From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423361AbXDYSP3 (ORCPT ); Wed, 25 Apr 2007 14:15:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423364AbXDYSP3 (ORCPT ); Wed, 25 Apr 2007 14:15:29 -0400 Received: from ns.suse.de ([195.135.220.2]:54462 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423361AbXDYSP2 (ORCPT ); Wed, 25 Apr 2007 14:15:28 -0400 From: Andi Kleen Organization: SUSE Linux Products GmbH, Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg) To: Jeremy Fitzhardinge Subject: Re: [PATCH 09/25] xen: Account for time stolen by Xen Date: Wed, 25 Apr 2007 20:15:06 +0200 User-Agent: KMail/1.9.6 Cc: Andrew Morton , virtualization@lists.osdl.org, lkml , john stultz , Keir Fraser References: <20070423215638.563901986@goop.org> <200704251115.49966.ak@suse.de> <462F9A4E.5050905@goop.org> In-Reply-To: <462F9A4E.5050905@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200704252015.06269.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 25 April 2007 20:13:34 Jeremy Fitzhardinge wrote: > Andi Kleen wrote: > >> + > >> + do { > >> + state_time = state->state_entry_time; > >> + barrier(); > >> > > > > Should be likely rmb > > We discussed this, and decided that it wasn't necessary. The state is > always updated by the current CPU, so if it changes under our feet it > will be because we were preempted, and so that should shoot down any > speculated reads. Then the barrier shouldn't be needed at all? Anyways needs comments -Andi