panic: _sx_xlock_hard: recursed on non-recursive sx newbus

Hiho! :-)

While loading snd_hda for fun on my fileserver, I got the following
panic (crashdump available for poking around):

panic: _sx_xlock_hard: recursed on non-recursive sx newbus
_at_ /usr/src/sys/kern/subr_bus.c:219

Backtrace is attached.

Bye
Marc