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/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <pthread.h>
#include <semaphore.h>
#include <errno.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <unistd.h>
/* a simple semaphore test, using three threads
*
* a semaphore is initialized with a value of 1
*
* Thread 1, 2 and 3 start at the same time
*
* Thread 1 takes the semaphore, then sleeps for 2 seconds, then post the semaphore
* Thread 2 sleeps for 1 second, then waits the semaphore, sleeps for 2 seconds, then post the semaphoe
* Thread 3 sleeps 3 seconds, waits for the semaphore
*/
static sem_t semaphore;
static void*
_thread1( void* unused )
{
printf( "thread 1: waiting for semaphore\n" );
if ( sem_wait( &semaphore ) < 0 ) {
printf( "thread 1: could not wait for semaphore: %s\n", strerror(errno) );
return NULL;
}
printf( "thread 1: got the semaphore ! sleeping for 2 seconds\n" );
sleep( 2 );
printf( "thread 1: awake !! posting semaphore\n" );
if ( sem_post( &semaphore ) < 0 ) {
printf( "thread 2: could not post semaphore: %s\n", strerror(errno) );
}
printf( "thread 1: quitting\n" );
return NULL;
}
static void*
_thread2( void* unused )
{
printf( "thread 2: sleeping for 1 second\n" );
sleep(1);
printf( "thread 2: awake !! waiting for semaphore\n" );
if ( sem_wait( &semaphore ) < 0 ) {
printf( "thread 2: could not wait for semaphore: %s\n", strerror(errno) );
return NULL;
}
printf( "thread 2: got the semaphore ! sleeping for 2 seconds\n" );
sleep( 2 );
printf( "thread 2: awake !! posting semaphore\n" );
if ( sem_post( &semaphore ) < 0 ) {
printf( "thread 2: could not post semaphore: %s\n", strerror(errno) );
}
printf( "thread 2: quitting\n" );
return NULL;
}
static void*
_thread3( void* unused )
{
printf( "thread 3: sleeping for 3 seconds\n" );
sleep(3);
printf( "thread 3: awake !! waiting for semaphore\n" );
if ( sem_wait( &semaphore ) < 0 ) {
printf( "thread 3: could not wait for semaphore: %s\n", strerror(errno) );
return NULL;
}
printf( "thread 3: got semaphore. quitting\n" );
return NULL;
}
typedef void* (*thread_func)(void*);
static const thread_func thread_routines[] =
{
&_thread1,
&_thread2,
&_thread3
};
int main( void )
{
pthread_t t[3];
int nn;
if ( sem_init( &semaphore, 0, 1 ) < 0 ) {
printf( "could not initialize semaphore: %s\n", strerror(errno) );
return -1;
}
for ( nn = 0; nn < 3; nn++ ) {
if ( pthread_create( &t[nn], NULL, thread_routines[nn], NULL ) < 0 ) {
printf("could not create thread %d: %s\n", nn+1, strerror(errno) );
return -2;
}
}
sleep( 5 );
return 0;
}
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