oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head

Michal Hocko · torvalds · commit af8e15cc85a2 · 2016-04-01T17:03:37.000-05:00
Commit bb29902 ("oom, oom_reaper: protect oom_reaper_list using simpler way") has simplified the check for tasks already enqueued for the oom reaper by checking tsk->oom_reaper_list != NULL. This check is not sufficient because the tsk might be the head of the queue without any other tasks queued and then we would simply lockup looping on the same task. Fix the condition by checking for the head as well. Fixes: bb29902 ("oom, oom_reaper: protect oom_reaper_list using simpler way") Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
@@ -547,7 +547,11 @@ static int oom_reaper(void *unused)
 
 static void wake_oom_reaper(struct task_struct *tsk)
 {
-	if (!oom_reaper_th || tsk->oom_reaper_list)
+	if (!oom_reaper_th)
+		return;
+
+	/* tsk is already queued? */
+	if (tsk == oom_reaper_list || tsk->oom_reaper_list)
 		return;
 
 	get_task_struct(tsk);
