panic: vm_fault: fault on nofault entry

I've been seeing the following panic for a few weeks now. It happens every
couple of days, sometimes perhaps a little more frequently.

lizzy:~/crash% uname -a
FreeBSD lizzy.catnook.local 8.0-CURRENT FreeBSD 8.0-CURRENT #0: Sun May 11
13:38:54 PDT 2008     root_at_lizzy.catnook.local:/usr/obj/usr/src/sys/LIZZY
i386
lizzy:~/crash% kgdb /usr/obj/usr/src/sys/LIZZY/kernel.debug vmcore.8
GNU gdb 6.1.1 [FreeBSD]
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This GDB was configured as "i386-marcel-freebsd"...

Unread portion of the kernel message buffer:
panic: vm_fault: fault on nofault entry, addr: c29ec000
Uptime: 2d2h21m44s
Physical memory: 1527 MB
Dumping 201 MB: 186 170 154 138 122 106 90 74 58 42 26 10

Reading symbols from /boot/kernel/linprocfs.ko...Reading symbols from /boot/kernel/linprocfs.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/linprocfs.ko
Reading symbols from /boot/kernel/linux.ko...Reading symbols from /boot/kernel/linux.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/linux.ko
Reading symbols from /boot/kernel/if_nfe.ko...Reading symbols from /boot/kernel/if_nfe.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/if_nfe.ko
Reading symbols from /boot/kernel/miibus.ko...Reading symbols from /boot/kernel/miibus.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/miibus.ko
Reading symbols from /boot/kernel/sound.ko...Reading symbols from /boot/kernel/sound.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/sound.ko
Reading symbols from /boot/kernel/snd_ich.ko...Reading symbols from /boot/kernel/snd_ich.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/snd_ich.ko
Reading symbols from /boot/kernel/tmpfs.ko...Reading symbols from /boot/kernel/tmpfs.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/tmpfs.ko
Reading symbols from /boot/kernel/daemon_saver.ko...Reading symbols from /boot/kernel/daemon_saver.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/daemon_saver.ko
#0  doadump () at pcpu.h:196
196     pcpu.h: No such file or directory.
        in pcpu.h
(kgdb) bt
#0  doadump () at pcpu.h:196
#1  0xc05486cf in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:418
#2  0xc0548947 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:572
#3  0xc064bac8 in vm_fault (map=0xc1054000, vaddr=3265183744, fault_type=Variable "fault_type" is not available.
) at /usr/src/sys/vm/vm_fault.c:277
#4  0xc06a43b7 in trap_pfault (frame=0xe6e76a40, usermode=0, eva=3265183752) at /usr/src/sys/i386/i386/trap.c:796
#5  0xc06a4ce2 in trap (frame=0xe6e76a40) at /usr/src/sys/i386/i386/trap.c:485
#6  0xc068c51b in calltrap () at /usr/src/sys/i386/i386/exception.s:146
#7  0xc0662b52 in vm_reserv_alloc_page (object=0xc4e70d00, pindex=839369) at /usr/src/sys/vm/vm_reserv.c:320
#8  0xc065c24e in vm_page_alloc (object=0xc4e70d00, pindex=839369, req=64) at /usr/src/sys/vm/vm_page.c:1066
#9  0xc064c032 in vm_fault (map=0xc4cd3674, vaddr=912048128, fault_type=2 '\002', fault_flags=Variable "fault_flags" is not available.
) at /usr/src/sys/vm/vm_fault.c:441
#10 0xc06a4349 in trap_pfault (frame=0xe6e76d38, usermode=1, eva=912049792) at /usr/src/sys/i386/i386/trap.c:784
#11 0xc06a4b42 in trap (frame=0xe6e76d38) at /usr/src/sys/i386/i386/trap.c:352
#12 0xc068c51b in calltrap () at /usr/src/sys/i386/i386/exception.s:146
#13 0x28495b6e in ?? ()
Previous frame inner to this frame (corrupt stack?)
(kgdb) 

Any idea what could be wrong?

-- 
Jos Backus
jos at catnook.com