Plasma workspace broken (no taskbar, plasmashell not responding)

on my LEAP 42.3 system, all users cannot start KDE Plasma Desktop properly.

They just get the background image, mouse pointer, can use ALT-F2 to start commands like “konsole”
or any others. But there is no taskbar, plasmashell does not respond to clicks (not on the little icon,
no right click on the background).

kquitapp  plasmashell

does not stop plasmashell. I can kill it and “kstart” it again, but that does not help.

I’ve removed .config/plasma-org.kde.plasma.desktop-appletsrc and restarted: no change.
I’ve used a fresh user: same problem.

The system has been upgraded from OpenSuse 13.1 to LEAP 42.3 a while ago, which went fine.
On 2017-10-08 when the problem started I’ve got some package updates,
but they look unrelated (libvirt*, mozilla*, libsoftokn3, git* , yast2-bootloader, yast2-xml).

The system is fully updated (some more updates today). Here is the used repo list:

zypper lr -Eup
#  | Alias                           | Name                                                    | Enabled | GPG Check | Refresh | Priority | URI                                                              
 1 |   | Haupt-Repository (NON-OSS)                              | Yes     | (r ) Yes  | Yes     |   99     |
 2 | | Aktualisierungs-Repository (Nicht-Open-Source-Software) | Yes     | (r ) Yes  | Yes     |   99     |           
 3 |       | Haupt-Repository (OSS)                                  | Yes     | (r ) Yes  | Yes     |   99     |  
 4 |     | Hauptaktualisierungs-Repository                         | Yes     | (r ) Yes  | Yes     |   99     |            
 5 | dvd                             | dvd                                                     | Yes     | (r ) Yes  | Yes     |   99     |               
 7 | packman                         | packman                                                 | Yes     | (r ) Yes  | Yes     |   99     | 

There is nothing obvious in the .xsession-error log. And nothing obvious when kstarting plasmashell.

The problem started to appear when I was trying to use yast to change my printer settings.
cups sometimes seems to hang, so I may have ended some processes and restarted.

Any hints how to further resolve or debug this?

Thanks in advance,

If it’s no problem for you, you could reset the plasmadesktop to default, by invoking

rm ~/.config/plasma*

then hit Ctrl+Alt+Backspace twice

Hi Knurpht,
thanks for the suggestion! I’ve tried with one user, but it did not help.

Later I got the right idea: I’ve straced plasmashell and saw that it was somehow hanging while asking cups.
Disabling cups made plasmashell start again. I guess there is a defect somewhere, probably a missing timeout
as a hanging cupsd should not render plasmashell broken.

To document it, I did something like

# killing plasmashell first, then restarting it with strace
strace -o trace1 plasmashell

# in a second window
vim trace1

# scrolled back, found stuff before a number of polls like
3374  connect(32, {sa_family=AF_LOCAL, sun_path="/run/cups/cups.sock"}, 22) = 0
3374 sendto(32, "POST / HTTP/1.1
Content-Length:"..., 180, 0, NULL, 0) = 180

# as root
systemctl stop cups
# plasmashell continued, now permanently disabling cups (printer daemon) until debugging is possible
systemctl disable cups

Best Regards and thanks for caring!
ps.: If someone wants to follow up on the defect later, relevant versions are plasma5-workspace-5.8.7-6.1.x86_64
and cups-1.7.5-11.1.x86_64.

Does uninstalling kde-print-manager help then?
(or disabling the applet in the system tray settings)

Just an FYI, this problem isn’t unique. I’ve been using alt-tab to change windows and save my work. I have no idea if the print manager is the culprit, but I have removed it and will do a post regarding if that fixes the problem or not.

I’m on a Dell E6400 ATG with Intel graphics.
Linux linux-0u81 4.4.92-31-default #1 SMP Sun Oct 22 06:56:24 UTC 2017 (1d80e8a) x86_64 x86_64 x86_64 GNU/Linux

I’ve deleted kde-print-manager and have put a few hours on the PC. I believe the problem is solved. I will leave it up to the gurus to determine if this requires a bug report.

Thanks for the tip.

After reinstalling and reconfiguring cups, cups did not hang anymore
and I did not run into the issue again. So I did not do further tests.

Maybe suspending the cupsd process could provoke the problem, but this is just a wild guess.