linux-ext4 - Re: [PATCH 1/1] x86: fix text

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Message-ID: <4811FF60.6040905@zytor.com>
Date:	Fri, 25 Apr 2008 08:57:20 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Slaby <jirislaby@...il.com>,
	David Miller <davem@...emloft.net>, zdenek.kabelac@...il.com,
	rjw@...k.pl, paulmck@...ux.vnet.ibm.com, akpm@...ux-foundation.org,
	linux-ext4@...r.kernel.org, herbert@...dor.apana.org.au,
	penberg@...helsinki.fi, clameter@....com,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Andi Kleen <andi@...stfloor.org>, pageexec@...email.hu,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: [PATCH 1/1] x86: fix text_poke

Ingo Molnar wrote:
> 
> text_poke() itself only applies/unapplies the LOCK prefix - a single 
> byte. We shouldnt be doing that at all: the cost of LOCK is 
> insignificant (a few cycles) and most systems are SMP anyway.
> 

Alas, on older CPUs the cost of LOCK can be massive.  The question is 
how much we really care - the embedded people (who would definitely be 
affected) will simply build UP kernels, and this only affects booting 
SMP kernels on UP.

	-hpa
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