+ * Must finish waiting for quiescent state for original parity before
+ * committing next rcu_gp_ctr update to memory. Failure to do so could
+ * result in the writer waiting forever while new readers are always
+ * accessing data (no progress). Enforce compiler-order of load
+ * URCU_TLS(rcu_reader).ctr before store to rcu_gp_ctr.
+ */
+ cmm_barrier();
+
+ /*
+ * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
+ * model easier to understand. It does not have a big performance impact
+ * anyway, given this is the write-side.