rcu: Move kthread_prio bounds-check to a separate function

Move the bounds-check of the kthread_prio cmdline parameter to a new
function in order to faciliate a different callsite.

Signed-off-by: Alison Chaiken <achaiken@aurora.tech>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Author: chaiken

kernel/rcu/tree.c

@@ -4440,26 +4440,10 @@ static int rcu_pm_notify(struct notifier_block *self,
 static int __init rcu_spawn_gp_kthread(void)
 {
 	unsigned long flags;
-	int kthread_prio_in = kthread_prio;
 	struct rcu_node *rnp;
 	struct sched_param sp;
 	struct task_struct *t;
 
-	/* Force priority into range. */
-	if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 2
-	    && IS_BUILTIN(CONFIG_RCU_TORTURE_TEST))
-		kthread_prio = 2;
-	else if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1)
-		kthread_prio = 1;
-	else if (kthread_prio < 0)
-		kthread_prio = 0;
-	else if (kthread_prio > 99)
-		kthread_prio = 99;
-
-	if (kthread_prio != kthread_prio_in)
-		pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n",
-			 kthread_prio, kthread_prio_in);
-
 	rcu_scheduler_fully_active = 1;
 	t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name);
 	if (WARN_ONCE(IS_ERR(t), "%s: Could not start grace-period kthread, OOM is now expected behavior\n", __func__))
@@ -4584,6 +4568,28 @@ static void __init rcu_init_one(void)
 	}
 }
 
+/*
+ * Force priority from the kernel command-line into range.
+ */
+static void __init sanitize_kthread_prio(void)
+{
+	int kthread_prio_in = kthread_prio;
+
+	if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 2
+	    && IS_BUILTIN(CONFIG_RCU_TORTURE_TEST))
+		kthread_prio = 2;
+	else if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1)
+		kthread_prio = 1;
+	else if (kthread_prio < 0)
+		kthread_prio = 0;
+	else if (kthread_prio > 99)
+		kthread_prio = 99;
+
+	if (kthread_prio != kthread_prio_in)
+		pr_alert("%s: Limited prio to %d from %d\n",
+			 __func__, kthread_prio, kthread_prio_in);
+}
+
 /*
  * Compute the rcu_node tree geometry from kernel parameters.  This cannot
  * replace the definitions in tree.h because those are needed to size
@@ -4744,6 +4750,7 @@ void __init rcu_init(void)
 
 	kfree_rcu_batch_init();
 	rcu_bootup_announce();
+	sanitize_kthread_prio();
 	rcu_init_geometry();
 	rcu_init_one();
 	if (dump_tree)