linux-kernel - Re: [RFC][PATCH] remove rq->lock from cpuacct cgroup (Was Re: [PATCH] cpuacct: add a branch prediction

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Date:	Tue, 03 Mar 2009 12:54:48 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	paulmck@...ux.vnet.ibm.com, Bharata B Rao <bharata.rao@...il.com>,
	Li Zefan <lizf@...fujitsu.com>, Ingo Molnar <mingo@...e.hu>,
	Paul Menage <menage@...gle.com>,
	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] remove rq->lock from cpuacct cgroup (Was Re:
 [PATCH] cpuacct: add a branch prediction

On Tue, 2009-03-03 at 19:42 +0900, KAMEZAWA Hiroyuki wrote:
> Peter Zijlstra  wrote:
> > On Tue, 2009-03-03 at 18:04 +0900, KAMEZAWA Hiroyuki wrote:
> >> Peter Zijlstra wrote:
> >> > On Tue, 2009-03-03 at 08:42 +0900, KAMEZAWA Hiroyuki wrote:
> >> >
> >> >> > Furthermore, if you want something like schedule_work_on() for each
> >> >> cpu,
> >> >> > there's schedule_on_each_cpu().
> >> >> >
> >> >> It can't pass arguments...Maybe I should use rq->lock here to reset
> >> >> other cpu's value.
> >> >
> >> > Why bother with serializing the reset code at all?
> >> >
> >>   I don't think reset v.s. read is problem but reset v.s. increment
> >>   (read-modify-write) can't be ?
> >
> > Sure, can be, do we care?
> >
> If small/easy code allows us to declare "there are any racy case!
> and you don't have to check whether you successfully reseted",
> it's worth to do I think.

smp_call_function() it is...

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