1 /*
2 * Copyright (c) 2005, 2022, 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 import java.io.IOException;
29 import java.nio.channels.ClosedSelectorException;
30 import java.nio.channels.SelectionKey;
31 import java.nio.channels.Selector;
32 import java.nio.channels.spi.SelectorProvider;
33 import java.util.ArrayDeque;
34 import java.util.Deque;
35 import java.util.HashMap;
36 import java.util.Map;
37 import java.util.concurrent.TimeUnit;
38 import java.util.function.Consumer;
39
40 import static sun.nio.ch.EPoll.EPOLLIN;
41 import static sun.nio.ch.EPoll.EPOLL_CTL_ADD;
42 import static sun.nio.ch.EPoll.EPOLL_CTL_DEL;
43 import static sun.nio.ch.EPoll.EPOLL_CTL_MOD;
44
45
46 /**
47 * Linux epoll based Selector implementation
48 */
49
50 class EPollSelectorImpl extends SelectorImpl {
51
52 // maximum number of events to poll in one call to epoll_wait
53 private static final int NUM_EPOLLEVENTS = Math.min(IOUtil.fdLimit(), 1024);
54
55 // epoll file descriptor
56 private final int epfd;
57
58 // address of poll array when polling with epoll_wait
59 private final long pollArrayAddress;
60
61 // eventfd object used for interrupt
62 private final EventFD eventfd;
63
64 // maps file descriptor to selection key, synchronize on selector
65 private final Map<Integer, SelectionKeyImpl> fdToKey = new HashMap<>();
66
67 // pending new registrations/updates, queued by setEventOps
68 private final Object updateLock = new Object();
69 private final Deque<SelectionKeyImpl> updateKeys = new ArrayDeque<>();
70
71 // interrupt triggering and clearing
72 private final Object interruptLock = new Object();
73 private boolean interruptTriggered;
74
75 EPollSelectorImpl(SelectorProvider sp) throws IOException {
76 super(sp);
77
78 this.epfd = EPoll.create();
79 this.pollArrayAddress = EPoll.allocatePollArray(NUM_EPOLLEVENTS);
80
81 try {
82 this.eventfd = new EventFD();
83 IOUtil.configureBlocking(IOUtil.newFD(eventfd.efd()), false);
84 } catch (IOException ioe) {
85 EPoll.freePollArray(pollArrayAddress);
86 FileDispatcherImpl.closeIntFD(epfd);
87 throw ioe;
88 }
89
90 // register the eventfd object for wakeups
91 EPoll.ctl(epfd, EPOLL_CTL_ADD, eventfd.efd(), EPOLLIN);
92 }
93
94 private void ensureOpen() {
95 if (!isOpen())
96 throw new ClosedSelectorException();
97 }
98
99 @Override
100 protected int doSelect(Consumer<SelectionKey> action, long timeout)
101 throws IOException
102 {
103 assert Thread.holdsLock(this);
104
105 // epoll_wait timeout is int
106 int to = (int) Math.min(timeout, Integer.MAX_VALUE);
107 boolean blocking = (to != 0);
108 boolean timedPoll = (to > 0);
109
110 int numEntries;
111 processUpdateQueue();
112 processDeregisterQueue();
113
114 if (Thread.currentThread().isVirtual()) {
115 numEntries = (timedPoll)
116 ? timedPoll(TimeUnit.MILLISECONDS.toNanos(to))
117 : untimedPoll(blocking);
118 } else {
119 try {
120 begin(blocking);
121 do {
122 long startTime = timedPoll ? System.nanoTime() : 0;
123 numEntries = EPoll.wait(epfd, pollArrayAddress, NUM_EPOLLEVENTS, to);
124 if (numEntries == IOStatus.INTERRUPTED && timedPoll) {
125 // timed poll interrupted so need to adjust timeout
126 long adjust = System.nanoTime() - startTime;
127 to -= (int) TimeUnit.NANOSECONDS.toMillis(adjust);
128 if (to <= 0) {
129 // timeout expired so no retry
130 numEntries = 0;
131 }
132 }
133 } while (numEntries == IOStatus.INTERRUPTED);
134 } finally {
135 end(blocking);
136 }
137 }
138 assert IOStatus.check(numEntries);
139
140 processDeregisterQueue();
141 return processEvents(numEntries, action);
142 }
143
144 /**
145 * If blocking, parks the current virtual thread until a file descriptor is polled
146 * or the thread is interrupted.
147 */
148 private int untimedPoll(boolean block) throws IOException {
149 int numEntries = EPoll.wait(epfd, pollArrayAddress, NUM_EPOLLEVENTS, 0);
150 if (block) {
151 while (numEntries == 0 && !Thread.currentThread().isInterrupted()) {
152 Poller.pollSelector(epfd, 0);
153 numEntries = EPoll.wait(epfd, pollArrayAddress, NUM_EPOLLEVENTS, 0);
154 }
155 }
156 return numEntries;
157 }
158
159 /**
160 * Parks the current virtual thread until a file descriptor is polled, or the thread
161 * is interrupted, for up to the specified waiting time.
162 */
163 private int timedPoll(long nanos) throws IOException {
164 long startNanos = System.nanoTime();
165 int numEntries = EPoll.wait(epfd, pollArrayAddress, NUM_EPOLLEVENTS, 0);
166 while (numEntries == 0 && !Thread.currentThread().isInterrupted()) {
167 long remainingNanos = nanos - (System.nanoTime() - startNanos);
168 if (remainingNanos <= 0) {
169 // timeout
170 break;
171 }
172 Poller.pollSelector(epfd, remainingNanos);
173 numEntries = EPoll.wait(epfd, pollArrayAddress, NUM_EPOLLEVENTS, 0);
174 }
175 return numEntries;
176 }
177
178 /**
179 * Process changes to the interest ops.
180 */
181 private void processUpdateQueue() {
182 assert Thread.holdsLock(this);
183
184 synchronized (updateLock) {
185 SelectionKeyImpl ski;
186 while ((ski = updateKeys.pollFirst()) != null) {
187 if (ski.isValid()) {
188 int fd = ski.getFDVal();
189 // add to fdToKey if needed
190 SelectionKeyImpl previous = fdToKey.putIfAbsent(fd, ski);
191 assert (previous == null) || (previous == ski);
192
193 int newEvents = ski.translateInterestOps();
194 int registeredEvents = ski.registeredEvents();
195 if (newEvents != registeredEvents) {
196 if (newEvents == 0) {
197 // remove from epoll
198 EPoll.ctl(epfd, EPOLL_CTL_DEL, fd, 0);
199 } else {
200 if (registeredEvents == 0) {
201 // add to epoll
202 EPoll.ctl(epfd, EPOLL_CTL_ADD, fd, newEvents);
203 } else {
204 // modify events
205 EPoll.ctl(epfd, EPOLL_CTL_MOD, fd, newEvents);
206 }
207 }
208 ski.registeredEvents(newEvents);
209 }
210 }
211 }
212 }
213 }
214
215 /**
216 * Process the polled events.
217 * If the interrupt fd has been selected, drain it and clear the interrupt.
218 */
219 private int processEvents(int numEntries, Consumer<SelectionKey> action)
220 throws IOException
221 {
222 assert Thread.holdsLock(this);
223
224 boolean interrupted = false;
225 int numKeysUpdated = 0;
226 for (int i=0; i<numEntries; i++) {
227 long event = EPoll.getEvent(pollArrayAddress, i);
228 int fd = EPoll.getDescriptor(event);
229 if (fd == eventfd.efd()) {
230 interrupted = true;
231 } else {
232 SelectionKeyImpl ski = fdToKey.get(fd);
233 if (ski != null) {
234 int rOps = EPoll.getEvents(event);
235 numKeysUpdated += processReadyEvents(rOps, ski, action);
236 }
237 }
238 }
239
240 if (interrupted) {
241 clearInterrupt();
242 }
243
244 return numKeysUpdated;
245 }
246
247 @Override
248 protected void implClose() throws IOException {
249 assert Thread.holdsLock(this);
250
251 // prevent further wakeup
252 synchronized (interruptLock) {
253 interruptTriggered = true;
254 }
255
256 FileDispatcherImpl.closeIntFD(epfd);
257 EPoll.freePollArray(pollArrayAddress);
258
259 eventfd.close();
260 }
261
262 @Override
263 protected void implDereg(SelectionKeyImpl ski) throws IOException {
264 assert !ski.isValid();
265 assert Thread.holdsLock(this);
266
267 int fd = ski.getFDVal();
268 if (fdToKey.remove(fd) != null) {
269 if (ski.registeredEvents() != 0) {
270 EPoll.ctl(epfd, EPOLL_CTL_DEL, fd, 0);
271 ski.registeredEvents(0);
272 }
273 } else {
274 assert ski.registeredEvents() == 0;
275 }
276 }
277
278 @Override
279 public void setEventOps(SelectionKeyImpl ski) {
280 ensureOpen();
281 synchronized (updateLock) {
282 updateKeys.addLast(ski);
283 }
284 }
285
286 @Override
287 public Selector wakeup() {
288 synchronized (interruptLock) {
289 if (!interruptTriggered) {
290 try {
291 eventfd.set();
292 } catch (IOException ioe) {
293 throw new InternalError(ioe);
294 }
295 interruptTriggered = true;
296 }
297 }
298 return this;
299 }
300
301 private void clearInterrupt() throws IOException {
302 synchronized (interruptLock) {
303 eventfd.reset();
304 interruptTriggered = false;
305 }
306 }
307 }