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
47 static sem_t semaphore;
48
49 static void*
_thread1(void * unused)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
67 static void*
_thread2(void * unused)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
88 static void*
_thread3(void * unused)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
102 typedef void* (*thread_func)(void*);
103
104 static const thread_func thread_routines[] =
105 {
106 &_thread1,
107 &_thread2,
108 &_thread3
109 };
110
main(void)111 int 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