Re: [PATCH v2] drm/scheduler: remove timeout work_struct from drm_sched_job

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Am 26.09.2018 um 09:39 schrieb Lucas Stach:
Hi Nayan,

Am Mittwoch, den 26.09.2018, 02:09 +0900 schrieb Nayan Deshmukh:
having a delayed work item per job is redundant as we only need one
per scheduler to track the time out the currently executing job.

v2: the first element of the ring mirror list is the currently
executing job so we don't need a additional variable for it

Signed-off-by: Nayan Deshmukh <nayan26deshmukh@xxxxxxxxx>
Suggested-by: Christian König <christian.koenig@xxxxxxx>
---
  drivers/gpu/drm/scheduler/sched_main.c | 31 ++++++++++++++++---------------
  include/drm/gpu_scheduler.h            |  6 +++---
  2 files changed, 19 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 9ca741f3a0bc..4e8505d51795 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -197,19 +197,15 @@ static void drm_sched_job_finish(struct work_struct *work)
  	 * manages to find this job as the next job in the list, the fence
  	 * signaled check below will prevent the timeout to be restarted.
  	 */
-	cancel_delayed_work_sync(&s_job->work_tdr);
+	cancel_delayed_work_sync(&sched->work_tdr);
spin_lock(&sched->job_list_lock);
-	/* queue TDR for next job */
-	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
-	    !list_is_last(&s_job->node, &sched->ring_mirror_list)) {
-		struct drm_sched_job *next = list_next_entry(s_job, node);
-
-		if (!dma_fence_is_signaled(&next->s_fence->finished))
-			schedule_delayed_work(&next->work_tdr, sched->timeout);
-	}
  	/* remove job from ring_mirror_list */
  	list_del(&s_job->node);
+	/* queue TDR for next job */
+	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
+	    !list_empty(&sched->ring_mirror_list))
+		schedule_delayed_work(&sched->work_tdr, sched->timeout);
  	spin_unlock(&sched->job_list_lock);
dma_fence_put(&s_job->s_fence->finished);
@@ -236,16 +232,21 @@ static void drm_sched_job_begin(struct drm_sched_job *s_job)
  	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
  	    list_first_entry_or_null(&sched->ring_mirror_list,
  				     struct drm_sched_job, node) == s_job)
-		schedule_delayed_work(&s_job->work_tdr, sched->timeout);
+		schedule_delayed_work(&sched->work_tdr, sched->timeout);
  	spin_unlock(&sched->job_list_lock);
  }
static void drm_sched_job_timedout(struct work_struct *work)
  {
-	struct drm_sched_job *job = container_of(work, struct drm_sched_job,
-						 work_tdr.work);
+	struct drm_gpu_scheduler *sched;
+	struct drm_sched_job *job;
+
+	sched = container_of(work, struct drm_gpu_scheduler, work_tdr.work);
+	job = list_first_entry_or_null(&sched->ring_mirror_list,
+				       struct drm_sched_job, node);
- job->sched->ops->timedout_job(job);
+	if (job)
+		job->sched->ops->timedout_job(job);
I don't think this is fully robust. Jobs are only removed from the
ring_mirror_list once the job_finish worker has run. If execution of
this worker is delayed for any reason (though it's really unlikely for
a delay as long as the job timeout to happen) you are blaming the wrong
job here.

So I think what you need to to is find the first job in the ring mirror
list with an unsignaled finish fence to robustly find the stuck job.

Yeah, that is a known problem I've pointed out as well.

The issue is we have bug reports that this happened before the patch, but I'm not 100% sure how.

My suggestion is to move a good part of the logic from drm_sched_hw_job_reset() and drm_sched_job_recovery() into drm_sched_job_timedout().

E.g. we first call dma_fence_remove_callback() for each job and actually check the return value if the fence was already signaled.

If we find a signaled fence we abort and add the callback back to the ones where we removed it.

Nayan do you want to take care of this or should I take a look?

Regards,
Christian.


Regards,
Lucas

  }
/**
@@ -315,7 +316,7 @@ void drm_sched_job_recovery(struct drm_gpu_scheduler *sched)
  	s_job = list_first_entry_or_null(&sched->ring_mirror_list,
  					 struct drm_sched_job, node);
  	if (s_job && sched->timeout != MAX_SCHEDULE_TIMEOUT)
-		schedule_delayed_work(&s_job->work_tdr, sched->timeout);
+		schedule_delayed_work(&sched->work_tdr, sched->timeout);
list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list, node) {
  		struct drm_sched_fence *s_fence = s_job->s_fence;
@@ -384,7 +385,6 @@ int drm_sched_job_init(struct drm_sched_job *job,
INIT_WORK(&job->finish_work, drm_sched_job_finish);
  	INIT_LIST_HEAD(&job->node);
-	INIT_DELAYED_WORK(&job->work_tdr, drm_sched_job_timedout);
return 0;
  }
@@ -575,6 +575,7 @@ int drm_sched_init(struct drm_gpu_scheduler *sched,
  	INIT_LIST_HEAD(&sched->ring_mirror_list);
  	spin_lock_init(&sched->job_list_lock);
  	atomic_set(&sched->hw_rq_count, 0);
+	INIT_DELAYED_WORK(&sched->work_tdr, drm_sched_job_timedout);
  	atomic_set(&sched->num_jobs, 0);
  	atomic64_set(&sched->job_id_count, 0);
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index daec50f887b3..d87b268f1781 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -175,8 +175,6 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
   *               finished to remove the job from the
   *               @drm_gpu_scheduler.ring_mirror_list.
   * @node: used to append this struct to the @drm_gpu_scheduler.ring_mirror_list.
- * @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the timeout
- *            interval is over.
   * @id: a unique id assigned to each job scheduled on the scheduler.
   * @karma: increment on every hang caused by this job. If this exceeds the hang
   *         limit of the scheduler then the job is marked guilty and will not
@@ -195,7 +193,6 @@ struct drm_sched_job {
  	struct dma_fence_cb		finish_cb;
  	struct work_struct		finish_work;
  	struct list_head		node;
-	struct delayed_work		work_tdr;
  	uint64_t			id;
  	atomic_t			karma;
  	enum drm_sched_priority		s_priority;
@@ -259,6 +256,8 @@ 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.
+ * @work_tdr: schedules a delayed call to @drm_sched_job_timedout after the
+ *            timeout interval is over.
   * @thread: the kthread on which the scheduler which run.
   * @ring_mirror_list: the list of jobs which are currently in the job queue.
   * @job_list_lock: lock to protect the ring_mirror_list.
@@ -278,6 +277,7 @@ struct drm_gpu_scheduler {
  	wait_queue_head_t		job_scheduled;
  	atomic_t			hw_rq_count;
  	atomic64_t			job_id_count;
+	struct delayed_work		work_tdr;
  	struct task_struct		*thread;
  	struct list_head		ring_mirror_list;
  	spinlock_t			job_list_lock;
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