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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

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/*

 * @test

 * @bug     4530538

 * @summary Basic unit test of ThreadInfo.getBlockedCount()

 * @author  Alexei Guibadoulline and Mandy Chung

 * @author  Jaroslav Bachorik

 * @run main ThreadBlockedCount

 */

import java.lang.management.*;

import java.util.concurrent.Phaser;

public class ThreadBlockedCount {

        final static long EXPECTED_BLOCKED_COUNT = 3;

    final static int  DEPTH = 10;

    private static final ThreadMXBean mbean

        = ManagementFactory.getThreadMXBean();

    private static final Object a = new Object();

    private static final Object b = new Object();

    private static final Object c = new Object();

    private static final Object blockedObj1 = new Object();

    private static final Object blockedObj2 = new Object();

    private static final Object blockedObj3 = new Object();

    private static volatile boolean testOk = true;

    private static BlockingThread blocking;

    private static BlockedThread blocked;

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

        // real run

        runTest();

        if (!testOk) {

            throw new RuntimeException("TEST FAILED.");

        }

        System.out.println("Test passed.");

    }

    private static void runTest() throws Exception {

        final Phaser p = new Phaser(2);

        blocking = new BlockingThread(p);

        blocking.start();

        blocked = new BlockedThread(p);

        blocked.start();

        try {

            blocking.join();

            testOk = checkBlocked();

            p.arriveAndAwaitAdvance(); // #5

        } catch (InterruptedException e) {

            System.err.println("Unexpected exception.");

            e.printStackTrace(System.err);

            throw e;

        }

    }

    static class BlockedThread extends Thread {

        private final Phaser p;

        BlockedThread(Phaser p) {

            super("BlockedThread");

            this.p = p;

        }

        public void run() {

            int accumulator = 0;

            p.arriveAndAwaitAdvance(); // #1

            // Enter lock a without blocking

            synchronized (a) {

                p.arriveAndAwaitAdvance(); // #2

                // Block to enter blockedObj1

                // blockedObj1 should be owned by BlockingThread

                synchronized (blockedObj1) {

                    accumulator++; // filler

                }

            }

            // Enter lock a without blocking

            synchronized (b) {

                // wait until BlockingThread holds blockedObj2

                p.arriveAndAwaitAdvance(); // #3

                // Block to enter blockedObj2

                // blockedObj2 should be owned by BlockingThread

                synchronized (blockedObj2) {

                    accumulator++; // filler

                }

            }

            // Enter lock a without blocking

            synchronized (c) {

                // wait until BlockingThread holds blockedObj3

                p.arriveAndAwaitAdvance(); // #4

                // Block to enter blockedObj3

                // blockedObj3 should be owned by BlockingThread

                synchronized (blockedObj3) {

                    accumulator++; // filler

                }

            }

            // wait for the main thread to check the blocked count

            System.out.println("Acquired " + accumulator + " monitors");

            p.arriveAndAwaitAdvance(); // #5

            // ... and we can leave now

        } // run()

    } // BlockedThread

    static class BlockingThread extends Thread {

        private final Phaser p;

        BlockingThread(Phaser p) {

            super("BlockingThread");

            this.p = p;

        }

        private void waitForBlocked() {

            // wait for BlockedThread.

            p.arriveAndAwaitAdvance();

            boolean threadBlocked = false;

            while (!threadBlocked) {

                // give a chance for BlockedThread to really block

                try {

                    Thread.sleep(50);

                } catch (InterruptedException e) {

                    System.err.println("Unexpected exception.");

                    e.printStackTrace(System.err);

                    testOk = false;

                    break;

                }

                ThreadInfo info = mbean.getThreadInfo(blocked.getId());

                threadBlocked = (info.getThreadState() == Thread.State.BLOCKED);

            }

        }

        public void run() {

            p.arriveAndAwaitAdvance(); // #1

            synchronized (blockedObj1) {

                System.out.println("BlockingThread attempts to notify a");

                waitForBlocked(); // #2

            }

            // block until BlockedThread is ready

            synchronized (blockedObj2) {

                System.out.println("BlockingThread attempts to notify b");

                waitForBlocked(); // #3

            }

            // block until BlockedThread is ready

            synchronized (blockedObj3) {

                System.out.println("BlockingThread attempts to notify c");

                waitForBlocked(); // #4

            }

        } // run()

    } // BlockingThread

    private static long getBlockedCount() {

        long count;

        // Check the mbean now

        ThreadInfo ti = mbean.getThreadInfo(blocked.getId());

        count = ti.getBlockedCount();

        return count;

    }

    private static boolean checkBlocked() {

        // wait for the thread stats to be updated for 10 seconds

        long count = -1;

        for (int i = 0; i < 100; i++) {

            count = getBlockedCount();

            if (count >= EXPECTED_BLOCKED_COUNT) {

                return true;

            }

            try {

                Thread.sleep(100);

            } catch (InterruptedException e) {

                System.err.println("Unexpected exception.");

                e.printStackTrace(System.err);

                return false;

            }

        }

        System.err.println("TEST FAILED: Blocked thread has " + count +

                            " blocked counts. Expected at least " +

                            EXPECTED_BLOCKED_COUNT);

        return false;

    }

}