RFR: 8264760: JVM crashes when two threads encounter the same resolution error [v3]

[Wang Huang]

On Sat, 17 Apr 2021 07:40:05 GMT, Wang Huang <whuang at openjdk.org> wrote:

>> test/hotspot/jtreg/runtime/Nestmates/membership/TestNestHostErrorWithMultiThread.java line 58:
>> 
>>> 56:   public void test() throws Throwable {
>>> 57: 
>>> 58:     CountDownLatch latch = new CountDownLatch(1);
>> 
>> The use of CDL doesn't guarantee that both threads have reached the await() before the main thread does the countDown(). If you use a CyclicBarrier instead it will trip when the second thread arrives.
>
> @dholmes-ora

> The use of CDL doesn't guarantee that both threads have reached the await() before the main thread does the countDown(). If you use a CyclicBarrier instead it will trip when the second thread arrives.

I have tested a small case  the `CyclicBarrier ` version and `CountDownLatch ` version on `JDK17` & `JDK11`. It seems that :
* For `JDK17`, the wake-up time between two threads in the `CyclicBarrier ` version is bigger than the  `CountDownLatch ` version. In other words,   the  `CountDownLatch ` version can trigger this bug more easily .
* the `CyclicBarrier ` version and   the  `CountDownLatch ` version running under `JDK11`  have the same performance.

// CountDownLatch version 
public class TestCountDownLatch {

  public static void main(String args[]) {
    CountDownLatch latch1 = new CountDownLatch(1);
    CountDownLatch latch2 = new CountDownLatch(2);

    MyThread t1 = new MyThread(latch1, latch2);
    MyThread t2 = new MyThread(latch1, latch2);

    t1.start();
    t2.start();

    try {
      // waiting thread creation
      latch2.await();
      latch1.countDown();

      t1.join();
      t2.join();
    } catch (InterruptedException e) {}   

    System.out.println(Math.abs(t1.getAwakeTime() - t2.getAwakeTime()));
  }

  static class MyThread extends Thread {
    private CountDownLatch latch1;
    private CountDownLatch latch2;
		private long awaketime;

    MyThread(CountDownLatch latch1, CountDownLatch latch2) {
      this.latch1 = latch1;
      this.latch2 = latch2;
    }

    @Override
    public void run() {
      try {
        latch2.countDown();
        // Try to have all threads trigger the nesthost check at the same time
        latch1.await();
        awaketime = System.nanoTime();
      } catch (InterruptedException e) {}
    }

    public long getAwakeTime() {
      return awaketime; 
    }
  }
}



// CyclicBarrier version 
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.CyclicBarrier;

public class TestCyclicBarrier {

  public static void main(String args[]) {
    CyclicBarrier barrier = new CyclicBarrier(2);

    MyThread t1 = new MyThread(barrier);
    MyThread t2 = new MyThread(barrier);

    t1.start();
    t2.start();

    try {
      t1.join();
      t2.join();
    } catch (InterruptedException e) {}   

    System.out.println(Math.abs(t1.getAwakeTime() - t2.getAwakeTime()));
  }

  static class MyThread extends Thread {
    private CyclicBarrier barrier; 
		private long awaketime;

    MyThread(CyclicBarrier barrier) {
      this.barrier = barrier;
    }

    @Override
    public void run() {
      try {
        // Try to have all threads trigger the nesthost check at the same time
        barrier.await();
        awaketime = System.nanoTime();
      } catch (Exception e) {}
    }

    public long getAwakeTime() {
      return awaketime; 
    }
  }
}

* results:  
 - `CountDownLatch` against `CyclicBarrier`
 ```
  CountDownLatch: 3960
  CyclicBarrier: 3361280
  CountDownLatch: 6120
  CyclicBarrier: 3337540
  CountDownLatch: 6160
  CyclicBarrier: 3462920
  CountDownLatch: 9150
  CyclicBarrier: 3328090
  CountDownLatch: 6580
  CyclicBarrier: 3345450
  CountDownLatch: 6340
  CyclicBarrier: 3342900
  CountDownLatch: 1330
  CyclicBarrier: 3379210
  CountDownLatch: 7780
  CyclicBarrier: 3219020
  CountDownLatch: 2460
  CyclicBarrier: 3297020
  CountDownLatch: 7320
  CyclicBarrier: 3332770

-  `JDK17` against `CyclicBarrier`

CyclicBarrier jdk17: 3188590
CyclicBarrier jdk11: 49090
CyclicBarrier jdk17: 3123340
CyclicBarrier jdk11: 14680
CyclicBarrier jdk17: 3107910
CyclicBarrier jdk11: 780
CyclicBarrier jdk17: 3072600
CyclicBarrier jdk11: 1720
CyclicBarrier jdk17: 3164340
CyclicBarrier jdk11: 41020
CyclicBarrier jdk17: 3098490
CyclicBarrier jdk11: 7060
CyclicBarrier jdk17: 3058220
CyclicBarrier jdk11: 14750
CyclicBarrier jdk17: 3052460
CyclicBarrier jdk11: 660
CyclicBarrier jdk17: 3083650
CyclicBarrier jdk11: 14670
CyclicBarrier jdk17: 3116260
CyclicBarrier jdk11: 850

-------------

PR: https://git.openjdk.java.net/jdk/pull/3392