From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1767310AbXDEVDq (ORCPT ); Thu, 5 Apr 2007 17:03:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1767311AbXDEVDq (ORCPT ); Thu, 5 Apr 2007 17:03:46 -0400 Received: from ns1.suse.de ([195.135.220.2]:57012 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1767310AbXDEVDp (ORCPT ); Thu, 5 Apr 2007 17:03:45 -0400 From: Andi Kleen Organization: SUSE Linux Products GmbH, Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg) To: Jeremy Fitzhardinge Subject: Re: What protects cpu_tlbstate? Date: Thu, 5 Apr 2007 23:03:35 +0200 User-Agent: KMail/1.9.6 Cc: Benjamin LaHaise , Ingo Molnar , Linux Kernel Mailing List References: <4615518A.4070003@goop.org> <200704052228.36590.ak@suse.de> <46156366.70206@goop.org> In-Reply-To: <46156366.70206@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200704052303.35846.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 05 April 2007 23:00:22 Jeremy Fitzhardinge wrote: > Andi Kleen wrote: > > The interrupts can only happen when the other CPU is already lazy > > and enter_lazy_tlb would be a nop then. The flushers itself are > > synchronized by the page_table_lock or the mm semaphore. > > > > Against switch_mm it tries to protect with ordering. > > > > wmb()s are not needed on x86 (ok minus errata on ppro and > > VIA magic mode but which is UP only). That would leave some rmb()s, > > but I don't see any place they would be needed. > > > > Hm, I was more wondering about simple compiler reordering. Does the > relative order of setting and reading cpu_tlbstate.state, active_mm and > the mm->cpu_vm_mask matter? Hmm, perhaps a barrier between state and active_mm might be a good idea. Setting active_mm after state might be problematic. cpu_vm_mask should be already a memory barrier. -Andi