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/*
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* Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.nio.ch;
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import java.nio.channels.spi.AsynchronousChannelProvider;
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import java.io.IOException;
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import java.util.concurrent.ArrayBlockingQueue;
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import java.util.concurrent.RejectedExecutionException;
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import java.util.concurrent.atomic.AtomicInteger;
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import static sun.nio.ch.KQueue.*;
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/**
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* AsynchronousChannelGroup implementation based on the BSD kqueue facility.
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*/
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final class KQueuePort
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extends Port
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{
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// maximum number of events to poll at a time
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private static final int MAX_KEVENTS_TO_POLL = 512;
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// kqueue file descriptor
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private final int kqfd;
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// true if kqueue closed
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private boolean closed;
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// socket pair used for wakeup
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private final int sp[];
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// number of wakeups pending
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private final AtomicInteger wakeupCount = new AtomicInteger();
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// address of the poll array passed to kqueue_wait
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private final long address;
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// encapsulates an event for a channel
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static class Event {
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final PollableChannel channel;
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final int events;
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Event(PollableChannel channel, int events) {
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this.channel = channel;
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this.events = events;
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}
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PollableChannel channel() { return channel; }
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int events() { return events; }
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}
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// queue of events for cases that a polling thread dequeues more than one
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// event
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private final ArrayBlockingQueue<Event> queue;
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private final Event NEED_TO_POLL = new Event(null, 0);
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private final Event EXECUTE_TASK_OR_SHUTDOWN = new Event(null, 0);
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KQueuePort(AsynchronousChannelProvider provider, ThreadPool pool)
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throws IOException
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{
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super(provider, pool);
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// open kqueue
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this.kqfd = kqueue();
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// create socket pair for wakeup mechanism
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int[] sv = new int[2];
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try {
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socketpair(sv);
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// register one end with kqueue
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keventRegister(kqfd, sv[0], EVFILT_READ, EV_ADD);
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} catch (IOException x) {
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close0(kqfd);
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throw x;
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}
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this.sp = sv;
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// allocate the poll array
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this.address = allocatePollArray(MAX_KEVENTS_TO_POLL);
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// create the queue and offer the special event to ensure that the first
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// threads polls
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this.queue = new ArrayBlockingQueue<Event>(MAX_KEVENTS_TO_POLL);
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this.queue.offer(NEED_TO_POLL);
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}
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KQueuePort start() {
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startThreads(new EventHandlerTask());
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return this;
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}
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/**
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* Release all resources
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*/
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private void implClose() {
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synchronized (this) {
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if (closed)
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return;
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closed = true;
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}
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freePollArray(address);
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close0(sp[0]);
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close0(sp[1]);
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close0(kqfd);
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}
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private void wakeup() {
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if (wakeupCount.incrementAndGet() == 1) {
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// write byte to socketpair to force wakeup
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try {
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interrupt(sp[1]);
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} catch (IOException x) {
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throw new AssertionError(x);
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}
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}
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}
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@Override
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void executeOnHandlerTask(Runnable task) {
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synchronized (this) {
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if (closed)
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throw new RejectedExecutionException();
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offerTask(task);
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wakeup();
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}
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}
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@Override
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void shutdownHandlerTasks() {
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/*
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* If no tasks are running then just release resources; otherwise
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* write to the one end of the socketpair to wakeup any polling threads.
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*/
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int nThreads = threadCount();
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if (nThreads == 0) {
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implClose();
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} else {
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// send interrupt to each thread
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while (nThreads-- > 0) {
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wakeup();
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}
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}
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}
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// invoked by clients to register a file descriptor
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@Override
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void startPoll(int fd, int events) {
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// We use a separate filter for read and write events.
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// TBD: Measure cost of EV_ONESHOT vs. EV_CLEAR, either will do here.
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int err = 0;
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int flags = (EV_ADD|EV_ONESHOT);
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if ((events & Port.POLLIN) > 0)
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err = keventRegister(kqfd, fd, EVFILT_READ, flags);
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if (err == 0 && (events & Port.POLLOUT) > 0)
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err = keventRegister(kqfd, fd, EVFILT_WRITE, flags);
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if (err != 0)
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throw new InternalError("kevent failed: " + err); // should not happen
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}
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/*
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* Task to process events from kqueue and dispatch to the channel's
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* onEvent handler.
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*
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* Events are retreived from kqueue in batch and offered to a BlockingQueue
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* where they are consumed by handler threads. A special "NEED_TO_POLL"
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* event is used to signal one consumer to re-poll when all events have
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* been consumed.
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*/
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private class EventHandlerTask implements Runnable {
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private Event poll() throws IOException {
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try {
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for (;;) {
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int n = keventPoll(kqfd, address, MAX_KEVENTS_TO_POLL);
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/*
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* 'n' events have been read. Here we map them to their
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* corresponding channel in batch and queue n-1 so that
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* they can be handled by other handler threads. The last
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* event is handled by this thread (and so is not queued).
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*/
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fdToChannelLock.readLock().lock();
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try {
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while (n-- > 0) {
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long keventAddress = getEvent(address, n);
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int fd = getDescriptor(keventAddress);
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// wakeup
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if (fd == sp[0]) {
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if (wakeupCount.decrementAndGet() == 0) {
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// no more wakeups so drain pipe
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drain1(sp[0]);
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}
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// queue special event if there are more events
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// to handle.
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if (n > 0) {
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queue.offer(EXECUTE_TASK_OR_SHUTDOWN);
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continue;
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}
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return EXECUTE_TASK_OR_SHUTDOWN;
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}
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PollableChannel channel = fdToChannel.get(fd);
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if (channel != null) {
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int filter = getFilter(keventAddress);
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int events = 0;
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if (filter == EVFILT_READ)
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events = Port.POLLIN;
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else if (filter == EVFILT_WRITE)
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events = Port.POLLOUT;
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Event ev = new Event(channel, events);
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// n-1 events are queued; This thread handles
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// the last one except for the wakeup
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if (n > 0) {
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queue.offer(ev);
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} else {
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return ev;
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}
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}
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}
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} finally {
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fdToChannelLock.readLock().unlock();
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}
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}
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} finally {
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// to ensure that some thread will poll when all events have
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// been consumed
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queue.offer(NEED_TO_POLL);
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}
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}
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public void run() {
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Invoker.GroupAndInvokeCount myGroupAndInvokeCount =
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Invoker.getGroupAndInvokeCount();
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final boolean isPooledThread = (myGroupAndInvokeCount != null);
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boolean replaceMe = false;
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Event ev;
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try {
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for (;;) {
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// reset invoke count
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if (isPooledThread)
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myGroupAndInvokeCount.resetInvokeCount();
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try {
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replaceMe = false;
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ev = queue.take();
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// no events and this thread has been "selected" to
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// poll for more.
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if (ev == NEED_TO_POLL) {
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try {
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ev = poll();
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} catch (IOException x) {
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x.printStackTrace();
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return;
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}
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}
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} catch (InterruptedException x) {
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continue;
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}
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// handle wakeup to execute task or shutdown
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if (ev == EXECUTE_TASK_OR_SHUTDOWN) {
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Runnable task = pollTask();
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if (task == null) {
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// shutdown request
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return;
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}
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// run task (may throw error/exception)
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replaceMe = true;
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task.run();
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continue;
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}
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// process event
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try {
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ev.channel().onEvent(ev.events(), isPooledThread);
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} catch (Error x) {
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replaceMe = true; throw x;
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} catch (RuntimeException x) {
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replaceMe = true; throw x;
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}
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}
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} finally {
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// last handler to exit when shutdown releases resources
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int remaining = threadExit(this, replaceMe);
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if (remaining == 0 && isShutdown()) {
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implClose();
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}
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}
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}
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}
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// -- Native methods --
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private static native void socketpair(int[] sv) throws IOException;
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private static native void interrupt(int fd) throws IOException;
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private static native void drain1(int fd) throws IOException;
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private static native void close0(int fd);
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static {
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Util.load();
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}
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}
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