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