Comment 15 for bug 1908423

I have the same/similar issue on my RPi 4. While playing video with Kodi the Pi randomly will hang and be unresponsive to mouse, keyboard and display frozen. I can SSH and the web server plus torrent servers are still running fine but the cpu load slowly rises to something in the 8-9 range. If left alone it will recover after maybe 30-45 minutes and when it does the kernel posts the below two messages to dmesg. Always the same two messages. I have also seen the "kworker has blocked for more than 120 seconds" message as mentioned above but not lately.

Distro:
Ubuntu MATE for Raspberry Pi 20.04

uname:
Linux raspberry 5.8.0-1011-raspi #14-Ubuntu SMP PREEMPT Tue Dec 15 08:53:29 UTC 2020 aarch64 aarch64 aarch64 GNU/Linux

dmesg:
[So Jan 10 04:31:09 2021] raspberrypi-firmware soc:firmware: mbox_send_message returned -62
[So Jan 10 04:31:09 2021] cpu cpu0: dev_pm_opp_set_rate: failed to find current OPP for freq 18446744073709551554 (-34)

Based on the "dev_pm_opp_set_rate" error I assumed it was related to the cpufreq function so I changed the cpufreq governor to 'performance' and I haven't had any issues since. I'll continue testing and maybe someday try to debug the kernel but for now it's fixed by leaving the governor on performance.

If I'm right then this isn't a Ubuntu bug but really a kernel bug, specific to the Raspberry Pi.