panic: _mtx_lock_sleep: recursed on non-recursive mutex sbc0 _at_ ../../../dev/sound/isa/sbc.c:131

For at least the last week's worth of kernels I've been getting the
following panic whenever I try and write to /dev/dsp.  It may have been
broken longer, but I don't usually use the soundcard on this machine. 
I triggered this one with with a simple "echo hi > /dev/dsp":

panic messages:
---
panic: _mtx_lock_sleep: recursed on non-recursive mutex sbc0 _at_ ../../../dev/sound/isa/sbc.c:131

(kgdb) where
#0  doadump () at machine/pcpu.h:159
#1  0xc052bfb5 in boot (howto=260) at ../../../kern/kern_shutdown.c:399
#2  0xc052c2af in panic () at ../../../kern/kern_shutdown.c:561
#3  0xc0524347 in _mtx_lock_sleep (m=0xc142c200, td=0xc1572c60, opts=0,
    file=0xc06a8d73 "../../../dev/sound/isa/sbc.c", line=131)
    at ../../../kern/kern_mutex.c:482
#4  0xc0523caa in _mtx_lock_flags (m=0xc142c200, opts=0,
    file=0xc06a8d73 "../../../dev/sound/isa/sbc.c", line=131)
    at ../../../kern/kern_mutex.c:253
#5  0xc04c87fa in sbc_lock (scp=0x0) at ../../../dev/sound/isa/sbc.c:131
#6  0xc04c774a in sb_lock (sb=0x0) at ../../../dev/sound/isa/sb16.c:123
#7  0xc04c78d6 in sb_cmd2 (sb=0xc1395a00, cmd=0 '\0', val=127)
    at ../../../dev/sound/isa/sb16.c:212
#8  0xc04c81e7 in sb_setup (sb=0xc1395a00) at ../../../dev/sound/isa/sb16.c:630
#9  0xc04c8388 in sb16chan_trigger (obj=0xc1422860, data=0xc1395a2c, go=0)
    at ../../../dev/sound/isa/sb16.c:727
#10 0xc04ccea2 in chn_trigger (c=0x1, go=1) at channel_if.h:100
#11 0xc04cbd67 in chn_start (c=0xc13aa500, force=1)
    at ../../../dev/sound/pcm/channel.c:543
#12 0xc04cbf9e in chn_flush (c=0xc13aa500)
    at ../../../dev/sound/pcm/channel.c:673
#13 0xc04cdb45 in dsp_close (i_dev=0xc1397500, flags=2, mode=8192,
    td=0xc1572c60) at ../../../dev/sound/pcm/dsp.c:379
#14 0xc04fa16f in spec_close (ap=0xcc201b70)
    at ../../../fs/specfs/spec_vnops.c:637
#15 0xc04f9293 in spec_vnoperate (ap=0x0)
    at ../../../fs/specfs/spec_vnops.c:118
#16 0xc0582942 in vn_close (vp=0xc18c1240, flags=2, file_cred=0xc1865180,
    td=0xc1572c60) at vnode_if.h:262
#17 0xc0583ad6 in vn_closefile (fp=0xc1558990, td=0xc1572c60)
    at ../../../kern/vfs_vnops.c:949
#18 0xc0511857 in fdrop_locked (fp=0xc1558990, td=0xc1572c60)
    at ../../../sys/file.h:289
#19 0xc0510be0 in fdrop (fp=0xc1558990, td=0xc1572c60)
    at ../../../kern/kern_descrip.c:1910
#20 0xc0510bb3 in closef (fp=0xc1558990, td=0xc1572c60)
    at ../../../kern/kern_descrip.c:1896
#21 0xc050ec20 in do_dup (td=0xc1572c60, type=DUP_FIXED, old=11, new=1,
    retval=0xc1572d74) at ../../../kern/kern_descrip.c:700
#22 0xc050dde5 in dup2 (td=0x0, uap=0x0) at ../../../kern/kern_descrip.c:255
#23 0xc06670bf in syscall (frame=
      {tf_fs = 134676527, tf_es = -1078001617, tf_ds = -1078001617, tf_edi = 1,
tf_esi = 672130312, tf_ebp = -1077941624, tf_isp = -870310540, tf_ebx = 67210923
6, tf_edx = 0, tf_ecx = 673317580, tf_eax = 90, tf_trapno = 12, tf_err = 2, tf_e
ip = 672806431, tf_cs = 31, tf_eflags = 643, tf_esp = -1077941652, tf_ss = 47})
    at ../../../i386/i386/trap.c:1004
#24 0xc0657e5f in Xint0x80_syscall () at {standard input}:137
---Can't read userspace from dump, or kernel process---

-- 
	Dan Nelson
	dnelson_at_allantgroup.com