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

static sem_t sem[2];
static long count[2];

static void *func(void *arg)
{
	long my_id = (long) arg;

	for (;;) {
		sem_wait(&sem[my_id]);
		count[my_id]++;
		sem_post(&sem[1-my_id]);
	}

	return NULL;
}

int main(void)
{
	void *ret;
	pthread_t t1, t2;

	sem_init(&sem[0], 0, 1);
	sem_init(&sem[1], 0, 0);

	pthread_create(&t1, NULL, func, (void*) 0);
	pthread_create(&t2, NULL, func, (void*) 1);

	sleep(2);

	pthread_cancel(t1);
	pthread_cancel(t2);

	pthread_join(t1, &ret);
	pthread_join(t2, &ret);

	printf("count=%ld\n", count[0] + count[1]);

	return 0;
}