From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934130AbbENU6A (ORCPT ); Thu, 14 May 2015 16:58:00 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:58201 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933626AbbENU56 (ORCPT ); Thu, 14 May 2015 16:57:58 -0400 Date: Thu, 14 May 2015 13:57:51 -0700 From: "Paul E. McKenney" To: Mathieu Desnoyers Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby prani Subject: Re: [PATCH tip/core/rcu 2/3] documentation: Update rcu_dereference.txt based on WG21 discussions Message-ID: <20150514205750.GH6776@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20150512212234.GA32351@linux.vnet.ibm.com> <1431465787-32541-1-git-send-email-paulmck@linux.vnet.ibm.com> <1431465787-32541-2-git-send-email-paulmck@linux.vnet.ibm.com> <733020894.34.1431541990525.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <733020894.34.1431541990525.JavaMail.zimbra@efficios.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15051420-0029-0000-0000-000009C9ADDB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 13, 2015 at 06:33:10PM +0000, Mathieu Desnoyers wrote: > ----- Original Message ----- > > From: "Paul E. McKenney" > > > > This commit provides another caveat for the care and feeding of pointers > > returned by rcu_dereference() that was pointed out in discussions within > > the C++ standards committee. > > > > Signed-off-by: Paul E. McKenney > > Reviewed-by: Mathieu Desnoyers Thank you, applied. > BTW, reading through rcu_dereference.txt, I found a nit: > > operatiors -> operators Hmmm... Almost like I was trying (and spectacularly failing) to write the document in French. ;-) > Very interesting reading :) Glad you liked it! Thanx, Paul > Thanks! > > Mathieu > > > --- > > Documentation/RCU/rcu_dereference.txt | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/Documentation/RCU/rcu_dereference.txt > > b/Documentation/RCU/rcu_dereference.txt > > index ceb05da5a5ac..2d05c9241a33 100644 > > --- a/Documentation/RCU/rcu_dereference.txt > > +++ b/Documentation/RCU/rcu_dereference.txt > > @@ -193,6 +193,11 @@ o Be very careful about comparing pointers obtained from > > pointer. Note that the volatile cast in rcu_dereference() > > will normally prevent the compiler from knowing too much. > > > > + However, please note that if the compiler knows that the > > + pointer takes on only one of two values, a not-equal > > + comparison will provide exactly the information that the > > + compiler needs to deduce the value of the pointer. > > + > > o Disable any value-speculation optimizations that your compiler > > might provide, especially if you are making use of feedback-based > > optimizations that take data collected from prior runs. Such > > -- > > 1.8.1.5 > > > > > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com >