My system has hit the same bug and I do not use firewire. I have not upgraded to mainline kernel. The power cycling work arounds above do not mitigate the issue for me.

 $ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=20.04
DISTRIB_CODENAME=focal
DISTRIB_DESCRIPTION="Ubuntu 20.04 LTS"

 $ uname -a
Linux hostname 5.4.0-39-generic #43-Ubuntu SMP Fri Jun 19 10:28:31 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

 $ pactl info
Connection failure: Connection refused
pa_context_connect() failed: Connection refused

 $ ps aux | grep pulse | grep -v grep
username    12895 17.0  0.0 100788 10908 ?        D<s  09:38   0:00 /usr/bin/pulseaudio --daemonize=no --log-target=journal

 $ sudo cat /proc/12895/stack
[<0>] usb_start_wait_urb+0x8f/0x180
[<0>] usb_control_msg+0xe3/0x140
[<0>] snd_usb_ctl_msg+0xe3/0x190 [snd_usb_audio]
[<0>] snd_usb_init_sample_rate+0x235/0x320 [snd_usb_audio]
[<0>] snd_usb_pcm_prepare+0x159/0x460 [snd_usb_audio]
[<0>] snd_pcm_do_prepare+0x1e/0x30 [snd_pcm]
[<0>] snd_pcm_action_single+0x3c/0x80 [snd_pcm]
[<0>] snd_pcm_action_nonatomic+0x6e/0x80 [snd_pcm]
[<0>] snd_pcm_prepare+0x6a/0x90 [snd_pcm]
[<0>] snd_pcm_common_ioctl+0x28c/0xc00 [snd_pcm]
[<0>] snd_pcm_ioctl+0x27/0x40 [snd_pcm]
[<0>] do_vfs_ioctl+0x407/0x670
[<0>] ksys_ioctl+0x67/0x90
[<0>] __x64_sys_ioctl+0x1a/0x20
[<0>] do_syscall_64+0x57/0x190
[<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

The stack frames line up w/ the above. 


$ journalctl -f | grep pulse # a selection of the output
Jun 27 09:38:50 hostname systemd[2373]: pulseaudio.service: State 'stop-sigterm' timed out. Killing.
Jun 27 09:38:50 hostname systemd[2373]: pulseaudio.service: Killing process 12140 (pulseaudio) with signal SIGKILL.

Jun 27 09:38:56 hostname systemd[2373]: pulseaudio.service: Main process exited, code=killed, status=9/KILL
Jun 27 09:38:56 hostname systemd[2373]: pulseaudio.service: Failed with result 'timeout'.
Jun 27 09:38:56 hostname systemd[2373]: pulseaudio.service: Scheduled restart job, restart counter is at 5.
Jun 27 09:38:56 hostname pulseaudio[12895]: Stale PID file, overwriting.
Jun 27 09:40:26 hostname systemd[2373]: pulseaudio.service: start operation timed out. Terminating.
Jun 27 09:41:56 hostname systemd[2373]: pulseaudio.service: State 'stop-sigterm' timed out. Killing.
Jun 27 09:41:56 hostname systemd[2373]: pulseaudio.service: Killing process 12895 (pulseaudio) with signal SIGKILL.
Jun 27 09:42:02 hostname systemd[2373]: pulseaudio.service: Main process exited, code=killed, status=9/KILL
Jun 27 09:42:02 hostname systemd[2373]: pulseaudio.service: Failed with result 'timeout'.
Jun 27 09:42:02 hostname systemd[2373]: pulseaudio.service: Scheduled restart job, restart counter is at 6.
Jun 27 09:42:03 hostname pulseaudio[13050]: Stale PID file, overwriting.
Jun 27 09:43:33 hostname systemd[2373]: pulseaudio.service: start operation timed out. Terminating.
Jun 27 09:45:03 hostname systemd[2373]: pulseaudio.service: State 'stop-sigterm' timed out. Killing.
Jun 27 09:45:03 hostname systemd[2373]: pulseaudio.service: Killing process 13050 (pulseaudio) with signal SIGKILL.
Jun 27 09:45:10 hostname systemd[2373]: pulseaudio.service: Main process exited, code=killed, status=9/KILL
Jun 27 09:45:10 hostname systemd[2373]: pulseaudio.service: Failed with result 'timeout'.
Jun 27 09:45:10 hostname systemd[2373]: pulseaudio.service: Scheduled restart job, restart counter is at 7.