jdk-24/test/jdk/sun/java2d/Disposer/TestDisposerRace.java

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import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Supplier;
import javax.swing.SwingUtilities;

import sun.java2d.Disposer;
import sun.java2d.DisposerRecord;

/**
 * @test
 * @bug 8289208
 * @summary Verifies Disposer robustness in a multi-threaded environment.
 * @run main/othervm -Xmx128m TestDisposerRace
 * @modules java.desktop/sun.java2d
 */
public final class TestDisposerRace {
    private static final AtomicInteger recordsCount = new AtomicInteger();
    private static volatile boolean disposerDone = false;

    private static final String KO_OVERFLOW = "Some records have not been disposed!";
    private static final String KO_UNDERFLOW = "Disposed more records than were added!";

    public static void main(String[] args) throws Exception {
        new TestDisposerRace().run();

        checkRecordsCountIsSane();
        if (recordsCount.get() > 0) {
            System.err.println(KO_OVERFLOW); // In case the next line fails to allocate due to OOME
            throw new RuntimeException("Some records (" + recordsCount + ") have not been disposed");
        }
    }

    interface ThrowingRunnable<E extends Exception> {
        void run() throws E;
    }

    TestDisposerRace() {
        addRecordsToDisposer(30_000);
    }

    void run() throws Exception {
        generateOOME();
        for (int i = 0; i < 1000; ++i) {
            retryOnOOME(() -> SwingUtilities.invokeAndWait(Disposer::pollRemove));

            // Adding records will race with the diposer trying to remove them
            if (i % 10 == 0)
                addRecordsToDisposer(1000);
        }

        retryOnOOME(() -> Disposer.addObjectRecord(new Object(), new FinalDisposerRecord()));

        while (!disposerDone) {
             generateOOME();
        }
    }

    private static void checkRecordsCountIsSane() {
        if (recordsCount.get() < 0) {
            throw new RuntimeException(KO_UNDERFLOW);
        }
    }

    private static <T> T retryOnOOME(Supplier<T> allocator) {
        for(;;) {
            try {
                return allocator.get();
            } catch (OutOfMemoryError ignored1) {
                try {
                    Thread.sleep(1); // Give GC a little chance to run
                } catch (InterruptedException ignored2) {}
            }
        }
    }

    private static <E extends Exception> void retryOnOOME(ThrowingRunnable<E> tr) throws E {
        for(;;) {
            try {
                tr.run();
                break;
            } catch (OutOfMemoryError ignored1) {
                try {
                    Thread.sleep(1); // Give GC a little chance to run
                } catch (InterruptedException ignored2) {}
            }
        }
    }

    private void addRecordsToDisposer(int count) {
        checkRecordsCountIsSane();

        MyDisposerRecord disposerRecord = retryOnOOME(MyDisposerRecord::new);

        while(count > 0) {
            recordsCount.incrementAndGet(); // pre-add to make sure it doesn't go negative
            var o = retryOnOOME(Object::new);
            retryOnOOME(() -> Disposer.addObjectRecord(o, disposerRecord));
            --count;
        }
    }

    class MyDisposerRecord implements DisposerRecord {
        public void dispose() {
            recordsCount.decrementAndGet();
        }
    }

    class FinalDisposerRecord implements DisposerRecord {
        public void dispose() {
            disposerDone = true;
        }
    }

    private static void giveGCAChance() {
        try {
            Thread.sleep(2000);
        } catch (InterruptedException ignored) {}
    }

    private static void generateOOME() throws Exception {
        try {
            final List<Object> leak = new LinkedList<>();
            while (true) {
                leak.add(new byte[1024 * 1024]);
            }
        } catch (OutOfMemoryError ignored) {}
        giveGCAChance();
    }
}