From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755809Ab3KVPjk (ORCPT ); Fri, 22 Nov 2013 10:39:40 -0500 Received: from merlin.infradead.org ([205.233.59.134]:48808 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753381Ab3KVPjj (ORCPT ); Fri, 22 Nov 2013 10:39:39 -0500 Date: Fri, 22 Nov 2013 16:39:08 +0100 From: Peter Zijlstra To: "Paul E. McKenney" 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: <20131122153908.GQ10022@twins.programming.kicks-ass.net> References: <20131121213055.GA6938@linux.vnet.ibm.com> <1385069489-7898-1-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1385069489-7898-1-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. > Under the 'COMPILER BARRIER' section we state that: "This is a general barrier - lesser varieties of compiler barrier do not exist." One could argue ACCESS_ONCE() is such a lesser barrier.