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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,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 3FDDEC282C8 for ; Mon, 28 Jan 2019 18:42:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0AD5B21741 for ; Mon, 28 Jan 2019 18:42:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548700956; bh=taewOz7zxs0tcf8S7TTKEYdIgOSkzra6lP+wnzdDF58=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=17Ww/g6txH7mNO5BsUsIe2kS3szDS11vIc3oWg5bqnpWfJfW2oWtFhmmKWjYhmQXh /gWogmvhtCVJq6A9UB+Y99Sl5Wjrc67oMrpdxDeXcz9sJvjijlVwXnTLVUI2MZh+Ol gZpjUvFExqevCjJoMoPHh1UrAsuMHHOfC3CDHb7A= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727761AbfA1Sme (ORCPT ); Mon, 28 Jan 2019 13:42:34 -0500 Received: from mx2.suse.de ([195.135.220.15]:55996 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726667AbfA1Sme (ORCPT ); Mon, 28 Jan 2019 13:42:34 -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 9FB8EB017; Mon, 28 Jan 2019 18:42:32 +0000 (UTC) Date: Mon, 28 Jan 2019 19:42:31 +0100 From: Michal Hocko To: Andrew Morton Cc: Tetsuo Handa , Arkadiusz =?utf-8?Q?Mi=C5=9Bkiewicz?= , 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 v3] oom, oom_reaper: do not enqueue same task twice Message-ID: <20190128184231.GS18811@dhcp22.suse.cz> References: <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> <20190127083724.GA18811@dhcp22.suse.cz> <20190127114021.GB18811@dhcp22.suse.cz> <20190128101513.f35752d6210f0781d0de8d17@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190128101513.f35752d6210f0781d0de8d17@linux-foundation.org> 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 Mon 28-01-19 10:15:13, Andrew Morton wrote: > On Sun, 27 Jan 2019 23:57:38 +0900 Tetsuo Handa wrote: > > > 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. > > > > Do we think this is serious enough to warrant a -stable backport? Yes, I would go with stable backport. -- Michal Hocko SUSE Labs