Re: [PATCH v5 3/6] drm/scheduler: rework job destruction

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Hi Andrey,

static void drm_sched_process_job(struct dma_fence *f, struct 
dma_fence_cb *cb)
{
...
         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);
[David] How about just remove above to worker from irq process? Any 
problem? Maybe I missed previous your discussion, but I think removing 
lock for list is a risk for future maintenance although you make sure 
thread safe currently.

-David

...

         schedule_work(&s_job->finish_work);
}

在 2019/4/18 23:00, Andrey Grodzovsky 写道:
> 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.
> v5:
> Move sched->hw_rq_count to drm_sched_start to account for counter
> decrement in drm_sched_stop even when we don't call resubmit jobs
> if guily job did signal.
>
> 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     | 159 +++++++++++++++++------------
>   drivers/gpu/drm/v3d/v3d_sched.c            |   2 +-
>   include/drm/gpu_scheduler.h                |   6 +-
>   8 files changed, 102 insertions(+), 84 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..7816de7 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);
> @@ -418,21 +416,22 @@ 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)
> -		goto unpark;
> -
>   	/*
>   	 * 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) {
>   		struct dma_fence *fence = s_job->s_fence->parent;
>   
> +		atomic_inc(&sched->hw_rq_count);
> +
> +		if (!full_recovery)
> +			continue;
> +
>   		if (fence) {
>   			r = dma_fence_add_callback(fence, &s_job->cb,
>   						   drm_sched_process_job);
> @@ -445,9 +444,12 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)
>   			drm_sched_process_job(NULL, &s_job->cb);
>   	}
>   
> -	drm_sched_start_timeout(sched);
> +	if (full_recovery) {
> +		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);
>   }
>   EXPORT_SYMBOL(drm_sched_start);
> @@ -464,7 +466,6 @@ 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;
>   
> @@ -477,7 +478,6 @@ void drm_sched_resubmit_jobs(struct drm_gpu_scheduler *sched)
>   			dma_fence_set_error(&s_fence->finished, -ECANCELED);
>   
>   		s_job->s_fence->parent = sched->ops->run_job(s_job);
> -		atomic_inc(&sched->hw_rq_count);
>   	}
>   }
>   EXPORT_SYMBOL(drm_sched_resubmit_jobs);
> @@ -514,7 +514,6 @@ 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 +596,53 @@ 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 +684,10 @@ 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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