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 * @bug 8330748
27 * @summary Test ByteArrayOutputStream.writeTo releases carrier thread
28 * @requires vm.continuations
29 * @modules java.base/java.lang:+open
30 * @library /test/lib
31 * @run main WriteToReleasesCarrier
32 */
33
34 import java.io.ByteArrayOutputStream;
35 import java.io.IOException;
36 import java.io.OutputStream;
37 import java.nio.charset.StandardCharsets;
38 import java.util.Arrays;
39 import java.util.concurrent.CountDownLatch;
40 import java.util.concurrent.ExecutorService;
41 import java.util.concurrent.Executor;
42 import java.util.concurrent.Executors;
43 import java.util.concurrent.atomic.AtomicBoolean;
44 import java.util.concurrent.locks.LockSupport;
45 import jdk.test.lib.thread.VThreadScheduler;
46
47 public class WriteToReleasesCarrier {
48 public static void main(String[] args) throws Exception {
49 byte[] bytes = "Hello".getBytes(StandardCharsets.UTF_8);
50
51 var baos = new ByteArrayOutputStream();
52 baos.write(bytes);
53
54 var target = new ParkingOutputStream();
55
56 try (ExecutorService scheduler = Executors.newFixedThreadPool(1)) {
57 Thread.Builder builder = VThreadScheduler.virtualThreadBuilder(scheduler);
58 var started = new CountDownLatch(1);
59 var vthread1 = builder.start(() -> {
60 started.countDown();
61 try {
62 baos.writeTo(target);
63 } catch (IOException ioe) { }
64 });
65 try {
66 started.await();
67 await(vthread1, Thread.State.WAITING);
68
69 // carrier should be released, use it for another thread
70 var executed = new AtomicBoolean();
71 var vthread2 = builder.start(() -> {
72 executed.set(true);
73 });
74 vthread2.join();
75 if (!executed.get()) {
76 throw new RuntimeException("Second virtual thread did not run");
77 }
78 } finally {
79 LockSupport.unpark(vthread1);
80 vthread1.join();
81 }
82 }
83
84 if (!Arrays.equals(target.toByteArray(), bytes)) {
85 throw new RuntimeException("Expected bytes not written");
86 }
87 }
88
89 /**
90 * Waits for a thread to get to the expected state.
91 */
92 private static void await(Thread thread, Thread.State expectedState) throws Exception {
93 Thread.State state = thread.getState();
94 while (state != expectedState) {
95 Thread.sleep(10);
96 state = thread.getState();
97 }
98 }
99
100 /**
101 * An OutputStream that parks when writing.
102 */
103 static class ParkingOutputStream extends OutputStream {
104 final ByteArrayOutputStream baos = new ByteArrayOutputStream();
105
106 @Override
107 public void write(int i) {
108 LockSupport.park();
109 baos.write(i);
110 }
111
112 @Override
113 public void write(byte[] b, int off, int len) {
114 LockSupport.park();
115 baos.write(b, off, len);
116 }
117
118 byte[] toByteArray() {
119 return baos.toByteArray();
120 }
121 }
122 }