From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) by kanga.kvack.org (Postfix) with ESMTP id 9F8778E00FB for ; Sun, 27 Jan 2019 11:58:35 -0500 (EST) Received: by mail-pf1-f198.google.com with SMTP id t2so12120400pfj.15 for ; Sun, 27 Jan 2019 08:58:35 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id y5si29696720pgk.49.2019.01.27.08.58.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 27 Jan 2019 08:58:34 -0800 (PST) Date: Sun, 27 Jan 2019 17:58:28 +0100 From: Michal Hocko Subject: Re: [PATCH v3] oom, oom_reaper: do not enqueue same task twice Message-ID: <20190127165828.GC18811@dhcp22.suse.cz> References: <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> <20190127083724.GA18811@dhcp22.suse.cz> <20190127114021.GB18811@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: 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 On Sun 27-01-19 23:57:38, Tetsuo Handa wrote: [...] > >From 9c9e935fc038342c48461aabca666f1b544e32b1 Mon Sep 17 00:00:00 2001 > From: Tetsuo Handa > Date: Sun, 27 Jan 2019 23:51:37 +0900 > Subject: [PATCH v3] 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. > > Signed-off-by: Tetsuo Handa > Reported-by: Arkadiusz Miśkiewicz > Tested-by: Arkadiusz Miśkiewicz > Fixes: af8e15cc85a25315 ("oom, oom_reaper: do not enqueue task if it is on the oom_reaper_list head") Acked-by: Michal Hocko > --- > include/linux/sched/coredump.h | 1 + > mm/oom_kill.c | 4 ++-- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h > index ec912d0..ecdc654 100644 > --- a/include/linux/sched/coredump.h > +++ b/include/linux/sched/coredump.h > @@ -71,6 +71,7 @@ static inline int get_dumpable(struct mm_struct *mm) > #define MMF_HUGE_ZERO_PAGE 23 /* mm has ever used the global huge zero page */ > #define MMF_DISABLE_THP 24 /* disable THP for all VMAs */ > #define MMF_OOM_VICTIM 25 /* mm is the oom victim */ > +#define MMF_OOM_REAP_QUEUED 26 /* mm was queued for oom_reaper */ > #define MMF_DISABLE_THP_MASK (1 << MMF_DISABLE_THP) > > #define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\ > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index f0e8cd9..059e617 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -647,8 +647,8 @@ static int oom_reaper(void *unused) > > static void wake_oom_reaper(struct task_struct *tsk) > { > - /* tsk is already queued? */ > - if (tsk == oom_reaper_list || tsk->oom_reaper_list) > + /* mm is already queued? */ > + if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags)) > return; > > get_task_struct(tsk); > -- > 1.8.3.1 -- Michal Hocko SUSE Labs