It is possible to be in this situation (from debugger, this condition is hit, and then Thread n is blocked)
Thread n
QLocalSocket::close() -> QWindowsPipeWriter::~QWindowsPipeWriter() -> terminate()
Thread QWindowsPipeWriter
emit bytesWritten(totalWritten);

Because Thread QWindowsPiperWriter is holding signalSlotLock(object of QWindowsPipeWriter) when emitting and be terminated, and then in Thread n
QWindowsPipeWriter::~QWindowsPipeWriter() -> QThread::~QThread() -> QObject::~Object() will always wait signalSlotLock(object of QWindowsPipeWriter) and be blocked.