Application: kwin_x11 (5.10.90)
 (Compiled from sources)
Qt Version: 5.9.0
Frameworks Version: 5.35.0
Operating System: Linux 4.8.0-54-generic x86_64
Distribution: KDE neon Developer Edition

-- Information about the crash:
- What I was doing when the application crashed:
Pressed Alt+Shift+F12 twice (ie. turn off compositing and back on)
Then I noticed my panel started flickering which I tried to remedy by restarting kwin (I ran kwin_x11 --replace)
and then the already running instance crashed on teardown.

It does not happen if I just kwin_x11 --replace directly, turning compositing off and back on is important, just turning it off also doesn't suffice to make it crash.

Console output from the crashed KWin instance:

org.kde.kactivities.lib.core: Killing the consumer
kwin_core: Extensions: shape: 0x "11"  composite: 0x "4"  render: 0x "b"  fixes: 0x "50"  randr: 0x "14"  sync: 0x "31"  damage: 0x  "11"
QThread: Destroyed while thread is still running
Application::crashHandler() called with signal 6; recent crashes: 1
QCoreApplication::applicationFilePath: Please instantiate the QApplication object first
sh: 1: --crashes: not found
KCrash: crashing... crashRecursionCounter = 2

The crash can be reproduced every time.

-- Backtrace:
Application: KWin (kwin_x11), signal: Aborted
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7fd19bd4f940 (LWP 18975))]

Thread 5 (Thread 0x7fd19102f700 (LWP 18988)):
#0  0x00007fd1b2344c21 in __GI_ppoll (fds=0x7fd184000b08, nfds=1, timeout=<optimized out>, sigmask=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:50
#1  0x00007fd1affb9dc1 in qt_safe_poll(pollfd*, unsigned long, timespec const*) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#2  0x00007fd1affbb422 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3  0x00007fd1aff6830a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4  0x00007fd1afd97af4 in QThread::exec() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5  0x00007fd1afd9c509 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#6  0x00007fd1abca86ba in start_thread (arg=0x7fd19102f700) at pthread_create.c:333
#7  0x00007fd1b235082d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 4 (Thread 0x7fd17eb0d700 (LWP 18987)):
#0  pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1  0x00007fd1af09d784 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#2  0x00007fd1af09d7c9 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#3  0x00007fd1abca86ba in start_thread (arg=0x7fd17eb0d700) at pthread_create.c:333
#4  0x00007fd1b235082d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 3 (Thread 0x7fd198fd1700 (LWP 18977)):
#0  0x00007fd1b2344c21 in __GI_ppoll (fds=0x7fd18c00ebb8, nfds=1, timeout=<optimized out>, sigmask=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:50
#1  0x00007fd1affb9dc1 in qt_safe_poll(pollfd*, unsigned long, timespec const*) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#2  0x00007fd1affbb422 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3  0x00007fd1aff6830a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4  0x00007fd1afd97af4 in QThread::exec() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5  0x00007fd1b2967b75 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5DBus.so.5
#6  0x00007fd1afd9c509 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#7  0x00007fd1abca86ba in start_thread (arg=0x7fd198fd1700) at pthread_create.c:333
#8  0x00007fd1b235082d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 2 (Thread 0x7fd19ab4a700 (LWP 18976)):
#0  0x00007fd1b2344b5d in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007fd1b12c1c62 in poll (__timeout=-1, __nfds=1, __fds=0x7fd19ab49b80) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46
#2  _xcb_conn_wait (c=c@entry=0xcc80e0, cond=cond@entry=0xcc8120, vector=vector@entry=0x0, count=count@entry=0x0) at ../../src/xcb_conn.c:459
#3  0x00007fd1b12c38d7 in xcb_wait_for_event (c=0xcc80e0) at ../../src/xcb_in.c:693
#4  0x00007fd19b7f81f9 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#5  0x00007fd1afd9c509 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#6  0x00007fd1abca86ba in start_thread (arg=0x7fd19ab4a700) at pthread_create.c:333
#7  0x00007fd1b235082d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7fd19bd4f940 (LWP 18975)):
[KCrash Handler]
#6  0x00007fd1b227f428 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
#7  0x00007fd1b228102a in __GI_abort () at abort.c:89
#8  0x00007fd1afd855b1 in QMessageLogger::fatal(char const*, ...) const () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#9  0x00007fd1afd96f04 in QThread::~QThread() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#10 0x00007fd1afd97009 in QThread::~QThread() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#11 0x00007fd1aff93bb3 in QObjectPrivate::deleteChildren() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#12 0x00007fd1aff9dad4 in QObject::~QObject() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#13 0x00007fd1b1e85ef8 in KWin::Platform::~Platform() () from /usr/lib/x86_64-linux-gnu/libkwin.so.5
#14 0x00007fd19857261a in KWin::X11StandalonePlatform::~X11StandalonePlatform() () from /usr/lib/x86_64-linux-gnu/qt5/plugins/org.kde.kwin.platforms/KWinX11Platform.so
#15 0x00007fd19857264a in KWin::X11StandalonePlatform::~X11StandalonePlatform() () from /usr/lib/x86_64-linux-gnu/qt5/plugins/org.kde.kwin.platforms/KWinX11Platform.so
#16 0x00007fd1aff93bb3 in QObjectPrivate::deleteChildren() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#17 0x00007fd1aff9dad4 in QObject::~QObject() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#18 0x00007fd1aff6beb2 in QCoreApplication::~QCoreApplication() () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#19 0x00007fd1b08d6be4 in QApplication::~QApplication() () from /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#20 0x00007fd1b1d47eb8 in KWin::Application::~Application() () from /usr/lib/x86_64-linux-gnu/libkwin.so.5
#21 0x00007fd1b261a71d in KWin::ApplicationX11::~ApplicationX11() () from /usr/lib/x86_64-linux-gnu/libkdeinit5_kwin_x11.so
#22 0x00007fd1b261c0bd in kdemain () from /usr/lib/x86_64-linux-gnu/libkdeinit5_kwin_x11.so
#23 0x0000000000400848 in main ()

Possible duplicates by query: bug 379070, bug 378738, bug 378240, bug 377996, bug 377986.

Reported using DrKonqi