220 lines
8.3 KiB
Java
220 lines
8.3 KiB
Java
/*
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* Copyright (c) 2011, 2016, 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 4243978
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* @summary Test if Reference.enqueue() works properly with pending references
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*/
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import java.lang.ref.*;
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public class ReferenceEnqueuePending {
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static class NumberedWeakReference extends WeakReference<Integer> {
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// Add an integer to identify the weak reference object.
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int number;
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NumberedWeakReference(Integer referent, ReferenceQueue<Integer> q, int i) {
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super(referent, q);
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number = i;
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}
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}
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static final boolean debug = System.getProperty("test.debug") != null;
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static final int iterations = 1000;
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static final int gc_trigger = 99;
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static int[] a = new int[2 * iterations];
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// Keep all weak references alive with the following array.
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static NumberedWeakReference[] b = new NumberedWeakReference[iterations];
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public static void main(String[] argv) throws Exception {
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if (debug) {
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System.out.println("Starting the test.");
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}
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// Raise thread priority to match the referenceHandler
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// priority, so that they can race also on a uniprocessor.
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raisePriority();
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ReferenceQueue<Integer> refQueue = new ReferenceQueue<>();
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// Our objective is to let the mutator enqueue
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// a Reference object that may already be in the
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// pending state because of having been identified
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// as weakly reachable at a previous garbage collection.
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// To this end, we create many Reference objects, each with a
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// a unique integer object as its referant.
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// We let the referents become eligible for collection,
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// while racing with the garbage collector which may
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// have pended some of these Reference objects.
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// Finally we check that all of the Reference objects
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// end up on the their queue. The test was originally
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// submitted to show that such races could break the
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// pending list and/or the reference queue, because of sharing
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// the same link ("next") for maintaining both lists, thus
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// losing some of the Reference objects on either queue.
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Integer obj = new Integer(0);
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NumberedWeakReference weaky = new NumberedWeakReference(obj, refQueue, 0);
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for (int i = 1; i < iterations; i++) {
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// Create a new object, dropping the onlY strong reference to
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// the previous Integer object.
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obj = new Integer(i);
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// Trigger gc each gc_trigger iterations.
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if ((i % gc_trigger) == 0) {
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forceGc(0);
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}
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// Enqueue every other weaky.
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if ((i % 2) == 0) {
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weaky.enqueue();
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}
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// Remember the Reference objects, for testing later.
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b[i - 1] = weaky;
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// Get a new weaky for the Integer object just
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// created, which may be explicitly enqueued in
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// our next trip around the loop.
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weaky = new NumberedWeakReference(obj, refQueue, i);
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}
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// Do a final collection to discover and process all
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// Reference objects created above, allowing some time
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// for the ReferenceHandler thread to queue the References.
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forceGc(100);
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forceGc(100);
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// Verify that all WeakReference objects ended up queued.
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checkResult(refQueue, iterations-1);
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// Ensure the final weaky is live but won't be enqueued during
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// result checking, by ensuring its referent remains live.
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// This eliminates behavior changes resulting from different
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// compiler optimizations.
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Reference.reachabilityFence(weaky);
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Reference.reachabilityFence(obj);
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System.out.println("Test passed.");
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}
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private static NumberedWeakReference waitForReference(ReferenceQueue<Integer> queue) {
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try {
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return (NumberedWeakReference) queue.remove(30000); // 30sec
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} catch (InterruptedException ie) {
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return null;
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}
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}
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private static void checkResult(ReferenceQueue<Integer> queue,
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int expected) {
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if (debug) {
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System.out.println("Reading the queue");
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}
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// Empty the queue and record numbers into a[];
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NumberedWeakReference weakRead = waitForReference(queue);
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int length = 0;
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while (weakRead != null) {
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a[length++] = weakRead.number;
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if (length < expected) {
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weakRead = waitForReference(queue);
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} else { // Check for unexpected extra entries.
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weakRead = (NumberedWeakReference) queue.poll();
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}
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}
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if (debug) {
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System.out.println("Reference Queue had " + length + " elements");
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}
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// verify the queued references: all but the last Reference object
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// should have been in the queue.
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if (debug) {
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System.out.println("Start of final check");
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}
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// Sort the first "length" elements in array "a[]".
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sort(length);
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boolean fail = (length != expected);
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for (int i = 0; i < length; i++) {
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if (a[i] != i) {
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if (debug) {
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System.out.println("a[" + i + "] is not " + i + " but " + a[i]);
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}
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fail = true;
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}
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}
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if (fail) {
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printMissingElements(length, expected);
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throw new RuntimeException("TEST FAILED: only " + length
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+ " reference objects have been queued out of "
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+ expected);
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}
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}
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private static void printMissingElements(int length, int expected) {
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System.out.println("The following numbers were not found in the reference queue: ");
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int missing = 0;
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int element = 0;
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for (int i = 0; i < length; i++) {
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while ((a[i] != element) & (element < expected)) {
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System.out.print(element + " ");
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if (missing % 20 == 19) {
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System.out.println(" ");
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}
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missing++;
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element++;
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}
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element++;
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}
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System.out.print("\n");
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}
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private static void forceGc(long millis) throws InterruptedException {
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Runtime.getRuntime().gc();
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Thread.sleep(millis);
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}
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// Bubble sort the first "length" elements in array "a".
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private static void sort(int length) {
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int hold;
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if (debug) {
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System.out.println("Sorting. Length=" + length);
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}
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for (int pass = 1; pass < length; pass++) { // passes over the array
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for (int i = 0; i < length - pass; i++) { // a single pass
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if (a[i] > a[i + 1]) { // then swap
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hold = a[i];
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a[i] = a[i + 1];
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a[i + 1] = hold;
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}
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} // End of i loop
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} // End of pass loop
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}
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// Raise thread priority so as to increase the
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// probability of the mutator succeeding in enqueueing
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// an object that is still in the pending state.
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// This is (probably) only required for a uniprocessor.
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static void raisePriority() {
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Thread tr = Thread.currentThread();
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tr.setPriority(Thread.MAX_PRIORITY);
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}
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} // End of class ReferenceEnqueuePending
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