mm: memcontrol: zap oom_info_lock

mem_cgroup_print_oom_info is always called under oom_lock, so
oom_info_lock is redundant.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -1150,12 +1150,9 @@ static bool mem_cgroup_wait_acct_move(struct mem_cgroup *memcg)
  */
 void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 {
-	/* oom_info_lock ensures that parallel ooms do not interleave */
-	static DEFINE_MUTEX(oom_info_lock);
 	struct mem_cgroup *iter;
 	unsigned int i;
 
-	mutex_lock(&oom_info_lock);
 	rcu_read_lock();
 
 	if (p) {
@@ -1199,7 +1196,6 @@ void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
 
 		pr_cont("\n");
 	}
-	mutex_unlock(&oom_info_lock);
 }
 
 /*