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8175797: (ref) Reference::enqueue method should clear the reference o…
…bject before enqueuing

8178832: (ref) jdk.lang.ref.disableClearBeforeEnqueue property is ignored
8193780: (ref) Remove the undocumented "jdk.lang.ref.disableClearBeforeEnqueue" system property

Reviewed-by: mchung, kbarrett, iris
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Poonam Bajaj committed Apr 28, 2022
1 parent ad6cdea commit 330d63d2f9e18ba069e11868d4381059c66f480f
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Showing 3 changed files with 58 additions and 9 deletions.
@@ -1,5 +1,5 @@
/*
* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1997, 2017, 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
@@ -33,4 +33,9 @@
public FinalReference(T referent, ReferenceQueue<? super T> q) {
super(referent, q);
}

@Override
public boolean enqueue() {
throw new InternalError("should never reach here");
}
}
@@ -213,7 +213,6 @@ public void clear() {
this.referent = null;
}


/* -- Queue operations -- */

/**
@@ -230,8 +229,8 @@ public boolean isEnqueued() {
}

/**
* Adds this reference object to the queue with which it is registered,
* if any.
* Clears this reference object and adds it to the queue with which
* it is registered, if any.
*
* <p> This method is invoked only by Java code; when the garbage collector
* enqueues references it does so directly, without invoking this method.
@@ -241,10 +240,10 @@ public boolean isEnqueued() {
* it was not registered with a queue when it was created
*/
public boolean enqueue() {
this.referent = null;
return this.queue.enqueue(this);
}


/* -- Constructors -- */

Reference(T referent) {
@@ -255,5 +254,4 @@ public boolean enqueue() {
this.referent = referent;
this.queue = (queue == null) ? ReferenceQueue.NULL : queue;
}

}
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2011, 2017, 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
@@ -22,17 +22,22 @@
*/

/* @test
* @bug 4268317
* @bug 4268317 8175797
* @summary Test if Reference.enqueue() works properly with GC
* @run main ReferenceEnqueue
*/

import java.lang.ref.*;
import java.util.ArrayList;
import java.util.List;

public class ReferenceEnqueue {

public static void main(String args[]) throws Exception {
for (int i=0; i < 5; i++)
for (int i=0; i < 5; i++) {
new WeakRef().run();
new ExplicitEnqueue().run();
}
System.out.println("Test passed.");
}

@@ -76,4 +81,45 @@ void run() throws InterruptedException {
}
}
}

static class ExplicitEnqueue {
final ReferenceQueue<Object> queue = new ReferenceQueue<>();
final List<Reference<Object>> refs = new ArrayList<>();
final int iterations = 1000;

ExplicitEnqueue() {
this.refs.add(new SoftReference<>(new Object(), queue));
this.refs.add(new WeakReference<>(new Object(), queue));
// Can't test PhantomReference because get() always returns null.
}

void run() throws InterruptedException {
for (Reference<Object> ref : refs) {
if (ref.enqueue() == false) {
throw new RuntimeException("Error: enqueue failed");
}
if (ref.get() != null) {
throw new RuntimeException("Error: referent must be cleared");
}
}

System.gc();
for (int i = 0; refs.size() > 0 && i < iterations; i++) {
Reference<Object> ref = (Reference<Object>)queue.poll();
if (ref == null) {
System.gc();
Thread.sleep(100);
continue;
}

if (refs.remove(ref) == false) {
throw new RuntimeException("Error: unknown reference " + ref);
}
}

if (!refs.isEmpty()) {
throw new RuntimeException("Error: not all references are removed");
}
}
}
}

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