5f13ffec66
ThreadGroup.enumerate(list,n,recurse) should never return a value that is less than n. Reviewed-by: clanger, chegar, prappo
116 lines
3.9 KiB
Java
116 lines
3.9 KiB
Java
/*
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* Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/**
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* @test
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* @summary enumerate(list,n,recurse) may return 0 if the group is being destroyed,
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* whereas it should never return a value < n. This lead to inconsistent
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* results if ThreadGroup::enumerate is called concurrently at the same
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* time that a child group is being destroyed. This is a race condition,
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* and this test will not always fail without the fix, but it does fail
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* often enough.
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* @bug 8219197
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*
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*/
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import java.util.concurrent.CountDownLatch;
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import java.util.concurrent.Semaphore;
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import java.util.concurrent.atomic.AtomicInteger;
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public class Destroy {
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static final class Task implements Runnable {
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final Semaphore sem;
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final CountDownLatch count;
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public Task(Semaphore sem, CountDownLatch count) {
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this.sem = sem;
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this.count = count;
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}
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@Override
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public void run() {
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try {
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count.countDown();
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sem.acquire();
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} catch (Throwable t) {
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t.printStackTrace();
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} finally {
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System.out.println(Thread.currentThread().getName()
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+ " exiting");
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}
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}
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}
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public static void main(String[] args) throws Exception {
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testDestroyChild();
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}
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public static void testDestroyChild() throws Exception {
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ThreadGroup root = new ThreadGroup("root");
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ThreadGroup parent = new ThreadGroup(root,"parent");
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ThreadGroup child1 = new ThreadGroup(parent, "child1");
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CountDownLatch count = new CountDownLatch(2);
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Semaphore sem1 = new Semaphore(1);
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Semaphore sem2 = new Semaphore(1);
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Thread t1 = new Thread(parent, new Task(sem1, count), "PT1");
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Thread t2 = new Thread(parent, new Task(sem2, count), "PT2");
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sem1.acquire();
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sem2.acquire();
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try {
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t1.start();
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t2.start();
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System.out.println("\nAwaiting parent threads...");
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count.await();
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Thread[] threads = new Thread[2];
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int nb = root.enumerate(threads, true);
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if (nb != 2) {
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throw new AssertionError("wrong number of threads: " + nb);
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}
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Thread t3 = new Thread(child1::destroy, "destroy");
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AtomicInteger nbr = new AtomicInteger();
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Thread t4 = new Thread("enumerate") {
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public void run() {
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Thread[] threads = new Thread[42];
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nbr.addAndGet(root.enumerate(threads, true));
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}
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};
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t4.start();
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t3.start();
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t4.join();
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t3.join();
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if (nbr.get() != nb) {
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throw new AssertionError("wrong number of threads: " + nbr.get());
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}
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} finally {
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sem1.release();
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sem2.release();
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}
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t1.join();
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t2.join();
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}
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}
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