KCM process hangs on exit with active output identifiers

[romangg]

When output identifiers are active while the KCM is closed the KCM process does not exit fully. Backtrace by GDB at this point:

#0  0x00007ffff45e105f in poll () from /usr/lib/libc.so.6
#1  0x00007ffff1c1d168 in ?? () from /usr/lib/libglib-2.0.so.0
#2  0x00007ffff1bce221 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#3  0x00007ffff4e1292d in QEventDispatcherGlib::processEvents (this=0x555555604450, flags=...) at /home/roman/dev/qt/src/qtbase/src/corelib/kernel/qeventdispatcher_glib.cpp:423
#4  0x00007ffff08b32ce in QXcbGlibEventDispatcher::processEvents (this=0x555555604450, flags=...) at /home/roman/dev/qt/src/qtbase/src/plugins/platforms/xcb/qxcbeventdispatcher.cpp:143
#5  0x00007ffff4d75bc7 in QEventLoop::processEvents (this=0x7fffffffd460, flags=...) at /home/roman/dev/qt/src/qtbase/src/corelib/kernel/qeventloop.cpp:139
#6  0x00007ffff4d75f29 in QEventLoop::exec (this=0x7fffffffd460, flags=...) at /home/roman/dev/qt/src/qtbase/src/corelib/kernel/qeventloop.cpp:232
#7  0x00007ffff4d79d9e in QCoreApplication::exec () at /home/roman/dev/qt/src/qtbase/src/corelib/kernel/qcoreapplication.cpp:1371
#8  0x00007ffff52c6196 in QGuiApplication::exec () at /home/roman/dev/qt/src/qtbase/src/gui/kernel/qguiapplication.cpp:1867
#9  0x00007ffff5ea6a25 in QApplication::exec () at /home/roman/dev/qt/src/qtbase/src/widgets/kernel/qapplication.cpp:2822
#10 0x000055555555e495 in main (_argc=2, _argv=0x7fffffffd698) at /home/roman/dev/kde/kde-cli-tools/src/kcmshell/main.cpp:329

Could be a bug in Qt.