https://bugs.kde.org/show_bug.cgi?id=447184
Bug ID: 447184
Summary: plasmashell uses 100% of cpu for extended period when
switching desktops, when a custom *.desktop file is
pinned in Task Manager
Product: plasmashell
Version: 5.18.7
Platform: Ubuntu Packages
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Task Manager and Icons-Only Task Manager
Assignee: h...@kde.org
Reporter: volo...@mindspring.com
CC: plasma-b...@kde.org
Target Milestone: 1.0
SUMMARY
***
Plasmashell will hang after desktop switch, with one core showing 100% CPU
utilization, when a custom *.desktop file is pinned in Task Manager
***
Creating a custom app.desktop which runs a shell command when clicked and
adding it (to be "pinned") in icons-only Task Manager creates a reproducible
hang for extended period when switching desktops.
Plasmashell will show in top as using 100% CPU and it takes quite a while for
the condition to resolve itself. Profiling with perf shows a lot of system
calls. Profiling with strace shows that the app.desktop file keeps being
repeatedly accessed. A typically pattern is several lstat() calls walking
directory tree two access() calls and then an openat() call. This repeats for a
while.
Note that the symptoms of this hang are similar to the hang one gets when
running plasmashell for extended time, except that in this case the problem is
triggered by adding the app.desktop to Task Manager, and is fixed by unpinning
the icon. It can be triggered again by adding the icon back.
It might (or might not) be relevant that I have a lot of other windows, in
particular Firefox opened at the same time. Firefox does have KDE integration
enabled.
Also, I have plasmashell panel with Task manager on the right side of the
screen (not the bottom).
STEPS TO REPRODUCE
0. A plasmashell desktop that has been in use for a while - many firefox
windows, many kwrite windows. Plasmashell panel on the right side of the
screen. Some kwrite windows slid under the panel on the right.
1. Create a custom app.desktop and add it Task manager.
2. Switch desktops
OBSERVED RESULT
100% CPU usage by plasmashell in top.
Significant delay before this is resolved.
EXPECTED RESULT
No delay in responsiveness when switching desktops.
SOFTWARE/OS VERSIONS
Windows:
macOS:
Linux/KDE Plasma:
(available in About System)
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
ADDITIONAL INFORMATION
Ubuntu 20.04
Intel 64-bit.
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