linux-kernel - Re: [PATCH 0/4] hard_smp_processor

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Date:	Wed, 11 Apr 2007 15:33:51 +0900
From:	Simon Horman <horms@...ge.net.au>
To:	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	ak@...e.de, benh@...nel.crashing.org, davem@...emloft.net,
	ebiederm@...ssion.com, heiko.carstens@...ibm.com,
	ink@...assic.park.msu.ru, jdike@...toit.com, paulus@...ba.org,
	rth@...ddle.net, schwidefsky@...ibm.com, takata@...ux-m32r.org,
	tony.luck@...el.com, vgoyal@...ibm.com
Subject: Re: [PATCH 0/4] hard_smp_processor_id overhaul (v.2)

On Wed, Apr 04, 2007 at 05:51:07PM +0900, Fernando Luis Vázquez Cao wrote:
> This new version (v.2) fixes generic arch i386 up build, has (hopefully)
> clearer explanations, and does not break git bisect searches.
> ---
> With the advent of kdump, the assumption that the boot CPU when running
> an UP kernel is always the CPU with a particular hardware ID (often 0)
> (usually referred to as BSP on some architectures) is not valid anymore.
> The reason being that the dump capture kernel boots on the crashed CPU
> (the CPU that invoked crash_kexec), which may be or may not be that
> particular CPU.
> 
> As a consequence, the hardcoding of hard_smp_processor_id() to 0 on UP
> systems (see "linux/smp.h") is not correct.
> 
> This patch-set does the following:
> 
> 1- Remove hardcoding of hard_smp_processor_id on UP systems (patch 1).
> 
> 2- Move definition of hard_smp_processor_id for the UP case to
> architecture specific code ("asm/smp.h") where it belongs, so that each
> architecture can provide its own implementation (patch 1).
> 
> 3- Ask the hardware when possible to obtain the hardware processor id on
> i386 (patch 2), x86_64 (patch 3), and ia64 (patch 4), independently of
> whether CONFIG_SMP is set or not.
> 
> I guess that something similar could be done for the rest of the
> architectures, but since I am not an expert in all of them I am just
> moving the definition of hard_smp_processor_id to "asm/smp.h" for those.
> Of course, help from the respective maintainers to fill this gap would
> be greatly appreciated.
> 
> The patches have been tested on i386, x86_64, and ia64.

Sorry for the delay in getting back to you, I've been on the road.

All these patches seem fine to me.
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