1 files changed, 3 insertions, 1 deletions

diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 267a86c74e2e..2040e6c4f172 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -246,9 +246,11 @@ struct ttm_buffer_object {
 
         atomic_t reserved;
 
-
         /**
          * Members protected by the bo::lock
+         * In addition, setting sync_obj to anything else
+         * than NULL requires bo::reserved to be held. This allows for
+         * checking NULL while reserved but not holding bo::lock.
          */
 
         void *sync_obj_arg;