Application: kwin_x11 (5.4.2)

Qt Version: 5.4.2
Operating System: Linux 4.2.0-16-generic x86_64
Distribution: Ubuntu 15.10

-- Information about the crash:
- What I was doing when the application crashed:

Laptop: Thinkpad X230 with Kubuntu 15.10

I hit Fn+F7 to switch output from laptop display to external VGA monitor. Each time I switch, KWin crashes and the taskbar disappears.

The crash can be reproduced every time.

-- Backtrace:
Application: KWin (kwin_x11), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f8825476840 (LWP 1387))]

Thread 5 (Thread 0x7f880e2bf700 (LWP 1400)):
#0  0x00007f8824f5d8dd in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f88230c4bd2 in ?? () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
#2  0x00007f88230c674f in xcb_wait_for_event () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
#3  0x00007f880ef70a39 in QXcbEventReader::run (this=0x7f3b30) at qxcbconnection.cpp:1105
#4  0x00007f882337e2be in QThreadPrivate::start (arg=0x7f3b30) at thread/qthread_unix.cpp:337
#5  0x00007f88245a16aa in start_thread (arg=0x7f880e2bf700) at pthread_create.c:333
#6  0x00007f8824f68eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 4 (Thread 0x7f8806dc8700 (LWP 1439)):
#0  0x00007f8824f5f743 in select () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f88235b090f in qt_safe_select (nfds=14, fdread=fdread@entry=0x7f87f8000a78, fdwrite=fdwrite@entry=0x7f87f8000d08, fdexcept=fdexcept@entry=0x7f87f8000f98, orig_timeout=orig_timeout@entry=0x0) at kernel/qcore_unix.cpp:75
#2  0x00007f88235b240e in QEventDispatcherUNIX::select (timeout=0x0, exceptfds=0x7f87f8000f98, writefds=0x7f87f8000d08, readfds=0x7f87f8000a78, nfds=<optimized out>, this=0x7f87f80008c0) at kernel/qeventdispatcher_unix.cpp:320
#3  QEventDispatcherUNIXPrivate::doSelect (this=this@entry=0x7f87f80008e0, flags=..., flags@entry=..., timeout=timeout@entry=0x0) at kernel/qeventdispatcher_unix.cpp:196
#4  0x00007f88235b293e in QEventDispatcherUNIX::processEvents (this=0x7f87f80008c0, flags=...) at kernel/qeventdispatcher_unix.cpp:607
#5  0x00007f882355b75a in QEventLoop::exec (this=this@entry=0x7f8806dc7d60, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#6  0x00007f88233793d4 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:503
#7  0x00007f881dee7f85 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#8  0x00007f882337e2be in QThreadPrivate::start (arg=0xa12680) at thread/qthread_unix.cpp:337
#9  0x00007f88245a16aa in start_thread (arg=0x7f8806dc8700) at pthread_create.c:333
#10 0x00007f8824f68eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 3 (Thread 0x7f87fe078700 (LWP 1452)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007f882250e114 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#2  0x00007f882250e159 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#3  0x00007f88245a16aa in start_thread (arg=0x7f87fe078700) at pthread_create.c:333
#4  0x00007f8824f68eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 2 (Thread 0x7f87fe879700 (LWP 3248)):
#0  0x00007ffdf45be949 in ?? ()
#1  0x00007ffdf45bec75 in clock_gettime ()
#2  0x00007f8824f7738d in __GI___clock_gettime (clock_id=<optimized out>, tp=tp@entry=0x7f87fe878b20) at ../sysdeps/unix/clock_gettime.c:115
#3  0x00007f882342f3a6 in qt_clock_gettime (ts=0x7f87fe878b20, clock=<optimized out>) at tools/qelapsedtimer_unix.cpp:105
#4  do_gettime (frac=<synthetic pointer>, sec=<synthetic pointer>) at tools/qelapsedtimer_unix.cpp:161
#5  qt_gettime () at tools/qelapsedtimer_unix.cpp:170
#6  0x00007f88235b2d29 in QTimerInfoList::updateCurrentTime (this=this@entry=0x7f87f4001118) at kernel/qtimerinfo_unix.cpp:84
#7  0x00007f88235b210b in QEventDispatcherUNIXPrivate::doSelect (this=this@entry=0x7f87f40008e0, flags=..., flags@entry=..., timeout=timeout@entry=0x0) at kernel/qeventdispatcher_unix.cpp:171
#8  0x00007f88235b293e in QEventDispatcherUNIX::processEvents (this=0x7f87f40008c0, flags=...) at kernel/qeventdispatcher_unix.cpp:607
#9  0x00007f882355b75a in QEventLoop::exec (this=this@entry=0x7f87fe878d60, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#10 0x00007f88233793d4 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:503
#11 0x00007f881dee7f85 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#12 0x00007f882337e2be in QThreadPrivate::start (arg=0x12629f0) at thread/qthread_unix.cpp:337
#13 0x00007f88245a16aa in start_thread (arg=0x7f87fe879700) at pthread_create.c:333
#14 0x00007f8824f68eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7f8825476840 (LWP 1387)):
[KCrash Handler]
#6  QScreen::handle (this=0x0) at kernel/qscreen.cpp:85
#7  0x00007f880ef872e5 in QXcbWindow::QXcbWindow (this=0x1bf8050, window=0x134e910) at qxcbwindow.cpp:260
#8  0x00007f880ef742c1 in QXcbIntegration::createPlatformWindow (this=<optimized out>, window=0x134e910) at qxcbintegration.cpp:194
#9  0x00007f8823884e6c in QWindowPrivate::create (this=0x134ff00, recursive=recursive@entry=false) at kernel/qwindow.cpp:395
#10 0x00007f882388504b in QWindow::create (this=this@entry=0x134e910) at kernel/qwindow.cpp:546
#11 0x00007f88238851f8 in QWindow::winId (this=0x134e910) at kernel/qwindow.cpp:565
#12 0x00007f8824b35a5f in KWin::AbstractThumbnailItem::findParentEffectWindow (this=0x19389b0) at ../thumbnailitem.cpp:83
#13 0x00007f8824b35c29 in KWin::AbstractThumbnailItem::effectWindowAdded (this=0x19389b0) at ../thumbnailitem.cpp:94
#14 0x00007f8824bc4b35 in KWin::AbstractThumbnailItem::qt_static_metacall (_o=_o@entry=0x19389b0, _c=_c@entry=QMetaObject::InvokeMetaMethod, _id=_id@entry=8, _a=_a@entry=0x7ffdf458aca0) at moc_thumbnailitem.cpp:130
#15 0x00007f882358e78a in QMetaObject::activate (sender=0x1215b60, signalOffset=<optimized out>, local_signal_index=local_signal_index@entry=6, argv=argv@entry=0x7ffdf458aca0) at kernel/qobject.cpp:3717
#16 0x00007f882358ef87 in QMetaObject::activate (sender=<optimized out>, m=m@entry=0x7f8822d37ac0 <KWin::EffectsHandler::staticMetaObject>, local_signal_index=local_signal_index@entry=6, argv=argv@entry=0x7ffdf458aca0) at kernel/qobject.cpp:3582
#17 0x00007f8822b28b22 in KWin::EffectsHandler::windowAdded (this=<optimized out>, _t1=0x1b4c890) at moc_kwineffects.cpp:1236
#18 0x00007f882358e617 in QtPrivate::QSlotObjectBase::call (a=0x7ffdf458ade0, r=0x1215b60, this=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qobject_impl.h:124
#19 QMetaObject::activate (sender=sender@entry=0x1c05dc0, signalOffset=<optimized out>, local_signal_index=local_signal_index@entry=7, argv=argv@entry=0x7ffdf458ade0) at kernel/qobject.cpp:3702
#20 0x00007f882358ef87 in QMetaObject::activate (sender=sender@entry=0x1c05dc0, m=m@entry=0x7f8824e5be60 <KWin::Toplevel::staticMetaObject>, local_signal_index=local_signal_index@entry=7, argv=argv@entry=0x7ffdf458ade0) at kernel/qobject.cpp:3582
#21 0x00007f8824bc08d2 in KWin::Toplevel::windowShown (this=this@entry=0x1c05dc0, _t1=_t1@entry=0x1c05dc0) at moc_toplevel.cpp:700
#22 0x00007f8824affb27 in KWin::Toplevel::setReadyForPainting (this=this@entry=0x1c05dc0) at ../toplevel.cpp:265
#23 0x00007f8824a67160 in KWin::Client::<lambda()>::operator() (__closure=<synthetic pointer>) at ../client.cpp:1831
#24 QtPrivate::FunctorCall<QtPrivate::IndexesList<>, QtPrivate::List<>, void, KWin::Client::sendSyncRequest()::<lambda()> >::call (arg=<optimized out>, f=...) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobjectdefs_impl.h:494
#25 QtPrivate::Functor<KWin::Client::sendSyncRequest()::<lambda()>, 0>::call<QtPrivate::List<>, void> (arg=<optimized out>, f=...) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobjectdefs_impl.h:551
#26 QtPrivate::QFunctorSlotObject<KWin::Client::sendSyncRequest()::<lambda()>, 0, QtPrivate::List<>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void **, bool *) (which=<optimized out>, this_=<optimized out>, r=<optimized out>, a=<optimized out>, ret=<optimized out>) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qobject_impl.h:192
#27 0x00007f882358e617 in QtPrivate::QSlotObjectBase::call (a=0x7ffdf458aef0, r=0x1c05dc0, this=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qobject_impl.h:124
#28 QMetaObject::activate (sender=sender@entry=0x1264fa0, signalOffset=<optimized out>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x0) at kernel/qobject.cpp:3702
#29 0x00007f882358ef87 in QMetaObject::activate (sender=sender@entry=0x1264fa0, m=m@entry=0x7f88237917c0 <QTimer::staticMetaObject>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x0) at kernel/qobject.cpp:3582
#30 0x00007f8823607b10 in QTimer::timeout (this=this@entry=0x1264fa0) at .moc/moc_qtimer.cpp:192
#31 0x00007f882359b178 in QTimer::timerEvent (this=0x1264fa0, e=<optimized out>) at kernel/qtimer.cpp:247
#32 0x00007f882358f603 in QObject::event (this=0x1264fa0, e=<optimized out>) at kernel/qobject.cpp:1267
#33 0x00007f8823e2bb8c in QApplicationPrivate::notify_helper (this=this@entry=0x7e0dc0, receiver=receiver@entry=0x1264fa0, e=e@entry=0x7ffdf458b220) at kernel/qapplication.cpp:3720
#34 0x00007f8823e31230 in QApplication::notify (this=0x7ffdf458b450, receiver=0x1264fa0, e=0x7ffdf458b220) at kernel/qapplication.cpp:3503
#35 0x00007f882355df1b in QCoreApplication::notifyInternal (this=0x7ffdf458b450, receiver=0x1264fa0, event=event@entry=0x7ffdf458b220) at kernel/qcoreapplication.cpp:935
#36 0x00007f88235b409d in QCoreApplication::sendEvent (event=0x7ffdf458b220, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:228
#37 QTimerInfoList::activateTimers (this=0x8188d8) at kernel/qtimerinfo_unix.cpp:635
#38 0x00007f88235b1e40 in QEventDispatcherUNIX::activateTimers (this=this@entry=0x8109c0) at kernel/qeventdispatcher_unix.cpp:549
#39 0x00007f88235b28b6 in QEventDispatcherUNIX::processEvents (this=0x8109c0, flags=flags@entry=...) at kernel/qeventdispatcher_unix.cpp:611
#40 0x00007f880efc705d in QUnixEventDispatcherQPA::processEvents (this=<optimized out>, flags=...) at eventdispatchers/qunixeventdispatcher.cpp:62
#41 0x00007f882355b75a in QEventLoop::exec (this=this@entry=0x7ffdf458b370, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#42 0x00007f88235632cc in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1188
#43 0x00007f882387800c in QGuiApplication::exec () at kernel/qguiapplication.cpp:1510
#44 0x00007f8823e28025 in QApplication::exec () at kernel/qapplication.cpp:2956
#45 0x00007f88252314c4 in kdemain (argc=1, argv=0x7ffdf458b5b8) at ../main_x11.cpp:303
#46 0x00007f8824e82a40 in __libc_start_main (main=0x4007a0 <main(int, char**)>, argc=3, argv=0x7ffdf458b5b8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffdf458b5a8) at libc-start.c:289
#47 0x00000000004007d9 in _start ()

Possible duplicates by query: bug 353122, bug 352712, bug 350800, bug 350766, bug 350710.

Reported using DrKonqi