def stop(self):
        """Call stop() on all child tasks, and ignore TaskError exceptions.
        Behavior depends on what the child tasks' stop() method does."""
        with self._lock_c:
            for task in self.taskset:
                try:
                    task.stop()

                except TaskError as e:
                    # Task does not have a way to stop it.
                    # TODO: notify who?
                    pass