112 lines
3.8 KiB
Java
112 lines
3.8 KiB
Java
/*
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* Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* @test id=default
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* @summary Test virtual threads entering a lot of monitors with contention
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* @requires vm.opt.LockingMode != 1
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* @library /test/lib
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* @run main LotsOfContendedMonitorEnter
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*/
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/*
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* @test id=LM_LIGHTWEIGHT
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* @requires vm.opt.LockingMode != 1
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* @library /test/lib
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* @run main/othervm -XX:LockingMode=2 LotsOfContendedMonitorEnter
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*/
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import java.util.concurrent.CountDownLatch;
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import jdk.test.lib.thread.VThreadRunner;
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public class LotsOfContendedMonitorEnter {
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public static void main(String[] args) throws Exception {
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int depth;
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if (args.length > 0) {
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depth = Integer.parseInt(args[0]);
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} else {
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depth = 1024;
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}
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VThreadRunner.run(() -> testContendedEnter(depth));
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}
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/**
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* Enter the monitor for a new object, racing with another virtual thread that
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* attempts to enter around the same time, then repeat to the given depth.
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*/
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private static void testContendedEnter(int depthRemaining) throws Exception {
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if (depthRemaining > 0) {
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var lock = new Object();
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// start thread to enter monitor for brief period, then enters again when signalled
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var started = new CountDownLatch(1);
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var signal = new CountDownLatch(1);
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var thread = Thread.ofVirtual().start(() -> {
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started.countDown();
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// enter, may be contended
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synchronized (lock) {
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Thread.onSpinWait();
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}
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// wait to be signalled
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try {
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signal.await();
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} catch (InterruptedException e) { }
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// enter again, this will block until the main thread releases
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synchronized (lock) {
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// do nothing
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}
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});
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try {
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// wait for thread to start
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started.await();
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// enter, may be contended
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synchronized (lock) {
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// signal thread to enter monitor again, it should block
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signal.countDown();
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await(thread, Thread.State.BLOCKED);
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testContendedEnter(depthRemaining - 1);
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}
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} finally {
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thread.join();
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}
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}
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}
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/**
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* Waits for the given thread to reach a given state.
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*/
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private static void await(Thread thread, Thread.State expectedState) {
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Thread.State state = thread.getState();
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while (state != expectedState) {
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assert state != Thread.State.TERMINATED : "Thread has terminated";
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Thread.yield();
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state = thread.getState();
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}
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}
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}
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