/*

 * Copyright (c) 2014, Oracle and/or its affiliates. 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.

 *

 * 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 8029516

 * @summary Bash on WatchKey.cancel with a view to causing a crash when

 *    an outstanding I/O operation on directory completes after the

 *    directory has been closed

 */

import java.nio.file.ClosedWatchServiceException;

import java.nio.file.FileSystems;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.WatchKey;

import java.nio.file.WatchService;

import static java.nio.file.StandardWatchEventKinds.*;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.TimeUnit;

public class LotsOfCancels {

    // set to true for any exceptions

    static volatile boolean failed;

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

        // create a bunch of directories. Create two tasks for each directory,

        // one to bash on cancel, the other to poll the events

        ExecutorService pool = Executors.newCachedThreadPool();

        try {

            Path top = Files.createTempDirectory("work");

            top.toFile().deleteOnExit();

            for (int i=1; i<=16; i++) {

                Path dir = Files.createDirectory(top.resolve("dir-" + i));

                WatchService watcher = FileSystems.getDefault().newWatchService();

                pool.submit(() -> handle(dir, watcher));

                pool.submit(() -> poll(watcher));

            }

        } finally {

            pool.shutdown();

        }

        // give thread pool lots of time to terminate

        if (!pool.awaitTermination(5L, TimeUnit.MINUTES))

            throw new RuntimeException("Thread pool did not terminate");

        if (failed)

            throw new RuntimeException("Test failed, see log for details");

    }

    /**

     * Stress the given WatchService, specifically the cancel method, in

     * the given directory. Closes the WatchService when done.

     */

    static void handle(Path dir, WatchService watcher) {

        try {

            try {

                Path file = dir.resolve("anyfile");

                for (int i=0; i<2000; i++) {

                    WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE);

                    Files.createFile(file);

                    Files.delete(file);

                    key.cancel();

                }

            } finally {

                watcher.close();

            }

        } catch (Exception e) {

            e.printStackTrace();

            failed = true;

        }

    }

    /**

     * Polls the given WatchService in a tight loop. This keeps the event

     * queue drained, it also hogs a CPU core which seems necessary to

     * tickle the original bug.

     */

    static void poll(WatchService watcher) {

        try {

            for (;;) {

                WatchKey key = watcher.take();

                if (key != null) {

                    key.pollEvents();

                    key.reset();

                }

            }

        } catch (ClosedWatchServiceException expected) {

            // nothing to do

        } catch (Exception e) {

            e.printStackTrace();

            failed = true;

        }

    }

}