Bug 346575

Application: kcmshell5 (5.2.2)

Qt Version: 5.4.1
Operating System: Linux 3.19.3-031903-generic x86_64
Distribution: Ubuntu 15.04

-- Information about the crash:
I only finished installing the latest Kubuntu this morning.

- What I was doing when the application crashed:
I had just adjusted my Display Configuration to fix where my monitors were located, and hit Apply, and the PC started lagging, everything was jittery, then it took awhile for the change to take effect. 

Finally, after the change took effect, the KDE Control Module crashed, the bug reporter popped up, and the desktop stopped lagging.

This actually happened to me twice, but I accidentally closed the bug report the first time.

- Unusual behavior I noticed:

The crash can be reproduced sometimes.

-- Backtrace:
Application: KDE Control Module (kcmshell5), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f816c083800 (LWP 3400))]

Thread 3 (Thread 0x7f8157a6c700 (LWP 3401)):
#0  0x00007f816bb698dd in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f8164255b72 in ?? () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
#2  0x00007f816425764f in xcb_wait_for_event () from /usr/lib/x86_64-linux-gnu/libxcb.so.1
#3  0x00007f8159990099 in QXcbEventReader::run (this=0x1034eb0) at qxcbconnection.cpp:1105
#4  0x00007f8169becb0e in QThreadPrivate::start (arg=0x1034eb0) at thread/qthread_unix.cpp:337
#5  0x00007f81696236aa in start_thread (arg=0x7f8157a6c700) at pthread_create.c:333
#6  0x00007f816bb74eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 2 (Thread 0x7f814a589700 (LWP 3405)):
#0  0x00007f816bb698dd in poll () at ../sysdeps/unix/syscall-template.S:81
#1  0x00007f8163b31ebc in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#2  0x00007f8163b31fcc in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#3  0x00007f8169e83c6c in QEventDispatcherGlib::processEvents (this=0x7f813c0008c0, flags=...) at kernel/qeventdispatcher_glib.cpp:418
#4  0x00007f8169e283e2 in QEventLoop::exec (this=this@entry=0x7f814a588da0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#5  0x00007f8169be7b44 in QThread::exec (this=<optimized out>) at thread/qthread.cpp:503
#6  0x00007f816902df65 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#7  0x00007f8169becb0e in QThreadPrivate::start (arg=0x1221290) at thread/qthread_unix.cpp:337
#8  0x00007f81696236aa in start_thread (arg=0x7f814a589700) at pthread_create.c:333
#9  0x00007f816bb74eed in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7f816c083800 (LWP 3400)):
[KCrash Handler]
#6  0x00007f81559dddf4 in isEmpty (this=0x10) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qstring.h:791
#7  KScreen::ConfigOperation::hasError (this=this@entry=0x152a2f0) at ../../src/configoperation.cpp:76
#8  0x00007f81559de026 in KScreen::ConfigOperation::exec (this=0x152a2f0) at ../../src/configoperation.cpp:109
#9  0x00007f8155c1133c in KCMKScreen::save (this=0x152a2f0) at ../../../kcm/src/kcm_kscreen.cpp:144
#10 0x00007f816b84d077 in KCModuleProxy::save (this=this@entry=0x10fbb70) at ../../src/kcmoduleproxy.cpp:272
#11 0x00007f816b84a2f0 in KCMultiDialogPrivate::apply (this=<optimized out>) at ../../src/kcmultidialog.cpp:323
#12 0x00007f816b84a695 in KCMultiDialog::qt_static_metacall (_o=0x152a2f0, _c=QMetaObject::ReadProperty, _id=1, _a=0x0) at ./moc_kcmultidialog.cpp:112
#13 0x00007f8169e5b9c9 in QMetaObject::activate (sender=sender@entry=0x110bd10, signalOffset=<optimized out>, local_signal_index=local_signal_index@entry=2, argv=argv@entry=0x7ffcc66fd7d0) at kernel/qobject.cpp:3716
#14 0x00007f8169e5c057 in QMetaObject::activate (sender=sender@entry=0x110bd10, m=m@entry=0x7f816a721a60 <QAbstractButton::staticMetaObject>, local_signal_index=local_signal_index@entry=2, argv=argv@entry=0x7ffcc66fd7d0) at kernel/qobject.cpp:3582
#15 0x00007f816a596012 in QAbstractButton::clicked (this=this@entry=0x110bd10, _t1=false) at .moc/moc_qabstractbutton.cpp:298
#16 0x00007f816a2e3675 in QAbstractButtonPrivate::emitClicked (this=0x110b0e0) at widgets/qabstractbutton.cpp:534
#17 0x00007f816a2e4299 in QAbstractButtonPrivate::click (this=0x110b0e0) at widgets/qabstractbutton.cpp:527
#18 0x00007f816a2e4454 in QAbstractButton::mouseReleaseEvent (this=0x110bd10, e=0x7ffcc66fdc90) at widgets/qabstractbutton.cpp:1132
#19 0x00007f816a22b1e8 in QWidget::event (this=0x110bd10, event=0x7ffcc66fdc90) at kernel/qwidget.cpp:9022
#20 0x00007f816a1e7b2c in QApplicationPrivate::notify_helper (this=0x101ae70, receiver=0x110bd10, e=0x7ffcc66fdc90) at kernel/qapplication.cpp:3720
#21 0x00007f816a1ed8eb in QApplication::notify (this=0x7ffcc66fd9d0, receiver=0x7ffcc66fd9f0, e=0x7ffcc66fdc90) at kernel/qapplication.cpp:3280
#22 0x00007f8169e2ac2b in QCoreApplication::notifyInternal (this=0x7ffcc66fe5c0, receiver=receiver@entry=0x110bd10, event=event@entry=0x7ffcc66fdc90) at kernel/qcoreapplication.cpp:935
#23 0x00007f816a1ec3da in sendSpontaneousEvent (event=0x7ffcc66fdc90, receiver=0x110bd10) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#24 QApplicationPrivate::sendMouseEvent (receiver=0x110bd10, event=0x7ffcc66fdc90, alienWidget=0x110bd10, nativeWidget=0x10c3f90, buttonDown=<optimized out>, lastMouseReceiver=..., spontaneous=true) at kernel/qapplication.cpp:2751
#25 0x00007f816a243cc0 in QWidgetWindow::handleMouseEvent (this=0x11a0b20, event=0x7ffcc66fe0a0) at kernel/qwidgetwindow.cpp:543
#26 0x00007f816a245e33 in QWidgetWindow::event (this=0x11a0b20, event=0x7ffcc66fe0a0) at kernel/qwidgetwindow.cpp:210
#27 0x00007f816a1e7b2c in QApplicationPrivate::notify_helper (this=0x101ae70, receiver=0x11a0b20, e=0x7ffcc66fe0a0) at kernel/qapplication.cpp:3720
#28 0x00007f816a1ed000 in QApplication::notify (this=0x7ffcc66fe5c0, receiver=0x11a0b20, e=0x7ffcc66fe0a0) at kernel/qapplication.cpp:3503
#29 0x00007f8169e2ac2b in QCoreApplication::notifyInternal (this=0x7ffcc66fe5c0, receiver=0x11a0b20, event=0x7ffcc66fe0a0) at kernel/qcoreapplication.cpp:935
#30 0x00007f8167709f82 in sendSpontaneousEvent (event=<optimized out>, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#31 QGuiApplicationPrivate::processMouseEvent (e=0x155b880) at kernel/qguiapplication.cpp:1774
#32 0x00007f816770bb45 in QGuiApplicationPrivate::processWindowSystemEvent (e=e@entry=0x155b880) at kernel/qguiapplication.cpp:1576
#33 0x00007f81676f034f in QWindowSystemInterface::sendWindowSystemEvents (flags=...) at kernel/qwindowsysteminterface.cpp:572
#34 0x00007f81599ba590 in userEventSourceDispatch (source=<optimized out>) at eventdispatchers/qeventdispatcher_glib.cpp:70
#35 0x00007f8163b31c3d in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#36 0x00007f8163b31f20 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#37 0x00007f8163b31fcc in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#38 0x00007f8169e83c57 in QEventDispatcherGlib::processEvents (this=0x106a620, flags=...) at kernel/qeventdispatcher_glib.cpp:418
#39 0x00007f8169e283e2 in QEventLoop::exec (this=this@entry=0x7ffcc66fe450, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#40 0x00007f816a3e94b5 in QDialog::exec (this=0x10c3f90) at dialogs/qdialog.cpp:541
#41 0x00007f816be409cb in kdemain (_argc=<optimized out>, _argv=<optimized out>) at ../../kcmshell/main.cpp:307
#42 0x00007f816ba8ea40 in __libc_start_main (main=0x400730 <main(int, char**)>, argc=2, argv=0x7ffcc66fe708, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffcc66fe6f8) at libc-start.c:289
#43 0x0000000000400769 in _start ()

Reported using DrKonqi