Gfrktyl

I'm still learning about concurrency, so I'm trying to figure out if this code, which I've modified, gives writers preference. I've been reading some possible solutions and apparently by having a reader locking the write lock then immediately release it we can provide write preference. Why is this?

Also, for clarity, LR and LW are class attributes in RW class.

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()