rcu: Further shrink Tiny RCU by making empty functions static inlines

The Tiny RCU counterparts to rcu_idle_enter(), rcu_idle_exit(),
rcu_irq_enter(), and rcu_irq_exit() are empty functions, but each has
EXPORT_SYMBOL_GPL(), which needlessly consumes extra memory, especially
in kernels built with module support.  This commit therefore moves these
functions to static inlines in rcutiny.h, removing the need for exports.

This won't affect the size of the tiniest kernels, which are likely
built without module support, but might help semi-tiny kernels that
might include module support.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

3 files changed, 21 insertions, 4 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 87bb0eee665b..1b3d7bcb3a6c 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -292,10 +292,6 @@ void rcu_sched_qs(void);
 void rcu_bh_qs(void);
 void rcu_check_callbacks(int user);
 struct notifier_block;
-void rcu_idle_enter(void);
-void rcu_idle_exit(void);
-void rcu_irq_enter(void);
-void rcu_irq_exit(void);
 int rcu_cpu_notify(struct notifier_block *self,
 		   unsigned long action, void *hcpu);
 
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 937edaeb150d..3df6c1ec4e25 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -159,6 +159,22 @@ static inline void rcu_cpu_stall_reset(void)
 {
 }
 
+static inline void rcu_idle_enter(void)
+{
+}
+
+static inline void rcu_idle_exit(void)
+{
+}
+
+static inline void rcu_irq_enter(void)
+{
+}
+
+static inline void rcu_irq_exit(void)
+{
+}
+
 static inline void exit_rcu(void)
 {
 }
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index d2e583a6aaca..f22d83f49e56 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -93,6 +93,11 @@ void rcu_force_quiescent_state(void);
 void rcu_bh_force_quiescent_state(void);
 void rcu_sched_force_quiescent_state(void);
 
+void rcu_idle_enter(void);
+void rcu_idle_exit(void);
+void rcu_irq_enter(void);
+void rcu_irq_exit(void);
+
 void exit_rcu(void);
 
 void rcu_scheduler_starting(void);