drm/ttm: lock resv object during destruction

Calling ttm_bo_cleanup_memtype_use() destroys the TT object
which in turn could result in warnings without this.
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/359288

drivers/gpu/drm/ttm/ttm_bo.c

@@ -588,7 +588,8 @@ static void ttm_bo_release(struct kref *kref)
 		ttm_mem_io_unlock(man);
 	}
 
-	if (!dma_resv_test_signaled_rcu(bo->base.resv, true)) {
+	if (!dma_resv_test_signaled_rcu(bo->base.resv, true) ||
+	    !dma_resv_trylock(bo->base.resv)) {
 		/* The BO is not idle, resurrect it for delayed destroy */
 		ttm_bo_flush_all_fences(bo);
 		bo->deleted = true;
@@ -621,6 +622,7 @@ static void ttm_bo_release(struct kref *kref)
 	spin_unlock(&ttm_bo_glob.lru_lock);
 
 	ttm_bo_cleanup_memtype_use(bo);
+	dma_resv_unlock(bo->base.resv);
 
 	BUG_ON(bo->mem.mm_node != NULL);
 	atomic_dec(&ttm_bo_glob.bo_count);