unix_events.py 文件源码

def attach_loop(self, loop):
        assert loop is None or isinstance(loop, events.AbstractEventLoop)

        if self._loop is not None and loop is None and self._callbacks:
            warnings.warn(
                'A loop is being detached '
                'from a child watcher with pending handlers',
                RuntimeWarning)

        if self._loop is not None:
            self._loop.remove_signal_handler(signal.SIGCHLD)

        self._loop = loop
        if loop is not None:
            loop.add_signal_handler(signal.SIGCHLD, self._sig_chld)

            # Prevent a race condition in case a child terminated
            # during the switch.
            self._do_waitpid_all()