drm/amdgpu: make userq fence_drv drop explicit in queue destroy

amdgpu_userq_fence_driver_free() is now responsible only for releasing
per-queue ancillary state (last_fence, fence_drv_xa) and no longer
touches the ownership reference, making each function's contract clear.

v2: Get the userq fence driver from amdgpu_userq_fence_driver_alloc()
    directly and dropping the userq fence driver reference after removing
    userq_doorbell_xa entry.(Christian)

Signed-off-by: Prike Liang <Prike.Liang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: prliangpub

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

@@ -449,9 +449,10 @@ static void amdgpu_userq_cleanup(struct amdgpu_usermode_queue *queue)
 	/* Drop the userq reference. */
 	amdgpu_userq_buffer_vas_list_cleanup(adev, queue);
 	uq_funcs->mqd_destroy(queue);
-	amdgpu_userq_fence_driver_free(queue);
 	/* Use interrupt-safe locking since IRQ handlers may access these XArrays */
 	xa_erase_irq(&adev->userq_doorbell_xa, queue->doorbell_index);
+	amdgpu_userq_fence_driver_free(queue);
+	queue->fence_drv = NULL;
 	queue->userq_mgr = NULL;
 	list_del(&queue->userq_va_list);
 	kfree(queue);
@@ -790,7 +791,7 @@ amdgpu_userq_create(struct drm_file *filp, union drm_amdgpu_userq *args)
 
 	queue->doorbell_index = index;
 	xa_init_flags(&queue->fence_drv_xa, XA_FLAGS_ALLOC);
-	r = amdgpu_userq_fence_driver_alloc(adev, queue);
+	r = amdgpu_userq_fence_driver_alloc(adev, &queue->fence_drv);
 	if (r) {
 		drm_file_err(uq_mgr->file, "Failed to alloc fence driver\n");
 		goto free_queue;

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

@@ -78,11 +78,15 @@ amdgpu_userq_fence_write(struct amdgpu_userq_fence_driver *fence_drv,
 }
 
 int amdgpu_userq_fence_driver_alloc(struct amdgpu_device *adev,
-				    struct amdgpu_usermode_queue *userq)
+				    struct amdgpu_userq_fence_driver **fence_drv_req)
 {
 	struct amdgpu_userq_fence_driver *fence_drv;
 	int r;
 
+	if (!fence_drv_req)
+		return -EINVAL;
+	*fence_drv_req = NULL;
+
 	fence_drv = kzalloc_obj(*fence_drv);
 	if (!fence_drv)
 		return -ENOMEM;
@@ -103,7 +107,7 @@ int amdgpu_userq_fence_driver_alloc(struct amdgpu_device *adev,
 	fence_drv->context = dma_fence_context_alloc(1);
 	get_task_comm(fence_drv->timeline_name, current);
 
-	userq->fence_drv = fence_drv;
+	*fence_drv_req = fence_drv;
 
 	return 0;
 
@@ -134,10 +138,10 @@ void
 amdgpu_userq_fence_driver_free(struct amdgpu_usermode_queue *userq)
 {
 	dma_fence_put(userq->last_fence);
-
+	userq->last_fence = NULL;
 	amdgpu_userq_walk_and_drop_fence_drv(&userq->fence_drv_xa);
 	xa_destroy(&userq->fence_drv_xa);
-	/* Drop the fence_drv reference held by user queue */
+	/* Drop the queue's ownership reference to fence_drv explicitly */
 	amdgpu_userq_fence_driver_put(userq->fence_drv);
 }
 

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

@@ -64,7 +64,7 @@ void amdgpu_userq_fence_slab_fini(void);
 void amdgpu_userq_fence_driver_get(struct amdgpu_userq_fence_driver *fence_drv);
 void amdgpu_userq_fence_driver_put(struct amdgpu_userq_fence_driver *fence_drv);
 int amdgpu_userq_fence_driver_alloc(struct amdgpu_device *adev,
-				    struct amdgpu_usermode_queue *userq);
+				    struct amdgpu_userq_fence_driver **fence_drv_req);
 void amdgpu_userq_fence_driver_free(struct amdgpu_usermode_queue *userq);
 void amdgpu_userq_fence_driver_process(struct amdgpu_userq_fence_driver *fence_drv);
 void amdgpu_userq_fence_driver_force_completion(struct amdgpu_usermode_queue *userq);