From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765033AbXF1Twl (ORCPT ); Thu, 28 Jun 2007 15:52:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759206AbXF1Twd (ORCPT ); Thu, 28 Jun 2007 15:52:33 -0400 Received: from mx1.redhat.com ([66.187.233.31]:35854 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760123AbXF1Twc (ORCPT ); Thu, 28 Jun 2007 15:52:32 -0400 Message-ID: <46841175.8070901@redhat.com> Date: Thu, 28 Jun 2007 15:52:21 -0400 From: Chuck Ebbert Organization: Red Hat User-Agent: Thunderbird 1.5.0.12 (X11/20070530) MIME-Version: 1.0 To: Andi Kleen CC: Loic Prylli , linux-kernel@vger.kernel.org Subject: Re: [PATCH] MTRR: Fix race causing set_mtrr to go into infinite loop References: <468035BC.9080008@myri.com> <46803C1D.2040009@redhat.com> <200706260034.41940.ak@suse.de> In-Reply-To: <200706260034.41940.ak@suse.de> Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 06/25/2007 06:34 PM, Andi Kleen wrote: > On Tuesday 26 June 2007 00:05:17 Chuck Ebbert wrote: >> On 06/25/2007 05:38 PM, Loic Prylli wrote: >> >> [cc: Andi] >> >>> Processors synchronization in set_mtrr requires the .gate field >>> to be set after .count field is properly initialized. Without an explicit >>> barrier, the compiler was reordering those memory stores. That was sometimes >>> causing a processor (in ipi_handler) to see the .gate change and >>> decrement .count before the latter is set by set_mtrr() (which >>> then hangs in a infinite loop with irqs disabled). > > Hmm, perhaps we should just put the smp_wmb into atomic_set(). > Near all other atomic operations have memory barriers too. I think > that would be the better fix. Can we get something merged before 2.6.22-final? The original patch seems okay...