process.py 文件源码

def initialize(cls, io_loop=None):
        """Initializes the ``SIGCHLD`` handler.

        The signal handler is run on an `.IOLoop` to avoid locking issues.
        Note that the `.IOLoop` used for signal handling need not be the
        same one used by individual Subprocess objects (as long as the
        ``IOLoops`` are each running in separate threads).

        .. versionchanged:: 4.1
           The ``io_loop`` argument is deprecated.
        """
        if cls._initialized:
            return
        if io_loop is None:
            io_loop = ioloop.IOLoop.current()
        cls._old_sigchld = signal.signal(
            signal.SIGCHLD,
            lambda sig, frame: io_loop.add_callback_from_signal(cls._cleanup))
        cls._initialized = True