Application: kwin (4.11.9)
KDE Platform Version: 4.13.1
Qt Version: 4.8.6
Operating System: Linux 3.14-1-amd64 x86_64
Distribution: Debian GNU/Linux testing (jessie)

Reproducible: Always

Steps to Reproduce:
I can make KWin crash by the following steps:

1) Right click the window title (on the window decoration)
2) Go to More actions (Swedish: "Fler åtgärder")
3) Choose Special Application Settings (Swedish: "Särskilda programinställningar")
4) Go to Tab Size and Position (Swedish: "Storlek och position")
5) Tick the Activity option (Swedish: "Aktivitet"), Remember (Swedish: "Kom ihåg") and then pick some other activity in the list.
6) Click Ok to close the window.
7) Right click the same window title again.
8) Hover over the Activity option to get a list of all the activities
9) Crash!

While writing this report I managed to reduce the number of steps required to reproduce it. I'm still including the original steps above, should the stack be different for any reason.

1) Right click the window title (on the window decoration)
2) Go to More actions (Swedish: "Fler åtgärder")
3) Choose Special Application Settings (Swedish: "Särskilda programinställningar")
4) Close the window you just opened.
5) Right click the same window title again.
6) Hover over the Activity option to get a list of all the activities
7) Crash!



-- Backtrace:
Application: Kwin (kwin), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7fc278ced900 (LWP 16119))]

Thread 3 (Thread 0x7fc250c3f700 (LWP 16130)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007fc2776d4b4b in QTWTF::TCMalloc_PageHeap::scavengerThread (this=0x7fc2779d2f00 <QTWTF::pageheap_memory>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:2359
#2  0x00007fc2776d4b89 in QTWTF::TCMalloc_PageHeap::runScavengerThread (context=<optimized out>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:1464
#3  0x00007fc27022f062 in start_thread (arg=0x7fc250c3f700) at pthread_create.c:312
#4  0x00007fc2784d0c1d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 2 (Thread 0x7fc2597b8700 (LWP 17645)):
#0  pthread_cond_timedwait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
#1  0x00007fc272753784 in wait (time=30000, this=0x13932b0) at thread/qwaitcondition_unix.cpp:84
#2  QWaitCondition::wait (this=this@entry=0x1298f40, mutex=mutex@entry=0x12f60a8, time=30000) at thread/qwaitcondition_unix.cpp:158
#3  0x00007fc27274708a in QThreadPoolThread::run (this=0x1298f30) at concurrent/qthreadpool.cpp:142
#4  0x00007fc2727532bf in QThreadPrivate::start (arg=0x1298f30) at thread/qthread_unix.cpp:349
#5  0x00007fc27022f062 in start_thread (arg=0x7fc2597b8700) at pthread_create.c:312
#6  0x00007fc2784d0c1d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 1 (Thread 0x7fc278ced900 (LWP 16119)):
[KCrash Handler]
#6  0x00007fc271bf277c in begin (this=0x1df3c98) at ../../include/QtCore/../../src/corelib/tools/qlist.h:101
#7  contains (t=@0x7fff48878128: 0x145d330, this=0x1df3c98) at ../../include/QtCore/../../src/corelib/tools/qlist.h:882
#8  QActionGroup::addAction (this=0x1e73910, a=a@entry=0x145d330) at kernel/qactiongroup.cpp:180
#9  0x00007fc278836f1c in KWin::UserActionsMenu::activityPopupAboutToShow (this=0x12de400) at ../../kwin/useractions.cpp:723
#10 0x00007fc2728696aa in QMetaObject::activate (sender=sender@entry=0x15c6a70, m=m@entry=0x7fc2726a8720 <QMenu::staticMetaObject>, local_signal_index=local_signal_index@entry=0, argv=argv@entry=0x0) at kernel/qobject.cpp:3567
#11 0x00007fc27201b690 in QMenu::aboutToShow (this=this@entry=0x15c6a70) at .moc/release-shared/moc_qmenu.cpp:164
#12 0x00007fc27201e5ad in QMenu::popup (this=0x15c6a70, p=..., atAction=atAction@entry=0x0) at widgets/qmenu.cpp:1843
#13 0x00007fc27201fbeb in QMenu::internalDelayedPopup (this=this@entry=0x1db6b40) at widgets/qmenu.cpp:3063
#14 0x00007fc272021664 in QMenu::timerEvent (this=0x1db6b40, e=<optimized out>) at widgets/qmenu.cpp:2923
#15 0x00007fc27286d861 in QObject::event (this=this@entry=0x1db6b40, e=e@entry=0x7fff488789a0) at kernel/qobject.cpp:1184
#16 0x00007fc271c44d1b in QWidget::event (this=this@entry=0x1db6b40, event=event@entry=0x7fff488789a0) at kernel/qwidget.cpp:8859
#17 0x00007fc272023d0b in QMenu::event (this=0x1db6b40, e=0x7fff488789a0) at widgets/qmenu.cpp:2480
#18 0x00007fc271bf56cc in QApplicationPrivate::notify_helper (this=this@entry=0x1172160, receiver=receiver@entry=0x1db6b40, e=e@entry=0x7fff488789a0) at kernel/qapplication.cpp:4570
#19 0x00007fc271bfbcfd in QApplication::notify (this=this@entry=0x7fff488799d0, receiver=receiver@entry=0x1db6b40, e=e@entry=0x7fff488789a0) at kernel/qapplication.cpp:4356
#20 0x00007fc2771238da in KApplication::notify (this=0x7fff488799d0, receiver=0x1db6b40, event=0x7fff488789a0) at ../../kdeui/kernel/kapplication.cpp:311
#21 0x00007fc27285541d in QCoreApplication::notifyInternal (this=0x7fff488799d0, receiver=0x1db6b40, event=0x7fff488789a0) at kernel/qcoreapplication.cpp:953
#22 0x00007fc272885133 in sendEvent (event=<optimized out>, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#23 QTimerInfoList::activateTimers (this=0x1172bd8) at kernel/qeventdispatcher_unix.cpp:621
#24 0x00007fc2728851b0 in QEventDispatcherUNIX::activateTimers (this=this@entry=0x1102b30) at kernel/qeventdispatcher_unix.cpp:878
#25 0x00007fc272885b30 in QEventDispatcherUNIX::processEvents (this=this@entry=0x1102b30, flags=...) at kernel/qeventdispatcher_unix.cpp:940
#26 0x00007fc271c940e6 in QEventDispatcherX11::processEvents (this=0x1102b30, flags=...) at kernel/qeventdispatcher_x11.cpp:152
#27 0x00007fc272853fef in QEventLoop::processEvents (this=this@entry=0x7fff48878cf0, flags=...) at kernel/qeventloop.cpp:149
#28 0x00007fc2728542e5 in QEventLoop::exec (this=this@entry=0x7fff48878cf0, flags=...) at kernel/qeventloop.cpp:204
#29 0x00007fc272022a77 in QMenu::exec (this=0x1db6b40, p=..., action=action@entry=0x0) at widgets/qmenu.cpp:2124
#30 0x00007fc27883380a in KWin::UserActionsMenu::show (this=0x12de400, pos=..., cl=...) at ../../kwin/useractions.cpp:167
#31 0x00007fc2788338cb in KWin::Workspace::showWindowMenu (this=0x12f4b50, pos=..., cl=0x14cccc0) at ../../kwin/useractions.cpp:1827
#32 0x00007fc278828042 in KWin::Bridge::showWindowMenu (this=0x140d250, p=..., id=<optimized out>) at ../../kwin/bridge.cpp:110
#33 0x00007fc259e286ee in Oxygen::Client::mousePressEvent (this=0x1305000, event=0x7fff48879260) at ../../../../kwin/clients/oxygen/oxygenclient.cpp:1669
#34 0x00007fc259e31c6a in Oxygen::Client::eventFilter (this=0x1305000, object=0x12b7b10, event=0x7fff48879260) at ../../../../kwin/clients/oxygen/oxygenclient.cpp:1358
#35 0x00007fc272855586 in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=this@entry=0x1172160, receiver=receiver@entry=0x12b7b10, event=event@entry=0x7fff48879260) at kernel/qcoreapplication.cpp:1063
#36 0x00007fc271bf56ac in QApplicationPrivate::notify_helper (this=this@entry=0x1172160, receiver=receiver@entry=0x12b7b10, e=e@entry=0x7fff48879260) at kernel/qapplication.cpp:4566
#37 0x00007fc271bfbe3a in QApplication::notify (this=this@entry=0x7fff488799d0, receiver=receiver@entry=0x12b7b10, e=e@entry=0x7fff48879260) at kernel/qapplication.cpp:4113
#38 0x00007fc2771238da in KApplication::notify (this=0x7fff488799d0, receiver=0x12b7b10, event=0x7fff48879260) at ../../kdeui/kernel/kapplication.cpp:311
#39 0x00007fc27285541d in QCoreApplication::notifyInternal (this=0x7fff488799d0, receiver=receiver@entry=0x12b7b10, event=event@entry=0x7fff48879260) at kernel/qcoreapplication.cpp:953
#40 0x00007fc271bfb633 in sendEvent (event=<optimized out>, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#41 QApplicationPrivate::sendMouseEvent (receiver=receiver@entry=0x12b7b10, event=event@entry=0x7fff48879260, alienWidget=alienWidget@entry=0x0, nativeWidget=nativeWidget@entry=0x12b7b10, buttonDown=buttonDown@entry=0x7fc2726d42d8 <qt_button_down>, lastMouseReceiver=..., spontaneous=spontaneous@entry=true) at kernel/qapplication.cpp:3178
#42 0x00007fc271c6d33b in QETWidget::translateMouseEvent (this=this@entry=0x12b7b10, event=event@entry=0x7fff488795e0) at kernel/qapplication_x11.cpp:4540
#43 0x00007fc271c6bdac in QApplication::x11ProcessEvent (this=0x7fff488799d0, event=event@entry=0x7fff488795e0) at kernel/qapplication_x11.cpp:3663
#44 0x00007fc271c94080 in QEventDispatcherX11::processEvents (this=0x1102b30, flags=...) at kernel/qeventdispatcher_x11.cpp:132
#45 0x00007fc272853fef in QEventLoop::processEvents (this=this@entry=0x7fff48879840, flags=...) at kernel/qeventloop.cpp:149
#46 0x00007fc2728542e5 in QEventLoop::exec (this=this@entry=0x7fff48879840, flags=...) at kernel/qeventloop.cpp:204
#47 0x00007fc272859ab9 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1225
#48 0x00007fc271bf3e8c in QApplication::exec () at kernel/qapplication.cpp:3828
#49 0x00007fc278810986 in kdemain (argc=3, argv=0x7fff48879b18) at ../../kwin/main.cpp:597
#50 0x00007fc27840cb45 in __libc_start_main (main=0x4006d0 <main(int, char**)>, argc=3, argv=0x7fff48879b18, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff48879b08) at libc-start.c:287
#51 0x00000000004006fe in _start ()


Might be a duplicate of bug 334152.