Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756514AbXHRCDt (ORCPT ); Fri, 17 Aug 2007 22:03:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752137AbXHRCDh (ORCPT ); Fri, 17 Aug 2007 22:03:37 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:49657 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750816AbXHRCDf (ORCPT ); Fri, 17 Aug 2007 22:03:35 -0400 Date: Sat, 18 Aug 2007 07:45:53 +0530 (IST) From: Satyam Sharma X-X-Sender: satyam@enigma.security.iitk.ac.in To: Nick Piggin cc: Stefan Richter , paulmck@linux.vnet.ibm.com, Herbert Xu , Paul Mackerras , Christoph Lameter , 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 In-Reply-To: <46C59B09.8040004@cyberone.com.au> Message-ID: 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> <46C40587.7050708@s5r6.in-berlin.de> <20070816081049.GA1431@gondor.apana.org.au> <46C41EE4.9090806@s5r6.in-berlin.de> <46C42767.4070104@s5r6.in-berlin.de> <20070816104250.GB2927@gondor.apana.org.au> <20070816163441.GB16957@linux.vnet.ibm.com> <46C512EB.7020603@yahoo.com.au> <46C54D74.60101@s5r6.in-berlin.de> <46C556F1.8000407@yahoo.com.au> <46C5672E.4060003@cyberone.com.au> <46C58B93.5000408@cyberone.com.au> <46C59B09.8040004@cyberone.com.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1497 Lines: 35 On Fri, 17 Aug 2007, Nick Piggin wrote: > Satyam Sharma wrote: > > > I didn't quite understand what you said here, so I'll tell what I think: > > > > * foo() is a compiler barrier if the definition of foo() is invisible to > > the compiler at a callsite. > > > > * foo() is also a compiler barrier if the definition of foo() includes > > a barrier, and it is inlined at the callsite. > > > > If the above is wrong, or if there's something else at play as well, > > do let me know. > > [...] > If a function is not completely visible to the compiler (so it can't > determine whether a barrier could be in it or not), then it must always > assume it will contain a barrier so it always does the right thing. Yup, that's what I'd said just a few sentences above, as you can see. I was actually asking for "elaboration" on "how a compiler determines that function foo() (say foo == schedule), even when it cannot see that it has a barrier(), as you'd mentioned, is a 'sleeping' function" actually, and whether compilers have a "notion of sleep to automatically assume a compiler barrier whenever such a sleeping function foo() is called". But I think you've already qualified the discussion to this kernel, so okay, I shouldn't nit-pick anymore. - 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/