1 /*
2 * Copyright (c) 2018, 2022, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package jdk.internal.misc;
27
28 import java.util.concurrent.TimeUnit;
29 import java.util.concurrent.RejectedExecutionException;
30 import jdk.internal.access.JavaLangAccess;
31 import jdk.internal.access.SharedSecrets;
32
33 /**
34 * Defines static methods to support execution in the context of a virtual thread.
35 */
36 public final class VirtualThreads {
37 private static final JavaLangAccess JLA;
38 static {
39 JLA = SharedSecrets.getJavaLangAccess();
40 if (JLA == null) {
41 throw new InternalError("JavaLangAccess not setup");
42 }
43 }
44 private VirtualThreads() { }
45
46 /**
47 * Parks the current virtual thread until it is unparked or interrupted.
48 * If already unparked then the parking permit is consumed and this method
49 * completes immediately (meaning it doesn't yield). It also completes
50 * immediately if the interrupt status is set.
51 * @throws WrongThreadException if the current thread is not a virtual thread
52 */
53 public static void park() {
54 JLA.parkVirtualThread();
55 }
56
57 /**
58 * Parks the current virtual thread up to the given waiting time or until it
59 * is unparked or interrupted. If already unparked then the parking permit is
60 * consumed and this method completes immediately (meaning it doesn't yield).
61 * It also completes immediately if the interrupt status is set or the waiting
62 * time is {@code <= 0}.
63 * @param nanos the maximum number of nanoseconds to wait
64 * @throws WrongThreadException if the current thread is not a virtual thread
65 */
66 public static void park(long nanos) {
67 JLA.parkVirtualThread(nanos);
68 }
69
70 /**
71 * Parks the current virtual thread until the given deadline or until is is
72 * unparked or interrupted. If already unparked then the parking permit is
73 * consumed and this method completes immediately (meaning it doesn't yield).
74 * It also completes immediately if the interrupt status is set or the
75 * deadline has past.
76 * @param deadline absolute time, in milliseconds, from the epoch
77 * @throws WrongThreadException if the current thread is not a virtual thread
78 */
79 public static void parkUntil(long deadline) {
80 long millis = deadline - System.currentTimeMillis();
81 long nanos = TimeUnit.NANOSECONDS.convert(millis, TimeUnit.MILLISECONDS);
82 park(nanos);
83 }
84
85 /**
86 * Re-enables a virtual thread for scheduling. If the thread was parked then
87 * it will be unblocked, otherwise its next attempt to park will not block
88 * @param thread the virtual thread to unpark
89 * @throws IllegalArgumentException if the thread is not a virtual thread
90 * @throws RejectedExecutionException if the scheduler cannot accept a task
91 */
92 public static void unpark(Thread thread) {
93 JLA.unparkVirtualThread(thread);
94 }
95 }