rcu: Move rcu_needs_cpu() to tree.c

Now that RCU_FAST_NO_HZ is no more, there is but one implementation of
the rcu_needs_cpu() function.  This commit therefore moves this function
from kernel/rcu/tree_plugin.c to kernel/rcu/tree.c.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/tree.c

@@ -1075,6 +1075,24 @@ void rcu_irq_enter_irqson(void)
 	local_irq_restore(flags);
 }
 
+/*
+ * Check to see if any future non-offloaded RCU-related work will need
+ * to be done by the current CPU, even if none need be done immediately,
+ * returning 1 if so.  This function is part of the RCU implementation;
+ * it is -not- an exported member of the RCU API.  This is used by
+ * the idle-entry code to figure out whether it is safe to disable the
+ * scheduler-clock interrupt.
+ *
+ * Just check whether or not this CPU has non-offloaded RCU callbacks
+ * queued.
+ */
+int rcu_needs_cpu(u64 basemono, u64 *nextevt)
+{
+	*nextevt = KTIME_MAX;
+	return !rcu_segcblist_empty(&this_cpu_ptr(&rcu_data)->cblist) &&
+		!rcu_rdp_is_offloaded(this_cpu_ptr(&rcu_data));
+}
+
 /*
  * If any sort of urgency was applied to the current CPU (for example,
  * the scheduler-clock interrupt was enabled on a nohz_full CPU) in order

kernel/rcu/tree_plugin.h

@@ -1251,22 +1251,6 @@ static void __init rcu_spawn_boost_kthreads(void)
 
 #endif /* #else #ifdef CONFIG_RCU_BOOST */
 
-/*
- * Check to see if any future non-offloaded RCU-related work will need
- * to be done by the current CPU, even if none need be done immediately,
- * returning 1 if so.  This function is part of the RCU implementation;
- * it is -not- an exported member of the RCU API.
- *
- * Just check whether or not this CPU has non-offloaded RCU callbacks
- * queued.
- */
-int rcu_needs_cpu(u64 basemono, u64 *nextevt)
-{
-	*nextevt = KTIME_MAX;
-	return !rcu_segcblist_empty(&this_cpu_ptr(&rcu_data)->cblist) &&
-		!rcu_rdp_is_offloaded(this_cpu_ptr(&rcu_data));
-}
-
 /*
  * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the
  * grace-period kthread will do force_quiescent_state() processing?