public class ClhSpinLock {  
    private final ThreadLocal<Node> pred;  
    private final ThreadLocal<Node> node;  
    private final AtomicReference<Node> tail = new AtomicReference<Node>(new Node());  
  
    public ClhSpinLock() {  
        this.node = new ThreadLocal<Node>() {  
            protected Node initialValue() {  
                return new Node();  
            }  
        };  
  
        this.pred = new ThreadLocal<Node>() {  
            protected Node initialValue() {  
                return null;  
            }  
        };  
    }  
  
    public void lock() {  
        final Node node = this.node.get();  
        node.locked = true;  
        Node pred = this.tail.getAndSet(node);  
        this.pred.set(pred);  
        while (pred.locked) {}  
    }  
  
    public void unlock() {  
        final Node node = this.node.get();  
        node.locked = false;  
        this.node.set(this.pred.get());  
    }  
  
    private static class Node {  
        private volatile boolean locked;  
    }  
}