From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751946Ab3HTCh6 (ORCPT ); Mon, 19 Aug 2013 22:37:58 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:39216 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751869Ab3HTCh5 (ORCPT ); Mon, 19 Aug 2013 22:37:57 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 3/3] doc: Fix memory-barrier control-dependency example Date: Mon, 19 Aug 2013 19:37:47 -0700 Message-Id: <1376966267-29949-3-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1376966267-29949-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20130820023717.GA29357@linux.vnet.ibm.com> <1376966267-29949-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13082002-4834-0000-0000-00000A50EFAB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" Each control-dependency example needs its barriers between the "if" condition and the body of the "if" because a control dependency is a dependency induced by a branch. This commit makes the needed adjustment. Reported-by: Yongming Shen Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- Documentation/memory-barriers.txt | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index fa5d8a9..c8c42e6 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -531,9 +531,10 @@ dependency barrier to make it work correctly. Consider the following bit of code: q = &a; - if (p) + if (p) { + q = &b; - + } x = *q; This will not have the desired effect because there is no actual data @@ -542,9 +543,10 @@ attempting to predict the outcome in advance. In such a case what's actually required is: q = &a; - if (p) + if (p) { + q = &b; - + } x = *q; -- 1.8.1.5