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