GCD

    dispatch_queue_t queue=dispatch_queue_create("luoliping", DISPATCH_QUEUE_SERIAL);
    
    dispatch_async(queue, ^{
        NSLog(@"%@",[NSThread currentThread]);
        
    });
    
    dispatch_suspend(queue);
    dispatch_resume(queue);

    dispatch_async(queue, ^{
        NSLog(@"%@",[NSThread currentThread]);

    });
    
    dispatch_async(queue, ^{
        NSLog(@"%@",[NSThread currentThread]);
        
    });
    
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        NSLog(@"2-%d",[NSThread isMainThread]);
        
        dispatch_async(dispatch_get_main_queue(), ^{
            NSLog(@"2-%d",[NSThread isMainThread]);
            //刷新表
            [_tableView reloadData];
        });
    });