Java 通过原子类 AtomicStampedReference 实现自旋锁

Posted 2022-03-06 夏秋初的学习笔记

参考

• 狂神说

介绍

自旋锁的定义：当一个线程尝试去获取某一把锁的时候，如果这个锁此时已经被别人获取(占用)，那么此线程就无法获取到这把锁，该线程将会等待，间隔一段时间后会再次尝试获取。这种采用循环加锁 -> 等待的机制被称为自旋锁(spinlock)。看完你就明白的锁系列之自旋锁
java.util.concurrent.atomic.AtomicStampedReference：AtomicStampedReference维护一个对象引用以及一个整数“标记”，可以原子方式更新。

代码

package lock;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicStampedReference;

/**
 * @Author 夏秋初
 * @Date 2022/3/5 11:51
 */
public class SpinLock 
    public static AtomicStampedReference<Thread> atomicStampedReference = new AtomicStampedReference(null, 0);
    /**
     * 自旋锁的简单实现
     */
    public static void lock()
        while (!atomicStampedReference.compareAndSet(null, Thread.currentThread(), 0, 1))

        
        System.out.println(Thread.currentThread().getName() + "加锁成功");
    
    public static void unLock()
        System.out.println(Thread.currentThread().getName() + "解锁成功");
        atomicStampedReference.compareAndSet( Thread.currentThread(), null, 1, 0);
    

    public static void main(String[] args) 
        new Thread(()->
            SpinLock.lock();
            try
                try 
                    TimeUnit.SECONDS.sleep(2);
                 catch (InterruptedException e) 
                    e.printStackTrace();
                
            finally 
                SpinLock.unLock();
            
        ,"A").start();
        new Thread(()->
            SpinLock.lock();
            try
                try 
                    TimeUnit.SECONDS.sleep(2);
                 catch (InterruptedException e) 
                    e.printStackTrace();
                
            finally 
                SpinLock.unLock();
            
        ,"B").start();
    

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