Bug 506441

Summary:	Changing to the external screen freezes its content
Product:	[Plasma] kwin	Reporter:	Alberto Salvia Novella <es20490446e>
Component:	multi-screen	Assignee:	Alberto Salvia Novella <es20490446e>
Status:	REPORTED ---
Severity:	normal	CC:	astroturf.statistic176, kde, kdedev, xaver.hugl
Priority:	NOR	Keywords:	X11-only
Version First Reported In:	6.4.1
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	KwinSupportInfo.txt

Description Alberto Salvia Novella 2025-07-01 14:54:16 UTC

SYSTEM
- Zenned OS
- Plasma 6.4.1
- Frameworks 6.15.0
- Qt 6.9.1
- GPU-1: Internal display attached: Intel Core i7-10750H: Iris Pro: mode-setting
- GPU-2: HDMI attached: Nvidia GeForce GTX 1650: nouveau: mode-setting

STEPS
1. Change to the Plasma X11 session. Wayland is not affected.
2. By using the applet "display configuration", change to any option that uses the external display.

RESULT
- The external display doesn't update its contents, except for the mouse cursor.
- If you changed to using only the external display, the system becomes unusable.
- Screen-cast: https://youtu.be/PLRjA5LZ9xs

INFO
- On Nvidia optimus, one screen is physically attached to the iGPU and the other to the dGPU.
- It can be either, depending on the model.
- Both GPUs share video memory.

Comment 1 David Edmundson 2025-07-02 09:28:19 UTC

*** Bug 506423 has been marked as a duplicate of this bug. ***

Comment 2 David Edmundson 2025-07-02 09:29:31 UTC


*** This bug has been marked as a duplicate of bug 506461 ***

Comment 3 Alberto Salvia Novella 2025-07-02 10:50:09 UTC

@ David Edmundson

Are you sure this is a duplicate?:
https://bugs.kde.org/show_bug.cgi?id=506461

They have completely different behaviors.

If so, set status back to:
resolved -> duplicate

Comment 4 TraceyC 2025-08-13 17:07:32 UTC

We need to find out if kwin crashed or froze.

If it crashed, there will be a coredump and we need a backtrace of it so we can figure out what's going on. If there is one, 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 ?

Otherwise, can you check kwin's logs when the hard freeze occurs? 

  journalctl --boot --user-unit plasma-kwin_wayland > ~/log.txt

Also, is there any chance that you could retrieve kwin's backtrace when the
hard freeze occurs? You would need to ssh from another computer and attach a debugger to kwin process, e.g.

  sudo gdb -p $(pidof kwin_wayland)

then type

  bt

and paste the output here. Thanks!

Comment 5 Alberto Salvia Novella 2025-08-16 11:20:41 UTC

`coredumpctl --reverse`
No coredump for `kwin_x11`.

`journalctl --boot --user-unit plasma-kwin_wayland`
No error.

`sudo gdb -p $(pidof kwin_x11)`
Hangs the entire windowing system, except the mouse.

Comment 6 TraceyC 2025-08-18 16:12:13 UTC

Thanks for checking those, that's helpful. It looks like kwin isn't actually crashing, but it is freezing.

Can you attach the output of the following to this report for the kwin developers to look at?

qdbus org.kde.KWin /KWin supportInformation

Thanks!

Comment 7 Alberto Salvia Novella 2025-08-18 23:03:44 UTC

Created attachment 184230 [details]
KwinSupportInfo.txt

Comment 8 TraceyC 2025-08-19 15:47:39 UTC

Thanks. I'll let the kwin developers take it from here.

Comment 9 Alberto Salvia Novella 2025-08-19 19:03:38 UTC

Nice 👌