Return-Path: <linux-kernel-owner+w=401wt.eu-S1760980AbXHQTyY@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1760980AbXHQTyY (ORCPT <rfc822;w@1wt.eu>);
	Fri, 17 Aug 2007 15:54:24 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754930AbXHQTyH
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Fri, 17 Aug 2007 15:54:07 -0400
Received: from pentafluge.infradead.org ([213.146.154.40]:34158 "EHLO
	pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754446AbXHQTyF (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Fri, 17 Aug 2007 15:54:05 -0400
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all
	architectures
From: Arjan van de Ven <arjan@infradead.org>
To: paulmck@linux.vnet.ibm.com
Cc: Chris Friesen <cfriesen@nortel.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Nick Piggin <piggin@cyberone.com.au>,
       Satyam Sharma <satyam@infradead.org>,
       Herbert Xu <herbert@gondor.apana.org.au>,
       Paul Mackerras <paulus@samba.org>, Christoph Lameter <clameter@sgi.com>,
       Chris Snook <csnook@redhat.com>,
       Ilpo Jarvinen <ilpo.jarvinen@helsinki.fi>,
       Stefan Richter <stefanr@s5r6.in-berlin.de>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       linux-arch@vger.kernel.org, Netdev <netdev@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>, ak@suse.de,
       heiko.carstens@de.ibm.com, David Miller <davem@davemloft.net>,
       schwidefsky@de.ibm.com, wensong@linux-vs.org, horms@verge.net.au,
       wjiang@resilience.com, zlynx@acm.org, rpjday@mindspring.com,
       jesper.juhl@gmail.com, segher@kernel.crashing.org
In-Reply-To: <20070817194924.GG8464@linux.vnet.ibm.com>
References: <20070817035342.GA14744@gondor.apana.org.au>
	 <alpine.LFD.0.999.0708171142550.3666@enigma.security.iitk.ac.in>
	 <46C55E90.7010407@yahoo.com.au>
	 <alpine.LFD.0.999.0708171431150.3666@enigma.security.iitk.ac.in>
	 <46C56ADF.8010501@cyberone.com.au>
	 <alpine.LFD.0.999.0708171612440.3666@enigma.security.iitk.ac.in>
	 <46C59717.4020108@cyberone.com.au>
	 <alpine.LFD.0.999.0708170929580.30176@woody.linux-foundation.org>
	 <46C5EDF9.3090507@nortel.com>
	 <1187376873.2615.2.camel@laptopd505.fenrus.org>
	 <20070817194924.GG8464@linux.vnet.ibm.com>
Content-Type: text/plain
Organization: Intel International BV
Date: Fri, 17 Aug 2007 12:49:00 -0700
Message-Id: <1187380142.2615.6.camel@laptopd505.fenrus.org>
Mime-Version: 1.0
X-Mailer: Evolution 2.11.6.1 (2.11.6.1-1.fc8) 
Content-Transfer-Encoding: 7bit
X-SRS-Rewrite: SMTP reverse-path rewritten from <arjan@infradead.org> by pentafluge.infradead.org
	See http://www.infradead.org/rpr.html
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1000
Lines: 23


On Fri, 2007-08-17 at 12:49 -0700, Paul E. McKenney wrote:
> > > What about reading values modified in interrupt handlers, as in your 
> > > "random" case?  Or is this a bug where the user of atomic_read() is 
> > > invalidly expecting a read each time it is called?
> > 
> > the interrupt handler case is an SMP case since you do not know
> > beforehand what cpu your interrupt handler will run on.
> 
> With the exception of per-CPU variables, yes.

if you're spinning waiting for a per-CPU variable to get changed by an
interrupt handler... you have bigger problems than "volatile" ;-)

-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

-
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/