Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935261AbXHOUST (ORCPT ); Wed, 15 Aug 2007 16:18:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765444AbXHOURy (ORCPT ); Wed, 15 Aug 2007 16:17:54 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.145]:45557 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756697AbXHOURw (ORCPT ); Wed, 15 Aug 2007 16:17:52 -0400 Date: Wed, 15 Aug 2007 13:17:48 -0700 From: "Paul E. McKenney" To: Satyam Sharma Cc: Segher Boessenkool , horms@verge.net.au, Stefan Richter , Linux Kernel Mailing List , rpjday@mindspring.com, netdev@vger.kernel.org, ak@suse.de, cfriesen@nortel.com, Heiko Carstens , jesper.juhl@gmail.com, linux-arch@vger.kernel.org, Andrew Morton , zlynx@acm.org, clameter@sgi.com, schwidefsky@de.ibm.com, Chris Snook , Herbert Xu , davem@davemloft.net, Linus Torvalds , wensong@linux-vs.org, wjiang@resilience.com Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures Message-ID: <20070815201748.GN9645@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20070815081841.GA16551@osiris.boeblingen.de.ibm.com> <46C30540.2070603@s5r6.in-berlin.de> <20070815145207.GA23106@gondor.apana.org.au> <46C3253F.5090707@s5r6.in-berlin.de> <20070815162722.GD9645@linux.vnet.ibm.com> <20070815185724.GH9645@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1875 Lines: 41 On Thu, Aug 16, 2007 at 01:24:42AM +0530, Satyam Sharma wrote: > [ The Cc: list scares me. Should probably trim it. ] Trim away! ;-) > On Wed, 15 Aug 2007, Paul E. McKenney wrote: > > > On Wed, Aug 15, 2007 at 08:31:25PM +0200, Segher Boessenkool wrote: > > > >>How does the compiler know that msleep() has got barrier()s? > > > > > > > >Because msleep_interruptible() is in a separate compilation unit, > > > >the compiler has to assume that it might modify any arbitrary global. > > > > > > No; compilation units have nothing to do with it, GCC can optimise > > > across compilation unit boundaries just fine, if you tell it to > > > compile more than one compilation unit at once. > > > > Last I checked, the Linux kernel build system did compile each .c file > > as a separate compilation unit. > > > > > What you probably mean is that the compiler has to assume any code > > > it cannot currently see can do anything (insofar as allowed by the > > > relevant standards etc.) > > I think this was just terminology confusion here again. Isn't "any code > that it cannot currently see" the same as "another compilation unit", > and wouldn't the "compilation unit" itself expand if we ask gcc to > compile more than one unit at once? Or is there some more specific > "definition" for "compilation unit" (in gcc lingo, possibly?) This is indeed my understanding -- "compilation unit" is whatever the compiler looks at in one go. I have heard the word "module" used for the minimal compilation unit covering a single .c file and everything that it #includes, but there might be a better name for this. Thanx, Paul - 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/