Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030243AbXHPCKR (ORCPT ); Wed, 15 Aug 2007 22:10:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761188AbXHPCJx (ORCPT ); Wed, 15 Aug 2007 22:09:53 -0400 Received: from rhun.apana.org.au ([64.62.148.172]:2471 "EHLO arnor.apana.org.au" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1760627AbXHPCJv (ORCPT ); Wed, 15 Aug 2007 22:09:51 -0400 Date: Thu, 16 Aug 2007 10:08:51 +0800 From: Herbert Xu To: Satyam Sharma Cc: Christoph Lameter , "Paul E. McKenney" , Paul Mackerras , Stefan Richter , Chris Snook , 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 Message-ID: <20070816020851.GA30809@gondor.apana.org.au> References: <18115.35524.56393.347841@cargo.ozlabs.ibm.com> <20070816003948.GY9645@linux.vnet.ibm.com> <20070816005348.GA9645@linux.vnet.ibm.com> <20070816011414.GC9645@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1496 Lines: 35 On Thu, Aug 16, 2007 at 07:45:44AM +0530, Satyam Sharma wrote: > > Completely agreed, again. To summarize again (had done so about ~100 mails > earlier in this thread too :-) ... > > atomic_{read,set}_volatile() -- guarantees volatility also along with > atomicity (the two _are_ different concepts after all, irrespective of > whether callsites normally want one with the other or not) > > atomic_{read,set}_nonvolatile() -- only guarantees atomicity, compiler > free to elid / coalesce / optimize such accesses, can keep the object > in question cached in a local register, leads to smaller text, etc. > > As to which one should be the default atomic_read() is a question of > whether majority of callsites (more weightage to important / hot > codepaths, lesser to obscure callsites) want a particular behaviour. > > Do we have a consensus here? (hoping against hope, probably :-) I can certainly agree with this. But I have to say that I still don't know of a single place where one would actually use the volatile variant. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt - 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/