From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262281AbVF1Xnb (ORCPT ); Tue, 28 Jun 2005 19:43:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262288AbVF1XnX (ORCPT ); Tue, 28 Jun 2005 19:43:23 -0400 Received: from smtp203.mail.sc5.yahoo.com ([216.136.129.93]:56684 "HELO smtp203.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S262281AbVF1XLI (ORCPT ); Tue, 28 Jun 2005 19:11:08 -0400 Message-ID: <42C1D8F4.2010601@yahoo.com.au> Date: Wed, 29 Jun 2005 09:10:44 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.6) Gecko/20050324 Debian/1.7.6-1 X-Accept-Language: en MIME-Version: 1.0 To: Christoph Lameter CC: William Lee Irwin III , "David S. Miller" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Anton Blanchard Subject: Re: [patch 2] mm: speculative get_page References: <42C0AAF8.5090700@yahoo.com.au> <20050628040608.GQ3334@holomorphy.com> <42C0D717.2080100@yahoo.com.au> <20050627.220827.21920197.davem@davemloft.net> <20050628141903.GR3334@holomorphy.com> <42C17028.6050903@yahoo.com.au> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Christoph Lameter wrote: > On Wed, 29 Jun 2005, Nick Piggin wrote: > > >>But nit picking aside, is it true that we need a load barrier before >>unlock? (store barrier I agree with) The ppc64 changeset in question >>indicates yes, but I can't quite work out why. There are noises in the >>archives about this, but I didn't pinpoint a conclusion... > > > A spinlock may be used to read a consistent set of variables. If load > operations would be moved below the spin_unlock then one may get values > that have been updated after another process acquired the spinlock. > > Of course, thanks. I was only thinking of the case where loads were moved from the unlocked into the locked section. Send instant messages to your online friends http://au.messenger.yahoo.com