Application: kwin_x11 (5.14.5)

Qt Version: 5.11.3
Frameworks Version: 5.54.0
Operating System: Linux 5.2.0-2-amd64 x86_64
Distribution: Debian GNU/Linux bullseye/sid

-- Information about the crash:
I work with a laptop's internal display and an external 4k monitor connected via DisplayPort on a docking station. KDE is configured to switch off the displays after some idle time. When I wake the monitor 
sometimes (rough guess: 5% of the time) kwin crashed.

Maybe related: More often (about 30% of the time) the 4k monitor will succesively "loose" some of its higher resolutions. 2160p and 1440p on the first sleep, going to 1080i [sic] on the next one. I haven't seen further degredation though.

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 0x7f689ae7be00 (LWP 8933))]

Thread 6 (Thread 0x7f685c4e3700 (LWP 8941)):
#0  futex_wait_cancelable (private=0, expected=0, futex_word=0x7f68a1664fb8 <QTWTF::pageheap_memory+57592>) at ../sysdeps/unix/sysv/linux/futex-internal.h:88
#1  __pthread_cond_wait_common (abstime=0x0, mutex=0x7f68a1664f68 <QTWTF::pageheap_memory+57512>, cond=0x7f68a1664f90 <QTWTF::pageheap_memory+57552>) at pthread_cond_wait.c:502
#2  __pthread_cond_wait (cond=0x7f68a1664f90 <QTWTF::pageheap_memory+57552>, mutex=0x7f68a1664f68 <QTWTF::pageheap_memory+57512>) at pthread_cond_wait.c:655
#3  0x00007f68a156ee6a in QTWTF::TCMalloc_PageHeap::scavengerThread (this=0x7f68a1656ec0 <QTWTF::pageheap_memory>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:2359
#4  0x00007f68a156ee89 in QTWTF::TCMalloc_PageHeap::runScavengerThread (context=<optimized out>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:1464
#5  0x00007f68a0c63fa3 in start_thread (arg=<optimized out>) at pthread_create.c:486
#6  0x00007f68a30c64cf in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 5 (Thread 0x7f6872b9c700 (LWP 8940)):
#0  0x00007f68a30bb916 in __GI_ppoll (fds=fds@entry=0x7f686c000d28, nfds=nfds@entry=1, timeout=<optimized out>, timeout@entry=0x0, sigmask=sigmask@entry=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1  0x00007f68a1cc23c1 in ppoll (__ss=<optimized out>, __timeout=<optimized out>, __nfds=<optimized out>, __fds=<optimized out>) at /usr/include/x86_64-linux-gnu/bits/poll2.h:77
#2  qt_ppoll (timeout_ts=0x0, nfds=1, fds=0x7f686c000d28) at kernel/qcore_unix.cpp:132
#3  qt_ppoll (timeout_ts=0x0, nfds=1, fds=0x7f686c000d28) at kernel/qcore_unix.cpp:129
#4  qt_safe_poll (fds=0x7f686c000d28, nfds=nfds@entry=1, timeout_ts=timeout_ts@entry=0x0) at kernel/qcore_unix.cpp:153
#5  0x00007f68a1cc3839 in QEventDispatcherUNIX::processEvents (this=<optimized out>, flags=...) at ../../include/QtCore/../../src/corelib/tools/qarraydata.h:209
#6  0x00007f68a1c73cfb in QEventLoop::exec (this=this@entry=0x7f6872b9bc40, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:140
#7  0x00007f68a1ac3d8e in QThread::exec (this=this@entry=0x5620c3bfc690) at ../../include/QtCore/../../src/corelib/global/qflags.h:120
#8  0x00007f68a0484c65 in QQmlThreadPrivate::run (this=0x5620c3bfc690) at qml/ftw/qqmlthread.cpp:148
#9  0x00007f68a1acda07 in QThreadPrivate::start (arg=0x5620c3bfc690) at thread/qthread_unix.cpp:367
#10 0x00007f68a0c63fa3 in start_thread (arg=<optimized out>) at pthread_create.c:486
#11 0x00007f68a30c64cf in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 4 (Thread 0x7f6890f50700 (LWP 8938)):
#0  futex_wait_cancelable (private=0, expected=0, futex_word=0x5620c261fa38) at ../sysdeps/unix/sysv/linux/futex-internal.h:88
#1  __pthread_cond_wait_common (abstime=0x0, mutex=0x5620c261f9e8, cond=0x5620c261fa10) at pthread_cond_wait.c:502
#2  __pthread_cond_wait (cond=0x5620c261fa10, mutex=0x5620c261f9e8) at pthread_cond_wait.c:655
#3  0x00007f689144498b in cnd_wait (mtx=0x5620c261f9e8, cond=0x5620c261fa10) at ../include/c11/threads_posix.h:155
#4  util_queue_thread_func (input=input@entry=0x5620c24b47b0) at ../src/util/u_queue.c:272
#5  0x00007f68914445b7 in impl_thrd_routine (p=<optimized out>) at ../include/c11/threads_posix.h:87
#6  0x00007f68a0c63fa3 in start_thread (arg=<optimized out>) at pthread_create.c:486
#7  0x00007f68a30c64cf in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 3 (Thread 0x7f68935d1700 (LWP 8937)):
#0  0x00007f68a30bb916 in __GI_ppoll (fds=fds@entry=0x7f6880000d28, nfds=nfds@entry=1, timeout=<optimized out>, timeout@entry=0x0, sigmask=sigmask@entry=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1  0x00007f68a1cc23c1 in ppoll (__ss=<optimized out>, __timeout=<optimized out>, __nfds=<optimized out>, __fds=<optimized out>) at /usr/include/x86_64-linux-gnu/bits/poll2.h:77
#2  qt_ppoll (timeout_ts=0x0, nfds=1, fds=0x7f6880000d28) at kernel/qcore_unix.cpp:132
#3  qt_ppoll (timeout_ts=0x0, nfds=1, fds=0x7f6880000d28) at kernel/qcore_unix.cpp:129
#4  qt_safe_poll (fds=0x7f6880000d28, nfds=nfds@entry=1, timeout_ts=timeout_ts@entry=0x0) at kernel/qcore_unix.cpp:153
#5  0x00007f68a1cc3839 in QEventDispatcherUNIX::processEvents (this=<optimized out>, flags=...) at ../../include/QtCore/../../src/corelib/tools/qarraydata.h:209
#6  0x00007f68a1c73cfb in QEventLoop::exec (this=this@entry=0x7f68935d0c40, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:140
#7  0x00007f68a1ac3d8e in QThread::exec (this=this@entry=0x5620c235a720) at ../../include/QtCore/../../src/corelib/global/qflags.h:120
#8  0x00007f68a0484c65 in QQmlThreadPrivate::run (this=0x5620c235a720) at qml/ftw/qqmlthread.cpp:148
#9  0x00007f68a1acda07 in QThreadPrivate::start (arg=0x5620c235a720) at thread/qthread_unix.cpp:367
#10 0x00007f68a0c63fa3 in start_thread (arg=<optimized out>) at pthread_create.c:486
#11 0x00007f68a30c64cf in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 2 (Thread 0x7f68995ae700 (LWP 8935)):
#0  0x00007f68a30bb916 in __GI_ppoll (fds=fds@entry=0x7f688c00e6b8, nfds=nfds@entry=1, timeout=<optimized out>, timeout@entry=0x0, sigmask=sigmask@entry=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
#1  0x00007f68a1cc23c1 in ppoll (__ss=<optimized out>, __timeout=<optimized out>, __nfds=<optimized out>, __fds=<optimized out>) at /usr/include/x86_64-linux-gnu/bits/poll2.h:77
#2  qt_ppoll (timeout_ts=0x0, nfds=1, fds=0x7f688c00e6b8) at kernel/qcore_unix.cpp:132
#3  qt_ppoll (timeout_ts=0x0, nfds=1, fds=0x7f688c00e6b8) at kernel/qcore_unix.cpp:129
#4  qt_safe_poll (fds=0x7f688c00e6b8, nfds=nfds@entry=1, timeout_ts=timeout_ts@entry=0x0) at kernel/qcore_unix.cpp:153
#5  0x00007f68a1cc3839 in QEventDispatcherUNIX::processEvents (this=<optimized out>, flags=...) at ../../include/QtCore/../../src/corelib/tools/qarraydata.h:209
#6  0x00007f68a1c73cfb in QEventLoop::exec (this=this@entry=0x7f68995adc30, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:140
#7  0x00007f68a1ac3d8e in QThread::exec (this=this@entry=0x7f689ffcbd60 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at ../../include/QtCore/../../src/corelib/global/qflags.h:120
#8  0x00007f689ff4c545 in QDBusConnectionManager::run (this=0x7f689ffcbd60 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at qdbusconnection.cpp:178
#9  0x00007f68a1acda07 in QThreadPrivate::start (arg=0x7f689ffcbd60 <(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at thread/qthread_unix.cpp:367
#10 0x00007f68a0c63fa3 in start_thread (arg=<optimized out>) at pthread_create.c:486
#11 0x00007f68a30c64cf in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 1 (Thread 0x7f689ae7be00 (LWP 8933)):
[KCrash Handler]
#6  QXcbConnection::updateScreens (this=this@entry=0x5620c2170b50, event=event@entry=0x7f689402cb90) at qxcbconnection.cpp:295
#7  0x00007f689a9dde8b in QXcbConnection::handleXcbEvent (this=this@entry=0x5620c2170b50, event=event@entry=0x7f689402cb90) at qxcbconnection.cpp:1210
#8  0x00007f689a9de843 in QXcbConnection::processXcbEvents (this=0x5620c2170b50) at qxcbconnection.cpp:1790
#9  0x00007f68a1c9ed62 in QObject::event (this=0x5620c2170b50, e=<optimized out>) at kernel/qobject.cpp:1251
#10 0x00007f68a25f1501 in QApplicationPrivate::notify_helper (this=this@entry=0x5620c2137680, receiver=receiver@entry=0x5620c2170b50, e=e@entry=0x7f6894035380) at kernel/qapplication.cpp:3726
#11 0x00007f68a25f89b0 in QApplication::notify (this=0x7ffe3477c9e0, receiver=0x5620c2170b50, e=0x7f6894035380) at kernel/qapplication.cpp:3485
#12 0x00007f68a1c75029 in QCoreApplication::notifyInternal2 (receiver=0x5620c2170b50, event=0x7f6894035380) at ../../include/QtCore/5.11.3/QtCore/private/../../../../../src/corelib/thread/qthread_p.h:307
#13 0x00007f68a1c7800b in QCoreApplication::sendEvent (event=0x7f6894035380, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:234
#14 QCoreApplicationPrivate::sendPostedEvents (receiver=0x0, event_type=0, data=0x5620c2140d00) at kernel/qcoreapplication.cpp:1744
#15 0x00007f68a1cc36ab in QEventDispatcherUNIX::processEvents (this=0x5620c21b9140, flags=...) at kernel/qeventdispatcher_unix.cpp:466
#16 0x00007f689aa7262d in QUnixEventDispatcherQPA::processEvents (this=<optimized out>, flags=...) at qunixeventdispatcher.cpp:68
#17 0x00007f68a1c73cfb in QEventLoop::exec (this=this@entry=0x7ffe3477c8f0, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:140
#18 0x00007f68a1c7bcd2 in QCoreApplication::exec () at ../../include/QtCore/../../src/corelib/global/qflags.h:120
#19 0x00007f68a319847b in kdemain (argc=<optimized out>, argv=0x7ffe3477cb78) at ./main_x11.cpp:468
#20 0x00007f68a2ff109b in __libc_start_main (main=0x5620c1940050 <main>, argc=2, argv=0x7ffe3477cb78, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffe3477cb68) at ../csu/libc-start.c:308
#21 0x00005620c194008a in _start ()
[Inferior 1 (process 8933) detached]

Possible duplicates by query: bug 400009.

Reported using DrKonqi