From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id D33176B0011 for ; Tue, 31 May 2011 20:01:07 -0400 (EDT) Message-ID: <4DE57FBB.8040408@zytor.com> Date: Tue, 31 May 2011 16:54:35 -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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 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 05/31/2011 04:49 PM, Christoph Lameter wrote: >>> >>> +# >>> +# CMPXCHG_DOUBLE needs to be set to enable the kernel to use cmpxchg16/8b >>> +# for cmpxchg_double if it find processor flags that indicate that the >>> +# capabilities are available. CMPXCHG_DOUBLE only compiles in >>> +# detection support. It needs to be set if there is a chance that processor >>> +# supports these instructions. >>> +# >>> +config CMPXCHG_DOUBLE >>> + def_bool GENERIC_CPU || X86_GENERIC || !M386 >>> + >>> config X86_L1_CACHE_SHIFT >>> int >>> default "7" if MPENTIUM4 || MPSC >> >> Per previous discussion: >> >> - Drop this Kconfig option (it is irrelevant.) CONFIG_CMPXCHG_LOCAL is >> different: it indicates that CMPXCHG is *guaranteed* to exist. > > Right but this is for cmpxchg16b which means that we need to check a > bit in the processor flags. Isnt this what you suggested? > 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. -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