Test cris-crossing

LISA cris-crossing read-side critical sections
(*
 * Result: Sometimes
 *)
{
}
 P0                 | P1            | P2            ;
 f[rcu_read_lock]   | r[once] r1 y  | r[once] r2 z  ;
 w[once] x 1        | w[once] z r1  | f[rmb]        ;
 f[rcu_read_unlock] |               | r[once] r3 x  ;
 f[wmb]             |               |               ;
 w[once] y 1        |               |               ;
Observed
    2:r3=0; 2:r2=1; 1:r1=1;