rcu: Rename and comment changes due to only one rcuo kthread per CPU

Given RCU flavor consolidation, the name rcu_spawn_all_nocb_kthreads()
is quite misleading.  It no longer ever creates more than one kthread,
and it does so only for the specified CPU.  This commit therefore changes
this name to the more descriptive rcu_spawn_cpu_nocb_kthread(), and also
fixes up a similar issue in its header comment while in the area.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

kernel/rcu/tree.c

@@ -3299,7 +3299,7 @@ int rcutree_prepare_cpu(unsigned int cpu)
 	trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl"));
 	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
 	rcu_prepare_kthreads(cpu);
-	rcu_spawn_all_nocb_kthreads(cpu);
+	rcu_spawn_cpu_nocb_kthread(cpu);
 
 	return 0;
 }

kernel/rcu/tree.h

@@ -451,7 +451,7 @@ static bool rcu_nocb_adopt_orphan_cbs(struct rcu_data *my_rdp,
 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
 static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
-static void rcu_spawn_all_nocb_kthreads(int cpu);
+static void rcu_spawn_cpu_nocb_kthread(int cpu);
 static void __init rcu_spawn_nocb_kthreads(void);
 #ifdef CONFIG_RCU_NOCB_CPU
 static void __init rcu_organize_nocb_kthreads(void);

kernel/rcu/tree_plugin.h

@@ -2517,9 +2517,9 @@ static void rcu_spawn_one_nocb_kthread(int cpu)
 
 /*
  * If the specified CPU is a no-CBs CPU that does not already have its
- * rcuo kthreads, spawn them.
+ * rcuo kthread, spawn it.
  */
-static void rcu_spawn_all_nocb_kthreads(int cpu)
+static void rcu_spawn_cpu_nocb_kthread(int cpu)
 {
 	if (rcu_scheduler_fully_active)
 		rcu_spawn_one_nocb_kthread(cpu);
@@ -2536,7 +2536,7 @@ static void __init rcu_spawn_nocb_kthreads(void)
 	int cpu;
 
 	for_each_online_cpu(cpu)
-		rcu_spawn_all_nocb_kthreads(cpu);
+		rcu_spawn_cpu_nocb_kthread(cpu);
 }
 
 /* How many follower CPU IDs per leader?  Default of -1 for sqrt(nr_cpu_ids). */
@@ -2670,7 +2670,7 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp)
 {
 }
 
-static void rcu_spawn_all_nocb_kthreads(int cpu)
+static void rcu_spawn_cpu_nocb_kthread(int cpu)
 {
 }