linux-kernel - Re: [PATCH 1/2] proc/insterrupts: make it cpu hotplug safe

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Message-ID: <4E2FA846.6000305@jp.fujitsu.com>
Date:	Wed, 27 Jul 2011 14:55:18 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	yong.zhang0@...il.com
CC:	linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, kobayashi.kk@...s.nec.co.jp,
	heiko.carstens@...ibm.com
Subject: Re: [PATCH 1/2] proc/insterrupts: make it cpu hotplug safe

(2011/07/27 14:47), Yong Zhang wrote:
> 2011/7/27 KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>:
>> (2011/07/27 13:56), Yong Zhang wrote:
>>> KOSAKI Motonhiro noticed that the reader of /proc/interrupts
>>> could be preempted by cpu hotplug, thus the reader can get
>>> broken result due to show_interrupts() iterate every online
>>> cpu without any protection.
>>>
>>> Signed-off-by: Yong Zhang <yong.zhang0@...il.com>
>>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>>> Cc: Keika Kobayashi <kobayashi.kk@...s.nec.co.jp>
>>> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>>> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
>>
>> Looks good. but I have a question. On last thread, kobayashi-san
>> suggested to use for_each_possible_cpu() and you wrote "+1".
> 
> Yeah, for_each_possible_cpu() will make code more cleaner.
> so I give it my support.
> 
>>
>>>> At that time, I suggested to change
>>>> from for_each_online_cpu() to for_each_possible_cpu(),
>>>> in /proc/interrupts.
>>> +1
>>> Thus we could also avoid the issue pointed by KOSAKI Motonhiro.
>>
>> Why do you decide to use another way?
> 
> But, as kobayashi-san has also said:
> In conclusion, we decided to remain /proc/interrupts.
> because it had been the way for a long time.
> 
> So I don't want to raise an argument again :)

Fair enough. thanks.

	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>



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