JDK14/Java14源码在线阅读
/*
* Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012 SAP SE. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* 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).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package sun.nio.ch;
import java.nio.channels.spi.AsynchronousChannelProvider;
import java.io.IOException;
import java.util.HashSet;
import java.util.Iterator;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.RejectedExecutionException;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.ReentrantLock;
import jdk.internal.misc.Unsafe;
/**
* AsynchronousChannelGroup implementation based on the AIX pollset framework.
*/
final class AixPollPort
extends Port
{
private static final Unsafe unsafe = Unsafe.getUnsafe();
static {
IOUtil.load();
init();
}
/**
* struct pollfd {
* int fd;
* short events;
* short revents;
* }
*/
private static final int SIZEOF_POLLFD = eventSize();
private static final int OFFSETOF_EVENTS = eventsOffset();
private static final int OFFSETOF_REVENTS = reventsOffset();
private static final int OFFSETOF_FD = fdOffset();
// opcodes
private static final int PS_ADD = 0x0;
private static final int PS_MOD = 0x1;
private static final int PS_DELETE = 0x2;
// maximum number of events to poll at a time
private static final int MAX_POLL_EVENTS = 512;
// pollset ID
private final int pollset;
// true if port is closed
private boolean closed;
// socket pair used for wakeup
private final int sp[];
// socket pair used to indicate pending pollsetCtl calls
// Background info: pollsetCtl blocks when another thread is in a pollsetPoll call.
private final int ctlSp[];
// number of wakeups pending
private final AtomicInteger wakeupCount = new AtomicInteger();
// address of the poll array passed to pollset_poll
private final long address;
// encapsulates an event for a channel
static class Event {
final PollableChannel channel;
final int events;
Event(PollableChannel channel, int events) {
this.channel = channel;
this.events = events;
}
PollableChannel channel() { return channel; }
int events() { return events; }
}
// queue of events for cases that a polling thread dequeues more than one
// event
private final ArrayBlockingQueue<Event> queue;
private final Event NEED_TO_POLL = new Event(null, 0);
private final Event EXECUTE_TASK_OR_SHUTDOWN = new Event(null, 0);
private final Event CONTINUE_AFTER_CTL_EVENT = new Event(null, 0);
// encapsulates a pollset control event for a file descriptor
static class ControlEvent {
final int fd;
final int events;
final boolean removeOnly;
int error = 0;
ControlEvent(int fd, int events, boolean removeOnly) {
this.fd = fd;
this.events = events;
this.removeOnly = removeOnly;
}
int fd() { return fd; }
int events() { return events; }
boolean removeOnly() { return removeOnly; }
int error() { return error; }
void setError(int error) { this.error = error; }
}
// queue of control events that need to be processed
// (this object is also used for synchronization)
private final HashSet<ControlEvent> controlQueue = new HashSet<ControlEvent>();
// lock used to check whether a poll operation is ongoing
private final ReentrantLock controlLock = new ReentrantLock();
AixPollPort(AsynchronousChannelProvider provider, ThreadPool pool)
throws IOException
{
super(provider, pool);
// open pollset
this.pollset = pollsetCreate();
// create socket pair for wakeup mechanism
int[] sv = new int[2];
try {
socketpair(sv);
// register one end with pollset
pollsetCtl(pollset, PS_ADD, sv[0], Net.POLLIN);
} catch (IOException x) {
pollsetDestroy(pollset);
throw x;
}
this.sp = sv;
// create socket pair for pollset control mechanism
sv = new int[2];
try {
socketpair(sv);
// register one end with pollset
pollsetCtl(pollset, PS_ADD, sv[0], Net.POLLIN);
} catch (IOException x) {
pollsetDestroy(pollset);
throw x;
}
this.ctlSp = sv;
// allocate the poll array
this.address = allocatePollArray(MAX_POLL_EVENTS);
// create the queue and offer the special event to ensure that the first
// threads polls
this.queue = new ArrayBlockingQueue<Event>(MAX_POLL_EVENTS);
this.queue.offer(NEED_TO_POLL);
}
AixPollPort start() {
startThreads(new EventHandlerTask());
return this;
}
/**
* Release all resources
*/
private void implClose() {
synchronized (this) {
if (closed)
return;
closed = true;
}
freePollArray(address);
close0(sp[0]);
close0(sp[1]);
close0(ctlSp[0]);
close0(ctlSp[1]);
pollsetDestroy(pollset);
}
private void wakeup() {
if (wakeupCount.incrementAndGet() == 1) {
// write byte to socketpair to force wakeup
try {
interrupt(sp[1]);
} catch (IOException x) {
throw new AssertionError(x);
}
}
}
@Override
void executeOnHandlerTask(Runnable task) {
synchronized (this) {
if (closed)
throw new RejectedExecutionException();
offerTask(task);
wakeup();
}
}
@Override
void shutdownHandlerTasks() {
/*
* If no tasks are running then just release resources; otherwise
* write to the one end of the socketpair to wakeup any polling threads.
*/
int nThreads = threadCount();
if (nThreads == 0) {
implClose();
} else {
// send interrupt to each thread
while (nThreads-- > 0) {
wakeup();
}
}
}
// invoke by clients to register a file descriptor
@Override
void startPoll(int fd, int events) {
queueControlEvent(new ControlEvent(fd, events, false));
}
// Callback method for implementations that need special handling when fd is removed
@Override
protected void preUnregister(int fd) {
queueControlEvent(new ControlEvent(fd, 0, true));
}
// Add control event into queue and wait for completion.
// In case the control lock is free, this method also tries to apply the control change directly.
private void queueControlEvent(ControlEvent ev) {
// pollsetCtl blocks when a poll call is ongoing. This is very probable.
// Therefore we let the polling thread do the pollsetCtl call.
synchronized (controlQueue) {
controlQueue.add(ev);
// write byte to socketpair to force wakeup
try {
interrupt(ctlSp[1]);
} catch (IOException x) {
throw new AssertionError(x);
}
do {
// Directly empty queue if no poll call is ongoing.
if (controlLock.tryLock()) {
try {
processControlQueue();
} finally {
controlLock.unlock();
}
} else {
try {
// Do not starve in case the polling thread returned before
// we could write to ctlSp[1] but the polling thread did not
// release the control lock until we checked. Therefore, use
// a timed wait for the time being.
controlQueue.wait(100);
} catch (InterruptedException e) {
// ignore exception and try again
}
}
} while (controlQueue.contains(ev));
}
if (ev.error() != 0) {
throw new AssertionError();
}
}
// Process all events currently stored in the control queue.
private void processControlQueue() {
synchronized (controlQueue) {
// On Aix it is only possible to set the event
// bits on the first call of pollsetCtl. Later
// calls only add bits, but cannot remove them.
// Therefore, we always remove the file
// descriptor ignoring the error and then add it.
Iterator<ControlEvent> iter = controlQueue.iterator();
while (iter.hasNext()) {
ControlEvent ev = iter.next();
pollsetCtl(pollset, PS_DELETE, ev.fd(), 0);
if (!ev.removeOnly()) {
ev.setError(pollsetCtl(pollset, PS_MOD, ev.fd(), ev.events()));
}
iter.remove();
}
controlQueue.notifyAll();
}
}
/*
* Task to process events from pollset and dispatch to the channel's
* onEvent handler.
*
* Events are retreived from pollset in batch and offered to a BlockingQueue
* where they are consumed by handler threads. A special "NEED_TO_POLL"
* event is used to signal one consumer to re-poll when all events have
* been consumed.
*/
private class EventHandlerTask implements Runnable {
private Event poll() throws IOException {
try {
for (;;) {
int n;
controlLock.lock();
try {
n = pollsetPoll(pollset, address, MAX_POLL_EVENTS);
} finally {
controlLock.unlock();
}
/*
* 'n' events have been read. Here we map them to their
* corresponding channel in batch and queue n-1 so that
* they can be handled by other handler threads. The last
* event is handled by this thread (and so is not queued).
*/
fdToChannelLock.readLock().lock();
try {
while (n-- > 0) {
long eventAddress = getEvent(address, n);
int fd = getDescriptor(eventAddress);
// To emulate one shot semantic we need to remove
// the file descriptor here.
if (fd != sp[0] && fd != ctlSp[0]) {
synchronized (controlQueue) {
pollsetCtl(pollset, PS_DELETE, fd, 0);
}
}
// wakeup
if (fd == sp[0]) {
if (wakeupCount.decrementAndGet() == 0) {
// no more wakeups so drain pipe
drain1(sp[0]);
}
// queue special event if there are more events
// to handle.
if (n > 0) {
queue.offer(EXECUTE_TASK_OR_SHUTDOWN);
continue;
}
return EXECUTE_TASK_OR_SHUTDOWN;
}
// wakeup to process control event
if (fd == ctlSp[0]) {
synchronized (controlQueue) {
drain1(ctlSp[0]);
processControlQueue();
}
if (n > 0) {
continue;
}
return CONTINUE_AFTER_CTL_EVENT;
}
PollableChannel channel = fdToChannel.get(fd);
if (channel != null) {
int events = getRevents(eventAddress);
Event ev = new Event(channel, events);
// n-1 events are queued; This thread handles
// the last one except for the wakeup
if (n > 0) {
queue.offer(ev);
} else {
return ev;
}
}
}
} finally {
fdToChannelLock.readLock().unlock();
}
}
} finally {
// to ensure that some thread will poll when all events have
// been consumed
queue.offer(NEED_TO_POLL);
}
}
public void run() {
Invoker.GroupAndInvokeCount myGroupAndInvokeCount =
Invoker.getGroupAndInvokeCount();
final boolean isPooledThread = (myGroupAndInvokeCount != null);
boolean replaceMe = false;
Event ev;
try {
for (;;) {
// reset invoke count
if (isPooledThread)
myGroupAndInvokeCount.resetInvokeCount();
try {
replaceMe = false;
ev = queue.take();
// no events and this thread has been "selected" to
// poll for more.
if (ev == NEED_TO_POLL) {
try {
ev = poll();
} catch (IOException x) {
x.printStackTrace();
return;
}
}
} catch (InterruptedException x) {
continue;
}
// contine after we processed a control event
if (ev == CONTINUE_AFTER_CTL_EVENT) {
continue;
}
// handle wakeup to execute task or shutdown
if (ev == EXECUTE_TASK_OR_SHUTDOWN) {
Runnable task = pollTask();
if (task == null) {
// shutdown request
return;
}
// run task (may throw error/exception)
replaceMe = true;
task.run();
continue;
}
// process event
try {
ev.channel().onEvent(ev.events(), isPooledThread);
} catch (Error x) {
replaceMe = true; throw x;
} catch (RuntimeException x) {
replaceMe = true; throw x;
}
}
} finally {
// last handler to exit when shutdown releases resources
int remaining = threadExit(this, replaceMe);
if (remaining == 0 && isShutdown()) {
implClose();
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