From mboxrd@z Thu Jan 1 00:00:00 1970 From: Segher Boessenkool Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures Date: Thu, 16 Aug 2007 21:32:03 +0200 Message-ID: <194369f4c96ea0e24decf8f9197d5bad@kernel.crashing.org> References: <46C32618.2080108@redhat.com> <20070815234021.GA28775@gondor.apana.org.au> <3694fb2e4ed1e4d9bf873c0d050c911e@kernel.crashing.org> <46C3B50E.7010702@yahoo.com.au> Mime-Version: 1.0 (Apple Message framework v623) Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Cc: heiko.carstens@de.ibm.com, horms@verge.net.au, linux-kernel@vger.kernel.org, rpjday@mindspring.com, ak@suse.de, netdev@vger.kernel.org, cfriesen@nortel.com, akpm@linux-foundation.org, torvalds@linux-foundation.org, jesper.juhl@gmail.com, linux-arch@vger.kernel.org, zlynx@acm.org, satyam@infradead.org, clameter@sgi.com, schwidefsky@de.ibm.com, Chris Snook , Herbert Xu , davem@davemloft.net, wensong@linux-vs.org, wjiang@resilience.com To: Nick Piggin Return-path: In-Reply-To: <46C3B50E.7010702@yahoo.com.au> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org >>>> Part of the motivation here is to fix heisenbugs. If I knew where >>>> they >>> >>> >>> By the same token we should probably disable optimisations >>> altogether since that too can create heisenbugs. >> Almost everything is a tradeoff; and so is this. I don't >> believe most people would find disabling all compiler >> optimisations an acceptable price to pay for some peace >> of mind. > > So why is this a good tradeoff? It certainly is better than disabling all compiler optimisations! > I also think that just adding things to APIs in the hope it might fix > up some bugs isn't really a good road to go down. Where do you stop? I look at it the other way: keeping the "volatile" semantics in atomic_XXX() (or adding them to it, whatever) helps _prevent_ bugs; certainly most people expect that behaviour, and also that behaviour is *needed* in some places and no other interface provides that functionality. [some confusion about barriers wrt atomics snipped] Segher