linux-kernel - Re: [pre-2.6.23 REGRESSION] 2.6.23-rc3-git1 crash/stuck on VIA CN700 system

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Date:	Wed, 05 Sep 2007 18:39:53 +0300
From:	Stefan Becker <Stefan.Becker@...ia.com>
To:	ext Andi Kleen <andi@...stfloor.org>,
	ext Michal Piotrowski <michal.k.k.piotrowski@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [pre-2.6.23 REGRESSION] 2.6.23-rc3-git1 crash/stuck on VIA CN700
 system

Hi,

ext Andi Kleen wrote:
>>> Please report for mainline kernels.
>> I compiled a vanilla 2.6.23-rc5 kernel. Same problem. Still no sensible 
>> debug information though...
> 
> Thanks. If you can easily reproduce it would it be possible to 
> do a git bisect to track down which change caused it? 
> See http://kerneltrap.org/node/11753 on how to do that.

Thanks for the pointer! It was very educational to see "git bisect" in 
action. Luckily I was able to reproduce the problem with defconfig so I 
could cut down the compilation/turnaround times drastically...

It turned out it was one of your changes:

------------------------------------------------------------------
19d36ccdc34f5ed444f8a6af0cbfdb6790eb1177 is first bad commit
commit 19d36ccdc34f5ed444f8a6af0cbfdb6790eb1177
Author: Andi Kleen <ak@...e.de>
Date:   Sun Jul 22 11:12:31 2007 +0200

     x86: Fix alternatives and kprobes to remap write-protected kernel text

     Reenable kprobes and alternative patching when the kernel text is write
     protected by DEBUG_RODATA

     Add a general utility function to change write protected text.  The new
     function remaps the code using vmap to write it and takes care of CPU
     synchronization.  It also does CLFLUSH to make icache recovery faster.

     There are some limitations on when the function can be used, see the
     comment.

     This is a newer version that also changes the paravirt_ops code.
     text_poke also supports multi byte patching now.

     Contains bug fixes from Zach Amsden and suggestions from Mathieu
     Desnoyers.

     Cc: Jan Beulich <jbeulich@...ell.com>
     Cc: Jeremy Fitzhardinge <jeremy@...p.org>
     Cc: Mathieu Desnoyers <compudj@...stal.dyndns.org>
     Cc: Zach Amsden <zach@...are.com>
     Signed-off-by: Andi Kleen <ak@...e.de>
     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

:040000 040000 06016fc7661dcdc27a961c9d0b7fe0435bbf2fa4 
1ffc495539fa0a055fbbf60d6aac8c8947e77c7d M      arch
:040000 040000 78d8f7a43090fdf2f3441532ba77eff5e9697780 
b7992c48781270f409adce6b71885fba489cd45f M      include
------------------------------------------------------------------


I thought the output of /proc/cpuinfo from the box might be helpful as 
this looks like something CPU-type related:

processor	: 0
vendor_id	: CentaurHauls
cpu family	: 6
model		: 10
model name	: VIA Esther processor 1200MHz
stepping	: 9
cpu MHz		: 1197.072
cache size	: 128 KB
fdiv_bug	: no
hlt_bug		: no
f00f_bug	: no
coma_bug	: no
fpu		: yes
fpu_exception	: yes
cpuid level	: 1
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic mtrr pge cmov pat 
clflush acpi mmx fxsr sse sse2 tm up pni est tm2 rng rng_en ace ace_en 
ace2 ace2_en phe phe_en pmm pmm_en
bogomips	: 2396.03
clflush size	: 64


Regards,

	Stefan

---
Stefan Becker
E-Mail: Stefan.Becker@...ia.com

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