Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937589AbXHLTOl (ORCPT ); Sun, 12 Aug 2007 15:14:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933285AbXHLTO2 (ORCPT ); Sun, 12 Aug 2007 15:14:28 -0400 Received: from gate.crashing.org ([63.228.1.57]:35515 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933141AbXHLTO1 (ORCPT ); Sun, 12 Aug 2007 15:14:27 -0400 In-Reply-To: References: <20070808230733.GA17270@shell.boston.redhat.com> <46BAC2BE.1090106@redhat.com> <46BB508B.7050601@redhat.com> <1186683646.9669.20.camel@localhost> <1186912098.3852.11.camel@localhost> <74868f39491f8691afc5540f72679129@kernel.crashing.org> Mime-Version: 1.0 (Apple Message framework v623) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: Content-Transfer-Encoding: 7bit Cc: wjiang@resilience.com, wensong@linux-vs.org, heiko.carstens@de.ibm.com, linux-kernel@vger.kernel.org, ak@suse.de, cfriesen@nortel.com, netdev@vger.kernel.org, horms@verge.net.au, akpm@linux-foundation.org, schwidefsky@de.ibm.com, Chuck Ebbert , davem@davemloft.net, zlynx@acm.org, Chris Snook From: Segher Boessenkool Subject: Re: [PATCH] make atomic_t volatile on all architectures Date: Sun, 12 Aug 2007 21:13:20 +0200 To: Linus Torvalds X-Mailer: Apple Mail (2.623) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1517 Lines: 45 >> Yeah. Compiler errors are more annoying though I dare say ;-) > > Actually, compile-time errors are fine, Yes, they don't cause data corruption or anything like that, but I still don't think the 390 people want to ship a kernel that doesn't build -- and it seems they still need to support GCC versions before 4.0. Up until the day they can finally drop 3.x, they'll have to... > and easy to work around. ...use the simple workaround, annoying as it may be, at least it works. That's all I'm saying. > *Much* > more annoying is when gcc actively generates subtly bad code. Quite so. > We've had > use-after-free issues due to incorrect gcc liveness calculations etc, > and > inline asm has beeen one of the more common causes - exactly because > the > kernel is one of the few users (along with glibc) that uses it at all. The good news is that things are getting better since more and more of the RTL transformations are ripped out. > Now *those* are hard to find - the code works most of the time, but the > compiler has inserted a really subtle race condition into the code > (deallocated a local stack entry before last use). We had that with our > semaphore code at some point. Yeah, magnifying glass + lots of time kind of bug. Lovely :-/ Segher - 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/