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 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 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 /**
132 * Process changes to the interest ops.
133 */
134 private void processUpdateQueue() {
135 assert Thread.holdsLock(this);
136
137 synchronized (updateLock) {
138 SelectionKeyImpl ski;
139 while ((ski = updateKeys.pollFirst()) != null) {
140 int newEvents = ski.translateInterestOps();
141 if (ski.isValid()) {
142 int index = ski.getIndex();
143 assert index >= 0 && index < pollArraySize;
144 if (index > 0) {
145 assert pollKeys.get(index) == ski;
146 if (newEvents == 0) {
147 remove(ski);
148 } else {
149 update(ski, newEvents);
150 }
151 } else if (newEvents != 0) {
152 add(ski, newEvents);
153 }
154 }
155 }
156 }
157 }
158
159 /**
160 * Update the keys of file descriptors that were polled and add them to
161 * the selected-key set.
162 * If the interrupt fd has been selected, drain it and clear the interrupt.
163 */
164 private int updateSelectedKeys() throws IOException {
165 assert Thread.holdsLock(this);
166 assert Thread.holdsLock(nioSelectedKeys());
167 assert pollArraySize > 0 && pollArraySize == pollKeys.size();
168
169 int numKeysUpdated = 0;
170 for (int i = 1; i < pollArraySize; i++) {
171 int rOps = getReventOps(i);
172 if (rOps != 0) {
173 SelectionKeyImpl ski = pollKeys.get(i);
174 assert ski.getFDVal() == getDescriptor(i);
175 if (ski.isValid()) {
176 if (selectedKeys.contains(ski)) {
177 if (ski.translateAndUpdateReadyOps(rOps)) {
178 numKeysUpdated++;
179 }
180 } else {
181 ski.translateAndSetReadyOps(rOps);
182 if ((ski.nioReadyOps() & ski.nioInterestOps()) != 0) {
183 selectedKeys.add(ski);
184 numKeysUpdated++;
185 }
186 }
187 }
188 }
189 }
190
191 // check for interrupt
192 if (getReventOps(0) != 0) {
193 assert getDescriptor(0) == fd0;
194 clearInterrupt();
195 }
196
197 return numKeysUpdated;
198 }
199
200 @Override
201 protected void implClose() throws IOException {
202 assert !isOpen();
203 assert Thread.holdsLock(this);
204
205 // prevent further wakeup
206 synchronized (interruptLock) {
207 interruptTriggered = true;
208 }
209
210 pollArray.free();
211 FileDispatcherImpl.closeIntFD(fd0);
212 FileDispatcherImpl.closeIntFD(fd1);
213 }
214
215 @Override
216 protected void implRegister(SelectionKeyImpl ski) {
217 assert ski.getIndex() == 0;
218 ensureOpen();
219 }
220
221 @Override
222 protected void implDereg(SelectionKeyImpl ski) throws IOException {
223 assert !ski.isValid();
224 assert Thread.holdsLock(this);
225
226 // remove from poll array
227 int index = ski.getIndex();
228 if (index > 0) {
229 remove(ski);
230 }
231 }
232
233 @Override
234 public void setEventOps(SelectionKeyImpl ski) {
235 ensureOpen();
236 synchronized (updateLock) {
237 updateKeys.addLast(ski);
238 }
239 }
240
241 @Override
242 public Selector wakeup() {
243 synchronized (interruptLock) {
244 if (!interruptTriggered) {
245 try {
246 IOUtil.write1(fd1, (byte)0);
247 } catch (IOException ioe) {
248 throw new InternalError(ioe);
249 }
250 interruptTriggered = true;
251 }
252 }
253 return this;
254 }
255
256 private void clearInterrupt() throws IOException {
257 synchronized (interruptLock) {
258 IOUtil.drain(fd0);
259 interruptTriggered = false;
260 }
261 }
262
263 /**
264 * Sets the first pollfd enty in the poll array to the given fd
265 */
266 private void setFirst(int fd, int ops) {
267 assert pollArraySize == 0;
268 assert pollKeys.isEmpty();
269
270 putDescriptor(0, fd);
271 putEventOps(0, ops);
272 pollArraySize = 1;
273
274 pollKeys.add(null); // dummy element
275 }
276
277 /**
278 * Adds a pollfd entry to the poll array, expanding the poll array if needed.
279 */
280 private void add(SelectionKeyImpl ski, int ops) {
281 expandIfNeeded();
282
283 int index = pollArraySize;
284 assert index > 0;
285 putDescriptor(index, ski.getFDVal());
286 putEventOps(index, ops);
287 putReventOps(index, 0);
288 ski.setIndex(index);
289 pollArraySize++;
290
291 pollKeys.add(ski);
292 assert pollKeys.size() == pollArraySize;
293 }
294
295 /**
296 * Update the events of pollfd entry.
297 */
298 private void update(SelectionKeyImpl ski, int ops) {
299 int index = ski.getIndex();
300 assert index > 0 && index < pollArraySize;
301 assert getDescriptor(index) == ski.getFDVal();
302 putEventOps(index, ops);
303 }
304
305 /**
306 * Removes a pollfd entry from the poll array
307 */
308 private void remove(SelectionKeyImpl ski) {
309 int index = ski.getIndex();
310 assert index > 0 && index < pollArraySize;
311 assert getDescriptor(index) == ski.getFDVal();
312
313 // replace pollfd at index with the last pollfd in array
314 int lastIndex = pollArraySize - 1;
315 if (lastIndex != index) {
316 SelectionKeyImpl lastKey = pollKeys.get(lastIndex);
317 assert lastKey.getIndex() == lastIndex;
318 int lastFd = getDescriptor(lastIndex);
319 int lastOps = getEventOps(lastIndex);
320 int lastRevents = getReventOps(lastIndex);
321 assert lastKey.getFDVal() == lastFd;
322 putDescriptor(index, lastFd);
323 putEventOps(index, lastOps);
324 putReventOps(index, lastRevents);
325 pollKeys.set(index, lastKey);
326 lastKey.setIndex(index);
327 }
328 pollKeys.remove(lastIndex);
329 pollArraySize--;
330 assert pollKeys.size() == pollArraySize;
331
332 ski.setIndex(0);
333 }
334
335 /**
336 * Expand poll array if at capacity
337 */
338 private void expandIfNeeded() {
339 if (pollArraySize == pollArrayCapacity) {
340 int oldSize = pollArrayCapacity * SIZE_POLLFD;
341 int newCapacity = pollArrayCapacity + INITIAL_CAPACITY;
342 int newSize = newCapacity * SIZE_POLLFD;
343 AllocatedNativeObject newPollArray = new AllocatedNativeObject(newSize, false);
344 Unsafe.getUnsafe().copyMemory(pollArray.address(), newPollArray.address(), oldSize);
345 pollArray.free();
346 pollArray = newPollArray;
347 pollArrayCapacity = newCapacity;
348 }
349 }
350
351 private static final short SIZE_POLLFD = 8;
352 private static final short FD_OFFSET = 0;
353 private static final short EVENT_OFFSET = 4;
354 private static final short REVENT_OFFSET = 6;
355
356 private void putDescriptor(int i, int fd) {
357 int offset = SIZE_POLLFD * i + FD_OFFSET;
358 pollArray.putInt(offset, fd);
359 }
360
361 private int getDescriptor(int i) {
362 int offset = SIZE_POLLFD * i + FD_OFFSET;
363 return pollArray.getInt(offset);
364 }
365
366 private void putEventOps(int i, int event) {
367 int offset = SIZE_POLLFD * i + EVENT_OFFSET;
368 pollArray.putShort(offset, (short)event);
369 }
370
371 private int getEventOps(int i) {
372 int offset = SIZE_POLLFD * i + EVENT_OFFSET;
373 return pollArray.getShort(offset);
374 }
375
376 private void putReventOps(int i, int revent) {
377 int offset = SIZE_POLLFD * i + REVENT_OFFSET;
378 pollArray.putShort(offset, (short)revent);
379 }
380
381 private int getReventOps(int i) {
382 int offset = SIZE_POLLFD * i + REVENT_OFFSET;
383 return pollArray.getShort(offset);
384 }
385
386 private static native int poll(long pollAddress, int numfds, int timeout);
387
388 static {
389 IOUtil.load();
390 }
391 }