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Subject: Re: [PATCH] mm,page_alloc: PF_WQ_WORKER threads must sleep at
 should_reclaim_retry().
References: <ca3da8b8-1bb5-c302-b190-fa6cebab58ca@I-love.SAKURA.ne.jp>
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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Message-ID: <6f433d59-4a56-b698-e119-682bb8bf6713@i-love.sakura.ne.jp>
Date: Tue, 31 Jul 2018 06:01:48 +0900
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To: Michal Hocko <mhocko@kernel.org>, Tejun Heo <tj@kernel.org>
Cc: 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 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.
(And that change will conflict with Roman's cgroup aware OOM killer patchset. But it
should be easy to rebase.)