C cmpxchg-fail-ordered-2

(*
 * Result: Never
 *
 * Demonstrate use of smp_mb__after_atomic() to make a failing cmpxchg
 * operation have acquire ordering.
 *)

{}

P0(int *x, int *y)
{
	int r1;

	WRITE_ONCE(*x, 1);
	r1 = cmpxchg(y, 0, 1);
}

P1(int *x, int *y)
{
	int r1;
	int r2;

	r1 = cmpxchg(y, 0, 1);
	smp_mb__after_atomic();
	r2 = READ_ONCE(*x);
}

exists (0:r1=0 /\ 1:r1=1 /\ 1:r2=0)