diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 435f08d..8610370 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -51,6 +51,7 @@
 #define do_swap_account		(0)
 #endif
 
+static DEFINE_MUTEX(memcg_tasklist);	/* can be hold under cgroup_mutex */
 
 /*
  * Statistics for memory cgroup.
@@ -827,7 +828,9 @@
 
 		if (!nr_retries--) {
 			if (oom) {
+				mutex_lock(&memcg_tasklist);
 				mem_cgroup_out_of_memory(mem_over_limit, gfp_mask);
+				mutex_unlock(&memcg_tasklist);
 				mem_over_limit->last_oom_jiffies = jiffies;
 			}
 			goto nomem;
@@ -2211,10 +2214,12 @@
 				struct cgroup *old_cont,
 				struct task_struct *p)
 {
+	mutex_lock(&memcg_tasklist);
 	/*
 	 * FIXME: It's better to move charges of this process from old
 	 * memcg to new memcg. But it's just on TODO-List now.
 	 */
+	mutex_unlock(&memcg_tasklist);
 }
 
 struct cgroup_subsys mem_cgroup_subsys = {