关于 epoll 的小小疑问， epoll 在等待事件的过程中会阻塞么

try:
    event_pairs = self._impl.poll(poll_timeout)
    except Exception as e:
    # Depending on python version and IOLoop implementation,
    # different exception types may be thrown and there are
    # two ways EINTR might be signaled:
    # * e.errno == errno.EINTR
    # * e.args is like (errno.EINTR, 'Interrupted system call')
        if errno_from_exception(e) == errno.EINTR:
            continue
        else:
            raise