LOR in pcm

lock order reversal
  1st 0xc2459380 pcm0:play:0 (pcm channel) _at_ 
/usr/src/sys/dev/sound/pcm/sound.c:191
  2nd 0xc2459500 pcm0 (sound cdev) _at_ /usr/src/sys/dev/sound/pcm/sound.c:163
Stack backtrace:
backtrace(c0397dd3,c2459500,c2433310,c038ab91,c038a9fc) atbacktrace+0x17
witness_lock(c2459500,8,c038a9fc,a3,1f40) at witness_lock+0x697
_mtx_lock_flags(c2459500,0,c038a9fc,a3,d1c6f978) at _mtx_lock_flags+0xb1
pcm_lock(c2441400,8,2b3,ffffffff,8) at pcm_lock+0x2c
dsp_open(c040a120,6,2000,c282f130,c03d0cc0) at dsp_open+0x2b0
spec_open(d1c6fa44,d1c6fae0,c027053a,d1c6fa44,c0417860) at spec_open+0x28b
spec_vnoperate(d1c6fa44,c0417860,0,80,c282f130) at spec_vnoperate+0x18
vn_open_cred(d1c6fbd8,d1c6fcd8,0,c33e3b80,d1c6fcc4) at vn_open_cred+0x3fa
vn_open(d1c6fbd8,d1c6fcd8,0,2ab,c04113a0) at vn_open+0x29
kern_open(c282f130,2807737a,0,6,0) at kern_open+0x13d
open(c282f130,d1c6fd10,c03ab60e,3fb,3) at open+0x30
syscall(bfbf002f,2806002f,bfbf002f,804faf3,2807737a) at syscall+0x26e
Xint0x80_syscall() at Xint0x80_syscall+0x1d
--- syscall (5), eip = 0x28108b6b, esp = 0xbfbff8bc, ebp = 0xbfbff8e8 ---

flo