Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756882AbXHOGul (ORCPT ); Wed, 15 Aug 2007 02:50:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750859AbXHOGua (ORCPT ); Wed, 15 Aug 2007 02:50:30 -0400 Received: from rhun.apana.org.au ([64.62.148.172]:2482 "EHLO arnor.apana.org.au" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750824AbXHOGu2 (ORCPT ); Wed, 15 Aug 2007 02:50:28 -0400 From: Herbert Xu To: csnook@redhat.com (Chris Snook) Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures Cc: satyam@infradead.org, clameter@sgi.com, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, torvalds@linux-foundation.org, netdev@vger.kernel.org, akpm@linux-foundation.org, 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 Organization: Core In-Reply-To: <46C2350A.1010807@redhat.com> X-Newsgroups: apana.lists.os.linux.kernel,apana.lists.os.linux.netdev User-Agent: tin/1.7.4-20040225 ("Benbecula") (UNIX) (Linux/2.6.17-rc4 (i686)) Message-Id: Date: Wed, 15 Aug 2007 14:49:03 +0800 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1151 Lines: 25 Chris Snook wrote: > > Because atomic operations are generally used for synchronization, which requires > volatile behavior. Most such codepaths currently use an inefficient barrier(). > Some forget to and we get bugs, because people assume that atomic_read() > actually reads something, and atomic_write() actually writes something. Worse, > these are architecture-specific, even compiler version-specific bugs that are > often difficult to track down. I'm yet to see a single example from the current tree where this patch series is the correct solution. So far the only example has been a buggy piece of code which has since been fixed with a cpu_relax. 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/