/*

 * Copyright (c) 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

 * 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 8166188 8178813

 * @summary Test return of JNI weak global refs during concurrent

 * marking, verifying the use of the G1 load barrier to keep the

 * referent alive.

 * @key gc

 * @requires vm.gc.G1

 * @modules java.base

 * @library /test/lib

 * @build sun.hotspot.WhiteBox

 * @run main ClassFileInstaller sun.hotspot.WhiteBox

 *    sun.hotspot.WhiteBox$WhiteBoxPermission

 * @run main/othervm/native

 *    -Xbootclasspath/a:.

 *    -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI

 *    -XX:+UseG1GC -XX:MaxTenuringThreshold=2

 *    -Xint

 *    TestJNIWeakG1

 * @run main/othervm/native

 *    -Xbootclasspath/a:.

 *    -XX:+UnlockDiagnosticVMOptions -XX:+WhiteBoxAPI

 *    -XX:+UseG1GC -XX:MaxTenuringThreshold=2

 *    -Xcomp

 *    TestJNIWeakG1

 */

import sun.hotspot.WhiteBox;

import java.lang.ref.Reference;

public final class TestJNIWeakG1 {

    static {

        System.loadLibrary("TestJNIWeakG1");

    }

    private static final WhiteBox WB = WhiteBox.getWhiteBox();

    private static final class TestObject {

        public final int value;

        public TestObject(int value) {

            this.value = value;

        }

    }

    private volatile TestObject testObject = null;

    private static native void registerObject(Object o);

    private static native void unregisterObject();

    private static native Object getReturnedWeak();

    private static native Object getResolvedWeak();

    // resolve controls whether getObject returns an explicitly

    // resolved jweak value (when resolve is true), or returns the

    // jweak directly and invokes the implicit resolution in the

    // native call return value handling path (when resolve is false).

    private boolean resolve = true;

    TestJNIWeakG1(boolean resolve) {

        this.resolve = resolve;

    }

    private Object getObject() {

        if (resolve) {

            return getResolvedWeak();

        } else {

            return getReturnedWeak();

        }

    }

    // Create the test object and record it both strongly and weakly.

    private void remember(int value) {

        TestObject o = new TestObject(value);

        registerObject(o);

        testObject = o;

    }

    // Remove both strong and weak references to the current test object.

    private void forget() {

        unregisterObject();

        testObject = null;

    }

    // Repeatedly perform young-only GC until o is in the old generation.

    private void gcUntilOld(Object o) {

        while (!WB.isObjectInOldGen(o)) {

            WB.youngGC();

        }

    }

    // Verify the weakly recorded object

    private void checkValue(int value) throws Exception {

        Object o = getObject();

        if (o == null) {

            throw new RuntimeException("Weak reference unexpectedly null");

        }

        TestObject t = (TestObject)o;

        if (t.value != value) {

            throw new RuntimeException("Incorrect value");

        }

    }

    // Verify we can create a weak reference and get it back.

    private void checkSanity() throws Exception {

        System.out.println("running checkSanity");

        try {

            // Inhibit concurrent GC during this check.

            WB.requestConcurrentGCPhase("IDLE");

            int value = 5;

            try {

                remember(value);

                checkValue(value);

            } finally {

                forget();

            }

        } finally {

            // Remove request.

            WB.requestConcurrentGCPhase("ANY");

        }

    }

    // Verify weak ref value survives across collection if strong ref exists.

    private void checkSurvival() throws Exception {

        System.out.println("running checkSurvival");

        try {

            int value = 10;

            try {

                remember(value);

                checkValue(value);

                gcUntilOld(testObject);

                // Run a concurrent collection after object is old.

                WB.requestConcurrentGCPhase("CONCURRENT_CYCLE");

                WB.requestConcurrentGCPhase("IDLE");

                // Verify weak ref still has expected value.

                checkValue(value);

            } finally {

                forget();

            }

        } finally {

            // Remove request.

            WB.requestConcurrentGCPhase("ANY");

        }

    }

    // Verify weak ref cleared if no strong ref exists.

    private void checkClear() throws Exception {

        System.out.println("running checkClear");

        try {

            int value = 15;

            try {

                remember(value);

                checkValue(value);

                gcUntilOld(testObject);

                // Run a concurrent collection after object is old.

                WB.requestConcurrentGCPhase("CONCURRENT_CYCLE");

                WB.requestConcurrentGCPhase("IDLE");

                checkValue(value);

                testObject = null;

                // Run a concurrent collection after strong ref removed.

                WB.requestConcurrentGCPhase("CONCURRENT_CYCLE");

                WB.requestConcurrentGCPhase("IDLE");

                // Verify weak ref cleared as expected.

                Object recorded = getObject();

                if (recorded != null) {

                    throw new RuntimeException("expected clear");

                }

            } finally {

                forget();

            }

        } finally {

            // Remove request.

            WB.requestConcurrentGCPhase("ANY");

        }

    }

    // Verify weak ref not cleared if no strong ref at start of

    // collection but weak ref read during marking.

    private void checkShouldNotClear() throws Exception {

        System.out.println("running checkShouldNotClear");

        try {

            int value = 20;

            try {

                remember(value);

                checkValue(value);

                gcUntilOld(testObject);

                // Block concurrent cycle until we're ready.

                WB.requestConcurrentGCPhase("IDLE");

                checkValue(value);

                testObject = null; // Discard strong ref

                // Run through mark_from_roots.

                WB.requestConcurrentGCPhase("BEFORE_REMARK");

                // Fetch weak ref'ed object.  Should be kept alive now.

                Object recovered = getObject();

                if (recovered == null) {

                    throw new RuntimeException("unexpected clear during mark");

                }

                // Finish collection, including reference processing.

                // Block any further cycles while we finish check.

                WB.requestConcurrentGCPhase("IDLE");

                // Fetch weak ref'ed object.  Referent is manifestly

                // live in recovered; the earlier fetch should have

                // kept it alive through collection, so weak ref

                // should not have been cleared.

                if (getObject() == null) {

                    // 8166188 problem results in not doing the

                    // keep-alive of earlier getObject result, so

                    // recovered is now reachable but not marked.

                    // We may eventually crash.

                    throw new RuntimeException("cleared jweak for live object");

                }

                Reference.reachabilityFence(recovered);

            } finally {

                forget();

            }

        } finally {

            // Remove request.

            WB.requestConcurrentGCPhase("ANY");

        }

    }

    private void check() throws Exception {

        checkSanity();

        checkSurvival();

        checkClear();

        checkShouldNotClear();

        System.out.println("Check passed");

    }

    public static void main(String[] args) throws Exception {

        // Perform check with direct jweak resolution.

        System.out.println("Check with jweak resolved");

        new TestJNIWeakG1(true).check();

        // Perform check with implicit jweak resolution by native

        // call's return value handling.

        System.out.println("Check with jweak returned");

        new TestJNIWeakG1(false).check();

    }

}