From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752060AbaH1UBg (ORCPT ); Thu, 28 Aug 2014 16:01:36 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:35024 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751086AbaH1UBe (ORCPT ); Thu, 28 Aug 2014 16:01:34 -0400 Date: Thu, 28 Aug 2014 13:01:29 -0700 From: "Paul E. McKenney" To: Randy Dunlap Cc: Ganesh Rapolu , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, David Howells , Alexey Dobriyan , Andrew Morton Subject: Re: [PATCH] DOCUMENTATION: Fixed typo in an example in memory-barriers.txt Message-ID: <20140828200129.GG5001@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <53F8D6DD.90306@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53F8D6DD.90306@infradead.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14082820-1542-0000-0000-000004602F49 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 23, 2014 at 11:01:01AM -0700, Randy Dunlap wrote: > On 08/22/14 23:05, Ganesh Rapolu wrote: > > In the first example in the memory-barriers.txt file, CPU 2 is assigned to > > run (x = B; y = A;). However, the rest of the example proceeds as if CPU 2 had been > > running (x = A; y = B;) as shown by the descriptions of the possible executions: > > > > STORE A=3, STORE B=4, x=LOAD A->3, y=LOAD B->4 > > STORE A=3, STORE B=4, y=LOAD B->4, x=LOAD A->3 > > STORE A=3, x=LOAD A->3, STORE B=4, y=LOAD B->4 > > STORE A=3, x=LOAD A->3, y=LOAD B->2, STORE B=4 > > STORE A=3, y=LOAD B->2, STORE B=4, x=LOAD A->3 > > STORE A=3, y=LOAD B->2, x=LOAD A->3, STORE B=4 > > STORE B=4, STORE A=3, x=LOAD A->3, y=LOAD B->4 > > STORE B=4, ... > > ... > > > > The change was merely to make the inital evironment consistent with what happens in the > > rest of the example. > > > > Signed-off-by: Ganesh Rapolu > > > Comments David, Alexey, Andrew, Paul? > > This would revert Alexey's patch 615cc2c9cf9529846fbc342560d6787c2ccaaeea: > "Documentation/memory-barriers.txt: fix important typo re memory barriers" > that was merged on June 6, 2014. > > Thanks. > > > > --- > > Documentation/memory-barriers.txt | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt > > index a4de88f..9a46bbe 100644 > > --- a/Documentation/memory-barriers.txt > > +++ b/Documentation/memory-barriers.txt > > @@ -115,8 +115,8 @@ For example, consider the following sequence of events: > > CPU 1 CPU 2 > > =============== =============== > > { A == 1; B == 2 } > > - A = 3; x = B; > > - B = 4; y = A; > > + A = 3; x = A; > > + B = 4; y = B; Alexey's patch was correct as far as it went, but it was incomplete. (Read his commit log for more information.) Would either of you like to send a patch fixing up the combinations? Thanx, Paul > > The set of accesses as seen by the memory system in the middle can be arranged > > in 24 different combinations: > > > > > -- > ~Randy >