From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756645Ab2CBF51 (ORCPT ); Fri, 2 Mar 2012 00:57:27 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:58870 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755693Ab2CBF50 (ORCPT ); Fri, 2 Mar 2012 00:57:26 -0500 Date: Thu, 1 Mar 2012 23:57:16 -0600 From: Jonathan Nieder To: Dan Williams Cc: Thomas Goirand , Konrad Rzeszutek Wilk , xen-devel@lists.xensource.com, William Dauchy , Maciej Sosnowski , pkg-xen-devel@lists.alioth.debian.org, linux-kernel@vger.kernel.org Subject: Re: ioatdma: Boot process hangs then reboots when using Xen + Linux 3.2 Message-ID: <20120302055715.GA692@burratino> References: <20120127144737.GA27750@andromeda.dapyr.net> <20120219223125.GA820@burratino> <20120220181618.GD17566@burratino> <4F4891B8.9050008@goirand.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4F4891B8.9050008@goirand.fr> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Dan, Thomas and William (cc-ed) have been having trouble loading the ioatdma driver on a 32-bit Xen dom0. The module loads automatically at boot time and trips BUG_ON(active && !seen_current); /* no active descs have written a completion? */ from drivers/dma/ioat/dma_v2.c. That check has been present since 5cbafa65b92e (ioat2,3: convert to a true ring buffer, 2009-08-26). The bug is probably in Xen code and seems to be a regression (the bug is present in 3.2 but not 3.1.8). Thomas Goirand wrote: > On 03/01/2012 11:53 PM, Bastian Blank wrote: >> On Thu, Mar 01, 2012 at 06:02:15PM +0800, Thomas Goirand wrote: >>> Any clue why I don't see crashes without Xen, with a >>> 64 bits kernel, or with earlier versions of Linux (eg: 3.1 for example)? >> >> xen/i386 uses a different memory model to anything else, this may be a >> problem. [...] > Replacing BUG_ON by a WARN_ON, and adding #define DEBUG 1 on top of > dma_v2.c, my kernel booted, and I had the attached dmesg output. > > Blacklisting the ioatdma kernel module of course, solved the issue. > > I hope that helps, please let me know if I should do more to help. If > you need access to my server, that's possible (I use it only for > packaging XCP and some tests...). I don't expect you to debug this Xen-specific bug, but I'm wondering: is there any reason this check has to be a BUG_ON instead of a WARN_ON? If there is some way to recover when the impossible happens, that would make using and debugging the kernel a little easier. Curious, Jonathan