/*
 *  Copyright (C) NAKAMURA Minoru <nminoru@nminoru.jp>
 */
#include <stdio.h>
#include <sched.h>
#include <pthread.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>

enum {
    THREADS = 2
};

static pthread_t threads[THREADS];
static int semid;

union semun {
    int              val;
    struct semid_ds *buf;
    unsigned short  *array;
    struct seminfo  *__buf;
}; 



static void* routine(void* p)
{
    int id = (int)p;
    int i, j, k;

    for (;;) {
        struct sembuf sb = {0, -1, 0};

        if (semop(semid, &sb, 1)) {
            perror("semop"), exit(2);
        }

        printf("Thread-ID: %d\n", id);
        sched_yield();

        sb.sem_op = 1;
        if (semop(semid, &sb, 1)) {
            perror("semop"), exit(2);
        }
    }
}



int main(int argc, char** argv)
{
    int i;
    union semun arg;
 
    if ((semid = semget(IPC_PRIVATE, 1, 0666)) == 1) {
        perror("semget"), exit(1);
    }

    arg.val = 1;
    if (semctl(semid, 0, SETVAL, arg)) {
        perror("semctl"), exit(1);
    }
    
    for (i=0 ; i<THREADS ; i++) {
        if (pthread_create(&threads[i], NULL, routine, (void*)i)) {
            perror("pthread_create"), exit(1);
        }
    }

    for (i=0 ; i<THREADS ; i++) {
        if (pthread_join(threads[i], NULL)) {
            perror("pthread_join"), exit(1);
        }
    }

    return 0;
}