Test rcu-relacq1

LISA rcu-relacq1
{
}
 P0          | P1                 | P2           ;
 w[once] x 1 | f[rcu_read_lock]   | r[once] r0 y ;
             | r[once] r0 x       | f[rmb]       ;
             | f[rcu_read_unlock] | r[once] r1 x ;
             | f[wmb]             |              ;
             | w[once] y 1        |              ;
Observed
    2:r1=0; 2:r0=1; 1:r0=1;