Created attachment 1552941 [details]
dmesg-5.0.5-200.fc29.x86_64

Description of problem:
After longish use of KDE Plasma session, Xorg server runs out of an anonymous file handles (a count of 1024 by default). I.e. /proc/`pidof Xorg`/fd fills up entries like:
...
lrwx------. 1 root root 64 Apr  6 10:55 95 -> '/memfd:xshmfence (deleted)'
lrwx------. 1 root root 64 Apr  6 13:18 96 -> '/memfd:xshmfence (deleted)'
lrwx------. 1 root root 64 Apr  6 10:55 97 -> '/memfd:xshmfence (deleted)'
lrwx------. 1 root root 64 Apr  6 10:55 98 -> '/memfd:xshmfence (deleted)'
lrwx------. 1 root root 64 Apr  6 10:55 99 -> '/memfd:xshmfence (deleted)'
...
And when Xorg has run out of system file limit, random problems start to appear:
- key bindings may lost and/or have no desired effect
- mouse clicks / drags have no effect
- $HOME/.cache corrupts somehow

Version-Release number of selected component(s):
kernel-5.0.5-200.fc29.x86_64
xorg-x11-drv-amdgpu 19.0.0
plasma-workspace 5.14.5
mesa 18.3.5

How reproducible:
always

Steps to Reproduce:
1. login to Plasma session
2. open dozens of appications so that Task Manager starts grouping task instances
3. observe content of /proc/`pidof Xorg`/fd by commands ls and wc
4. induce creation of memfd:xshmfence fds by hovering on panel (Task Manager), over group of open tasks so that Task Manager shows thumbnails of windows of open applications. This step will increase fds by number of window thumbnails of hovered group
5. repeat from 3. until system file limit is hit

Actual results:
see above

Expected results:
plasmashell shall release rendering related memory stuff right after use

Additional info:
Hovering on Pager or on System Tray in a such way that popup window appears does not consume an anonymous file handles on X server permanently. Only via Task Manager does.