linux-kernel - Re: [PATCH] mm,vmscan: Use accurate values for zone

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Message-ID: <20151102192053.GC9553@mtj.duckdns.org>
Date:	Mon, 2 Nov 2015 14:20:53 -0500
From:	Tejun Heo <htejun@...il.com>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Christoph Lameter <cl@...ux.com>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org,
	David Rientjes <rientjes@...gle.com>, oleg@...hat.com,
	kwalker@...hat.com, akpm@...ux-foundation.org, hannes@...xchg.org,
	vdavydov@...allels.com, skozina@...hat.com, mgorman@...e.de,
	riel@...hat.com
Subject: Re: [PATCH] mm,vmscan: Use accurate values for zone_reclaimable()
 checks

On Mon, Nov 02, 2015 at 04:01:37PM +0100, Michal Hocko wrote:
...
> which is perfectly suited for the stable backport, OOM sysrq resp. any
> sysrq which runs from the WQ context should be as robust as possible and
> shouldn't rely on all the code running from WQ context to issue a sleep
> to get unstuck. So I definitely support something like this patch.

Well, sysrq wouldn't run successfully either on a cpu which is busy
looping with preemption off.  I don't think this calls for a new flag
to modify workqueue behavior especially given that missing such flag
would lead to the same kind of lockup.  It's a shitty solution.  If
the possibility of sysrq getting stuck behind concurrency management
is an issue, queueing them on an unbound or highpri workqueue should
be good enough.

Thanks.

-- 
tejun
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