Return the socket to the pool, or if it's closed discard it.

def return_socket(self, sock_info):
        """Return the socket to the pool, or if it's closed discard it."""
        if self.pid != os.getpid():
            self.reset()
        else:
            if sock_info.pool_id != self.pool_id:
                sock_info.close()
            elif not sock_info.closed:
                sock_info.last_checkin = _time()
                with self.lock:
                    self.sockets.add(sock_info)

        self._socket_semaphore.release()
        with self.lock:
            self.active_sockets -= 1