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/*
* 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.
*/
/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Written by Martin Buchholz with assistance from members of JCP
* JSR-166 Expert Group and released to the public domain, as
* explained at http://creativecommons.org/publicdomain/zero/1.0/
*/
/*
* @test
* @bug 8074773
* @summary Stress test looks for lost unparks
*/
import static java.util.concurrent.TimeUnit.SECONDS;
import java.util.SplittableRandom;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicReferenceArray;
import java.util.concurrent.locks.LockSupport;
public final class ParkLoops {
static final int THREADS = 4;
static final int ITERS = 30_000;
static class Parker implements Runnable {
static {
// Reduce the risk of rare disastrous classloading in first call to
// LockSupport.park: https://bugs.openjdk.java.net/browse/JDK-8074773
Class<?> ensureLoaded = LockSupport.class;
}
private final AtomicReferenceArray<Thread> threads;
private final CountDownLatch done;
private final SplittableRandom rnd;
Parker(AtomicReferenceArray<Thread> threads,
CountDownLatch done,
SplittableRandom rnd) {
this.threads = threads; this.done = done; this.rnd = rnd;
}
public void run() {
final Thread current = Thread.currentThread();
for (int k = ITERS, j; k > 0; k--) {
do {
j = rnd.nextInt(THREADS);
} while (!threads.compareAndSet(j, null, current));
do { // handle spurious wakeups
LockSupport.park();
} while (threads.get(j) == current);
}
done.countDown();
}
}
static class Unparker implements Runnable {
static {
// Reduce the risk of rare disastrous classloading in first call to
// LockSupport.park: https://bugs.openjdk.java.net/browse/JDK-8074773
Class<?> ensureLoaded = LockSupport.class;
}
private final AtomicReferenceArray<Thread> threads;
private final CountDownLatch done;
private final SplittableRandom rnd;
Unparker(AtomicReferenceArray<Thread> threads,
CountDownLatch done,
SplittableRandom rnd) {
this.threads = threads; this.done = done; this.rnd = rnd;
}
public void run() {
for (int n = 0; (n++ & 0xff) != 0 || done.getCount() > 0;) {
int j = rnd.nextInt(THREADS);
Thread parker = threads.get(j);
if (parker != null &&
threads.compareAndSet(j, parker, null)) {
LockSupport.unpark(parker);
}
}
}
}
public static void main(String[] args) throws Exception {
final SplittableRandom rnd = new SplittableRandom();
final ExecutorService pool = Executors.newCachedThreadPool();
final AtomicReferenceArray<Thread> threads
= new AtomicReferenceArray<>(THREADS);
final CountDownLatch done = new CountDownLatch(THREADS);
for (int i = 0; i < THREADS; i++) {
pool.submit(new Parker(threads, done, rnd.split()));
pool.submit(new Unparker(threads, done, rnd.split()));
}
// Let test harness handle timeout
done.await();
pool.shutdown();
pool.awaitTermination(Long.MAX_VALUE, SECONDS);
}
}
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