Series of witness warnings from PCM

I loaded up my XFree86 4.3 / KDE 3.2.1 workstation with WITNESS today to
test some network locking changes, and got the attached set of warnings. 
Not sure if they're well-trodden ground, but my source is pretty
up-to-date, and the branch has no local changes in pcm. 

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert_at_fledge.watson.org      Senior Research Scientist, McAfee Research

...
pcm0: <CS4236> port 0x530-0x537 on acpi0
device_probe_and_attach: pcm0 attach returned 6
pcm0: <CS4236> port 0x530-0x537 on acpi0
device_probe_and_attach: pcm0 attach returned 6
pcm0: <CS4236> port 0x530-0x537 on acpi0
device_probe_and_attach: pcm0 attach returned 6
...
pcm0: <CS4236> port 0x530-0x537 on acpi0
device_probe_and_attach: pcm0 attach returned 6
pcm0: <CS4236> port 0x530-0x537 on acpi0
device_probe_and_attach: pcm0 attach returned 6
pcm0: <CS4236> port 0x530-0x537 on acpi0
device_probe_and_attach: pcm0 attach returned 6
pcm0: <CS4236> port 0x530-0x537 on acpi0
device_probe_and_attach: pcm0 attach returned 6
...
pcm0: <CS423x> at port 0x220-0x22f,0x388-0x38b,0x534-0x537 irq 5 drq 0,1 on isa0
pcm0: [GIANT-LOCKED]
...
malloc() of "256" with the following non-sleepable locks held:
exclusive sleep mutex pcm0 (sound cdev) r = 0 (0xc446ac00) locked _at_ /local0/rwatson/rwatson_netperf/sys/dev/sound/pcm/dsp.c:215
Stack backtrace:
backtrace(1,c080a8a0,c1045c00,2,dcbf28b8) at backtrace+0x12
witness_warn(5,0,c07cc264,c077a3cd) at witness_warn+0x196
uma_zalloc_arg(c1045c00,0,2) at uma_zalloc_arg+0x85
malloc(100,c080a8a0,2,c4473480,c05f5316) at malloc+0xb7
sndbuf_resize(c447b000,2,80,c4469990,dcbf2950) at sndbuf_resize+0x80
msschan_setblocksize(c4469990,c4472d94,80,c4472d94,80) at msschan_setblocksize+0x18
chn_setblocksize(c4473480,400,0,c4472d00,c4472d94) at chn_setblocksize+0x36f
chn_tryspeed(c4473480,1f40,c4472d94,0,c4473480) at chn_tryspeed+0x149
chn_tryformat(c4473480,1,0,c4473480,1f40) at chn_tryformat+0xaf
chn_setformat(c4473480,1,0,0,c4473480) at chn_setformat+0x15
chn_reset(c4473480,1,0,1,c4474000) at chn_reset+0xd4
dsp_open(c4479200,6,2000,c458ae70,c4a62000) at dsp_open+0x21f
spec_open(dcbf2a6c,dcbf2b28,c0635938,dcbf2a6c,80) at spec_open+0x2a2
spec_vnoperate(dcbf2a6c) at spec_vnoperate+0x13
vn_open_cred(dcbf2be4,dcbf2ce4,0,c4a62000,9) at vn_open_cred+0x3c0
vn_open(dcbf2be4,dcbf2ce4,0,9,c086f900) at vn_open+0x1e
kern_open(c458ae70,808c0fc,0,6,0) at kern_open+0xd8
open(c458ae70,dcbf2d14,3,26,200292) at open+0x18
syscall(2f,2f,2f,8080000,0) at syscall+0x217
Xint0x80_syscall() at Xint0x80_syscall+0x1d
--- syscall (5), eip = 0x286f72f3, esp = 0xbfbfe21c, ebp = 0xbfbfe248 ---
lock order reversal
 1st 0xc446b140 pcm0 (sound softc) _at_ /local0/rwatson/rwatson_netperf/sys/dev/sound/isa/mss.c:179
 2nd 0xc446a800 pcm0:play:0 (pcm play channel) _at_ /local0/rwatson/rwatson_netperf/sys/dev/sound/pcm/channel.c:503
Stack backtrace:
backtrace(0,ffffffff,c0938e28,c0938d60,c080c13c) at backtrace+0x12
witness_checkorder(c446a800,9,c0a6395b,1f7) at witness_checkorder+0x593
_mtx_lock_flags(c446a800,0,c0a6395b,1f7,c4472d00) at _mtx_lock_flags+0x67
chn_intr(c4473480,1097fd20,c446adc0,c197cb00,c197fd20) at chn_intr+0x1b
mss_intr(c4472d00) at mss_intr+0x7d
ithread_loop(c197cb00,d743ed48,c197cb00,c05ce64c,0) at ithread_loop+0x11c
fork_exit(c05ce64c,c197cb00,d743ed48) at fork_exit+0xa8
fork_trampoline() at fork_trampoline+0x8
--- trap 0x1, eip = 0, esp = 0xd743ed7c, ebp = 0 ---
malloc() of "256" with the following non-sleepable locks held:
exclusive sleep mutex pcm0 (sound cdev) r = 0 (0xc446ac00) locked _at_ /local0/rwatson/rwatson_netperf/sys/dev/sound/pcm/dsp.c:215
Stack backtrace:
backtrace(1,c080a8a0,c1045c00,2,dcbf28b8) at backtrace+0x12
witness_warn(5,0,c07cc264,c077a3cd) at witness_warn+0x196
uma_zalloc_arg(c1045c00,0,2) at uma_zalloc_arg+0x85
malloc(100,c080a8a0,2,c4473480,dcbf2918) at malloc+0xb7
sndbuf_resize(c447b000,2,80,c4469990,dcbf2950) at sndbuf_resize+0x80
msschan_setblocksize(c4469990,c4472d94,80,c4472d94,80) at msschan_setblocksize+0x18
chn_setblocksize(c4473480,400,0,c4472d00,c4472d94) at chn_setblocksize+0x36f
chn_tryspeed(c4473480,1f40,c4472d94,0,c4473480) at chn_tryspeed+0x149
chn_tryformat(c4473480,1,0,c4473480,1f40) at chn_tryformat+0xaf
chn_setformat(c4473480,1,0,0,c4473480) at chn_setformat+0x15
chn_reset(c4473480,1,0,1,c4474000) at chn_reset+0xd4
dsp_open(c4479200,6,2000,c458ae70,c4a62000) at dsp_open+0x21f
spec_open(dcbf2a6c,dcbf2b28,c0635938,dcbf2a6c,80) at spec_open+0x2a2
spec_vnoperate(dcbf2a6c) at spec_vnoperate+0x13
vn_open_cred(dcbf2be4,dcbf2ce4,0,c4a62000,9) at vn_open_cred+0x3c0
vn_open(dcbf2be4,dcbf2ce4,0,9,c086f900) at vn_open+0x1e
kern_open(c458ae70,808c0fc,0,6,0) at kern_open+0xd8
open(c458ae70,dcbf2d14,3,43,200292) at open+0x18
syscall(2f,2f,2f,8080000,0) at syscall+0x217
Xint0x80_syscall() at Xint0x80_syscall+0x1d
--- syscall (5), eip = 0x286f72f3, esp = 0xbfbfe21c, ebp = 0xbfbfe248 ---
malloc() of "256" with the following non-sleepable locks held:
exclusive sleep mutex pcm0 (sound cdev) r = 0 (0xc446ac00) locked _at_ /local0/rwatson/rwatson_netperf/sys/dev/sound/pcm/dsp.c:215
Stack backtrace:
backtrace(1,c080a8a0,c1045c00,2,dcbf28b8) at backtrace+0x12
witness_warn(5,0,c07cc264,c077a3cd) at witness_warn+0x196
uma_zalloc_arg(c1045c00,0,2) at uma_zalloc_arg+0x85
malloc(100,c080a8a0,2,c4473480,dcbf2918) at malloc+0xb7
sndbuf_resize(c447b000,2,80,c4469990,dcbf2950) at sndbuf_resize+0x80
msschan_setblocksize(c4469990,c4472d94,80,c4472d94,80) at msschan_setblocksize+0x18
chn_setblocksize(c4473480,400,0,c4472d00,c4472d94) at chn_setblocksize+0x36f
chn_tryspeed(c4473480,1f40,c4472d94,0,c4473480) at chn_tryspeed+0x149
chn_tryformat(c4473480,1,0,c4473480,1f40) at chn_tryformat+0xaf
chn_setformat(c4473480,1,0,0,c4473480) at chn_setformat+0x15
chn_reset(c4473480,1,0,1,c4474000) at chn_reset+0xd4
dsp_open(c4479200,6,2000,c458ae70,c4a62000) at dsp_open+0x21f
spec_open(dcbf2a6c,dcbf2b28,c0635938,dcbf2a6c,80) at spec_open+0x2a2
spec_vnoperate(dcbf2a6c) at spec_vnoperate+0x13
vn_open_cred(dcbf2be4,dcbf2ce4,0,c4a62000,9) at vn_open_cred+0x3c0
vn_open(dcbf2be4,dcbf2ce4,0,9,c086f900) at vn_open+0x1e
kern_open(c458ae70,808c0fc,0,6,0) at kern_open+0xd8
open(c458ae70,dcbf2d14,3,5d,200292) at open+0x18
syscall(2f,2f,2f,8080000,0) at syscall+0x217
Xint0x80_syscall() at Xint0x80_syscall+0x1d
--- syscall (5), eip = 0x286f72f3, esp = 0xbfbfddac, ebp = 0xbfbfddd8 ---