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/*
* Copyright (c) 2024, 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 8330748
* @summary Test ByteArrayOutputStream.writeTo releases carrier thread
* @requires vm.continuations
* @modules java.base/java.lang:+open
* @run main WriteToReleasesCarrier
*/
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;
import java.lang.reflect.Constructor;
import java.util.Arrays;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.LockSupport;
public class WriteToReleasesCarrier {
public static void main(String[] args) throws Exception {
byte[] bytes = "Hello".getBytes(StandardCharsets.UTF_8);
var baos = new ByteArrayOutputStream();
baos.write(bytes);
var target = new ParkingOutputStream();
try (ExecutorService scheduler = Executors.newFixedThreadPool(1)) {
Thread.Builder builder = virtualThreadBuilder(scheduler);
var started = new CountDownLatch(1);
var vthread1 = builder.start(() -> {
started.countDown();
try {
baos.writeTo(target);
} catch (IOException ioe) { }
});
try {
started.await();
await(vthread1, Thread.State.WAITING);
// carrier should be released, use it for another thread
var executed = new AtomicBoolean();
var vthread2 = builder.start(() -> {
executed.set(true);
});
vthread2.join();
if (!executed.get()) {
throw new RuntimeException("Second virtual thread did not run");
}
} finally {
LockSupport.unpark(vthread1);
vthread1.join();
}
}
if (!Arrays.equals(target.toByteArray(), bytes)) {
throw new RuntimeException("Expected bytes not written");
}
}
/**
* Waits for a thread to get to the expected state.
*/
private static void await(Thread thread, Thread.State expectedState) throws Exception {
Thread.State state = thread.getState();
while (state != expectedState) {
Thread.sleep(10);
state = thread.getState();
}
}
/**
* An OutputStream that parks when writing.
*/
static class ParkingOutputStream extends OutputStream {
final ByteArrayOutputStream baos = new ByteArrayOutputStream();
@Override
public void write(int i) {
LockSupport.park();
baos.write(i);
}
@Override
public void write(byte[] b, int off, int len) {
LockSupport.park();
baos.write(b, off, len);
}
byte[] toByteArray() {
return baos.toByteArray();
}
}
/**
* Returns a builder to create virtual threads that use the given scheduler.
*/
static Thread.Builder.OfVirtual virtualThreadBuilder(Executor scheduler) throws Exception {
Class<?> clazz = Class.forName("java.lang.ThreadBuilders$VirtualThreadBuilder");
Constructor<?> ctor = clazz.getDeclaredConstructor(Executor.class);
ctor.setAccessible(true);
return (Thread.Builder.OfVirtual) ctor.newInstance(scheduler);
}
}
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