--- x/drivers/gpu/drm/drm_atomic_helper.c
+++ y/drivers/gpu/drm/drm_atomic_helper.c
@@ -1849,7 +1849,11 @@ static void commit_work(struct work_stru
 	struct drm_atomic_state *state = container_of(work,
 						      struct drm_atomic_state,
 						      commit_work);
+	struct drm_device *dev = state->dev;
+
+	mutex_lock(&dev->master_mutex);
 	commit_tail(state);
+	mutex_unlock(&dev->master_mutex);
 }
 
 /**