闭锁这个词源于 jdk 1.5 中新增了一个类: CountDownLatch

A synchronization aid that allows one or more threads to wait until a set of operations being performed in other threads completes.

同步辅助类, 允许一个或多个线程等待直到其他线程的一系列操作完成, 才放开这些线程的执行

一直觉的go的 WaitGroup 和 java的闭锁比较像对比一下实现:

java 示例

  1. package com.tonny.thread;
  3. import java.util.concurrent.CountDownLatch;
  5. public class Driver { // ...
  6.     public  static void main(String[] args) throws InterruptedException {
  7.         int N = 10;
  8.         CountDownLatch startSignal = new CountDownLatch(1);
  9.         CountDownLatch doneSignal = new CountDownLatch(N);
  11.         for (int i = 0; i < N; ++i) // create and start threads
  12.             new Thread(new Worker(startSignal, doneSignal)).start();
  14.         System.out.println("main run =============");          // don't let run yet
  15.         startSignal.countDown();      // let all threads proceed
  16.         System.out.println("all start working");
  17.         doneSignal.await();           // wait for all to finish
  18.         System.out.println("all worker finished");
  19.     }
  20. }
  22. class Worker implements Runnable {
  23.     private final CountDownLatch startSignal;
  24.     private final CountDownLatch doneSignal;
  25.     Worker(CountDownLatch startSignal, CountDownLatch doneSignal) {
  26.         this.startSignal = startSignal;
  27.         this.doneSignal = doneSignal;
  28.     }
  29.     public void run() {
  30.         try {
  31.             startSignal.await();
  32.             doWork();
  33.             doneSignal.countDown();
  34.         } catch (InterruptedException ex) {} // return;
  35.     }
  37.     void doWork() {
  38.         System.out.println("I'm working");
  39.     }
  40. }

go 实现

两个 WaitGroup 实现

  1. func main() {
  3.     var wgstart sync.WaitGroup
  4.     var wgend sync.WaitGroup
  5.     N := 100
  6.     wgstart.Add(1)
  7.     for i := 0; i < N; i++ {
  8.         wgend.Add(1)
  9.         go func() {
  10.             wgstart.Wait()
  11.             fmt.Println("I.m working ...........")
  12.             wgend.Done()
  13.         }()
  14.     }
  15.     fmt.Println("all start working")
  16.     wgstart.Done()
  17.     wgend.Wait()
  18.     fmt.Println("all worker finished")
  19. }