1 files changed, 3 insertions, 0 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 925b431f3f03..58c69c94402a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2896,6 +2896,7 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
          * ordering is imposed by list_lru_node->lock taken by
          * memcg_drain_all_list_lrus().
          */
+        rcu_read_lock(); /* can be called from css_free w/o cgroup_mutex */
         css_for_each_descendant_pre(css, &memcg->css) {
                 child = mem_cgroup_from_css(css);
                 BUG_ON(child->kmemcg_id != kmemcg_id);
@@ -2903,6 +2904,8 @@ static void memcg_offline_kmem(struct mem_cgroup *memcg)
                 if (!memcg->use_hierarchy)
                         break;
         }
+        rcu_read_unlock();
+
         memcg_drain_all_list_lrus(kmemcg_id, parent->kmemcg_id);
 
         memcg_free_cache_id(kmemcg_id);