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