Bug 487053

Summary:	When fingerprint signature is enabled lock screen not shown when locked shortly after unlock
Product:	[Plasma] plasmashell	Reporter:	Oleg Gorobets <oleg.goro>
Component:	Screen locking	Assignee:	Plasma Bugs List <plasma-bugs-null>
Status:	CONFIRMED ---
Severity:	normal	CC:	kdedev
Priority:	NOR
Version First Reported In:	6.0.4
Target Milestone:	1.0
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Oleg Gorobets 2024-05-15 11:44:22 UTC

SUMMARY
When fingerprint signature is enabled there is some weird behavior when locking screen again shortly after unlock (a few seconds). On this second attempt no lock screen is shown. Instead all windows become unresponsive. I can move the mouse around, but cannot interact with any windows and controls. Keyboard input is also blocked. After a few seconds mouse and keyboard become unblocked and I can use KDE as usual.

Jounrlctl shows the following warning at about the same time:

тра 15 11:44:27 p15v ksmserver[14600]: QProcess::start: Process is already running

When I remove fingerprint signature via fprintd-delete, lock screen works as expected.

STEPS TO REPRODUCE
1. Create fingerprint signature as per https://wiki.archlinux.org/title/fprint#Create_fingerprint_signature
2. Lock screen with Meta+L shortcut
3. Unlock screen with password
4. Wait 5 seconds
5. Lock screen with Meta+L shortcut

OBSERVED RESULT
No lock screen is shown. All windows and controls become unresponsive, keyboard input is blocked.


EXPECTED RESULT
Lock screen is shown.


SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 6.0.4
KDE Frameworks Version: 6.1.0
Qt Version: 6.7.0


ADDITIONAL INFORMATION
Kernel Version: 6.8.7-arch1-1 (64-bit)
Graphics Platform: X11
Fingerprint Reader: Synaptics, Inc. Prometheus MIS Touch Fingerprint Reader

Comment 1 TraceyC 2025-03-04 22:19:07 UTC

Thank you for the bug report. Unfortunately we were not able to get to it yet. Can we ask you to please check if this is still an issue with Plasma 6.3.2 (the latest released version)?

If you can still reproduce the bug, please change the Status to "CONFIRMED". Thanks.

Comment 2 Oleg Gorobets 2025-03-13 16:57:05 UTC

(In reply to TraceyC from comment #1)

I can still reproduce this on Plasma 6.3.2 every time. Same behavior on X11 (frozen screen).

I also tested Wayland and it's similar there, the only difference that on Wayland the result is black screen.

Comment 3 TraceyC 2025-03-14 15:31:21 UTC

I'm able to reproduce this with Wayland git-master on a laptop where I have working fingerprint unlocking and a fingerprint enrolled
Following the original reproduction steps results in a black screen with a mouse cursor