Bug 487700

Summary:	X11-forwarded apps briefly freeze the wayland session
Product:	[Plasma] kwin	Reporter:	Firlaev-Hans <firlaevhanskde.upstream314>
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	fort.malvery
Priority:	NOR
Version First Reported In:	6.0.5
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:
Attachments:	backtrace after freeze

Description Firlaev-Hans 2024-05-28 17:14:24 UTC

SUMMARY
I'm using X11 forwarding via SSH to run some applications on a remote system and interact with them on my local system, which is running a Wayland session.
Every couple of seconds when interacting with the forwarded application, my entire screen freezes for 3 seconds or so. This makes X11 forwarding extremely tedious to use in the wayland session.
I don't see any relevant messages about this in the journal.

STEPS TO REPRODUCE
1. While in a Wayland session, connect to a remote system via SSH with X11 forwarding enabled
2. Run any graphical application on the remote host so that it displays on your local machine
3. Interact with the window

OBSERVED RESULT
The whole screen freezes regularly for several seconds.

EXPECTED RESULT
Everything should be smooth, at most the forwarded Xwayland window should freeze but not the whole desktop

SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 40
KDE Plasma Version: 6.0.5
KDE Frameworks Version: 6.2.0
Qt Version: 6.7.0
Kernel Version: 6.8.10-300.fc40.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 20 × 12th Gen Intel® Core™ i7-12700H
Memory: 15.3 GiB of RAM
Graphics Processor: Mesa Intel® Graphics

ADDITIONAL INFORMATION
I tried to run Nautilus, Firefox and Virtualbox via SSH X11 forwarding on a Debian 12 server and observed the same behavior with all of them. I have no such problems when using Waypipe but unfortunately at least VirtualBox needs X11.

Comment 1 malvery 2024-08-30 08:06:12 UTC

Same problem here on the plasma 6.1.4. When I forward xwayland socket /tmp/.X11-unix/X0 to the incus contaner (example ubuntu 22.04) and set Xauth token, when interaction with the opened X11 application from this container freezes entire plasma session for the a few seconds.

Comment 2 Vlad Zahorodnii 2024-09-27 08:38:35 UTC

Can you get kwin_wayland's backtrace when the screen is frozen? You would need to SSH from another machine and attach a debugger to kwin_wayland process. https://community.kde.org/KWin/Debugging

Comment 3 Vlad Zahorodnii 2024-10-01 10:17:51 UTC

Comment 4 malvery 2024-10-01 11:15:24 UTC

Created attachment 174262 [details]
backtrace after freeze

Attached backtrace after freeze happened. Sorry, I don't familiar with gdb and do steps only from https://community.kde.org/KWin/Debugging#TL;DR_for_bug_reporters. If that backtrace doesn't help, please clarify what should I do, thanks.

Comment 5 Bug Janitor Service 2024-10-16 03:47:41 UTC

🐛🧹 ⚠️ This bug has been in NEEDSINFO status with no change for at least 15 days. Please provide the requested information, then set the bug status to REPORTED. If there is no change for at least 30 days, it will be automatically closed as RESOLVED WORKSFORME.

For more information about our bug triaging procedures, please read https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging.

Thank you for helping us make KDE software even better for everyone!

Comment 6 Bug Janitor Service 2024-10-31 03:47:02 UTC

🐛🧹 This bug has been in NEEDSINFO status with no change for at least 30 days. Closing as RESOLVED WORKSFORME.

Comment 7 Firlaev-Hans 2024-11-08 10:45:14 UTC

Sorry for not responding in such a long time but I finally got around to trying to get a backtrace, however I can no longer reproduce this issue on any system (with Intel, AMD or VirtIO graphics) on Plasma 6.2.
I still recommend using Waypipe instead of X11 forwarding whenever possible since it performs a million times better but at least X11 forwarding is a usable option now.