C auto/C-RR-R+WW-G { } P0(int *x0, int *x1) { rcu_read_lock(); r1 = READ_ONCE(*x); r2 = READ_ONCE(*y); rcu_read_unlock(); } P1(int *x0, int *x1) { WRITE_ONCE(*y, 1); synchronize_rcu(); WRITE_ONCE(*x, 1); } exists (0:r1=1 /\ 0:r2=0)