Application: kwin (4.8.5 (4.8.5))
KDE Platform Version: 4.8.5 (4.8.5)
Qt Version: 4.8.1
Operating System: Linux 3.2.0-61-generic-pae i686
Distribution: Ubuntu 12.04.4 LTS

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

Switching the windows using Alt-Tab

- Unusual behavior I noticed:

At some point I noticed that the lower bar (this with usual task bar) has disappeared. The view with switching windows was then frozen for a few seconds, then I just saw that the window decorations disappeared and KWin was restarted. After KWin restarted, the lower bar was still missing. I haven't yet tried to restart KDE because I'm writing this report :)

-- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0xb1b0a740 (LWP 2305))]

Thread 2 (Thread 0xace06b40 (LWP 2399)):
#0  0xb77da1b2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1  0xb2aab96b in pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/i386/i686/../i486/pthread_cond_wait.S:169
#2  0xb75af4bc in __pthread_cond_wait (cond=0xb67bd890, mutex=0xb67bd878) at forward.c:139
#3  0xb66b9029 in ?? () from /usr/lib/i386-linux-gnu/libQtScript.so.4
#4  0xb66b906f in ?? () from /usr/lib/i386-linux-gnu/libQtScript.so.4
#5  0xb2aa7d4c in start_thread (arg=0xace06b40) at pthread_create.c:308
#6  0xb75a1bae in clone () at ../sysdeps/unix/sysv/linux/i386/clone.S:130

Thread 1 (Thread 0xb1b0a740 (LWP 2305)):
[KCrash Handler]
#7  0x00000000 in ?? ()
#8  0xaced4e10 in KWin::CoverSwitchEffect::postPaintScreen (this=0x880aeb0) at ../../../kwin/effects/coverswitch/coverswitch.cpp:411
#9  0xb77548ce in KWin::EffectsHandlerImpl::postPaintScreen (this=0x86c38f0) at ../../kwin/effects.cpp:228
#10 0xb772f49f in KWin::Scene::paintScreen (this=0x83ff740, mask=0xbf974a74, region=0xbf974b08) at ../../kwin/scene.cpp:159
#11 0xb7747b69 in KWin::SceneOpenGL::paint (this=0x83ff740, damage=..., toplevels=...) at ../../kwin/scene_opengl_glx.cpp:459
#12 0xb7728aa4 in KWin::Workspace::performCompositing (this=0x8578298) at ../../kwin/composite.cpp:417
#13 0xb5ff5ac4 in QObject::event (this=0x8578298, e=0xbf974fec) at kernel/qobject.cpp:1157
#14 0xb54c4ed4 in notify_helper (e=0xbf974fec, receiver=0x8578298, this=0x82c0c30) at kernel/qapplication.cpp:4559
#15 QApplicationPrivate::notify_helper (this=0x82c0c30, receiver=0x8578298, e=0xbf974fec) at kernel/qapplication.cpp:4531
#16 0xb54ca30d in QApplication::notify (this=0xbf974fec, receiver=0x8578298, e=0xbf974fec) at kernel/qapplication.cpp:4288
#17 0xb725ae01 in KApplication::notify (this=0xbf9752f8, receiver=0x8578298, event=0xbf974fec) at ../../kdeui/kernel/kapplication.cpp:311
#18 0xb76d17ff in notify (e=0xbf974fec, o=0x8578298, this=0xbf9752f8) at ../../kwin/main.cpp:368
#19 KWin::Application::notify (this=0xbf9752f8, o=0x8578298, e=0xbf974fec) at ../../kwin/main.cpp:364
#20 0xb5fda97e in QCoreApplication::notifyInternal (this=0xbf9752f8, receiver=0x8578298, event=0xbf974fec) at kernel/qcoreapplication.cpp:876
#21 0xb600f990 in sendEvent (event=0xbf974fec, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#22 QTimerInfoList::activateTimers (this=0x82c14d4) at kernel/qeventdispatcher_unix.cpp:611
#23 0xb6010207 in QEventDispatcherUNIX::processEvents (this=0x827fea0, flags=...) at kernel/qeventdispatcher_unix.cpp:930
#24 0xb557ebbe in QEventDispatcherX11::processEvents (this=0x827fea0, flags=...) at kernel/qeventdispatcher_x11.cpp:152
#25 0xb5fd950d in QEventLoop::processEvents (this=0xbf975234, flags=...) at kernel/qeventloop.cpp:149
#26 0xb5fd97a9 in QEventLoop::exec (this=0xbf975234, flags=...) at kernel/qeventloop.cpp:204
#27 0xb5fdeeba in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1148
#28 0xb54c2a74 in QApplication::exec () at kernel/qapplication.cpp:3820
#29 0xb76d47c5 in kdemain (argc=3, argv=0xbf9755a4) at ../../kwin/main.cpp:541
#30 0x0804850b in main (argc=3, argv=0xbf9755a4) at kwin_dummy.cpp:3

Possible duplicates by query: bug 300809.

Reported using DrKonqi