Не работает блокировка мьютекса Опции

[empirik]

Не могу понять, почему несмотря на mutex.lock(), потоки все равно выполняют один и тот же кусок кода одновременно. Есть диалоговое окно, которое по запросу потока должно появляться и позволять пользователю ввести сообщение. Когда сообщение введено и нажата кнопка "ОК", это сообщение должно быть получено этим самым потоком. Вот код:

class MyDialog(QtGui.QDialog):
    got_message = QtCore.pyqtSignal("QString")

    def __init__(self, *args, **kwargs):
        super(MyDialog, self).__init__(*args, **kwargs)

        self.setModal(True)
        self.message_label = QtGui.QLabel(u"Message")
        self.message_input = QtGui.QLineEdit()
        self.dialog_buttons = QtGui.QDialogButtonBox(QtGui.QDialogButtonBox.Ok | QtGui.QDialogButtonBox.Cancel)
        self.dialog_buttons.accepted.connect(self.accept)
        self.dialog_buttons.rejected.connect(self.reject)
        self.dialog_buttons.accepted.connect(self.on_accepted)
        self.hbox = QtGui.QHBoxLayout()
        self.hbox.addWidget(self.message_label)
        self.hbox.addWidget(self.message_input)
        self.vbox = QtGui.QVBoxLayout()
        self.vbox.addLayout(self.hbox)
        self.vbox.addWidget(self.dialog_buttons)
        self.setLayout(self.vbox)

        self.input_finished = QtCore.QWaitCondition()

    @QtCore.pyqtSlot()
    def show_input(self):
        print "showing input"
        self.show()
        self.setModal(True)

    @QtCore.pyqtSlot()
    def on_accepted(self):
        # print "emit: ", self.message_input.text()
        self.got_message.emit(self.message_input.text())
        self.input_finished.wakeAll()

class MyThread(QtCore.QThread):
    mutex = QtCore.QMutex()
    load_message_input = QtCore.pyqtSignal()

    def __init__(self, id, window):
        super(MyThread, self).__init__()
        self.id = id
        self.window = window
        # self.mutex = QtCore.QMutex()

    def run(self):
        print "Thread %d is started" % self.id
        MyThread.mutex.lock()
        self.get_captcha_value()
        print "Thread %d is finishing" % self.id

    def get_captcha_value(self):
        print "Thread %d locks mutex" % self.id
        self.load_message_input.connect(self.window.show_input, QtCore.Qt.BlockingQueuedConnection)
        self.load_message_input.emit()
        self.window.got_message.connect(self.print_message)
        self.window.input_finished.wait(MyThread.mutex)
        print "Thread %d unlocks mutex" % self.id
        MyThread.mutex.unlock()

    @QtCore.pyqtSlot("QString")
    def print_message(self, msg):
        print "Thread %d: %s" % (self.id, msg)


if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)

    window = test_qdialog.MyDialog()
    threads = []

    for i in range(5):
        thread = MyThread(i, window)
        if not thread.isRunning():
            thread.start()
            threads.append(thread)

    sys.exit(app.exec_())

При запуске в консоли получается так:

Thread 0 is startedThread 2 is started
 
 Thread 0 locks mutex
Thread 3 is startedThread 1 is started
Thread 4 is started

showing input
Thread 2 locks mutex
showing input
Thread 3 locks mutex
showing input
Thread 4 locks mutex
showing input
Thread 1 locks mutex
showing input
Thread 0: hello
Thread 2: hello
Thread 3: hello
Thread 4: hello
Thread 1: hello
Thread 0 unlocks mutex
Thread 0 is finishing
Thread 4 unlocks mutex
Thread 4 is finishingThread 3 unlocks mutex

Thread 3 is finishingThread 2 unlocks mutex

Thread 2 is finishing
Thread 1 unlocks mutex
Thread 1 is finishing