drm/sched: Re-group and rename the entity run-queue lock

When writing to a drm_sched_entity's run-queue, writers are protected
through the lock drm_sched_entity.rq_lock. This naming, however,
frequently collides with the separate internal lock of struct
drm_sched_rq, resulting in uses like this:

spin_lock(&entity->rq_lock);
spin_lock(&entity->rq->lock);

Rename drm_sched_entity.rq_lock to improve readability. While at it,
re-order that struct's members to make it more obvious what the lock
protects.

v2:
* Rename some rq_lock straddlers in kerneldoc, improve commit text. (Philipp)

Signed-off-by: Tvrtko Ursulin <[e-mail]>
Suggested-by: Christian König <[e-mail]>
Cc: Alex Deucher <[e-mail]>
Cc: Luben Tuikov <[e-mail]>
Cc: Matthew Brost <[e-mail]>
Cc: Philipp Stanner <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
[pstanner: Fix typo in docstring]
Signed-off-by: Philipp Stanner <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/scheduler/sched_entity.c

···
 	/* We start in an idle state. */
 	complete_all(&entity->entity_idle);
 
-	spin_lock_init(&entity->rq_lock);
+	spin_lock_init(&entity->lock);
 	spsc_queue_init(&entity->job_queue);
 
 	atomic_set(&entity->fence_seq, 0);
···
 {
 	WARN_ON(!num_sched_list || !sched_list);
 
-	spin_lock(&entity->rq_lock);
+	spin_lock(&entity->lock);
 	entity->sched_list = sched_list;
 	entity->num_sched_list = num_sched_list;
-	spin_unlock(&entity->rq_lock);
+	spin_unlock(&entity->lock);
 }
 EXPORT_SYMBOL(drm_sched_entity_modify_sched);
 
···
 	if (!entity->rq)
 		return;
 
-	spin_lock(&entity->rq_lock);
+	spin_lock(&entity->lock);
 	entity->stopped = true;
 	drm_sched_rq_remove_entity(entity->rq, entity);
-	spin_unlock(&entity->rq_lock);
+	spin_unlock(&entity->lock);
 
 	/* Make sure this entity is not used by the scheduler at the moment */
 	wait_for_completion(&entity->entity_idle);
···
 void drm_sched_entity_set_priority(struct drm_sched_entity *entity,
 				   enum drm_sched_priority priority)
 {
-	spin_lock(&entity->rq_lock);
+	spin_lock(&entity->lock);
 	entity->priority = priority;
-	spin_unlock(&entity->rq_lock);
+	spin_unlock(&entity->lock);
 }
 EXPORT_SYMBOL(drm_sched_entity_set_priority);
 
···
 
 		next = to_drm_sched_job(spsc_queue_peek(&entity->job_queue));
 		if (next) {
-			spin_lock(&entity->rq_lock);
+			spin_lock(&entity->lock);
 			drm_sched_rq_update_fifo_locked(entity,
 							next->submit_ts);
-			spin_unlock(&entity->rq_lock);
+			spin_unlock(&entity->lock);
 		}
 	}
 
···
 	if (fence && !dma_fence_is_signaled(fence))
 		return;
 
-	spin_lock(&entity->rq_lock);
+	spin_lock(&entity->lock);
 	sched = drm_sched_pick_best(entity->sched_list, entity->num_sched_list);
 	rq = sched ? sched->sched_rq[entity->priority] : NULL;
 	if (rq != entity->rq) {
 		drm_sched_rq_remove_entity(entity->rq, entity);
 		entity->rq = rq;
 	}
-	spin_unlock(&entity->rq_lock);
+	spin_unlock(&entity->lock);
 
 	if (entity->num_sched_list == 1)
 		entity->sched_list = NULL;
···
 		struct drm_sched_rq *rq;
 
 		/* Add the entity to the run queue */
-		spin_lock(&entity->rq_lock);
+		spin_lock(&entity->lock);
 		if (entity->stopped) {
-			spin_unlock(&entity->rq_lock);
+			spin_unlock(&entity->lock);
 
 			DRM_ERROR("Trying to push to a killed entity\n");
 			return;
···
 		if (drm_sched_policy == DRM_SCHED_POLICY_FIFO)
 			drm_sched_rq_update_fifo_locked(entity, submit_ts);
 
-		spin_unlock(&entity->rq_lock);
+		spin_unlock(&entity->lock);
 
 		drm_sched_wakeup(sched);
 	}

drivers/gpu/drm/scheduler/sched_main.c

···
 	 * for entity from within concurrent drm_sched_entity_select_rq and the
 	 * other to update the rb tree structure.
 	 */
-	lockdep_assert_held(&entity->rq_lock);
+	lockdep_assert_held(&entity->lock);
 
 	spin_lock(&entity->rq->lock);
 

include/drm/gpu_scheduler.h

···
 	struct list_head		list;
 
 	/**
+	 * @lock:
+	 *
+	 * Lock protecting the run-queue (@rq) to which this entity belongs,
+	 * @priority and the list of schedulers (@sched_list, @num_sched_list).
+	 */
+	spinlock_t			lock;
+
+	/**
 	 * @rq:
 	 *
 	 * Runqueue on which this entity is currently scheduled.
 	 *
 	 * FIXME: Locking is very unclear for this. Writers are protected by
-	 * @rq_lock, but readers are generally lockless and seem to just race
-	 * with not even a READ_ONCE.
+	 * @lock, but readers are generally lockless and seem to just race with
+	 * not even a READ_ONCE.
 	 */
 	struct drm_sched_rq		*rq;
 
···
 	 * @priority:
 	 *
 	 * Priority of the entity. This can be modified by calling
-	 * drm_sched_entity_set_priority(). Protected by &rq_lock.
+	 * drm_sched_entity_set_priority(). Protected by @lock.
 	 */
 	enum drm_sched_priority         priority;
-
-	/**
-	 * @rq_lock:
-	 *
-	 * Lock to modify the runqueue to which this entity belongs.
-	 */
-	spinlock_t			rq_lock;
 
 	/**
 	 * @job_queue: the list of jobs of this entity.