drm/sched: Split free_job into own work item

Rather than call free_job and run_job in same work item have a dedicated
work item for each. This aligns with the design and intended use of work
queues.

v2:
   - Test for DMA_FENCE_FLAG_TIMESTAMP_BIT before setting
     timestamp in free_job() work item (Danilo)
v3:
  - Drop forward dec of drm_sched_select_entity (Boris)
  - Return in drm_sched_run_job_work if entity NULL (Boris)
v4:
  - Replace dequeue with peek and invert logic (Luben)
  - Wrap to 100 lines (Luben)
  - Update comments for *_queue / *_queue_if_ready functions (Luben)
v5:
  - Drop peek argument, blindly reinit idle (Luben)
  - s/drm_sched_free_job_queue_if_ready/drm_sched_free_job_queue_if_done (Luben)
  - Update work_run_job & work_free_job kernel doc (Luben)
v6:
  - Do not move drm_sched_select_entity in file (Luben)
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20231031032439.1558703-4-matthew.brost@intel.comReviewed-by: Luben Tuikov <ltuikov89@gmail.com>
Signed-off-by: Luben Tuikov <ltuikov89@gmail.com>

drivers/gpu/drm/scheduler/sched_main.c

@@ -265,6 +265,32 @@ static void drm_sched_run_job_queue(struct drm_gpu_scheduler *sched)
 		queue_work(sched->submit_wq, &sched->work_run_job);
 }
 
+/**
+ * drm_sched_free_job_queue - enqueue free-job work
+ * @sched: scheduler instance
+ */
+static void drm_sched_free_job_queue(struct drm_gpu_scheduler *sched)
+{
+	if (!READ_ONCE(sched->pause_submit))
+		queue_work(sched->submit_wq, &sched->work_free_job);
+}
+
+/**
+ * drm_sched_free_job_queue_if_done - enqueue free-job work if ready
+ * @sched: scheduler instance
+ */
+static void drm_sched_free_job_queue_if_done(struct drm_gpu_scheduler *sched)
+{
+	struct drm_sched_job *job;
+
+	spin_lock(&sched->job_list_lock);
+	job = list_first_entry_or_null(&sched->pending_list,
+				       struct drm_sched_job, list);
+	if (job && dma_fence_is_signaled(&job->s_fence->finished))
+		drm_sched_free_job_queue(sched);
+	spin_unlock(&sched->job_list_lock);
+}
+
 /**
  * drm_sched_job_done - complete a job
  * @s_job: pointer to the job which is done
@@ -284,7 +310,7 @@ static void drm_sched_job_done(struct drm_sched_job *s_job, int result)
 	dma_fence_get(&s_fence->finished);
 	drm_sched_fence_finished(s_fence, result);
 	dma_fence_put(&s_fence->finished);
-	drm_sched_run_job_queue(sched);
+	drm_sched_free_job_queue(sched);
 }
 
 /**
@@ -943,8 +969,10 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
 						typeof(*next), list);
 
 		if (next) {
-			next->s_fence->scheduled.timestamp =
-				dma_fence_timestamp(&job->s_fence->finished);
+			if (test_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT,
+				     &next->s_fence->scheduled.flags))
+				next->s_fence->scheduled.timestamp =
+					dma_fence_timestamp(&job->s_fence->finished);
 			/* start TO timer for next job */
 			drm_sched_start_timeout(sched);
 		}
@@ -994,7 +1022,40 @@ drm_sched_pick_best(struct drm_gpu_scheduler **sched_list,
 EXPORT_SYMBOL(drm_sched_pick_best);
 
 /**
- * drm_sched_run_job_work - main scheduler thread
+ * drm_sched_run_job_queue_if_ready - enqueue run-job work if ready
+ * @sched: scheduler instance
+ */
+static void drm_sched_run_job_queue_if_ready(struct drm_gpu_scheduler *sched)
+{
+	if (drm_sched_select_entity(sched))
+		drm_sched_run_job_queue(sched);
+}
+
+/**
+ * drm_sched_free_job_work - worker to call free_job
+ *
+ * @w: free job work
+ */
+static void drm_sched_free_job_work(struct work_struct *w)
+{
+	struct drm_gpu_scheduler *sched =
+		container_of(w, struct drm_gpu_scheduler, work_free_job);
+	struct drm_sched_job *cleanup_job;
+
+	if (READ_ONCE(sched->pause_submit))
+		return;
+
+	cleanup_job = drm_sched_get_cleanup_job(sched);
+	if (cleanup_job) {
+		sched->ops->free_job(cleanup_job);
+
+		drm_sched_free_job_queue_if_done(sched);
+		drm_sched_run_job_queue_if_ready(sched);
+	}
+}
+
+/**
+ * drm_sched_run_job_work - worker to call run_job
  *
  * @w: run job work
  */
@@ -1003,65 +1064,51 @@ static void drm_sched_run_job_work(struct work_struct *w)
 	struct drm_gpu_scheduler *sched =
 		container_of(w, struct drm_gpu_scheduler, work_run_job);
 	struct drm_sched_entity *entity;
-	struct drm_sched_job *cleanup_job;
+	struct dma_fence *fence;
+	struct drm_sched_fence *s_fence;
+	struct drm_sched_job *sched_job;
 	int r;
 
 	if (READ_ONCE(sched->pause_submit))
 		return;
 
-	cleanup_job = drm_sched_get_cleanup_job(sched);
 	entity = drm_sched_select_entity(sched);
+	if (!entity)
+		return;
 
-	if (!entity && !cleanup_job)
+	sched_job = drm_sched_entity_pop_job(entity);
+	if (!sched_job) {
+		complete_all(&entity->entity_idle);
 		return;	/* No more work */
+	}
 
-	if (cleanup_job)
-		sched->ops->free_job(cleanup_job);
-
-	if (entity) {
-		struct dma_fence *fence;
-		struct drm_sched_fence *s_fence;
-		struct drm_sched_job *sched_job;
-
-		sched_job = drm_sched_entity_pop_job(entity);
-		if (!sched_job) {
-			complete_all(&entity->entity_idle);
-			if (!cleanup_job)
-				return;	/* No more work */
-			goto again;
-		}
-
-		s_fence = sched_job->s_fence;
-
-		atomic_inc(&sched->hw_rq_count);
-		drm_sched_job_begin(sched_job);
+	s_fence = sched_job->s_fence;
 
-		trace_drm_run_job(sched_job, entity);
-		fence = sched->ops->run_job(sched_job);
-		complete_all(&entity->entity_idle);
-		drm_sched_fence_scheduled(s_fence, fence);
+	atomic_inc(&sched->hw_rq_count);
+	drm_sched_job_begin(sched_job);
 
-		if (!IS_ERR_OR_NULL(fence)) {
-			/* Drop for original kref_init of the fence */
-			dma_fence_put(fence);
+	trace_drm_run_job(sched_job, entity);
+	fence = sched->ops->run_job(sched_job);
+	complete_all(&entity->entity_idle);
+	drm_sched_fence_scheduled(s_fence, fence);
 
-			r = dma_fence_add_callback(fence, &sched_job->cb,
-						   drm_sched_job_done_cb);
-			if (r == -ENOENT)
-				drm_sched_job_done(sched_job, fence->error);
-			else if (r)
-				DRM_DEV_ERROR(sched->dev, "fence add callback failed (%d)\n",
-					  r);
-		} else {
-			drm_sched_job_done(sched_job, IS_ERR(fence) ?
-					   PTR_ERR(fence) : 0);
-		}
+	if (!IS_ERR_OR_NULL(fence)) {
+		/* Drop for original kref_init of the fence */
+		dma_fence_put(fence);
 
-		wake_up(&sched->job_scheduled);
+		r = dma_fence_add_callback(fence, &sched_job->cb,
+					   drm_sched_job_done_cb);
+		if (r == -ENOENT)
+			drm_sched_job_done(sched_job, fence->error);
+		else if (r)
+			DRM_DEV_ERROR(sched->dev, "fence add callback failed (%d)\n", r);
+	} else {
+		drm_sched_job_done(sched_job, IS_ERR(fence) ?
+				   PTR_ERR(fence) : 0);
 	}
 
-again:
-	drm_sched_run_job_queue(sched);
+	wake_up(&sched->job_scheduled);
+	drm_sched_run_job_queue_if_ready(sched);
 }
 
 /**
@@ -1145,6 +1192,7 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
 	atomic_set(&sched->hw_rq_count, 0);
 	INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
 	INIT_WORK(&sched->work_run_job, drm_sched_run_job_work);
+	INIT_WORK(&sched->work_free_job, drm_sched_free_job_work);
 	atomic_set(&sched->_score, 0);
 	atomic64_set(&sched->job_id_count, 0);
 	sched->pause_submit = false;
@@ -1274,6 +1322,7 @@ void drm_sched_wqueue_stop(struct drm_gpu_scheduler *sched)
 {
 	WRITE_ONCE(sched->pause_submit, true);
 	cancel_work_sync(&sched->work_run_job);
+	cancel_work_sync(&sched->work_free_job);
 }
 EXPORT_SYMBOL(drm_sched_wqueue_stop);
 
@@ -1286,5 +1335,6 @@ void drm_sched_wqueue_start(struct drm_gpu_scheduler *sched)
 {
 	WRITE_ONCE(sched->pause_submit, false);
 	queue_work(sched->submit_wq, &sched->work_run_job);
+	queue_work(sched->submit_wq, &sched->work_free_job);
 }
 EXPORT_SYMBOL(drm_sched_wqueue_start);

include/drm/gpu_scheduler.h

@@ -480,9 +480,10 @@ struct drm_sched_backend_ops {
  *                 finished.
  * @hw_rq_count: the number of jobs currently in the hardware queue.
  * @job_id_count: used to assign unique id to the each job.
- * @submit_wq: workqueue used to queue @work_run_job
+ * @submit_wq: workqueue used to queue @work_run_job and @work_free_job
  * @timeout_wq: workqueue used to queue @work_tdr
  * @work_run_job: work which calls run_job op of each scheduler.
+ * @work_free_job: work which calls free_job op of each scheduler.
  * @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the
  *            timeout interval is over.
  * @pending_list: the list of jobs which are currently in the job queue.
@@ -512,6 +513,7 @@ struct drm_gpu_scheduler {
 	struct workqueue_struct		*submit_wq;
 	struct workqueue_struct		*timeout_wq;
 	struct work_struct		work_run_job;
+	struct work_struct		work_free_job;
 	struct delayed_work		work_tdr;
 	struct list_head		pending_list;
 	spinlock_t			job_list_lock;