/*

 * 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.

 *

 * 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/* @test

 * @bug 6693490

 * @summary Pre-close file descriptor may inadvertently get registered with

 *     epoll during close

 */

import java.net.*;

import java.nio.channels.*;

import java.util.concurrent.*;

import java.util.*;

import java.io.IOException;

public class RegAfterPreClose {

    static final int TEST_ITERATIONS = 300;

    static volatile boolean done;

    /**

     * A task that continuously connects to a given address and immediately

     * closes the connection.

     */

    static class Connector implements Runnable {

        private final SocketAddress sa;

        Connector(int port) throws IOException {

            InetAddress lh = InetAddress.getLocalHost();

            this.sa = new InetSocketAddress(lh, port);

        }

        public void run() {

            while (!done) {

                try {

                    SocketChannel.open(sa).close();

                } catch (IOException x) {

                    // back-off as probably resource related

                    try {

                        Thread.sleep(10);

                    } catch (InterruptedException  ignore) { }

                }

            }

        }

    }

    /**

     * A task that closes a channel.

     */

    static class Closer implements Runnable {

        private final Channel channel;

        Closer(Channel sc) {

            this.channel = sc;

        }

        public void run() {

            try {

                channel.close();

            } catch (IOException ignore) { }

        }

    }

    public static void main(String[] args) throws Exception {

        // create listener

        InetSocketAddress isa = new InetSocketAddress(0);

        ServerSocketChannel ssc = ServerSocketChannel.open();

        ssc.socket().bind(isa);

        // register with Selector

        final Selector sel = Selector.open();

        ssc.configureBlocking(false);

        SelectionKey key = ssc.register(sel, SelectionKey.OP_ACCEPT);

        ThreadFactory factory = new ThreadFactory() {

            @Override

            public Thread newThread(Runnable r) {

                Thread t = new Thread(r);

                t.setDaemon(true);

                return t;

            }

        };

        // create Executor that handles tasks that closes channels

        // "asynchronously" - this creates the conditions to provoke the bug.

        ExecutorService executor = Executors.newFixedThreadPool(2, factory);

        // submit task that connects to listener

        executor.execute(new Connector(ssc.socket().getLocalPort()));

        // loop accepting connections until done (or an IOException is thrown)

        int remaining = TEST_ITERATIONS;

        while (remaining > 0) {

            sel.select();

            if (key.isAcceptable()) {

                SocketChannel sc = ssc.accept();

                if (sc != null) {

                    remaining--;

                    sc.configureBlocking(false);

                    sc.register(sel, SelectionKey.OP_READ);

                    executor.execute(new Closer(sc));

                }

            }

            sel.selectedKeys().clear();

        }

        done = true;

        sel.close();

        executor.shutdown();

    }

}