Test ISA2+rl-o-o-rul+rl-o-o-rul+o-srcu-o

LISA ISA2+rl-o-o-rul+rl-o-o-rul+o-srcu-o
(* Allowed: More RCU RS CSes than GPs. *)
{
a = 1;
x = 2;
c = 0;
}
 P0                 | P1                 | P2            ;
 f[rcu_read_lock]   | f[rcu_read_lock]   |               ;
 w[once] a 3        | r[once] r1 x       | r[once] r3 c  ;
                    |                    | f[sync]       ;
 w[once] x 4        | w[once] c 1        | r[once] r2 a  ;
 f[rcu_read_unlock] | f[rcu_read_unlock] |               ;
Observed
    2:r3=1; 2:r2=1; 1:r1=4;