一 前言
前面已经说到JUC中的锁主要是基于AQS实现，而AQS（AQS的内部结构 、AQS的设计与实现）在前面已经简单介绍过了。今天记录下JUC包下的锁是怎么基于AQS上实现的
二 同步锁
同步锁不是JUC中的锁但也顺便提下，它是由synchronized 关键字进行同步，实现对竞争资源互斥访问的锁。
同步锁的原理：对于每一个对象，有且仅有一个同步锁；不同的线程能共同访问该同步锁。在同一个时间点该同步锁能且只能被一个线程获取到，其他线程都得等待。
另外：synchronized是Java中的关键字且是内置的语言实现；它是在JVM层面上实现的，不但可以通过一些监控工具监控synchronized的锁定，而且在代码执行时出现异常，JVM会自动释放锁定；synchronized等待的线程会一直等待下去，不能响应中断。
三 JUC中的锁结构
相比同步锁，JUC包中的锁的功能更加强大，它为锁提供了一个框架，该框架允许更灵活地使用锁（它由自己实现、需要手动释放锁、能响应中断、可以多线程跑提高效率等）。下图是根据源码中查出画的类图，便知它提供的锁有好几种，下面一一分析。
四 可重入锁-ReentrantLock
重入锁ReentrantLock，顾名思义：就是支持重进入的锁，它表示该锁能够支持一个线程对资源的重复加锁。另外该锁孩纸获取锁时的公平和非公平性选择，所以它包含公平锁与非公平锁（它们两也可以叫可重入锁）。首先提出两个疑问：它怎么实现重进入呢？释放逻辑还跟AQS中一样吗？
非公平锁
final boolean nonfairTryAcquire(int acquires) { final Thread current = Thread.currentThread(); int c = getState(); if (c == 0) { if (compareAndSetState(0, acquires)) { setExclusiveOwnerThread(current); return true; } } // 同步状态已经被其他线程占用，则判断当前线程是否与被占用的线程是同一个线程，如果是同一个线程则允许获取，并state+1 else if (current == getExclusiveOwnerThread()) { int nextc = c + acquires; if (nextc < 0) // overflow throw new Error("Maximum lock count exceeded"); setState(nextc); return true; } return false; }
该方法增加了再次获取同步状态的处理逻辑：通过判断当前线程是否为获取锁的线程来决定获取操作是否成功。如果是获取锁的线程再次请求，则将同步状态值进行增加并返回true,表示获取同步状态成功。
protected final boolean tryRelease(int releases) { int c = getState() - releases; if (Thread.currentThread() != getExclusiveOwnerThread()) throw new IllegalMonitorStateException(); boolean free = false; if (c == 0) { free = true; setExclusiveOwnerThread(null); } setState(c); return free; }
上面代码是释放锁的代码。如果该锁被获取了n次，那么前（n-1）次都是返回false,直至state=0，将占有线程设置为null，并返回true,表示释放成功。
公平锁
公平锁与非公平锁有啥区别呢？ 还是从源码中分析吧。
protected final boolean tryAcquire(int acquires) { final Thread current = Thread.currentThread(); int c = getState(); if (c == 0) { // 区别：增加判断同步队列中当前节点是否有前驱节点的判断 if (!hasQueuedPredecessors() && compareAndSetState(0, acquires)) { setExclusiveOwnerThread(current); return true; } } // 一样支持重入 else if (current == getExclusiveOwnerThread()) { int nextc = c + acquires; if (nextc < 0) throw new Error("Maximum lock count exceeded"); setState(nextc); return true; } return false; }
与非公平锁的唯一不同就是增加了一个判断条件：判断同步队列中当前节点是否有前驱节点的判断，如果方法返回true,则表示有线程比当前线程更早地请求获取锁，因此需要等待前驱线程获取并释放锁之后才能继续获取锁。
公平锁与非公平锁的区别
从上面源码中得知，公平性锁保证了锁的获取按照FIFO原则，但是代价就是进行大量的线程切换。而非公平性锁，可能会造成线程“饥饿”（不会保证先进来的就会先获取），但是极少线程的切换，保证了更大的吞吐量。下面我们看下案例：
import org.junit.Test; import java.util.*; import java.util.concurrent.*; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; public class FairAndUnfairTest { private static Lock fairLock = new ReentrantLock2(true); private static Lock unFairLock = new ReentrantLock2(false); @Test public void fair() throws Exception{ testLock(fairLock); } @Test public void unFairLock() throws Exception{ testLock(unFairLock); } private static void testLock(Lock lock) throws InterruptedException, ExecutionException { ExecutorService threadPool = Executors.newFixedThreadPool(5); List<Future<Long>> list = new ArrayList<>(); for (int i = 0 ; i < 5; i++) { Future<Long> future = threadPool.submit(new Job(lock)); list.add(future); } long cost = 0; for (Future<Long> future : list) { cost += future.get(); } // 查看五个线程所需耗时的时间 System.out.println("cost:" + cost + " ms"); } private static class Job implements Callable<Long> { private Lock lock; public Job(Lock lock) { this.lock = lock; } @Override public Long call() throws Exception { long st = System.currentTimeMillis(); // 同一线程获取100锁 for (int i =0; i < 100; i ++) { lock.lock(); try { System.out.println("Lock by[" + Thread.currentThread().getId() + "]," + "Waiting by[" + printThread(((ReentrantLock2)lock).getQueuedThreads()) + "]"); } catch (Exception e) { e.printStackTrace(); } finally { lock.unlock(); } } // 返回100次所需的时间 return System.currentTimeMillis() - st; } private String printThread(Collection<Thread> list) { StringBuilder ids = new StringBuilder(); for (Thread t : list) { ids.append(t.getId()).append(","); } return ids.toString(); } } private static class ReentrantLock2 extends ReentrantLock { public ReentrantLock2(boolean fair) { super(fair); } public Collection<Thread> getQueuedThreads() { List<Thread> arrayList = new ArrayList<>(super.getQueuedThreads()); Collections.reverse(arrayList); return arrayList; } } }
非公平性锁的测试结果，cost:117 ms
Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[9],Waiting by[] Lock by[10],Waiting by[] Lock by[10],Waiting by[9,] Lock by[10],Waiting by[9,] Lock by[10],Waiting by[9,11,] Lock by[10],Waiting by[9,11,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[10],Waiting by[9,11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[9],Waiting by[11,12,13,] Lock by[11],Waiting by[12,13,] Lock by[11],Waiting by[12,13,] Lock by[11],Waiting by[12,13,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[11],Waiting by[12,13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[12],Waiting by[13,9,] Lock by[13],Waiting by[9,] Lock by[13],Waiting by[9,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[13],Waiting by[9,12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[9],Waiting by[12,] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] Lock by[12],Waiting by[] cost:117 ms
公平性锁的测试结果，cost:193 ms
Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[14],Waiting by[] Lock by[15],Waiting by[] Lock by[14],Waiting by[15,] Lock by[15],Waiting by[14,] Lock by[14],Waiting by[15,] Lock by[15],Waiting by[14,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,14,] Lock by[16],Waiting by[14,15,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,17,] Lock by[15],Waiting by[16,17,14,] Lock by[16],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,18,] Lock by[14],Waiting by[15,18,17,] Lock by[15],Waiting by[18,17,14,] Lock by[18],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,18,] Lock by[14],Waiting by[15,18,17,] Lock by[15],Waiting by[18,17,14,] Lock by[18],Waiting by[17,14,15,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,14,] Lock by[16],Waiting by[18,17,14,15,] Lock by[18],Waiting by[17,14,15,16,] Lock by[17],Waiting by[14,15,16,18,] Lock by[14],Waiting by[15,16,18,17,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,] Lock by[18],Waiting by[17,16,] Lock by[17],Waiting by[16,18,] Lock by[16],Waiting by[18,17,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,15,] Lock by[18],Waiting by[17,15,16,] Lock by[17],Waiting by[15,16,18,] Lock by[15],Waiting by[16,18,17,] Lock by[16],Waiting by[18,17,] Lock by[18],Waiting by[17,16,] Lock by[17],Waiting by[16,18,] Lock by[16],Waiting by[18,17,] Lock by[18],Waiting by[17,16,] Lock by[17],Waiting by[16,18,] Lock by[16],Waiting by[18,17,] Lock by[18],Waiting by[17,16,] Lock by[17],Waiting by[16,18,] Lock by[16],Waiting by[18,17,] Lock by[18],Waiting by[17,16,] Lock by[17],Waiting by[16,18,] Lock by[16],Waiting by[18,17,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[17,] Lock by[17],Waiting by[18,] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] Lock by[18],Waiting by[] cost:193 ms
五 读写锁
读写锁维护了一对锁，一个读锁和一个写锁，通过分离读锁和写锁，使得并发性相比一般的排他锁（同一时刻只允许一个线程进行访问）有了很大的提升。
下面我们看下它有啥特性：
| 特性 |
说明 |
| 公平性选择 |
支持非公平（默认）和公平的所获取方式，吞吐量还是非公平优于公平 |
| 可重入 |
该锁支持可重进入。 读线程在获取了读锁之后能够再次获取读锁。 写线程在获取了写锁之后能够再次获取写锁。 |
| 锁降级 |
遵循获取写锁、获取读锁在释放写锁的次序，写锁能够降级成读锁。 |
| 排他性 |
当写线程访问时，其他读写线程均被阻塞 |
另外读写锁是采取一个整型变量来维护多种状态。高16位表示读，低16位表示写。
// 偏移位 static final int SHARED_SHIFT = 16; static final int SHARED_UNIT = (1 << SHARED_SHIFT); // 读写线程允许占用的最大数 static final int MAX_COUNT = (1 << SHARED_SHIFT) - 1; // 独占标志 static final int EXCLUSIVE_MASK = (1 << SHARED_SHIFT) - 1;
下面从源码中找出这些特性，先看下写锁的实现：
1 protected final boolean tryAcquire(int acquires) { 2 3 Thread current = Thread.currentThread(); 4 int c = getState(); 5 // 表示独占个数，也就是与低16为进行与运算。 6 int w = exclusiveCount(c); 7 if (c != 0) { 8 // c！=0 且 w==0表示不存在写线程，但存在读线程 9 if (w == 0 || current != getExclusiveOwnerThread()) 10 return false; 11 if (w + exclusiveCount(acquires) > MAX_COUNT) 12 throw new Error("Maximum lock count exceeded"); 13 /** 14 * 获取写锁的条件： 15 * 不能存在读线程且当前线程是当前占用锁的线程(这里体现可重入性和排他性)； 16 * 当前占用锁的次数不能超过最大数 17 */ 18 setState(c + acquires); 19 return true; 20 } 21 if (writerShouldBlock() || 22 !compareAndSetState(c, c + acquires)) 23 return false; 24 setExclusiveOwnerThread(current); 25 return true; 26 } 27 static int exclusiveCount(int c) { return c & EXCLUSIVE_MASK; }
获取读锁源码如下：
protected final int tryAcquireShared(int unused) { Thread current = Thread.currentThread(); int c = getState(); /** * exclusiveCount(c) != 0: 表示有写线程在占用 * getExclusiveOwnerThread() != current : 当前占用锁的线程不是当前线程。 * 如果上面两个条件同时满足，则获取失败。 * 上面表明如果当前线程是拥有写锁的线程可以获取读锁（体现可重入和锁降级）。 */ if (exclusiveCount(c) != 0 && getExclusiveOwnerThread() != current) return -1; int r = sharedCount(c); if (!readerShouldBlock() && r < MAX_COUNT && compareAndSetState(c, c + SHARED_UNIT)) { if (r == 0) { firstReader = current; firstReaderHoldCount = 1; } else if (firstReader == current) { firstReaderHoldCount++; } else { HoldCounter rh = cachedHoldCounter; if (rh == null || rh.tid != getThreadId(current)) cachedHoldCounter = rh = readHolds.get(); else if (rh.count == 0) readHolds.set(rh); rh.count++; } return 1; } return fullTryAcquireShared(current); }