[Wayland] xdg-desktop-portal-kde hogs CPU after logout and login

[qydw]

1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu
Operating System: Kubuntu 21.04
KDE Plasma Version: 5.21.3
KDE Frameworks Version: 5.80.0
Qt Version: 5.15.2
Kernel Version: 5.11.0-13-generic
OS Type: 64-bit
Graphics Platform: Wayland
Processors: 4 × Intel® Core™ i5-3337U CPU @ 1.80GHz
Memory: 3.7 GiB of RAM
Graphics Processor: Mesa DRI Intel® HD Graphics 4000

2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center
xdg-desktop-portal-kde:
  Installed: 5.21.3-0ubuntu1
  Candidate: 5.21.3-0ubuntu1
  Version table:
 *** 5.21.3-0ubuntu1 500
        500 https://mirrors.tuna.tsinghua.edu.cn/ubuntu hirsute/universe amd64 Packages
        100 /var/lib/dpkg/status

3) What you expected to happen
After logout and login, xdg-desktop-portal-kde should not hog CPU.

4) What happened instead
After logout and login, xdg-desktop-portal-kde hogs CPU.

The bug was also reported on KDE Bugtracking System.
https://bugs.kde.org/show_bug.cgi?id=433293

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: xdg-desktop-portal-kde 5.21.3-0ubuntu1
ProcVersionSignature: Ubuntu 5.11.0-13.14-generic 5.11.7
Uname: Linux 5.11.0-13-generic x86_64
ApportVersion: 2.20.11-0ubuntu61
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Sun Apr 4 10:06:58 2021
SourcePackage: xdg-desktop-portal-kde
UpgradeStatus: Upgraded to hirsute on 2021-04-02 (1 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Cass Stephen (madeoutofsprings)]

Operating System: Kubuntu 21.10
DE: KDE 5.86.0 / Plasma 5.22.5
see also bug/1396367

When a second user attempts to log out it appears to log out, but afterwards gradually the fans rise to full speed.

If the first user (never logged out just locked) logs back in and runs sudo htop you can see 60ish pids running in the name of the second user, 6ish of those are using 100% of all cores.

The pids that are hogging are xdg-desktop-portal-kde and at least one kdeconnectd, usually multiple threads of kdeconnectd.

Each of the threads that those pids are in are end with a drconqi pid that, if you kill it, the entire thread closes and that core frees up.

If all of the hogging threads are killed in that way that still leaves 50ish pids running in the name of the second user, but they use 0% CPU. I have been killing all of second users threads without noticing any repercussions.