drm/amdgpu: use ref to keep job alive

this is to fix fatal page fault error that occured if:
job is signaled/released after its timeout work is already
put to the global queue (in this case the cancel_delayed_work
will return false), which will lead to NX-protection error
page fault during job_timeout_func.

Signed-off-by: Monk Liu <[e-mail]>
Reviewed-by: Chunming Zhou <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu.h

···
 		     struct amdgpu_job **job);
 int amdgpu_job_alloc_with_ib(struct amdgpu_device *adev, unsigned size,
 			     struct amdgpu_job **job);
+
 void amdgpu_job_free(struct amdgpu_job *job);
+void amdgpu_job_free_func(struct kref *refcount);
 int amdgpu_job_submit(struct amdgpu_job *job, struct amdgpu_ring *ring,
 		      struct amd_sched_entity *entity, void *owner,
 		      struct fence **f);

drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c

···
 	r = amd_sched_job_init(&job->base, &ring->sched,
 						&p->ctx->rings[ring->idx].entity,
 						amdgpu_job_timeout_func,
+						amdgpu_job_free_func,
 						p->filp, &fence);
 	if (r) {
 		amdgpu_job_free(job);

drivers/gpu/drm/amd/amdgpu/amdgpu_job.c

···
 static void amdgpu_job_free_handler(struct work_struct *ws)
 {
 	struct amdgpu_job *job = container_of(ws, struct amdgpu_job, base.work_free_job);
-	kfree(job);
+	amd_sched_job_put(&job->base);
 }
 
 void amdgpu_job_timeout_func(struct work_struct *work)
···
 				job->base.sched->name,
 				(uint32_t)atomic_read(&job->ring->fence_drv.last_seq),
 				job->ring->fence_drv.sync_seq);
+
+	amd_sched_job_put(&job->base);
 }
 
 int amdgpu_job_alloc(struct amdgpu_device *adev, unsigned num_ibs,
···
 		kfree(job);
 }
 
+void amdgpu_job_free_func(struct kref *refcount)
+{
+	struct amdgpu_job *job = container_of(refcount, struct amdgpu_job, base.refcount);
+	kfree(job);
+}
+
 int amdgpu_job_submit(struct amdgpu_job *job, struct amdgpu_ring *ring,
 		      struct amd_sched_entity *entity, void *owner,
 		      struct fence **f)
···
 		return -EINVAL;
 
 	r = amd_sched_job_init(&job->base, &ring->sched,
-							entity, owner,
+							entity,
 							amdgpu_job_timeout_func,
-							&fence);
+							amdgpu_job_free_func,
+							owner, &fence);
 	if (r)
 		return r;
 

drivers/gpu/drm/amd/scheduler/gpu_scheduler.c

···
 	struct amd_gpu_scheduler *sched = s_job->sched;
 
 	if (sched->timeout != MAX_SCHEDULE_TIMEOUT) {
-		cancel_delayed_work(&s_job->work_tdr); /*TODO: how to deal the case that tdr is running */
+		if (cancel_delayed_work(&s_job->work_tdr))
+			amd_sched_job_put(s_job);
 
 		/* queue TDR for next job */
 		next = list_first_entry_or_null(&sched->ring_mirror_list,
···
 
 		if (next) {
 			INIT_DELAYED_WORK(&next->work_tdr, s_job->timeout_callback);
+			amd_sched_job_get(next);
 			schedule_delayed_work(&next->work_tdr, sched->timeout);
 		}
 	}
···
 		list_first_entry_or_null(&sched->ring_mirror_list, struct amd_sched_job, node) == s_job)
 	{
 		INIT_DELAYED_WORK(&s_job->work_tdr, s_job->timeout_callback);
+		amd_sched_job_get(s_job);
 		schedule_delayed_work(&s_job->work_tdr, sched->timeout);
 	}
 }
···
 						struct amd_gpu_scheduler *sched,
 						struct amd_sched_entity *entity,
 						void (*timeout_cb)(struct work_struct *work),
+						void (*free_cb)(struct kref *refcount),
 						void *owner, struct fence **fence)
 {
 	INIT_LIST_HEAD(&job->node);
+	kref_init(&job->refcount);
 	job->sched = sched;
 	job->s_entity = entity;
 	job->s_fence = amd_sched_fence_create(entity, owner);
···
 
 	job->s_fence->s_job = job;
 	job->timeout_callback = timeout_cb;
+	job->free_callback = free_cb;
 
 	if (fence)
 		*fence = &job->s_fence->base;

drivers/gpu/drm/amd/scheduler/gpu_scheduler.h

···
 };
 
 struct amd_sched_job {
+	struct kref refcount;
 	struct amd_gpu_scheduler        *sched;
 	struct amd_sched_entity         *s_entity;
 	struct amd_sched_fence          *s_fence;
···
 	struct list_head			   node;
 	struct delayed_work work_tdr;
 	void (*timeout_callback) (struct work_struct *work);
+	void (*free_callback)(struct kref *refcount);
 };
 
 extern const struct fence_ops amd_sched_fence_ops;
···
 					struct amd_gpu_scheduler *sched,
 					struct amd_sched_entity *entity,
 					void (*timeout_cb)(struct work_struct *work),
+					void (*free_cb)(struct kref* refcount),
 					void *owner, struct fence **fence);
 void amd_sched_job_pre_schedule(struct amd_gpu_scheduler *sched ,
 								struct amd_sched_job *s_job);
 void amd_sched_job_finish(struct amd_sched_job *s_job);
 void amd_sched_job_begin(struct amd_sched_job *s_job);
+static inline void amd_sched_job_get(struct amd_sched_job *job) {
+	if (job)
+		kref_get(&job->refcount);
+}
+
+static inline void amd_sched_job_put(struct amd_sched_job *job) {
+	if (job)
+		kref_put(&job->refcount, job->free_callback);
+}
+
 #endif