C MP+poonceonces

(*
 * Result: Sometimes
 *
 * Can the counter-intuitive message-passing outcome be prevented with
 * no ordering at all?
 *)

{}

P0(int *x, int *y)
{
	WRITE_ONCE(*x, 1);
	WRITE_ONCE(*y, 1);
}

P1(int *x, int *y)
{
	int r0;
	int r1;

	r0 = READ_ONCE(*y);
	r1 = READ_ONCE(*x);
}

exists (1:r0=1 /\ 1:r1=0)