_communicate in Popen (subprocess.py) appears to sporadically hang on Apple M1 hardware

[waltstuart25]

Hi, I'm using 3.0.14 on Apple M1 hardware with Python 3.8.10 virtual environment. I'm experiencing sporadic but frequent hangs. When debugging the code, it appears that the hang results from the following while loop in _communicate never exiting:

                while selector.get_map():
                    timeout = self._remaining_time(endtime)
                    if timeout is not None and timeout < 0:
                        self._check_timeout(endtime, orig_timeout,
                                            stdout, stderr,
                                            skip_check_and_raise=True)
                        raise RuntimeError(  # Impossible :)
                            '_check_timeout(..., skip_check_and_raise=True) '
                            'failed to raise TimeoutExpired.')

                    ready = selector.select(timeout)
                    self._check_timeout(endtime, orig_timeout, stdout, stderr)

                    # XXX Rewrite these to use non-blocking I/O on the file
                    # objects; they are no longer using C stdio!

                    for key, events in ready:
                        if key.fileobj is self.stdin:
                            chunk = input_view[self._input_offset :
                                               self._input_offset + _PIPE_BUF]
                            try:
                                self._input_offset += os.write(key.fd, chunk)
                            except BrokenPipeError:
                                selector.unregister(key.fileobj)
                                key.fileobj.close()
                            else:
                                if self._input_offset >= len(self._input):
                                    selector.unregister(key.fileobj)
                                    key.fileobj.close()
                        elif key.fileobj in (self.stdout, self.stderr):
                            data = os.read(key.fd, 32768)
                            if not data:
                                selector.unregister(key.fileobj)
                                key.fileobj.close()
                            self._fileobj2output[key.fileobj].append(data)

            self.wait(timeout=self._remaining_time(endtime))

I can repeat this on many of the functions in the test code. Any ideas on this or whether pyboolnet 3.0.14 has been tested on M1 hardware?