/* * 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 threads entering a lot of monitors with contention * @requires vm.opt.LockingMode != 1 * @library /test/lib * @run main/othervm LotsOfContendedMonitorEnter */ /* * @test id=LM_LIGHTWEIGHT * @requires vm.opt.LockingMode != 1 * @library /test/lib * @run main/othervm -XX:LockingMode=2 LotsOfContendedMonitorEnter */ import java.util.concurrent.CountDownLatch; import jdk.test.lib.thread.VThreadRunner; public class LotsOfContendedMonitorEnter { public static void main(String[] args) throws Exception { int depth; if (args.length > 0) { depth = Integer.parseInt(args[0]); } else { depth = 1024; } VThreadRunner.run(() -> testContendedEnter(depth)); } /** * Enter the monitor for a new object, racing with another virtual thread that * attempts to enter around the same time, then repeat to the given depth. */ private static void testContendedEnter(int depthRemaining) throws Exception { if (depthRemaining > 0) { var lock = new Object(); // start thread to enter monitor for brief period, then enters again when signalled var started = new CountDownLatch(1); var signal = new CountDownLatch(1); var thread = Thread.ofVirtual().start(() -> { started.countDown(); // enter, may be contended synchronized (lock) { Thread.onSpinWait(); } // wait to be signalled try { signal.await(); } catch (InterruptedException e) { } // enter again, this will block until the main thread releases synchronized (lock) { // do nothing } }); try { // wait for thread to start started.await(); // enter, may be contended synchronized (lock) { // signal thread to enter monitor again, it should block signal.countDown(); await(thread, Thread.State.BLOCKED); testContendedEnter(depthRemaining - 1); } } finally { thread.join(); } } } /** * Waits for the given thread to reach a given state. */ private static void await(Thread thread, Thread.State expectedState) { Thread.State state = thread.getState(); while (state != expectedState) { assert state != Thread.State.TERMINATED : "Thread has terminated"; Thread.yield(); state = thread.getState(); } } }