Bug 459643

Summary:	Plasma hangs when trying to log out while program "Ding" is running and Compositing/HiddenPreviews is not set to "Always"
Product:	[Plasma] kwin	Reporter:	imaginator
Component:	compositing	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	CONFIRMED ---
Severity:	normal	CC:	jack, nate, zawertun
Priority:	NOR
Version:	5.24.4
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description imaginator 2022-09-25 11:42:56 UTC

Since version 5.19 Plasma hangs when trying to log out/reboot/shutdown while dictionary "Ding" (Tk based frontend to grep) is running and Compositing/HiddenPreviews is not set to "6" in .config/kwinrc or "Always" in Systemsettings/Monitor/Compositor/Keep Window Thumbnails.

What I have observed is that Ding's icon in the taskbar is the first to vanish from the taskbar and immediately thereafter the screen freezes. The mousepointer can still be moved but clicking anywhere has no effect.

The session can not be revived/replaced and the only way to get back to the login screen of the display manager (lightdm) is to kill process "startplasma-x11" in a VT.

The problem does *not* exist in Plasma-5.18.7, I've checked this several times today. Irrespective of the setting of "HiddenReviews" (here: 4/5/6), all logouts and reboots were just fine.

While a bug in Ding cannot be ruled out, a bug in Plasma >= 5.19 seems more likely since no earlier version had this problem and neither does xfce on the same PC.

The system is a SysVinit-system but the problem has also been confirmed for a systemd-system by user popov895 (https://bugs.kde.org/show_bug.cgi?id=374538#c68).

--
Current system:

Operating System: Linux
KDE Plasma Version: 5.24.4
KDE Frameworks Version: 5.91.0
Qt Version: 5.15.2
Kernel Version: 5.19.11 (64-bit)
Graphics Platform: X11

Comment 1 imaginator 2022-09-30 18:30:39 UTC

The problem also exists in a Wayland session. But the freeze is not so severe as with X. The programs and the desktop are still responsive and to a certain degree usable, LO-Writer, for instance. But after the first trial failed, it is not possible to log out via the menu or via keyboard (alt + ctrl + del). But I could initiate a reboot in Konsole.

Like in an X-session, "HiddenPreviews=6" in .config/kwinrc also works in Wayland - although the option is no longer available in Systemsettings/Monitor/Compositor.

BTW: I haven't used Plasma-Wayland for a long time but was pleasently surprised by the progress that has been made. Plasma and the programs seem/are even more responsive than in an X-session. Plasma-Wayland feels really snappy. Suspend and hibernate/resume worked (bad crash last time I tried). And except for one real bummer the glitches I have encountered so far were minor and would be no real problem for me until ironed out.

The bummer, however, is of course that the session can not be saved and restored. That came totally unexpected. Really a pity and - as I see it - a big obstacle to a wider adoption of Plasma-Wayland until solved.