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8071507: (ref) Clear phantom reference as soft and weak references do
8143847: Remove REF_CLEANER reference category Reviewed-by: iris, dholmes, mchung, andrew Backport-of: ad6cdea5ae385623afa86251a8278c9c5274f4c1
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Poonam Bajaj
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Aug 11, 2022
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,101 @@ | ||
| /* | ||
| * Copyright (c) 2015, 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 8071507 | ||
| * @summary Test that PhantomReferences are cleared when notified. | ||
| * @run main/othervm PhantomReferentClearing | ||
| */ | ||
|
|
||
| import java.lang.ref.PhantomReference; | ||
| import java.lang.ref.ReferenceQueue; | ||
| import java.util.ArrayList; | ||
| import java.util.List; | ||
|
|
||
| public class PhantomReferentClearing { | ||
|
|
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| private static final long ENQUEUE_TIMEOUT = 1000; // 1 sec, in millis | ||
|
|
||
| // P1 & P2 are PhantomReference objects | ||
| // O1 & O2 are objects | ||
| // | ||
| // -> is a strong reference | ||
| // => is a referent reference | ||
| // | ||
| // root -> P1 | ||
| // root -> P2 | ||
| // root -> O1 | ||
| // root -> O2 | ||
| // O1 -> O2 | ||
| // P1 => O1 | ||
| // P2 => O2 | ||
| // | ||
| // (1) Remove root -> O1 and collect. P1 notified, P2 !notified. | ||
| // (2) Remove root -> O2 and collect. | ||
| // | ||
| // If phantom references are cleared when notified, as proposed by | ||
| // 8071507, then P2 should be notified, and the test passes. | ||
| // | ||
| // Otherwise, P2 does not get notified because it remains reachable | ||
| // from O1, which is being retained by P1. This fails the test. | ||
|
|
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| private static final ReferenceQueue<Object> Q1 = new ReferenceQueue<>(); | ||
| private static final ReferenceQueue<Object> Q2 = new ReferenceQueue<>(); | ||
|
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| private static volatile Object O2 = new Object(); | ||
| private static volatile List<Object> O1 = new ArrayList<>(); | ||
| static { | ||
| O1.add(O2); | ||
| } | ||
|
|
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| private static final PhantomReference<Object> P1 = new PhantomReference<>(O1, Q1); | ||
| private static final PhantomReference<Object> P2 = new PhantomReference<>(O2, Q2); | ||
|
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| public static void main(String[] args) throws InterruptedException { | ||
|
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| // Collect, and verify neither P1 or P2 notified. | ||
| System.gc(); | ||
| if (Q1.remove(ENQUEUE_TIMEOUT) != null) { | ||
| throw new RuntimeException("P1 already notified"); | ||
| } else if (Q2.poll() != null) { | ||
| throw new RuntimeException("P2 already notified"); | ||
| } | ||
|
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| // Delete root -> O1, collect, verify P1 notified, P2 not notified. | ||
| O1 = null; | ||
| System.gc(); | ||
| if (Q1.remove(ENQUEUE_TIMEOUT) == null) { | ||
| throw new RuntimeException("P1 not notified by O1 deletion"); | ||
| } else if (Q2.remove(ENQUEUE_TIMEOUT) != null) { | ||
| throw new RuntimeException("P2 notified by O1 deletion."); | ||
| } | ||
|
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| // Delete root -> O2, collect. P2 should be notified. | ||
| O2 = null; | ||
| System.gc(); | ||
| if (Q2.remove(ENQUEUE_TIMEOUT) == null) { | ||
| throw new RuntimeException("P2 not notified by O2 deletion"); | ||
| } | ||
| } | ||
| } |
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