From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6D419C282C0 for ; Sun, 27 Jan 2019 08:37:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 362A3214C6 for ; Sun, 27 Jan 2019 08:37:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548578251; bh=l1qJ1O18UAJWbwMNUwkeNBZcDHoZC2pV/59uHdjfI3Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=EBWbK1w4cOYoSd19c289LS6NUQUHgSOuPhpfOpj0IM6KT9EbLA9yNCYCT1bk7yFJ8 hcsq9qznDxGKS7AUf4eWct7A7U/24KjgZpgnQPvihtP5Mw/FafFfIeEMLtChIIw+De sIZSqC8S6VuQq9ikg+CR7CWlV3e17gU6ypgEznlY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726661AbfA0Ih3 (ORCPT ); Sun, 27 Jan 2019 03:37:29 -0500 Received: from mx2.suse.de ([195.135.220.15]:40030 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726327AbfA0Ih2 (ORCPT ); Sun, 27 Jan 2019 03:37:28 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 31A37AE3B; Sun, 27 Jan 2019 08:37:26 +0000 (UTC) Date: Sun, 27 Jan 2019 09:37:24 +0100 From: Michal Hocko To: Tetsuo Handa Cc: Arkadiusz =?utf-8?Q?Mi=C5=9Bkiewicz?= , Andrew Morton , Tejun Heo , cgroups@vger.kernel.org, Aleksa Sarai , Jay Kamat , Roman Gushchin , Johannes Weiner , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm Subject: Re: [PATCH v2] oom, oom_reaper: do not enqueue same task twice Message-ID: <20190127083724.GA18811@dhcp22.suse.cz> References: <1cdbef13-564d-61a6-95f4-579d2cad243d@gmail.com> <20190125163731.GJ50184@devbig004.ftw2.facebook.com> <480296c4-ed7a-3265-e84a-298e42a0f1d5@I-love.SAKURA.ne.jp> <6da6ca69-5a6e-a9f6-d091-f89a8488982a@gmail.com> <72aa8863-a534-b8df-6b9e-f69cf4dd5c4d@i-love.sakura.ne.jp> <33a07810-6dbc-36be-5bb6-a279773ccf69@i-love.sakura.ne.jp> <34e97b46-0792-cc66-e0f2-d72576cdec59@i-love.sakura.ne.jp> <2b0c7d6c-c58a-da7d-6f0a-4900694ec2d3@gmail.com> <1d161137-55a5-126f-b47e-b2625bd798ca@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1d161137-55a5-126f-b47e-b2625bd798ca@i-love.sakura.ne.jp> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 26-01-19 22:10:52, Tetsuo Handa wrote: [...] > >From 9c9e935fc038342c48461aabca666f1b544e32b1 Mon Sep 17 00:00:00 2001 > From: Tetsuo Handa > Date: Sat, 26 Jan 2019 21:57:25 +0900 > Subject: [PATCH v2] oom, oom_reaper: do not enqueue same task twice > > Arkadiusz reported that enabling memcg's group oom killing causes > strange memcg statistics where there is no task in a memcg despite > the number of tasks in that memcg is not 0. It turned out that there > is a bug in wake_oom_reaper() which allows enqueuing same task twice > which makes impossible to decrease the number of tasks in that memcg > due to a refcount leak. > > This bug existed since the OOM reaper became invokable from > task_will_free_mem(current) path in out_of_memory() in Linux 4.7, > but memcg's group oom killing made it easier to trigger this bug by > calling wake_oom_reaper() on the same task from one out_of_memory() > request. > > Fix this bug using an approach used by commit 855b018325737f76 > ("oom, oom_reaper: disable oom_reaper for oom_kill_allocating_task"). > As a side effect of this patch, this patch also avoids enqueuing > multiple threads sharing memory via task_will_free_mem(current) path. Thanks for the analysis and the patch. This should work, I believe but I am not really thrilled to overload the meaning of the MMF_UNSTABLE. The flag is meant to signal accessing address space is not stable and it is not aimed to synchronize oom reaper with the oom path. Can we make use mark_oom_victim directly? I didn't get to think that through right now so I might be missing something but this should prevent repeating queueing as well. diff --git a/mm/oom_kill.c b/mm/oom_kill.c index f0e8cd9edb1a..dac4f2197e53 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -690,7 +690,7 @@ static void mark_oom_victim(struct task_struct *tsk) WARN_ON(oom_killer_disabled); /* OOM killer might race with memcg OOM */ if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE)) - return; + return false; /* oom_mm is bound to the signal struct life time. */ if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) { @@ -707,6 +707,8 @@ static void mark_oom_victim(struct task_struct *tsk) __thaw_task(tsk); atomic_inc(&oom_victims); trace_mark_victim(tsk->pid); + + return true; } /** @@ -873,7 +875,7 @@ static void __oom_kill_process(struct task_struct *victim) * reserves from the user space under its control. */ do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID); - mark_oom_victim(victim); + can_oom_reap = mark_oom_victim(victim); pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n", task_pid_nr(victim), victim->comm, K(victim->mm->total_vm), K(get_mm_counter(victim->mm, MM_ANONPAGES)), @@ -954,8 +956,8 @@ static void oom_kill_process(struct oom_control *oc, const char *message) */ task_lock(p); if (task_will_free_mem(p)) { - mark_oom_victim(p); - wake_oom_reaper(p); + if (mark_oom_victim(p) + wake_oom_reaper(p); task_unlock(p); put_task_struct(p); return; @@ -1084,8 +1086,8 @@ bool out_of_memory(struct oom_control *oc) * quickly exit and free its memory. */ if (task_will_free_mem(current)) { - mark_oom_victim(current); - wake_oom_reaper(current); + if (mark_oom_victim(current)) + wake_oom_reaper(current); return true; } -- Michal Hocko SUSE Labs