/*
 * Dekker's critical section algorithm, implemented with fences.
 *
 * URL:
 *   http://www.justsoftwaresolutions.co.uk/threading/
 */

#include <atomic>
#include <threads.h>

#include "librace.h"

std::atomic<bool> flag0, flag1;
std::atomic<int> turn;
std::atomic<int> var;

void p0() {
	flag0.store(true);

	while (flag1.load()) {
		if (turn.load() !=0)
		{
			flag0.store(false);
			while (turn.load() != 0) {
				thrd_yield();
			}
			flag0.store(true);
		} else
			thrd_yield();
	}

	// critical section
	var.store(1);

	turn.store(1);
	flag0.store(false);
}

void p1() {
	flag1.store(true);

	while (flag0.load()) {
		if (turn.load() != 1) {
			flag1.store(false);
			while (turn.load() != 1) {
				thrd_yield();
			}
			flag1.store(true);
		} else
			thrd_yield();
	}
	
	// critical section
	var.store(2);

	turn.store(0);
	flag1.store(false);
}

void p0l(void *arg) {
	int i;
	for(i=0;i<PROBLEMSIZE;i++)
		p0();
}

void p1l(void *arg) {
	int i;
	for(i=0;i<PROBLEMSIZE;i++)
		p1();
}

int user_main(int argc, char **argv)
{
	thrd_t a, b;

	flag0 = false;
	flag1 = false;
	turn = 0;
	var=0;
	
	thrd_create(&a, p0l, NULL);
	thrd_create(&b, p1l, NULL);

	thrd_join(a);
	thrd_join(b);

	return 0;
}