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/*
* Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/* @test
* @summary Basic tests for making sure StableValue publishes values safely
* @modules java.base/jdk.internal.misc
* @enablePreview
* @run junit StableValuesSafePublicationTest
*/
import org.junit.jupiter.api.Test;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;
import static org.junit.jupiter.api.Assertions.*;
final class StableValuesSafePublicationTest {
private static final int SIZE = 100_000;
private static final int THREADS = Runtime.getRuntime().availableProcessors();
private static final StableValue<Holder>[] STABLES = stables();
static StableValue<Holder>[] stables() {
@SuppressWarnings("unchecked")
StableValue<Holder>[] stables = (StableValue<Holder>[]) new StableValue[SIZE];
for (int i = 0; i < SIZE; i++) {
stables[i] = StableValue.of();
}
return stables;
}
static final class Holder {
// These are non-final fields but should be seen
// fully initialized thanks to the HB properties of StableValue.
int a, b, c, d, e;
Holder() {
a = b = c = d = e = 1;
}
}
static final class Consumer implements Runnable {
final int[] observations = new int[SIZE];
final StableValue<Holder>[] stables = STABLES;
int i = 0;
@Override
public void run() {
for (; i < SIZE; i++) {
StableValue<Holder> s = stables[i];
Holder h;
// Wait until the StableValue has a holder value
while ((h = s.orElse(null)) == null) {}
int a = h.a;
int b = h.b;
int c = h.c;
int d = h.d;
int e = h.e;
observations[i] = a + (b << 1) + (c << 2) + (c << 3) + (d << 4) + (e << 5);
}
}
}
static final class Producer implements Runnable {
final StableValue<Holder>[] stables = STABLES;
@Override
public void run() {
StableValue<Holder> s;
long deadlineNs = System.nanoTime();
for (int i = 0; i < SIZE; i++) {
s = stables[i];
s.trySet(new Holder());
deadlineNs += 1000;
while (System.nanoTime() < deadlineNs) {
Thread.onSpinWait();
}
}
}
}
@Test
void main() {
List<Consumer> consumers = IntStream.range(0, THREADS)
.mapToObj(_ -> new Consumer())
.toList();
List<Thread> consumersThreads = IntStream.range(0, THREADS)
.mapToObj(i -> Thread.ofPlatform()
.name("Consumer Thread " + i)
.start(consumers.get(i)))
.toList();
Producer producer = new Producer();
Thread producerThread = Thread.ofPlatform()
.name("Producer Thread")
.start(producer);
join(consumers, producerThread);
join(consumers, consumersThreads.toArray(Thread[]::new));
int[] histogram = new int[64];
for (Consumer consumer : consumers) {
for (int i = 0; i < SIZE; i++) {
histogram[consumer.observations[i]]++;
}
}
// unless a = 1, ..., e = 1, zero observations should be seen
for (int i = 0; i < 63; i++) {
assertEquals(0, histogram[i]);
}
// a = 1, ..., e = 1 : index 2^5-1 = 63
// All observations should end up in this bucket
assertEquals(THREADS * SIZE, histogram[63]);
}
static void join(List<Consumer> consumers, Thread... threads) {
try {
for (Thread t:threads) {
long deadline = System.nanoTime() + TimeUnit.MINUTES.toNanos(1);
while (t.isAlive()) {
t.join(TimeUnit.SECONDS.toMillis(10));
if (t.isAlive()) {
String stack = Arrays.stream(t.getStackTrace())
.map(Objects::toString)
.collect(Collectors.joining(System.lineSeparator()));
System.err.println(t + ": " + stack);
for (int i = 0; i < consumers.size(); i++) {
System.err.println("Consumer " + i + ": " + consumers.get(i).i);
}
}
if (System.nanoTime() > deadline) {
long nonNulls = CompletableFuture.supplyAsync(() ->
Stream.of(STABLES)
.map(s -> s.orElse(null))
.filter(Objects::nonNull)
.count(), Executors.newSingleThreadExecutor()).join();
fail("Giving up! Set stables seen by a new thread: " + nonNulls);
}
}
}
} catch (InterruptedException ie) {
fail(ie);
}
}
}
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