Message-Id: <4B1638FE0200007800022FC2@vpn.id2.novell.com>
Date: Wed, 02 Dec 2009 08:53:02 +0000
From: "Jan Beulich" <JBeulich@novell.com>
To: "Hidetoshi Seto" <seto.hidetoshi@jp.fujitsu.com>
Cc: <mingo@elte.hu>, <stable@kernel.org>, <tglx@linutronix.de>,
       <linux-kernel@vger.kernel.org>, <hpa@zytor.com>
Subject: Re: [PATCH] x86/mce: timer must be setup unconditionally
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 <4B1629A0.60403@jp.fujitsu.com>
In-Reply-To: <4B1629A0.60403@jp.fujitsu.com>
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>>> Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> 02.12.09 09:47 >>>
>Jan Beulich wrote:
>> mce_timer must be passed to setup_timer() in all cases, no matter
>> whether it is going to be actually used. Otherwise, when the CPU gets
>> brought down, its call to del_timer_sync() will never return, as the
>> timer won't have a base associated, and hence lock_timer_base() will
>> loop infinitely.
>
>No, what we need to fix is hotplug callbacks.
>So correct fix should be like "del/add timer conditionally when hotplug."

Why? This makes the logic just more complicated (you'd need to track
whether the timer was ever setup or added), and I can't see any
non-tolerable side effect of calling setup_timer() without ever adding
the timer anywhere.

Jan

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