1 /*
2 * Copyright (c) 2007, 2017, 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 * @bug 6499848
27 * @library /test/lib
28 * @build jdk.test.lib.RandomFactory
29 * @run main GCDuringIteration
30 * @summary Check that iterators work properly in the presence of
31 * concurrent finalization and removal of elements.
32 * @key randomness
33 */
34
35 import static java.util.concurrent.TimeUnit.SECONDS;
36
37 import java.lang.ref.WeakReference;
38 import java.util.Arrays;
39 import java.util.Iterator;
40 import java.util.Map;
41 import java.util.NoSuchElementException;
42 import java.util.Random;
43 import java.util.WeakHashMap;
44 import java.util.concurrent.CountDownLatch;
45 import java.util.function.BooleanSupplier;
46 import jdk.test.lib.RandomFactory;
47
48 public class GCDuringIteration {
49
50 /** No guarantees, but effective in practice. */
51 static void forceFullGc() {
52 CountDownLatch finalizeDone = new CountDownLatch(1);
53 WeakReference<?> ref = new WeakReference<Object>(new Object() {
54 protected void finalize() { finalizeDone.countDown(); }});
55 try {
56 for (int i = 0; i < 10; i++) {
57 System.gc();
58 if (finalizeDone.await(1L, SECONDS) && ref.get() == null) {
59 System.runFinalization(); // try to pick up stragglers
60 return;
61 }
62 }
63 } catch (InterruptedException unexpected) {
64 throw new AssertionError("unexpected InterruptedException");
65 }
66 throw new AssertionError("failed to do a \"full\" gc");
67 }
68
69 static void gcAwait(BooleanSupplier s) {
70 for (int i = 0; i < 10; i++) {
71 if (s.getAsBoolean())
72 return;
73 forceFullGc();
74 }
75 throw new AssertionError("failed to satisfy condition");
76 }
77
78 // A class with the traditional pessimal hashCode implementation,
79 // to ensure that all instances end up in the same bucket.
80 static class Foo { public int hashCode() { return 42; }}
81
82 <K,V> void put(Map<K,V> map, K k, V v) {
83 check(! map.containsKey(k));
84 equal(map.get(k), null);
85 equal(map.put(k, v), null);
86 equal(map.get(k), v);
87 check(map.containsKey(k));
88 equal(map.put(k, v), v);
89 equal(map.get(k), v);
90 check(map.containsKey(k));
91 check(! map.isEmpty());
92 equal(map.keySet().iterator().next(), k);
93 equal(map.values().iterator().next(), v);
94 }
95
96 static final Random rnd = RandomFactory.getRandom();
97
98 void checkIterator(final Iterator<Map.Entry<Foo, Integer>> it, int first) {
99 for (int i = first; i >= 0; --i) {
100 if (rnd.nextBoolean()) check(it.hasNext());
101 equal(it.next().getValue(), i);
102 }
103 if (rnd.nextBoolean()) {
104 try {
105 it.next();
106 throw new AssertionError("should throw");
107 } catch (NoSuchElementException success) {}
108 }
109
110 if (rnd.nextBoolean())
111 check(! it.hasNext());
112 }
113
114 <K,V> V firstValue(Map<K,V> map) {
115 return map.values().iterator().next();
116 }
117
118 void test(String[] args) throws Throwable {
119 final int n = 10;
120 // Create array of strong refs
121 final Foo[] foos = new Foo[2*n];
122 final Map<Foo,Integer> map = new WeakHashMap<>(foos.length);
123 check(map.isEmpty());
124 equal(map.size(), 0);
125
126 for (int i = 0; i < foos.length; i++) {
127 Foo foo = new Foo();
128 foos[i] = foo;
129 put(map, foo, i);
130 }
131 equal(map.size(), foos.length);
132
133 {
134 int first = firstValue(map);
135 final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
136 foos[first] = null;
137 gcAwait(() -> map.size() == first);
138 checkIterator(it, first-1);
139 equal(map.size(), first);
140 equal(firstValue(map), first-1);
141 }
142
143 {
144 int first = firstValue(map);
145 final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
146 it.next(); // protects first entry
147 System.out.println(map.values());
148 int oldSize = map.size();
149 foos[first] = null;
150 forceFullGc();
151 equal(map.size(), oldSize);
152 System.out.println(map.values());
153 checkIterator(it, first-1);
154 // first entry no longer protected
155 gcAwait(() -> map.size() == first);
156 equal(firstValue(map), first-1);
157 }
158
159 {
160 int first = firstValue(map);
161 final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
162 it.next(); // protects first entry
163 System.out.println(map.values());
164 foos[first] = foos[first-1] = null;
165 gcAwait(() -> map.size() == first);
166 equal(firstValue(map), first);
167 System.out.println(map.values());
168 checkIterator(it, first-2);
169 // first entry no longer protected
170 gcAwait(() -> map.size() == first-1);
171 equal(firstValue(map), first-2);
172 }
173
174 {
175 int first = firstValue(map);
176 final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
177 it.next(); // protects first entry
178 it.hasNext(); // protects second entry
179 System.out.println(map.values());
180 int oldSize = map.size();
181 foos[first] = foos[first-1] = null;
182 forceFullGc();
183 equal(map.size(), oldSize);
184 equal(firstValue(map), first);
185 System.out.println(map.values());
186 checkIterator(it, first-1);
187 // first entry no longer protected
188 gcAwait(() -> map.size() == first-1);
189 equal(firstValue(map), first-2);
190 }
191
192 {
193 int first = firstValue(map);
194 final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
195 it.next(); // protects first entry
196 System.out.println(map.values());
197 equal(map.size(), first+1);
198 foos[first] = foos[first-1] = null;
199 gcAwait(() -> map.size() == first);
200 it.remove();
201 equal(firstValue(map), first-2);
202 equal(map.size(), first-1);
203 System.out.println(map.values());
204 checkIterator(it, first-2);
205 // first entry no longer protected
206 gcAwait(() -> map.size() == first-1);
207 equal(firstValue(map), first-2);
208 }
209
210 {
211 int first = firstValue(map);
212 final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
213 it.next(); // protects first entry
214 it.remove();
215 it.hasNext(); // protects second entry
216 System.out.println(map.values());
217 equal(map.size(), first);
218 foos[first] = foos[first-1] = null;
219 forceFullGc();
220 equal(firstValue(map), first-1);
221 equal(map.size(), first);
222 System.out.println(map.values());
223 checkIterator(it, first-1);
224 gcAwait(() -> map.size() == first-1);
225 equal(firstValue(map), first-2);
226 }
227
228 {
229 int first = firstValue(map);
230 final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
231 it.hasNext(); // protects first entry
232 Arrays.fill(foos, null);
233 gcAwait(() -> map.size() == 1);
234 System.out.println(map.values());
235 equal(it.next().getValue(), first);
236 check(! it.hasNext());
237 gcAwait(() -> map.size() == 0);
238 check(map.isEmpty());
239 }
240 }
241
242 //--------------------- Infrastructure ---------------------------
243 volatile int passed = 0, failed = 0;
244 void pass() {passed++;}
245 void fail() {failed++; Thread.dumpStack();}
246 void fail(String msg) {System.err.println(msg); fail();}
247 void unexpected(Throwable t) {failed++; t.printStackTrace();}
248 void check(boolean cond) {if (cond) pass(); else fail();}
249 void equal(Object x, Object y) {
250 if (x == null ? y == null : x.equals(y)) pass();
251 else fail(x + " not equal to " + y);}
252 public static void main(String[] args) throws Throwable {
253 new GCDuringIteration().instanceMain(args);}
254 void instanceMain(String[] args) throws Throwable {
255 try {test(args);} catch (Throwable t) {unexpected(t);}
256 System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
257 if (failed > 0) throw new AssertionError("Some tests failed");}
258 }