Bug 489951

Summary:	Screen locking sometimes freezes the system on both X11 and Wayland
Product:	[Unmaintained] kscreenlocker	Reporter:	jat255
Component:	general	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	veehexx
Priority:	NOR
Version First Reported In:	6.1.2
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description jat255 2024-07-08 23:49:54 UTC

SUMMARY

Screen locking is broken on my KDE Plasma 6 system. Often, I can lock/unlock my screen exactly once, and subsequent attempts to lock (either manually, or auto-lock on screen timeout or suspend) causes a system lock-up. I notice two different behaviors: on Wayland, the screen will turn black and only the cursor will be visible (similar to https://bugs.kde.org/show_bug.cgi?id=483163). On X11 (my typical session), the system will appear to be working, but I cannot click on anything. Oddly, when in this "frozen" state, hovering over things that were active in the interface will cause them to be highlighted, but I can't click on them.

Some notes from researching if this is the same as bug #483163:

- Changing the theme to "Breeze Dark" does not appear to help (it does in #483163)
- I cannot "blind" type in my password and press enter to unlock the screen and get access (this works in #483163)
- switching to another TTY and back to tty2 does not fix/unlock the system (this was reported to workaround in #483163)

STEPS TO REPRODUCE
1. Login to KDE Plasma (X11 or Wayland)
2. Lock the screen with Meta+L and then unlock
3. Lock the screen again

OBSERVED RESULT
The system is "hung" and cannot be recovered without rebooting from another tty

EXPECTED RESULT
Lock screen window correctly drawn.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 6.1.2
KDE Frameworks Version: 6.3.0
Qt Version: 6.7.2
Kernel Version: 6.6.37-1-lts (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-8650U CPU @ 1.90GHz
Memory: 15.4 GiB of RAM
Graphics Processor: Mesa Intel® UHD Graphics 620
Manufacturer: LENOVO
Product Name: 20KHCTO1WW
System Version: ThinkPad X1 Carbon 6th

ADDITIONAL INFORMATION

This is similar to https://bugs.kde.org/show_bug.cgi?id=483163, but not exactly the same. I would also like to know if there's some CLI command to unlock the system, which would allow me to workaround this without a hard reboot. `logingctl unlock-session` does not appear to do anything. I would also be happy to provide any debugging information needed. I do not see anything of relevance when this occurs in journalctl.

Comment 1 jat255 2024-07-08 23:51:48 UTC

I meant to add that this problem does not *always* occur, but I have not quite tracked down when/why it doesn't.

Comment 2 jat255 2024-07-10 20:17:29 UTC

I did finally figure out that I can work around this by jumping to a TTY and killing `kscreenlocker_greet`, which then auto-restarts and I can unlock my session as normal when switching back to TTY2

Comment 3 jat255 2024-07-12 14:59:56 UTC

I believe this person is having the same issue: https://discuss.kde.org/t/kscreenlocker-freezes-and-have-to-be-killed/15096

Comment 4 Tim D 2024-08-13 20:29:21 UTC

if I've understood you correctly, it seems this issue is recoverable via ctrl+alt+F[1-7]?

(i'm hunting for existing bugs related to this, but a hard freeze - even capslock wont toggle its LED).

Comment 5 jat255 2024-08-13 20:41:45 UTC

(In reply to Tim D from comment #4)
> if I've understood you correctly, it seems this issue is recoverable via
> ctrl+alt+F[1-7]?
> 
> (i'm hunting for existing bugs related to this, but a hard freeze - even
> capslock wont toggle its LED).

Yes, I was still able to switch to a virtual tty when the system was locked (more of a soft freeze). This appears to have been resolved in either an update or configuration change, as I haven't had it happen in a couple of weeks, so I'll close this for now.