Application: kwin_x11 (5.17.80)
 (Compiled from sources)
Qt Version: 5.14.0
Frameworks Version: 5.66.0
Operating System: Linux 5.4.1-arch1-1 x86_64
Windowing system: X11
Distribution: Arch Linux

-- Information about the crash:
git master of today, haven't investigated further, thought I'd post as-is anyway.

-- Backtrace:
Application: KWin (kwin_x11), signal: Aborted
Using host libthread_db library "/usr/lib/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f55490c6880 (LWP 9534))]

Thread 4 (Thread 0x7f5533027700 (LWP 9551)):
#0  0x00007f554f667c45 in pthread_cond_wait@@GLIBC_2.3.2 () at /usr/lib/libpthread.so.0
#1  0x00007f55336495fc in  () at /usr/lib/dri/i965_dri.so
#2  0x00007f55336491f8 in  () at /usr/lib/dri/i965_dri.so
#3  0x00007f554f6614cf in start_thread () at /usr/lib/libpthread.so.0
#4  0x00007f554d4542d3 in clone () at /usr/lib/libc.so.6

Thread 3 (Thread 0x7f5541e41700 (LWP 9548)):
#0  0x00007f554d449ae6 in ppoll () at /usr/lib/libc.so.6
#1  0x00007f554dc49ad8 in qt_ppoll(pollfd*, nfds_t, timespec const*) (fds=0x7f5538000d38, nfds=1, timeout_ts=0x0) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qcore_unix.cpp:132
#2  0x00007f554dc49b1c in qt_safe_poll(pollfd*, unsigned long, timespec const*) (fds=0x7f5538000d38, nfds=1, timeout_ts=0x0) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qcore_unix.cpp:155
#3  0x00007f554dc4b502 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f5538000b60, flags=...) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qeventdispatcher_unix.cpp:500
#4  0x00007f554dbb79e9 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f5541e40ce0, flags=...) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qeventloop.cpp:138
#5  0x00007f554dbb7d23 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f5541e40ce0, flags=...) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qeventloop.cpp:225
#6  0x00007f554d94bfd4 in QThread::exec() (this=0x55f9c2da3260) at /home/david/projects/qt/src/qtbase/src/corelib/thread/qthread.cpp:536
#7  0x00007f5550df73a3 in QQmlThreadPrivate::run() (this=0x55f9c2da3260) at /home/david/projects/qt/src/qtdeclarative/src/qml/qml/ftw/qqmlthread.cpp:155
#8  0x00007f554d94ee91 in QThreadPrivate::start(void*) (arg=0x55f9c2da3260) at /home/david/projects/qt/src/qtbase/src/corelib/thread/qthread_unix.cpp:342
#9  0x00007f554f6614cf in start_thread () at /usr/lib/libpthread.so.0
#10 0x00007f554d4542d3 in clone () at /usr/lib/libc.so.6

Thread 2 (Thread 0x7f5543d07700 (LWP 9539)):
#0  0x00007f554dc4d449 in QVector<pollfd>::capacity() const (this=0x7f553c000bf0) at ../../include/QtCore/../../../../src/qtbase/src/corelib/tools/qvector.h:94
#1  0x00007f554dc4c102 in QVector<pollfd>::reserve(int) (this=0x7f553c000bf0, asize=1) at ../../include/QtCore/../../../../src/qtbase/src/corelib/tools/qvector.h:427
#2  0x00007f554dc4b3f5 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f553c000b60, flags=...) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qeventdispatcher_unix.cpp:489
#3  0x00007f554dbb79e9 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f5543d06cb0, flags=...) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qeventloop.cpp:138
#4  0x00007f554dbb7d23 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7f5543d06cb0, flags=...) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qeventloop.cpp:225
#5  0x00007f554d94bfd4 in QThread::exec() (this=0x7f554f505dc0 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at /home/david/projects/qt/src/qtbase/src/corelib/thread/qthread.cpp:536
#6  0x00007f554f44a379 in QDBusConnectionManager::run() (this=0x7f554f505dc0 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at /home/david/projects/qt/src/qtbase/src/dbus/qdbusconnection.cpp:179
#7  0x00007f554d94ee91 in QThreadPrivate::start(void*) (arg=0x7f554f505dc0 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at /home/david/projects/qt/src/qtbase/src/corelib/thread/qthread_unix.cpp:342
#8  0x00007f554f6614cf in start_thread () at /usr/lib/libpthread.so.0
#9  0x00007f554d4542d3 in clone () at /usr/lib/libc.so.6

Thread 1 (Thread 0x7f55490c6880 (LWP 9534)):
[KCrash Handler]
#6  0x00007f554d390f25 in raise () at /usr/lib/libc.so.6
#7  0x00007f554d37a897 in abort () at /usr/lib/libc.so.6
#8  0x00007f554d943dc8 in qt_message_fatal(QtMsgType, QMessageLogContext const&, QString const&) (context=..., message=...) at /home/david/projects/qt/src/qtbase/src/corelib/global/qlogging.cpp:1894
#9  0x00007f554d940406 in QMessageLogger::fatal(char const*, ...) const (this=0x7ffc72d8b9e0, msg=0x7f554dcf6d48 "ASSERT: \"%s\" in file %s, line %d") at /home/david/projects/qt/src/qtbase/src/corelib/global/qlogging.cpp:893
#10 0x00007f554d936ba8 in qt_assert(char const*, char const*, int) (assertion=0x7f555261fbd9 "m_scene->hasSwapEvent() ^ !m_bufferSwapPending", file=0x7f555261f9f6 "/home/david/projects/kde5/src/kde/workspace/kwin/composite.cpp", line=694) at /home/david/projects/qt/src/qtbase/src/corelib/global/qglobal.cpp:3342
#11 0x00007f555233b50c in KWin::Compositor::performCompositing() (this=0x55f9c2c027a0) at /home/david/projects/kde5/src/kde/workspace/kwin/composite.cpp:694
#12 0x00007f555233c81a in KWin::X11Compositor::performCompositing() (this=0x55f9c2c027a0) at /home/david/projects/kde5/src/kde/workspace/kwin/composite.cpp:911
#13 0x00007f555233ae2b in KWin::Compositor::bufferSwapComplete() (this=0x55f9c2c027a0) at /home/david/projects/kde5/src/kde/workspace/kwin/composite.cpp:595
#14 0x00007f55434b7611 in KWin::SwapEventFilter::event(xcb_generic_event_t*) (this=0x55f9c30c47d0, event=0x7f554400f9a0) at /home/david/projects/kde5/src/kde/workspace/kwin/plugins/platforms/x11/standalone/glxbackend.cpp:95
#15 0x00007f55523c9bd4 in KWin::Workspace::workspaceEvent(xcb_generic_event_t*) (this=0x55f9c2c8e5f0, e=0x7f554400f9a0) at /home/david/projects/kde5/src/kde/workspace/kwin/events.cpp:240
#16 0x00007f555245dfd0 in KWin::XcbEventFilter::nativeEventFilter(QByteArray const&, void*, long*) (this=0x55f9c2bfd800, eventType=..., message=0x7f554400f9a0, result=0x7ffc72d8bfe0) at /home/david/projects/kde5/src/kde/workspace/kwin/main.cpp:414
#17 0x00007f554dbb4ff2 in QAbstractEventDispatcher::filterNativeEvent(QByteArray const&, void*, long*) (this=0x55f9c2beafa0, eventType=..., message=0x7f554400f9a0, result=0x7ffc72d8bfe0) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qabstracteventdispatcher.cpp:488
#18 0x00007f5548f1b963 in QXcbConnection::handleXcbEvent(xcb_generic_event_t*) (this=0x55f9c2bad820, event=0x7f554400f9a0) at /home/david/projects/qt/src/qtbase/src/plugins/platforms/xcb/qxcbconnection.cpp:550
#19 0x00007f5548f1ddb2 in QXcbConnection::processXcbEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x55f9c2bad820, flags=...) at /home/david/projects/qt/src/qtbase/src/plugins/platforms/xcb/qxcbconnection.cpp:1029
#20 0x00007f5548f61772 in QXcbUnixEventDispatcher::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x55f9c2beafa0, flags=...) at /home/david/projects/qt/src/qtbase/src/plugins/platforms/xcb/qxcbeventdispatcher.cpp:61
#21 0x00007f554dbb79e9 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7ffc72d8c320, flags=...) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qeventloop.cpp:138
#22 0x00007f554dbb7d23 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x7ffc72d8c320, flags=...) at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qeventloop.cpp:225
#23 0x00007f554dbbbb5c in QCoreApplication::exec() () at /home/david/projects/qt/src/qtbase/src/corelib/kernel/qcoreapplication.cpp:1400
#24 0x00007f554e0f39ac in QGuiApplication::exec() () at /home/david/projects/qt/src/qtbase/src/gui/kernel/qguiapplication.cpp:1845
#25 0x00007f554e9b5ec9 in QApplication::exec() () at /home/david/projects/qt/src/qtbase/src/widgets/kernel/qapplication.cpp:2833
#26 0x00007f5552764c40 in kdemain(int, char**) (argc=3, argv=0x7ffc72d8c718) at /home/david/projects/kde5/src/kde/workspace/kwin/main_x11.cpp:483
#27 0x000055f9c1c7a192 in main(int, char**) (argc=3, argv=0x7ffc72d8c718) at kwin_x11_dummy.cpp:3
[Inferior 1 (process 9534) detached]

Possible duplicates by query: bug 415750, bug 415078, bug 414922, bug 413943, bug 412008.

Reported using DrKonqi