Bug 511403 - Crash disconnecting monitors: Workspace::setActiveOutput "unknown active output"
Summary: Crash disconnecting monitors: Workspace::setActiveOutput "unknown active output"
Status: RESOLVED DUPLICATE of bug 495702
Alias: None
Product: kwin
Classification: Plasma
Component: wayland-generic (other bugs)
Version First Reported In: unspecified
Platform: Other Linux
: NOR crash
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-10-31 00:23 UTC by Thiago Macieira
Modified: 2025-10-31 12:00 UTC (History)
1 user (show)

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Version Fixed/Implemented In:
Sentry Crash Report:

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Description Thiago Macieira 2025-10-31 00:23:13 UTC 
SUMMARY
When disconnecting a dock station that had two monitors connected, kwin crashed with
        qFatal("unknown active output");

in Workspace::setActiveOutput().

STEPS TO REPRODUCE
1. Connect two monitors to a dock station and the dockstation to the computer
2. Ensure all three screens are active
3. (Unsure if necessary) Lock the screen
4. Disconnect the dock station

I don't know what exactly caused the issue. It's probably related to the order in which the outputs are disconnected by the OS/HW and how the events are delivered. I have disconnected the dock station before with the two monitors without observing this issue.

OBSERVED RESULT
kwin crashed

EXPECTED RESULT
kwin does not crash

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:
KDE Plasma Version: 6.5.0
KDE Frameworks Version: 6.19.0
Qt Version: 6.10.0
openSUSE Tumbleweed builds

ADDITIONAL INFORMATION
Backtrace:
#5  0x00007f933f2427b6 in raise () at /lib64/libc.so.6
#6  0x00007f933f22934b in abort () at /lib64/libc.so.6
#7  0x00007f933faf65e7 in qAbort () at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/global/qassert.cpp:46
#8  qt_maybe_message_fatal<QString&> (msgType=QtFatalMsg, context=<optimized out>, message=...)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/global/qlogging.cpp:2165
#9  qt_message(QtMsgType, const QMessageLogContext &, const char *, typedef __va_list_tag __va_list_tag *)
    (msgType=msgType@entry=QtFatalMsg, context=..., msg=msg@entry=0x7f9342ef613b "unknown active output", ap=ap@entry=0x7ffe6c251248)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/global/qlogging.cpp:412
#10 0x00007f933faf720d in QMessageLogger::fatal (this=this@entry=0x7ffe6c251480, msg=msg@entry=0x7f9342ef613b "unknown active output")
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/global/qlogging.cpp:901
#11 0x00007f9342a04f8c in KWin::Workspace::setActiveOutput (this=<optimized out>, output=<optimized out>) at /usr/src/debug/kwin-6.5.0/src/workspace.cpp:2441
#12 KWin::Workspace::setActiveOutput (this=<optimized out>, output=<optimized out>) at /usr/src/debug/kwin-6.5.0/src/workspace.cpp:2438
#13 0x00007f9342a92eb4 in KWin::Workspace::takeActivity (this=0x5622fb63ad70, window=<optimized out>, flags=...) at /usr/src/debug/kwin-6.5.0/src/activation.cpp:423
#14 0x00007f9342a98c2a in KWin::Workspace::activateNextWindow (this=0x5622fb63ad70, window=0x5622fffcb680) at /usr/src/debug/kwin-6.5.0/src/activation.cpp:516
#15 0x00007f9342d13082 in KWin::Workspace::removeWaylandWindow (this=0x5622fb63ad70, window=0x5622fffcb680) at /usr/src/debug/kwin-6.5.0/src/workspace.cpp:813
#16 0x00007f933fc4c6d3 in QtPrivate::QSlotObjectBase::call (this=0x5622fb699750, r=0x5622fb63ad70, a=0x7ffe6c251720)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qobjectdefs_impl.h:461
#17 doActivate<false> (sender=0x5622fa4c46b0, signal_index=4, argv=0x7ffe6c251720) at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qobject.cpp:4255
#18 0x00007f9342cde6f7 in QMetaObject::activate<void, KWin::Window*>
    (sender=<optimized out>, mo=<optimized out>, local_signal_index=1, ret=0x0, sender=<optimized out>, mo=<optimized out>, local_signal_index=<optimized out>, ret=<optimized out>) at /usr/include/qt6/QtCore/qobjectdefs.h:319
#19 KWin::WaylandServer::windowRemoved (this=<optimized out>, _t1=<optimized out>) at /usr/src/debug/kwin-6.5.0/build/src/kwin_autogen/include/moc_wayland_server.cpp:155
#20 0x00007f9342ba9758 in KWin::LayerShellV1Window::destroyWindow (this=0x5622fffcb680) at /usr/src/debug/kwin-6.5.0/src/layershellv1window.cpp:213
#21 0x00007f933fc4c6d3 in QtPrivate::QSlotObjectBase::call (this=0x5622fc104930, r=0x5622fffcb680, a=0x7ffe6c2518d0)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qobjectdefs_impl.h:461
#22 doActivate<false> (sender=0x5622fb63ad70, signal_index=19, argv=0x7ffe6c2518d0) at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qobject.cpp:4255
#23 0x00007f9342d20f67 in QMetaObject::activate<void, KWin::Output*>
    (sender=<optimized out>, mo=<optimized out>, local_signal_index=16, ret=0x0, sender=<optimized out>, mo=<optimized out>, local_signal_index=<optimized out>, ret=<optimized out>) at /usr/include/qt6/QtCore/qobjectdefs.h:319
#24 KWin::Workspace::outputRemoved (this=<optimized out>, _t1=<optimized out>) at /usr/src/debug/kwin-6.5.0/build/src/kwin_autogen/include/moc_workspace.cpp:659
#25 0x00007f9342d194f5 in KWin::Workspace::updateOutputs (this=0x5622fb63ad70, outputOrder=<optimized out>) at /usr/src/debug/kwin-6.5.0/src/workspace.cpp:1228
#26 0x00007f9342d1187b in KWin::Workspace::applyOutputConfiguration (this=this@entry=0x5622fb63ad70, config=..., outputOrder=std::optional = {...})
    at /usr/src/debug/kwin-6.5.0/src/workspace.cpp:442
#27 0x00007f9342d11ba2 in KWin::Workspace::updateOutputConfiguration (this=this@entry=0x5622fb63ad70) at /usr/src/debug/kwin-6.5.0/src/workspace.cpp:511
#28 0x00007f9342d12ba9 in KWin::Workspace::slotOutputBackendOutputsQueried (this=0x5622fb63ad70) at /usr/src/debug/kwin-6.5.0/src/workspace.cpp:1148
#29 0x00007f933fc4c6d3 in QtPrivate::QSlotObjectBase::call (this=0x5622fb7785d0, r=0x5622fb63ad70, a=0x7ffe6c2523e8)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qobjectdefs_impl.h:461
#30 doActivate<false> (sender=0x5622fa4ccd20, signal_index=3, argv=0x7ffe6c2523e8) at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qobject.cpp:4255
#31 0x00007f9342d83285 in KWin::DrmBackend::updateOutputs (this=this@entry=0x5622fa4ccd20) at /usr/src/debug/kwin-6.5.0/src/backends/drm/drm_backend.cpp:303
#32 0x00007f9342d84d24 in KWin::DrmBackend::handleUdevEvent (this=0x5622fa4ccd20) at /usr/src/debug/kwin-6.5.0/src/backends/drm/drm_backend.cpp:203
#33 0x00007f933fc4c6d3 in QtPrivate::QSlotObjectBase::call (this=0x5622fa4d7430, r=0x5622fa4ccd20, a=0x7ffe6c252840)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qobjectdefs_impl.h:461
#34 doActivate<false> (sender=0x5622fa591890, signal_index=3, argv=0x7ffe6c252840) at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qobject.cpp:4255
#35 0x00007f933fc54e2d in QMetaObject::activate<void, QSocketDescriptor, QSocketNotifier::Type, QSocketNotifier::QPrivateSignal>
    (sender=<optimized out>, mo=<optimized out>, local_signal_index=<optimized out>, ret=<optimized out>)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qobjectdefs.h:319
#36 QSocketNotifier::activated (this=this@entry=0x5622fa591890, _t1=..., _t2=<optimized out>, _t3=...)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/build-x86-64-v4/src/corelib/Core_autogen/include/moc_qsocketnotifier.cpp:161
#37 0x00007f933fc55e3a in QSocketNotifier::event (this=0x5622fa591890, e=<optimized out>)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qsocketnotifier.cpp:324
#38 0x00007f9340fe7918 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /lib64/libQt6Widgets.so.6
#39 0x00007f933fbdae78 in QCoreApplication::notifyInternal2 (receiver=0x5622fa591890, event=0x7ffe6c252990)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qcoreapplication.cpp:1109
#40 0x00007f933fdabe7b in QEventDispatcherUNIXPrivate::activateSocketNotifiers (this=this@entry=0x5622fa3fd180)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qeventdispatcher_unix.cpp:276
--Type <RET> for more, q to quit, c to continue without paging--c
#41 0x00007f933fdac869 in QEventDispatcherUNIX::processEvents (this=<optimized out>, flags=...)
    at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qeventdispatcher_unix.cpp:498
#42 0x00007f9340a232e1 in QUnixEventDispatcherQPA::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /lib64/glibc-hwcaps/x86-64-v4/libQt6Gui.so.6.10.0
#43 0x00007f933fbe9fcb in QEventLoop::exec (this=0x7ffe6c252b60, flags=...) at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/global/qflags.h:77
#44 0x00007f933fbe00f4 in QCoreApplication::exec () at /usr/src/debug/qtbase-everywhere-src-6.10.0/src/corelib/kernel/qcoreapplication.cpp:1452
#45 0x00005622c4fdf8c6 in main (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/kwin-6.5.0/src/main_wayland.cpp:635
Comment 1 Zamundaaa 2025-10-31 12:00:28 UTC 

*** This bug has been marked as a duplicate of bug 495702 ***