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