Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758969AbXIJS7p (ORCPT ); Mon, 10 Sep 2007 14:59:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754119AbXIJS7f (ORCPT ); Mon, 10 Sep 2007 14:59:35 -0400 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:43833 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751651AbXIJS7d (ORCPT ); Mon, 10 Sep 2007 14:59:33 -0400 Date: Mon, 10 Sep 2007 11:59:29 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Segher Boessenkool cc: Paul Mackerras , heiko.carstens@de.ibm.com, horms@verge.net.au, Stefan Richter , Satyam Sharma , Linux Kernel Mailing List , David Miller , "Paul E. McKenney" , =?ISO-8859-1?Q?Ilpo_J=E4rvinen?= , ak@suse.de, cfriesen@nortel.com, rpjday@mindspring.com, Netdev , jesper.juhl@gmail.com, linux-arch@vger.kernel.org, Andrew Morton , zlynx@acm.org, schwidefsky@de.ibm.com, Chris Snook , Herbert Xu , Linus Torvalds , wensong@linux-vs.org, wjiang@resilience.com Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures In-Reply-To: Message-ID: References: <20070816003948.GY9645@linux.vnet.ibm.com> <18115.44462.622801.683446@cargo.ozlabs.ibm.com> <20070816020042.GA30650@gondor.apana.org.au> <18115.45316.702491.681906@cargo.ozlabs.ibm.com> <18115.52863.638655.658466@cargo.ozlabs.ibm.com> <20070816053945.GB32442@gondor.apana.org.au> <18115.62741.807704.969977@cargo.ozlabs.ibm.com> <20070816070907.GA964@gondor.apana.org.au> <46C4ABA5.9010804@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: 780 Lines: 18 On Fri, 17 Aug 2007, Segher Boessenkool wrote: > "volatile" has nothing to do with reordering. atomic_dec() writes > to memory, so it _does_ have "volatile semantics", implicitly, as > long as the compiler cannot optimise the atomic variable away > completely -- any store counts as a side effect. Stores can be reordered. Only x86 has (mostly) implicit write ordering. So no atomic_dec has no volatile semantics and may be reordered on a variety of processors. Writes to memory may not follow code order on several processors. - 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/