registry[num_readers].tid = id;
/* reference to the TLS of _this_ reader thread. */
registry[num_readers].rcu_reader_qs_gp = &rcu_reader_qs_gp;
registry[num_readers].tid = id;
/* reference to the TLS of _this_ reader thread. */
registry[num_readers].rcu_reader_qs_gp = &rcu_reader_qs_gp;