From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id 695026B0011 for ; Thu, 26 May 2011 14:12:11 -0400 (EDT) Message-ID: <4DDE9670.3060709@zytor.com> Date: Thu, 26 May 2011 11:05:36 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [slubllv5 07/25] x86: Add support for cmpxchg_double References: <20110516202605.274023469@linux.com> <20110516202625.197639928@linux.com> In-Reply-To: <20110516202625.197639928@linux.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Pekka Enberg , David Rientjes , Eric Dumazet , linux-mm@kvack.org, Thomas Gleixner On 05/16/2011 01:26 PM, Christoph Lameter wrote: > A simple implementation that only supports the word size and does not > have a fallback mode (would require a spinlock). > > And 32 and 64 bit support for cmpxchg_double. cmpxchg double uses > the cmpxchg8b or cmpxchg16b instruction on x86 processors to compare > and swap 2 machine words. This allows lockless algorithms to move more > context information through critical sections. > > Set a flag CONFIG_CMPXCHG_DOUBLE to signal the support of that feature > during kernel builds. > > Signed-off-by: Christoph Lameter > > > +config CMPXCHG_DOUBLE > + def_bool X86_64 || (X86_32 && !M386) > + CMPXCHG16B is not a baseline feature for the Linux x86-64 build, and CMPXCHG8G is a Pentium, not a 486, feature. Nacked-by: H. Peter Anvin -hpa -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org