Re: [PATCH v4 3/5] drm/scheduler: rework job destruction

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I can't review this patch, since I'm one of the authors of it, but in general your changes look good to me now.

For patch #5 I think it might be cleaner if we move incrementing of the hw_rq_count while starting the scheduler again.

Regards,
Christian.

Am 17.04.19 um 16:36 schrieb Grodzovsky, Andrey:
Ping on this patch and patch 5. The rest already RBed.

Andrey

On 4/16/19 2:23 PM, Andrey Grodzovsky wrote:
From: Christian König <christian.koenig@xxxxxxx>

We now destroy finished jobs from the worker thread to make sure that
we never destroy a job currently in timeout processing.
By this we avoid holding lock around ring mirror list in drm_sched_stop
which should solve a deadlock reported by a user.

v2: Remove unused variable.
v4: Move guilty job free into sched code.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109692

Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
---
   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |   9 +-
   drivers/gpu/drm/etnaviv/etnaviv_dump.c     |   4 -
   drivers/gpu/drm/etnaviv/etnaviv_sched.c    |   2 +-
   drivers/gpu/drm/lima/lima_sched.c          |   2 +-
   drivers/gpu/drm/panfrost/panfrost_job.c    |   2 +-
   drivers/gpu/drm/scheduler/sched_main.c     | 145 +++++++++++++++++------------
   drivers/gpu/drm/v3d/v3d_sched.c            |   2 +-
   include/drm/gpu_scheduler.h                |   6 +-
   8 files changed, 94 insertions(+), 78 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 7cee269..a0e165c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -3334,7 +3334,7 @@ static int amdgpu_device_pre_asic_reset(struct amdgpu_device *adev,
   		if (!ring || !ring->sched.thread)
   			continue;
- drm_sched_stop(&ring->sched);
+		drm_sched_stop(&ring->sched, &job->base);
/* after all hw jobs are reset, hw fence is meaningless, so force_completion */
   		amdgpu_fence_driver_force_completion(ring);
@@ -3343,8 +3343,6 @@ static int amdgpu_device_pre_asic_reset(struct amdgpu_device *adev,
   	if(job)
   		drm_sched_increase_karma(&job->base);
-
-
   	if (!amdgpu_sriov_vf(adev)) {
if (!need_full_reset)
@@ -3482,8 +3480,7 @@ static int amdgpu_do_asic_reset(struct amdgpu_hive_info *hive,
   	return r;
   }
-static void amdgpu_device_post_asic_reset(struct amdgpu_device *adev,
-					  struct amdgpu_job *job)
+static void amdgpu_device_post_asic_reset(struct amdgpu_device *adev)
   {
   	int i;
@@ -3623,7 +3620,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev, /* Post ASIC reset for all devs .*/
   	list_for_each_entry(tmp_adev, device_list_handle, gmc.xgmi.head) {
-		amdgpu_device_post_asic_reset(tmp_adev, tmp_adev == adev ? job : NULL);
+		amdgpu_device_post_asic_reset(tmp_adev);
if (r) {
   			/* bad news, how to tell it to userspace ? */
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_dump.c b/drivers/gpu/drm/etnaviv/etnaviv_dump.c
index 33854c9..5778d9c 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_dump.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_dump.c
@@ -135,13 +135,11 @@ void etnaviv_core_dump(struct etnaviv_gpu *gpu)
   		    mmu_size + gpu->buffer.size;
/* Add in the active command buffers */
-	spin_lock_irqsave(&gpu->sched.job_list_lock, flags);
   	list_for_each_entry(s_job, &gpu->sched.ring_mirror_list, node) {
   		submit = to_etnaviv_submit(s_job);
   		file_size += submit->cmdbuf.size;
   		n_obj++;
   	}
-	spin_unlock_irqrestore(&gpu->sched.job_list_lock, flags);
/* Add in the active buffer objects */
   	list_for_each_entry(vram, &gpu->mmu->mappings, mmu_node) {
@@ -183,14 +181,12 @@ void etnaviv_core_dump(struct etnaviv_gpu *gpu)
   			      gpu->buffer.size,
   			      etnaviv_cmdbuf_get_va(&gpu->buffer));
- spin_lock_irqsave(&gpu->sched.job_list_lock, flags);
   	list_for_each_entry(s_job, &gpu->sched.ring_mirror_list, node) {
   		submit = to_etnaviv_submit(s_job);
   		etnaviv_core_dump_mem(&iter, ETDUMP_BUF_CMD,
   				      submit->cmdbuf.vaddr, submit->cmdbuf.size,
   				      etnaviv_cmdbuf_get_va(&submit->cmdbuf));
   	}
-	spin_unlock_irqrestore(&gpu->sched.job_list_lock, flags);
/* Reserve space for the bomap */
   	if (n_bomap_pages) {
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_sched.c b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
index 6d24fea..a813c82 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_sched.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_sched.c
@@ -109,7 +109,7 @@ static void etnaviv_sched_timedout_job(struct drm_sched_job *sched_job)
   	}
/* block scheduler */
-	drm_sched_stop(&gpu->sched);
+	drm_sched_stop(&gpu->sched, sched_job);
if(sched_job)
   		drm_sched_increase_karma(sched_job);
diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
index 97bd9c1..df98931 100644
--- a/drivers/gpu/drm/lima/lima_sched.c
+++ b/drivers/gpu/drm/lima/lima_sched.c
@@ -300,7 +300,7 @@ static struct dma_fence *lima_sched_run_job(struct drm_sched_job *job)
   static void lima_sched_handle_error_task(struct lima_sched_pipe *pipe,
   					 struct lima_sched_task *task)
   {
-	drm_sched_stop(&pipe->base);
+	drm_sched_stop(&pipe->base, &task->base);
if (task)
   		drm_sched_increase_karma(&task->base);
diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c b/drivers/gpu/drm/panfrost/panfrost_job.c
index 0a7ed04..c6336b7 100644
--- a/drivers/gpu/drm/panfrost/panfrost_job.c
+++ b/drivers/gpu/drm/panfrost/panfrost_job.c
@@ -385,7 +385,7 @@ static void panfrost_job_timedout(struct drm_sched_job *sched_job)
   		sched_job);
for (i = 0; i < NUM_JOB_SLOTS; i++)
-		drm_sched_stop(&pfdev->js->queue[i].sched);
+		drm_sched_stop(&pfdev->js->queue[i].sched, sched_job);
if (sched_job)
   		drm_sched_increase_karma(sched_job);
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 19fc601..21e8734 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -265,32 +265,6 @@ void drm_sched_resume_timeout(struct drm_gpu_scheduler *sched,
   }
   EXPORT_SYMBOL(drm_sched_resume_timeout);
-/* job_finish is called after hw fence signaled
- */
-static void drm_sched_job_finish(struct work_struct *work)
-{
-	struct drm_sched_job *s_job = container_of(work, struct drm_sched_job,
-						   finish_work);
-	struct drm_gpu_scheduler *sched = s_job->sched;
-	unsigned long flags;
-
-	/*
-	 * Canceling the timeout without removing our job from the ring mirror
-	 * list is safe, as we will only end up in this worker if our jobs
-	 * finished fence has been signaled. So even if some another worker
-	 * 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(&sched->work_tdr);
-
-	spin_lock_irqsave(&sched->job_list_lock, flags);
-	/* queue TDR for next job */
-	drm_sched_start_timeout(sched);
-	spin_unlock_irqrestore(&sched->job_list_lock, flags);
-
-	sched->ops->free_job(s_job);
-}
-
   static void drm_sched_job_begin(struct drm_sched_job *s_job)
   {
   	struct drm_gpu_scheduler *sched = s_job->sched;
@@ -315,6 +289,13 @@ static void drm_sched_job_timedout(struct work_struct *work)
   	if (job)
   		job->sched->ops->timedout_job(job);
+ /*
+	 * Guilty job did complete and hence needs to be manually removed
+	 * See drm_sched_stop doc.
+	 */
+	if (list_empty(&job->node))
+		job->sched->ops->free_job(job);
+
   	spin_lock_irqsave(&sched->job_list_lock, flags);
   	drm_sched_start_timeout(sched);
   	spin_unlock_irqrestore(&sched->job_list_lock, flags);
@@ -371,23 +352,26 @@ EXPORT_SYMBOL(drm_sched_increase_karma);
    * @sched: scheduler instance
    * @bad: bad scheduler job
    *
+ * Stop the scheduler and also removes and frees all completed jobs.
+ * Note: bad job will not be freed as it might be used later and so it's
+ * callers responsibility to release it manually if it's not part of the
+ * mirror list any more.
+ *
    */
-void drm_sched_stop(struct drm_gpu_scheduler *sched)
+void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)
   {
-	struct drm_sched_job *s_job;
+	struct drm_sched_job *s_job, *tmp;
   	unsigned long flags;
-	struct dma_fence *last_fence =  NULL;
kthread_park(sched->thread); /*
-	 * Verify all the signaled jobs in mirror list are removed from the ring
-	 * by waiting for the latest job to enter the list. This should insure that
-	 * also all the previous jobs that were in flight also already singaled
-	 * and removed from the list.
+	 * Iterate the job list from later to  earlier one and either deactive
+	 * their HW callbacks or remove them from mirror list if they already
+	 * signaled.
+	 * This iteration is thread safe as sched thread is stopped.
   	 */
-	spin_lock_irqsave(&sched->job_list_lock, flags);
-	list_for_each_entry_reverse(s_job, &sched->ring_mirror_list, node) {
+	list_for_each_entry_safe_reverse(s_job, tmp, &sched->ring_mirror_list, node) {
   		if (s_job->s_fence->parent &&
   		    dma_fence_remove_callback(s_job->s_fence->parent,
   					      &s_job->cb)) {
@@ -395,16 +379,30 @@ void drm_sched_stop(struct drm_gpu_scheduler *sched)
   			s_job->s_fence->parent = NULL;
   			atomic_dec(&sched->hw_rq_count);
   		} else {
-			 last_fence = dma_fence_get(&s_job->s_fence->finished);
-			 break;
+			/*
+			 * remove job from ring_mirror_list.
+			 * Locking here is for concurrent resume timeout
+			 */
+			spin_lock_irqsave(&sched->job_list_lock, flags);
+			list_del_init(&s_job->node);
+			spin_unlock_irqrestore(&sched->job_list_lock, flags);
+
+			/*
+			 * Wait for job's HW fence callback to finish using s_job
+			 * before releasing it.
+			 *
+			 * Job is still alive so fence refcount at least 1
+			 */
+			dma_fence_wait(&s_job->s_fence->finished, false);
+
+			/*
+			 * We must keep bad job alive for later use during
+			 * recovery by some of the drivers
+			 */
+			if (bad != s_job)
+				sched->ops->free_job(s_job);
   		}
   	}
-	spin_unlock_irqrestore(&sched->job_list_lock, flags);
-
-	if (last_fence) {
-		dma_fence_wait(last_fence, false);
-		dma_fence_put(last_fence);
-	}
   }
EXPORT_SYMBOL(drm_sched_stop);
@@ -418,6 +416,7 @@ EXPORT_SYMBOL(drm_sched_stop);
   void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
   {
   	struct drm_sched_job *s_job, *tmp;
+	unsigned long flags;
   	int r;
if (!full_recovery)
@@ -425,9 +424,7 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
/*
   	 * Locking the list is not required here as the sched thread is parked
-	 * so no new jobs are being pushed in to HW and in drm_sched_stop we
-	 * flushed all the jobs who were still in mirror list but who already
-	 * signaled and removed them self from the list. Also concurrent
+	 * so no new jobs are being inserted or removed. Also concurrent
   	 * GPU recovers can't run in parallel.
   	 */
   	list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list, node) {
@@ -445,7 +442,9 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
   			drm_sched_process_job(NULL, &s_job->cb);
   	}
+ spin_lock_irqsave(&sched->job_list_lock, flags);
   	drm_sched_start_timeout(sched);
+	spin_unlock_irqrestore(&sched->job_list_lock, flags);
unpark:
   	kthread_unpark(sched->thread);
@@ -464,7 +463,6 @@ void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched)
   	uint64_t guilty_context;
   	bool found_guilty = false;
- /*TODO DO we need spinlock here ? */
   	list_for_each_entry_safe(s_job, tmp, &sched->ring_mirror_list, node) {
   		struct drm_sched_fence *s_fence = s_job->s_fence;
@@ -514,7 +512,6 @@ int drm_sched_job_init(struct drm_sched_job *job,
   		return -ENOMEM;
   	job->id = atomic64_inc_return(&sched->job_id_count);
- INIT_WORK(&job->finish_work, drm_sched_job_finish);
   	INIT_LIST_HEAD(&job->node);
return 0;
@@ -597,24 +594,53 @@ static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb)
   	struct drm_sched_job *s_job = container_of(cb, struct drm_sched_job, cb);
   	struct drm_sched_fence *s_fence = s_job->s_fence;
   	struct drm_gpu_scheduler *sched = s_fence->sched;
-	unsigned long flags;
-
-	cancel_delayed_work(&sched->work_tdr);
atomic_dec(&sched->hw_rq_count);
   	atomic_dec(&sched->num_jobs);
- spin_lock_irqsave(&sched->job_list_lock, flags);
-	/* remove job from ring_mirror_list */
-	list_del_init(&s_job->node);
-	spin_unlock_irqrestore(&sched->job_list_lock, flags);
+	trace_drm_sched_process_job(s_fence);
drm_sched_fence_finished(s_fence);
-
-	trace_drm_sched_process_job(s_fence);
   	wake_up_interruptible(&sched->wake_up_worker);
+}
+
+/**
+ * drm_sched_cleanup_jobs - destroy finished jobs
+ *
+ * @sched: scheduler instance
+ *
+ * Remove all finished jobs from the mirror list and destroy them.
+ */
+static void drm_sched_cleanup_jobs(struct drm_gpu_scheduler *sched)
+{
+	unsigned long flags;
+
+	/* Don't destroy jobs while the timeout worker is running */
+	if (!cancel_delayed_work(&sched->work_tdr))
+		return;
+
+
+	while (!list_empty(&sched->ring_mirror_list)) {
+		struct drm_sched_job *job;
+
+		job = list_first_entry(&sched->ring_mirror_list,
+				       struct drm_sched_job, node);
+		if (!dma_fence_is_signaled(&job->s_fence->finished))
+			break;
+
+		spin_lock_irqsave(&sched->job_list_lock, flags);
+		/* remove job from ring_mirror_list */
+		list_del_init(&job->node);
+		spin_unlock_irqrestore(&sched->job_list_lock, flags);
+
+		sched->ops->free_job(job);
+	}
+
+	/* queue timeout for next job */
+	spin_lock_irqsave(&sched->job_list_lock, flags);
+	drm_sched_start_timeout(sched);
+	spin_unlock_irqrestore(&sched->job_list_lock, flags);
- schedule_work(&s_job->finish_work);
   }
/**
@@ -656,9 +682,10 @@ static int drm_sched_main(void *param)
   		struct dma_fence *fence;
wait_event_interruptible(sched->wake_up_worker,
+					 (drm_sched_cleanup_jobs(sched),
   					 (!drm_sched_blocked(sched) &&
   					  (entity = drm_sched_select_entity(sched))) ||
-					 kthread_should_stop());
+					 kthread_should_stop()));
if (!entity)
   			continue;
diff --git a/drivers/gpu/drm/v3d/v3d_sched.c b/drivers/gpu/drm/v3d/v3d_sched.c
index e740f3b..1a4abe7 100644
--- a/drivers/gpu/drm/v3d/v3d_sched.c
+++ b/drivers/gpu/drm/v3d/v3d_sched.c
@@ -232,7 +232,7 @@ v3d_gpu_reset_for_timeout(struct v3d_dev *v3d, struct drm_sched_job *sched_job)
/* block scheduler */
   	for (q = 0; q < V3D_MAX_QUEUES; q++)
-		drm_sched_stop(&v3d->queue[q].sched);
+		drm_sched_stop(&v3d->queue[q].sched, sched_job);
if (sched_job)
   		drm_sched_increase_karma(sched_job);
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index 0daca4d..9ee0f27 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -167,9 +167,6 @@ struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
    * @sched: the scheduler instance on which this job is scheduled.
    * @s_fence: contains the fences for the scheduling of job.
    * @finish_cb: the callback for the finished fence.
- * @finish_work: schedules the function @drm_sched_job_finish once the job has
- *               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.
    * @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
@@ -188,7 +185,6 @@ struct drm_sched_job {
   	struct drm_gpu_scheduler	*sched;
   	struct drm_sched_fence		*s_fence;
   	struct dma_fence_cb		finish_cb;
-	struct work_struct		finish_work;
   	struct list_head		node;
   	uint64_t			id;
   	atomic_t			karma;
@@ -296,7 +292,7 @@ int drm_sched_job_init(struct drm_sched_job *job,
   		       void *owner);
   void drm_sched_job_cleanup(struct drm_sched_job *job);
   void drm_sched_wakeup(struct drm_gpu_scheduler *sched);
-void drm_sched_stop(struct drm_gpu_scheduler *sched);
+void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad);
   void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery);
   void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched);
   void drm_sched_increase_karma(struct drm_sched_job *bad);

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