From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751910AbZJWMdZ (ORCPT ); Fri, 23 Oct 2009 08:33:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751666AbZJWMdY (ORCPT ); Fri, 23 Oct 2009 08:33:24 -0400 Received: from tomts16-srv.bellnexxia.net ([209.226.175.4]:35603 "EHLO tomts16-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751581AbZJWMdX (ORCPT ); Fri, 23 Oct 2009 08:33:23 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AnUHAC8+4UpGGN1W/2dsb2JhbACBUJo2vGiEPwSBXQ Date: Fri, 23 Oct 2009 08:33:27 -0400 From: Mathieu Desnoyers To: David Miller Cc: nickpiggin@yahoo.com.au, linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com Subject: Re: sparc64 cmpxchg is not a full memory barrier anymore ? Message-ID: <20091023123327.GA14058@Krystal> References: <20091022183242.GA19307@Krystal> <20091022.145645.249762938.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20091022.145645.249762938.davem@davemloft.net> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.27.31-grsec (i686) X-Uptime: 08:32:24 up 65 days, 23:21, 2 users, load average: 0.69, 0.28, 0.15 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * David Miller (davem@davemloft.net) wrote: > From: Mathieu Desnoyers > Date: Thu, 22 Oct 2009 14:32:42 -0400 > > > The same applies to the other atomic instructions we find in this list. > > How is the correct ordering of loads wrt to cmxchg (and other atomic > > ops) still ensured by this modification? > > All actual sparc64 chips implement more strict ordering than > the V9 specification permits. The memory barriers were just > nops and actually not doing anything more than the chip > already does for us. OK. Perhaps adding a comment to that effect near sparc mb() implementation would be appropriate ? Thanks, Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68