test_pthread_cond.cpp revision 12751 
1/*
2  * Copyright (c) 2018, Cornell University
3  * All rights reserved.
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5  * Redistribution and use in source and binary forms, with or
6  * without modification, are permitted provided that the following
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10  * notice, this list of conditions and the following disclaimer.
11  *
12  * Redistributions in binary form must reproduce the above
13  * copyright notice, this list of conditions and the following
14  * disclaimer in the documentation and/or other materials provided
15  * with the distribution.
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18  * contributors may be used to endorse or promote products derived
19  * from this software without specific prior written permission.
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21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
22  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
23  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
24  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
25  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
26  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
27  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
28  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
29  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
30  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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33  * POSSIBILITY OF SUCH DAMAGE.
34  *
35  * Author: Moyang Wang
36  */
37
38#include <pthread.h>
39
40#include <cstdlib>
41#include <iostream>
42#include <mutex>
43#include <vector>
44
45//------------------------------------------------------------------------
46// Test pthread_cond
47//------------------------------------------------------------------------
48// The master thread creates N threads, each of which waits on a
49// condition variable of a signal to start. The master thread then set
50// the signal and notifies all other threads to begin.
51
52#define MAX_N_WORKER_THREADS 10
53
54pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
55pthread_cond_t  cv = PTHREAD_COND_INITIALIZER;
56
57bool ready = false;
58
59void* print_id( void* arg_vptr )
60{
61    pthread_mutex_lock( &mutex );
62    long id = (long)arg_vptr;
63
64    while (!ready) {
65        pthread_cond_wait( &cv, &mutex );
66    }
67    // ...
68    std::cout << "thread " << id << '\n';
69
70    pthread_mutex_unlock( &mutex );
71
72    return nullptr;
73}
74
75void go()
76{
77    pthread_mutex_lock( &mutex );
78    ready = true;
79    pthread_cond_broadcast( &cv );
80    pthread_mutex_unlock( &mutex );
81}
82
83int main( int argc, char* argv[] )
84{
85    size_t n_worker_threads = 0;
86
87    std::vector< pthread_t > threads( MAX_N_WORKER_THREADS );
88
89    int ret = 0;
90    for ( size_t i = 0; i < MAX_N_WORKER_THREADS; i++ ){
91        ret = pthread_create( &threads[i], nullptr, print_id, (void*)i );
92        if (ret != 0) {
93            break;
94        }
95        n_worker_threads++;
96    }
97
98    std::cout << n_worker_threads << " threads ready to race...\n";
99
100    go();
101
102    for ( size_t i = 1; i < n_worker_threads; i++ ) {
103        pthread_join( threads[i], nullptr );
104    }
105
106    if (n_worker_threads < 1) {
107        return EXIT_FAILURE;
108    }
109
110    return EXIT_SUCCESS;
111}
112