Fix T79038: Blender freezes on vertex paint on linked mesh data

This change promotes the work-a-round to the current solution.
There are options to solve this better, but needs more design.

source/blender/draw/intern/draw_cache_impl_mesh.c

@@ -1559,8 +1559,14 @@ void DRW_mesh_batch_cache_create_requested(struct TaskGraph *task_graph,
                                      scene,
                                      ts,
                                      use_hide);
-  /* TODO(jbakker): Work-around for threading issues in 2.90. See T79533, T79038. Needs to be
-   * solved or made permanent in 2.91. Underlying issue still needs to be researched. */
+
+  /* Ensure that all requested batches have finished.
+   * Ideally we want to remove this sync, but there are cases where this doesn't work.
+   * See T79038 for example.
+   *
+   * An idea to improve this is to separate the Object mode from the edit mode draw caches. And
+   * based on the mode the correct one will be updated. Other option is to look into using
+   * drw_batch_cache_generate_requested_delayed. */
   BLI_task_graph_work_and_wait(task_graph);
 #ifdef DEBUG
   drw_mesh_batch_cache_check_available(task_graph, me);