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