Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757432AbXHQDzc (ORCPT ); Thu, 16 Aug 2007 23:55:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753352AbXHQDzU (ORCPT ); Thu, 16 Aug 2007 23:55:20 -0400 Received: from rhun.apana.org.au ([64.62.148.172]:4872 "EHLO arnor.apana.org.au" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752821AbXHQDzS (ORCPT ); Thu, 16 Aug 2007 23:55:18 -0400 Date: Fri, 17 Aug 2007 11:53:42 +0800 From: Herbert Xu To: Paul Mackerras Cc: Linus Torvalds , Christoph Lameter , Chris Snook , Ilpo J?rvinen , Satyam Sharma , "Paul E. McKenney" , Stefan Richter , Linux Kernel Mailing List , linux-arch@vger.kernel.org, Netdev , Andrew Morton , ak@suse.de, heiko.carstens@de.ibm.com, David Miller , 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: <20070817035342.GA14744@gondor.apana.org.au> References: <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> <46C4ABA5.9010804@redhat.com> <18117.1287.779351.836552@cargo.ozlabs.ibm.com> <18117.6495.397597.582736@cargo.ozlabs.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <18117.6495.397597.582736@cargo.ozlabs.ibm.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1239 Lines: 26 On Fri, Aug 17, 2007 at 01:43:27PM +1000, Paul Mackerras wrote: > > The cost of doing so seems to me to be well down in the noise - 44 > bytes of extra kernel text on a ppc64 G5 config, and I don't believe > the extra few cycles for the occasional extra load would be measurable > (they should all hit in the L1 dcache). I don't mind if x86[-64] have > atomic_read/set be nonvolatile and find all the missing barriers, but > for now on powerpc, I think that not having to find those missing > barriers is worth the 0.00076% increase in kernel text size. BTW, the sort of missing barriers that triggered this thread aren't that subtle. It'll result in a simple lock-up if the loop condition holds upon entry. At which point it's fairly straightforward to find the culprit. 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/