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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 id=default
* @summary Test virtual thread entering (and reentering) a lot of monitors with no contention
* @library /test/lib
* @run main LotsOfUncontendedMonitorEnter
*/
/*
* @test id=LM_LEGACY
* @library /test/lib
* @run main/othervm -XX:LockingMode=1 LotsOfUncontendedMonitorEnter
*/
/*
* @test id=LM_LIGHTWEIGHT
* @library /test/lib
* @run main/othervm -XX:LockingMode=2 LotsOfUncontendedMonitorEnter
*/
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;
import jdk.test.lib.thread.VThreadRunner;
public class LotsOfUncontendedMonitorEnter {
public static void main(String[] args) throws Exception {
int depth;
if (args.length > 0) {
depth = Integer.parseInt(args[0]);
} else {
depth = 24; // 33554430 enters
}
VThreadRunner.run(() -> {
testEnter(List.of(), depth);
});
}
/**
* Enter the monitor for a new object, reenter a monitor that is already held, and
* repeat to the given depth.
*/
private static void testEnter(List<Object> ownedMonitors, int depthRemaining) {
if (depthRemaining > 0) {
var lock = new Object();
synchronized (lock) {
// new list of owned monitors
var monitors = concat(ownedMonitors, lock);
testEnter(monitors, depthRemaining - 1);
// reenter a monitor that is already owned
int index = ThreadLocalRandom.current().nextInt(monitors.size());
var otherLock = monitors.get(index);
synchronized (otherLock) {
testEnter(monitors, depthRemaining - 1);
}
}
}
}
/**
* Adds an element to a list, returning a new list.
*/
private static <T> List<T> concat(List<T> list, T object) {
var newList = new ArrayList<>(list);
newList.add(object);
return newList;
}
}
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