MP+onceassign+derefonce.litmus

C MP+onceassign+derefonce

(*
 * Result: Never
 *
 * This litmus test demonstrates that rcu_assign_pointer() and
 * rcu_dereference() suffice to ensure that an RCU reader will not see
 * pre-initialization garbage when it traverses an RCU-protected data
 * structure containing a newly inserted element.
 *)

{
p=y;
}

P0(int *x, int **p) // Producer
{
	WRITE_ONCE(*x, 1);
	rcu_assign_pointer(*p, x);
}

P1(int *x, int **p) // Consumer
{
	int *r0;
	int r1;

	rcu_read_lock();
	r0 = rcu_dereference(*p);
	r1 = READ_ONCE(*r0);
	rcu_read_unlock();
}

exists (1:r0=x /\ 1:r1=0) (* Bad outcome. *)