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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package sun.nio.ch;
import java.io.IOException;
import java.nio.channels.ClosedSelectorException;
import java.nio.channels.Selector;
import java.nio.channels.spi.SelectorProvider;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
import static sun.nio.ch.EPoll.EPOLLIN;
import static sun.nio.ch.EPoll.EPOLL_CTL_ADD;
import static sun.nio.ch.EPoll.EPOLL_CTL_DEL;
import static sun.nio.ch.EPoll.EPOLL_CTL_MOD;
/**
* Linux epoll based Selector implementation
*/
class EPollSelectorImpl extends SelectorImpl {
// maximum number of events to poll in one call to epoll_wait
private static final int NUM_EPOLLEVENTS = Math.min(IOUtil.fdLimit(), 1024);
// epoll file descriptor
private final int epfd;
// address of poll array when polling with epoll_wait
private final long pollArrayAddress;
// file descriptors used for interrupt
private final int fd0;
private final int fd1;
// maps file descriptor to selection key, synchronize on selector
private final Map<Integer, SelectionKeyImpl> fdToKey = new HashMap<>();
// pending new registrations/updates, queued by implRegister and putEventOpos
private final Object updateLock = new Object();
private final Deque<SelectionKeyImpl> newKeys = new ArrayDeque<>();
private final Deque<SelectionKeyImpl> updateKeys = new ArrayDeque<>();
private final Deque<Integer> updateEvents = new ArrayDeque<>();
// interrupt triggering and clearing
private final Object interruptLock = new Object();
private boolean interruptTriggered;
/**
* Package private constructor called by factory method in
* the abstract superclass Selector.
*/
EPollSelectorImpl(SelectorProvider sp) throws IOException {
super(sp);
this.epfd = EPoll.create();
this.pollArrayAddress = EPoll.allocatePollArray(NUM_EPOLLEVENTS);
try {
long fds = IOUtil.makePipe(false);
this.fd0 = (int) (fds >>> 32);
this.fd1 = (int) fds;
} catch (IOException ioe) {
EPoll.freePollArray(pollArrayAddress);
FileDispatcherImpl.closeIntFD(epfd);
throw ioe;
}
// register one end of the socket pair for wakeups
EPoll.ctl(epfd, EPOLL_CTL_ADD, fd0, EPOLLIN);
}
private void ensureOpen() {
if (!isOpen())
throw new ClosedSelectorException();
}
@Override
protected int doSelect(long timeout) throws IOException {
assert Thread.holdsLock(this);
// epoll_wait timeout is int
int to = (int) Math.min(timeout, Integer.MAX_VALUE);
boolean blocking = (to != 0);
boolean timedPoll = (to > 0);
int numEntries;
processUpdateQueue();
processDeregisterQueue();
try {
begin(blocking);
do {
long startTime = timedPoll ? System.nanoTime() : 0;
numEntries = EPoll.wait(epfd, pollArrayAddress, NUM_EPOLLEVENTS, to);
if (numEntries == IOStatus.INTERRUPTED && timedPoll) {
// timed poll interrupted so need to adjust timeout
long adjust = System.nanoTime() - startTime;
to -= TimeUnit.MILLISECONDS.convert(adjust, TimeUnit.NANOSECONDS);
if (to <= 0) {
// timeout expired so no retry
numEntries = 0;
}
}
} while (numEntries == IOStatus.INTERRUPTED);
assert IOStatus.check(numEntries);
} finally {
end(blocking);
}
processDeregisterQueue();
return updateSelectedKeys(numEntries);
}
/**
* Process new registrations and changes to the interest ops.
*/
private void processUpdateQueue() {
assert Thread.holdsLock(this);
synchronized (updateLock) {
SelectionKeyImpl ski;
// new registrations
while ((ski = newKeys.pollFirst()) != null) {
if (ski.isValid()) {
int fd = ski.channel.getFDVal();
SelectionKeyImpl previous = fdToKey.put(fd, ski);
assert previous == null;
assert ski.registeredEvents() == 0;
}
}
// changes to interest ops
assert updateKeys.size() == updateEvents.size();
while ((ski = updateKeys.pollFirst()) != null) {
int newEvents = updateEvents.pollFirst();
int fd = ski.channel.getFDVal();
if (ski.isValid() && fdToKey.containsKey(fd)) {
int registeredEvents = ski.registeredEvents();
if (newEvents != registeredEvents) {
if (newEvents == 0) {
// remove from epoll
EPoll.ctl(epfd, EPOLL_CTL_DEL, fd, 0);
} else {
if (registeredEvents == 0) {
// add to epoll
EPoll.ctl(epfd, EPOLL_CTL_ADD, fd, newEvents);
} else {
// modify events
EPoll.ctl(epfd, EPOLL_CTL_MOD, fd, newEvents);
}
}
ski.registeredEvents(newEvents);
}
}
}
}
}
/**
* Update the keys of file descriptors that were polled and add them to
* the selected-key set.
* If the interrupt fd has been selected, drain it and clear the interrupt.
*/
private int updateSelectedKeys(int numEntries) throws IOException {
assert Thread.holdsLock(this);
assert Thread.holdsLock(nioSelectedKeys());
boolean interrupted = false;
int numKeysUpdated = 0;
for (int i=0; i<numEntries; i++) {
long event = EPoll.getEvent(pollArrayAddress, i);
int fd = EPoll.getDescriptor(event);
if (fd == fd0) {
interrupted = true;
} else {
SelectionKeyImpl ski = fdToKey.get(fd);
if (ski != null) {
int rOps = EPoll.getEvents(event);
if (selectedKeys.contains(ski)) {
if (ski.channel.translateAndSetReadyOps(rOps, ski)) {
numKeysUpdated++;
}
} else {
ski.channel.translateAndSetReadyOps(rOps, ski);
if ((ski.nioReadyOps() & ski.nioInterestOps()) != 0) {
selectedKeys.add(ski);
numKeysUpdated++;
}
}
}
}
}
if (interrupted) {
clearInterrupt();
}
return numKeysUpdated;
}
@Override
protected void implClose() throws IOException {
assert Thread.holdsLock(this);
// prevent further wakeup
synchronized (interruptLock) {
interruptTriggered = true;
}
FileDispatcherImpl.closeIntFD(epfd);
EPoll.freePollArray(pollArrayAddress);
FileDispatcherImpl.closeIntFD(fd0);
FileDispatcherImpl.closeIntFD(fd1);
}
@Override
protected void implRegister(SelectionKeyImpl ski) {
ensureOpen();
synchronized (updateLock) {
newKeys.addLast(ski);
}
}
@Override
protected void implDereg(SelectionKeyImpl ski) throws IOException {
assert !ski.isValid();
assert Thread.holdsLock(this);
int fd = ski.channel.getFDVal();
if (fdToKey.remove(fd) != null) {
if (ski.registeredEvents() != 0) {
EPoll.ctl(epfd, EPOLL_CTL_DEL, fd, 0);
ski.registeredEvents(0);
}
} else {
assert ski.registeredEvents() == 0;
}
}
@Override
public void putEventOps(SelectionKeyImpl ski, int events) {
ensureOpen();
synchronized (updateLock) {
updateEvents.addLast(events); // events first in case adding key fails
updateKeys.addLast(ski);
}
}
@Override
public Selector wakeup() {
synchronized (interruptLock) {
if (!interruptTriggered) {
try {
IOUtil.write1(fd1, (byte)0);
} catch (IOException ioe) {
throw new InternalError(ioe);
}
interruptTriggered = true;
}
}
return this;
}
private void clearInterrupt() throws IOException {
synchronized (interruptLock) {
IOUtil.drain(fd0);
interruptTriggered = false;
}
}
}