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 Test cancelling a timeout task for Object.wait(millis) when there is
27 * contention on the timer queue
28 * @key randomness
29 * @run main/othervm
30 * -Djdk.virtualThreadScheduler.parallelism=2
31 * -Djdk.virtualThreadScheduler.timerQueues=1
32 * CancelTimerWithContention
33 */
34
35 import java.time.Instant;
36 import java.util.Random;
37 import java.util.concurrent.Executors;
38 import java.util.concurrent.atomic.AtomicInteger;
39
40 public class CancelTimerWithContention {
41
42 // number of threads
43 private static final int MIN_THREADS = 100;
44 private static final int MAX_THREADS = 10_000;
45
46 // number of monitors to enter
47 private static final int MIN_MONITORS = 2;
48 private static final int MAX_MONITORS = 8;
49
50 private static final Random RAND = new Random();
51
52 public static void main(String[] args) {
53 for (int threadCount = MIN_THREADS; threadCount <= MAX_THREADS; threadCount += 100) {
54 System.out.format("%s #threads = %d%n", Instant.now(), threadCount);
55 for (int lockCount = MIN_MONITORS; lockCount <= MAX_MONITORS; lockCount += 2) {
56 test(threadCount, lockCount);
57 }
58 }
59 }
60
61 /**
62 * Test threads entering monitors and using Object.wait(millis) to wait. This
63 * testing scenario leads to a mix of contention (with responsible threads using
64 * short timeouts), timed-wait, and cancellation of timer tasks. This scenario
65 * can result in contention of the timer queue.
66 */
67 static void test(int threadCount, int monitorCount) {
68 var locks = new Object[monitorCount];
69 for (int i = 0; i < monitorCount; i++) {
70 locks[i] = new Object();
71 }
72
73 try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
74 var finished = new AtomicInteger();
75
76 for (int i = 0; i < threadCount; i++) {
77 Object lock = locks[RAND.nextInt(monitorCount)]; // random lock
78
79 executor.submit(() -> {
80 synchronized (lock) {
81 lock.wait(Long.MAX_VALUE);
82 }
83 finished.incrementAndGet();
84 return null;
85 });
86
87 synchronized (lock) {
88 lock.notify();
89 }
90 }
91
92 // notify at most one thread until all threads are finished
93 while (finished.get() < threadCount) {
94 for (Object lock : locks) {
95 synchronized (lock) {
96 lock.notify();
97 }
98 }
99 }
100 }
101 }
102 }