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

Commit bb29902a7515 ("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: bb29902a7515 ("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
index b34d279a7ee6c43cb5e85d7e35956159c656cc47..86349586eacbac5022affca24ebaa2b57d19aa15 100644 (file)
--- 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);