exemple_semaphores.c

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>


sem_t semaphore;

static void * routine_thread(void * numero_thread);
static int aleatoire(int maximum);

int
main(void) {
    int i;
    pthread_t thread;

    sem_init(& semaphore, 0, 3);
    for (i = 0; i < 10; i++)
        pthread_create(& thread, NULL, routine_thread, (void *) i);
    pthread_exit(NULL);
}

void *
routine_thread(void * numero_thread) {
    int i;
    for (i = 0; i < 2; i++) {
        sem_wait(& semaphore);
        fprintf(stdout, "Thread %d dans portion critique\n",
                (int) numero_thread);
        sleep(aleatoire(4));

        fprintf(stdout, "Thread %d sort de la portion critique\n",
                (int) numero_thread);
        sem_post(& semaphore);
        sleep(aleatoire(4));
    }
    return (NULL);
}

static int
aleatoire(int maximum) {
    double d;
    d = (double) maximum * rand();
    d = d / (RAND_MAX + 1.0);
    return ((int) d);
}