ng_ubt(?) related kernel panic on 6.2-PRE

[pluknet]

hi all.

i got a panic when attached and then detached the ubt0 device just
after a few seconds.
Actually, it is a built-in bluetooth device in my laptop, operated with
the Fn key.

The module was loaded via
ng_ubt_load="YES"
in loader.conf

FreeBSD notebook.h3 6.2-PRERELEASE FreeBSD 6.2-PRERELEASE #13: Wed Jan
 3 16:04:04 MSK 2007
root at notebook.h3:/usr/src/sys/i386/compile/MYKERNEL  i386

part of dmesg:
ubt0: vendor 0x413c product 0x8000, rev 2.00/12.66, addr 2
ubt0: vendor 0x413c product 0x8000, rev 2.00/12.66, addr 2
ubt0: Interface 0 endpoints: interrupt=0x81, bulk-in=0x82, bulk-out=0x2
ubt0: Interface 1 (alt.config 5) endpoints: isoc-in=0x83,
isoc-out=0x3; wMaxPacketSize=49; nframes=6, buffer size=294
...
Jan 10 22:29:44 notebook savecore: reboot after panic: page fault

kgdb bt shows:
#0  0xc04f663c in doadump ()
#1  0xc04f6bbd in boot ()
#2  0xc04f7193 in panic ()
#3  0xc0672044 in trap_fatal ()
#4  0xc06722fb in trap_pfault ()
#5  0xc06726f0 in trap ()
#6  0xc065f62a in calltrap ()
#7  0xc049ccc9 in uhci_device_bulk_start ()
#8  0xc04a72e6 in usb_transfer_complete ()
#9  0xc049c6ac in uhci_idone ()
#10 0xc049c879 in uhci_softintr ()
#11 0xc049c500 in uhci_intr1 ()
#12 0xc04dee8e in ithread_loop ()
#13 0xc04dda2d in fork_exit ()
#14 0xc065f68c in fork_trampoline ()

Since ng_ubt is a BT-USB interface, there is nothing extraordinary
in the above, i think. Though, maybe it is related to usb, not ubt.

This is the first time i got this panic. Usually (i.e. until this
time) there was no panic related to ubt0. So, probably it is not
reproduceable :(
Unfortunately, the kernel didn't have any debug options when it
occurred.

thanks.
pluknet
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