1 /*
2 * Copyright (c) 2002, 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. 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 sun.nio.ch;
27
28 // Special-purpose data structure for sets of native threads
29
30 class NativeThreadSet {
31 private static final int OTHER_THREAD_INDEX = -99;
32
33 private final int initialCapacity;
34 private Thread[] threads; // array of platform threads, created lazily
35 private int used; // number of elements in threads array
36 private int otherThreads; // additional threads that can't be signalled
37 private boolean waitingToEmpty;
38
39 NativeThreadSet(int n) {
40 initialCapacity = n;
41 }
42
43 /**
44 * Adds the current thread handle to this set, returning an index so that
45 * it can efficiently be removed later.
46 */
47 int add() {
48 synchronized (this) {
49 final Thread t = NativeThread.threadToSignal();
50 if (t == null || t.isVirtual()) {
51 otherThreads++;
52 return OTHER_THREAD_INDEX;
53 }
54
55 // add platform threads to array, creating or growing array if needed
56 int start = 0;
57 if (threads == null) {
58 threads = new Thread[initialCapacity];
59 } else if (used >= threads.length) {
60 int on = threads.length;
61 int nn = on * 2;
62 Thread[] nthreads = new Thread[nn];
63 System.arraycopy(threads, 0, nthreads, 0, on);
64 threads = nthreads;
65 start = on;
66 }
67 for (int i = start; i < threads.length; i++) {
68 if (threads[i] == null) {
69 threads[i] = t;
70 used++;
71 return i;
72 }
73 }
74 throw new InternalError();
75 }
76 }
77
78 /**
79 * Removes the thread at the given index. A no-op if index is -1.
80 */
81 void remove(int i) {
82 synchronized (this) {
83 if (i >= 0) {
84 threads[i] = null;
85 used--;
86 } else if (i == OTHER_THREAD_INDEX) {
87 otherThreads--;
88 } else {
89 assert i == -1;
90 return;
91 }
92 if (used == 0 && otherThreads == 0 && waitingToEmpty) {
93 notifyAll();
94 }
95 }
96 }
97
98 /**
99 * Signals all native threads in the thread set and wait for the thread set to empty.
100 */
101 synchronized void signalAndWait() {
102 boolean interrupted = false;
103 while (used > 0 || otherThreads > 0) {
104 int u = used, i = 0;
105 while (u > 0 && i < threads.length) {
106 Thread t = threads[i];
107 if (t != null) {
108 NativeThread.signal(t);
109 u--;
110 }
111 i++;
112 }
113 waitingToEmpty = true;
114 try {
115 wait(50);
116 } catch (InterruptedException e) {
117 interrupted = true;
118 } finally {
119 waitingToEmpty = false;
120 }
121 }
122 if (interrupted)
123 Thread.currentThread().interrupt();
124 }
125 }