1 /*
2 * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24 /*
25 * @test
26 * @summary verify if the hidden class is unloaded when the class loader is GC'ed
27 * @library /test/lib/
28 * @build jdk.test.lib.util.ForceGC
29 * @run testng/othervm UnloadingTest
30 */
31
32 import java.io.IOException;
33 import java.lang.invoke.MethodHandles.Lookup;
34 import java.lang.ref.Reference;
35 import java.lang.ref.WeakReference;
36 import java.lang.reflect.Method;
37 import java.net.MalformedURLException;
38 import java.net.URL;
39 import java.net.URLClassLoader;
40 import java.nio.file.Files;
41 import java.nio.file.Path;
42 import java.nio.file.Paths;
43 import java.util.concurrent.atomic.AtomicInteger;
44
45 import jdk.test.lib.util.ForceGC;
46
47 import jdk.test.lib.compiler.CompilerUtils;
48 import jdk.test.lib.Utils;
49
50 import org.testng.annotations.BeforeTest;
51 import org.testng.annotations.Test;
52
53 import static java.lang.invoke.MethodHandles.lookup;
54 import static java.lang.invoke.MethodHandles.Lookup.ClassOption.*;
55 import static org.testng.Assert.*;
56
57 public class UnloadingTest {
58 private static final Path CLASSES_DIR = Paths.get("classes");
59 private static byte[] hiddenClassBytes;
60
61 @BeforeTest
62 static void setup() throws IOException {
63 Path src = Paths.get(Utils.TEST_SRC, "src", "LookupHelper.java");
64 if (!CompilerUtils.compile(src, CLASSES_DIR)) {
65 throw new RuntimeException("Compilation of the test failed: " + src);
66 }
67
68 hiddenClassBytes = Files.readAllBytes(CLASSES_DIR.resolve("LookupHelper.class"));
69 }
70
71 /*
72 * Test that a hidden class is unloaded while the loader remains strongly reachable
73 */
74 @Test
75 public void unloadable() throws Exception {
76 TestLoader loader = new TestLoader();
77 Class<?> helper = Class.forName("LookupHelper", true, loader);
78 Method m = helper.getMethod("getLookup");
79 Lookup lookup = (Lookup)m.invoke(null);
80 HiddenClassUnloader unloader = createHiddenClass(lookup, false);
81 // the hidden class should be unloaded
82 unloader.unload();
83
84 // loader is strongly reachable
85 Reference.reachabilityFence(loader);
86 }
87
88 /*
89 * Test that a hidden class is not unloaded when the loader is strongly reachable
90 */
91 @Test
92 public void notUnloadable() throws Exception {
93 TestLoader loader = new TestLoader();
94 Class<?> helper = Class.forName("LookupHelper", true, loader);
95 Method m = helper.getMethod("getLookup");
96 Lookup lookup = (Lookup)m.invoke(null);
97 HiddenClassUnloader unloader = createHiddenClass(lookup, true);
98 assertFalse(unloader.tryUnload()); // hidden class is not unloaded
99
100 // loader is strongly reachable
101 Reference.reachabilityFence(loader);
102 }
103
104 /*
105 * Create a nest of two hidden classes.
106 * They can be unloaded even the loader is strongly reachable
107 */
108 @Test
109 public void hiddenClassNest2() throws Exception {
110 TestLoader loader = new TestLoader();
111 Class<?> helper = Class.forName("LookupHelper", true, loader);
112 Method m = helper.getMethod("getLookup");
113 Lookup lookup = (Lookup)m.invoke(null);
114 HiddenClassUnloader[] unloaders = createNestOfTwoHiddenClasses(lookup, false, false);
115
116 // keep a strong reference to the nest member class
117 Class<?> member = unloaders[1].weakRef.get();
118 // nest host and member will not be unloaded
119 assertFalse(unloaders[0].tryUnload());
120 assertFalse(unloaders[1].tryUnload());
121
122 // clear the reference to the nest member
123 member = null;
124
125 // nest host and member will be unloaded
126 unloaders[0].unload();
127 unloaders[1].unload();
128
129 // loader is strongly reachable
130 Reference.reachabilityFence(loader);
131 }
132
133 /*
134 * Create a nest with a hidden class nest host and strong nest member.
135 * Test that both are not unloaded
136 */
137 @Test
138 public void hiddenClassNestStrongMember() throws Exception {
139 TestLoader loader = new TestLoader();
140 Class<?> helper = Class.forName("LookupHelper", true, loader);
141 Method m = helper.getMethod("getLookup");
142 Lookup lookup = (Lookup)m.invoke(null);
143 HiddenClassUnloader[] unloaders = createNestOfTwoHiddenClasses(lookup, false, true);
144 assertFalse(unloaders[0].tryUnload()); // nest host cannot be unloaded
145 assertFalse(unloaders[1].tryUnload()); // nest member cannot be unloaded
146
147 // loader is strongly reachable
148 Reference.reachabilityFence(loader);
149 }
150
151 /*
152 * Create a nest with a strong hidden nest host and a hidden class member.
153 * The nest member can be unloaded whereas the nest host will not be unloaded.
154 */
155 @Test
156 public void hiddenClassNestStrongHost() throws Exception {
157 TestLoader loader = new TestLoader();
158 Class<?> helper = Class.forName("LookupHelper", true, loader);
159 Method m = helper.getMethod("getLookup");
160 Lookup lookup = (Lookup)m.invoke(null);
161 HiddenClassUnloader[] unloaders = createNestOfTwoHiddenClasses(lookup, true, false);
162 assertFalse(unloaders[0].tryUnload()); // nest host cannot be unloaded
163 unloaders[1].unload();
164
165 // loader is strongly reachable
166 Reference.reachabilityFence(loader);
167 }
168
169 /*
170 * Create a HiddenClassUnloader that holds a weak reference to the newly created
171 * hidden class.
172 */
173 static HiddenClassUnloader createHiddenClass(Lookup lookup, boolean strong) throws Exception {
174 Class<?> hc;
175 if (strong) {
176 hc = lookup.defineHiddenClass(hiddenClassBytes, false, STRONG).lookupClass();
177 } else {
178 hc = lookup.defineHiddenClass(hiddenClassBytes, false).lookupClass();
179 }
180 assertTrue(hc.getClassLoader() == lookup.lookupClass().getClassLoader());
181 return new HiddenClassUnloader(hc);
182 }
183
184 /*
185 * Create an array of HiddenClassUnloader with two elements: the first element
186 * is for the nest host and the second element is for the nest member.
187 */
188 static HiddenClassUnloader[] createNestOfTwoHiddenClasses(Lookup lookup, boolean strongHost, boolean strongMember) throws Exception {
189 Lookup hostLookup;
190 if (strongHost) {
191 hostLookup = lookup.defineHiddenClass(hiddenClassBytes, false, STRONG);
192 } else {
193 hostLookup = lookup.defineHiddenClass(hiddenClassBytes, false);
194 }
195 Class<?> host = hostLookup.lookupClass();
196 Class<?> member;
197 if (strongMember) {
198 member = hostLookup.defineHiddenClass(hiddenClassBytes, false, NESTMATE, STRONG).lookupClass();
199 } else {
200 member = hostLookup.defineHiddenClass(hiddenClassBytes, false, NESTMATE).lookupClass();
201 }
202 assertTrue(member.getNestHost() == host);
203 return new HiddenClassUnloader[] { new HiddenClassUnloader(host), new HiddenClassUnloader(member) };
204 }
205
206 static class HiddenClassUnloader {
207 private final WeakReference<Class<?>> weakRef;
208 private HiddenClassUnloader(Class<?> hc) {
209 assertTrue(hc.isHiddenClass());
210 this.weakRef = new WeakReference<>(hc);
211 }
212
213 void unload() {
214 // Force garbage collection to trigger unloading of class loader and native library
215 ForceGC gc = new ForceGC();
216 assertTrue(gc.await(() -> weakRef.get() == null));
217
218 if (weakRef.get() != null) {
219 throw new RuntimeException("loader " + " not unloaded!");
220 }
221 }
222
223 boolean tryUnload() {
224 ForceGC gc = new ForceGC();
225 return gc.await(() -> weakRef.get() == null);
226 }
227 }
228
229 static class TestLoader extends URLClassLoader {
230 static URL[] toURLs() {
231 try {
232 return new URL[] { CLASSES_DIR.toUri().toURL() };
233 } catch (MalformedURLException e) {
234 throw new Error(e);
235 }
236 }
237
238 static AtomicInteger counter = new AtomicInteger();
239 TestLoader() {
240 super("testloader-" + counter.addAndGet(1), toURLs(), ClassLoader.getSystemClassLoader());
241 }
242 }
243 }