import threading
class Reader(threading.Thread):
    def run(self):
        while True:
            with RW.LW:
                pass

            with RW.LR:
                RW.read_count += 1

            readData(RW.data)

            with RW.LR:
                RW.read_count -= 1
                RW.LR.notify()

            doMoreWork()

class Writer(threading.Thread):
    def run(self):
        while True:
            with RW.LW:
                waiting = True
                while waiting:
                    with RW.LR:
                        if RW.read_count == 0:
                            updateData(Rw.data)
                            waiting = False
                        else:
                            # use wait/notify to avoid busy waiting
                            while RW.read_count != 0:
                                RW.LR.wait()
        doOtherWork()