C-thread allocate_PID

int
allocate_PID(int t_id)
{
    int next_pid;
    int i;
    int pid = -1;

    pthread_mutex_lock(&mutex);
    //Test for available resources
    if (S<=0) {
        goto end;
    }

    for (i =0;i<PID_MAX-PID_MIN+1;i++) {
        if (pid_map[i] == 0){
            S--;
            printf("Thread number %d got PID %d S=%d\n", t_id, i+PID_MIN, S);
            pid_map[i] = 1;
            next_pid   = i;
            pid        = next_pid + PID_MIN;
            goto end;
        }
    }
    //for debug purposes:
    //if a thread will pass mutex and S-semaphore
    //but won't find a PID then -999 will be returned
    pid = -999;
end:
    pthread_mutex_unlock(&mutex);
    return pid;
}