-Start polling on grace period. The returned poll state should be
-queried using `poll_state_synchronize_rcu` to check whether the
-grace period has completed.
+Provides a handle for checking if a new grace period has started
+and completed since the handle was obtained. It returns a
+`struct urcu_gp_poll_state` handle that can be used with
+`poll_state_synchronize_rcu` to check, by polling, if the
+associated grace period has completed.