rcu: repair code-duplication FIXMEs

Combine the duplicate definitions of ULONG_CMP_GE(), ULONG_CMP_LT(),
and rcu_preempt_depth() into include/linux/rcupdate.h.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

include/linux/rcupdate.h

@@ -47,6 +47,9 @@
 extern int rcutorture_runnable; /* for sysctl */
 #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
 
+#define ULONG_CMP_GE(a, b)	(ULONG_MAX / 2 >= (a) - (b))
+#define ULONG_CMP_LT(a, b)	(ULONG_MAX / 2 < (a) - (b))
+
 /**
  * struct rcu_head - callback structure for use with RCU
  * @next: next update requests in a list
@@ -66,6 +69,18 @@ extern int sched_expedited_torture_stats(char *page);
 /* Internal to kernel */
 extern void rcu_init(void);
 
+#ifdef CONFIG_PREEMPT_RCU
+
+/*
+ * Defined as a macro as it is a very low level header included from
+ * areas that don't even know about current.  This gives the rcu_read_lock()
+ * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other
+ * types of kernel builds, the rcu_read_lock() nesting depth is unknowable.
+ */
+#define rcu_preempt_depth() (current->rcu_read_lock_nesting)
+
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
+
 #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
 #include <linux/rcutree.h>
 #elif defined(CONFIG_TINY_RCU) || defined(CONFIG_TINY_PREEMPT_RCU)

include/linux/rcutiny.h

@@ -133,13 +133,6 @@ static inline int rcu_needs_cpu(int cpu)
 	return rcu_preempt_needs_cpu();
 }
 
-/*
- * Defined as macro as it is a very low level header
- * included from areas that don't even know about current
- * FIXME: combine with include/linux/rcutree.h into rcupdate.h.
- */
-#define rcu_preempt_depth() (current->rcu_read_lock_nesting)
-
 #endif /* #else #ifdef CONFIG_TINY_RCU */
 
 static inline void rcu_note_context_switch(int cpu)

include/linux/rcutree.h

@@ -45,12 +45,6 @@ extern void __rcu_read_unlock(void);
 extern void synchronize_rcu(void);
 extern void exit_rcu(void);
 
-/*
- * Defined as macro as it is a very low level header
- * included from areas that don't even know about current
- */
-#define rcu_preempt_depth() (current->rcu_read_lock_nesting)
-
 #else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
 
 static inline void __rcu_read_lock(void)

kernel/rcutiny_plugin.h

@@ -26,10 +26,6 @@
 
 #include <linux/delay.h>
 
-/* FIXME: merge with definitions in kernel/rcutree.h. */
-#define ULONG_CMP_GE(a, b)	(ULONG_MAX / 2 >= (a) - (b))
-#define ULONG_CMP_LT(a, b)	(ULONG_MAX / 2 < (a) - (b))
-
 /* Global control variables for preemptible RCU. */
 struct rcu_preempt_ctrlblk {
 	struct rcu_ctrlblk rcb;	/* curtail: ->next ptr of last CB for GP. */

kernel/rcutree.h

@@ -272,9 +272,6 @@ struct rcu_data {
 
 #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
 
-#define ULONG_CMP_GE(a, b)	(ULONG_MAX / 2 >= (a) - (b))
-#define ULONG_CMP_LT(a, b)	(ULONG_MAX / 2 < (a) - (b))
-
 /*
  * RCU global state, including node hierarchy.  This hierarchy is
  * represented in "heap" form in a dense array.  The root (first level)