From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 10 Feb 2016 18:30:56 +0100
Subject: rcu: disable more spots of rcu_bh
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.6/older/patches-4.6.2-rt5.tar.xz

We don't use ru_bh on -RT but we still fork a thread for it and keep it
as a flavour. No more.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/rcu/tree.c |    6 ++++++
 kernel/rcu/tree.h |    2 ++
 2 files changed, 8 insertions(+)

--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -440,11 +440,13 @@ EXPORT_SYMBOL_GPL(rcu_batches_started_sc
 /*
  * Return the number of RCU BH batches started thus far for debug & stats.
  */
+#ifndef CONFIG_PREEMPT_RT_FULL
 unsigned long rcu_batches_started_bh(void)
 {
 	return rcu_bh_state.gpnum;
 }
 EXPORT_SYMBOL_GPL(rcu_batches_started_bh);
+#endif
 
 /*
  * Return the number of RCU batches completed thus far for debug & stats.
@@ -549,9 +551,11 @@ void rcutorture_get_gp_data(enum rcutort
 	case RCU_FLAVOR:
 		rsp = rcu_state_p;
 		break;
+#ifndef CONFIG_PREEMPT_RT_FULL
 	case RCU_BH_FLAVOR:
 		rsp = &rcu_bh_state;
 		break;
+#endif
 	case RCU_SCHED_FLAVOR:
 		rsp = &rcu_sched_state;
 		break;
@@ -4637,7 +4641,9 @@ void __init rcu_init(void)
 
 	rcu_bootup_announce();
 	rcu_init_geometry();
+#ifndef CONFIG_PREEMPT_RT_FULL
 	rcu_init_one(&rcu_bh_state);
+#endif
 	rcu_init_one(&rcu_sched_state);
 	if (dump_tree)
 		rcu_dump_rcu_node_tree(&rcu_sched_state);
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -572,7 +572,9 @@ extern struct list_head rcu_struct_flavo
  */
 extern struct rcu_state rcu_sched_state;
 
+#ifndef CONFIG_PREEMPT_RT_FULL
 extern struct rcu_state rcu_bh_state;
+#endif
 
 #ifdef CONFIG_PREEMPT_RCU
 extern struct rcu_state rcu_preempt_state;
