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Date: Sat, 31 Mar 2007 12:40:49 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Bernhard Rosenkraenzer <bero@arklinux.org>
Cc: linux-kernel@vger.kernel.org, Dan Williams <dan.j.williams@intel.com>,
       Neil Brown <neilb@suse.de>
Subject: Re: 2.6.21-rc5-mm[12]: Oops on bootup in xor_see_2
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On Sat, 31 Mar 2007 17:36:47 +0000 Bernhard Rosenkraenzer <bero@arklinux.org> wrote:

> I'm getting this Oops when booting an 2.6.21-rc5-mm1 or 2.6.21-rc5-mm2 on an 
> Acer Aspire 1501 LMi in 32 bit mode (2.6.21-rc4-mm1 + hotfixes works 
> perfectly):
> 
> xor: automatically using best checksumming function: pIII_sse
> 
> BUG: unable to handle kernel NULL pointer dereference at virtual address 
> 00000010
> printing eip:
> c02cb724
> *pde=00000000
> Oops: 0002 [#1]
> last sysfs file:
> Modules linked in:
> CPU: 0
> EIP: 0060:[<c02cb724>] Not tainted VLI
> EFLAGS: 00010212 (2.6.12-rc5-mm2)
> EIP is at xor_sse_2+0x34/0x200
> eax: 00000010 ebx: fffea4df ecx: df8c3000 edx: df8c0000
> esi: 8005003b edi: c03ebce0 ebp: df8c3000 esp: dfd01ef8
> ds: 007b es: 007b fs: 00d8 gs: 0000 ss: 0068
> Process swapper (pid: 1, ti=dfd000000 task=c146aa10 task:ti=dfd00000
> Stack: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>        00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>        c13f1800 fffea4df 00000000 c02caa83 c03ebce0 df8c0000 00000000 c011bd7b
> Call Trace:
>   [<c02caa83>] do_xor_speed+0x53/0xf0
>   [<c011bd7b>] printk+0x1b/0x20
>   [<c02cac02>] calibrate_xor_block+0x2e/0x1b0
>   [<c03fe7a2>] kernel_init+0x92/0x1c0
>   [<c0103dee>] ret_from_fork+0x6/0x1c
>   [<c03fe710>] kernel_init+0x0/0x1c0
>   [<c03fe710>] kernel_init+0x0/0x1c0
>   [<c0104937>] kernel_thread_helper+0x7/0x10
> =======================
> Code: 44 89 74 24 48 0f 20 c6 0f 06 0f 11 04 24 0f 11 4c 24 10 0f 11 54 24 20 
> 0f
>       11 5c 24 30 0f 18 82 00 01 00 00 0f 18 82 20 01 00 00 <00> 00 00 00 00 
> 00
>       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> -

Dan, I'm assuming your changes in there are the cause of this.  AFAICT all
you're doing is moving code around, so it's a bit odd.

Bernhard, the config would be useful please.

Neil, is calibrate_xor_block() being rational?

	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
	...
	b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;

Is it correct to add BENCH_SIZE to b2 here?