Public bug reported:

Environment:

OS: Kubuntu 25.10 (Plucky Puffin)

PPA: ppa:kubuntu-ppa/backports

Plasma Version: 6.5.5

Session: Wayland

Graphics: NVIDIA (Driver 580.126.09)

Issue:
I have identified a persistent file descriptor leak in plasmashell. Every time 
a window thumbnail preview is triggered in the Task Manager, the process leaks 
exactly 4 file descriptors. Since my system is on Wayland with NVIDIA, this 
quickly leads to reaching the FD limit, causing plasmashell to become 
unresponsive or crash.

Steps to reproduce:

Use Kubuntu 25.10 with the Backports PPA (Plasma 6.5.5).

Monitor FD count: watch "ls /proc/$(pidof plasmashell)/fd | wc -l"

Hover over a taskbar icon to show a thumbnail preview, then move away.

Observe the FD count increasing by 4 every time.

Key Findings:

This is confirmed to be related to the new Explicit Sync implementation.

Setting __NV_DISABLE_EXPLICIT_SYNC=1 completely stops the leak.

Upstream KDE bug report: https://bugs.kde.org/show_bug.cgi?id=516950

Request:
Since Plasma 6.6 is already out and likely contains fixes for synchronization 
logic, could the Kubuntu Backports team please look into backporting the fix or 
updating the PPA to a newer point release? This bug makes the current backport 
unstable for NVIDIA users.

** Affects: plasma-workspace (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2143044

Title:
  File descriptor leak in plasmashell (Task Manager thumbnails) on
  Kubuntu 25.10 with Backports PPA

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