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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 *
 * 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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/*
 * @test HandshakeSuspendExitTest
 * @summary This test tries to stress the handshakes with new and exiting threads while suspending them.
 * @library /testlibrary /test/lib
 * @build HandshakeSuspendExitTest
 * @run main/othervm -XX:+UnlockDiagnosticVMOptions -XX:GuaranteedSafepointInterval=1 -XX:+HandshakeALot HandshakeSuspendExitTest
 */

import jvmti.JVMTIUtils;

public class HandshakeSuspendExitTest  implements Runnable {

    static Thread[] _suspend_threads = new Thread[16];
    static volatile boolean _exit_now = false;
    static java.util.concurrent.Semaphore _sem = new java.util.concurrent.Semaphore(0);

    static void suspendThread(Thread t) {
        try {
            JVMTIUtils.suspendThread(t);
        } catch (JVMTIUtils.JvmtiException e) {
            if (e.getCode() != JVMTIUtils.JVMTI_ERROR_THREAD_SUSPENDED
                && e.getCode() != JVMTIUtils.JVMTI_ERROR_THREAD_NOT_ALIVE) {
                throw e;
            }
        }
    }

    static void resumeThread(Thread t) {
        try {
            JVMTIUtils.resumeThread(t);
        } catch (JVMTIUtils.JvmtiException e) {
            if (e.getCode() != JVMTIUtils.JVMTI_ERROR_THREAD_NOT_SUSPENDED
                && e.getCode() != JVMTIUtils.JVMTI_ERROR_THREAD_NOT_ALIVE) {
                throw e;
            }
        }
    }

    @Override
    public void run() {
        _sem.release();
        while (!_exit_now) {
            // Leave last 2 threads running.
            for (int i = 0; i < _suspend_threads.length - 2; i++) {
                if (Thread.currentThread() != _suspend_threads[i]) {
                    suspendThread(_suspend_threads[i]);
                    resumeThread(_suspend_threads[i]);
                }
            }
        }
        _sem.release();
    }


    public static void main(String... args) throws Exception {
        HandshakeSuspendExitTest test = new HandshakeSuspendExitTest();
        // Fire-up suspend threads.
        for (int i = 0; i < _suspend_threads.length; i++) {
            _suspend_threads[i] = new Thread(test);
        }
        for (int i = 0; i < _suspend_threads.length; i++) {
            _suspend_threads[i].start();
        }
        // Wait for all suspend-threads to start looping.
        for (Thread thr : _suspend_threads) {
            _sem.acquire();
        }

        // Fire-up exiting threads.
        Thread[] exit_threads = new Thread[128];
        for (int i = 0; i < exit_threads.length; i++) {
            exit_threads[i] = new Thread();
            exit_threads[i].start();
        }

        // Try to suspend them.
        for (Thread thr : exit_threads) {
            suspendThread(thr);
        }
        for (Thread thr : exit_threads) {
            resumeThread(thr);
        }

        // Start exit and join.
        _exit_now = true;
        int waiting = _suspend_threads.length;
        do {
            // Resume any worker threads that might have suspended
            // each other at exactly the same time so they can see
            // _exit_now and check in via the semaphore.
            for (Thread thr : _suspend_threads) {
                resumeThread(thr);
            }
            while (_sem.tryAcquire()) {
                --waiting;
            }
        } while (waiting > 0);
        for (Thread thr : _suspend_threads) {
            thr.join();
        }
        for (Thread thr : exit_threads) {
            thr.join();
        }
    }
}
