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 * @modules jdk.compiler
28 * @library /test/lib/
29 * @build jdk.test.lib.util.ForceGC
30 * @run testng/othervm UnloadingTest
31 */
32
33 import java.io.IOException;
34 import java.lang.invoke.MethodHandles.Lookup;
35 import java.lang.ref.Reference;
36 import java.lang.ref.WeakReference;
37 import java.lang.reflect.Method;
38 import java.net.MalformedURLException;
39 import java.net.URL;
40 import java.net.URLClassLoader;
41 import java.nio.file.Files;
42 import java.nio.file.Path;
43 import java.nio.file.Paths;
44 import java.util.concurrent.atomic.AtomicInteger;
45
46 import jdk.test.lib.util.ForceGC;
47
48 import jdk.test.lib.compiler.CompilerUtils;
49 import jdk.test.lib.Utils;
50
51 import org.testng.annotations.BeforeTest;
52 import org.testng.annotations.Test;
53
54 import static java.lang.invoke.MethodHandles.lookup;
55 import static java.lang.invoke.MethodHandles.Lookup.ClassOption.*;
56 import static org.testng.Assert.*;
57
58 public class UnloadingTest {
59 private static final Path CLASSES_DIR = Paths.get("classes");
60 private static byte[] hiddenClassBytes;
61
62 @BeforeTest
63 static void setup() throws IOException {
64 Path src = Paths.get(Utils.TEST_SRC, "src", "LookupHelper.java");
65 if (!CompilerUtils.compile(src, CLASSES_DIR)) {
66 throw new RuntimeException("Compilation of the test failed: " + src);
67 }
68
69 hiddenClassBytes = Files.readAllBytes(CLASSES_DIR.resolve("LookupHelper.class"));
70 }
71
72 /*
73 * Test that a hidden class is unloaded while the loader remains strongly reachable
74 */
75 @Test
76 public void unloadable() throws Exception {
77 TestLoader loader = new TestLoader();
78 Class<?> helper = Class.forName("LookupHelper", true, loader);
79 Method m = helper.getMethod("getLookup");
80 Lookup lookup = (Lookup)m.invoke(null);
81 HiddenClassUnloader unloader = createHiddenClass(lookup, false);
82 // the hidden class should be unloaded
83 unloader.unload();
84
85 // loader is strongly reachable
86 Reference.reachabilityFence(loader);
87 }
88
89 /*
90 * Test that a hidden class is not unloaded when the loader is strongly reachable
91 */
92 @Test
93 public void notUnloadable() throws Exception {
94 TestLoader loader = new TestLoader();
95 Class<?> helper = Class.forName("LookupHelper", true, loader);
96 Method m = helper.getMethod("getLookup");
97 Lookup lookup = (Lookup)m.invoke(null);
98 HiddenClassUnloader unloader = createHiddenClass(lookup, true);
99 assertFalse(unloader.tryUnload()); // hidden class is not unloaded
100
101 // loader is strongly reachable
102 Reference.reachabilityFence(loader);
103 }
104
105 /*
106 * Create a nest of two hidden classes.
107 * They can be unloaded even the loader is strongly reachable
108 */
109 @Test
110 public void hiddenClassNest() throws Exception {
111 TestLoader loader = new TestLoader();
112 Class<?> helper = Class.forName("LookupHelper", true, loader);
113 Method m = helper.getMethod("getLookup");
114 Lookup lookup = (Lookup)m.invoke(null);
115 HiddenClassUnloader[] unloaders = createNestOfTwoHiddenClasses(lookup, false, false);
116
117 // keep a strong reference to the nest member class
118 Class<?> member = unloaders[1].weakRef.get();
119 assertTrue(member != null);
120 // nest host and member will not be unloaded
121 assertFalse(unloaders[0].tryUnload());
122 assertFalse(unloaders[1].tryUnload());
123
124 // clear the reference to the nest member
125 Reference.reachabilityFence(member);
126 member = null;
127
128 // nest host and member will be unloaded
129 unloaders[0].unload();
130 unloaders[1].unload();
131
132 // loader is strongly reachable
133 Reference.reachabilityFence(loader);
134 }
135
136 /*
137 * Create a nest with a hidden class nest host and strong nest member.
138 * Test that both are not unloaded
139 */
140 @Test
141 public void hiddenClassNestStrongMember() throws Exception {
142 TestLoader loader = new TestLoader();
143 Class<?> helper = Class.forName("LookupHelper", true, loader);
144 Method m = helper.getMethod("getLookup");
145 Lookup lookup = (Lookup)m.invoke(null);
146 HiddenClassUnloader[] unloaders = createNestOfTwoHiddenClasses(lookup, false, true);
147 assertFalse(unloaders[0].tryUnload()); // nest host cannot be unloaded
148 assertFalse(unloaders[1].tryUnload()); // nest member cannot be unloaded
149
150 // loader is strongly reachable
151 Reference.reachabilityFence(loader);
152 }
153
154 /*
155 * Create a nest with a strong hidden nest host and a hidden class member.
156 * The nest member can be unloaded whereas the nest host will not be unloaded.
157 */
158 @Test
159 public void hiddenClassNestStrongHost() throws Exception {
160 TestLoader loader = new TestLoader();
161 Class<?> helper = Class.forName("LookupHelper", true, loader);
162 Method m = helper.getMethod("getLookup");
163 Lookup lookup = (Lookup)m.invoke(null);
164 HiddenClassUnloader[] unloaders = createNestOfTwoHiddenClasses(lookup, true, false);
165 assertFalse(unloaders[0].tryUnload()); // nest host cannot be unloaded
166 unloaders[1].unload();
167
168 // loader is strongly reachable
169 Reference.reachabilityFence(loader);
170 }
171
172 /*
173 * Create a HiddenClassUnloader that holds a weak reference to the newly created
174 * hidden class.
175 */
176 static HiddenClassUnloader createHiddenClass(Lookup lookup, boolean strong) throws Exception {
177 Class<?> hc;
178 if (strong) {
179 hc = lookup.defineHiddenClass(hiddenClassBytes, false, STRONG).lookupClass();
180 } else {
181 hc = lookup.defineHiddenClass(hiddenClassBytes, false).lookupClass();
182 }
183 assertTrue(hc.getClassLoader() == lookup.lookupClass().getClassLoader());
184 return new HiddenClassUnloader(hc);
185 }
186
187 /*
188 * Create an array of HiddenClassUnloader with two elements: the first element
189 * is for the nest host and the second element is for the nest member.
190 */
191 static HiddenClassUnloader[] createNestOfTwoHiddenClasses(Lookup lookup, boolean strongHost, boolean strongMember) throws Exception {
192 Lookup hostLookup;
193 if (strongHost) {
194 hostLookup = lookup.defineHiddenClass(hiddenClassBytes, false, STRONG);
195 } else {
196 hostLookup = lookup.defineHiddenClass(hiddenClassBytes, false);
197 }
198 Class<?> host = hostLookup.lookupClass();
199 Class<?> member;
200 if (strongMember) {
201 member = hostLookup.defineHiddenClass(hiddenClassBytes, false, NESTMATE, STRONG).lookupClass();
202 } else {
203 member = hostLookup.defineHiddenClass(hiddenClassBytes, false, NESTMATE).lookupClass();
204 }
205 assertTrue(member.getNestHost() == host);
206 return new HiddenClassUnloader[] { new HiddenClassUnloader(host), new HiddenClassUnloader(member) };
207 }
208
209 static class HiddenClassUnloader {
210 private final WeakReference<Class<?>> weakRef;
211 private HiddenClassUnloader(Class<?> hc) {
212 assertTrue(hc.isHidden());
213 this.weakRef = new WeakReference<>(hc);
214 }
215
216 void unload() {
217 // Force garbage collection to trigger unloading of class loader and native library
218 ForceGC gc = new ForceGC();
219 assertTrue(gc.await(() -> weakRef.get() == null));
220
221 if (weakRef.get() != null) {
222 throw new RuntimeException("loader " + " not unloaded!");
223 }
224 }
225
226 boolean tryUnload() {
227 ForceGC gc = new ForceGC();
228 return gc.await(() -> weakRef.get() == null);
229 }
230 }
231
232 static class TestLoader extends URLClassLoader {
233 static URL[] toURLs() {
234 try {
235 return new URL[] { CLASSES_DIR.toUri().toURL() };
236 } catch (MalformedURLException e) {
237 throw new Error(e);
238 }
239 }
240
241 static AtomicInteger counter = new AtomicInteger();
242 TestLoader() {
243 super("testloader-" + counter.addAndGet(1), toURLs(), ClassLoader.getSystemClassLoader());
244 }
245 }
246 }