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