1/*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 */
22
23/*
24 * This file is available under and governed by the GNU General Public
25 * License version 2 only, as published by the Free Software Foundation.
26 * However, the following notice accompanied the original version of this
27 * file:
28 *
29 * Written by Doug Lea with assistance from members of JCP JSR-166
30 * Expert Group and released to the public domain, as explained at
31 * http://creativecommons.org/publicdomain/zero/1.0/
32 */
33
34/*
35 * @test
36 * @bug 4486658
37 * @summary multiple threads using a single lock
38 * @library /lib/testlibrary/
39 */
40
41import static java.util.concurrent.TimeUnit.MILLISECONDS;
42
43import java.util.concurrent.CyclicBarrier;
44import java.util.concurrent.ExecutorService;
45import java.util.concurrent.Executors;
46import java.util.concurrent.locks.ReentrantLock;
47import java.util.concurrent.ThreadLocalRandom;
48import jdk.testlibrary.Utils;
49
50public final class SimpleReentrantLockLoops {
51    static final long LONG_DELAY_MS = Utils.adjustTimeout(10_000);
52    static final ExecutorService pool = Executors.newCachedThreadPool();
53    static boolean print = false;
54    static int iters = 100_000;
55
56    public static void main(String[] args) throws Exception {
57        int maxThreads = 5;
58        if (args.length > 0)
59            maxThreads = Integer.parseInt(args[0]);
60
61        print = true;
62
63        int reps = 2;
64        for (int i = 1; i <= maxThreads; i += (i+1) >>> 1) {
65            int n = reps;
66            if (reps > 1) --reps;
67            while (n-- > 0) {
68                System.out.print("Threads: " + i);
69                new ReentrantLockLoop(i).test();
70            }
71        }
72        pool.shutdown();
73        if (! pool.awaitTermination(LONG_DELAY_MS, MILLISECONDS))
74            throw new Error();
75    }
76
77    static final class ReentrantLockLoop implements Runnable {
78        private int v = ThreadLocalRandom.current().nextInt();
79        private volatile int result = 17;
80        private final ReentrantLock lock = new ReentrantLock();
81        private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
82        private final CyclicBarrier barrier;
83        private final int nthreads;
84        ReentrantLockLoop(int nthreads) {
85            this.nthreads = nthreads;
86            barrier = new CyclicBarrier(nthreads+1, timer);
87        }
88
89        final void test() throws Exception {
90            for (int i = 0; i < nthreads; ++i)
91                pool.execute(this);
92            barrier.await();
93            barrier.await();
94            if (print) {
95                long time = timer.getTime();
96                long tpi = time / ((long)iters * nthreads);
97                System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock");
98                double secs = (double)(time) / 1000000000.0;
99                System.out.println("\t " + secs + "s run time");
100            }
101
102            int r = result;
103            if (r == 0) // avoid overoptimization
104                System.out.println("useless result: " + r);
105        }
106
107        public final void run() {
108            try {
109                barrier.await();
110                int sum = v;
111                int x = 0;
112                int n = iters;
113                do {
114                    lock.lock();
115                    try {
116                        if ((n & 255) == 0)
117                            v = x = LoopHelpers.compute2(LoopHelpers.compute1(v));
118                        else
119                            v = x += ~(v - n);
120                    }
121                    finally {
122                        lock.unlock();
123                    }
124                    // Once in a while, do something more expensive
125                    if ((~n & 255) == 0) {
126                        sum += LoopHelpers.compute1(LoopHelpers.compute2(x));
127                    }
128                    else
129                        sum += sum ^ x;
130                } while (n-- > 0);
131                barrier.await();
132                result += sum;
133            }
134            catch (Exception ex) {
135                return;
136            }
137        }
138    }
139
140}
141