linux-kernel - Re: UML kernel failed to start betvee 2.6.8-rc8 and current git sources

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Date:	Fri, 11 Jul 2008 10:43:32 +0200
From:	Toralf Förster <toralf.foerster@....de>
To:	Jeff Dike <jdike@...toit.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	uml-devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: Re: UML kernel failed to start betvee 2.6.8-rc8 and current git sources

At Thursday 10 July 2008 21:30:19 Jeff Dike wrote :
> On Thu, Jul 10, 2008 at 08:09:59PM +0200, Toralf Förster wrote:
> > At Thursday 10 July 2008 18:35:15 Jeff Dike wrote :
> > 
> > > What's the host?
> > 
> > tfoerste@n22 ~ $ uname -a
> > Linux n22 2.6.25-gentoo-r6 #4 Thu Jul 10 19:49:36 CEST 2008 i686 Intel(R) Pentium(R) M processor 1700MHz GenuineIntel GNU/Linux
> > 
> > BTW,  this works fine and shows only the config :
> > n22 ~ # linux-v2.6.26-rc8-227 --showconfig 
> > 
> > whereas this failed:
> > 
> > n22 ~ # linux-v2.6.26-rc9-56 --showconfig
> > Locating the bottom of the address space ... 0x0
> > Locating the top of the address space ... 0xc0000000
> 
> OK, I believe you're seeing the same bug as Uli saw here:
> 
>     http://marc.info/?l=linux-kernel&m=121011518003727&w=2
> 
> More precise symptoms are here:
> 
>      http://marc.info/?l=linux-kernel&m=121011722806093&w=2
> 
> I never did figure that one out.  I had the same kernel version, same
> toolchain, same everything as far as I could see, and I couldn't
> reproduce it, except with a binary that he gave me.
> 
> You're seeing it on i386, whereas he saw it on x86_64.
> 
> The underlying problem is that somehow the UML initcalls aren't being
> run, which is why you're seeing all zeros in the register dump.
> 
> If you bisect this, I bet you end up at the no-unit-at-a-time patch
> that he ended up at.  And I have no idea what that has to do with
> anything.
> 
You're right :

tfoerste@n22 ~/devel/linux-2.6 $ git bisect good
4f81c5350b44bcc501ab6f8a089b16d064b4d2f6 is first bad commit
commit 4f81c5350b44bcc501ab6f8a089b16d064b4d2f6
Author: Jeff Dike <jdike@...toit.com>
Date:   Mon Jul 7 13:36:56 2008 -0400

    [UML] fix gcc ICEs and unresolved externs

    There are various constraints on the use of unit-at-a-time:
     - i386 uses no-unit-at-a-time for pre-4.0 (not 4.3)
     - x86_64 uses unit-at-a-time always

...


-- 
MfG/Sincerely

Toralf Förster
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