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

sem_t sem;

void *thread (int p) {
	while (1) {
		printf("Thread %d ready\n", p);
		sem_wait(&sem);
		printf("Thread %d inside C.S.\n", p);
		usleep(1000000 * p);
		printf("Thread %d leaving C.S.\n", p);
		sem_post(&sem);
		usleep(1000000);
	}
}

int main () {
	pthread_t thr_id;

	sem_init(&sem, 0, 1);
	
	pthread_create(&thr_id, NULL, thread, (void *) 1);
	pthread_create(&thr_id, NULL, thread, (void *) 2);
	pthread_create(&thr_id, NULL, thread, (void *) 3);
	pthread_create(&thr_id, NULL, thread, (void *) 4);
	pthread_create(&thr_id, NULL, thread, (void *) 5);
	pthread_create(&thr_id, NULL, thread, (void *) 6);
		
	usleep(50000000); //simulation time

	return 0;
}