[PATCH v3] Revert "drm/scheduler: Avoid accessing freed bad job."

[Jingwen Chen]

[Why]
for bailing job, this commit will delete it from pending list thus the
bailing job will never have a chance to be resubmitted even in advance
tdr mode.

[How]
after embeded hw_fence into amdgpu_job is done, the race condition that
this commit tries to work around is completely solved.So revert this
commit.
This reverts commit 135517d3565b48f4def3b1b82008bc17eb5d1c90.
v2:
add dma_fence_get/put() around timedout_job to avoid  concurrent delete
during processing timedout_job
v3:
park sched->thread instead during timedout_job.

Signed-off-by: Jingwen Chen <Jingwen.Chen2 at amd.com>
---
 drivers/gpu/drm/scheduler/sched_main.c | 22 ++--------------------
 1 file changed, 2 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index a2a953693b45..c187fd3a6bb6 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -319,17 +319,12 @@ static void drm_sched_job_timedout(struct work_struct *work)
 	sched = container_of(work, struct drm_gpu_scheduler, work_tdr.work);
 
 	/* Protects against concurrent deletion in drm_sched_get_cleanup_job */
+	kthread_park(sched->thread);
 	spin_lock(&sched->job_list_lock);
 	job = list_first_entry_or_null(&sched->pending_list,
 				       struct drm_sched_job, list);
 
 	if (job) {
-		/*
-		 * Remove the bad job so it cannot be freed by concurrent
-		 * drm_sched_cleanup_jobs. It will be reinserted back after sched->thread
-		 * is parked at which point it's safe.
-		 */
-		list_del_init(&job->list);
 		spin_unlock(&sched->job_list_lock);
 
 		status = job->sched->ops->timedout_job(job);
@@ -345,6 +340,7 @@ static void drm_sched_job_timedout(struct work_struct *work)
 	} else {
 		spin_unlock(&sched->job_list_lock);
 	}
+	kthread_unpark(sched->thread);
 
 	if (status != DRM_GPU_SCHED_STAT_ENODEV) {
 		spin_lock(&sched->job_list_lock);
@@ -392,20 +388,6 @@ void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
 
 	kthread_park(sched->thread);
 
-	/*
-	 * Reinsert back the bad job here - now it's safe as
-	 * drm_sched_get_cleanup_job cannot race against us and release the
-	 * bad job at this point - we parked (waited for) any in progress
-	 * (earlier) cleanups and drm_sched_get_cleanup_job will not be called
-	 * now until the scheduler thread is unparked.
-	 */
-	if (bad && bad->sched == sched)
-		/*
-		 * Add at the head of the queue to reflect it was the earliest
-		 * job extracted.
-		 */
-		list_add(&bad->list, &sched->pending_list);
-
 	/*
 	 * Iterate the job list from later to  earlier one and either deactive
 	 * their HW callbacks or remove them from pending list if they already
-- 
2.25.1