Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759796AbXHTNhi (ORCPT ); Mon, 20 Aug 2007 09:37:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753900AbXHTNh1 (ORCPT ); Mon, 20 Aug 2007 09:37:27 -0400 Received: from mx1.redhat.com ([66.187.233.31]:44853 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752302AbXHTNhZ (ORCPT ); Mon, 20 Aug 2007 09:37:25 -0400 Message-ID: <46C997B1.1010800@redhat.com> Date: Mon, 20 Aug 2007 09:31:29 -0400 From: Chris Snook User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: Christoph Lameter CC: "Paul E. McKenney" , Herbert Xu , Linus Torvalds , Nick Piggin , Paul Mackerras , Segher Boessenkool , heiko.carstens@de.ibm.com, horms@verge.net.au, linux-kernel@vger.kernel.org, rpjday@mindspring.com, ak@suse.de, netdev@vger.kernel.org, cfriesen@nortel.com, akpm@linux-foundation.org, jesper.juhl@gmail.com, linux-arch@vger.kernel.org, zlynx@acm.org, satyam@infradead.org, schwidefsky@de.ibm.com, davem@davemloft.net, wensong@linux-vs.org, wjiang@resilience.com Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures References: <20070815234021.GA28775@gondor.apana.org.au> <3694fb2e4ed1e4d9bf873c0d050c911e@kernel.crashing.org> <46C3B50E.7010702@yahoo.com.au> <194369f4c96ea0e24decf8f9197d5bad@kernel.crashing.org> <46C505B2.6030704@yahoo.com.au> <18117.4848.695269.72976@cargo.ozlabs.ibm.com> <46C516BA.60700@yahoo.com.au> <20070817235912.GA24314@linux.vnet.ibm.com> <20070818000913.GA25585@gondor.apana.org.au> <20070818010818.GQ8464@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1553 Lines: 35 Christoph Lameter wrote: > On Fri, 17 Aug 2007, Paul E. McKenney wrote: > >> On Sat, Aug 18, 2007 at 08:09:13AM +0800, Herbert Xu wrote: >>> On Fri, Aug 17, 2007 at 04:59:12PM -0700, Paul E. McKenney wrote: >>>> gcc bugzilla bug #33102, for whatever that ends up being worth. ;-) >>> I had totally forgotten that I'd already filed that bug more >>> than six years ago until they just closed yours as a duplicate >>> of mine :) >>> >>> Good luck in getting it fixed! >> Well, just got done re-opening it for the third time. And a local >> gcc community member advised me not to give up too easily. But I >> must admit that I am impressed with the speed that it was identified >> as duplicate. >> >> Should be entertaining! ;-) > > Right. ROTFL... volatile actually breaks atomic_t instead of making it > safe. x++ becomes a register load, increment and a register store. Without > volatile we can increment the memory directly. It seems that volatile > requires that the variable is loaded into a register first and then > operated upon. Understandable when you think about volatile being used to > access memory mapped I/O registers where a RMW operation could be > problematic. So, if we want consistent behavior, we're pretty much screwed unless we use inline assembler everywhere? -- Chris - 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/