rcu: Remove obsolete callback-invocation statistics for debugfs

The debugfs interface displayed statistics on RCU callback invocation but
this interface has since been removed.  This commit therefore removes the
no-longer-used rcu_data structure's ->n_cbs_invoked and ->n_nocbs_invoked
fields along with their updates.

If this information proves necessary in the future, the corresponding
event traces will be added.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tree.c

@@ -2691,7 +2691,6 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
 	/* Update counts and requeue any remaining callbacks. */
 	rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl);
 	smp_mb(); /* List handling before counting for rcu_barrier(). */
-	rdp->n_cbs_invoked += count;
 	rcu_segcblist_insert_count(&rdp->cblist, &rcl);
 
 	/* Reinstate batch limit if we have worked down the excess. */

kernel/rcu/tree.h

@@ -211,8 +211,6 @@ struct rcu_data {
 					/* different grace periods. */
 	long		qlen_last_fqs_check;
 					/* qlen at last check for QS forcing */
-	unsigned long	n_cbs_invoked;	/* count of RCU cbs invoked. */
-	unsigned long	n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */
 	unsigned long	n_force_qs_snap;
 					/* did other CPU force QS recently? */
 	long		blimit;		/* Upper limit on a processed batch */

kernel/rcu/tree_plugin.h

@@ -2243,7 +2243,6 @@ static int rcu_nocb_kthread(void *arg)
 		smp_mb__before_atomic();  /* _add after CB invocation. */
 		atomic_long_add(-c, &rdp->nocb_q_count);
 		atomic_long_add(-cl, &rdp->nocb_q_count_lazy);
-		rdp->n_nocbs_invoked += c;
 	}
 	return 0;
 }