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 }
--- EOF ---