linux-kernel - Re: [PATCH UPDATED#3 04/16] x86: setup_local_APIC() must always be called with preemption disabled

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Message-ID: <4D020A53.8020500@kernel.org>
Date:	Fri, 10 Dec 2010 12:09:07 +0100
From:	Tejun Heo <tj@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	linux-kernel@...r.kernel.org, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, eric.dumazet@...il.com, yinghai@...nel.org,
	brgerst@...il.com, gorcunov@...il.com, penberg@...nel.org
Subject: Re: [PATCH UPDATED#3 04/16] x86: setup_local_APIC() must always be
 called with preemption disabled

On 12/09/2010 10:56 PM, Thomas Gleixner wrote:
> On Thu, 9 Dec 2010, Tejun Heo wrote:
> 
>> setup_local_APIC() is used to setup local APIC early during CPU
>> initialization and already assumes that preemption is disabled on
>> entry.  However, The function unnecessarily disables and enables
>> preemption and uses smp_processor_id() multiple times in and out of
>> the nested preemption disabled section.  This gives the wrong
>> impression that the function might be able to handle being called with
>> preemption enabled and/or migrated to another processor in the middle.
>>
>> Make it clear that the function is always called with preemption
>> disabled, drop the confusing preemption disable block and call
>> smp_processor_id() once at the beginning of the function.
> 
> AFAICT, this one is completely unrelated to that NUMA cleanup, right ?
> 
> So this can be applied independent and should never have been part of
> that NUMA series in the first place.

Originally, it was a trivial prep patch.  Anyways, I'll push it
to the top of the series so that it can be taken separately.

Thanks.

-- 
tejun
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