rcu: Open-code the rcu_cblist_n_cbs() function

Because the rcu_cblist_n_cbs() just samples the ->len counter, and
because the rcu_cblist structure is quite straightforward, it makes
sense to open-code rcu_cblist_n_cbs(p) as p->len, cutting out a level
of indirection.  This commit makes this change.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>

kernel/rcu/rcu_segcblist.h

@@ -22,12 +22,6 @@
 
 #include <linux/rcu_segcblist.h>
 
-/* Return number of callbacks in simple callback list. */
-static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp)
-{
-	return rclp->len;
-}
-
 /* Return number of lazy callbacks in simple callback list. */
 static inline long rcu_cblist_n_lazy_cbs(struct rcu_cblist *rclp)
 {

kernel/rcu/tree.c

@@ -2633,9 +2633,8 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags)
 		return;
 
 	/* Do the accounting first. */
-	rdp->n_cbs_adopted += rcu_cblist_n_cbs(&rsp->orphan_done);
-	if (rcu_cblist_n_lazy_cbs(&rsp->orphan_done) !=
-	    rcu_cblist_n_cbs(&rsp->orphan_done))
+	rdp->n_cbs_adopted += rsp->orphan_done.len;
+	if (rcu_cblist_n_lazy_cbs(&rsp->orphan_done) != rsp->orphan_done.len)
 		rcu_idle_count_callbacks_posted();
 	rcu_segcblist_insert_count(&rdp->cblist, &rsp->orphan_done);
 
@@ -2792,14 +2791,14 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
 		 * Stop only if limit reached and CPU has something to do.
 		 * Note: The rcl structure counts down from zero.
 		 */
-		if (-rcu_cblist_n_cbs(&rcl) >= bl &&
+		if (-rcl.len >= bl &&
 		    (need_resched() ||
 		     (!is_idle_task(current) && !rcu_is_callbacks_kthread())))
 			break;
 	}
 
 	local_irq_save(flags);
-	count = -rcu_cblist_n_cbs(&rcl);
+	count = -rcl.len;
 	trace_rcu_batch_end(rsp->name, count, !!rcl.head, need_resched(),
 			    is_idle_task(current), rcu_is_callbacks_kthread());
 

kernel/rcu/tree_plugin.h

@@ -1934,7 +1934,7 @@ static bool __maybe_unused rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
 						     struct rcu_data *rdp,
 						     unsigned long flags)
 {
-	long ql = rcu_cblist_n_cbs(&rsp->orphan_done);
+	long ql = rsp->orphan_done.len;
 	long qll = rcu_cblist_n_lazy_cbs(&rsp->orphan_done);
 
 	/* If this is not a no-CBs CPU, tell the caller to do it the old way. */

kernel/rcu/tree_trace.c

@@ -278,7 +278,7 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
 		   rsp->n_force_qs - rsp->n_force_qs_ngp,
 		   READ_ONCE(rsp->n_force_qs_lh),
 		   rcu_cblist_n_lazy_cbs(&rsp->orphan_done),
-		   rcu_cblist_n_cbs(&rsp->orphan_done));
+		   rsp->orphan_done.len);
 	for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < rcu_num_nodes; rnp++) {
 		if (rnp->level != level) {
 			seq_puts(m, "\n");