/* * Copyright (c) 2022, 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 Class unloading test with concurrent mark * @summary Make sure that verification during gc does not prevent class unloading * @bug 8280454 * @requires vm.gc.G1 * @requires vm.opt.final.ClassUnloading * @requires vm.opt.final.ClassUnloadingWithConcurrentMark * @modules java.base/jdk.internal.misc * @library /test/lib * @library classes * @build jdk.test.whitebox.WhiteBox test.Empty * @run driver jdk.test.lib.helpers.ClassFileInstaller jdk.test.whitebox.WhiteBox * @run main/othervm -Xbootclasspath/a:. -Xmn8m -XX:+UseG1GC -XX:+UnlockDiagnosticVMOptions -XX:+VerifyDuringGC -XX:+AlwaysTenure -XX:+WhiteBoxAPI -Xlog:gc,class+unload=debug UnloadTestWithVerifyDuringGC */ import jdk.test.whitebox.WhiteBox; import jdk.test.lib.classloader.ClassUnloadCommon; /** * Test that verifies that classes are unloaded using concurrent mark with G1 when they are no * longer reachable even when -XX:+VerifyDuringGC is enabled * * The test creates a class loader, uses the loader to load a class and creates an instance * of that class. The it nulls out all the references to the instance, class and class loader * and tries to trigger class unloading using a concurrent mark. Then it verifies that the class * is no longer loaded by the VM. */ public class UnloadTestWithVerifyDuringGC { private static final WhiteBox wb = WhiteBox.getWhiteBox(); private static void triggerUnloadingWithConcurrentMark() throws Exception { // Try to unload classes using concurrent mark. wb.g1RunConcurrentGC(); } private static String className = "test.Empty"; public static void main(String... args) throws Exception { ClassUnloadCommon.failIf(wb.isClassAlive(className), "is not expected to be alive yet"); ClassLoader cl = ClassUnloadCommon.newClassLoader(); Class c = cl.loadClass(className); Object o = c.newInstance(); ClassUnloadCommon.failIf(!wb.isClassAlive(className), "should be live here"); String loaderName = cl.getName(); int loadedRefcount = wb.getSymbolRefcount(loaderName); System.out.println("Refcount of symbol " + loaderName + " is " + loadedRefcount); // Move everything into the old gen so that concurrent mark can unload. wb.youngGC(); cl = null; c = null; o = null; triggerUnloadingWithConcurrentMark(); ClassUnloadCommon.failIf(wb.isClassAlive(className), "should have been unloaded"); int unloadedRefcount = wb.getSymbolRefcount(loaderName); System.out.println("Refcount of symbol " + loaderName + " is " + unloadedRefcount); ClassUnloadCommon.failIf(unloadedRefcount != (loadedRefcount - 1), "Refcount must be decremented"); } }