linux-kernel - Re: vmstat: On demand vmstat workers V8

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Message-ID: <20140729151415.GF4791@htj.dyndns.org>
Date:	Tue, 29 Jul 2014 11:14:15 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Christoph Lameter <cl@...two.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	akpm@...ux-foundation.org, Gilad Ben-Yossef <gilad@...yossef.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <johnstul@...ibm.com>,
	Mike Frysinger <vapier@...too.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, hughd@...gle.com,
	viresh.kumar@...aro.org, hpa@...or.com, mingo@...nel.org,
	Lai Jiangshan <laijs@...fujitsu.com>
Subject: Re: vmstat: On demand vmstat workers V8

On Tue, Jul 29, 2014 at 10:10:11AM -0500, Christoph Lameter wrote:
> On Tue, 29 Jul 2014, Tejun Heo wrote:
> 
> > I agree this can be improved, but at least for now, please add cpu
> > down hooks.  We need them right now and they'll be helpful when later
> > separating out the correctness ones.
> 
> mm/vmstat.c already has cpu down hooks. See vmstat_cpuup_callback().

Hmmm, well, then it's something else.  Either a bug in workqueue or in
the caller.  Given the track record, the latter is more likely.
e.g. it looks kinda suspicious that the work func is cleared after
cancel_delayed_work_sync() is called.  What happens if somebody tries
to schedule it inbetween?

Thanks.

-- 
tejun
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