Date: Thu, 12 Oct 2006 14:06:44 -0700
From: Randy Dunlap <rdunlap@xenotime.net>
To: Edward Goggin <egoggin@emc.com>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: looking for explanation of spontaneous reset/reboot on Opteron
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On Thu, 12 Oct 2006 13:43:15 -0400 Edward Goggin wrote:

> I'm looking for information about potential causes for a
> spontaneous reboot of a dual core Opteron running RHEL 4
> linux (2.6.9 derivative).  I'm thinking the cause is
> due to the box taking a triple fault and resetting the
> BIOS.
> 
> I'm also thinking that the triple fault is caused by a
> kernel stack overflow into an unmapped virtual page
> frame.  Is this a reasonable explanation?  Are there
> others?
> 
> What are reasonable debugging strategies for handling
> this?  Following the kernel stack overflow hunch, I'm
> going to try increasing the Opteron stack size from
> 8K to 16K.  Can this be done by simply changing
> THREAD_ORDER in include/asm-x86_64/page.h from 1 to 2?
> 
> Also, is there any kernel stack overflow detection
> debugging code anywhere for x86_64 as there is for
> i386?

[Please start a new thread instead of replying to a diff.
one and changing the subject.]

arch/x86_64/Kconfig.debug has these Kernel hacking options:
[but I'm not talking about 2.6.9; maybe you should/could try
a newer kernel]

config DEBUG_STACKOVERFLOW
        bool "Check for stack overflows"
        depends on DEBUG_KERNEL
        help
	  This option will cause messages to be printed if free stack space
	  drops below a certain limit.

config DEBUG_STACK_USAGE
        bool "Stack utilization instrumentation"
        depends on DEBUG_KERNEL
        help
	  Enables the display of the minimum amount of free stack which each
	  task has ever had available in the sysrq-T and sysrq-P debug output.

	  This option will slow down process creation somewhat.


---
~Randy
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