting);
 }
 
-static inline void drm_sched_rq_remove_fifo_locked(struct drm_sched_entity *entity)
+static void drm_sched_rq_remove_fifo_locked(struct drm_sched_entity *entity,
+					    struct drm_sched_rq *rq)
 {
-	struct drm_sched_rq *rq = entity->rq;
-
 	if (!RB_EMPTY_NODE(&entity->rb_tree_node)) {
 		rb_erase_cached(&entity->rb_tree_node, &rq->rb_tree_root);
 		RB_CLEAR_NODE(&entity->rb_tree_node);
 	}
 }
 
-void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity, ktime_t ts)
+void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity,
+				     struct drm_sched_rq *rq,
+				     ktime_t ts)
 {
 	lockdep_assert_held(&entity->lock);
+	lockdep_assert_held(&rq->lock);
 
-	spin_lock(&entity->rq->lock);
-
-	drm_sched_rq_remove_fifo_locked(entity);
+	drm_sched_rq_remove_fifo_locked(entity, rq);
 
 	entity->oldest_job_waiting = ts;
 
-	rb_add_cached(&entity->rb_tree_node, &entity->rq->rb_tree_root,
+	rb_add_cached(&entity->rb_tree_node, &rq->rb_tree_root,
 		      drm_sched_entity_compare_before);
-
-	spin_unlock(&entity->rq->lock);
 }
 
 void drm_sched_rq_update_fifo(struct drm_sched_entity *entity, ktime_t ts)
 {
+	struct drm_sched_rq *rq;
+
 	/*
 	 * Both locks need to be grabbed, one to protect from entity->rq change
 	 * for entity from within concurrent drm_sched_entity_select_rq and the
 	 * other to update the rb tree structure.
 	 */
 	spin_lock(&entity->lock);
-	drm_sched_rq_update_fifo_locked(entity, ts);
+	rq = entity->rq;
+	spin_lock(&rq->lock);
+	drm_sched_rq_update_fifo_locked(entity, rq, ts);
+	spin_unlock(&rq->lock);
 	spin_unlock(&entity->lock);
 }
 
@@ -210,25 +213,23 @@ static void drm_sched_rq_init(struct drm_gpu_scheduler *sched,
 }
 
 /**
- * drm_sched_rq_add_entity - add an entity
+ * drm_sched_rq_add_entity_locked - add an entity
  *
  * @rq: scheduler run queue
  * @entity: scheduler entity
  *
  * Adds a scheduler entity to the run queue.
  */
-void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
-			     struct drm_sched_entity *entity)
+void drm_sched_rq_add_entity_locked(struct drm_sched_rq *rq,
+				    struct drm_sched_entity *entity)
 {
+	lockdep_assert_held(&rq->lock);
+
 	if (!list_empty(&entity->list))
 		return;
 
-	spin_lock(&rq->lock);
-
 	atomic_inc(rq->sched->score);
 	list_add_tail(&entity->list, &rq->entities);
-
-	spin_unlock(&rq->lock);
 }
 
 /**
@@ -242,6 +243,8 @@ void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
 void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
 				struct drm_sched_entity *entity)
 {
+	lockdep_assert_held(&entity->lock);
+
 	if (list_empty(&entity->list))
 		return;
 
@@ -254,7 +257,7 @@ void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
 		rq->current_entity = NULL;
 
 	if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
-		drm_sched_rq_remove_fifo_locked(entity);
+		drm_sched_rq_remove_fifo_locked(entity, rq);
 
 	spin_unlock(&rq->lock);
 }
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 5a1e4c803b90..2ad33e2fe2d2 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -591,13 +591,14 @@ bool drm_sched_dependency_optimized(struct dma_fence* fence,
 				    struct drm_sched_entity *entity);
 void drm_sched_fault(struct drm_gpu_scheduler *sched);
 
-void drm_sched_rq_add_entity(struct drm_sched_rq *rq,
-			     struct drm_sched_entity *entity);
+void drm_sched_rq_add_entity_locked(struct drm_sched_rq *rq,
+				    struct drm_sched_entity *entity);
 void drm_sched_rq_remove_entity(struct drm_sched_rq *rq,
 				struct drm_sched_entity *entity);
 
 void drm_sched_rq_update_fifo(struct drm_sched_entity *entity, ktime_t ts);
-void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity, ktime_t ts);
+void drm_sched_rq_update_fifo_locked(struct drm_sched_entity *entity,
+				     struct drm_sched_rq *rq, ktime_t ts);
 
 int drm_sched_entity_init(struct drm_sched_entity *entity,
 			  enum drm_sched_priority priority,
-- 
2.46.0