@synchronized doesn't retain monitored object under MRC

gistfile1.m

    __block id foo = [MyObject new];
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        NSLog(@"block entering synchronized");
        @synchronized(foo) {
            NSLog(@"running in synchronized");
            sleep(10);
            NSLog(@"running [foo self]");
            [foo self];
            NSLog(@"ran [foo self]");
        }
        NSLog(@"block exited synchronized");
    });
    sleep(1);
    NSLog(@"running at top level, releasing foo");
    [foo release];
    NSLog(@"running at top level, released foo");

Does this mean you should retain foo before @synchronized(foo) and release afterwards? Does that mean you need to wrap all of that in a try/catch in case it does throw so that foo can be released in that case too?