From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta7.messagelabs.com (mail6.bemta7.messagelabs.com [216.82.255.55]) by kanga.kvack.org (Postfix) with ESMTP id 34D306B0011 for ; Wed, 1 Jun 2011 11:48:21 -0400 (EDT) Message-ID: <4DE65DB6.4050801@zytor.com> Date: Wed, 01 Jun 2011 08:41:42 -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> <4DDE9670.3060709@zytor.com> <4DDE9C01.2090104@zytor.com> <1306445159.2543.25.camel@edumazet-laptop> <4DE50632.90906@zytor.com> <4DE576EA.6070906@zytor.com> <4DE57FBB.8040408@zytor.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Eric Dumazet , Pekka Enberg , David Rientjes , linux-mm@kvack.org, Thomas Gleixner On 06/01/2011 07:13 AM, Christoph Lameter wrote: >> >> Per your own description: >> >> "CMPXCHG_DOUBLE only compiles in detection support. It needs to be set >> if there is a chance that processor supports these instructions." >> >> That condition is always TRUE, so no Kconfig is needed. > > There are several early processors (especially from AMD it seems) that do > not support cmpxchg16b. If one builds a kernel specifically for the early > cpus then the support does not need to be enabled. > We don't support building kernels specifically for those early CPUs as far as I know. Besides, it is a very small set. Even if we did, the conditional as you have specified it is wrong, and I mean "not even in the general ballpark of correct". > This is also an issue going beyond x86. Other platforms mostly do not > support double word cmpxchg so the code for this feature also does not > need to be included for those builds. That's fine; just set it unconditionally for x86. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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