ForkJoinPool JDK 11+

Test.java

import java.util.concurrent.*;

public class Test {
  static boolean triggerIssue = true;

  static ForkJoinPool fjp;

  static void hotSleep(int ms) {
    long until = System.nanoTime() + ms*1000_000;
    while (System.nanoTime() < until) { }
  }

  public static void main(String[] args) {
    int parallelism = (args.length > 0) ? Integer.parseInt(args[0]) : Runtime.getRuntime().availableProcessors();
    fjp = new ForkJoinPool(parallelism);

    for (int i = 0; i < 1000; i += 1) {
      if (i % 25 == 0)
        System.out.println("iteration " + i);

      hotSleep(25);

      long begin = System.nanoTime();

      if (!triggerIssue)
        fjp.execute(() -> hotSleep(205)); // this doesn't trigger the issue

      T t = new T(50);
      fjp.execute(t);
      t.join();

      long duration = (System.nanoTime() - begin) / 1000_000;
      if (duration > 200)
        System.out.println("  " + i + ": suspicious duration " + duration);
    }
  }

  static class T extends RecursiveAction {
    private static T[] noTs = {};

    int n;

    public T(int n) {
      this.n = n;
    }

    public void compute() {
      T[] subtasks = (n > 2) ? new T[] { new T(n / 2), new T(n / 2) } : noTs;
      
      for (T t : subtasks)
        t.fork();

      if (triggerIssue && n == 50)
        fjp.execute(() -> hotSleep(205));

      hotSleep(2);

      for (T t : subtasks)
        t.join();
    }
  }
}