rcu/nocb: Merge rcu_spawn_cpu_nocb_kthread() and rcu_spawn_one_nocb_kthread()

The rcu_spawn_one_nocb_kthread() function is called only from
rcu_spawn_cpu_nocb_kthread().  Therefore, inline the former into
the latter, saving a few lines of code.
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/tree_nocb.h

@@ -1233,12 +1233,15 @@ static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
  * rcuo CB kthread, spawn it.  Additionally, if the rcuo GP kthread
  * for this CPU's group has not yet been created, spawn it as well.
  */
-static void rcu_spawn_one_nocb_kthread(int cpu)
+static void rcu_spawn_cpu_nocb_kthread(int cpu)
 {
 	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
 	struct rcu_data *rdp_gp;
 	struct task_struct *t;
 
+	if (!rcu_scheduler_fully_active || !rcu_nocb_is_setup)
+		return;
+
 	/* If there already is an rcuo kthread, then nothing to do. */
 	if (rdp->nocb_cb_kthread)
 		return;
@@ -1262,16 +1265,6 @@ static void rcu_spawn_one_nocb_kthread(int cpu)
 	WRITE_ONCE(rdp->nocb_gp_kthread, rdp_gp->nocb_gp_kthread);
 }
 
-/*
- * If the specified CPU is a no-CBs CPU that does not already have its
- * rcuo kthread, spawn it.
- */
-static void rcu_spawn_cpu_nocb_kthread(int cpu)
-{
-	if (rcu_scheduler_fully_active && rcu_nocb_is_setup)
-		rcu_spawn_one_nocb_kthread(cpu);
-}
-
 /*
  * Once the scheduler is running, spawn rcuo kthreads for all online
  * no-CBs CPUs.  This assumes that the early_initcall()s happen before