test/jdk/java/lang/Thread/virtual/stress/GetStackTraceALotWhenParking.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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/**
 * @test
 * @summary Stress test asynchronous Thread.getStackTrace when parking
 * @requires vm.debug != true & vm.continuations
 * @modules java.base/java.lang:+open
 * @library /test/lib
 * @run main GetStackTraceALotWhenParking
 */

/**
 * @test
 * @requires vm.debug == true & vm.continuations
 * @modules java.base/java.lang:+open
 * @library /test/lib
 * @run main/timeout=300 GetStackTraceALotWhenParking 1000
 */

import java.time.Duration;
import java.time.Instant;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.LockSupport;
import jdk.test.lib.thread.VThreadScheduler;

public class GetStackTraceALotWhenParking {
    static class RoundRobinExecutor implements Executor, AutoCloseable {
        private final ExecutorService[] executors;
        private int next;

        RoundRobinExecutor() {
            var factory = Thread.ofPlatform().name("worker-", 1).daemon(true).factory();
            var executors = new ExecutorService[2];
            for (int i = 0; i < executors.length; i++) {
                executors[i] = Executors.newSingleThreadExecutor(factory);
            }
            this.executors = executors;
        }

        @Override
        public void execute(Runnable task) {
            executors[next].execute(task);
            next = (next + 1) % executors.length;
        }

        @Override
        public void close() {
            for (int i = 0; i < executors.length; i++) {
                executors[i].shutdown();
            }
        }
    }

    public static void main(String[] args) throws Exception {
        int iterations = args.length > 0 ? Integer.parseInt(args[0])  : 10_000;

        final int ITERATIONS = iterations;
        final int SPIN_NANOS = 5000;

        AtomicInteger count = new AtomicInteger();

        try (RoundRobinExecutor executor = new RoundRobinExecutor()) {
            ThreadFactory factory = VThreadScheduler.virtualThreadFactory(executor);

            Thread thread = factory.newThread(() -> {
                while (count.incrementAndGet() < ITERATIONS) {
                    long start = System.nanoTime();
                    while ((System.nanoTime() - start) < SPIN_NANOS) {
                        Thread.onSpinWait();
                    }
                    LockSupport.parkNanos(500_000);
                }
            });
            thread.start();

            long start = System.nanoTime();
            while (thread.isAlive()) {
                StackTraceElement[] stackTrace = thread.getStackTrace();
                // printStackTrace(stackTrace);
                Thread.sleep(5);
                if ((System.nanoTime() - start) > 500_000_000) {
                    System.out.format("%s => %d of %d%n", Instant.now(), count.get(), ITERATIONS);
                    start = System.nanoTime();
                }
            }

            int countValue = count.get();
            if (countValue != ITERATIONS) {
                throw new RuntimeException("count = " + countValue);
            }
        }
    }

    static void printStackTrace(StackTraceElement[] stackTrace) {
        if (stackTrace == null) {
            System.out.println("NULL");
        } else {
            for (var e : stackTrace) {
                System.out.println("\t" + e);
            }
        }
    }
}