strange behavior of QBasicAtomicInt::testAndSetRelease

I am working on some code which ,after holding an exception returns 0. And after that executes some code ,which eventually throws exception: The call stack is : QBasicAtomicInt::testAndSetRelease(int expectedValue, int newValue)  Line 381 QMutex::unlock()  Line 382 + 0x11 bytes Looks like it happens from QMetaObject::activate@ it calls QMutex::unlock() twice. Is it always twice? In the code the debugger points to the exit of function :QBasicAtomicInt::testAndSetRelease(int expectedValue, int newValue). The values of expectedValue and newValue are strange (non valid) – 2806644 and 63243056 I have no idea how to proceed with that and investigate where /what causes to this behavior. Any advices? P.S. For me theoretically it looks like mutex which was not locked is unlock ….But if it is even correct – I have no idea how to find what mutex is that and what causes such behavior