Test RCU-idempotency

LISA RCU-idempotency
{
}
 P0                 | P1          | P2                 ;
 f[rcu_read_lock]   | w[once] x 1 | f[rcu_read_lock]   ;
 r[once] r0 x       | f[sync]     | r[once] r0 z       ;
 r[once] r1 y       | w[once] z 1 | w[once] y 1        ;
 f[rcu_read_unlock] |             | f[rcu_read_unlock] ;
Observed
    2:r0=1; 0:r1=1; 0:r0=0;