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Date:      Mon, 15 Mar 1999 09:49:13 +0900
From:      Kazutaka YOKOTA <yokota@zodiac.mech.utsunomiya-u.ac.jp>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        freebsd-hackers@freebsd.org, yokota@zodiac.mech.utsunomiya-u.ac.jp
Subject:   Re: FreeBSD 3.1-Stable Being Unstable 
Message-ID:  <199903150049.JAA06054@zodiac.mech.utsunomiya-u.ac.jp>
In-Reply-To: Your message of "Sun, 14 Mar 1999 11:26:24 PST." <199903141926.LAA93452@apollo.backplane.com> 
References:  <199903132253.QAA09676@isua1.iastate.edu>  <199903141926.LAA93452@apollo.backplane.com> 

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>    The vga stuff in the call stack is very suspicious.  It looks like it
>    crashed trying to start up the screen saver.
>
>    If you are using any dynamically loaded modules ( such as the splash 
>    module ), make sure you have recompiled and reinstaslled them.
>
>					-Matt
>					Matthew Dillon 
>					<dillon@backplane.com>

To be precise, the system is crashing when syscons is trying to stop
the screen saver and restore the video mode.

What I know about this crash is as follows:

The section of the code which is triggering the panic is in the vga
driver in the kernel, not in any KLD modules.

The users are seeing the problem on 486DX, P54C/133, Cyrix (I don't
know which one it is) CPUs.  (I cannot reproduce the problem on my
test bed, a dual P-Pro machine.)

The vga driver is trying to write to the BIOS data variables in the
physical memory region 0x0-0x4ff, the very first page of the physical
memory, when this panic occurs The region is supposed to be always
mapped to the beginning of the kernel memory space.

The vga driver reads from that region when initializing itself and
there is no panic at that point.

I suspect the page table entry for the above region may be corrupted
at some point.

Any comment?

Kazu



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