Linux: Test qqmlnotifier frequently hangs (every 8th time or so when executed in loop)

~"#0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:39\n"
>~"#1  0x00007f1412d2cc6f in _q_futex (addr=0x7f1413499508, op=0, val=3, timeout=0x0) at thread/qmutex_linux.cpp:154\n"
>~"#2  0x00007f1412d2ce3e in lockInternal_helper<false> (d_ptr=..., timeout=-1, elapsedTimer=0x0) at thread/qmutex_linux.cpp:195\n"
>~"#3  0x00007f1412d2cccb in QBasicMutex::lockInternal (this=0x7f1413499508) at thread/qmutex_linux.cpp:211\n"
>~"#4  0x00007f1412d2ca79 in QMutex::lock (this=0x7f1413499508) at thread/qmutex.cpp:225\n"
>~"#5  0x00007f1412d11b41 in QMutexLocker::QMutexLocker (this=0x7fff863f1990, m=0x7f1413499508) at ../../include/QtCore/../../src/corelib/thread/qmutex.h:130\n"
>~"#6  0x00007f1412fde86e in QObject::receivers (this=0x2309550, signal=0x2308399 \"qmlObjectPropChanged()\") at kernel/qobject.cpp:2265\n"
>~"#7  0x000000000040843b in ExportedClass::verifyReceiverCount (this=0x2309550) at tst_qqmlnotifier.cpp:101\n"
>~"#8  0x0000000000408ead in ExportedClass::disconnectNotify (this=0x2309550, signal=...) at tst_qqmlnotifier.cpp:137\n"
>~"#9  0x00007f1412fdc053 in QObject::~QObject (this=0x22e70c0, __in_chrg=<optimized out>) at kernel/qobject.cpp:902\n"
>~"#10 0x00007f1408ae9e56 in QQuickItem::~QQuickItem (this=0x22e70c0, __in_chrg=<optimized out>) at items/qquickitem.cpp:1984\n"
>~"#11 0x00007f1408b574bd in QQmlPrivate::QQmlElement<QQuickItem>::~QQmlElement (this=0x22e70c0, __in_chrg=<optimized out>) at /depot/fkleint/qt-5s/qtbase/include/QtQml/../../../
qtdeclarative/src/qml/qml/qqmlprivate.h:90\n"
>~"#12 0x00007f1408b574f6 in QQmlPrivate::QQmlElement<QQuickItem>::~QQmlElement (this=0x22e70c0, __in_chrg=<optimized out>) at /depot/fkleint/qt-5s/qtbase/include/QtQml/../../../
qtdeclarative/src/qml/qml/qqmlprivate.h:90\n"
>~"#13 0x00000000004052fb in tst_qqmlnotifier::createObjects (this=0x7fff863f2cd0) at tst_qqmlnotifier.cpp:194\n"
>~"#14 0x0000000000406743 in tst_qqmlnotifier::propertyChange (this=0x7fff863f2cd0) at tst_qqmlnotifier.cpp:298\n"
>~"#15 0x000000000040753b in tst_qqmlnotifier::qt_static_metacall (_o=0x7fff863f2cd0, _c=QMetaObject::InvokeMetaMethod, _id=8, _a=0x7fff863f2010) at .moc/tst_qqmlnotifier.moc:402
\n"
>~"#16 0x00007f1412fac387 in QMetaMethod::invoke (this=0x7fff863f22b0, object=0x7fff863f2cd0, connectionType=Qt::DirectConnection, returnValue=..., val0=..., val1=..., val2=..., 
val3=..., val4=..., val5=..., val6=..., val7=..., val8=..., val9=...) at kernel/qmetaobject.cpp:2169\n"
>~"#17 0x00007f1412fab843 in QMetaObject::invokeMethod (obj=0x7fff863f2cd0, member=0x1c4e0d0 \"propertyChange\", type=Qt::DirectConnection, ret=..., val0=..., val1=..., val2=...,
 val3=..., val4=..., val5=..., val6=..., val7=..., val8=..., val9=...) at kernel/qmetaobject.cpp:1464\n"
>~"#18 0x00007f1413cc8c6d in QMetaObject::invokeMethod (obj=0x7fff863f2cd0, member=0x1c4e0d0 \"propertyChange\", type=Qt::DirectConnection, val0=..., val1=..., val2=..., val3=...
, val4=..., val5=..., val6=..., val7=..., val8=..., val9=...) at ../../include/QtCore/../../src/corelib/kernel/qobjectdefs.h:395\n"
>~"#19 0x00007f1413cc49ca in QTest::qInvokeTestMethodDataEntry (slot=0x1c4e0d0 \"propertyChange\") at qtestcase.cpp:1692\n"
>~"#20 0x00007f1413cc5247 in QTest::qInvokeTestMethod (slotName=0x22f26a8 \"propertyChange()\", data=0x0) at qtestcase.cpp:1817\n"
>~"#21 0x00007f1413cc5ae3 in QTest::qInvokeTestMethods (testObject=0x7fff863f2cd0) at qtestcase.cpp:1971\n"
>~"#22 0x00007f1413cc5ff9 in QTest::qExec (testObject=0x7fff863f2cd0, argc=1, argv=0x7fff863f2e38) at qtestcase.cpp:2199\n"
>~"#23 0x0000000000406d18 in main (argc=1, argv=0x7fff863f2e38) at tst_qqmlnotifier.cpp:322\n"