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

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Message-ID: <20140729075637.GA19379@twins.programming.kicks-ass.net>
Date:	Tue, 29 Jul 2014 09:56:37 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Christoph Lameter <cl@...two.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>, akpm@...ux-foundation.org,
	Gilad Ben-Yossef <gilad@...yossef.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tejun Heo <tj@...nel.org>, 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
Subject: Re: vmstat: On demand vmstat workers V8

On Mon, Jul 28, 2014 at 01:55:17PM -0500, Christoph Lameter wrote:
> On Fri, 25 Jul 2014, Sasha Levin wrote:
> 
> > This patch doesn't interact well with my fuzzing setup. I'm seeing
> > the following:
> >
> > [  490.446927] BUG: using __this_cpu_read() in preemptible [00000000] code: kworker/16:1/7368
> > [  490.447909] caller is __this_cpu_preempt_check+0x13/0x20
> 
> __this_cpu_read() from vmstat_update is only called from a kworker that
> is bound to a single cpu. A false positive?

kworkers are never guaranteed to be so, its a 'feature' :/

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