+ get_call_rcu_data should be called from registered RCU read-side
+ threads. For the QSBR flavor, the caller should be online.
+
+void call_rcu_data_free(struct call_rcu_data *crdp);
+
+ Terminates a call_rcu() helper thread and frees its associated
+ data. The caller must have ensured that this thread is no longer
+ in use, for example, by passing NULL to set_thread_call_rcu_data()
+ and set_cpu_call_rcu_data() as required.
+
+struct call_rcu_data *get_default_call_rcu_data(void);
+
+ Returns the handle for the default call_rcu() helper thread.
+ Creates it if necessary.
+
+struct call_rcu_data *get_cpu_call_rcu_data(int cpu);
+
+ Returns the handle for the current cpu's call_rcu() helper
+ thread, or NULL if the current CPU has no helper thread
+ currently assigned. The call to this function and use of the
+ returned call_rcu_data should be protected by RCU read-side
+ lock.