1 /*
2 * Copyright (c) 2001, 2018, 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 package sun.nio.ch;
26
27 import java.io.IOException;
28 import java.nio.channels.ClosedSelectorException;
29 import java.nio.channels.Selector;
30 import java.nio.channels.spi.SelectorProvider;
31 import java.util.ArrayDeque;
32 import java.util.ArrayList;
33 import java.util.Deque;
34 import java.util.List;
35 import java.util.concurrent.TimeUnit;
36
37 import jdk.internal.misc.Unsafe;
38
39 /**
40 * Selector implementation based on poll
41 */
42
43 public class PollSelectorImpl extends SelectorImpl {
44
45 // initial capacity of poll array
46 private static final int INITIAL_CAPACITY = 16;
47
48 // poll array, grows as needed
49 private int pollArrayCapacity = INITIAL_CAPACITY;
50 private int pollArraySize;
51 private AllocatedNativeObject pollArray;
52
53 // file descriptors used for interrupt
54 private final int fd0;
55 private final int fd1;
56
57 // keys for file descriptors in poll array, synchronize on selector
58 private final List<SelectionKeyImpl> pollKeys = new ArrayList<>();
59
60 // pending updates, queued by putEventOps
61 private final Object updateLock = new Object();
62 private final Deque<SelectionKeyImpl> updateKeys = new ArrayDeque<>();
63
64 // interrupt triggering and clearing
65 private final Object interruptLock = new Object();
66 private boolean interruptTriggered;
67
68 protected PollSelectorImpl(SelectorProvider sp) throws IOException {
69 super(sp);
70
71 int size = pollArrayCapacity * SIZE_POLLFD;
72 this.pollArray = new AllocatedNativeObject(size, false);
73
74 try {
75 long fds = IOUtil.makePipe(false);
76 this.fd0 = (int) (fds >>> 32);
77 this.fd1 = (int) fds;
78 } catch (IOException ioe) {
79 pollArray.free();
80 throw ioe;
81 }
82
83 // wakeup support
84 synchronized (this) {
85 setFirst(fd0, Net.POLLIN);
86 }
87 }
88
89 private void ensureOpen() {
90 if (!isOpen())
91 throw new ClosedSelectorException();
92 }
93
94 @Override
95 protected int doSelect(long timeout) throws IOException {
96 assert Thread.holdsLock(this);
97
98 int to = (int) Math.min(timeout, Integer.MAX_VALUE); // max poll timeout
99 boolean blocking = (to != 0);
100 boolean timedPoll = (to > 0);
101
102 processUpdateQueue();
103 processDeregisterQueue();
104 try {
105 begin(blocking);
106
107 int numPolled;
108 do {
109 long startTime = timedPoll ? System.nanoTime() : 0;
110 numPolled = poll(pollArray.address(), pollArraySize, to);
111 if (numPolled == IOStatus.INTERRUPTED && timedPoll) {
112 // timed poll interrupted so need to adjust timeout
113 long adjust = System.nanoTime() - startTime;
114 to -= TimeUnit.MILLISECONDS.convert(adjust, TimeUnit.NANOSECONDS);
115 if (to <= 0) {
116 // timeout expired so no retry
117 numPolled = 0;
118 }
119 }
120 } while (numPolled == IOStatus.INTERRUPTED);
121 assert numPolled <= pollArraySize;
122
123 } finally {
124 end(blocking);
125 }
126
127 processDeregisterQueue();
128 return updateSelectedKeys();
129 }
130
131 protected int poll(long pollAddress, int numfds, int timeout) {
132 return poll0(pollAddress, numfds, timeout);
133 }
134
135 /**
136 * Process changes to the interest ops.
137 */
138 private void processUpdateQueue() {
139 assert Thread.holdsLock(this);
140
141 synchronized (updateLock) {
142 SelectionKeyImpl ski;
143 while ((ski = updateKeys.pollFirst()) != null) {
144 int newEvents = ski.translateInterestOps();
145 if (ski.isValid()) {
146 int index = ski.getIndex();
147 assert index >= 0 && index < pollArraySize;
148 if (index > 0) {
149 assert pollKeys.get(index) == ski;
150 if (newEvents == 0) {
151 remove(ski);
152 } else {
153 update(ski, newEvents);
154 }
155 } else if (newEvents != 0) {
156 add(ski, newEvents);
157 }
158 }
159 }
160 }
161 }
162
163 /**
164 * Update the keys of file descriptors that were polled and add them to
165 * the selected-key set.
166 * If the interrupt fd has been selected, drain it and clear the interrupt.
167 */
168 private int updateSelectedKeys() throws IOException {
169 assert Thread.holdsLock(this);
170 assert Thread.holdsLock(nioSelectedKeys());
171 assert pollArraySize > 0 && pollArraySize == pollKeys.size();
172
173 int numKeysUpdated = 0;
174 for (int i = 1; i < pollArraySize; i++) {
175 int rOps = getReventOps(i);
176 if (rOps != 0) {
177 SelectionKeyImpl ski = pollKeys.get(i);
178 assert ski.getFDVal() == getDescriptor(i);
179 if (ski.isValid()) {
180 if (selectedKeys.contains(ski)) {
181 if (ski.translateAndUpdateReadyOps(rOps)) {
182 numKeysUpdated++;
183 }
184 } else {
185 ski.translateAndSetReadyOps(rOps);
186 if ((ski.nioReadyOps() & ski.nioInterestOps()) != 0) {
187 selectedKeys.add(ski);
188 numKeysUpdated++;
189 }
190 }
191 }
192 }
193 }
194
195 // check for interrupt
196 if (getReventOps(0) != 0) {
197 assert getDescriptor(0) == fd0;
198 clearInterrupt();
199 }
200
201 return numKeysUpdated;
202 }
203
204 @Override
205 protected void implClose() throws IOException {
206 assert !isOpen();
207 assert Thread.holdsLock(this);
208
209 // prevent further wakeup
210 synchronized (interruptLock) {
211 interruptTriggered = true;
212 }
213
214 pollArray.free();
215 FileDispatcherImpl.closeIntFD(fd0);
216 FileDispatcherImpl.closeIntFD(fd1);
217 }
218
219 @Override
220 protected void implRegister(SelectionKeyImpl ski) {
221 assert ski.getIndex() == 0;
222 ensureOpen();
223 }
224
225 @Override
226 protected void implDereg(SelectionKeyImpl ski) throws IOException {
227 assert !ski.isValid();
228 assert Thread.holdsLock(this);
229
230 // remove from poll array
231 int index = ski.getIndex();
232 if (index > 0) {
233 remove(ski);
234 }
235 }
236
237 @Override
238 public void setEventOps(SelectionKeyImpl ski) {
239 ensureOpen();
240 synchronized (updateLock) {
241 updateKeys.addLast(ski);
242 }
243 }
244
245 @Override
246 public Selector wakeup() {
247 synchronized (interruptLock) {
248 if (!interruptTriggered) {
249 try {
250 IOUtil.write1(fd1, (byte)0);
251 } catch (IOException ioe) {
252 throw new InternalError(ioe);
253 }
254 interruptTriggered = true;
255 }
256 }
257 return this;
258 }
259
260 private void clearInterrupt() throws IOException {
261 synchronized (interruptLock) {
262 IOUtil.drain(fd0);
263 interruptTriggered = false;
264 }
265 }
266
267 /**
268 * Sets the first pollfd enty in the poll array to the given fd
269 */
270 private void setFirst(int fd, int ops) {
271 assert pollArraySize == 0;
272 assert pollKeys.isEmpty();
273
274 putDescriptor(0, fd);
275 putEventOps(0, ops);
276 pollArraySize = 1;
277
278 pollKeys.add(null); // dummy element
279 }
280
281 /**
282 * Adds a pollfd entry to the poll array, expanding the poll array if needed.
283 */
284 private void add(SelectionKeyImpl ski, int ops) {
285 expandIfNeeded();
286
287 int index = pollArraySize;
288 assert index > 0;
289 putDescriptor(index, ski.getFDVal());
290 putEventOps(index, ops);
291 putReventOps(index, 0);
292 ski.setIndex(index);
293 pollArraySize++;
294
295 pollKeys.add(ski);
296 assert pollKeys.size() == pollArraySize;
297 }
298
299 /**
300 * Update the events of pollfd entry.
301 */
302 private void update(SelectionKeyImpl ski, int ops) {
303 int index = ski.getIndex();
304 assert index > 0 && index < pollArraySize;
305 assert getDescriptor(index) == ski.getFDVal();
306 putEventOps(index, ops);
307 }
308
309 /**
310 * Removes a pollfd entry from the poll array
311 */
312 private void remove(SelectionKeyImpl ski) {
313 int index = ski.getIndex();
314 assert index > 0 && index < pollArraySize;
315 assert getDescriptor(index) == ski.getFDVal();
316
317 // replace pollfd at index with the last pollfd in array
318 int lastIndex = pollArraySize - 1;
319 if (lastIndex != index) {
320 SelectionKeyImpl lastKey = pollKeys.get(lastIndex);
321 assert lastKey.getIndex() == lastIndex;
322 int lastFd = getDescriptor(lastIndex);
323 int lastOps = getEventOps(lastIndex);
324 int lastRevents = getReventOps(lastIndex);
325 assert lastKey.getFDVal() == lastFd;
326 putDescriptor(index, lastFd);
327 putEventOps(index, lastOps);
328 putReventOps(index, lastRevents);
329 pollKeys.set(index, lastKey);
330 lastKey.setIndex(index);
331 }
332 pollKeys.remove(lastIndex);
333 pollArraySize--;
334 assert pollKeys.size() == pollArraySize;
335
336 ski.setIndex(0);
337 }
338
339 /**
340 * Expand poll array if at capacity
341 */
342 private void expandIfNeeded() {
343 if (pollArraySize == pollArrayCapacity) {
344 int oldSize = pollArrayCapacity * SIZE_POLLFD;
345 int newCapacity = pollArrayCapacity + INITIAL_CAPACITY;
346 int newSize = newCapacity * SIZE_POLLFD;
347 AllocatedNativeObject newPollArray = new AllocatedNativeObject(newSize, false);
348 Unsafe.getUnsafe().copyMemory(pollArray.address(), newPollArray.address(), oldSize);
349 pollArray.free();
350 pollArray = newPollArray;
351 pollArrayCapacity = newCapacity;
352 }
353 }
354
355 private static final short SIZE_POLLFD = 8;
356 private static final short FD_OFFSET = 0;
357 private static final short EVENT_OFFSET = 4;
358 private static final short REVENT_OFFSET = 6;
359
360 private void putDescriptor(int i, int fd) {
361 int offset = SIZE_POLLFD * i + FD_OFFSET;
362 pollArray.putInt(offset, fd);
363 }
364
365 private int getDescriptor(int i) {
366 int offset = SIZE_POLLFD * i + FD_OFFSET;
367 return pollArray.getInt(offset);
368 }
369
370 private void putEventOps(int i, int event) {
371 int offset = SIZE_POLLFD * i + EVENT_OFFSET;
372 pollArray.putShort(offset, (short)event);
373 }
374
375 private int getEventOps(int i) {
376 int offset = SIZE_POLLFD * i + EVENT_OFFSET;
377 return pollArray.getShort(offset);
378 }
379
380 private void putReventOps(int i, int revent) {
381 int offset = SIZE_POLLFD * i + REVENT_OFFSET;
382 pollArray.putShort(offset, (short)revent);
383 }
384
385 private int getReventOps(int i) {
386 int offset = SIZE_POLLFD * i + REVENT_OFFSET;
387 return pollArray.getShort(offset);
388 }
389
390 private static native int poll0(long pollAddress, int numfds, int timeout);
391
392 static {
393 IOUtil.load();
394 }
395 }