SUMMARY kwin crashes sometimes either upon locking and turning monitors off, or turning monitors back on after returning from being away long enough for the environment to have locked itself per settings. STEPS TO REPRODUCE 1. Lock screen 2. Turn both monitors off 3. Hear error chime 4. Turn displays back on and unlock session OBSERVED RESULT kwin crash dialog and cascaded crashes of applications such as firefox, thunderbird, and discord (flatpak) journalctl contains following line as first indication of problem: Oct 25 17:40:39 Menphina kwin_wayland[45394]: unknown active output EXPECTED RESULT application windows as they were when I locked the system SOFTWARE/OS VERSIONS Linux/KDE Plasma: Arch Linux (sync Oct 25 2025 ~12 PM US Eastern) KDE Plasma Version: 6.5.0 KDE Frameworks Version: 6.19.0 Qt Version: 6.10.0 ADDITIONAL INFORMATION This has been a long-running off and on issue for me where for my system with a 60 minute screen lock and I turn both monitors off when I step away. KDE 6.4 seemed to be pretty good about not triggering the issue but 6.5 has seen a return in frequency of this issue. Please let me know if there's any information I've overlooked including as this is my first time opening an issue. qdbus6 output paste: https://invent.kde.org/-/snippets/3573 coredump bt: Program terminated with signal SIGABRT, Aborted. #0 0x00007f8a5c09894c in ?? () from /usr/lib/libc.so.6 [Current thread is 1 (Thread 0x7f8a55a06400 (LWP 45394))] (gdb) bt #0 0x00007f8a5c09894c in ?? () from /usr/lib/libc.so.6 #1 0x00007f8a5c03e410 in raise () from /usr/lib/libc.so.6 #2 0x00007f8a5fad1e57 in KCrash::defaultCrashHandler(int) () from /usr/lib/libKF6Crash.so.6 #3 <signal handler called> #4 0x00007f8a5c09894c in ?? () from /usr/lib/libc.so.6 #5 0x00007f8a5c03e410 in raise () from /usr/lib/libc.so.6 #6 0x00007f8a5c02557a in abort () from /usr/lib/libc.so.6 #7 0x00007f8a5c89348c in ?? () from /usr/lib/libQt6Core.so.6 #8 0x00007f8a5c894250 in QMessageLogger::fatal(char const*, ...) const () from /usr/lib/libQt6Core.so.6 #9 0x00007f8a5f35c8fa in ?? () from /usr/lib/libkwin.so.6 #10 0x00007f8a5f37b5ce in KWin::Workspace::takeActivity(KWin::Window*, QFlags<KWin::Workspace::ActivityFlag>) () from /usr/lib/libkwin.so.6 #11 0x00007f8a5f37bbdb in KWin::Workspace::activateNextWindow(KWin::Window*) () from /usr/lib/libkwin.so.6 #12 0x00007f8a5f6106aa in KWin::Workspace::removeWaylandWindow(KWin::Window*) () from /usr/lib/libkwin.so.6 #13 0x00007f8a5c9d716f in ?? () from /usr/lib/libQt6Core.so.6 #14 0x00007f8a5f5d9e0b in KWin::WaylandServer::windowRemoved(KWin::Window*) () from /usr/lib/libkwin.so.6 #15 0x00007f8a5f49bd67 in ?? () from /usr/lib/libkwin.so.6 #16 0x00007f8a5c9d716f in ?? () from /usr/lib/libQt6Core.so.6 #17 0x00007f8a5f61ed1b in KWin::Workspace::outputRemoved(KWin::Output*) () from /usr/lib/libkwin.so.6 #18 0x00007f8a5f6170cf in KWin::Workspace::updateOutputs(std::optional<QList<KWin::Output*> > const&) () from /usr/lib/libkwin.so.6 #19 0x00007f8a5f60edcd in KWin::Workspace::applyOutputConfiguration(KWin::OutputConfiguration&, std::optional<QList<KWin::Output*> > const&) () from /usr/lib/libkwin.so.6 #20 0x00007f8a5f60f0fe in KWin::Workspace::updateOutputConfiguration() () from /usr/lib/libkwin.so.6 #21 0x00007f8a5f6101a0 in KWin::Workspace::slotOutputBackendOutputsQueried() () from /usr/lib/libkwin.so.6 #22 0x00007f8a5c9d716f in ?? () from /usr/lib/libQt6Core.so.6 #23 0x00007f8a5f682d30 in KWin::DrmBackend::updateOutputs() () from /usr/lib/libkwin.so.6 #24 0x00007f8a5f684967 in KWin::DrmBackend::handleUdevEvent() () from /usr/lib/libkwin.so.6 #25 0x00007f8a5c9d716f in ?? () from /usr/lib/libQt6Core.so.6 #26 0x00007f8a5c9e1c40 in QSocketNotifier::event(QEvent*) () from /usr/lib/libQt6Core.so.6 #27 0x00007f8a5db020a0 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /usr/lib/libQt6Widgets.so.6 #28 0x00007f8a5c96a6c8 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib/libQt6Core.so.6 #29 0x00007f8a5cb2f049 in QEventDispatcherUNIXPrivate::activateSocketNotifiers() () from /usr/lib/libQt6Core.so.6 #30 0x00007f8a5cb2fb6c in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt6Core.so.6 #31 0x00007f8a5d734773 in QUnixEventDispatcherQPA::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt6Gui.so.6 #32 0x00007f8a5c975a86 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt6Core.so.6 #33 0x00007f8a5c96f171 in QCoreApplication::exec() () from /usr/lib/libQt6Core.so.6 #34 0x000055cee0b909e4 in ?? () #35 0x00007f8a5c027675 in ?? () from /usr/lib/libc.so.6 #36 0x00007f8a5c027729 in __libc_start_main () from /usr/lib/libc.so.6 #37 0x000055cee0b96eb5 in ?? ()
I can confirm this issue (although i'm not sure it started with 6.5 (i think it was a couple of days before), it for sure became worse with it (i only had crash on wake up before)) I'm getting kwin_wayland crashes on start (i have auto login + auto lock set up) & on lock wake (sleep disabled) Worth noting, i'm on a multi monitor setup (i think it's part of the issue). Although i'm not certain they're exactly the same issue (start vs wake), i'm seeing the same behaviour, lockscreen is frozen and not even loginctl unlock-session in another tty helps unfreezing it (i'm sure i tried restarting plasmashell after unlocking the session) i seen some mention online & from previous issues i've had with it that it might be related to Night Light, from a quick testing, disabling it appears to solve crashes I can provide more logs/specs if needed
I can also confirm this. Kwin crashes when the PC suspends/turns off the displays. To reproduce: Locking the screen and pressing Esc to turn off the displays, waking it flashes the lockscreen, turns black for a second and then shows the lockscreen again. After logging in, kwin tells me it crashed. I have 3 monitors, nightlight was not active. Also crashes when night light is turned off fully. Sometimes I get notifications that a display reconnects, so my guess is, the displays disconnect on wake and immediately reconnect. journalctl logs shows this: ``` Okt 26 15:17:28 Vanillarch kwin_wayland[60192]: Failed to delay sleep: Sender is not authorized to send message Okt 26 15:17:28 Vanillarch kwin_wayland[60192]: Failed to delay sleep: Sender is not authorized to send message Okt 26 15:17:28 Vanillarch kwin_wayland[60192]: Failed to delay sleep: Sender is not authorized to send message Okt 26 15:17:48 Vanillarch kwin_wayland[60192]: unknown active output Okt 26 15:17:48 Vanillarch kwin_wayland_wrapper[60192]: KCrash: Application 'kwin_wayland' crashing... crashRecursionCounter = 2 ```
Correcting myself on what i said earlier, disabling night light did not fix crashes, although it seems to have made crashes less "hard" (instead of freezing on the lockscreen, kwin_wayland crashes but restarts by itself), I'm not certain it's really what really helped, i did have a bump of libdrm from 2.4.126 to 2.4.127 which seems more likely to be the reason for the crash on wake i've seen either lines: plasmashell[1385]: KWaylandBackend: no output modes available anymore, this seems like a compositor bug & kwin_wayland[1160]: unknown active output
I'm experiencing an issue related to session locking. Initially, I thought it was due to session locking itself, but I later realized that the issue only occurs when the screen is set to turn off. When I disabled screen power-off, the issue no longer appeared. Additionally, I see an "kwin_wayland[26256]: unknown active output" message in the logs. I’m not using the Night Light feature, and the system crashes intermittently. Instead of freezing on the lock screen, kwin crashes and automatically restarts. However, after unlocking the screen, the entire display session is wiped, and I get an error when attempting to open the Power Management window. STEPS TO REPRODUCE 1. Lock the session. 2. Allow the system to turn off the screen. 3. Try to unlock the session after the screen turns off. EXPECTED BEHAVIOR: * The screen should unlock without any crashes or session wipes. * The Power Management window should open without errors. ACTUAL BEHAVIOR: * The display session is wiped after unlocking the screen (all applications are closed, no tray non-default tray icons are visible, etc). * I get an error when trying to access the Power Management window. * kwin crashes with "kwin_wayland[26256]: unknown active output" log message ADDITIONAL INFORMATION: * Night Light is not enabled. * The issue seems resolved by disabling screen power-off. * The system is up to date. SYSTEM INFORMATION: * OS: CachyOS x86_64 * Kernel: Linux 6.17.5-2-cachyos * Packages: 1837 (pacman) * Shell: fish 4.1.2 * Display (HWV2402): 1920x1080 in 24", 60 Hz [External] * * Display (HWV2402): 1920x1080 in 24", 60 Hz [External] * Display (HWV2402): 1920x1080 in 24", 60 Hz [External] * DE: KDE Plasma 6.5.0 * WM: KWin (Wayland) * WM Theme: Breeze * Theme: Breeze (Dark) [Qt], Breeze-Dark [GTK2], Breeze [GTK3/4] * Icons: breeze-dark [Qt], breeze-dark [GTK2/3/4] * Font: Noto Sans (10pt) [Qt], Noto Sans (10pt) [GTK2/3/4] * Cursor: breeze (24px) * Terminal: konsole 25.8.2 * CPU: AMD Ryzen 9 7950X (32) @ 5.88 GHz * GPU: AMD Radeon RX 7900 XTX [Discrete] * Memory: 62.39 GiB * Swap: 62.39 GiB
*** This bug has been marked as a duplicate of bug 495702 ***