uaudio: pulseaudio locks up system

[Stefan Ehmann]

FreeBSD locks up when my USB audio interface is connected and accessed via
pulseudio.

The interface is connected via USB hub.
Symptoms: First USB mouse (on same hub) stops working. System becomes
increasingly unresponsive until it totally locks up.

I can reproduce the problem by simply running pactl list

If I reboot immediately, shutdown also hangs. Kernel debugger shows this
suspicious trace (transcribed by hand):

__mtx_lock_sleep()
uaudio_chan_play_callback()
usbd_callback_wrapper()
usb_command_wrapper()
usb_callback_proc()
usb_process()

I'm on 13.0-BETA, amd64.

This is the interface, but the problem also occurs with a different device:

uaudio0 on uhub3
uaudio0: <Scarlett Solo USB> on usbus2
uaudio0: Play[0]: 192000 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Play[0]: 176400 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Play[0]: 96000 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Play[0]: 88200 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Play[0]: 48000 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Play[0]: 44100 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 192000 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 176400 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 96000 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 88200 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 48000 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: Record[0]: 44100 Hz, 2 ch, 32-bit S-LE PCM format, 2x8ms buffer.
uaudio0: No MIDI sequencer.
pcm7: <USB audio> on uaudio0
uaudio0: No HID volume keys found.