kern/55130: audio sometimes plays a buzz sound for a few seconds when changing volume

[coypu%sdf.org@localhost]

>Number:         55130
>Category:       kern
>Synopsis:       audio sometimes plays a buzz sound for a few seconds when changing volume
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Apr 01 20:35:00 +0000 2020
>Originator:     coypu
>Release:        NetBSD 9.99.51
>Organization:
>Environment:
NetBSD planets 9.99.51 NetBSD 9.99.51 (GENERIC) #0: Tue Mar 24 22:28:54 IST 2020  fly@planets:/cvs/obj/sys/arch/amd64/compile/GENERIC amd64

>Description:
I change audio volume a lot out of habit (I have a key binding for it) with mixerctl. Every so often it wedges and plays a buzzing sound.
Changing the audio latency made it more likely to reproduce.

My dmesg has a lot of:

[ 10743.902726] audio0: device timeout
[ 10746.904582] audio0: device timeout
[ 10853.640570] audio0: device timeout
[ 10856.642426] audio0: device timeout
[ 10859.644281] audio0: device timeout
[ 13810.378515] audio0: device timeout

mlelstv has suggested that perhaps the cv_broadcast happens before cv_timedwait_sig.
>How-To-Repeat:

>Fix: