請教多線程 GCD 關(guān)于異步同步與串行相關(guān)的問題

```

dispatch_queue_t queue = dispatch_queue_create("com.serial.com", DISPATCH_QUEUE_SERIAL);

? ? NSLog(@"1-%@",[NSThread currentThread]);

? ? dispatch_async(queue,^ {

? ? ? ? NSLog(@"2-%@",[NSThread currentThread]);

? ? ? ? dispatch_sync(queue,^{

? ? ? ? ? ? NSLog(@"3-%@",[NSThread currentThread]);

? ? ? ? });

? ? ? ? NSLog(@"4-%@",[NSThread currentThread]);

? ? });

? ? NSLog(@"5-%@",[NSThread currentThread]);?

``` ? ?print 152

執(zhí)行到?? ? ? ? dispatch_sync(queue,^{ 就結(jié)束了。