test_semaphore.c revision e16cb84e2324f05334d18dcf5956f20f44262b62 
1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28#include <pthread.h>
29#include <semaphore.h>
30#include <errno.h>
31#include <stdio.h>
32#include <time.h>
33#include <string.h>
34#include <unistd.h>
35
36/* a simple semaphore test, using three threads
37 *
38 *  a semaphore is initialized with a value of 1
39 *
40 *  Thread 1, 2 and 3 start at the same time
41 *
42 *  Thread 1 takes the semaphore, then sleeps for 2 seconds, then post the semaphore
43 *  Thread 2 sleeps for 1 second, then waits the semaphore, sleeps for 2 seconds, then post the semaphoe
44 *  Thread 3 sleeps 3 seconds, waits for the semaphore
45 */
46
47static  sem_t   semaphore;
48
49static void*
50_thread1( void* unused )
51{
52    printf( "thread 1: waiting for semaphore\n" );
53    if ( sem_wait( &semaphore ) < 0 ) {
54        printf( "thread 1: could not wait for semaphore: %s\n", strerror(errno) );
55        return NULL;
56    }
57    printf( "thread 1: got the semaphore ! sleeping for 2 seconds\n" );
58    sleep( 2 );
59    printf( "thread 1: awake !! posting semaphore\n" );
60    if ( sem_post( &semaphore ) < 0 ) {
61        printf( "thread 2: could not post semaphore: %s\n", strerror(errno) );
62    }
63    printf( "thread 1: quitting\n" );
64    return NULL;
65}
66
67static void*
68_thread2( void* unused )
69{
70    printf( "thread 2: sleeping for 1 second\n" );
71    sleep(1);
72    printf( "thread 2: awake !! waiting for semaphore\n" );
73    if ( sem_wait( &semaphore ) < 0 ) {
74        printf( "thread 2: could not wait for semaphore: %s\n", strerror(errno) );
75        return NULL;
76    }
77    printf( "thread 2: got the semaphore ! sleeping for 2 seconds\n" );
78    sleep( 2 );
79    printf( "thread 2: awake !! posting semaphore\n" );
80    if ( sem_post( &semaphore ) < 0 ) {
81        printf( "thread 2: could not post semaphore: %s\n", strerror(errno) );
82    }
83    printf( "thread 2: quitting\n" );
84    return NULL;
85}
86
87
88static void*
89_thread3( void* unused )
90{
91    printf( "thread 3: sleeping for 3 seconds\n" );
92    sleep(3);
93    printf( "thread 3: awake !! waiting for semaphore\n" );
94    if ( sem_wait( &semaphore ) < 0 ) {
95        printf( "thread 3: could not wait for semaphore: %s\n", strerror(errno) );
96        return NULL;
97    }
98    printf( "thread 3: got semaphore. quitting\n" );
99    return NULL;
100}
101
102typedef void*  (*thread_func)(void*);
103
104static const  thread_func  thread_routines[] =
105{
106    &_thread1,
107    &_thread2,
108    &_thread3
109};
110
111int  main( void )
112{
113    pthread_t   t[3];
114    int         nn;
115
116    if ( sem_init( &semaphore, 0, 1 ) < 0 ) {
117        printf( "could not initialize semaphore: %s\n", strerror(errno) );
118        return -1;
119    }
120
121    for ( nn = 0; nn < 3; nn++ ) {
122        if ( pthread_create( &t[nn], NULL, thread_routines[nn], NULL ) < 0 ) {
123            printf("could not create thread %d: %s\n", nn+1, strerror(errno) );
124            return -2;
125        }
126    }
127    sleep( 5 );
128    return 0;
129}
130