Java 中的自旋锁

自旋锁

使用CAS+无限循环组成自旋锁。

原子引用类保存持有锁的线程，其他线程将使用CAS+自旋争夺锁。

示例代码

public class SpinLockDemo {
    AtomicReference<Thread> atomicReference = new AtomicReference<>();

    public void myLock () {
        Thread thread = Thread.currentThread();
        System.out.println(LocalDateTime.now() +"\t" + thread.getName() + "\t come in");
        while (!atomicReference.compareAndSet(null, thread)) {
            System.out.println(thread.getName() + "自旋中");
        }
    }

    public void myUnLock() {
        Thread thread = Thread.currentThread();
        atomicReference.compareAndSet(thread, null);
        System.out.println(LocalDateTime.now() +"\t" + thread.getName() + "\t invoke my unlock");
    }

    public static void main(String[] args) {
        SpinLockDemo spinLockDemo = new SpinLockDemo();

        new Thread(() -> {
            spinLockDemo.myLock();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            spinLockDemo.myUnLock();
        },"AAA").start();

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(() -> {
            spinLockDemo.myLock();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            spinLockDemo.myUnLock();
        }, "BBB").start();

    }

}

输出：

2021-03-28T18:50:49.923    AAA     come in
2021-03-28T18:50:50.870    BBB     come in
BBB自旋中
BBB自旋中
BBB自旋中
2021-03-28T18:50:50.937    AAA     invoke my unlock
2021-03-28T18:50:51.938    BBB     invoke my unlock