possible bug in udev?

[Martin Renwanz]

Hi everyone,

I stumbled recently over an interesting issue. I have an external 
bluray-drive, connected via usb. I have 20.04.3 LTS running, with latest 
patches applied.
Now, whenever I open the cd-tray with the button, the tray opens, the 
activity LED starts blinking fast, and I am unable to close the tray, as 
it is ejected immediately after closing it.

I hooked myself with udevadm monitor -u, and noticed an endless loop of 
events coming in. The only way to stop this is to disconnected the drive.

I was able to fix this (although creating another problem) by copying 
and modifying /lib/udev/rules.d/60-cdrom_id.rules - after removing the 
RUN+= part from the line which handles the cd eject, the problem was 
gone. (and udevadm did not show an endless loop of event when the eject 
button is pressed!)

I posted my problem (and the solution) on a stackexchange site, if 
anyone cares for further details.

https://unix.stackexchange.com/questions/668928/unable-to-close-cd-tray

My question is: my "fix" obviously is only a workaround, I have not been 
able to find the root cause. Is this a bug inside ubuntu / systemd, or 
did I make a mistake somewhere ?

Best Regards,
Martin Renwanz