Application: kwin (4.11.16)
KDE Platform Version: 4.14.6
Qt Version: 4.8.6
Operating System: Linux 3.19.2-201.fc21.x86_64 x86_64
Distribution: "Fedora release 21 (Twenty One)"

-- Information about the crash:
Watching a video.
Multiple Chrome and Firefox open.
Also Libre office Calc.

-- Backtrace:
Application: KWin (kwin), signal: Segmentation fault
Using host libthread_db library "/lib64/libthread_db.so.1".
81	T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)
[Current thread is 1 (Thread 0x7f5cedb65900 (LWP 3124))]

Thread 2 (Thread 0x7f5cdb584700 (LWP 3127)):
#0  0x0000003c8080c590 in pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x0000003c9f59a49a in QTWTF::TCMalloc_PageHeap::scavengerThread() (this=0x3c9f89ff80) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:2359
#2  0x0000003c9f59a4c9 in QTWTF::TCMalloc_PageHeap::runScavengerThread(void*) (context=<optimized out>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:1464
#3  0x0000003c8080752a in start_thread (arg=0x7f5cdb584700) at pthread_create.c:310
#4  0x0000003c7fd0022d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7f5cedb65900 (LWP 3124)):
[KCrash Handler]
#6  0x00007f5cedb65868 in  ()
#7  0x0000000001e8f9c0 in  ()
#8  0x000000000000000b in  ()
#9  0x0000000001e8f9c0 in  ()
#10 0x00007ffdf5e569b0 in  ()
#11 0x00007f5cf37ea649 in  () at /usr/lib64/nvidia/libGL.so.1
#12 0x00007f5cf08660a9 in  () at /usr/lib64/nvidia/tls/libnvidia-tls.so.346.47
#13 0x0000003c81c0b22b in poll_for_reply () at /lib64/libxcb.so.1
#14 0x0000003c81c0baa4 in wait_for_reply () at /lib64/libxcb.so.1
#15 0x0000003c81c0bba1 in xcb_wait_for_reply () at /lib64/libxcb.so.1
#16 0x00007f5cf45de2b7 in KWin::Toplevel::getDamageRegionReply() () at /lib64/libkdeinit4_kwin.so
#17 0x00007f5cf45de7f5 in KWin::Compositor::performCompositing() () at /lib64/libkdeinit4_kwin.so
#18 0x0000003c8d39f2a3 in QObject::event(QEvent*) (this=0x1771200, e=<optimized out>) at kernel/qobject.cpp:1253
#19 0x0000003c8f7c7efc in QApplicationPrivate::notify_helper(QObject*, QEvent*) (this=this@entry=0x15da9a0, receiver=receiver@entry=0x1771200, e=e@entry=0x7ffdf5e56f10) at kernel/qapplication.cpp:4565
#20 0x0000003c8f7ce958 in QApplication::notify(QObject*, QEvent*) (this=this@entry=0x7ffdf5e573f0, receiver=receiver@entry=0x1771200, e=e@entry=0x7ffdf5e56f10) at kernel/qapplication.cpp:4351
#21 0x0000003d0e64ec6a in KApplication::notify(QObject*, QEvent*) (this=0x7ffdf5e573f0, receiver=0x1771200, event=0x7ffdf5e56f10) at /usr/src/debug/kdelibs-4.14.6/kdeui/kernel/kapplication.cpp:311
#22 0x0000003c8d38616d in QCoreApplication::notifyInternal(QObject*, QEvent*) (this=0x7ffdf5e573f0, receiver=0x1771200, event=event@entry=0x7ffdf5e56f10) at kernel/qcoreapplication.cpp:953
#23 0x0000003c8d3b7aeb in QTimerInfoList::activateTimers() (event=0x7ffdf5e56f10, receiver=<optimized out>) at kernel/qcoreapplication.h:231
#24 0x0000003c8d3b7aeb in QTimerInfoList::activateTimers() (this=0x15db468) at kernel/qeventdispatcher_unix.cpp:621
#25 0x0000003c8d3b7bc0 in QEventDispatcherUNIX::activateTimers() (this=this@entry=0x1523b00) at kernel/qeventdispatcher_unix.cpp:878
#26 0x0000003c8d3b8618 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x1523b00, flags=...) at kernel/qeventdispatcher_unix.cpp:948
#27 0x0000003c8f86ba9b in QEventDispatcherX11::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=0x1523b00, flags=...) at kernel/qeventdispatcher_x11.cpp:152
#28 0x0000003c8d384cc1 in QEventLoop::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7ffdf5e57260, flags=...) at kernel/qeventloop.cpp:149
#29 0x0000003c8d385025 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) (this=this@entry=0x7ffdf5e57260, flags=...) at kernel/qeventloop.cpp:204
#30 0x0000003c8d38a709 in QCoreApplication::exec() () at kernel/qcoreapplication.cpp:1225
#31 0x00007f5cf4593048 in kdemain () at /lib64/libkdeinit4_kwin.so
#32 0x0000003c7fc1ffe0 in __libc_start_main (main=0x4009d0 <main>, argc=3, argv=0x7ffdf5e57548, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffdf5e57538) at libc-start.c:289
#33 0x00000000004009fe in _start ()

Reported using DrKonqi