I've a `kdevelop --ps` launcher. Somewhat often, I'll find an instance of kdevelop using one full core, even after all sessions have been quit.

backtrace:

#0  0x00007fd2396ccf8a in KDevelop::Bucket<KDevelop::AbstractTypeData, KDevelop::AbstractTypeDataRequest, true, 0u>::followerIndex(unsigned short) const (index=0, this=0x7fd1d81524d0)
    at /usr/src/debug/kdevplatform-5.1.1/serialization/itemrepository.h:941
#1  0x00007fd2396ccf8a in KDevelop::Bucket<KDevelop::AbstractTypeData, KDevelop::AbstractTypeDataRequest, true, 0u>::deleteItem<KDevelop::ItemRepository<KDevelop::AbstractTypeData, KDevelop::AbstractTypeDataRequest, true, true, 0u, 1048576u> >(unsigned short, unsigned int, KDevelop::ItemRepository<KDevelop::AbstractTypeData, KDevelop::AbstractTypeDataRequest, true, true, 0u, 1048576u>&) (repository=..., hash=<optimized out>, index=14586, this=0x7fd1d81524d0)
    at /usr/src/debug/kdevplatform-5.1.1/serialization/itemrepository.h:547
#2  0x00007fd2396ccf8a in KDevelop::Bucket<KDevelop::AbstractTypeData, KDevelop::AbstractTypeDataRequest, true, 0u>::finalCleanup<KDevelop::ItemRepository<KDevelop::AbstractTypeData, KDevelop::AbstractTypeDataRequest, true, true, 0u, 1048576u> >(KDevelop::ItemRepository<KDevelop::AbstractTypeData, KDevelop::AbstractTypeDataRequest, true, true, 0u, 1048576u>&) (repository=..., this=<optimized out>) at /usr/src/debug/kdevplatform-5.1.1/serialization/itemrepository.h:677
#3  0x00007fd2396ccf8a in KDevelop::ItemRepository<KDevelop::AbstractTypeData, KDevelop::AbstractTypeDataRequest, true, true, 0u, 1048576u>::finalCleanup() (this=<optimized out>)
    at /usr/src/debug/kdevplatform-5.1.1/serialization/itemrepository.h:2074
#4  0x00007fd2380468a1 in KDevelop::ItemRepositoryRegistry::finalCleanup() (this=<optimized out>) at /usr/src/debug/kdevplatform-5.1.1/serialization/itemrepositoryregistry.cpp:366
#5  0x00007fd239606149 in KDevelop::finalCleanup () at /usr/src/debug/kdevplatform-5.1.1/language/duchain/duchain.cpp:1585
#6  0x00007fd239606149 in KDevelop::DUChain::shutdown() (this=<optimized out>) at /usr/src/debug/kdevplatform-5.1.1/language/duchain/duchain.cpp:1623
#7  0x00007fd241a7c988 in KDevelop::Core::cleanup() (this=this@entry=0x562e0c59b980) at /usr/src/debug/kdevplatform-5.1.1/shell/core.cpp:461
#8  0x00007fd241a7cc08 in KDevelop::Core::shutdown() (this=0x562e0c59b980) at /usr/src/debug/kdevplatform-5.1.1/shell/core.cpp:412
#9  0x00007fd241a5c70d in KDevelop::MainWindow::~MainWindow() (this=this@entry=0x562e0c4a5fa0, __in_chrg=<optimized out>, __vtt_parm=<optimized out>) at /usr/src/debug/kdevplatform-5.1.1/shell/mainwindow.cpp:158
#10 0x00007fd241a5c769 in KDevelop::MainWindow::~MainWindow() (this=0x562e0c4a5fa0, __in_chrg=<optimized out>, __vtt_parm=<optimized out>) at /usr/src/debug/kdevplatform-5.1.1/shell/mainwindow.cpp:162
#11 0x00007fd23c2fa8f8 in QObject::event(QEvent*) () at /lib64/libQt5Core.so.5
#12 0x00007fd23cb640db in QWidget::event(QEvent*) () at /lib64/libQt5Widgets.so.5
#13 0x00007fd23cc5df2b in QMainWindow::event(QEvent*) () at /lib64/libQt5Widgets.so.5
#14 0x00007fd23f9bca57 in KMainWindow::event(QEvent*) () at /lib64/libKF5XmlGui.so.5
#15 0x00007fd23fa01a65 in KXmlGuiWindow::event(QEvent*) () at /lib64/libKF5XmlGui.so.5
#16 0x00007fd23cb1d5dc in QApplicationPrivate::notify_helper(QObject*, QEvent*) () at /lib64/libQt5Widgets.so.5
#17 0x00007fd23cb24c74 in QApplication::notify(QObject*, QEvent*) () at /lib64/libQt5Widgets.so.5
#18 0x00007fd23c2d2627 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /lib64/libQt5Core.so.5
#19 0x00007fd23c2d485b in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () at /lib64/libQt5Core.so.5
#20 0x00007fd23c320dd3 in postEventSourceDispatch(_GSource*, int (*)(void*), void*) () at /lib64/libQt5Core.so.5
#21 0x00007fd22e42d247 in g_main_context_dispatch () at /lib64/libglib-2.0.so.0
#22 0x00007fd22e42d5e8 in g_main_context_iterate.isra () at /lib64/libglib-2.0.so.0
#23 0x00007fd22e42d67c in g_main_context_iteration () at /lib64/libglib-2.0.so.0
#24 0x00007fd23c320e4f in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () at /lib64/libQt5Core.so.5
#25 0x00007fd23c2d160a in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () at /lib64/libQt5Core.so.5
#26 0x00007fd23c2d927c in QCoreApplication::exec() () at /lib64/libQt5Core.so.5
#27 0x0000562e0b89f2a7 in main(int, char**) (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/kdevelop-5.1.1/app/main.cpp:763