Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933188AbaLBVuR (ORCPT ); Tue, 2 Dec 2014 16:50:17 -0500 Received: from e38.co.us.ibm.com ([32.97.110.159]:53460 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754320AbaLBVuO (ORCPT ); Tue, 2 Dec 2014 16:50:14 -0500 Date: Tue, 2 Dec 2014 13:50:06 -0800 From: "Paul E. McKenney" To: Jonathan Corbet Cc: Srikanth Thokala , linux-doc@vger.kernel.org, "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] Documentation: memory-barriers: Fix typo in the first example Message-ID: <20141202215006.GT25340@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1416285598-6630-1-git-send-email-sriku.linux@gmail.com> <20141202161519.581ea1af@lwn.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141202161519.581ea1af@lwn.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14120221-0029-0000-0000-0000060F1E2E Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 02, 2014 at 04:15:19PM -0500, Jonathan Corbet wrote: > On Thu, 27 Nov 2014 12:19:26 +0530 > Srikanth Thokala wrote: > > > Hi, > > > > Kindly review the patch. > > To me it looks right. Something like this, though, needs an ack from > Paul (cc'd) before I can be really confident. Paul...? I am guessing that this patch is against an old version of this file (there have been two patches applied to this example in the last six months). I believe that the current version is correct, in other words, that Alexey Dobriyan and Pranith Kumar beat you to this one. ;-) Please see below for the current version, which is in -tip as of November 20th. Thanx, Paul > jon > > > Thanks > > Srikanth > > > > On Tue, Nov 18, 2014 at 10:09 AM, Srikanth Thokala > > wrote: > > > In the first example, the loads into 'x' and 'y' on CPU 2 doesn't > > > match the sequence of events described below it. To match the > > > sequence of events, the values of 'A' and 'B' should be loaded > > > into 'x' and 'y' respectively. > > > > > > Signed-off-by: Srikanth Thokala > > > --- > > > 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 22a969c..2770bce 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; > > > > > > The set of accesses as seen by the memory system in the middle can be arranged > > > in 24 different combinations: For example, consider the following sequence of events: CPU 1 CPU 2 =============== =============== { A == 1; B == 2 } A = 3; x = B; B = 4; y = A; The set of accesses as seen by the memory system in the middle can be arranged in 24 different combinations: STORE A=3, STORE B=4, y=LOAD A->3, x=LOAD B->4 STORE A=3, STORE B=4, x=LOAD B->4, y=LOAD A->3 STORE A=3, y=LOAD A->3, STORE B=4, x=LOAD B->4 STORE A=3, y=LOAD A->3, x=LOAD B->2, STORE B=4 STORE A=3, x=LOAD B->2, STORE B=4, y=LOAD A->3 STORE A=3, x=LOAD B->2, y=LOAD A->3, STORE B=4 STORE B=4, STORE A=3, y=LOAD A->3, x=LOAD B->4 STORE B=4, ... ... and can thus result in four different combinations of values: x == 2, y == 1 x == 2, y == 3 x == 4, y == 1 x == 4, y == 3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/