linux-kernel - Re: [patch v3] mm, oom: fix unnecessary killing of additional processes

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Message-ID: <9ab77cc7-2167-0659-a2ad-9cec3b9440e9@i-love.sakura.ne.jp>
Date:   Fri, 20 Jul 2018 18:57:44 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        kbuild test robot <fengguang.wu@...el.com>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [patch v3] mm, oom: fix unnecessary killing of additional
 processes

On 2018/07/20 17:41, David Rientjes wrote:
> Absent oom_lock serialization, this is exactly working as intended.  You 
> could argue that once the thread has reached exit_mmap() and begins oom 
> reaping that it should be allowed to finish before the oom reaper declares 
> MMF_OOM_SKIP.  That could certainly be helpful, I simply haven't 
> encountered a usecase where it were needed.  Or, we could restart the oom 
> expiration when MMF_UNSTABLE is set and deem that progress is being made 
> so it give it some extra time.  In practice, again, we haven't seen this 
> needed.  But either of those are very easy to add in as well.  Which would 
> you prefer?

I don't think we need to introduce user-visible knob interface (even if it is in
debugfs), for I think that my approach can solve your problem. Please try OOM lockup
(CVE-2016-10723) mitigation patch ( https://marc.info/?l=linux-mm&m=153112243424285&w=4 )
and my cleanup patch ( [PATCH 1/2] at https://marc.info/?l=linux-mm&m=153119509215026&w=4 )
on top of linux.git . And please reply how was the result, for I'm currently asking
Roman whether we can apply these patches before applying the cgroup-aware OOM killer.