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, 3 Mar 2009 19:44:06 +0900 (JST)
From:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
To:	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
Cc:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	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

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!
                                                     isn't...
Sorry.
-Kame


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