Bug 436720

SUMMARY
In the summary everything is said.

Occurs in Debian 11 (Bullseye - testing). But I suppose it will also happen to others. It took me almost a month to find out where the culprit was. I have looked at logs and could not find the cause.

To this day the problem continues. I have verified it on two other PCs that did not suffer from this problem. Activating the composer the problem also appears on those PCs.

I have changed the OpenGl 3.1, 2.0 and XRender rendering engine but the same thing happens.

Fixed temporarily using DefaultTimeoutStopSec = 10s option in /etc/systemd/system.conf file

My graphics card are a NVIDIA Geforce GTX 690
On the other PC I have a GTX 980 Ti with the same problem.

STEPS TO REPRODUCE
1. Installed Debian 11 Bullseye (actually testing) and KDE Plasma. Graphics NVIDIA
2. Enable composer (systemd -> Hardware -> Screen and monitor -> Composer .. Select Enable composer at startup.
3. Exit the session once. Re-login and restart or shut down the PC. 

OBSERVED RESULT
The PC delay 90 seconds to reboot or power off.

EXPECTED RESULT
It should turn off quickly even if the composer is selected.

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: Debian 11 Bullseye (testing)/KDE Plasma 5.20.5
(available in About System)
KDE Plasma Version: 5.20.5
KDE Frameworks Version: I do not understand.
Qt Version: Package: qtbase5-dev (5.15.2+dfsg-5)

ADDITIONAL INFORMATION
I have been with this problem for more than a month but they have not solved it. Debian 11 is about to be released as stable, but it looks like a beta. I think I should contribute by communicating this problem.

Greetings.