1 /*
2 * Copyright (c) 2005, 2024, 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 import jdk.internal.misc.Blocker;
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 @Override
95 protected int doSelect(Consumer<SelectionKey> action, long timeout)
96 throws IOException
97 {
98 assert Thread.holdsLock(this);
99
100 // epoll_wait timeout is int
101 int to = (int) Math.min(timeout, Integer.MAX_VALUE);
102 boolean blocking = (to != 0);
103 boolean timedPoll = (to > 0);
104
105 int numEntries;
106 processUpdateQueue();
107 processDeregisterQueue();
108 try {
109 begin(blocking);
110
111 do {
112 long startTime = timedPoll ? System.nanoTime() : 0;
113 boolean attempted = Blocker.begin(blocking);
114 try {
115 numEntries = EPoll.wait(epfd, pollArrayAddress, NUM_EPOLLEVENTS, to);
116 } finally {
117 Blocker.end(attempted);
118 }
119 if (numEntries == IOStatus.INTERRUPTED && timedPoll) {
120 // timed poll interrupted so need to adjust timeout
121 long adjust = System.nanoTime() - startTime;
122 to -= (int) TimeUnit.NANOSECONDS.toMillis(adjust);
123 if (to <= 0) {
124 // timeout expired so no retry
125 numEntries = 0;
126 }
127 }
128 } while (numEntries == IOStatus.INTERRUPTED);
129 assert IOStatus.check(numEntries);
130
131 } finally {
132 end(blocking);
133 }
134 processDeregisterQueue();
135 return processEvents(numEntries, action);
136 }
137
138 /**
139 * Process changes to the interest ops.
140 */
141 private void processUpdateQueue() {
142 assert Thread.holdsLock(this);
143
144 synchronized (updateLock) {
145 SelectionKeyImpl ski;
146 while ((ski = updateKeys.pollFirst()) != null) {
147 if (ski.isValid()) {
148 int fd = ski.getFDVal();
149 // add to fdToKey if needed
150 SelectionKeyImpl previous = fdToKey.putIfAbsent(fd, ski);
151 assert (previous == null) || (previous == ski);
152
153 int newEvents = ski.translateInterestOps();
154 int registeredEvents = ski.registeredEvents();
155 if (newEvents != registeredEvents) {
156 if (newEvents == 0) {
157 // remove from epoll
158 EPoll.ctl(epfd, EPOLL_CTL_DEL, fd, 0);
159 } else {
160 if (registeredEvents == 0) {
161 // add to epoll
162 EPoll.ctl(epfd, EPOLL_CTL_ADD, fd, newEvents);
163 } else {
164 // modify events
165 EPoll.ctl(epfd, EPOLL_CTL_MOD, fd, newEvents);
166 }
167 }
168 ski.registeredEvents(newEvents);
169 }
170 }
171 }
172 }
173 }
174
175 /**
176 * Process the polled events.
177 * If the interrupt fd has been selected, drain it and clear the interrupt.
178 */
179 private int processEvents(int numEntries, Consumer<SelectionKey> action)
180 throws IOException
181 {
182 assert Thread.holdsLock(this);
183
184 boolean interrupted = false;
185 int numKeysUpdated = 0;
186 for (int i=0; i<numEntries; i++) {
187 long event = EPoll.getEvent(pollArrayAddress, i);
188 int fd = EPoll.getDescriptor(event);
189 if (fd == eventfd.efd()) {
190 interrupted = true;
191 } else {
192 SelectionKeyImpl ski = fdToKey.get(fd);
193 if (ski != null) {
194 int rOps = EPoll.getEvents(event);
195 numKeysUpdated += processReadyEvents(rOps, ski, action);
196 }
197 }
198 }
199
200 if (interrupted) {
201 clearInterrupt();
202 }
203
204 return numKeysUpdated;
205 }
206
207 @Override
208 protected void implClose() throws IOException {
209 assert Thread.holdsLock(this);
210
211 // prevent further wakeup
212 synchronized (interruptLock) {
213 interruptTriggered = true;
214 }
215
216 FileDispatcherImpl.closeIntFD(epfd);
217 EPoll.freePollArray(pollArrayAddress);
218
219 eventfd.close();
220 }
221
222 @Override
223 protected void implDereg(SelectionKeyImpl ski) throws IOException {
224 assert !ski.isValid();
225 assert Thread.holdsLock(this);
226
227 int fd = ski.getFDVal();
228 if (fdToKey.remove(fd) != null) {
229 if (ski.registeredEvents() != 0) {
230 EPoll.ctl(epfd, EPOLL_CTL_DEL, fd, 0);
231 ski.registeredEvents(0);
232 }
233 } else {
234 assert ski.registeredEvents() == 0;
235 }
236 }
237
238 @Override
239 public void setEventOps(SelectionKeyImpl ski) {
240 synchronized (updateLock) {
241 updateKeys.addLast(ski);
242 }
243 }
244
245 @Override
246 public Selector wakeup() {
247 synchronized (interruptLock) {
248 if (!interruptTriggered) {
249 try {
250 eventfd.set();
251 } catch (IOException ioe) {
252 throw new InternalError(ioe);
253 }
254 interruptTriggered = true;
255 }
256 }
257 return this;
258 }
259
260 private void clearInterrupt() throws IOException {
261 synchronized (interruptLock) {
262 eventfd.reset();
263 interruptTriggered = false;
264 }
265 }
266 }