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Date: Thu, 21 Sep 2006 17:41:34 -0700
From: Andrew Morton <akpm@osdl.org>
To: kmannth@us.ibm.com
Cc: lkml <linux-kernel@vger.kernel.org>,
       Christoph Lameter <clameter@engr.sgi.com>
Subject: Re: [BUG] i386 2.6.18 cpu_up: attempt to bring up CPU 4 failed :
 kernel BUG at mm/slab.c:2698!
Message-Id: <20060921174134.4e0d30f2.akpm@osdl.org>
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On Thu, 21 Sep 2006 17:17:31 -0700
keith mannthey <kmannth@us.ibm.com> wrote:

> I wanted to just give 2.6.18 a spin and I tripped over something I
> didn't expect. 
> 
> 
> cpu_up: attempt to bring up CPU 4 failed
> kfree_debugcheck: bad ptr c15f6000h.
> ------------[ cut here ]------------
> kernel BUG at mm/slab.c:2698!
> invalid opcode: 0000 [#1]
> SMP
> Modules linked in:
> CPU:    0
> EIP:    0060:[<c106ce51>]    Not tainted VLI
> EFLAGS: 00010046   (2.6.18 #1)
> EIP is at kfree_debugcheck+0x7f/0x90
> eax: 00000028   ebx: 000015f6   ecx: c1025289   edx: c7653540
> esi: c15f6000   edi: c15f6000   ebp: c764af38   esp: c764af28
> ds: 007b   es: 007b   ss: 0068
> Process swapper (pid: 1, ti=c764a000 task=c7653540 task.ti=c764a000)
> Stack: c122c68d c15f6000 c1635000 00000004 c764af5c c106ef93 00000286
> c76a77d0
>        00000004 00000001 c1635000 00000004 00000004 c764af6c c10557f6
> c1274eac
>        c12743dc c764af84 c1207467 00000004 c12734c0 00000004 00000004
> c764af98
> Call Trace:
>  [<c106ef93>] kfree+0x24/0x1d8
>  [<c10557f6>] pageset_cpuup_callback+0x40/0x58
>  [<c1207467>] notifier_call_chain+0x20/0x31
>  [<c1031530>] blocking_notifier_call_chain+0x1d/0x2d
>  [<c103f80c>] cpu_up+0xb5/0xcf
>  [<c1000372>] init+0x78/0x296
>  [<c1002005>] kernel_thread_helper+0x5/0xb

I think we have two problems here:

a) CPU4 didn't come up.  To diagnose that I think we'll need to ask you
   to into cpu_up(), add debug printks to blocking_notifier_call_chain(),
   work out which entry on that chain returned NOTIFY_BAD, then work out
   why it did so.

b) pageset_cpuup_callback()'s CPU_UP_CANCELED path possibly hasn't been
   tested before.  I'd be guessing that we're not zeroing out the
   zone.pageset[] array when the `struct zone' is first allocated, but I
   don't immediately recall where that code lives.


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