/*

 * Copyright (c) 2006, 2013, 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 6503247 6574123

 * @summary Test resilience to tryAcquire methods that throw

 * @author Martin Buchholz

 */

import java.util.concurrent.ThreadLocalRandom;

import java.util.concurrent.CyclicBarrier;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.locks.AbstractQueuedLongSynchronizer;

import java.util.concurrent.locks.Condition;

import java.util.concurrent.locks.Lock;

/**

 * This uses a variant of the standard Mutex demo, except with a

 * tryAcquire method that randomly throws various Throwable

 * subclasses.

 */

@SuppressWarnings("serial")

public class FlakyMutex implements Lock {

    static class MyError extends Error {}

    static class MyException extends Exception {}

    static class MyRuntimeException extends RuntimeException {}

    static void checkThrowable(Throwable t) {

        check((t instanceof MyError) ||

              (t instanceof MyException) ||

              (t instanceof MyRuntimeException));

    }

    static void realMain(String[] args) throws Throwable {

        final int nThreads = 3;

        final int iterations = 10_000;

        final CyclicBarrier startingGate = new CyclicBarrier(nThreads);

        final FlakyMutex mutex = new FlakyMutex();

        final ExecutorService es = Executors.newFixedThreadPool(nThreads);

        final Runnable task = () -> {

            try {

                startingGate.await();

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

                    for (;;) {

                        try { mutex.lock(); break; }

                        catch (Throwable t) { checkThrowable(t); }

                    }

                    try { check(! mutex.tryLock()); }

                    catch (Throwable t) { checkThrowable(t); }

                    try { check(! mutex.tryLock(1, TimeUnit.MICROSECONDS)); }

                    catch (Throwable t) { checkThrowable(t); }

                    mutex.unlock();

                }

            } catch (Throwable t) { unexpected(t); }

        };

        for (int i = 0; i < nThreads; i++)

            es.submit(task);

        es.shutdown();

        // Let test harness handle timeout

        check(es.awaitTermination(Long.MAX_VALUE, TimeUnit.DAYS));

    }

    private static class FlakySync extends AbstractQueuedLongSynchronizer {

        private static final long serialVersionUID = -1L;

        public boolean isHeldExclusively() { return getState() == 1; }

        public boolean tryAcquire(long acquires) {

            // Sneak in some tests for queue state

            if (hasQueuedPredecessors())

                check(getFirstQueuedThread() != Thread.currentThread());

            if (getFirstQueuedThread() == Thread.currentThread()) {

                check(hasQueuedThreads());

                check(!hasQueuedPredecessors());

            } else {

                // Might be true, but only transiently

                do {} while (hasQueuedPredecessors() != hasQueuedThreads());

            }

            switch (ThreadLocalRandom.current().nextInt(10)) {

            case 0: throw new MyError();

            case 1: throw new MyRuntimeException();

            case 2: FlakyMutex.<RuntimeException>uncheckedThrow(new MyException());

                // fall through ... NOT!

            default: return compareAndSetState(0, 1);

            }

        }

        public boolean tryRelease(long releases) {

            setState(0);

            return true;

        }

        Condition newCondition() { return new ConditionObject(); }

    }

    private final FlakySync sync = new FlakySync();

    public void lock() { sync.acquire(1); }

    public boolean tryLock() { return sync.tryAcquire(1); }

    public void lockInterruptibly() throws InterruptedException {

        sync.acquireInterruptibly(1);

    }

    public boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException {

        return sync.tryAcquireNanos(1, unit.toNanos(timeout));

    }

    public void unlock() { sync.release(1); }

    public Condition newCondition()   { return sync.newCondition(); }

    public boolean isLocked()         { return sync.isHeldExclusively(); }

    public boolean hasQueuedThreads() { return sync.hasQueuedThreads(); }

    //--------------------- Infrastructure ---------------------------

    static volatile int passed = 0, failed = 0;

    static void pass() {passed++;}

    static void fail() {failed++; Thread.dumpStack();}

    static void fail(String msg) {System.out.println(msg); fail();}

    static void unexpected(Throwable t) {failed++; t.printStackTrace();}

    static void check(boolean cond) {if (cond) pass(); else fail();}

    static void equal(Object x, Object y) {

        if (x == null ? y == null : x.equals(y)) pass();

        else fail(x + " not equal to " + y);}

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

        try {realMain(args);} catch (Throwable t) {unexpected(t);}

        System.out.printf("%nPassed = %d, failed = %d%n%n", passed, failed);

        if (failed > 0) throw new AssertionError("Some tests failed");}

    @SuppressWarnings("unchecked")

    static <T extends Throwable> void uncheckedThrow(Throwable t) throws T {

        throw (T)t; // rely on vacuous cast

    }

}