C auto/C-RW-R+RW-Gr+RW-Ra { } P0(int *x, int *y) { rcu_read_lock(); r1 = READ_ONCE(*y); WRITE_ONCE(*x, 1); rcu_read_unlock(); } P1(int *x, int *z) { r2 = READ_ONCE(*x); synchronize_rcu(); smp_store_release(z, 1); } P2(int *z, int *y) { rcu_read_lock(); r3 = smp_load_acquire(z); WRITE_ONCE(*y, 1); rcu_read_unlock(); } exists (0:r1=1 /\ 1:r2=1 /\ 2:r3=1)