kern/46232: netbsd-6 pad(4) panic: locking against myself

[Matthew Mondor <mm_lists%pulsar-zone.net@localhost>]

>Number:         46232
>Category:       kern
>Synopsis:       netbsd-6 pad(4) panic: locking against myself
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Mar 20 17:05:01 +0000 2012
>Originator:     Matthew Mondor
>Release:        NetBSD 6.0_BETA
>Organization:
>Environment:
System: NetBSD ninja.xisop 6.0_BETA NetBSD 6.0_BETA (GENERIC_MM) #2: Tue Mar 20 
12:14:05 EDT 2012 root@ninja.xisop:/usr/obj/sys/arch/amd64/compile/GENERIC_MM 
amd64
Architecture: x86_64
Machine: amd64
>Description:

I can reliably reproduce a pad(4) panic.

Mutex error: mutex_vector_enter: locking against myself
        wait/spin: 0/0

...
lockdebug_abort()
mutex_vector_enter()
audio_clear()
audio_pint()
pad_read()
spec_read()
VOP_READ()
vn_read()
dofileread()
sys_read()
syscall()

BTW, must I do something special for ddb to do VGA_POST?  The kernel
was built with support for it, but if within X11 I can't see ddb
entering.  I had crash dumps enabled because of that instead, but I
wasn't patient enough to wait for the long dump to finish...

>How-To-Repeat:

Shell 1:

$ audioplay -d /dev/sound1 foo.wav

Shall 2:

$ dd if=/dev/pad0 of=foo.pcm

>Fix: