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[195.135.220.15]) by mx.google.com with ESMTPS id f47si2926246edf.53.2019.01.28.10.42.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Jan 2019 10:42:33 -0800 (PST) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org 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) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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