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>

1 files changed, 18 insertions, 0 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5e98257c2910..4ac019e9b25f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1076,6 +1076,24 @@ void rcu_irq_enter_irqson(void)
 }
 
 /*
+ * 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
  * to get to a quiescent state, disable it.