Hi,
Running in KDE5 on a Debian Sid machine, plasmashell freezes where I now use Alt+Tab to move to another window. I typed

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$ killall plasmashell

It will return to the prompt without doing anything and typing

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$ kquitapp plasmashell

Takes some seconds or minute and reply

kquitapp(19486): "Quitting application plasmashell failed. Error reported was:

org.freedesktop.DBus.Error.NoReply : Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken."

Weird thing is that sometimes these commands kill it successfully and sometimes doesn't

try using

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 kquitapp plasmashell

try changing the effect used when switching windows

I don't understand, I've used the kquitapp and it returns this

kquitapp(19486): "Quitting application plasmashell failed. Error reported was:

org.freedesktop.DBus.Error.NoReply : Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken."

see if these help (seem relevant):

viewtopic.php?f=289&t=124690
viewtopic.php?f=289&t=129354

Thanks, restarted my system and it's back. Will try those solutions next other time it happens.

Fyi, "kill" does *not* SIGKILL by default, but SIGTERM, which asks the process to quit.
Apparently plasmashell is hardlocked, thus doesn't respond to dbus, nor will handle system signals.

The next attempts are to
pkill -11 plasmashell # SEGV - the process is told it crashed
resp
pkill -9 plasmashell # KILL - the kernel kicks the process, may leak open resources

Okay, tried the both commands you suggested and still nothing. plasmashell remains and the command returns to prompt after I hit enter.
plasmashell froze again as I'm typing this. Please how do I debug the issue of this freezing?

> plasmashell remains
You're telling me that SIGKILL failed?

Avoid the name/process mapping attempts and kill the PID

kill -9 <pid of plasmashell>

To check where it's mumbling around, you can gdb into it and inspect the stack, see
https://community.kde.org/KWin/Debugging
on how to (doesn't matter that it's about kwin, it only covers problems when debugging from VT1)

To dump all threads at once, enter "thread apply all bt" in gdb.

Also tried to kill with process, still nothing

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donjajo@jajo-pc:~$ ps aux | grep plasmashell
donjajo   1542 15.1  0.0      0     0 ?        Zl   11:10   2:03 [plasmashell] <defunct>
donjajo   3275  0.0  0.0  12728  2172 pts/0    S+   11:24   0:00 grep plasmashell
donjajo@jajo-pc:~$ kill -9 1542


Now will try the kwin debugging

Now tried to run

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gdb --pid `pidof kwin_x11` 2>&1 | tee kwin.gdb

The whole system froze up, only my mouse was alive moving around.

I think this all started when I changed my Desktop to Folder view and same thing happened when I had a widget on my desktop. Now my desktop is blank and everything is moving smoothly

The system didn't "freeze" - gdb stalled the window manager and compositor (kwin), so nothing would repaint anymore.
Problem is that you did not want to debug KWin, but plasmashell.

However, the plasmashell process is "defunct", ie. a zombie. It already finished and you therefore cannot kill it "more".
Random google results (look all more less ok-ish on their explanations)

http://en.linuxreviews.org/Defunct_process
http://unix.stackexchange.com/questions ... nt-is-init
http://askubuntu.com/questions/201303/w ... get-killed
https://en.wikipedia.org/wiki/Zombie_process

tl;dr - you should not have to worry about that entry and it's *not* the frozen desktop. That "defunct" process is gone.

Wao, you've taught me another thing in Linux. Thanks

So its now to report the bug that once I have something on my desktop, either Folders or Widget... that is when it freezes and turn to the defunct. But since there has been nothing on my desktop, everything is going smoothly