barrier.hh revision 9983:2cce74fe359e 
1/*
2 * Copyright (c) 2013 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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36 *
37 * Authors: Ali Saidi
38 */
39
40#ifndef __BASE_BARRIER_HH__
41#define __BASE_BARRIER_HH__
42
43#include <condition_variable>
44
45class Barrier
46{
47  private:
48    /// Mutex to protect access to numLeft and generation
49    std::mutex bMutex;
50    /// Condition variable for waiting on barrier
51    std::condition_variable bCond;
52    /// Number of threads we should be waiting for before completing the barrier
53    unsigned numWaiting;
54    /// Generation of this barrier
55    unsigned generation;
56    /// Number of threads remaining for the current generation
57    unsigned numLeft;
58
59  public:
60    Barrier(unsigned _numWaiting)
61        : numWaiting(_numWaiting), generation(0), numLeft(_numWaiting)
62    {}
63
64    bool
65    wait()
66    {
67        std::unique_lock<std::mutex> lock(bMutex);
68        unsigned int gen = generation;
69
70        if (--numLeft == 0) {
71            generation++;
72            numLeft = numWaiting;
73            bCond.notify_all();
74            return true;
75        }
76        while (gen == generation)
77            bCond.wait(lock);
78        return false;
79    }
80};
81
82#endif // __BASE_BARRIER_HH__
83