1 /*
 2  * Copyright (c) 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.
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 virtual threads that are blocking or
27  *     blocked on monitorenter
28  * @run main GetStackTraceALotWhenBlocked 500000
29  */
30 
31 /*
32  * @test
33  * @requires vm.debug == true & vm.continuations
34  * @run main/timeout=300 GetStackTraceALotWhenBlocked 50000
35  */
36 
37 import java.util.concurrent.ThreadLocalRandom;
38 import java.util.concurrent.atomic.AtomicBoolean;
39 
40 public class GetStackTraceALotWhenBlocked {
41 
42     public static void main(String[] args) throws Exception {
43         int iterations = args.length > 0 ? Integer.parseInt(args[0]) : 100_000;
44 
45         var done = new AtomicBoolean();
46         var lock = new Object();
47 
48         Runnable task = () -> {
49             long count = 0L;
50             while (!done.get()) {
51                 synchronized (lock) {
52                     pause();
53                 }
54                 count++;
55             }
56             System.out.format("%s => %d%n", Thread.currentThread(), count);
57         };
58 
59         var thread1 = Thread.ofVirtual().start(task);
60         var thread2 = Thread.ofVirtual().start(task);
61         try {
62             for (int i = 0; i < iterations; i++) {
63                 thread1.getStackTrace();
64                 pause();
65                 thread2.getStackTrace();
66                 pause();
67             }
68         } finally {
69             done.set(true);
70             thread1.join();
71             thread2.join();
72         }
73     }
74 
75     private static void pause() {
76         if (ThreadLocalRandom.current().nextBoolean()) {
77             Thread.onSpinWait();
78         } else {
79             Thread.yield();
80         }
81     }
82 }