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* 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.Pipe;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.spi.SelectorProvider;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Consumer;
import jdk.internal.misc.Unsafe;
/**
* A multi-threaded implementation of Selector for Windows.
*
* @author Konstantin Kladko
* @author Mark Reinhold
*/
class WindowsSelectorImpl extends SelectorImpl {
private static final Unsafe unsafe = Unsafe.getUnsafe();
private static int addressSize = unsafe.addressSize();
private static int dependsArch(int value32, int value64) {
return (addressSize == 4) ? value32 : value64;
}
// Initial capacity of the poll array
private final int INIT_CAP = 8;
// Maximum number of sockets for select().
// Should be INIT_CAP times a power of 2
private static final int MAX_SELECTABLE_FDS = 1024;
// Size of FD_SET struct to allocate a buffer for it in SubSelector,
// aligned to 8 bytes on 64-bit:
// struct { unsigned int fd_count; SOCKET fd_array[MAX_SELECTABLE_FDS]; }.
private static final long SIZEOF_FD_SET = dependsArch(
4 + MAX_SELECTABLE_FDS * 4, // SOCKET = unsigned int
4 + MAX_SELECTABLE_FDS * 8 + 4); // SOCKET = unsigned __int64
// The list of SelectableChannels serviced by this Selector. Every mod
// MAX_SELECTABLE_FDS entry is bogus, to align this array with the poll
// array, where the corresponding entry is occupied by the wakeupSocket
private SelectionKeyImpl[] channelArray = new SelectionKeyImpl[INIT_CAP];
// The global native poll array holds file decriptors and event masks
private PollArrayWrapper pollWrapper;
// The number of valid entries in poll array, including entries occupied
// by wakeup socket handle.
private int totalChannels = 1;
// Number of helper threads needed for select. We need one thread per
// each additional set of MAX_SELECTABLE_FDS - 1 channels.
private int threadsCount = 0;
// A list of helper threads for select.
private final List<SelectThread> threads = new ArrayList<SelectThread>();
//Pipe used as a wakeup object.
private final Pipe wakeupPipe;
// File descriptors corresponding to source and sink
private final int wakeupSourceFd, wakeupSinkFd;
// Maps file descriptors to their indices in pollArray
private static final class FdMap extends HashMap<Integer, MapEntry> {
static final long serialVersionUID = 0L;
private MapEntry get(int desc) {
return get(Integer.valueOf(desc));
}
private MapEntry put(SelectionKeyImpl ski) {
return put(Integer.valueOf(ski.getFDVal()), new MapEntry(ski));
}
private MapEntry remove(SelectionKeyImpl ski) {
Integer fd = Integer.valueOf(ski.getFDVal());
MapEntry x = get(fd);
if ((x != null) && (x.ski.channel() == ski.channel()))
return remove(fd);
return null;
}
}
// class for fdMap entries
private static final class MapEntry {
final SelectionKeyImpl ski;
long updateCount = 0;
MapEntry(SelectionKeyImpl ski) {
this.ski = ski;
}
}
private final FdMap fdMap = new FdMap();
// SubSelector for the main thread
private final SubSelector subSelector = new SubSelector();
private long timeout; //timeout for poll
// Lock for interrupt triggering and clearing
private final Object interruptLock = new Object();
private volatile boolean interruptTriggered;
// pending new registrations/updates, queued by implRegister and setEventOps
private final Object updateLock = new Object();
private final Deque<SelectionKeyImpl> newKeys = new ArrayDeque<>();
private final Deque<SelectionKeyImpl> updateKeys = new ArrayDeque<>();
WindowsSelectorImpl(SelectorProvider sp) throws IOException {
super(sp);
pollWrapper = new PollArrayWrapper(INIT_CAP);
wakeupPipe = Pipe.open();
wakeupSourceFd = ((SelChImpl)wakeupPipe.source()).getFDVal();
// Disable the Nagle algorithm so that the wakeup is more immediate
SinkChannelImpl sink = (SinkChannelImpl)wakeupPipe.sink();
(sink.sc).socket().setTcpNoDelay(true);
wakeupSinkFd = ((SelChImpl)sink).getFDVal();
pollWrapper.addWakeupSocket(wakeupSourceFd, 0);
}
private void ensureOpen() {
if (!isOpen())
throw new ClosedSelectorException();
}
@Override
protected int doSelect(Consumer<SelectionKey> action, long timeout)
throws IOException
{
assert Thread.holdsLock(this);
this.timeout = timeout; // set selector timeout
processUpdateQueue();
processDeregisterQueue();
if (interruptTriggered) {
resetWakeupSocket();
return 0;
}
// Calculate number of helper threads needed for poll. If necessary
// threads are created here and start waiting on startLock
adjustThreadsCount();
finishLock.reset(); // reset finishLock
// Wakeup helper threads, waiting on startLock, so they start polling.
// Redundant threads will exit here after wakeup.
startLock.startThreads();
// do polling in the main thread. Main thread is responsible for
// first MAX_SELECTABLE_FDS entries in pollArray.
try {
begin();
try {
subSelector.poll();
} catch (IOException e) {
finishLock.setException(e); // Save this exception
}
// Main thread is out of poll(). Wakeup others and wait for them
if (threads.size() > 0)
finishLock.waitForHelperThreads();
} finally {
end();
}
// Done with poll(). Set wakeupSocket to nonsignaled for the next run.
finishLock.checkForException();
processDeregisterQueue();
int updated = updateSelectedKeys(action);
// Done with poll(). Set wakeupSocket to nonsignaled for the next run.
resetWakeupSocket();
return updated;
}
/**
* 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()) {
growIfNeeded();
channelArray[totalChannels] = ski;
ski.setIndex(totalChannels);
pollWrapper.putEntry(totalChannels, ski);
totalChannels++;
MapEntry previous = fdMap.put(ski);
assert previous == null;
}
}
// changes to interest ops
while ((ski = updateKeys.pollFirst()) != null) {
int events = ski.translateInterestOps();
int fd = ski.getFDVal();
if (ski.isValid() && fdMap.containsKey(fd)) {
int index = ski.getIndex();
assert index >= 0 && index < totalChannels;
pollWrapper.putEventOps(index, events);
}
}
}
}
// Helper threads wait on this lock for the next poll.
private final StartLock startLock = new StartLock();
private final class StartLock {
// A variable which distinguishes the current run of doSelect from the
// previous one. Incrementing runsCounter and notifying threads will
// trigger another round of poll.
private long runsCounter;
// Triggers threads, waiting on this lock to start polling.
private synchronized void startThreads() {
runsCounter++; // next run
notifyAll(); // wake up threads.
}
// This function is called by a helper thread to wait for the
// next round of poll(). It also checks, if this thread became
// redundant. If yes, it returns true, notifying the thread
// that it should exit.
private synchronized boolean waitForStart(SelectThread thread) {
while (true) {
while (runsCounter == thread.lastRun) {
try {
startLock.wait();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
if (thread.isZombie()) { // redundant thread
return true; // will cause run() to exit.
} else {
thread.lastRun = runsCounter; // update lastRun
return false; // will cause run() to poll.
}
}
}
}
// Main thread waits on this lock, until all helper threads are done
// with poll().
private final FinishLock finishLock = new FinishLock();
private final class FinishLock {
// Number of helper threads, that did not finish yet.
private int threadsToFinish;
// IOException which occurred during the last run.
IOException exception = null;
// Called before polling.
private void reset() {
threadsToFinish = threads.size(); // helper threads
}
// Each helper thread invokes this function on finishLock, when
// the thread is done with poll().
private synchronized void threadFinished() {
if (threadsToFinish == threads.size()) { // finished poll() first
// if finished first, wakeup others
wakeup();
}
threadsToFinish--;
if (threadsToFinish == 0) // all helper threads finished poll().
notify(); // notify the main thread
}
// The main thread invokes this function on finishLock to wait
// for helper threads to finish poll().
private synchronized void waitForHelperThreads() {
if (threadsToFinish == threads.size()) {
// no helper threads finished yet. Wakeup them up.
wakeup();
}
while (threadsToFinish != 0) {
try {
finishLock.wait();
} catch (InterruptedException e) {
// Interrupted - set interrupted state.
Thread.currentThread().interrupt();
}
}
}
// sets IOException for this run
private synchronized void setException(IOException e) {
exception = e;
}
// Checks if there was any exception during the last run.
// If yes, throws it
private void checkForException() throws IOException {
if (exception == null)
return;
StringBuffer message = new StringBuffer("An exception occurred" +
" during the execution of select(): \n");
message.append(exception);
message.append('\n');
exception = null;
throw new IOException(message.toString());
}
}
private final class SubSelector {
private final int pollArrayIndex; // starting index in pollArray to poll
// These arrays will hold result of native select().
// The first element of each array is the number of selected sockets.
// Other elements are file descriptors of selected sockets.
private final int[] readFds = new int [MAX_SELECTABLE_FDS + 1];
private final int[] writeFds = new int [MAX_SELECTABLE_FDS + 1];
private final int[] exceptFds = new int [MAX_SELECTABLE_FDS + 1];
// Buffer for readfds, writefds and exceptfds structs that are passed
// to native select().
private final long fdsBuffer = unsafe.allocateMemory(SIZEOF_FD_SET * 3);
private SubSelector() {
this.pollArrayIndex = 0; // main thread
}
private SubSelector(int threadIndex) { // helper threads
this.pollArrayIndex = (threadIndex + 1) * MAX_SELECTABLE_FDS;
}
private int poll() throws IOException{ // poll for the main thread
return poll0(pollWrapper.pollArrayAddress,
Math.min(totalChannels, MAX_SELECTABLE_FDS),
readFds, writeFds, exceptFds, timeout, fdsBuffer);
}
private int poll(int index) throws IOException {
// poll for helper threads
return poll0(pollWrapper.pollArrayAddress +
(pollArrayIndex * PollArrayWrapper.SIZE_POLLFD),
Math.min(MAX_SELECTABLE_FDS,
totalChannels - (index + 1) * MAX_SELECTABLE_FDS),
readFds, writeFds, exceptFds, timeout, fdsBuffer);
}
private native int poll0(long pollAddress, int numfds,
int[] readFds, int[] writeFds, int[] exceptFds, long timeout, long fdsBuffer);
private int processSelectedKeys(long updateCount, Consumer<SelectionKey> action) {
int numKeysUpdated = 0;
numKeysUpdated += processFDSet(updateCount, action, readFds,
Net.POLLIN,
false);
numKeysUpdated += processFDSet(updateCount, action, writeFds,
Net.POLLCONN |
Net.POLLOUT,
false);
numKeysUpdated += processFDSet(updateCount, action, exceptFds,
Net.POLLIN |
Net.POLLCONN |
Net.POLLOUT,
true);
return numKeysUpdated;
}
/**
* updateCount is used to tell if a key has been counted as updated
* in this select operation.
*
* me.updateCount <= updateCount
*/
private int processFDSet(long updateCount,
Consumer<SelectionKey> action,
int[] fds, int rOps,
boolean isExceptFds)
{
int numKeysUpdated = 0;
for (int i = 1; i <= fds[0]; i++) {
int desc = fds[i];
if (desc == wakeupSourceFd) {
synchronized (interruptLock) {
interruptTriggered = true;
}
continue;
}
MapEntry me = fdMap.get(desc);
// If me is null, the key was deregistered in the previous
// processDeregisterQueue.
if (me == null)
continue;
SelectionKeyImpl sk = me.ski;
// The descriptor may be in the exceptfds set because there is
// OOB data queued to the socket. If there is OOB data then it
// is discarded and the key is not added to the selected set.
if (isExceptFds &&
(sk.channel() instanceof SocketChannelImpl) &&
discardUrgentData(desc))
{
continue;
}
int updated = processReadyEvents(rOps, sk, action);
if (updated > 0 && me.updateCount != updateCount) {
me.updateCount = updateCount;
numKeysUpdated++;
}
}
return numKeysUpdated;
}
private void freeFDSetBuffer() {
unsafe.freeMemory(fdsBuffer);
}
}
// Represents a helper thread used for select.
private final class SelectThread extends Thread {
private final int index; // index of this thread
final SubSelector subSelector;
private long lastRun = 0; // last run number
private volatile boolean zombie;
// Creates a new thread
private SelectThread(int i) {
super(null, null, "SelectorHelper", 0, false);
this.index = i;
this.subSelector = new SubSelector(i);
//make sure we wait for next round of poll
this.lastRun = startLock.runsCounter;
}
void makeZombie() {
zombie = true;
}
boolean isZombie() {
return zombie;
}
public void run() {
while (true) { // poll loop
// wait for the start of poll. If this thread has become
// redundant, then exit.
if (startLock.waitForStart(this)) {
subSelector.freeFDSetBuffer();
return;
}
// call poll()
try {
subSelector.poll(index);
} catch (IOException e) {
// Save this exception and let other threads finish.
finishLock.setException(e);
}
// notify main thread, that this thread has finished, and
// wakeup others, if this thread is the first to finish.
finishLock.threadFinished();
}
}
}
// After some channels registered/deregistered, the number of required
// helper threads may have changed. Adjust this number.
private void adjustThreadsCount() {
if (threadsCount > threads.size()) {
// More threads needed. Start more threads.
for (int i = threads.size(); i < threadsCount; i++) {
SelectThread newThread = new SelectThread(i);
threads.add(newThread);
newThread.setDaemon(true);
newThread.start();
}
} else if (threadsCount < threads.size()) {
// Some threads become redundant. Remove them from the threads List.
for (int i = threads.size() - 1 ; i >= threadsCount; i--)
threads.remove(i).makeZombie();
}
}
// Sets Windows wakeup socket to a signaled state.
private void setWakeupSocket() {
setWakeupSocket0(wakeupSinkFd);
}
private native void setWakeupSocket0(int wakeupSinkFd);
// Sets Windows wakeup socket to a non-signaled state.
private void resetWakeupSocket() {
synchronized (interruptLock) {
if (interruptTriggered == false)
return;
resetWakeupSocket0(wakeupSourceFd);
interruptTriggered = false;
}
}
private native void resetWakeupSocket0(int wakeupSourceFd);
private native boolean discardUrgentData(int fd);
// We increment this counter on each call to updateSelectedKeys()
// each entry in SubSelector.fdsMap has a memorized value of
// updateCount. When we increment numKeysUpdated we set updateCount
// for the corresponding entry to its current value. This is used to
// avoid counting the same key more than once - the same key can
// appear in readfds and writefds.
private long updateCount = 0;
// Update ops of the corresponding Channels. Add the ready keys to the
// ready queue.
private int updateSelectedKeys(Consumer<SelectionKey> action) {
updateCount++;
int numKeysUpdated = 0;
numKeysUpdated += subSelector.processSelectedKeys(updateCount, action);
for (SelectThread t: threads) {
numKeysUpdated += t.subSelector.processSelectedKeys(updateCount, action);
}
return numKeysUpdated;
}
@Override
protected void implClose() throws IOException {
assert !isOpen();
assert Thread.holdsLock(this);
// prevent further wakeup
synchronized (interruptLock) {
interruptTriggered = true;
}
wakeupPipe.sink().close();
wakeupPipe.source().close();
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