From: Michal Hocko <mhocko@kernel.org>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Rientjes <rientjes@google.com>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Oleg Nesterov <oleg@redhat.com>, Hugh Dickins <hughd@google.com>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm, oom: allow oom reaper to race with exit_mmap
Date: Thu, 27 Jul 2017 08:32:04 +0200 [thread overview]
Message-ID: <20170727063202.GA20970@dhcp22.suse.cz> (raw)
In-Reply-To: <20170726163928.GB29716@redhat.com>
On Wed 26-07-17 18:39:28, Andrea Arcangeli wrote:
> On Wed, Jul 26, 2017 at 07:45:33AM +0200, Michal Hocko wrote:
> > Yes, exit_aio is the only blocking call I know of currently. But I would
> > like this to be as robust as possible and so I do not want to rely on
> > the current implementation. This can change in future and I can
> > guarantee that nobody will think about the oom path when adding
> > something to the final __mmput path.
>
> I think ksm_exit may block too waiting for allocations, the generic
> idea is those calls before exit_mmap can cause a problem yes.
I thought that ksm used __GFP_NORETRY but haven't checked too deeply.
Anyway I guess we agree that enabling oom_reaper to race with the final
__mmput is desirable?
[...]
> > This will work more or less the same to what we have currently.
> >
> > [victim] [oom reaper] [oom killer]
> > do_exit __oom_reap_task_mm
> > mmput
> > __mmput
> > mmget_not_zero
> > test_and_set_bit(MMF_OOM_SKIP)
> > oom_evaluate_task
> > # select next victim
> > # reap the mm
> > unmap_vmas
> >
> > so we can select a next victim while the current one is still not
> > completely torn down.
>
> How does oom_evaluate_task possibly run at the same time of
> test_and_set_bit in __oom_reap_task_mm considering both are running
> under the oom_lock?
You are absolutely right. This race is impossible. It was just me
assuming we are going to get rid of the oom_lock because I have that
idea in the back of my head and I would really like to get rid of
it. Global locks are nasty and I would prefer dropping it if we can.
[...]
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2017-07-27 6:32 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-24 7:23 [PATCH] mm, oom: allow oom reaper to race with exit_mmap Michal Hocko
2017-07-24 14:00 ` Kirill A. Shutemov
2017-07-24 14:15 ` Michal Hocko
2017-07-24 14:51 ` Kirill A. Shutemov
2017-07-24 16:11 ` Michal Hocko
2017-07-25 14:17 ` Kirill A. Shutemov
2017-07-25 14:26 ` Michal Hocko
2017-07-25 15:07 ` Kirill A. Shutemov
2017-07-25 15:15 ` Michal Hocko
2017-07-25 14:26 ` Michal Hocko
2017-07-25 15:17 ` Kirill A. Shutemov
2017-07-25 15:23 ` Michal Hocko
2017-07-25 15:31 ` Kirill A. Shutemov
2017-07-25 16:04 ` Michal Hocko
2017-07-25 19:19 ` Andrea Arcangeli
2017-07-26 5:45 ` Michal Hocko
2017-07-26 16:29 ` Andrea Arcangeli
2017-07-26 16:43 ` Andrea Arcangeli
2017-07-27 6:50 ` Michal Hocko
2017-07-27 14:55 ` Andrea Arcangeli
2017-07-28 6:23 ` Michal Hocko
2017-07-28 1:58 ` [PATCH 1/1] mm: oom: let oom_reap_task and exit_mmap to run kbuild test robot
2017-08-15 0:20 ` [PATCH] mm, oom: allow oom reaper to race with exit_mmap David Rientjes
2017-07-24 15:27 ` Michal Hocko
2017-07-24 16:42 ` kbuild test robot
2017-07-24 18:12 ` Michal Hocko
2017-07-25 15:26 ` Andrea Arcangeli
2017-07-25 15:45 ` Michal Hocko
2017-07-25 18:26 ` Andrea Arcangeli
2017-07-26 5:45 ` Michal Hocko
2017-07-26 16:39 ` Andrea Arcangeli
2017-07-27 6:32 ` Michal Hocko [this message]
2017-08-10 8:16 Michal Hocko
2017-08-10 18:05 ` Andrea Arcangeli
2017-08-10 18:51 ` Michal Hocko
2017-08-10 20:36 ` Michal Hocko
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