test/jdk/java/lang/Thread/virtual/MonitorEnterWaitOOME.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * version 2 for more details (a copy is included in the LICENSE file that
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/*
 * @test id=monitorenter
 * @bug 8345266
 * @summary Test OOM while trying to unmount vthread on monitorenter
 * @requires vm.continuations & vm.gc.G1 & vm.opt.DisableExplicitGC != "true"
 * @library /test/lib
 * @run main/othervm -XX:+UseG1GC -Xmx48M MonitorEnterWaitOOME false
 */

/*
 * @test id=timedwait
 * @summary Test OOM while trying to unmount vthread on Object.wait
 * @requires vm.continuations & vm.gc.G1 & vm.opt.DisableExplicitGC != "true"
 * @library /test/lib
 * @run main/othervm -XX:+UseG1GC -Xmx48M MonitorEnterWaitOOME true 5
 */

/*
 * @test id=untimedwait
 * @summary Test OOM while trying to unmount vthread on Object.wait
 * @requires vm.continuations & vm.gc.G1 & vm.opt.DisableExplicitGC != "true"
 * @library /test/lib
 * @run main/othervm -XX:+UseG1GC -Xmx48M MonitorEnterWaitOOME true 0
 */

import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;

import jdk.test.lib.thread.VThreadRunner;

public class MonitorEnterWaitOOME {
    static volatile Object data;
    static Thread.State dummyState = Thread.State.RUNNABLE; // load java.lang.Thread$State

    public static void main(String[] args) throws Throwable {
        final boolean testWait = args.length >= 1 ? Boolean.parseBoolean(args[0]) : false;
        final long timeout = testWait && args.length == 2 ? Long.parseLong(args[1]) : 0L;

        VThreadRunner.ensureParallelism(2);

        Thread vthread;
        var lock = new Object();
        var canFillHeap = new AtomicBoolean();
        var heapFilled = new AtomicBoolean();
        var heapCollected = new AtomicBoolean();
        var exRef = new AtomicReference<Throwable>();
        synchronized (lock) {
            vthread = Thread.ofVirtual().start(() -> {
                try {
                    awaitTrue(canFillHeap);
                    data = fillHeap();
                    heapFilled.set(true);
                    synchronized (lock) {
                        if (testWait) {
                            lock.wait(timeout);
                        }
                    }
                    data = null;
                    System.gc();
                    heapCollected.set(true);
                } catch (Throwable e) {
                    data = null;
                    System.gc(); // avoid nested OOME
                    exRef.set(e);
                }
            });
            canFillHeap.set(true);
            awaitTrue(heapFilled);
            awaitState(vthread, Thread.State.BLOCKED);
        }
        if (testWait && timeout == 0) {
            awaitState(vthread, Thread.State.WAITING);
            synchronized (lock) {
                lock.notify();
            }
        }
        joinVThread(vthread, heapCollected, exRef);
        assert exRef.get() == null;
    }

    private static Object[] fillHeap() {
        Object[] first = null, last = null;
        int size = 1 << 20;
        while (size > 0) {
            try {
                Object[] array = new Object[size];
                if (first == null) {
                    first = array;
                } else {
                    last[0] = array;
                }
                last = array;
            } catch (OutOfMemoryError oome) {
                size = size >>> 1;
            }
        }
        return first;
    }

    private static void awaitTrue(AtomicBoolean ready) {
        // Don't call anything that might allocate from the Java heap.
        while (!ready.get()) {
            Thread.onSpinWait();
        }
    }

    private static void awaitState(Thread thread, Thread.State expectedState) {
        // Don't call anything that might allocate from the Java heap.
        while (thread.getState() != expectedState) {
            Thread.onSpinWait();
        }
    }

    private static void joinVThread(Thread vthread, AtomicBoolean ready, AtomicReference<Throwable> exRef) throws Throwable {
        // Don't call anything that might allocate from the Java heap until ready is set.
        while (!ready.get()) {
            Throwable ex = exRef.get();
            if (ex != null) {
                throw ex;
            }
            Thread.onSpinWait();
        }
        vthread.join();
    }
}