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Date:      Thu, 7 Mar 1996 00:17:46 +0000
From:      mark@linus.demon.co.uk (Mark Valentine)
To:        current@freebsd.org
Subject:   reproducible fatal trap 12
Message-ID:  <199603070017.AAA00301@linus.demon.co.uk>

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I can reliably reproduce a "Fatal trap 12: page fault while in kernel
mode" in a current kernel (up to date as of a few hours ago).  I reproduce
it by mounting the FreeBSD 2.1 "live file system" CD and doing some file
name completion in the Xlib source tree (using bash), e.g.

    $ more /cdrom/usr/X11R6/src/xc/lib/X11/<TAB>

The fault address on one instance was 0xf08aa001, and the fault code is
"supervisor read, page not present".  The instruction pointer is at:

    _cd9660_readdir+0x1a7: movzbl 0(%ecx),%esi

%ecx is the fault address.

I have DDB enabled if anyone wants me to poke around, but I can't get
dumps (last I tried anyway).  This is a 486DX2/66, and the CD drive is
a Toshiba XM3401B attached to an AHA1542C, if that's relevant.

Although this is the first time I've seen just this problem, I've had a
few problems recently, and the symptoms have changed over the last few
days.

For two or three weeks I've been getting a hang (in X) or silent reboot
(not in X) *only* when bringing my PPP link up or down (about once every
4-5 connections, with kernel PPP).  After some recent VM commits (Monday-ish?),
I've had a couple of "unexpected" hangs (in X), though one of them was while
playing xdoom with sound during a make world, which was asking for it...

Incidentally, on the first of these reproducible crashes (only), nvi sent
me mail dated "Mon, 6 Mar 2000 23:15:31 GMT" (which mush promptly sorted
as "very old" and marked "Jan 17" :-/ - must look into that one!).  My
clock otherwise seems fine, no manual corrections required (I run it on
local time).

		Mark.



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