1 /*
 2  * Copyright (c) 2024, 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  * @summary Stress test Thread.getStackTrace on a virtual thread in timed-Object.wait
27  * @requires vm.debug != true
28  * @run main/othervm GetStackTraceALotWithTimedWait 100000
29  */
30 
31 /*
32  * @test
33  * @requires vm.debug == true
34  * @run main/othervm GetStackTraceALotWithTimedWait 50000
35  */
36 
37 import java.time.Instant;
38 import java.util.ArrayList;
39 import java.util.concurrent.Executors;
40 import java.util.concurrent.ThreadLocalRandom;
41 import java.util.concurrent.atomic.AtomicBoolean;
42 import java.util.concurrent.atomic.AtomicReference;
43 
44 public class GetStackTraceALotWithTimedWait {
45 
46     public static void main(String[] args) throws Exception {
47         int iterations = args.length > 0 ? Integer.parseInt(args[0]) : 100_000;
48 
49         try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
50             var done = new AtomicBoolean();
51             var threads = new ArrayList<Thread>();
52 
53             // start threads that invoke Object.wait with a short timeout
54             int nthreads = Runtime.getRuntime().availableProcessors();
55             for (int i = 0; i < nthreads; i++) {
56                 var ref = new AtomicReference<Thread>();
57                 var lock = new Object();
58                 executor.submit(() -> {
59                     ref.set(Thread.currentThread());
60                     while (!done.get()) {
61                         synchronized (lock) {
62                             int delay = 1 + ThreadLocalRandom.current().nextInt(20);
63                             lock.wait(delay);
64                         }
65                     }
66                     return null;
67                 });
68                 Thread thread;
69                 while ((thread = ref.get()) == null) {
70                     Thread.sleep(20);
71                 }
72                 threads.add(thread);
73             }
74 
75             // hammer on Thread.getStackTrace
76             try {
77                 for (int i = 1; i <= iterations; i++) {
78                     if ((i % 1000) == 0) {
79                         System.out.println(Instant.now() + " => " + i + " of " + iterations);
80                     }
81                     for (Thread thread : threads) {
82                         thread.getStackTrace();
83                     }
84                 }
85             } finally {
86                 done.set(true);
87             }
88         }
89     }
90 }
91