linux-kernel - Re: [PATCH 00 of 11] x86: separate pmd lifetime from pgd

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Date:	Mon, 28 Jan 2008 16:41:40 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Andi Kleen <ak@...e.de>,
	Jan Beulich <jbeulich@...ell.com>,
	Eduardo Pereira Habkost <ehabkost@...hat.com>,
	Ian Campbell <ijc@...lion.org.uk>,
	H Peter Anvin <hpa@...or.com>
Subject: Re: [PATCH 00 of 11] x86: separate pmd lifetime from pgd


* Ingo Molnar <mingo@...e.hu> wrote:

> hm, i tried this, and got an early crash:
> 
> [   29.389844] VFS: Mounted root (ext3 filesystem) readonly.
> [   29.389872] debug: unmapping init memory c0b03000..c0b6f000
> [   29.440139] PM: Adding info for No Bus:vcs1
> [   29.463676] khelper used greatest stack depth: 2404 bytes left
> [   29.467238] PM: Adding info for No Bus:vcsa1
> [   29.541785] PANIC: double fault, gdt at c1d16000 [255 bytes]
> [   29.541785] double fault, tss at c1d19100
> [   29.541785] eip = c011fa95, esp = c3bf6000
> [   29.541785] eax = c3bf6010, ebx = c0b6fc08, ecx = 0000007b, edx = 00000000
> [   29.541785] esi = f76a7df4, edi = c011fa90
> 
> i think it's one of your patches :) Bisecting it down to the right one 
> now. Config attached.

and after a session of bisection, the winner patch is:

  Subject: x86: unify PAE/non-PAE pgd_ctor

which is a tad unexpected, given the relatively harmless nature of the 
patch. (but then again, nothing is really harmless in PAE land.)

btw., this is not fair i think: your patch was apparently caught by the 
new debugging helper that tells about itself here:

> [   29.389872] debug: unmapping init memory c0b03000..c0b6f000

note the close proximity of c0b6f000 and ebx = c0b6fc08. [ I regularly 
come up with such nasty tricks and debugging helpers like that to catch 
bad patches off-guard. You have been warned! ;-) ]

	Ingo
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