1 /*
2 * Copyright (c) 2025, 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 8356870
27 * @summary Test HotSpotDiagnosticMXBean.dumpThreads with a thread owning a monitor for
28 * an object that is scalar replaced
29 * @requires vm.compMode != "Xcomp"
30 * @requires (vm.opt.TieredStopAtLevel == null | vm.opt.TieredStopAtLevel == 4)
31 * @modules jdk.management
32 * @library /test/lib
33 * @run main/othervm -XX:CompileCommand=inline,java/lang/String*.* DumpThreadsWithEliminatedLock plain platform
34 * @run main/othervm -XX:CompileCommand=inline,java/lang/String*.* DumpThreadsWithEliminatedLock plain virtual
35 * @run main/othervm -XX:CompileCommand=inline,java/lang/String*.* DumpThreadsWithEliminatedLock json platform
36 * @run main/othervm -XX:CompileCommand=inline,java/lang/String*.* DumpThreadsWithEliminatedLock json virtual
37 */
38
39 import java.io.IOException;
40 import java.io.UncheckedIOException;
41 import java.lang.management.ManagementFactory;
42 import java.nio.file.Files;
43 import java.nio.file.Path;
44 import java.time.Instant;
45 import java.util.List;
46 import java.util.concurrent.CountDownLatch;
47 import java.util.concurrent.ThreadFactory;
48 import java.util.concurrent.atomic.AtomicBoolean;
49 import java.util.concurrent.atomic.AtomicReference;
50 import java.util.stream.Stream;
51 import com.sun.management.HotSpotDiagnosticMXBean;
52 import jdk.test.lib.threaddump.ThreadDump;
53 import jdk.test.lib.thread.VThreadRunner;
54
55 public class DumpThreadsWithEliminatedLock {
56
57 public static void main(String[] args) throws Exception {
58 boolean plain = switch (args[0]) {
59 case "plain" -> true;
60 case "json" -> false;
61 default -> throw new RuntimeException("Unknown dump format");
62 };
63
64 ThreadFactory factory = switch (args[1]) {
65 case "platform" -> Thread.ofPlatform().factory();
66 case "virtual" -> Thread.ofVirtual().factory();
67 default -> throw new RuntimeException("Unknown thread kind");
68 };
69
70 // need at least two carriers for JTREG_TEST_THREAD_FACTORY=Virtual
71 if (Thread.currentThread().isVirtual()) {
72 VThreadRunner.ensureParallelism(2);
73 }
74
75 // A thread that spins creating and adding to a StringBuffer. StringBuffer is
76 // synchronized, assume object will be scalar replaced and the lock eliminated.
77 var started = new CountDownLatch(1);
78 var done = new AtomicBoolean();
79 var ref = new AtomicReference<String>();
80 Thread thread = factory.newThread(() -> {
81 started.countDown();
82 while (!done.get()) {
83 StringBuffer sb = new StringBuffer();
84 sb.append(System.currentTimeMillis());
85 String s = sb.toString();
86 ref.set(s);
87 }
88 });
89 try {
90 thread.start();
91 started.await();
92 if (plain) {
93 testPlainFormat();
94 } else {
95 testJsonFormat(thread.threadId());
96 }
97 } finally {
98 done.set(true);
99 thread.join();
100 }
101 }
102
103 /**
104 * Invoke HotSpotDiagnosticMXBean.dumpThreads to generate a thread dump in plain text
105 * format until "lock is eliminated" is found in the output.
106 */
107 private static void testPlainFormat() {
108 try {
109 Path file = genOutputPath(".txt");
110 boolean found = false;
111 int attempts = 0;
112 while (!found) {
113 attempts++;
114 Files.deleteIfExists(file);
115 ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class)
116 .dumpThreads(file.toString(), HotSpotDiagnosticMXBean.ThreadDumpFormat.TEXT_PLAIN);
117 try (Stream<String> stream = Files.lines(file)) {
118 found = stream.map(String::trim)
119 .anyMatch(l -> l.contains("- lock is eliminated"));
120 }
121 System.out.format("%s Attempt %d, found: %b%n", Instant.now(), attempts, found);
122 }
123 } catch (IOException ioe) {
124 throw new UncheckedIOException(ioe);
125 }
126 }
127
128 /**
129 * Invoke HotSpotDiagnosticMXBean.dumpThreads to generate a thread dump in JSON format
130 * until the monitorsOwned.locks array for the given thread has a null lock.
131 */
132 private static void testJsonFormat(long tid) {
133 try {
134 Path file = genOutputPath(".json");
135 boolean found = false;
136 int attempts = 0;
137 while (!found) {
138 attempts++;
139 Files.deleteIfExists(file);
140 ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class)
141 .dumpThreads(file.toString(), HotSpotDiagnosticMXBean.ThreadDumpFormat.JSON);
142
143 // parse thread dump as JSON and find thread
144 String jsonText = Files.readString(file);
145 ThreadDump threadDump = ThreadDump.parse(jsonText);
146 ThreadDump.ThreadInfo ti = threadDump.rootThreadContainer()
147 .findThread(tid)
148 .orElse(null);
149 if (ti == null) {
150 throw new RuntimeException("Thread " + tid + " not found in thread dump");
151 }
152
153 // look for null element in ownedMonitors/locks array
154 found = ti.ownedMonitors()
155 .values()
156 .stream()
157 .flatMap(List::stream)
158 .anyMatch(o -> o == null);
159 System.out.format("%s Attempt %d, found: %b%n", Instant.now(), attempts, found);
160 }
161 } catch (IOException ioe) {
162 throw new UncheckedIOException(ioe);
163 }
164 }
165
166 /**
167 * Generate a file path with the given suffix to use as an output file.
168 */
169 private static Path genOutputPath(String suffix) throws IOException {
170 Path dir = Path.of(".").toAbsolutePath();
171 Path file = Files.createTempFile(dir, "dump", suffix);
172 Files.delete(file);
173 return file;
174 }
175 }