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To: "Jeffrey D. Wheelhouse" <jdw@wwwi.com>
cc: freebsd-stable@freebsd.org
Subject: Re: Trap 12/supervisor read, page not present 
In-reply-to: Your message of "Mon, 17 Jun 1996 10:13:22 PDT."
             <199606171714.KAA02527@voltimand.csd.wwwi.com> 
From: David Greenman <davidg@Root.COM>
Reply-To: davidg@Root.COM
Date: Mon, 17 Jun 1996 12:05:38 -0700
Sender: owner-stable@freebsd.org
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>Ok, I'm now getting detectable panics again (two panic/dumps, one
>mystery reboot).  Seems like I've been switched to another common
>VM problem: "invalid kernel page directory".
>
>Here are the two panics and backtraces:
>kernel page directory invalid pdir=0x1beb023, va=0xefbfe000
>panic: invalid kernel page directory
>
...
>#2  0xf0192c4b in pmap_enter (pmap=0xf121f46c, va=4022329344, pa=44859392, 
>    prot=7 '\a', wired=1) at ../../i386/i386/pmap.c:1184
>#3  0xf017e2c5 in vm_fault (map=0xf121f400, vaddr=4022329344, 
>    fault_type=7 '\a', change_wiring=1) at ../../vm/vm_fault.c:840
>#4  0xf017e4d4 in vm_fault_wire (map=0xf121f400, start=4022329344, 
>    end=4022337536) at ../../vm/vm_fault.c:919
>#5  0xf0180b76 in vm_map_pageable (map=0xf121f400, start=4022329344, 
>    end=4022337536, new_pageable=0) at ../../vm/vm_map.c:1401
>#6  0xf017eda6 in vm_fork (p1=0xf12ef100, p2=0xf1335600, isvfork=0)
>    at ../../vm/vm_glue.c:227
...

    Like I said, this is a "known" problem. What I don't understand is why you
see it happen so often. It takes literally *months* of heavy system activity
for me to reproduce this sometimes, which is why it has taken so long to fix
it. We'll be looking at this problem again this week, but I can give no
guarantees that it will be fixed in the 2.1.5 release.

-DG

David Greenman
Core-team/Principal Architect, The FreeBSD Project