linux-kernel - Re: [PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptible kernel and CPU hotplug

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Message-ID: <alpine.LFD.1.10.0808150854140.3324@nehalem.linux-foundation.org>
Date:	Fri, 15 Aug 2008 09:06:38 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
cc:	Ingo Molnar <mingo@...e.hu>, Jeremy Fitzhardinge <jeremy@...p.org>,
	Harvey Harrison <harvey.harrison@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Steven Rostedt <srostedt@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Roland McGrath <roland@...hat.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Gregory Haskins <ghaskins@...ell.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	Clark Williams <williams@...hat.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptible
 kernel and CPU hotplug



On Thu, 14 Aug 2008, Mathieu Desnoyers wrote:
>
> Changing the 0x90 (single-byte nop) currently used into a 0x3E DS segment
> override prefix should fix this issue. Since the default of the atomic
> instructions is to use the DS segment anyway, it should not affect the
> behavior.

Ok, so I think this is an _excellent_ patch, but I'd like to also then use 
LOCK_PREFIX in include/asm-x86/futex.h.

See commit 9d55b9923a1b7ea8193b8875c57ec940dc2ff027.

		Linus
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