To: miaox@cn.fujitsu.com
Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] time: add an offline-cpu check in add_timer_on()
From: Andi Kleen <andi@firstfloor.org>
References: <47625B94.50105@cn.fujitsu.com>
Date: Fri, 14 Dec 2007 11:56:44 +0100
In-Reply-To: <47625B94.50105@cn.fujitsu.com> (Miao Xie's message of "Fri\, 14 Dec 2007 18\:31\:48 +0800")
Message-ID: <p73lk7xfssz.fsf@bingen.suse.de>
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Miao Xie <miaox@cn.fujitsu.com> writes:

> Hi everyone,
>   I think we need a check in the function add_timer_on() to avoid adding a
> timer into the timer list of an offline cpu.
>
> This patch fixes this problem in add_timer_on().

No it doesn't -- it will just crash if a caller does that. If it's a real 
problem then you either need to fix the callers or change add_timer_on()
to transparently put it onto another CPU.

I don't think it's a real problem though because CPU offlining does
a stop machine and that should take care of most such races.

-Andi
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