https://bugs.kde.org/show_bug.cgi?id=527314
Bug ID: 527314
Summary: Window List in a vertical panel wider than 144 px
makes plasmashell spin at 100% CPU (Plasma 6.8.0)
Classification: Plasma
Product: plasmashell
Version First 6.8.0
Reported In:
Platform: EndeavourOS
OS: Linux
Status: REPORTED
Severity: crash
Priority: NOR
Component: Window List widget
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: 1.0
Window List in a vertical panel wider than 144 px makes plasmashell spin at
100% CPU (Plasma 6.8.0)
DESCRIPTION
When a panel on the right edge of the screen containing the Window List widget
is widened past 144 px, the plasmashell hangs at 100% CPU. The same wide panel
without the window list widget does not cause any issues.
STEPS TO REPRODUCE
1. Create a vertical panel on the right edge of the screen.
2. Add the Window List widget to it.
3. In Edit Mode, increase the panel thickness above 144 px.
4. It may take a few minutes before the hang occurs, or it may occur
immediately, so you may have to wait to see the freeze happen.
OBSERVED RESULT
plasmashell goes to ~100% CPU and all panels and widgets stop responding.
It does not recover until killed. The new size is not saved, so a restart
comes back with the last good thickness. With an older saved layout that
already contained the wide panel, plasmashell hung during startup (no panels
drawn, one thread spinning).
EXPECTED RESULT
The panel is able to contain the Window List widget at any width without
hanging plasmashell.
SOFTWARE/OS VERSIONS
Operating System (available in the Info Center app, or by running `kinfo` in a
terminal window): EndeavourOS, kernel 7.2.11-arch1-1
KDE Plasma Version: 6.8.0
KDE Frameworks Version: 6.31.0
Qt Version: 6.12.0
Wayland session, Intel Iris Xe (Mesa), 1920x1200, scale 1, single display
ADDITIONAL INFORMATION
- The backtraces contained some hints to the Sweet theme as being a culprit (I
changed it to Breeze in case it was an issue) but that has not been confirmed
as an isolated trigger.
- Left edge has not been tested, only right edge.
I have some more info about the backtraces, but I synthesized this info using
an LLM since it's not something I can really understand myself:
- Earlier hang (before I identified the panel-width trigger): plasmashell
was stuck at 100% CPU right after resetting my panel layout, with a custom
color scheme active. Switching to Breeze Dark fixed that one. The main
thread was in QQuickLayout::updatePolish -> QGridLayoutEngine::setGeometries
-> QQuickItem::setSize -> ... Kirigami::Platform::PlatformTheme::event /
PlatformThemeChangeTracker (libKirigamiPlatform). All other threads idle.
This may be the same loop as the wide-panel hang or a separate trigger;
I could not tell. Attached: thread1-nosymbols.txt
- Two later captures during wide-panel hangs: only a single frame resolved,
in libQt6QuickLayouts and in libQt6Core/libQt6Qml respectively. Main thread
each time, other threads idle. Debug symbols would not download in a
reasonable time. I can capture again if a specific procedure is wanted.
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