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Date: Mon, 18 Sep 2017 20:38:22 -0700
From: Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH] mm, memory_hotplug: do not back off draining pcp free
 pages from kworker context
Message-ID: <20170919033821.GR378890@devbig577.frc2.facebook.com>
References: <20170828093341.26341-1-mhocko@kernel.org>
 <20170828153359.f9b252f99647eebd339a3a89@linux-foundation.org>
 <6e138348-aa28-8660-d902-96efafe1dcb2@I-love.SAKURA.ne.jp>
 <20170829112823.GA12413@dhcp22.suse.cz>
 <20170831053342.fo7x4hnhicxikme4@dhcp22.suse.cz>
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To: Michal Hocko <mhocko@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mgorman@suse.de>, linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>

Hello, Sorry about the delay.

On Thu, Aug 31, 2017 at 07:33:42AM +0200, Michal Hocko wrote:
> > > Michal, are you sure that this patch does not cause deadlock?
> > > 
> > > As shown in "[PATCH] mm: Use WQ_HIGHPRI for mm_percpu_wq." thread, currently work
> > > items on mm_percpu_wq seem to be blocked by other work items not on mm_percpu_wq.

IIUC that wasn't a deadlock but more a legitimate starvation from too
many tasks trying to reclaim directly.

> > But we have a rescuer so we should make a forward progress eventually.
> > Or am I missing something. Tejun, could you have a look please?
> 
> ping... I would really appreaciate if you could double check my thinking
> Tejun. This is a tricky area and I would like to prevent further subtle
> issues here.

So, this shouldn't be an issue.  This may get affected by direct
reclaim frenzy but it's only a small piece of the whole symptom and we
gotta fix that at the source.

Thanks.

-- 
tejun

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