Bug 510786 - Taskbar glitch and plasmashell lockup after 2nd monitor unplugged
Summary: Taskbar glitch and plasmashell lockup after 2nd monitor unplugged
Status: RESOLVED FIXED
Alias: None
Product: plasmashell
Classification: Plasma
Component: Panel (other bugs)
Version First Reported In: 6.4.5
Platform: Arch Linux Linux
: NOR major
Target Milestone: 1.0
Assignee: Plasma Bugs List
URL:
Keywords: multiscreen
Depends on:
Blocks:
 
Reported: 2025-10-19 12:28 UTC by admin
Modified: 2025-10-24 16:13 UTC (History)
4 users (show)

See Also:
Latest Commit:
Version Fixed/Implemented In: 6.5.0
Sentry Crash Report:


Attachments
glitch (538.42 KB, video/webm)
2025-10-19 12:28 UTC, admin
Details

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Description admin 2025-10-19 12:28:33 UTC
Created attachment 185901 [details]
glitch

SUMMARY
Taskbar visual glitch happens on laptop internal screen when 2nd monitor is unplugged.

After about 10 minutes plasmashell lockups using 100% of CPU, taskbar become unresponsive.

Host PC is ASUS TUF A14 2025 (2560x1600 140% DPI), external screen is Gigabyte M32U (3840x2160 105% DPI), extended to the right side.

STEPS TO REPRODUCE
1. Connect external screen (Or connected before boot up)
2. Unplug external screen
3. Glitch happens
4. Wait about 10 minutes
5. Shell dead

OBSERVED RESULT
Visual glitch and shell dead

EXPECTED RESULT
No glitch

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0
Kernel Version: 6.17.3-3-cachyos (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen AI 7 H 350 w/ Radeon 860M
Memory: 32 GiB of RAM (29.0 GiB usable)
Comment 1 Nate Graham 2025-10-20 17:45:57 UTC
Well that's strange. Does it ever happen with a new clean user account on the same machine with no customization except for moving the panel to the left side?
Comment 2 admin 2025-10-20 18:08:33 UTC
(In reply to Nate Graham from comment #1)
> Well that's strange. Does it ever happen with a new clean user account on
> the same machine with no customization except for moving the panel to the
> left side?

Yes it also happens with a new clean user. The only thing I did is move the panel to the left side, then clone the panel to external monitor.
Comment 3 Nate Graham 2025-10-21 13:32:17 UTC
Thanks!
Comment 4 TraceyC 2025-10-22 19:45:23 UTC
If something crashed, we need a backtrace of it so we can figure out what's going on. Can you please attach a backtrace of the crash using the coredumpctl command-line program, as detailed in https://community.kde.org/Guidelines_and_HOWTOs/Debugging/How_to_create_useful_crash_reports#Retrieving_a_backtrace_using_coredumpctl ?

If there are no coredumps, then this isn't actually a crash, and there are other steps we can try.

Thanks.
Comment 5 admin 2025-10-22 20:32:27 UTC
(In reply to TraceyC from comment #4)
> If something crashed, we need a backtrace of it so we can figure out what's
> going on. Can you please attach a backtrace of the crash using the
> coredumpctl command-line program, as detailed in
> https://community.kde.org/Guidelines_and_HOWTOs/Debugging/
> How_to_create_useful_crash_reports#Retrieving_a_backtrace_using_coredumpctl ?
> 
> If there are no coredumps, then this isn't actually a crash, and there are
> other steps we can try.
> 
> Thanks.

I think the plasmashell "crash" (more like lockup, doesn't take any input) after Taskbar glitch maybe is caused by something else, in last 2 days' reproduction the lockup didn't happen.

I've coredumpctl installed and the last dump is something else earlier.
Comment 6 TraceyC 2025-10-23 15:52:25 UTC
Thanks for clarifying. It does sound like two things happened. We'll keep this report focused on the taskbar glitch and plasmashell lockup. If you see another crash, please create a new report for it.

Can you run  `sudo perf top -g` until the system misbehaves and take a screenshot, then attach that to this report? That will give us an idea of what's causing the lockup. Thanks.
Comment 7 admin 2025-10-24 15:55:57 UTC
The issue is disappeared after updating to 6.5.0, good job !
Comment 8 TraceyC 2025-10-24 16:13:41 UTC
That's great to hear! Thanks for letting us know.