Quelle EarlyTimeout.java Sprache: JAVA

/*
* 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);
        }
    }
}

quality89%

¤ Dauer der Verarbeitung: 0.24 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.