util/WeakHashMap/GCDuringIteration.java

/*
 * Copyright (c) 2007, 2015, 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
 * @bug 6499848
 * @library /lib/testlibrary/
 * @build jdk.testlibrary.RandomFactory
 * @run main GCDuringIteration
 * @summary Check that iterators work properly in the presence of
 *          concurrent finalization and removal of elements.
 * @key randomness
 */

import static java.util.concurrent.TimeUnit.SECONDS;

import java.lang.ref.WeakReference;
import java.util.Arrays;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Random;
import java.util.WeakHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.function.BooleanSupplier;
import jdk.testlibrary.RandomFactory;

public class GCDuringIteration {

    /** No guarantees, but effective in practice. */
    static void forceFullGc() {
        CountDownLatch finalizeDone = new CountDownLatch(1);
        WeakReference<?> ref = new WeakReference<Object>(new Object() {
            protected void finalize() { finalizeDone.countDown(); }});
        try {
            for (int i = 0; i < 10; i++) {
                System.gc();
                if (finalizeDone.await(1L, SECONDS) && ref.get() == null) {
                    System.runFinalization(); // try to pick up stragglers
                    return;
                }
            }
        } catch (InterruptedException unexpected) {
            throw new AssertionError("unexpected InterruptedException");
        }
        throw new AssertionError("failed to do a \"full\" gc");
    }

    static void gcAwait(BooleanSupplier s) {
        for (int i = 0; i < 10; i++) {
            if (s.getAsBoolean())
                return;
            forceFullGc();
        }
        throw new AssertionError("failed to satisfy condition");
    }

    // A class with the traditional pessimal hashCode implementation,
    // to ensure that all instances end up in the same bucket.
    static class Foo { public int hashCode() { return 42; }}

    <K,V> void put(Map<K,V> map, K k, V v) {
        check(! map.containsKey(k));
        equal(map.get(k), null);
        equal(map.put(k, v), null);
        equal(map.get(k), v);
        check(map.containsKey(k));
        equal(map.put(k, v), v);
        equal(map.get(k), v);
        check(map.containsKey(k));
        check(! map.isEmpty());
        equal(map.keySet().iterator().next(), k);
        equal(map.values().iterator().next(), v);
    }

    static final Random rnd = RandomFactory.getRandom();

    void checkIterator(final Iterator<Map.Entry<Foo, Integer>> it, int first) {
        for (int i = first; i >= 0; --i) {
            if (rnd.nextBoolean()) check(it.hasNext());
            equal(it.next().getValue(), i);
        }
        if (rnd.nextBoolean()) {
            try {
                it.next();
                throw new AssertionError("should throw");
            } catch (NoSuchElementException success) {}
        }

        if (rnd.nextBoolean())
            check(! it.hasNext());
    }

    <K,V> V firstValue(Map<K,V> map) {
        return map.values().iterator().next();
    }

    void test(String[] args) throws Throwable {
        final int n = 10;
        // Create array of strong refs
        final Foo[] foos = new Foo[2*n];
        final Map<Foo,Integer> map = new WeakHashMap<>(foos.length);
        check(map.isEmpty());
        equal(map.size(), 0);

        for (int i = 0; i < foos.length; i++) {
            Foo foo = new Foo();
            foos[i] = foo;
            put(map, foo, i);
        }
        equal(map.size(), foos.length);

        {
            int first = firstValue(map);
            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
            foos[first] = null;
            gcAwait(() -> map.size() == first);
            checkIterator(it, first-1);
            equal(map.size(), first);
            equal(firstValue(map), first-1);
        }

        {
            int first = firstValue(map);
            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
            it.next();          // protects first entry
            System.out.println(map.values());
            int oldSize = map.size();
            foos[first] = null;
            forceFullGc();
            equal(map.size(), oldSize);
            System.out.println(map.values());
            checkIterator(it, first-1);
            // first entry no longer protected
            gcAwait(() -> map.size() == first);
            equal(firstValue(map), first-1);
        }

        {
            int first = firstValue(map);
            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
            it.next();          // protects first entry
            System.out.println(map.values());
            foos[first] = foos[first-1] = null;
            gcAwait(() -> map.size() == first);
            equal(firstValue(map), first);
            System.out.println(map.values());
            checkIterator(it, first-2);
            // first entry no longer protected
            gcAwait(() -> map.size() == first-1);
            equal(firstValue(map), first-2);
        }

        {
            int first = firstValue(map);
            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
            it.next();          // protects first entry
            it.hasNext();       // protects second entry
            System.out.println(map.values());
            int oldSize = map.size();
            foos[first] = foos[first-1] = null;
            forceFullGc();
            equal(map.size(), oldSize);
            equal(firstValue(map), first);
            System.out.println(map.values());
            checkIterator(it, first-1);
            // first entry no longer protected
            gcAwait(() -> map.size() == first-1);
            equal(firstValue(map), first-2);
        }

        {
            int first = firstValue(map);
            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
            it.next();          // protects first entry
            System.out.println(map.values());
            equal(map.size(), first+1);
            foos[first] = foos[first-1] = null;
            gcAwait(() -> map.size() == first);
            it.remove();
            equal(firstValue(map), first-2);
            equal(map.size(), first-1);
            System.out.println(map.values());
            checkIterator(it, first-2);
            // first entry no longer protected
            gcAwait(() -> map.size() == first-1);
            equal(firstValue(map), first-2);
        }

        {
            int first = firstValue(map);
            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
            it.next();          // protects first entry
            it.remove();
            it.hasNext();       // protects second entry
            System.out.println(map.values());
            equal(map.size(), first);
            foos[first] = foos[first-1] = null;
            forceFullGc();
            equal(firstValue(map), first-1);
            equal(map.size(), first);
            System.out.println(map.values());
            checkIterator(it, first-1);
            gcAwait(() -> map.size() == first-1);
            equal(firstValue(map), first-2);
        }

        {
            int first = firstValue(map);
            final Iterator<Map.Entry<Foo,Integer>> it = map.entrySet().iterator();
            it.hasNext();       // protects first entry
            Arrays.fill(foos, null);
            gcAwait(() -> map.size() == 1);
            System.out.println(map.values());
            equal(it.next().getValue(), first);
            check(! it.hasNext());
            gcAwait(() -> map.size() == 0);
            check(map.isEmpty());
        }
    }

    //--------------------- Infrastructure ---------------------------
    volatile int passed = 0, failed = 0;
    void pass() {passed++;}
    void fail() {failed++; Thread.dumpStack();}
    void fail(String msg) {System.err.println(msg); fail();}
    void unexpected(Throwable t) {failed++; t.printStackTrace();}
    void check(boolean cond) {if (cond) pass(); else fail();}
    void equal(Object x, Object y) {
        if (x == null ? y == null : x.equals(y)) pass();
        else fail(x + " not equal to " + y);}
    public static void main(String[] args) throws Throwable {
        new GCDuringIteration().instanceMain(args);}
    void instanceMain(String[] args) throws Throwable {
        try {test(args);} catch (Throwable t) {unexpected(t);}
        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);
        if (failed > 0) throw new AssertionError("Some tests failed");}
}
Revision:	1.8
Committed:	Thu Feb 18 04:47:12 2016 UTC (8 years, 3 months ago) by jsr166
Branch:	MAIN
Changes since 1.7:	+63 -54 lines
Log Message:	use more robust techniques for waiting for gc finalization
#	User	Rev	Content
1	jsr166	1.1	/*
2	jsr166	1.7	* Copyright (c) 2007, 2015, Oracle and/or its affiliates. All rights reserved.
3	jsr166	1.1	* 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	jsr166	1.2	* 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	jsr166	1.1	*/
23
24			/*
25			* @test
26			* @bug 6499848
27	jsr166	1.7	* @library /lib/testlibrary/
28			* @build jdk.testlibrary.RandomFactory
29			* @run main GCDuringIteration
30	jsr166	1.1	* @summary Check that iterators work properly in the presence of
31			* concurrent finalization and removal of elements.
32	jsr166	1.8	* @key randomness
33	jsr166	1.1	*/
34
35	jsr166	1.8	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	jsr166	1.1	import java.util.concurrent.CountDownLatch;
45	jsr166	1.8	import java.util.function.BooleanSupplier;
46	jsr166	1.7	import jdk.testlibrary.RandomFactory;
47	jsr166	1.1
48			public class GCDuringIteration {
49	jsr166	1.4
50	jsr166	1.8	/** 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	jsr166	1.1	}
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	jsr166	1.7	static final Random rnd = RandomFactory.getRandom();
97
98	jsr166	1.1	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	jsr166	1.8	if (rnd.nextBoolean()) {
104			try {
105			it.next();
106			throw new AssertionError("should throw");
107			} catch (NoSuchElementException success) {}
108			}
109
110	jsr166	1.1	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	jsr166	1.7	final Map<Foo,Integer> map = new WeakHashMap<>(foos.length);
123	jsr166	1.1	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	jsr166	1.4	foos[first] = null;
137	jsr166	1.8	gcAwait(() -> map.size() == first);
138	jsr166	1.1	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	jsr166	1.8	int oldSize = map.size();
149	jsr166	1.4	foos[first] = null;
150	jsr166	1.8	forceFullGc();
151			equal(map.size(), oldSize);
152	jsr166	1.1	System.out.println(map.values());
153			checkIterator(it, first-1);
154	jsr166	1.4	// first entry no longer protected
155	jsr166	1.8	gcAwait(() -> map.size() == first);
156	jsr166	1.1	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	jsr166	1.4	foos[first] = foos[first-1] = null;
165	jsr166	1.8	gcAwait(() -> map.size() == first);
166	jsr166	1.1	equal(firstValue(map), first);
167			System.out.println(map.values());
168			checkIterator(it, first-2);
169	jsr166	1.4	// first entry no longer protected
170	jsr166	1.8	gcAwait(() -> map.size() == first-1);
171	jsr166	1.1	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	jsr166	1.8	int oldSize = map.size();
181	jsr166	1.4	foos[first] = foos[first-1] = null;
182	jsr166	1.8	forceFullGc();
183			equal(map.size(), oldSize);
184	jsr166	1.1	equal(firstValue(map), first);
185			System.out.println(map.values());
186			checkIterator(it, first-1);
187	jsr166	1.4	// first entry no longer protected
188	jsr166	1.8	gcAwait(() -> map.size() == first-1);
189	jsr166	1.1	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	jsr166	1.8	equal(map.size(), first+1);
198	jsr166	1.4	foos[first] = foos[first-1] = null;
199	jsr166	1.8	gcAwait(() -> map.size() == first);
200	jsr166	1.1	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	jsr166	1.4	// first entry no longer protected
206	jsr166	1.8	gcAwait(() -> map.size() == first-1);
207	jsr166	1.1	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	jsr166	1.8	equal(map.size(), first);
218	jsr166	1.4	foos[first] = foos[first-1] = null;
219	jsr166	1.8	forceFullGc();
220	jsr166	1.1	equal(firstValue(map), first-1);
221			equal(map.size(), first);
222			System.out.println(map.values());
223			checkIterator(it, first-1);
224	jsr166	1.8	gcAwait(() -> map.size() == first-1);
225	jsr166	1.1	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	jsr166	1.8	gcAwait(() -> map.size() == 1);
234	jsr166	1.1	System.out.println(map.values());
235			equal(it.next().getValue(), first);
236			check(! it.hasNext());
237	jsr166	1.8	gcAwait(() -> map.size() == 0);
238	jsr166	1.1	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			}