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  * @compile -source 1.5 SimpleReentrantLockLoops.java
  38  * @run main/timeout=4500 SimpleReentrantLockLoops
  39  * @summary multiple threads using a single lock
  40  */
  41 
  42 import java.util.concurrent.*;
  43 import java.util.concurrent.locks.*;
  44 import java.util.*;
  45 
  46 public final class SimpleReentrantLockLoops {
  47     static final ExecutorService pool = Executors.newCachedThreadPool();
  48     static final LoopHelpers.SimpleRandom rng = new LoopHelpers.SimpleRandom();
  49     static boolean print = false;
  50     static int iters = 1000000;
  51 
  52     public static void main(String[] args) throws Exception {
  53         int maxThreads = 5;
  54         if (args.length > 0)
  55             maxThreads = Integer.parseInt(args[0]);
  56 
  57         print = true;
  58 
  59         int reps = 2;
  60         for (int i = 1; i <= maxThreads; i += (i+1) >>> 1) {
  61             int n = reps;
  62             if (reps > 1) --reps;
  63             while (n-- > 0) {
  64                 System.out.print("Threads: " + i);
  65                 new ReentrantLockLoop(i).test();
  66                 Thread.sleep(100);
  67             }
  68         }
  69         pool.shutdown();
  70         if (! pool.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS))
  71             throw new Error();
  72     }
  73 
  74     static final class ReentrantLockLoop implements Runnable {
  75         private int v = rng.next();
  76         private volatile int result = 17;
  77         private final ReentrantLock lock = new ReentrantLock();
  78         private final LoopHelpers.BarrierTimer timer = new LoopHelpers.BarrierTimer();
  79         private final CyclicBarrier barrier;
  80         private final int nthreads;
  81         ReentrantLockLoop(int nthreads) {
  82             this.nthreads = nthreads;
  83             barrier = new CyclicBarrier(nthreads+1, timer);
  84         }
  85 
  86         final void test() throws Exception {
  87             for (int i = 0; i < nthreads; ++i)
  88                 pool.execute(this);
  89             barrier.await();
  90             barrier.await();
  91             if (print) {
  92                 long time = timer.getTime();
  93                 long tpi = time / ((long)iters * nthreads);
  94                 System.out.print("\t" + LoopHelpers.rightJustify(tpi) + " ns per lock");
  95                 double secs = (double)(time) / 1000000000.0;
  96                 System.out.println("\t " + secs + "s run time");
  97             }
  98 
  99             int r = result;
 100             if (r == 0) // avoid overoptimization
 101                 System.out.println("useless result: " + r);
 102         }
 103 
 104         public final void run() {
 105             try {
 106                 barrier.await();
 107                 int sum = v;
 108                 int x = 0;
 109                 int n = iters;
 110                 do {
 111                     lock.lock();
 112                     try {
 113                         if ((n & 255) == 0)
 114                             v = x = LoopHelpers.compute2(LoopHelpers.compute1(v));
 115                         else
 116                             v = x += ~(v - n);
 117                     }
 118                     finally {
 119                         lock.unlock();
 120                     }
 121                     // Once in a while, do something more expensive
 122                     if ((~n & 255) == 0) {
 123                         sum += LoopHelpers.compute1(LoopHelpers.compute2(x));
 124                     }
 125                     else
 126                         sum += sum ^ x;
 127                 } while (n-- > 0);
 128                 barrier.await();
 129                 result += sum;
 130             }
 131             catch (Exception ie) {
 132                 return;
 133             }
 134         }
 135     }
 136 
 137 }