Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763452AbXHQCFq (ORCPT ); Thu, 16 Aug 2007 22:05:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752592AbXHQCFf (ORCPT ); Thu, 16 Aug 2007 22:05:35 -0400 Received: from mx1.redhat.com ([66.187.233.31]:55298 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751845AbXHQCFd (ORCPT ); Thu, 16 Aug 2007 22:05:33 -0400 Message-ID: <46C50228.4000004@redhat.com> Date: Thu, 16 Aug 2007 22:04:24 -0400 From: Chris Snook User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: Herbert Xu CC: Stefan Richter , Paul Mackerras , Satyam Sharma , Christoph Lameter , "Paul E. McKenney" , Linux Kernel Mailing List , linux-arch@vger.kernel.org, Linus Torvalds , netdev@vger.kernel.org, Andrew Morton , ak@suse.de, heiko.carstens@de.ibm.com, davem@davemloft.net, schwidefsky@de.ibm.com, wensong@linux-vs.org, horms@verge.net.au, wjiang@resilience.com, cfriesen@nortel.com, zlynx@acm.org, rpjday@mindspring.com, jesper.juhl@gmail.com, segher@kernel.crashing.org Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures References: <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> <46C40587.7050708@s5r6.in-berlin.de> <20070816081049.GA1431@gondor.apana.org.au> <46C4AA26.4060707@redhat.com> <20070817000209.GC11594@gondor.apana.org.au> In-Reply-To: <20070817000209.GC11594@gondor.apana.org.au> 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: 1041 Lines: 26 Herbert Xu wrote: > On Thu, Aug 16, 2007 at 03:48:54PM -0400, Chris Snook wrote: >>> Can you find an actual atomic_read code snippet there that is >>> broken without the volatile modifier? >> A whole bunch of atomic_read uses will be broken without the volatile >> modifier once we start removing barriers that aren't needed if volatile >> behavior is guaranteed. > > Could you please cite the file/function names so we can > see whether removing the barrier makes sense? > > Thanks, At a glance, several architectures' implementations of smp_call_function() have one or more legitimate atomic_read() busy-waits that shouldn't be using CPU-relax. Some of them do work in the loop. I'm sure there are plenty more examples that various maintainers could find in their own code. -- 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/