From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures Date: Sat, 18 Aug 2007 14:56:52 -0700 Message-ID: <20070818215652.GD7628@linux.vnet.ibm.com> References: <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> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: 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, Chris Snook , davem@davemloft.net, wensong@linux-vs.org, wjiang@resilience.com To: Christoph Lameter Return-path: Received: from e3.ny.us.ibm.com ([32.97.182.143]:45439 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757581AbXHRV45 (ORCPT ); Sat, 18 Aug 2007 17:56:57 -0400 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, Aug 17, 2007 at 06:24:15PM -0700, 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. > > See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3506 Yep. The initial reaction was in fact to close my bug as a duplicate of 3506. But I was not asking for atomicity, but rather for smaller code to be generated, so I reopened it. Thanx, Paul