xref: /kernel/linux/linux-6.6/Documentation/litmus-tests/rcu/RCU+sync+read.litmus

C RCU+sync+read

(*
 * Result: Never
 *
 * This litmus test demonstrates that after a grace period, an RCU updater always
 * sees all stores done in prior RCU read-side critical sections. Such
 * read-side critical sections would have ended before the grace period ended.
 *
 * This is one implication of the RCU grace-period guarantee, which says (among
 * other things) that an RCU read-side critical section cannot span a grace period.
 *)

{
int x = 0;
int y = 0;
}

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

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

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

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