rcu: Consolidate kfree_call_rcu() to use rcu_state pointer

kfree_call_rcu is defined two times. When defined under CONFIG_TREE_PREEMPT_RCU,
it uses rcu_preempt_state. Otherwise, it uses rcu_sched_state.
This patch uses the rcu_state_pointer to combine the two definitions into one.
The resulting function is placed after the closing of the preprocessor
conditional CONFIG_TREE_PREEMPT_RCU.

Signed-off-by: Andreea-Cristina Bernat <bernat.ada@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

kernel/rcu/tree.c

@@ -2597,6 +2597,20 @@ void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
 }
 EXPORT_SYMBOL_GPL(call_rcu_bh);
 
+/*
+ * Queue an RCU callback for lazy invocation after a grace period.
+ * This will likely be later named something like "call_rcu_lazy()",
+ * but this change will require some way of tagging the lazy RCU
+ * callbacks in the list of pending callbacks. Until then, this
+ * function may only be called from __kfree_rcu().
+ */
+void kfree_call_rcu(struct rcu_head *head,
+		    void (*func)(struct rcu_head *rcu))
+{
+	__call_rcu(head, func, rcu_state, -1, 1);
+}
+EXPORT_SYMBOL_GPL(kfree_call_rcu);
+
 /*
  * Because a context switch is a grace period for RCU-sched and RCU-bh,
  * any blocking grace-period wait automatically implies a grace period

kernel/rcu/tree_plugin.h

@@ -688,20 +688,6 @@ void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
 }
 EXPORT_SYMBOL_GPL(call_rcu);
 
-/*
- * Queue an RCU callback for lazy invocation after a grace period.
- * This will likely be later named something like "call_rcu_lazy()",
- * but this change will require some way of tagging the lazy RCU
- * callbacks in the list of pending callbacks.  Until then, this
- * function may only be called from __kfree_rcu().
- */
-void kfree_call_rcu(struct rcu_head *head,
-		    void (*func)(struct rcu_head *rcu))
-{
-	__call_rcu(head, func, &rcu_preempt_state, -1, 1);
-}
-EXPORT_SYMBOL_GPL(kfree_call_rcu);
-
 /**
  * synchronize_rcu - wait until a grace period has elapsed.
  *
@@ -1079,22 +1065,6 @@ static void rcu_preempt_check_callbacks(int cpu)
 {
 }
 
-/*
- * Queue an RCU callback for lazy invocation after a grace period.
- * This will likely be later named something like "call_rcu_lazy()",
- * but this change will require some way of tagging the lazy RCU
- * callbacks in the list of pending callbacks.  Until then, this
- * function may only be called from __kfree_rcu().
- *
- * Because there is no preemptible RCU, we use RCU-sched instead.
- */
-void kfree_call_rcu(struct rcu_head *head,
-		    void (*func)(struct rcu_head *rcu))
-{
-	__call_rcu(head, func, &rcu_sched_state, -1, 1);
-}
-EXPORT_SYMBOL_GPL(kfree_call_rcu);
-
 /*
  * Wait for an rcu-preempt grace period, but make it happen quickly.
  * But because preemptible RCU does not exist, map to rcu-sched.