Bug 454099

Created attachment 149030 [details]
Stack trace produced by following these instructions: https://community.kde.org/KWin/Debugging#TL.3BDR_for_bug_reporters

SUMMARY
KWin often crashes when monitors wake up from sleep. GDB stacktrace says the crash is in KWin::Workspace::clientArea:

Thread 1 "kwin_x11" received signal SIGSEGV, Segmentation fault.
KWin::Workspace::clientArea (this=0x563633dfaaf0, opt=KWin::PlacementArea, output=<optimized out>, desktop=<optimized out>) at /usr/src/debug/kwin-5.24.4-1.fc35.x86_64/src/workspace.cpp:2288
2288	        screenArea = effectiveOutput->geometry();

STEPS TO REPRODUCE
1. Lock the screen
2. Power off both monitors / let monitors go to sleep
3. Power on both monitors / wake monitors up
Repro is inconsistent. Seems to happen most consistently after a fresh reboot.

OBSERVED RESULT
System journal indicates that kwin crashed. Desktop shows various kinds of corruption: flashing or black background, occasionally missing panels.

EXPECTED RESULT
Crash doesn't happen.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 35
(available in About System)
KDE Plasma Version: 5.24.4
KDE Frameworks Version: 5.91.0
Qt Version: 5.15.2

ADDITIONAL INFORMATION
If I remember correctly, this crash started happening when I bought a new monitor, changing my display arrangement to a 2560x1440 primary monitor and a portrait mode 1920x1080 monitor on the left side. The crash seems to be related to the primary monitor waking up, judging by observing journal output when waking up the monitors.