From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756153AbXHOTnN (ORCPT ); Wed, 15 Aug 2007 15:43:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752273AbXHOTmu (ORCPT ); Wed, 15 Aug 2007 15:42:50 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:49290 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752048AbXHOTms (ORCPT ); Wed, 15 Aug 2007 15:42:48 -0400 Date: Thu, 16 Aug 2007 01:24:42 +0530 (IST) From: Satyam Sharma X-X-Sender: satyam@enigma.security.iitk.ac.in To: "Paul E. McKenney" 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 In-Reply-To: <20070815185724.GH9645@linux.vnet.ibm.com> Message-ID: References: <46C2350A.1010807@redhat.com> <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 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org [ The Cc: list scares me. Should probably trim it. ] 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?)