uaudio attach panic: Giant not locked

Hi.
It's amazing how fast the FreeBSD 8 release process moves forward. Wow.

So I updated my machine to CURRENT r196062 and use a USB audio
converter. Attaching it to the machine leads to a kernel panic:

ugen7.8: <Sennheiser Communications> at usbus7
uaudio0: <Sennheiser Communications Sennheiser USB Headset, class 0/0,
rev 1.10/0.04, addr 8> on usbus7
panic: lock (sleep mutex) Giant not locked _at_
/usr/src/sys/dev/usb/usb_request.c:312
cpuid = 1
KDB: enter: panic
exclusive sx 23456789ABCDEF - USB config SX lock (23456789ABCDEF - USB
config SX lock) r = 0 (0xc69a5c3c) locked _at_
/usr/src/sys/dev/usb/usb_device.c:1237
exclusive sx newbus (newbus) r = 0 (0xc0a9ad00) locked _at_
/usr/src/sys/kern/subr_bus.c:219
exclusive sx 23456789ABCDEF - USB config SX lock (23456789ABCDEF - USB
config SX lock) r = 0 (0xc69a5c3c) locked _at_
/usr/src/sys/dev/usb/usb_device.c:1237
exclusive sx newbus (newbus) r = 0 (0xc0a9ad00) locked _at_
/usr/src/sys/kern/subr_bus.c:219
db:1:locks>  show alllocks
Process 45 (usbus7) thread 0xc6b59900 (100073)
db:0:kdb.enter.default>  show pcpu
cpuid        = 1
dynamic pcpu    = 0x57b1e12
curthread    = 0xc6b59900: pid 45 "usbus7"
curpcb       = 0xe8e99d90
fpcurthread  = none
idlethread   = 0xc6573d80: pid 10 "idle: cpu1"
APIC ID      = 1
currentldt   = 0x50
spin locks held:
db:0:kdb.enter.default>  bt
Tracing pid 45 tid 100073 td 0xc6b59900
kdb_enter(c09cc469,c09cc469,c09d2085,e8e995f8,1,...) at kdb_enter+0x3a
panic(c09d2085,c09f3eb7,c09ed67c,c09bbeff,138,...) at panic+0x136
witness_unlock(c0a896b0,8,c09bbeff,138,0,...) at witness_unlock+0xf8
_mtx_unlock_flags(c0a896b0,0,c09bbeff,138,c7a81000,...) at
_mtx_unlock_flags+0xbc
usbd_do_request_flags(c69a5c00,c0a896b0,e8e996d8,e8e996e0,0,...) at
usbd_do_request_flags+0x11c
uaudio_mixer_get(e8e99720,c05c3a60,150,c7b764a4,e8e99720,...) at
uaudio_mixer_get+0x87
uaudio_mixer_add_ctl(e8e999a4,150,102,1,c0997fc8,...) at
uaudio_mixer_add_ctl+0xbc
uaudio_attach(c7ac1c00,c681005c,c0a37ff8,c09bca92,80000000,...) at
uaudio_attach+0x1dea
device_attach(c7ac1c00,4,c09ced90,a23) at device_attach+0x3a7
device_probe_and_attach(c7ac1c00,e8e99bb8,ffffffff,c69a5c00,0,...) at
device_probe_and_attach+0x5c
usb_probe_and_attach_sub(c69a5c00,0,c09ba6a0,4d5,c0bc9ca8,...) at
usb_probe_and_attach_sub+0xde
usb_probe_and_attach(c69a5c00,ff,c6988400,2,3,...) at usb_probe_and_attach+0x1d0
uhub_explore(c6988400,ff,c6bd5400,1,1,...) at uhub_explore+0x787
uhub_explore(c6bd5400,0,c09b9b29,e3,c695dd34,...) at uhub_explore+0x7b9
usb_bus_explore(c695dd34,c695ddac,c09bbde1,67,c0a8dc80,...) at
usb_bus_explore+0x97
usb_process(c695dcd4,e8e99d38,c09c7984,33e,c6b42aa0,...) at usb_process+0xde
fork_exit(c05fc7c0,c695dcd4,e8e99d38) at fork_exit+0xb8
fork_trampoline() at fork_trampoline+0x8
--- trap 0, eip = 0, esp = 0xe8e99d70, ebp = 0 ---

...

The textdump is available here:
http://sites.google.com/site/lwfreebsd/Home/files/uaudio-panic.tar.gz?attredirects=0
If needed, I can produce a real coredump on a different machine or
provide more information.

Any ideas to solve this problem?

Lucius