Could you install debug symbols for plasma-desktop and Qt and reopen this with an additional backtrace when it crashes again? This looks interesting but the backtrace lacks too many symbols to make sense of what's going on so far.

OK, I'll do that.

Here's another backtrace, this time with more symbols.

Application: Plasma (plasmashell), signal: Segmentation fault
Using host libthread_db library "/lib64/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f9fc8f49f40 (LWP 1537))]

Thread 8 (Thread 0x7f9ef9925700 (LWP 3476)):
#0  0x00007f9fc2511f2b in __GI___poll (fds=0x7f9ef40029e0, nfds=1, timeout=2549283) at ../sysdeps/unix/sysv/linux/poll.c:29
#1  0x00007f9fbd288149 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0x7f9ef40029e0, timeout=<optimized out>, context=0x7f9ef4000be0) at gmain.c:4187
#2  0x00007f9fbd288149 in g_main_context_iterate (context=context@entry=0x7f9ef4000be0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3881
#3  0x00007f9fbd28825c in g_main_context_iteration (context=0x7f9ef4000be0, may_block=1) at gmain.c:3947
#4  0x00007f9fc2e4857b in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#5  0x00007f9fc2def4aa in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#6  0x00007f9fc2c168da in QThread::exec() () at /usr/lib64/libQt5Core.so.5
#7  0x00007f9efc1eff67 in KCupsConnection::run() () at /usr/lib64/libkcupslib.so
#8  0x00007f9fc2c1b8d0 in QThreadPrivate::start(void*) () at /usr/lib64/libQt5Core.so.5
#9  0x00007f9fc1dcb558 in start_thread (arg=0x7f9ef9925700) at pthread_create.c:465
#10 0x00007f9fc251c6df in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 7 (Thread 0x7f9f0f320700 (LWP 2270)):
#0  0x00007f9fc2511f2b in __GI___poll (fds=0x7f9f08005380, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
#1  0x00007f9fbd288149 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0x7f9f08005380, timeout=<optimized out>, context=0x7f9f08000be0) at gmain.c:4187
#2  0x00007f9fbd288149 in g_main_context_iterate (context=context@entry=0x7f9f08000be0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3881
#3  0x00007f9fbd28825c in g_main_context_iteration (context=0x7f9f08000be0, may_block=1) at gmain.c:3947
#4  0x00007f9fc2e4857b in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#5  0x00007f9fc2def4aa in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#6  0x00007f9fc2c168da in QThread::exec() () at /usr/lib64/libQt5Core.so.5
#7  0x00007f9fc6931b22 in QQuickPixmapReader::run() () at /usr/lib64/libQt5Quick.so.5
#8  0x00007f9fc2c1b8d0 in QThreadPrivate::start(void*) () at /usr/lib64/libQt5Core.so.5
#9  0x00007f9fc1dcb558 in start_thread (arg=0x7f9f0f320700) at pthread_create.c:465
#10 0x00007f9fc251c6df in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 6 (Thread 0x7f9f9ab94700 (LWP 2146)):
#0  0x00007f9fc1dd182d in futex_wait_cancelable (private=<optimized out>, expected=0, futex_word=0x7f9fc891ffb8 <QTWTF::pageheap_memory+57592>) at ../sysdeps/unix/sysv/linux/futex-internal.h:88
#1  0x00007f9fc1dd182d in __pthread_cond_wait_common (abstime=0x0, mutex=0x7f9fc891ff68 <QTWTF::pageheap_memory+57512>, cond=0x7f9fc891ff90 <QTWTF::pageheap_memory+57552>) at pthread_cond_wait.c:502
#2  0x00007f9fc1dd182d in __pthread_cond_wait (cond=0x7f9fc891ff90 <QTWTF::pageheap_memory+57552>, mutex=0x7f9fc891ff68 <QTWTF::pageheap_memory+57512>) at pthread_cond_wait.c:655
#3  0x00007f9fc862b614 in QTWTF::TCMalloc_PageHeap::scavengerThread() (this=0x7f9fc8911ec0 <QTWTF::pageheap_memory>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:2359
#4  0x00007f9fc862b659 in QTWTF::TCMalloc_PageHeap::runScavengerThread(void*) (context=<optimized out>) at ../3rdparty/javascriptcore/JavaScriptCore/wtf/FastMalloc.cpp:1464
#5  0x00007f9fc1dcb558 in start_thread (arg=0x7f9f9ab94700) at pthread_create.c:465
#6  0x00007f9fc251c6df in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 5 (Thread 0x7f9fa8d34700 (LWP 2122)):
#0  0x00007f9fc250da88 in __GI___libc_read (fd=11, buf=buf@entry=0x7f9fa8d33aa0, nbytes=nbytes@entry=16) at ../sysdeps/unix/sysv/linux/read.c:26
#1  0x00007f9fbd2cc3c0 in read (__nbytes=16, __buf=0x7f9fa8d33aa0, __fd=<optimized out>) at /usr/include/bits/unistd.h:44
#2  0x00007f9fbd2cc3c0 in g_wakeup_acknowledge (wakeup=0x7f9f9c003590) at gwakeup.c:210
#3  0x00007f9fbd287c2b in g_main_context_check (context=context@entry=0x7f9fa0000be0, max_priority=2147483647, fds=fds@entry=0x7f9fa0002de0, n_fds=n_fds@entry=1) at gmain.c:3664
#4  0x00007f9fbd2880f0 in g_main_context_iterate (context=context@entry=0x7f9fa0000be0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3883
#5  0x00007f9fbd28825c in g_main_context_iteration (context=0x7f9fa0000be0, may_block=1) at gmain.c:3947
#6  0x00007f9fc2e4857b in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#7  0x00007f9fc2def4aa in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#8  0x00007f9fc2c168da in QThread::exec() () at /usr/lib64/libQt5Core.so.5
#9  0x00007f9fc5d7fbd5 in QQmlThreadPrivate::run() () at /usr/lib64/libQt5Qml.so.5
#10 0x00007f9fc2c1b8d0 in QThreadPrivate::start(void*) () at /usr/lib64/libQt5Core.so.5
#11 0x00007f9fc1dcb558 in start_thread (arg=0x7f9fa8d34700) at pthread_create.c:465
#12 0x00007f9fc251c6df in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 4 (Thread 0x7f9faa7c2700 (LWP 1661)):
#0  0x00007f9fc250da88 in __GI___libc_read (fd=10, buf=buf@entry=0x7f9faa7c1aa0, nbytes=nbytes@entry=16) at ../sysdeps/unix/sysv/linux/read.c:26
#1  0x00007f9fbd2cc3c0 in read (__nbytes=16, __buf=0x7f9faa7c1aa0, __fd=<optimized out>) at /usr/include/bits/unistd.h:44
#2  0x00007f9fbd2cc3c0 in g_wakeup_acknowledge (wakeup=0x7f9fa40039a0) at gwakeup.c:210
#3  0x00007f9fbd287c2b in g_main_context_check (context=context@entry=0x7f9f9c000be0, max_priority=2147483647, fds=fds@entry=0x7f9f9c0029e0, n_fds=n_fds@entry=1) at gmain.c:3664
#4  0x00007f9fbd2880f0 in g_main_context_iterate (context=context@entry=0x7f9f9c000be0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3883
#5  0x00007f9fbd28825c in g_main_context_iteration (context=0x7f9f9c000be0, may_block=1) at gmain.c:3947
#6  0x00007f9fc2e4857b in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#7  0x00007f9fc2def4aa in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#8  0x00007f9fc2c168da in QThread::exec() () at /usr/lib64/libQt5Core.so.5
#9  0x00007f9fc5d7fbd5 in QQmlThreadPrivate::run() () at /usr/lib64/libQt5Qml.so.5
#10 0x00007f9fc2c1b8d0 in QThreadPrivate::start(void*) () at /usr/lib64/libQt5Core.so.5
#11 0x00007f9fc1dcb558 in start_thread (arg=0x7f9faa7c2700) at pthread_create.c:465
#12 0x00007f9fc251c6df in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 3 (Thread 0x7f9fabfff700 (LWP 1596)):
#0  0x00007f9fc2511f2b in __GI___poll (fds=0x7f9fa4002de0, nfds=1, timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
#1  0x00007f9fbd288149 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0x7f9fa4002de0, timeout=<optimized out>, context=0x7f9fa4000be0) at gmain.c:4187
#2  0x00007f9fbd288149 in g_main_context_iterate (context=context@entry=0x7f9fa4000be0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3881
#3  0x00007f9fbd28825c in g_main_context_iteration (context=0x7f9fa4000be0, may_block=1) at gmain.c:3947
#4  0x00007f9fc2e4857b in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#5  0x00007f9fc2def4aa in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /usr/lib64/libQt5Core.so.5
#6  0x00007f9fc2c168da in QThread::exec() () at /usr/lib64/libQt5Core.so.5
#7  0x00007f9fc326dbd5 in QDBusConnectionManager::run() () at /usr/lib64/libQt5DBus.so.5
#8  0x00007f9fc2c1b8d0 in QThreadPrivate::start(void*) () at /usr/lib64/libQt5Core.so.5
#9  0x00007f9fc1dcb558 in start_thread (arg=0x7f9fabfff700) at pthread_create.c:465
#10 0x00007f9fc251c6df in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 2 (Thread 0x7f9fb2855700 (LWP 1549)):
#0  0x00007f9fc2511f2b in __GI___poll (fds=fds@entry=0x7f9fb2854bc8, nfds=nfds@entry=1, timeout=timeout@entry=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
#1  0x00007f9fc754b387 in poll (__timeout=-1, __nfds=1, __fds=0x7f9fb2854bc8) at /usr/include/bits/poll2.h:46
#2  0x00007f9fc754b387 in _xcb_conn_wait (c=c@entry=0x5588786ca0a0, cond=cond@entry=0x5588786ca0e0, vector=vector@entry=0x0, count=count@entry=0x0) at xcb_conn.c:479
#3  0x00007f9fc754d17a in xcb_wait_for_event (c=0x5588786ca0a0) at xcb_in.c:693
#4  0x00007f9fb540c8d9 in QXcbEventReader::run() () at /usr/lib64/libQt5XcbQpa.so.5
#5  0x00007f9fc2c1b8d0 in QThreadPrivate::start(void*) () at /usr/lib64/libQt5Core.so.5
#6  0x00007f9fc1dcb558 in start_thread (arg=0x7f9fb2855700) at pthread_create.c:465
#7  0x00007f9fc251c6df in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 1 (Thread 0x7f9fc8f49f40 (LWP 1537)):
[KCrash Handler]
#6  0x00007f9f0ced5633 in QHash<QString, AbstractEntry*>::findNode(QString const&, unsigned int) const (this=this@entry=0x7f9fac00c0a0, akey=..., h=2470466443) at /usr/include/qt5/QtCore/qhash.h:917
#7  0x00007f9f0ced56be in QHash<QString, AbstractEntry*>::findNode(QString const&, unsigned int*) const (this=this@entry=0x7f9fac00c0a0, akey=..., ahp=ahp@entry=0x0) at /usr/include/qt5/QtCore/qhash.h:936
#8  0x00007f9f0ced0b67 in QHash<QString, AbstractEntry*>::contains(QString const&) const (akey=..., this=0x7f9fac00c0a0) at /usr/include/qt5/QtCore/qhash.h:906
#9  0x00007f9f0ced0b67 in KAStatsFavoritesModel::isFavorite(QString const&) const (this=this@entry=0x55887b78f710, id=...) at /usr/src/debug/plasma-desktop-5.11.5/applets/kicker/plugin/kastatsfavoritesmodel.cpp:547
#10 0x00007f9f0cef4721 in InvalidAppsFilterProxy::filterAcceptsRow(int, QModelIndex const&) const (this=0x55887c4ed820, source_row=<optimized out>, source_parent=...) at /usr/src/debug/plasma-desktop-5.11.5/applets/kicker/plugin/recentusagemodel.cpp:94
#11 0x00007f9fc2db61fb in QSortFilterProxyModelPrivate::create_mapping(QModelIndex const&) const () at /usr/lib64/libQt5Core.so.5
#12 0x00007f9fc2db8233 in QSortFilterProxyModel::rowCount(QModelIndex const&) const () at /usr/lib64/libQt5Core.so.5
#13 0x00007f9fc2db61c8 in QSortFilterProxyModelPrivate::create_mapping(QModelIndex const&) const () at /usr/lib64/libQt5Core.so.5
#14 0x00007f9fc2db754a in QSortFilterProxyModelPrivate::update_source_sort_column() () at /usr/lib64/libQt5Core.so.5
#15 0x00007f9fc2db7c38 in QSortFilterProxyModelPrivate::_q_sourceLayoutChanged(QList<QPersistentModelIndex> const&, QAbstractItemModel::LayoutChangeHint) () at /usr/lib64/libQt5Core.so.5
#16 0x00007f9fc2dbc573 in QSortFilterProxyModel::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) () at /usr/lib64/libQt5Core.so.5
#17 0x00007f9fc2e1edba in QMetaObject::activate(QObject*, int, int, void**) () at /usr/lib64/libQt5Core.so.5
#18 0x00007f9fc2d8f736 in QAbstractItemModel::layoutChanged(QList<QPersistentModelIndex> const&, QAbstractItemModel::LayoutChangeHint) () at /usr/lib64/libQt5Core.so.5
#19 0x00007f9fc2db7abe in QSortFilterProxyModel::invalidate() () at /usr/lib64/libQt5Core.so.5
#20 0x00007f9f0cef35ec in InvalidAppsFilterProxy::connectNewFavoritesModel() (this=0x55887c4ed820) at /usr/src/debug/plasma-desktop-5.11.5/applets/kicker/plugin/recentusagemodel.cpp:80
#21 0x00007f9fc2e1eebc in QMetaObject::activate(QObject*, int, int, void**) () at /usr/lib64/libQt5Core.so.5
#22 0x00007f9f0ceff2fa in AbstractModel::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) (_o=<optimized out>, _c=<optimized out>, _id=<optimized out>, _a=0x7fffc35d7ec0) at /usr/src/debug/plasma-desktop-5.11.5/build/applets/kicker/kickerplugin_autogen/7RBZBFH7CH/moc_abstractmodel.cpp:223
#23 0x00007f9fc5d6942d in QObjectPointerBinding::write(QV4::Value const&, bool, QFlags<QQmlPropertyData::WriteFlag>) () at /usr/lib64/libQt5Qml.so.5
#24 0x00007f9fc5d6a526 in QQmlNonbindingBinding::doUpdate(QQmlJavaScriptExpression::DeleteWatcher const&, QFlags<QQmlPropertyData::WriteFlag>, QV4::Scope&) () at /usr/lib64/libQt5Qml.so.5
#25 0x00007f9fc5d671c3 in QQmlBinding::update(QFlags<QQmlPropertyData::WriteFlag>) () at /usr/lib64/libQt5Qml.so.5
#26 0x00007f9fc5d7381b in QQmlObjectCreator::finalize(QQmlInstantiationInterrupt&) () at /usr/lib64/libQt5Qml.so.5
#27 0x00007f9fc5cf4df2 in QQmlIncubatorPrivate::incubate(QQmlInstantiationInterrupt&) () at /usr/lib64/libQt5Qml.so.5
#28 0x00007f9fc5cf539c in QQmlEnginePrivate::incubate(QQmlIncubator&, QQmlContextData*) () at /usr/lib64/libQt5Qml.so.5
#29 0x00007f9fc5cf2554 in QQmlComponent::create(QQmlIncubator&, QQmlContext*, QQmlContext*) () at /usr/lib64/libQt5Qml.so.5
#30 0x00007f9fc6a87874 in QQuickLoaderPrivate::_q_sourceLoaded() () at /usr/lib64/libQt5Quick.so.5
#31 0x00007f9fc6a879c8 in QQuickLoaderPrivate::load() () at /usr/lib64/libQt5Quick.so.5
#32 0x00007f9fc6a8850f in QQuickLoader::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) () at /usr/lib64/libQt5Quick.so.5
#33 0x00007f9fc6a88673 in QQuickLoader::qt_metacall(QMetaObject::Call, int, void**) () at /usr/lib64/libQt5Quick.so.5
#34 0x00007f9fc5cd98ca in QQmlVMEMetaObject::metaCall(QObject*, QMetaObject::Call, int, void**) () at /usr/lib64/libQt5Qml.so.5
#35 0x00007f9fc5ceef40 in QQmlPropertyData::writeProperty(QObject*, void*, QFlags<QQmlPropertyData::WriteFlag>) const () at /usr/lib64/libQt5Qml.so.5
#36 0x00007f9fc5ced6b2 in QQmlPropertyPrivate::write(QObject*, QQmlPropertyData const&, QVariant const&, QQmlContextData*, QFlags<QQmlPropertyData::WriteFlag>) () at /usr/lib64/libQt5Qml.so.5
#37 0x00007f9fc5cb7b5f in QV4::QObjectWrapper::setProperty(QV4::ExecutionEngine*, QObject*, QQmlPropertyData*, QV4::Value const&) () at /usr/lib64/libQt5Qml.so.5
#38 0x00007f9fc5cca990 in QV4::Runtime::method_setQmlQObjectProperty(QV4::ExecutionEngine*, QV4::Value const&, int, QV4::Value const&) () at /usr/lib64/libQt5Qml.so.5
#39 0x00007f9f19f81f98 in  ()
#40 0x00000000000001d0 in  ()
#41 0x0003800000000000 in  ()
#42 0x000055887b644710 in  ()
#43 0x00007fffc35d99b8 in  ()
#44 0x000000000000018e in  ()
#45 0x0000000000000000 in  ()

Still reproducible for me with Plasma 5.12.5.

I can consistently reproduce it simply by moving my mouse pointer over the "History" icon.

My best guess currently is a corrupted KActivities database unfortunately ...

(In reply to Eike Hein from comment #5)
> My best guess currently is a corrupted KActivities database unfortunately ...

OK, so why did you mark this as RESOLVED/FIXED?

Sorry, accidentally while juggling tabs.

If it's a corrupted KActivities database, then something must be consistently corrupting it, because I am experiencing this problem on two different machines -- one running Plasma 5.12.5 on openSUSE 15.0 and one running Plasma 5.13.0 on openSUSE Tumbleweed.  The Tumbleweed machine has exhibited the problem since at least Plasma 5.11.4.

Is there some way of clearing the KActivities database so that we can test if this is the problem?  If so, what sort of information is stored in this database?  (Anything I'm likely to miss?)

The db stores recently opened documents and recently launched apps (i.e. metadata), file<>activity associations (manually done by user), window<>activity associations (manually done by user) and menu favorites (also done by user).

I think Ivan is working on a scheme where corrupted db's are caught and auto-rolled-back to a periodical backup ...

Thank you for the report, Tristan.

As it has been a while since this was reported, can you please test and confirm if this issue is still occurring or if this bug report can be marked as resolved.

I have set the bug status to "needsinfo" pending your response, please change back to "reported" or "resolved/worksforme" when you respond, thank you.

I've no longer been able to reproduce this problem for a while now -- I'm currently using Plasma 5.20.3.