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

#define MAX 20
#define THREAD_MAIN 0
#define THREAD_CONTROLLER 1

int count = 0;
pthread_mutex_t mutex;
int scheduler;

void *controlling(void *arg);
int numero_primo(int num);

int main()
{
  printf("Benvenuto nel programma.\n");
  pthread_t controller;
  pthread_mutex_init(&mutex, NULL);
  pthread_create(&controller, NULL, &controlling, NULL);
  while(count < MAX)
    {
      if(scheduler == THREAD_MAIN)
    {
      pthread_mutex_lock(&mutex);
      count ++;
      pthread_mutex_unlock(&mutex);
      scheduler = THREAD_CONTROLLER;
    }
    }
}

void *controlling(void *arg)
{
  while(count <= MAX)
    {
      if(scheduler == THREAD_CONTROLLER)
    {
      pthread_mutex_lock(&mutex);
      if(numero_primo(count))
        {
          printf("%d\n", count);
          fflush(stdout);
        }
      pthread_mutex_unlock(&mutex);
      scheduler = THREAD_MAIN;
    }
    }
}

int numero_primo(int num)
{
  for(int i = 2; i < num; i++)
      if( (num % i) == 0)
    return 0;
  return 1;
}