Recent update to sys/dev/audio.c causes hangs?

[Tom Ivar Helbekkmo <tih%hamartun.priv.no@localhost>]

I've just updated my i386-current, and am experiencing hangs using a USB
audio device (aka external sound card).  I use mplayer, and it happily
outputs sound through the device, but when I quit mplayer, the system
hangs, and needs to be reset.

My previous 'cvs update' was somewhere around the end of March or
beginning or April, and this problem was introduced when I updated on
April 10.  The obvious suspect is mrg's update to sys/dev/audio.c on
April 6, which changed a few mutex_enter() and mutex_exit() calls.  My
intuition says these changes need some sort of compensating change in
sys/dev/usb/uaduio.c.

-tih
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