locks.py 文件源码

def acquire(self, timeout=None):
        """Decrement the counter. Returns a Future.

        Block if the counter is zero and wait for a `.release`. The Future
        raises `.TimeoutError` after the deadline.
        """
        waiter = Future()
        if self._value > 0:
            self._value -= 1
            waiter.set_result(_ReleasingContextManager(self))
        else:
            self._waiters.append(waiter)
            if timeout:
                def on_timeout():
                    waiter.set_exception(gen.TimeoutError())
                    self._garbage_collect()
                io_loop = ioloop.IOLoop.current()
                timeout_handle = io_loop.add_timeout(timeout, on_timeout)
                waiter.add_done_callback(
                    lambda _: io_loop.remove_timeout(timeout_handle))
        return waiter