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

unsigned long long global = 0x00010000;
#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))

void *thread_set_function(void *arg);
void *thread_read_function(void *arg);

int main(int argc, char **argv)
{
	int ret;
	pthread_t pthread_set;
	pthread_t pthread_read;

	ret = pthread_create(&pthread_set, NULL, thread_set_function, NULL);
	if (ret) {
		fprintf(stderr, "ERROR: fail to create set_thread\n");
		exit(EXIT_FAILURE);
	}
	ret = pthread_create(&pthread_read, NULL, thread_read_function, NULL);
	if (ret) {
		fprintf(stderr, "ERROR: fail to create read_thread\n");
		exit(EXIT_FAILURE);
	}
	pthread_join(pthread_set, NULL);
	pthread_join(pthread_read, NULL);
	return 0;
}

void *thread_set_function(void *arg)
{
	sleep(1);
	while(1) {
		ACCESS_ONCE(global) = 0x0000000000000100;
		ACCESS_ONCE(global) = 0x0010000000000000;
	}
}

void *thread_read_function(void *arg)
{
	if (global)
		printf("no 0 \n");
	while(1) {
		if (global == 0) {
			printf("0 is detected\n");
			exit(0);
		}
	}
}