Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1425909AbWLHRGt (ORCPT ); Fri, 8 Dec 2006 12:06:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1425908AbWLHRGs (ORCPT ); Fri, 8 Dec 2006 12:06:48 -0500 Received: from omx2-ext.sgi.com ([192.48.171.19]:40851 "EHLO omx2.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1425909AbWLHRGp (ORCPT ); Fri, 8 Dec 2006 12:06:45 -0500 Date: Fri, 8 Dec 2006 09:06:00 -0800 (PST) From: Christoph Lameter To: David Howells cc: Russell King , Nick Piggin , torvalds@osdl.org, akpm@osdl.org, linux-arm-kernel@lists.arm.linux.org.uk, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it In-Reply-To: <4595.1165597017@redhat.com> Message-ID: References: <20061206164314.19870.33519.stgit@warthog.cambridge.redhat.com> <20061206190025.GC9959@flint.arm.linux.org.uk> <20061206195820.GA15281@flint.arm.linux.org.uk> <4577DF5C.5070701@yahoo.com.au> <20061207150303.GB1255@flint.arm.linux.org.uk> <4578BD7C.4050703@yahoo.com.au> <20061208085634.GA25751@flint.arm.linux.org.uk> <4595.1165597017@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 817 Lines: 21 On Fri, 8 Dec 2006, David Howells wrote: > > It is the most universal atomic instruction that I know of. > > I think TAS-type things and XCHG-type things are more common. Huh? The most popular architectures are i386 x86_64 sparc ia64 etc which all have one or the other form of cmpxchg (some issues with early sparc and i386). And yes the xchg was the first multiprocessor instruction and therefore is also available on very old processors. > In fact I think more things have LL/SC than have CMPXCHG. LL/SC can be easily used to come up with a cmpxchg equivalent. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/