panic: mutex vm object not owned

[Gavin Atkinson]

Hi,

I'm tracking RELENG_5 and since my last update I can no longer start X
without getting the following panic:

panic: mutex vm object not owned at /usr/src/sys/vm/vm_page.c:334
cpuid = 0
KDB: enter: panic
[ thread pid 2762 tid 100116 ]
stopped at         kdb_enter+0x2b:   nop

At which point the machine hangs solid (note this is over a serial console
- it is after X has claimed the display).

I've done a binary chop to find where the bug was introduced, and it
started at some point between 19:00 on 2005/02/25 and 00:00 on 2005/02/26.
The MFC to vm_page.c which added the assertion I'm tripping up on happened
between those two points:
$FreeBSD: src/sys/vm/vm_page.c,v 1.290.2.4 2005/02/25 23:38:22 alc Exp $

vm_page.c:334 seems to correspond to the line
    VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
within vm_page_wakeup()

Any suggestions?  I'll try to coerce it into generating a backtrace but
given the machine wedges before even giving the DDB prompt I'm not sure
I'll be able to.

Thanks,

Gavin