kern/45927: panic: kernel diagnostic assertion "sc->sc_dvlock < 0" failed

[nonakap%gmail.com@localhost]

>Number:         45927
>Category:       kern
>Synopsis:       panic: kernel diagnostic assertion "sc->sc_dvlock < 0" failed
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Feb 05 01:10:00 +0000 2012
>Originator:     NONAKA Kimihiro
>Release:        5.99.64
>Organization:
>Environment:
NetBSD koharu.myhome.local 5.99.64 NetBSD 5.99.64 (TPX201) #1796: Sun Feb  5 
08:59:11 JST 2012  
root@koharu.myhome.local:/usr/obj.i386/sys/arch/i386/compile/TPX201 i386
>Description:
panic: kernel diagnostic assertion "sc->sc_dvlock < 0" failed: file 
"/usr/src/sys/dev/audio.c", line 2681 

>How-To-Repeat:
I think that happens if you mmap the audio device.

For example, this problem occurs in my environment, when you launch a Xnp2 have 
enabled the SDL_mixer.
cd xnp2-20120204/x11 && configure && make && ./xnp2
# Xnp2: http://www.asahi-net.or.jp/~aw9k-nnk/np2/xnp2-20120204.tar.bz2

>Fix: