1 /*
2 * Copyright (c) 2022, 2023, 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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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22 */
23
24 /**
25 * @test
26 * @summary Test Thread.holdsLock when lock held by carrier thread
27 * @requires vm.continuations
28 * @modules java.base/java.lang:+open
29 * @enablePreview
30 * @run junit HoldsLock
31 */
32
33 /**
34 * @test
35 * @summary Test Thread.holdsLock when lock held by carrier thread
36 * @requires vm.continuations & vm.debug
37 * @modules java.base/java.lang:+open
38 * @enablePreview
39 * @run junit/othervm -XX:+UseHeavyMonitors HoldsLock
40 */
41
42 import java.lang.management.LockInfo;
43 import java.lang.management.ManagementFactory;
44 import java.lang.management.ThreadInfo;
45 import java.lang.management.ThreadMXBean;
46 import java.util.Arrays;
47 import java.util.concurrent.ArrayBlockingQueue;
48 import java.util.concurrent.BlockingQueue;
49 import java.util.concurrent.ExecutionException;
50 import java.util.concurrent.Executor;
51 import java.util.concurrent.RejectedExecutionException;
52 import java.util.concurrent.ThreadFactory;
53 import java.util.concurrent.atomic.AtomicReference;
54
55 import org.junit.jupiter.api.Test;
56 import org.junit.jupiter.api.Disabled;
57 import static org.junit.jupiter.api.Assertions.*;
58
59 class HoldsLock {
60 static final Object LOCK1 = new Object();
61 static final Object LOCK2 = new Object();
62
63 @Disabled("JDK-8281642")
64 @Test
65 void testHoldsLock() throws Exception {
66 var q = new ArrayBlockingQueue<Runnable>(5);
67
68 Thread carrier = Thread.ofPlatform().start(() -> {
69 synchronized (LOCK1) {
70 eventLoop(q);
71 }
72 });
73
74 var ex = new AtomicReference<Throwable>();
75 Thread vthread = spawnVirtual(ex, executor(q), () -> {
76 assertTrue(Thread.currentThread().isVirtual());
77 assertFalse(carrier.isVirtual());
78
79 synchronized (LOCK2) {
80 assertTrue(Thread.holdsLock(LOCK2)); // virtual thread holds lock2
81 assertFalse(Thread.holdsLock(LOCK1)); // carrier thread holds lock1
82 }
83 });
84
85 join(vthread, ex);
86 stop(carrier);
87 }
88
89 @Test
90 void testThreadInfo() throws Exception {
91 var q = new ArrayBlockingQueue<Runnable>(5);
92
93 Thread carrier = spawnCarrier(q);
94 Thread vthread = spawnVirtual(executor(q), () -> {
95 synchronized (LOCK1) {
96 try {
97 LOCK1.wait();
98 } catch (InterruptedException e) {}
99 }
100 });
101
102 while (vthread.getState() != Thread.State.WAITING) {
103 Thread.sleep(10);
104 }
105 System.out.format("%s is waiting on %s%n", vthread, LOCK1);
106 long vthreadId = vthread.getId();
107 long carrierId = carrier.getId();
108
109 System.out.format("\t\t%s%n", LOCK1);
110 String lockAsString = LOCK1.toString();
111
112 ThreadMXBean bean = ManagementFactory.getThreadMXBean();
113 long[] tids = bean.getAllThreadIds();
114 boolean foundCarrier = false;
115 for (long tid : tids) {
116 ThreadInfo info = bean.getThreadInfo(tid);
117 System.out.println(info); // System.out.format("%d\t%s%n", tid, info.getThreadName());
118
119 LockInfo lock = info.getLockInfo();
120 if (lock != null && lockAsString.equals(lock.toString())) {
121 assert false; // should never get here
122 assert tid == vthreadId : "Actual waiter is: " + info.getThreadName()
123 + " vthread: " + vthread + " carrier: " + carrier;
124 }
125
126 if (tid == carrierId) {
127 // Carrier is WAITING on vthread
128 assertTrue(info.getThreadState() == Thread.State.WAITING);
129 assertEquals(vthread.getClass().getName(), info.getLockInfo().getClassName());
130 assertTrue(info.getLockInfo().getIdentityHashCode() == System.identityHashCode(vthread));
131 assertTrue(info.getLockOwnerId() == vthreadId);
132 foundCarrier = true;
133 }
134 }
135 assertTrue(foundCarrier);
136
137 stop(vthread);
138 stop(carrier);
139 }
140
141 static Thread spawnCarrier(BlockingQueue<Runnable> q) {
142 return Thread.ofPlatform().start(() -> { eventLoop(q); });
143 }
144
145 static Executor executor(BlockingQueue<Runnable> q) {
146 return r -> {
147 if (!q.offer(r)) throw new RejectedExecutionException();
148 };
149 }
150
151 static void eventLoop(BlockingQueue<Runnable> q) {
152 try {
153 while (!Thread.interrupted())
154 q.take().run();
155 } catch (InterruptedException e) {}
156 }
157
158 static Thread spawnVirtual(Executor scheduler, Runnable task) {
159 var t = newThread(scheduler, task);
160 t.start();
161 return t;
162 }
163
164 static Thread spawnVirtual(AtomicReference<Throwable> ex, Executor scheduler, Runnable task) {
165 var t = newThread(scheduler, () -> {
166 try {
167 task.run();
168 } catch (Throwable x) {
169 ex.set(x);
170 }
171 });
172 t.start();
173 return t;
174 }
175
176 static void stop(Thread t) throws InterruptedException {
177 t.interrupt();
178 t.join();
179 }
180
181 static void join(Thread t, AtomicReference<Throwable> ex) throws Exception {
182 t.join();
183 var ex0 = ex.get();
184 if (ex0 != null)
185 throw new ExecutionException("Thread " + t + " threw an uncaught exception.", ex0);
186 }
187
188 static Thread newThread(Executor scheduler, Runnable task) {
189 ThreadFactory factory = ThreadBuilders.virtualThreadBuilder(scheduler).factory();
190 return factory.newThread(task);
191 }
192 }