Re: Plea for help

[Micha Feigin <michf-+lLcF8/aw9x6auLlOhE+pQ@public.gmane.org>]

On Thu, Dec 18, 2003 at 11:41:13PM -0600, Ian Pilcher wrote:
> I posted a couple of weeks ago about a kernel panic that shows up when I
> boot my Abit VP6 (dual-PIII) with ACPI turned on.  It turns out that the
> kernel boots just fine with ACPI on when I build it with
> CONFIG_DEBUG_SLAB=y.
> 
> Alan Cox suggested that this is probably due to code that kmallocs
> memory and then relies on its content without clearing it, but I never
> received any response to my request for suggestions on how to identify
> the offending code.
> 
> I've just spent several hours adding printk statements to the ACPI code,
> and I've reached a point where the oops message is overwriting portions
> of my printk messages.  I have the sinking feeling that this indicates
> that the process executing the ACPI code is not the one that's oops'ing.
> 
> I'm stuck.  How can a relative newbie debug a problem like this, or at
> least gather enough information to enable someone with more expertise to
> do so?
> 

I had a brief look at what CONFIG_DEBUG_SLAB=y option does. It looks
that beside adding some debug output and sanity checks it also
initializes the memory to a non null pattern (poison something). You
could start with setting that pattern to 0x00 instead of what it is and
see if that returns your oopses (don't know where it points, but thats
probably won't do anything but could give you a null pointer access).
Otherwise I would follow the changes (it changes the DEBUG flag and
don't remember what else) and see if it changes anything (other then
the poison thing) or just read tests the results and prints error
messages. If that is the case than what you probably have is a race
condition causing some kind of timing problem.

> TIA.
> -- 
> ========================================================================
> Ian Pilcher                                        i.pilcher-Wuw85uim5zDR7s880joybQ@public.gmane.org
> ========================================================================
> 
> 
> 
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