From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner+w=401wt.eu-S1758755AbYG1Pxd@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1758755AbYG1Pxd (ORCPT <rfc822;w@1wt.eu>);
	Mon, 28 Jul 2008 11:53:33 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755450AbYG1PxO
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Mon, 28 Jul 2008 11:53:14 -0400
Received: from mx2.mail.elte.hu ([157.181.151.9]:53192 "EHLO mx2.mail.elte.hu"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1754914AbYG1PxN (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Mon, 28 Jul 2008 11:53:13 -0400
Date: Mon, 28 Jul 2008 17:52:48 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Mike Travis <travis@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Hugh Dickins <hugh@veritas.com>, Jack Steiner <steiner@sgi.com>,
       Jeremy Fitzhardinge <jeremy@goop.org>, "H. Peter Anvin" <hpa@zytor.com>,
       linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>
Subject: [crash] Re: [PATCH 0/4] x86_64: Optimize percpu accesses
Message-ID: <20080728155248.GA7123@elte.hu>
References: <20080725211117.586723000@polaris-admin.engr.sgi.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20080725211117.586723000@polaris-admin.engr.sgi.com>
User-Agent: Mutt/1.5.18 (2008-05-17)
X-ELTE-VirusStatus: clean
X-ELTE-SpamScore: -1.5
X-ELTE-SpamLevel: 
X-ELTE-SpamCheck: no
X-ELTE-SpamVersion: ELTE 2.0 
X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3
	-1.5 BAYES_00               BODY: Bayesian spam probability is 0 to 1%
	[score: 0.0000]
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


ok, i have integrated tip/x86/percpu-zerobased into tip/master briefly, 
but it blew up almost immediately in testing, on two boxes.

one bad config is:

  http://redhat.com/~mingo/misc/config-Mon_Jul_28_17_35_00_CEST_2008.bad

failure pattern: it booted up fine to userspace and seemed function, but 
then produced a spontaneous reboot while building a kernel, without any 
log entries.

other bad config is:

  http://redhat.com/~mingo/misc/config-Mon_Jul_28_17_30_39_CEST_2008.bad

failure pattern: early crash at:

  PANIC: early exception 0e rip 10:fffffff817dfc1a error 0 cr2 28

which corresponds to:

ffffffff817dfc0f <machine_specific_memory_setup>:
ffffffff817dfc0f:       48 8b 05 aa cf 04 00    mov    315306(%rip),%rax
# ffffffff8182cbc0 <x86_quirks>
ffffffff817dfc16:       55                      push   %rbp
ffffffff817dfc17:       48 89 e5                mov    %rsp,%rbp
ffffffff817dfc1a:       48 8b 40 28             mov    0x28(%rax),%rax  [*]
ffffffff817dfc1e:       48 85 c0                test   %rax,%rax

i.e. RAX was zero.

i've pushed out the tip/tmp.x86/percpu-zerobased.bad branch which shows 
the exact kernel that failed. It was generated by:

 git-checkout tip/master
 git-merge tip/x86/percpu-zerobased

	Ingo