From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753523AbcC2Mbi (ORCPT ); Tue, 29 Mar 2016 08:31:38 -0400 Received: from mail-wm0-f45.google.com ([74.125.82.45]:34668 "EHLO mail-wm0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752676AbcC2Mbe (ORCPT ); Tue, 29 Mar 2016 08:31:34 -0400 From: Michal Hocko To: Andrew Morton Cc: Tetsuo Handa , , LKML , Michal Hocko Subject: [PATCH] oom, oom_reaper: Do not enqueue task if it is on the oom_reaper_list head Date: Tue, 29 Mar 2016 14:31:26 +0200 Message-Id: <1459254686-29457-1-git-send-email-mhocko@kernel.org> X-Mailer: git-send-email 2.7.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michal Hocko 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 --- Hi, I have just noticed this after I started consolidating other oom_reaper related changes I have here locally. I should have caught this during the review already and I really feel ashamed I haven't because this is really a trivial bug that should be obvious see... mm/oom_kill.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index b34d279a7ee6..86349586eacb 100644 --- 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); -- 2.7.0