Application: kwin_x11 (5.12.7)

Qt Version: 5.9.5
Frameworks Version: 5.47.0
Operating System: Linux 4.15.0-39-generic x86_64
Distribution: Ubuntu 18.04.1 LTS

-- Information about the crash:
I was trying to switch between active applications. No problem doing it with the mouse or trackpad, but makes Kwin crash if I do it with the keyboard (Alt+Tab). Note that Alt+Tab normally works for me.
Active applications are Firefox, Dolphin, Konsole. Another application that was initially running, but that I closed afterwards, was System Settings (the driver manager was scanning my system). Now each time I press Alt+Tab I get a notice that KWin closed unexpectedly.

The crash can be reproduced sometimes.

-- Backtrace:
Application: KWin (kwin_x11), signal: Aborted
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f6444f4ccc0 (LWP 17256))]

Thread 5 (Thread 0x7f6420db5700 (LWP 17272)):
#0  0x00007f643d9009f3 in futex_wait_cancelable (private=<optimized out>, expected=0, futex_word=0x7f6440ea2fb8) at ../sysdeps/unix/sysv/linux/futex-internal.h:88
#1  0x00007f643d9009f3 in __pthread_cond_wait_common (abstime=0x0, mutex=0x7f6440ea2f68, cond=0x7f6440ea2f90) at pthread_cond_wait.c:502
#2  0x00007f643d9009f3 in __pthread_cond_wait (cond=0x7f6440ea2f90, mutex=0x7f6440ea2f68) at pthread_cond_wait.c:655
#3  0x00007f6440bac5f4 in  () at /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#4  0x00007f6440bac639 in  () at /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#5  0x00007f643d8fa6db in start_thread (arg=0x7f6420db5700) at pthread_create.c:463
#6  0x00007f64448ad88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 4 (Thread 0x7f64221b6700 (LWP 17271)):
#0  0x00007f64448a0cf6 in __GI_ppoll (fds=0x7f6410000d28, nfds=1, timeout=<optimized out>, sigmask=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1  0x00007f6441ca15c1 in qt_safe_poll(pollfd*, unsigned long, timespec const*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#2  0x00007f6441ca2cde in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3  0x00007f6441c4a9ea in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4  0x00007f6441a6922a in QThread::exec() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5  0x00007f643c3e66f5 in  () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#6  0x00007f6441a6e16d in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#7  0x00007f643d8fa6db in start_thread (arg=0x7f64221b6700) at pthread_create.c:463
#8  0x00007f64448ad88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 3 (Thread 0x7f64231d1700 (LWP 17270)):
#0  0x00007f643d900ed9 in futex_reltimed_wait_cancelable (private=<optimized out>, reltime=0x7f64231d0c00, expected=0, futex_word=0x5579ef477054) at ../sysdeps/unix/sysv/linux/futex-internal.h:142
#1  0x00007f643d900ed9 in __pthread_cond_wait_common (abstime=0x7f64231d0cc0, mutex=0x5579ef477000, cond=0x5579ef477028) at pthread_cond_wait.c:533
#2  0x00007f643d900ed9 in __pthread_cond_timedwait (cond=0x5579ef477028, mutex=0x5579ef477000, abstime=0x7f64231d0cc0) at pthread_cond_wait.c:667
#3  0x00007f6441a6f458 in QWaitCondition::wait(QMutex*, unsigned long) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4  0x00007f6441a6b52d in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5  0x00007f6441a6e16d in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#6  0x00007f643d8fa6db in start_thread (arg=0x7f64231d1700) at pthread_create.c:463
#7  0x00007f64448ad88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 2 (Thread 0x7f6428efd700 (LWP 17260)):
#0  0x00007f64448a0cf6 in __GI_ppoll (fds=0x7f641c00e798, nfds=1, timeout=<optimized out>, sigmask=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1  0x00007f6441ca15c1 in qt_safe_poll(pollfd*, unsigned long, timespec const*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#2  0x00007f6441ca2cde in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3  0x00007f6441c4a9ea in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4  0x00007f6441a6922a in QThread::exec() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5  0x00007f643b2b6d45 in  () at /usr/lib/x86_64-linux-gnu/libQt5DBus.so.5
#6  0x00007f6441a6e16d in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#7  0x00007f643d8fa6db in start_thread (arg=0x7f6428efd700) at pthread_create.c:463
#8  0x00007f64448ad88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 1 (Thread 0x7f6444f4ccc0 (LWP 17256)):
[KCrash Handler]
#6  0x00007f64447cae97 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#7  0x00007f64447cc801 in __GI_abort () at abort.c:79
#8  0x00007f6441a58fa7 in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#9  0x00007f642a53a254 in  () at /usr/lib/x86_64-linux-gnu/qt5/plugins/xcbglintegrations/libqxcb-glx-integration.so
#10 0x00007f642a537bb7 in  () at /usr/lib/x86_64-linux-gnu/qt5/plugins/xcbglintegrations/libqxcb-glx-integration.so
#11 0x00007f642c43f581 in QXcbIntegration::createPlatformOpenGLContext(QOpenGLContext*) const () at /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#12 0x00007f644224b01f in QOpenGLContext::create() () at /usr/lib/x86_64-linux-gnu/libQt5Gui.so.5
#13 0x00007f642a53aa10 in  () at /usr/lib/x86_64-linux-gnu/qt5/plugins/xcbglintegrations/libqxcb-glx-integration.so
#14 0x00007f642a53b051 in  () at /usr/lib/x86_64-linux-gnu/qt5/plugins/xcbglintegrations/libqxcb-glx-integration.so
#15 0x00007f643cab8455 in QSGRenderLoop::instance() () at /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#16 0x00007f643cb25b0a in QQuickWindowPrivate::init(QQuickWindow*, QQuickRenderControl*) () at /usr/lib/x86_64-linux-gnu/libQt5Quick.so.5
#17 0x00007f638f0cde9c in PlasmaQuick::Dialog::Dialog(QQuickItem*) () at /usr/lib/x86_64-linux-gnu/libKF5PlasmaQuick.so.5
#18 0x00007f638f31eff0 in  () at /usr/lib/x86_64-linux-gnu/qt5/qml/org/kde/plasma/core/libcorebindingsplugin.so
#19 0x00007f643c36b962 in QQmlType::create(QObject**, void**, unsigned long) const () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#20 0x00007f643c3dc146 in QQmlObjectCreator::createInstance(int, QObject*, bool) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#21 0x00007f643c3de3da in QQmlObjectCreator::setPropertyBinding(QQmlPropertyData const*, QV4::CompiledData::Binding const*) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#22 0x00007f643c3dee11 in QQmlObjectCreator::setupBindings(bool) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#23 0x00007f643c3dbba6 in QQmlObjectCreator::populateInstance(int, QObject*, QObject*, QQmlPropertyData const*) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#24 0x00007f643c3dc97c in QQmlObjectCreator::createInstance(int, QObject*, bool) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#25 0x00007f643c3dfc6c in QQmlObjectCreator::create(int, QObject*, QQmlInstantiationInterrupt*) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#26 0x00007f643c356408 in QQmlComponentPrivate::beginCreate(QQmlContextData*) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#27 0x00007f643c35474f in QQmlComponent::create(QQmlContext*) () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#28 0x00007f64444a6eb1 in  () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#29 0x00007f64444a848a in  () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#30 0x00007f64444a86d9 in  () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#31 0x00007f6441c7b5b5 in QMetaObject::activate(QObject*, int, int, void**) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#32 0x00007f6441c88027 in QTimer::timeout(QTimer::QPrivateSignal) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#33 0x00007f6441c88388 in QTimer::timerEvent(QTimerEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#34 0x00007f6441c7c0db in QObject::event(QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#35 0x00007f64429ca82c in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#36 0x00007f64429d20f4 in QApplication::notify(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#37 0x00007f6441c4c9a8 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#38 0x00007f6441ca4d8e in QTimerInfoList::activateTimers() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#39 0x00007f6441ca2f42 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#40 0x00007f642c49c5cd in  () at /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#41 0x00007f6441c4a9ea in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#42 0x00007f6441c53a84 in QCoreApplication::exec() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#43 0x00007f6444b85dbb in kdemain () at /usr/lib/x86_64-linux-gnu/libkdeinit5_kwin_x11.so
#44 0x00007f64447adb97 in __libc_start_main (main=0x5579edc05730, argc=3, argv=0x7fff772d1bc8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff772d1bb8) at ../csu/libc-start.c:310
#45 0x00005579edc0576a in _start ()

Reported using DrKonqi