[PATCH] drm/sched: Eliminate drm_sched_run_job_queue_if_ready()

[Luben Tuikov <ltuikov89@xxxxxxxxx>]

Eliminate drm_sched_run_job_queue_if_ready() and instead just call
drm_sched_run_job_queue() in drm_sched_free_job_work(). The problem is that
the former function uses drm_sched_select_entity() to determine if the
scheduler had an entity ready in one of its run-queues, and in the case of the
Round-Robin (RR) scheduling, the function drm_sched_rq_select_entity_rr() does
just that, selects the _next_ entity which is ready, sets up the run-queue and
completion and returns that entity. The FIFO scheduling algorithm is unaffected.

Now, since drm_sched_run_job_work() also calls drm_sched_select_entity(), then
in the case of RR scheduling, that would result in calling select_entity()
twice, which may result in skipping a ready entity if more than one entity is
ready. This commit fixes this by eliminating the if_ready() variant.

Signed-off-by: Luben Tuikov <ltuikov89@xxxxxxxxx>
---
 drivers/gpu/drm/scheduler/sched_main.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 98b2ad54fc7071..05816e7cae8c8b 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -1040,16 +1040,6 @@ drm_sched_pick_best(struct drm_gpu_scheduler **sched_list,
 }
 EXPORT_SYMBOL(drm_sched_pick_best);
 
-/**
- * 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
  *
@@ -1069,7 +1059,7 @@ static void drm_sched_free_job_work(struct work_struct *w)
 		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_queue(sched);
 	}
 }
 
@@ -1127,7 +1117,7 @@ static void drm_sched_run_job_work(struct work_struct *w)
 	}
 
 	wake_up(&sched->job_scheduled);
-	drm_sched_run_job_queue_if_ready(sched);
+	drm_sched_run_job_queue(sched);
 }
 
 /**

base-commit: 6fd9487147c4f18ad77eea00bd8c9189eec74a3e
-- 
2.42.1