From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f71.google.com (mail-lf0-f71.google.com [209.85.215.71]) by kanga.kvack.org (Postfix) with ESMTP id 047EC6B0262 for ; Fri, 3 Jun 2016 05:17:05 -0400 (EDT) Received: by mail-lf0-f71.google.com with SMTP id 132so34911410lfz.3 for ; Fri, 03 Jun 2016 02:17:04 -0700 (PDT) Received: from mail-wm0-f68.google.com (mail-wm0-f68.google.com. [74.125.82.68]) by mx.google.com with ESMTPS id ts7si6325457wjb.215.2016.06.03.02.16.54 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 03 Jun 2016 02:16:54 -0700 (PDT) Received: by mail-wm0-f68.google.com with SMTP id a20so10497954wma.3 for ; Fri, 03 Jun 2016 02:16:54 -0700 (PDT) From: Michal Hocko Subject: [PATCH 06/10] mm, oom: kill all tasks sharing the mm Date: Fri, 3 Jun 2016 11:16:40 +0200 Message-Id: <1464945404-30157-7-git-send-email-mhocko@kernel.org> In-Reply-To: <1464945404-30157-1-git-send-email-mhocko@kernel.org> References: <1464945404-30157-1-git-send-email-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org Cc: Tetsuo Handa , David Rientjes , Oleg Nesterov , Vladimir Davydov , Andrew Morton , LKML , Michal Hocko From: Michal Hocko Currently oom_kill_process skips both the oom reaper and SIG_KILL if a process sharing the same mm is unkillable via OOM_ADJUST_MIN. After "mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj" all such processes are sharing the same value so we shouldn't see such a task at all (oom_badness would rule them out). We can still encounter oom disabled vforked task which has to be killed as well if we want to have other tasks sharing the mm reapable because it can access the memory before doing exec. Killing such a task should be acceptable because it is highly unlikely it has done anything useful because it cannot modify any memory before it calls exec. An alternative would be to keep the task alive and skip the oom reaper and risk all the weird corner cases where the OOM killer cannot make forward progress because the oom victim hung somewhere on the way to exit. There is a potential race where we kill the oom disabled task which is highly unlikely but possible. It would happen if __set_oom_adj raced with select_bad_process and then it is OK to consider the old value or with fork when it should be acceptable as well. Let's add a little note to the log so that people would tell us that this really happens in the real life and it matters. Signed-off-by: Michal Hocko --- mm/oom_kill.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 2c604a9a8305..22affacaf38b 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -847,8 +847,7 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p, continue; if (same_thread_group(p, victim)) continue; - if (unlikely(p->flags & PF_KTHREAD) || is_global_init(p) || - p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) { + if (unlikely(p->flags & PF_KTHREAD) || is_global_init(p)) { /* * We cannot use oom_reaper for the mm shared by this * process because it wouldn't get killed and so the @@ -857,6 +856,11 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *p, can_oom_reap = false; continue; } + if (p->signal->oom_score_adj == OOM_ADJUST_MIN) + pr_warn("%s pid=%d shares mm with oom disabled %s pid=%d. Seems like misconfiguration, killing anyway!" + " Report at linux-mm@kvack.org\n", + victim->comm, task_pid_nr(victim), + p->comm, task_pid_nr(p)); do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true); } rcu_read_unlock(); -- 2.8.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org