Bug 446010

SUMMARY
Ok, so this is kind of weird. I build my own KDE with my own scripts, and then roll it up into a bootable ISO. I have had this process for quite some time

The builds are scripted to where I can rebuild all of KDE Master and everything and roll it into an ISO it's scripted builds
Everything KDE works, except for one weird thing more recently:

So sometimes I boot the ISO, and the Task Manager/Icon Only Task Manager plasmoid, along with the Pager plasmoid work as normal. Which is good.

However, I reboot the SAME VM, with the SAME ISO and same everything, and upon boot, and login, the task manager, and the pager do NOT work.
While I can run programs off the default launchers on the Task Manager plasmoid, it does not even play the spinning launch animation (however the cursor launch feedback does bounce), and the running window is not listed when it appears. And the wireframes in the pager plasmoid do not appear.
This happens for the Icons Only Task Manager one, and the one that has the window title next to the icon


What is odd is that if I start Latte Dock under the session (which I also build myself) and add a Pager plasmoid, and task manager plasmoid, those on Latte dock work.
Krunner can also list the running windows just fine too. So I don't think the problem is with kwin, and the protocol it uses.

Now sometimes if I get lucky, I blow away .cache  (sometimes I can narrow it down to removing .cache/ksycoca*, and run plasmashell --replace, and when it comes back up, the pager and taskmanager randomly start working! And once it works, future runs of plasmashell --replace, I am then unable to replicate the problem anymore, until I reboot the VM...

I tried to compare the standard output of plasmashell when the plasmoids don't work, and from when they do work, and using kompare to see the differences, and nothing obvious stood out,

And one time, before I got plasmashell --replace to work, I also tried to make ~/.config, ~/.local, and ~/.kde folders under $HOME all into git repos, so I can do git diff to see if anything changes under those once it starts working, and nothing stands out in the config. It seems to be something under .cache

I don't know if it's a race condition or something, I tried to set QML_DISABLE_DISK_CACHE=1 since there are a bunch of QMLC files under .cache for plasmashell, but that doesn't seem to really help.

The only thing I can suspect at this point is the ksycoca* file under .cache , but I am only guessing at this point. It might be some weird race condition or something. I am now at a loss of figuring this out. It seems to be plasmashell, and not say kwin_wayland, or some other process, since plasmashell --replace eventually works in the same session

It's not scientific, but it seems to happen more when I have two virtual CPUs, compared to only one.

In the live ISO, I have a very minimal config in /etc/skel/.config for some files, but I tried to eliminate that, and that doesn't seem to be the problem



SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Kernel 5.14 /Master
(available in About System)
KDE Plasma Version: Master
KDE Frameworks Version:  Master
Qt Version: 5.15

ADDITIONAL INFORMATION