Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1425607AbWLHQcN (ORCPT ); Fri, 8 Dec 2006 11:32:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1425600AbWLHQcM (ORCPT ); Fri, 8 Dec 2006 11:32:12 -0500 Received: from caramon.arm.linux.org.uk ([217.147.92.249]:3388 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760764AbWLHQcL (ORCPT ); Fri, 8 Dec 2006 11:32:11 -0500 Date: Fri, 8 Dec 2006 16:31:27 +0000 From: Russell King To: Christoph Lameter Cc: Nick Piggin , David Howells , 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 Message-ID: <20061208163127.GD31068@flint.arm.linux.org.uk> Mail-Followup-To: Christoph Lameter , Nick Piggin , David Howells , torvalds@osdl.org, akpm@osdl.org, linux-arm-kernel@lists.arm.linux.org.uk, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1369 Lines: 30 On Fri, Dec 08, 2006 at 08:06:23AM -0800, Christoph Lameter wrote: > On Fri, 8 Dec 2006, Russell King wrote: > > > I'm trying to suggest a better implementation for atomic ops rather > > than just bowing to this x86-centric "cmpxchg is the best, everyone > > must implement it" mentality. > > cmpxchg is the simplest solution to realize many other atomic operations > and its widely available on a wide variety of platforms. It is the most > universal atomic instruction that I know of. Other atomic operations may > be more efficient but certainly cmpxchg is the most universal. > > Having multiple instructions with restrictions of what can be done in > between just complicates the use and seems to be arch specific. I have not > seen a better solution. Are you really advocating the weirdly complex > ll/sc be adopted by other architectures? You're advocating cmpxchg is adopted by all architectures. It isn't available on many architectures, and those which it can be requires unnecessarily complicated coding. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: - 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/