/*

 * Copyright (c) 1998, 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 4026895

   @summary Ensure that System.runFinalization does not run finalizers in the

            thread that invokes it

 */

public class FinThreads {

    static Thread mainThread;

    static Object lock = new Object();    /* Protects following two fields */

    static Thread finalizerThread = null;

    static Thread finalizedBy = null;

    static class Foo {

        boolean catchFinalizer = false;

        /* Instances are only created in an auxiliary thread, in order to

           guard against stray references from the current thread's stack

         */

            throws InterruptedException

        {

            Thread t = new Thread(new Runnable() {

                public void run() {

                    new Foo(catchFinalizer);

                }});

            t.start();

            t.join();

        }

        public Foo(boolean catchFinalizer) {

            this.catchFinalizer = catchFinalizer;

        }

        public void finalize() throws InterruptedException {

            if (catchFinalizer) {

                boolean gotFinalizer = false;

                synchronized (lock) {

                    if (finalizerThread == null) {

                        finalizerThread = Thread.currentThread();

                        gotFinalizer = true;

                    }

                }

                if (gotFinalizer) {

                    System.err.println("Caught finalizer thread; sleeping...");

                    Thread.sleep(Long.MAX_VALUE);

                }

            } else {

                synchronized (lock) {

                    finalizedBy = Thread.currentThread();

                }

                System.err.println("Test object finalized by " + finalizedBy);

            }

        }

    }

    static void alarm(final Thread sleeper, final long delay)

        throws InterruptedException

    {

        Thread t = new Thread(new Runnable() {

            public void run() {

                try {

                    Thread.sleep(delay);

                    System.err.println("Waking " + sleeper);

                    sleeper.interrupt();

                } catch (InterruptedException x) { }

            }});

        t.setDaemon(true);

        t.start();

    }

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

        mainThread = Thread.currentThread();

        /* Find the finalizer thread and put it to sleep */

        for (;;) {

            Foo.create(true);

            System.gc();

            synchronized (lock) {

                if (finalizerThread != null) break;

            }

        }

        /* Now create a finalizable object and run finalization */

        alarm(finalizerThread, 5000);

        Foo.create(false);

        for (;;) {

            System.gc();

            System.runFinalization();

            synchronized (lock) {

                if (finalizedBy != null) break;

            }

        }

        if (finalizedBy == mainThread)

            throw new Exception("Finalizer run in main thread");

    }

}