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

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Date:	Thu, 9 Dec 2010 22:56:13 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Tejun Heo <tj@...nel.org>
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 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.

Thanks,

	tglx
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