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/*
* Copyright (c) 2022, 2023, 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
* @summary Test Thread.yield submits the virtual thread task to the expected queue
* @requires vm.continuations
* @run junit/othervm -Djdk.virtualThreadScheduler.maxPoolSize=1 YieldQueuing
*/
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.locks.LockSupport;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
class YieldQueuing {
/**
* Test Thread.yield submits the task for the current virtual thread to a scheduler
* submission queue when there are no tasks in the local queue.
*/
@Test
void testYieldWithEmptyLocalQueue() throws Exception {
var list = new CopyOnWriteArrayList<String>();
var threadsStarted = new AtomicBoolean();
var threadA = Thread.ofVirtual().unstarted(() -> {
// pin thread until task for B is in submission queue
while (!threadsStarted.get()) {
Thread.onSpinWait();
}
list.add("A");
Thread.yield(); // push task for A to submission queue, B should run
list.add("A");
});
var threadB = Thread.ofVirtual().unstarted(() -> {
list.add("B");
});
// push tasks for A and B to submission queue
threadA.start();
threadB.start();
// release A
threadsStarted.set(true);
// wait for result
threadA.join();
threadB.join();
assertEquals(list, List.of("A", "B", "A"));
}
/**
* Test Thread.yield submits the task for the current virtual thread to the local
* queue when there are tasks in the local queue.
*/
@Test
void testYieldWithNonEmptyLocalQueue() throws Exception {
var list = new CopyOnWriteArrayList<String>();
var threadsStarted = new AtomicBoolean();
var threadA = Thread.ofVirtual().unstarted(() -> {
// pin thread until tasks for B and C are in submission queue
while (!threadsStarted.get()) {
Thread.onSpinWait();
}
list.add("A");
LockSupport.park(); // B should run
list.add("A");
});
var threadB = Thread.ofVirtual().unstarted(() -> {
list.add("B");
LockSupport.unpark(threadA); // push task for A to local queue
Thread.yield(); // push task for B to local queue, A should run
list.add("B");
});
var threadC = Thread.ofVirtual().unstarted(() -> {
list.add("C");
});
// push tasks for A, B and C to submission queue
threadA.start();
threadB.start();
threadC.start();
// release A
threadsStarted.set(true);
// wait for result
threadA.join();
threadB.join();
threadC.join();
assertEquals(list, List.of("A", "B", "A", "B", "C"));
}
}
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