From: Michal Hocko <mhocko@kernel.org>
To: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: linux-mm@kvack.org, rientjes@google.com, oleg@redhat.com,
vdavydov@parallels.com, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 07/10] mm, oom: fortify task_will_free_mem
Date: Mon, 13 Jun 2016 13:27:46 +0200 [thread overview]
Message-ID: <20160613112746.GD6518@dhcp22.suse.cz> (raw)
In-Reply-To: <201606111710.IGF51027.OJLSOQtHVOFFFM@I-love.SAKURA.ne.jp>
On Sat 11-06-16 17:10:03, Tetsuo Handa wrote:
> Michal Hocko wrote:
> > > Also, I think setting TIF_MEMDIE on p when find_lock_task_mm(p) != p is
> > > wrong. While oom_reap_task() will anyway clear TIF_MEMDIE even if we set
> > > TIF_MEMDIE on p when p->mm == NULL, it is not true for CONFIG_MMU=n case.
> >
> > Yes this would be racy for !CONFIG_MMU but does it actually matter?
>
> I don't know because I've never used CONFIG_MMU=n kernels. But I think it
> actually matters. You fixed this race by commit 83363b917a2982dd ("oom:
> make sure that TIF_MEMDIE is set under task_lock").
Yes and that commit was trying to address a highly theoretical issue
reported by you. Let me quote:
:oom_kill_process is currently prone to a race condition when the OOM
:victim is already exiting and TIF_MEMDIE is set after the task releases
:its address space. This might theoretically lead to OOM livelock if the
:OOM victim blocks on an allocation later during exiting because it
:wouldn't kill any other process and the exiting one won't be able to exit.
:The situation is highly unlikely because the OOM victim is expected to
:release some memory which should help to sort out OOM situation.
Even if such a race is possible it wouldn't be with the oom
reaper. Regarding CONFIG_MMU=n I am even less sure it is possible and
I would rather focus on CONFIG_MMU=y where we know that problems exist
rather than speculating about something as special as nommu which even
might not care at all.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-06-13 11:27 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-09 11:52 [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-09 11:52 ` [PATCH 01/10] proc, oom: drop bogus task_lock and mm check Michal Hocko
2016-06-09 11:52 ` [PATCH 02/10] proc, oom: drop bogus sighand lock Michal Hocko
2016-06-09 11:52 ` [PATCH 03/10] proc, oom_adj: extract oom_score_adj setting into a helper Michal Hocko
2016-06-09 11:52 ` [PATCH 04/10] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko
2016-06-15 15:03 ` Oleg Nesterov
2016-06-09 11:52 ` [PATCH 05/10] mm, oom: skip vforked tasks from being selected Michal Hocko
2016-06-15 14:51 ` Oleg Nesterov
2016-06-16 6:24 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 06/10] mm, oom: kill all tasks sharing the mm Michal Hocko
2016-06-09 11:52 ` [PATCH 07/10] mm, oom: fortify task_will_free_mem Michal Hocko
2016-06-09 13:18 ` Tetsuo Handa
2016-06-09 14:20 ` Michal Hocko
2016-06-11 8:10 ` Tetsuo Handa
2016-06-13 11:27 ` Michal Hocko [this message]
2016-06-16 12:54 ` Tetsuo Handa
2016-06-16 14:29 ` Michal Hocko
2016-06-16 15:40 ` Tetsuo Handa
2016-06-16 15:53 ` Michal Hocko
2016-06-17 11:38 ` Tetsuo Handa
2016-06-17 12:26 ` Michal Hocko
2016-06-17 13:12 ` Tetsuo Handa
2016-06-17 13:29 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 08/10] mm, oom: task_will_free_mem should skip oom_reaped tasks Michal Hocko
2016-06-17 11:35 ` Tetsuo Handa
2016-06-17 12:56 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 09/10] mm, oom_reaper: do not attempt to reap a task more than twice Michal Hocko
2016-06-15 14:48 ` Oleg Nesterov
2016-06-16 6:28 ` Michal Hocko
2016-06-09 11:52 ` [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init Michal Hocko
2016-06-09 15:15 ` Tetsuo Handa
2016-06-09 15:41 ` Michal Hocko
2016-06-16 13:15 ` Tetsuo Handa
2016-06-16 13:36 ` Tetsuo Handa
2016-06-15 14:37 ` Oleg Nesterov
2016-06-16 6:31 ` Michal Hocko
2016-06-13 11:23 ` [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-13 14:13 ` Michal Hocko
2016-06-14 20:17 ` Oleg Nesterov
2016-06-14 20:44 ` Oleg Nesterov
2016-06-16 6:33 ` Michal Hocko
2016-06-15 15:09 ` Oleg Nesterov
2016-06-16 6:34 ` Michal Hocko
-- strict thread matches above, loose matches on Subject: below --
2016-06-20 12:43 [PATCH 0/10 -v5] " Michal Hocko
2016-06-20 12:43 ` [PATCH 07/10] mm, oom: fortify task_will_free_mem Michal Hocko
2016-06-03 9:16 [PATCH 0/10 -v3] Handle oom bypass more gracefully Michal Hocko
2016-06-03 9:16 ` [PATCH 07/10] mm, oom: fortify task_will_free_mem Michal Hocko
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