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Subject: Re: [PATCH] mm,page_alloc: PF_WQ_WORKER threads must sleep at
 should_reclaim_retry().
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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Message-ID: <d11c3aa2-0f14-d882-59c5-6634dc56eed1@i-love.sakura.ne.jp>
Date: Fri, 3 Aug 2018 07:05:54 +0900
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To: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>, Roman Gushchin <guro@fb.com>, Johannes Weiner <hannes@cmpxchg.org>, Vladimir Davydov <vdavydov.dev@gmail.com>, David Rientjes <rientjes@google.com>, Andrew Morton <akpm@linux-foundation.org>, Linus Torvalds <torvalds@linux-foundation.org>, linux-mm <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>

On 2018/07/31 14:09, Michal Hocko wrote:
> On Tue 31-07-18 06:01:48, Tetsuo Handa wrote:
>> On 2018/07/31 4:10, Michal Hocko wrote:
>>> Since should_reclaim_retry() should be a natural reschedule point,
>>> let's do the short sleep for PF_WQ_WORKER threads unconditionally in
>>> order to guarantee that other pending work items are started. This will
>>> workaround this problem and it is less fragile than hunting down when
>>> the sleep is missed. E.g. we used to have a sleeping point in the oom
>>> path but this has been removed recently because it caused other issues.
>>> Having a single sleeping point is more robust.
>>
>> linux.git has not removed the sleeping point in the OOM path yet. Since removing the
>> sleeping point in the OOM path can mitigate CVE-2016-10723, please do so immediately.
> 
> is this an {Acked,Reviewed,Tested}-by?
> 
> I will send the patch to Andrew if the patch is ok. 
> 
>> (And that change will conflict with Roman's cgroup aware OOM killer patchset. But it
>> should be easy to rebase.)
> 
> That is still a WIP so I would lose sleep over it.
> 

Now that Roman's cgroup aware OOM killer patchset will be dropped from linux-next.git ,
linux-next.git will get the sleeping point removed. Please send this patch to linux-next.git .