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Date: Tue, 3 Jul 2007 08:55:09 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: 2.6.22-rc6-mm1 bad_page events.
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On Tue, 3 Jul 2007 15:06:56 +0100 Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

> X86 32bit with lots of debug turned on I get this:
> 
> 
> 
> Freeing unused kernel memory: 156k freed
> Write protecting the kernel text: 1668k
> Write protecting the kernel read-only data: 719k
> Bad page state in process 'swapper'
> page:c10000c0 flags:0x00000400 mapping:00000000 mapcount:0 count:0
> Trying to fix it up, but a reboot is needed
> Backtrace:
>  [<c024589c>] bad_page+0x6c/0x100
>  [<c024648d>] free_hot_cold_page+0x5d/0x140
>  [<c02116c2>] global_flush_tlb+0x112/0x130
>  [<c020102d>] init_post+0xd/0xe0
>  [<c047c876>] kernel_init+0x216/0x220
>  [<c0214c50>] schedule_tail+0x0/0xe0
>  [<c047c660>] kernel_init+0x0/0x220
>  [<c047c660>] kernel_init+0x0/0x220
>  [<c0204227>] kernel_thread_helper+0x7/0x10
>  =======================
> Hexdump:
> 000: 00 06 00 00 01 00 00 00 ff ff ff ff 0f 00 00 00
> 010: 00 00 00 00 00 00 00 00 78 00 00 c1 b8 00 00 c1
> 020: 00 06 00 00 01 00 00 00 ff ff ff ff a7 03 00 00
> 030: 00 00 00 00 00 00 00 00 98 00 00 c1 d8 00 00 c1
> 040: 00 04 00 00 00 00 00 00 ff ff ff ff 00 00 00 00
> 050: 00 00 00 00 00 00 00 00 b8 00 00 c1 f8 00 00 c1
> 060: 00 06 00 00 01 00 00 00 ff ff ff ff 00 04 00 00
> 070: 00 00 00 00 00 00 00 00 d8 00 00 c1 18 01 00 c1
> 080: 00 06 00 00 01 00 00 00 ff ff ff ff 9c 03 00 00
> 090: 00 00 00 00 00 00 00 00 f8 00 00 c1 38 01 00 c1
> 0a0: 00 06 00 00 01 00 00 00 ff ff ff ff 00 04 00 00
> 0b0: 00 00 00 00 00 00 00 00 18 01 00 c1 58 01 00 c1

Wow, freeing lots of PageReserved() pages.  I assume via free_initmem(),
but it's strange that free_initmem() makes no appearance in the backtrace.

I don't know which change could have caused this.  Nobody else has reported
this, but 32-on-64 might be pretty rare.  If you can send the config I'll
see if it happens here?