Python multiprocessing 模块，forking() 实例源码

def _on_sigchld(self, watcher):
            """Callback of libev child watcher. Called when libev event loop
            catches corresponding SIGCHLD signal.
            """
            watcher.stop()
            # Status evaluation copied from `multiprocessing.forking` in Py2.7.
            if os.WIFSIGNALED(watcher.rstatus):
                self._popen.returncode = -os.WTERMSIG(watcher.rstatus)
            else:
                assert os.WIFEXITED(watcher.rstatus)
                self._popen.returncode = os.WEXITSTATUS(watcher.rstatus)
            self._returnevent.set()
            log.debug("SIGCHLD watcher callback for %s invoked. Exitcode "
                      "stored: %s", self.pid, self._popen.returncode)

def _make_nonblocking(self):
        if hasattr(gevent.os, 'make_nonblocking'):
            # On POSIX-compliant systems, the file descriptor flags are
            # inherited after forking, i.e. it is sufficient to make fd
            # nonblocking only once.
            gevent.os.make_nonblocking(self._fd)