Java并发编程JUC之手写自旋锁

川长思鸟来 2022-12-25 00:55 143阅读 0赞

自旋锁：spinlock，是指尝试获取锁的线程不会立即阻塞，而是采用循环的方式去尝试获取锁，这样的好处是减少线程上下文切换的消耗，缺点是循环会消耗CPU

原来提到的比较并交换，底层使用的就是自旋，自旋就是多次尝试，多次访问，不会阻塞的状态就是自旋。

/**
     * 自旋锁
     */
    public class SpinLockDemo {
    
    
        AtomicReference<Thread> atomicReference = new AtomicReference<Thread>();
    
        public void myLock() {
            Thread thread = Thread.currentThread();
            System.out.println(Thread.currentThread() + " come in!");
    
            while (!atomicReference.compareAndSet(null, thread)) {
    //            System.out.println("正在持有锁。。。。,ThreadName: "+Thread.currentThread());
            }
        }
    
    
        public void myUnLock() {
            Thread thread = Thread.currentThread();
    
            atomicReference.compareAndSet(thread, null);
    
            System.out.println(Thread.currentThread() + " invoked myUnLock!");
        }
    
    
        public static void main(String[] args) {
            SpinLockDemo spinLockDemo = new SpinLockDemo();
    
    
            Thread t1 = new Thread(new Runnable() {
                @Override
                public void run() {
                    spinLockDemo.myLock();
                    try {
                        TimeUnit.SECONDS.sleep(5);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    spinLockDemo.myUnLock();
                }
            });
    
            t1.setName("t1");
            t1.start();
    
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
    
    
            Thread t2 = new Thread(new Runnable() {
                @Override
                public void run() {
                    spinLockDemo.myLock();
                    spinLockDemo.myUnLock();
                }
            });
    
            t2.setName("t2");
            t2.start();
        }
    
    
    }