From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754444Ab3KUWJ7 (ORCPT ); Thu, 21 Nov 2013 17:09:59 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:39545 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751663Ab3KUWJ6 (ORCPT ); Thu, 21 Nov 2013 17:09:58 -0500 Date: Thu, 21 Nov 2013 14:09:51 -0800 From: "Paul E. McKenney" To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu Subject: Re: [PATCH v2 RFC 1/3] documentation: Add needed ACCESS_ONCE() calls to memory-barriers.txt Message-ID: <20131121220950.GG4138@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20131121213055.GA6938@linux.vnet.ibm.com> <1385069489-7898-1-git-send-email-paulmck@linux.vnet.ibm.com> <20131121215517.GA16796@laptop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131121215517.GA16796@laptop.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13112122-9332-0000-0000-00000241E1FB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 21, 2013 at 10:55:17PM +0100, Peter Zijlstra wrote: > On Thu, Nov 21, 2013 at 01:31:27PM -0800, Paul E. McKenney wrote: > > From: "Paul E. McKenney" > > > > The Documentation/memory-barriers.txt file was written before the need > > for ACCESS_ONCE() was fully appreciated. It therefore contains no > > ACCESS_ONCE() calls, which can be a problem when people lift examples > > from it. This commit therefore adds ACCESS_ONCE() calls. > > So I find the repeated ACCESS_ONCE() significantly detracts from the > readability of the text. > > Can't we simply state that all accesses are assumed single-copy atomic > and this can be achieved for naturally aligned words using ACCESS_ONCE() > in C/C++ ? We could, but at the moment I would prefer the decrease in readability to the copy-and-paste bugs that omit needed ACCESS_ONCE() calls. Is there some way to get both ACCESS_ONCE() and readability? An abbreviation such as AO()? More easily distinguished variable names? Something else? Thanx, Paul