def locked(*args, **kwargs):
    """A locking **method** decorator.

    It will look for a provided attribute (typically a lock or a list
    of locks) on the first argument of the function decorated (typically this
    is the 'self' object) and before executing the decorated function it
    activates the given lock or list of locks as a context manager,
    automatically releasing that lock on exit.

    NOTE(harlowja): if no attribute name is provided then by default the
    attribute named '_lock' is looked for (this attribute is expected to be
    the lock/list of locks object/s) in the instance object this decorator
    is attached to.

    NOTE(harlowja): a custom logger (which will be used if lock release
    failures happen) can be provided by passing a logger instance for keyword
    argument ``logger``.
    """

    def decorator(f):
        attr_name = kwargs.get('lock', '_lock')
        logger = kwargs.get('logger')

        @six.wraps(f)
        def wrapper(self, *args, **kwargs):
            attr_value = getattr(self, attr_name)
            if isinstance(attr_value, (tuple, list)):
                with _utils.LockStack(logger=logger) as stack:
                    for i, lock in enumerate(attr_value):
                        if not stack.acquire_lock(lock):
                            raise threading.ThreadError("Unable to acquire"
                                                        " lock %s" % (i + 1))
                    return f(self, *args, **kwargs)
            else:
                lock = attr_value
                with lock:
                    return f(self, *args, **kwargs)

        return wrapper

    # This is needed to handle when the decorator has args or the decorator
    # doesn't have args, python is rather weird here...
    if kwargs or not args:
        return decorator
    else:
        if len(args) == 1:
            return decorator(args[0])
        else:
            return decorator