1 /*
 2  * Copyright (C) 2021 THL A29 Limited, a Tencent company. 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 Test virtual thread park when scheduler is a fixed thread pool
27  * @requires vm.continuations
28  * @modules java.base/java.lang:+open
29  * @run main ParkWithFixedThreadPool
30  */
31 
32 import java.util.concurrent.*;
33 import java.util.concurrent.atomic.*;
34 import java.util.concurrent.locks.LockSupport;
35 
36 public class ParkWithFixedThreadPool {
37     public static void main(String[] args) throws Exception {
38         try (ExecutorService scheduler = Executors.newFixedThreadPool(8)) {
39             int vthreadCount = 300;
40             Thread[] vthreads = new Thread[vthreadCount];
41             Runnable target = new Runnable() {
42                 public void run() {
43                     int myIndex = -1;
44                     for (int i = 0; i < vthreadCount; i++) {
45                         if (vthreads[i] == Thread.currentThread()) {
46                             myIndex = i;
47                             break;
48                         }
49                     }
50 
51                     if (myIndex > 0) {
52                         LockSupport.unpark(vthreads[myIndex - 1]);
53                     }
54 
55                     if (myIndex != (vthreadCount - 1)) {
56                         LockSupport.park();
57                     }
58                 }
59             };
60 
61             ThreadFactory factory = ThreadBuilders.virtualThreadBuilder(scheduler)
62                     .name("vthread-", 0)
63                     .factory();
64 
65             for (int i = 0; i < vthreadCount; i++) {
66                 vthreads[i] = factory.newThread(target);
67             }
68             for (int i = 0; i < vthreadCount; i++) {
69                 vthreads[i].start();
70             }
71 
72             for (int i = 0; i < vthreadCount; i++) {
73                 vthreads[i].join();
74             }
75         }
76     }
77 }