105 lines
4.0 KiB
Java
105 lines
4.0 KiB
Java
/*
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* Copyright (c) 2014, 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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/* @test
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* @bug 6853696
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* @summary ReferenceQueue#remove(timeout) should not return null before
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* timeout is elapsed
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*/
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import java.lang.InterruptedException;
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import java.lang.System;
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import java.lang.ref.Reference;
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import java.lang.ref.ReferenceQueue;
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import java.lang.ref.WeakReference;
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import java.util.concurrent.CountDownLatch;
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import static java.util.concurrent.TimeUnit.NANOSECONDS;
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/**
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* In order to demonstrate the issue we make several threads (two appears to be sufficient)
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* to block in ReferenceQueue#remove(timeout) at the same time.
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* Then, we force a reference to be enqueued by setting its referent to null and calling System.gc().
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* One of the threads gets the reference returned from the remove().
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* The other threads get null:
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* 1) with bug: this may happen before the specified timeout is elapsed,
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* 2) without bug: this can only happen after the timeout is fully elapsed.
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*/
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public class EarlyTimeout extends Thread {
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static final int THREADS_COUNT = 2;
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static final int TIMEOUT = 1000;
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static Object referent = new Object();
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static final ReferenceQueue<Object> queue = new ReferenceQueue<Object>();
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static final WeakReference<Object> weakReference = new WeakReference<Object>(referent, queue);
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static final CountDownLatch startedSignal = new CountDownLatch(THREADS_COUNT);
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long actual;
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Reference<?> reference;
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public static void main(String[] args) throws Exception {
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EarlyTimeout[] threads = new EarlyTimeout[THREADS_COUNT];
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for (int i = 0; i < THREADS_COUNT; ++i) {
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threads[i] = new EarlyTimeout();
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threads[i].start();
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}
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// The main thread waits until the threads has started and give it a chance
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// for the threads to block on the queue.remove(TIMEOUT) call
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startedSignal.await();
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Thread.sleep(TIMEOUT / 2);
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referent = null;
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System.gc();
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for (EarlyTimeout thread : threads) {
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thread.join();
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}
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if (weakReference.get() != null) {
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throw new RuntimeException("weakReference was not cleared");
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}
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int nonNullRefCount = 0;
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for (EarlyTimeout thread : threads) {
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if (thread.reference == null && thread.actual < TIMEOUT) {
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throw new RuntimeException("elapsed time " + thread.actual
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+ " is less than timeout " + TIMEOUT);
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}
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if (thread.reference != null && thread.reference == weakReference) {
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nonNullRefCount++;
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}
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}
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if (nonNullRefCount > 1) {
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throw new RuntimeException("more than one references were removed from queue");
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}
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}
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public void run() {
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try {
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startedSignal.countDown();
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long start = System.nanoTime();
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reference = queue.remove(TIMEOUT);
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actual = NANOSECONDS.toMillis(System.nanoTime() - start);
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} catch (InterruptedException ex) {
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throw new RuntimeException(ex);
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}
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}
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}
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