Create deadlock in Grand Central Dispatch

1.

dispatch_queue_t q = dispatch_queue_create("deadlock queue", DISPATCH_QUEUE_SERIAL);NSLog(@"1");dispatch_async(q, ^{    NSLog(@"2");    dispatch_sync(q, ^{        NSLog(@"3");    });    NSLog(@"4");});NSLog(@"5");

2.
dispatch_sync(dispatch_get_current_queue(), ^{
    NSLog(@"-------");
});