RuntimeThreadInheritanceLeak.java revision 9330:8b1f1c2a400f 
1/*
2 * Copyright (c) 2001, 2012, 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/* @test
25 * @bug 4404702
26 * @summary When the RMI runtime (lazily) spawns system threads that could
27 * outlive the application context in which they were (happened to be)
28 * created, such threads should not inherit (thread local) data specific to
29 * such an application context for various isolation reasons (see 4219095).
30 * While there is not yet a practical means for a general solution to this
31 * problem, the particular problem documented in 4404702-- the inheritance
32 * of the parent thread's context class loader, preventing that loader from
33 * being garbage collected in the future-- can be easily fixed.  This test
34 * verifies that the context class loader in effect when the first remote
35 * object is exported (and thus when some long-lived RMI daemon threads are
36 * created) can be garbage collected after the remote object has been
37 * unexported.  [Note that this test is somewhat at the mercy of other J2SE
38 * subsystems also not holding on to the loader in their daemon threads.]
39 * @author Peter Jones
40 *
41 * @build RuntimeThreadInheritanceLeak_Stub
42 * @run main/othervm RuntimeThreadInheritanceLeak
43 */
44
45import java.lang.ref.Reference;
46import java.lang.ref.ReferenceQueue;
47import java.lang.ref.WeakReference;
48import java.net.URL;
49import java.net.URLClassLoader;
50import java.rmi.Remote;
51import java.rmi.RemoteException;
52import java.rmi.server.UnicastRemoteObject;
53import java.util.Iterator;
54import java.util.Map;
55
56public class RuntimeThreadInheritanceLeak implements Remote {
57
58    private static final int TIMEOUT = 20000;
59
60    public static void main(String[] args) {
61
62        System.err.println("\nRegression test for bug 4404702\n");
63
64        /*
65         * HACK: Work around the fact that java.util.logging.LogManager's
66         * (singleton) construction also has this bug-- it will register a
67         * "shutdown hook", i.e. a thread, which will inherit and pin the
68         * current thread's context class loader for the lifetime of the VM--
69         * by causing the LogManager to be initialized now, instead of by
70         * RMI when our special context class loader is set.
71         */
72        java.util.logging.LogManager.getLogManager();
73
74        /*
75         * HACK: Work around the fact that the non-native, thread-based
76         * SecureRandom seed generator (ThreadedSeedGenerator) seems to
77         * have this bug too (which had been causing this test to fail
78         * when run with jtreg on Windows XP-- see 4910382).
79         */
80        (new java.security.SecureRandom()).nextInt();
81
82        RuntimeThreadInheritanceLeak obj = new RuntimeThreadInheritanceLeak();
83
84        try {
85            ClassLoader loader = URLClassLoader.newInstance(new URL[0]);
86            ReferenceQueue refQueue = new ReferenceQueue();
87            Reference loaderRef = new WeakReference(loader, refQueue);
88            System.err.println("created loader: " + loader);
89
90            Thread.currentThread().setContextClassLoader(loader);
91            UnicastRemoteObject.exportObject(obj);
92            Thread.currentThread().setContextClassLoader(
93                ClassLoader.getSystemClassLoader());
94            System.err.println(
95                "exported remote object with loader as context class loader");
96
97            loader = null;
98            System.err.println("nulled strong reference to loader");
99
100            UnicastRemoteObject.unexportObject(obj, true);
101            System.err.println("unexported remote object");
102
103            /*
104             * HACK: Work around the fact that the sun.misc.GC daemon thread
105             * also has this bug-- it will have inherited our loader as its
106             * context class loader-- by giving it a chance to pass away.
107             */
108            Thread.sleep(2000);
109            System.gc();
110
111            System.err.println(
112                "waiting to be notified of loader being weakly reachable...");
113            Reference dequeued = refQueue.remove(TIMEOUT);
114            if (dequeued == null) {
115                System.err.println(
116                    "TEST FAILED: loader not deteced weakly reachable");
117                dumpThreads();
118                throw new RuntimeException(
119                    "TEST FAILED: loader not detected weakly reachable");
120            }
121
122            System.err.println(
123                "TEST PASSED: loader detected weakly reachable");
124            dumpThreads();
125
126        } catch (RuntimeException e) {
127            throw e;
128        } catch (Exception e) {
129            throw new RuntimeException("TEST FAILED: unexpected exception", e);
130        } finally {
131            try {
132                UnicastRemoteObject.unexportObject(obj, true);
133            } catch (RemoteException e) {
134            }
135        }
136    }
137
138    /**
139     * Dumps information about all live threads to System.err,
140     * including their context class loaders.
141     **/
142    private static void dumpThreads() {
143        System.err.println(
144            "current live threads and their context class loaders:");
145        Map threads = Thread.getAllStackTraces();
146        for (Iterator iter = threads.entrySet().iterator(); iter.hasNext();) {
147            Map.Entry e = (Map.Entry) iter.next();
148            Thread t = (Thread) e.getKey();
149            System.err.println("  thread: " + t);
150            System.err.println("  context class loader: " +
151                               t.getContextClassLoader());
152            StackTraceElement[] trace = (StackTraceElement[]) e.getValue();
153            for (int i = 0; i < trace.length; i++) {
154                System.err.println("    " + trace[i]);
155            }
156        }
157    }
158}
159