Java自旋锁
1、Java自旋锁理论
自旋锁（spinlock）：是指尝试去获取锁的线程不会立即阻塞，而是采用循环的方式去获取锁，这样的好处是减少线程上下文切换消耗，缺点是循环会消耗CPU。
代码示例：
public final int getAndAddInt(Object var1, long var2, int var4) {
int var5;
do {
var5 = this.getIntVolatile(var1, var2);
} while(!this.compareAndSwapInt(var1, var2, var5, var5 + var4));
return var5;
}
2、手写自旋锁
public class SpinlockDemo {
// AtomicReference对象创建初始值为null
private AtomicReference
public void lock() {
Thread currentThread = Thread.currentThread();
// 模拟自旋
while(!threadAtomicReference.compareAndSet(null,currentThread)) {
}
System.out.println(Thread.currentThread().getName()+"\t get lock");
}
public void unLock(){
Thread currentThread = Thread.currentThread();
threadAtomicReference.compareAndSet(currentThread,null);
System.out.println(Thread.currentThread().getName()+"\t release lock");
}
public static void main(String[] args) {
SpinlockDemo spinlockDemo = new SpinlockDemo();
// T1线程使用自旋方式获取锁，然后模拟5s业务处理
new Thread(()-> {
spinlockDemo.lock();
try {
System.out.println(Thread.currentThread().getName()+"\t开始模拟5s业务处理");
TimeUnit.SECONDS.sleep(5);
System.out.println(Thread.currentThread().getName()+"\t模拟5s业务处理完毕");
} catch (InterruptedException e) {
e.printStackTrace();
}
spinlockDemo.unLock();
},"T1").start();
// T1线程使用自旋方式获取锁，然后模拟3s业务处理
new Thread(()-> {
spinlockDemo.lock();
try {
System.out.println(Thread.currentThread().getName()+"\t开始模拟5s业务处理");
TimeUnit.SECONDS.sleep(5);
System.out.println(Thread.currentThread().getName()+"\t模拟5s业务处理完毕");
} catch (InterruptedException e) {
e.printStackTrace();
}
spinlockDemo.unLock();
},"T2").start();
}
}
程序执行结果如下：
