Created attachment 164340 [details]
Strace from plasmashell started shortly before the problem

SUMMARY
When I run an elisp program in my emacs, it very often results in the desktop panel disappearing and the background goes black. It lasts for a couple of seconds and then the panel and background reappears. The emacs program finishes successfully and does not seem to be affected. In the journal there are those messages from plasmashell.

dec 21 09:25:42 mimmi plasmashell[425833]: error marshalling arguments for get_icon: dup failed: För många öppna filer
dec 21 09:25:42 mimmi plasmashell[425833]: Error marshalling request: För många öppna filer
dec 21 09:25:42 mimmi plasmashell[425833]: The Wayland connection experienced a fatal error: För många öppna filer
dec 21 09:25:42 mimmi systemd[416625]: plasma-plasmashell.service: Main process exited, code=exited, status=1/FAILURE

"För många öppna filer" is Swedish for "Too many open files"

STEPS TO REPRODUCE
Running my emacs program as described above, but it somehow is dependent on my environment. I've not been able to create an independent reproducer.

OBSERVED RESULT
Plasmashell exits with a failure. Systemd then starts a new instance, so the desktop recovers.

EXPECTED RESULT
I don't understand why this affects plasmashell at all.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 5.27.8
KDE Frameworks Version: 5.109.0
Qt Version: 5.15.11
Fedora 39

ADDITIONAL INFORMATION
This has happened for a while, it did not appear in any specific version.

The emacs program does a "grep" over files in my home directory and then emacs visits the file positions listed by the "grep" command. The command typically finds entries in up to 50 files, and the total number of hits could be in the range of hundreds. The risk of triggering the problem seems to increase with more matches, but it is hard to say exactly. As mentioned, I have tried to reproduce with a set of test files in a simple environment, but been unable to trigger it.

I started debugging by attatching an "strace" to plasmashell before running my emacs function, and have a trace from where the problem is triggered. I note that plasmashell is opening /sys/devices/system/cpu/online and creates pipes over and over again, until it runs out of file descriptors. I attach the trace hoping it might be of some help.