jdk

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/*
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 * Copyright (c) 2020, 2022, 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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package gc;
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/* @test
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 * @requires vm.gc != "Shenandoah" | vm.opt.ShenandoahGCMode != "iu"
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 * @library /test/lib
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 * @build jdk.test.whitebox.WhiteBox
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 * @run driver jdk.test.lib.helpers.ClassFileInstaller jdk.test.whitebox.WhiteBox
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 * @run main/othervm
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 *      -Xbootclasspath/a:.
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 *      -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI
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 *      gc.TestReferenceRefersToDuringConcMark
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 */
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import java.lang.ref.Reference;
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import java.lang.ref.WeakReference;
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import jdk.test.whitebox.WhiteBox;
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public class TestReferenceRefersToDuringConcMark {
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    private static final WhiteBox WB = WhiteBox.getWhiteBox();
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    private static volatile Object testObject = null;
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    private static WeakReference<Object> testWeak = null;
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    private static void setup() {
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        testObject = new Object();
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        testWeak = new WeakReference<Object>(testObject);
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    }
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    private static void gcUntilOld(Object o) throws Exception {
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        if (!WB.isObjectInOldGen(o)) {
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            WB.fullGC();
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            if (!WB.isObjectInOldGen(o)) {
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                fail("object not promoted by full gc");
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            }
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        }
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    }
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    private static void gcUntilOld() throws Exception {
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        gcUntilOld(testObject);
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        gcUntilOld(testWeak);
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    }
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    private static void fail(String msg) throws Exception {
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        throw new RuntimeException(msg);
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    }
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    private static void expectNotCleared(Reference<Object> ref,
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                                         String which) throws Exception {
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        if (ref.refersTo(null)) {
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            fail("expected " + which + " to not be cleared");
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        }
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    }
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    private static void expectValue(Reference<Object> ref,
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                                    Object value,
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                                    String which) throws Exception {
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        expectNotCleared(ref, which);
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        if (!ref.refersTo(value)) {
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            fail(which + " doesn't refer to expected value");
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        }
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    }
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    private static void checkInitialStates() throws Exception {
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        expectValue(testWeak, testObject, "testWeak");
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    }
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    private static void discardStrongReferences() {
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        testObject = null;
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    }
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    private static void testConcurrentCollection() throws Exception {
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        setup();
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        gcUntilOld();
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        WB.concurrentGCAcquireControl();
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        try {
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            checkInitialStates();
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            discardStrongReferences();
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            WB.concurrentGCRunTo(WB.BEFORE_MARKING_COMPLETED);
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            // For most collectors - the configurations tested here -,
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            // calling get() will keep testObject alive.
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            if (testWeak.get() == null) {
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                fail("testWeak unexpectedly == null");
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            }
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            WB.concurrentGCRunToIdle();
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            expectNotCleared(testWeak, "testWeak");
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        } finally {
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            WB.concurrentGCReleaseControl();
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        }
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    }
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    public static void main(String[] args) throws Exception {
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        if (WB.supportsConcurrentGCBreakpoints()) {
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            testConcurrentCollection();
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        }
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    }
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}
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