I have noticed much longer waiting time during each reboot/shutdown, after the most recent update on my setup (5.4.101-1-MANJARO KDE Plasma):
https://pastebin.com/raw/qZcaQJ0X
There are several issues within the logs and I’ll try to list a few hints related to them below:
QDBusAbstractAdaptor: Cannot relay signal KDEDModule::moduleDeleted(KDEDModule*): Pointers are not supported: KDEDModule*
[...]
/etc/udev/rules.d/66-maxperfwiz.rules:1 Failed to write ATTR{/sys/devices/.../queue/scheduler}, ignoring: No such file or directory
[...]
plasma-kactivitymanagerd.service: Main process exited, code=exited, status=1/FAILURE
[...]
Activation via systemd failed for unit 'rtkit-daemon.service': Refusing activation, D-Bus is shutting down.
[...]
xdg-desktop-portal-kde: This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.
[...]
systemd-coredump.socket: Failed to queue service startup job (Maybe the service file is missing or not a non-template unit?): Transaction for systemd-coredump@2-2382-0.service/start is destructive (shutdown.target has 'start' job queued, but 'stop' is included in transaction).
[...]
systemd-coredump.socket: Failed with result 'resources'.
[...]
xdg-desktop-por: Failed to get application states: GDBus.Error:org.freedesktop.DBus.Error.Spawn.ChildSignaled: Process org.freedesktop.impl.portal.desktop.kde received signal 6
[...]
Activated service 'org.kde.KSplash' failed: Process org.kde.KSplash exited with status 1
[...]
session-2.scope: Killing process 1829 (kwin_x11) with signal SIGKILL.
session-2.scope: Failed with result 'timeout'.
[...]
Activation via systemd failed for unit 'dbus-org.freedesktop.nm-dispatcher.service': Refusing activation, D-Bus is shutting down.
[...]
kernel: watchdog: watchdog0: watchdog did not stop!
The following file may be relevant for the issue num. 2 above:
$ cat /etc/udev/rules.d/66-maxperfwiz.rules
ACTION=="add|change", KERNEL=="nvme[0-9]*", ATTR{queue/scheduler}="none"
ACTION=="add|change", KERNEL=="sd[a-z]|mmcblk[0-9]*", ATTR{queue/rotational}=="0", ATTR{queue/scheduler}="mq-deadline"
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="1", ATTR{queue/scheduler}="bfq"