1 files changed, 9 insertions, 8 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c40e508d54e9..8ec5b0f38292 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -798,7 +798,8 @@ css_rightmost_descendant(struct cgroup_subsys_state *pos);
  * @pos: the css * to use as the loop cursor
  * @root: css whose descendants to walk
  *
- * Walk @root's descendants.  Must be called under rcu_read_lock().  A
+ * Walk @root's descendants.  @root is included in the iteration and the
+ * first node to be visited.  Must be called under rcu_read_lock().  A
  * descendant css which hasn't finished ->css_online() or already has
  * finished ->css_offline() may show up during traversal and it's each
  * subsystem's responsibility to verify that each @pos is alive.
@@ -820,13 +821,12 @@ css_rightmost_descendant(struct cgroup_subsys_state *pos);
  *
  * my_update_state(@css)
  * {
- *      Lock @css;
- *      Update @css's state;
- *      Unlock @css;
- *
  *      css_for_each_descendant_pre(@pos, @css) {
  *              Lock @pos;
- *              Verify @pos is alive and inherit state from @pos's parent;
+ *              if (@pos == @css)
+ *                      Update @css's state;
+ *              else
+ *                      Verify @pos is alive and inherit state from its parent;
  *              Unlock @pos;
  *      }
  * }
@@ -864,8 +864,9 @@ css_next_descendant_post(struct cgroup_subsys_state *pos,
  * @css: css whose descendants to walk
  *
  * Similar to css_for_each_descendant_pre() but performs post-order
- * traversal instead.  Note that the walk visibility guarantee described in
- * pre-order walk doesn't apply the same to post-order walks.
+ * traversal instead.  @root is included in the iteration and the last
+ * node to be visited.  Note that the walk visibility guarantee described
+ * in pre-order walk doesn't apply the same to post-order walks.
  */
 #define css_for_each_descendant_post(pos, css)                          \
         for ((pos) = css_next_descendant_post(NULL, (css)); (pos);      \