Application: kwin_x11 (5.14.3)

Qt Version: 5.11.2
Frameworks Version: 5.51.0
Operating System: Linux 4.18.0-3-amd64 x86_64
Distribution: Debian GNU/Linux buster/sid

-- Information about the crash:
This issue happens to me on Debian sid packages (I do not use anything else), on x86-64 (ditto).

I was alt-tabbing right after triggering a mail send in claws-mail. When sending a mail, this gtk application pops a window showing mail sending progress. This window closes once mail is sent.
I was alt-tabbing to other applications (few opened: chomium, konsole) while this happened (likely after progress window creation, so the issue is likely during window destruction, but I was not paying special attention to this).

This issue happens from time to time (once a month ?) in this situation (because I often alt-tab away from claws once I am done composing an email), and since many kde versions (so this is not a recent regression).
Once kwin crashed, it respawns automatically and I can carry on (modulo reorganising windows between my physical screens).

Regards,
Vincent Pelletier

The crash can be reproduced sometimes.

-- Backtrace:
Application: KWin (kwin_x11), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f731de05940 (LWP 2179))]

Thread 5 (Thread 0x7f731755f700 (LWP 4579)):
#0  0x00007f7325ee9fec in __pthread_cond_wait_common (abstime=0x0, mutex=0x55902711ede8, cond=0x55902711ee10) at pthread_cond_wait.c:418
#1  0x00007f7325ee9fec in __pthread_cond_wait (cond=0x55902711ee10, mutex=0x55902711ede8) at pthread_cond_wait.c:655
#2  0x00007f73078e3bab in  () at /usr/lib/x86_64-linux-gnu/dri/i965_dri.so
#3  0x00007f73078e38d7 in  () at /usr/lib/x86_64-linux-gnu/dri/i965_dri.so
#4  0x00007f7316d5f000 in  ()
#5  0x0000000000000000 in  ()

Thread 4 (Thread 0x7f7316999700 (LWP 2349)):
#0  0x00007f73284d2cd6 in __GI_ppoll (fds=0x7f730c000d28, nfds=1, timeout=<optimized out>, sigmask=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1  0x00007f73270e5d11 in qt_safe_poll(pollfd*, unsigned long, timespec const*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#2  0x00007f73270e7189 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3  0x00007f7327096d0b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4  0x00007f7326ee60c6 in QThread::exec() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5  0x00007f7325711385 in  () at /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#6  0x00007f7326eefc97 in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#7  0x00007f7325ee3fa3 in start_thread (arg=<optimized out>) at pthread_create.c:486
#8  0x00007f73284dd88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 3 (Thread 0x7f7317fff700 (LWP 2206)):
#0  0x00007f73284d2cd6 in __GI_ppoll (fds=0x7f731000ecf8, nfds=1, timeout=<optimized out>, sigmask=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1  0x00007f73270e5d11 in qt_safe_poll(pollfd*, unsigned long, timespec const*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#2  0x00007f73270e7189 in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#3  0x00007f7327096d0b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#4  0x00007f7326ee60c6 in QThread::exec() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5  0x00007f73251ea545 in  () at /usr/lib/x86_64-linux-gnu/libQt5DBus.so.5
#6  0x00007f7326eefc97 in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#7  0x00007f7325ee3fa3 in start_thread (arg=<optimized out>) at pthread_create.c:486
#8  0x00007f73284dd88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 2 (Thread 0x7f731d4da700 (LWP 2191)):
#0  0x00007f73284d2bd9 in __GI___poll (fds=0x7f731d4d9b78, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
#1  0x00007f7326e0fcf7 in  () at /usr/lib/x86_64-linux-gnu/libxcb.so.1
#2  0x00007f7326e1191a in xcb_wait_for_event () at /usr/lib/x86_64-linux-gnu/libxcb.so.1
#3  0x00007f731d9b3519 in  () at /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#4  0x00007f7326eefc97 in  () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#5  0x00007f7325ee3fa3 in start_thread (arg=<optimized out>) at pthread_create.c:486
#6  0x00007f73284dd88f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 1 (Thread 0x7f731de05940 (LWP 2179)):
[KCrash Handler]
#6  0x00000000ffffffff in  ()
#7  0x00007f73281ec39d in KWin::Workspace::constrainedStackingOrder() () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#8  0x00007f73281ecbe8 in KWin::Workspace::updateStackingOrder(bool) () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#9  0x00007f73281ecfb0 in KWin::Workspace::blockStackingUpdates(bool) () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#10 0x00007f732819c6c8 in KWin::Client::destroyClient() () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#11 0x00007f73281f8171 in KWin::Client::unmapNotifyEvent(xcb_unmap_notify_event_t*) () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#12 0x00007f73281fb84b in KWin::Client::windowEvent(xcb_generic_event_t*) () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#13 0x00007f73281fc5fa in KWin::Workspace::workspaceEvent(xcb_generic_event_t*) () at /usr/lib/x86_64-linux-gnu/libkwin.so.5
#14 0x00007f7327095b8f in QAbstractEventDispatcher::filterNativeEvent(QByteArray const&, void*, long*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#15 0x00007f731d9b4cb0 in QXcbConnection::handleXcbEvent(xcb_generic_event_t*) () at /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#16 0x00007f731d9b5843 in QXcbConnection::processXcbEvents() () at /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#17 0x00007f73270c1b42 in QObject::event(QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#18 0x00007f7327a10491 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#19 0x00007f7327a17ad0 in QApplication::notify(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Widgets.so.5
#20 0x00007f7327098039 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#21 0x00007f732709b02b in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#22 0x00007f73270e6ffb in QEventDispatcherUNIX::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#23 0x00007f731da46aed in  () at /usr/lib/x86_64-linux-gnu/libQt5XcbQpa.so.5
#24 0x00007f7327096d0b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#25 0x00007f732709ee82 in QCoreApplication::exec() () at /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
#26 0x00007f73285af47b in kdemain () at /usr/lib/x86_64-linux-gnu/libkdeinit5_kwin_x11.so
#27 0x00007f732840809b in __libc_start_main (main=0x559026157050, argc=1, argv=0x7fff3e026768, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff3e026758) at ../csu/libc-start.c:308
#28 0x000055902615708a in _start ()
[Inferior 1 (process 2179) detached]

Reported using DrKonqi