iOS 线程同步 自旋锁 OSSpinLock

#import "ViewController.h"
#import <libkern/OSAtomic.h>
@interface ViewController ()
@property (nonatomic,assign)  int ticket;
//@property (nonatomic,assign)  OSSpinLock lock;
@end

@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
//    self.lock = OS_SPINLOCK_INIT;
    self.ticket=50;
    [self ticketsTest];
    // Do any additional setup after loading the view.
}
-(void)saleTicket{
    //静态创建、则不需要新建属性
    static OSSpinLock lock = OS_SPINLOCK_INIT;
    //若后面是个函数、则需
    /*
    static OSSpinLock lock = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        lock = OS_SPINLOCK_INIT;
    });
     */
    //其他线程执行到这里时，发现锁被加锁了 就会再这排队等待、直到这个锁被打开
    //加锁
    OSSpinLockLock(&lock);
    int ticket = self.ticket;
    sleep(.2);
    ticket--;
    self.ticket=ticket;
    NSLog(@"%d",self.ticket);
    //解锁
    OSSpinLockUnlock(&lock);
}
-(void)ticketsTest{
    dispatch_queue_t queue = dispatch_get_global_queue(0, 0);
    dispatch_async(queue, ^{
        for (int i =0; i<5; i++) {
            [self saleTicket];
        }
    });
    dispatch_async(queue, ^{
        for (int i =0; i<5; i++) {
            [self saleTicket];
        }
    });
}