def test_serial_parent_implicit_mp_fork_par_child_then_par_parent(self):
        """
        Implicit use of multiprocessing (will be fork, but cannot declare that
        in Py2.7 as there's no process launch context).
        Does this:
        1. Start with no OpenMP
        2. Fork to processes using OpenMP
        3. Join forks
        4. Run some OpenMP
        """
        body = """if 1:
            X = np.arange(1000000.)
            Y = np.arange(1000000.)
            q = multiprocessing.Queue()

            # this is ok
            procs = []
            for x in range(10):
                # fork() underneath with but no OpenMP in parent, this is ok
                proc = multiprocessing.Process(target = busy_func,
                                               args=(X, Y, q))
                procs.append(proc)
                proc.start()

            [p.join() for p in procs]

            # and this is still ok as the OpenMP happened in forks
            Z = busy_func(X, Y, q)
            try:
                q.get(False)
            except multiprocessing.queues.Empty:
                pass
            else:
                raise RuntimeError("Queue was not empty")
        """
        runme = self.template % body
        cmdline = [sys.executable, '-c', runme]
        out, err = self.run_cmd(cmdline)
        if self._DEBUG:
            print(out, err)

        Implicit use of multiprocessing (will be fork, but cannot declare that
        in Py2.7 as there's no process launch context).
        Does this:
        1. Start with no OpenMP
        2. Fork to processes using OpenMP
        3. Join forks
        4. Run some OpenMP
        
numba/tests/test_parallel_backend.py