[PATCH] srcu: Isolate srcu sections using CONFIG_SRCU

[Pranith Kumar]

Isolate the SRCU functions and data structures within CONFIG_SRCU so that there
is a compile time failure if srcu is used when not enabled. This was decided to
be better than waiting until link time for a failure to occur.

Signed-off-by: Pranith Kumar <bobby.prani@xxxxxxxxx>
CC: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CC: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
CC: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
---
 include/linux/notifier.h | 45 +++++++++++++++++++++++++--------------------
 include/linux/srcu.h     |  6 +++++-
 2 files changed, 30 insertions(+), 21 deletions(-)

diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index d14a4c3..291ecb1 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -70,12 +70,6 @@ struct raw_notifier_head {
 	struct notifier_block __rcu *head;
 };
 
-struct srcu_notifier_head {
-	struct mutex mutex;
-	struct srcu_struct srcu;
-	struct notifier_block __rcu *head;
-};
-
 #define ATOMIC_INIT_NOTIFIER_HEAD(name) do {	\
 		spin_lock_init(&(name)->lock);	\
 		(name)->head = NULL;		\
@@ -88,11 +82,6 @@ struct srcu_notifier_head {
 		(name)->head = NULL;		\
 	} while (0)
 
-/* srcu_notifier_heads must be initialized and cleaned up dynamically */
-extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
-#define srcu_cleanup_notifier_head(name)	\
-		cleanup_srcu_struct(&(name)->srcu);
-
 #define ATOMIC_NOTIFIER_INIT(name) {				\
 		.lock = __SPIN_LOCK_UNLOCKED(name.lock),	\
 		.head = NULL }
@@ -101,7 +90,6 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
 		.head = NULL }
 #define RAW_NOTIFIER_INIT(name)	{				\
 		.head = NULL }
-/* srcu_notifier_heads cannot be initialized statically */
 
 #define ATOMIC_NOTIFIER_HEAD(name)				\
 	struct atomic_notifier_head name =			\
@@ -121,8 +109,6 @@ extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
 		struct notifier_block *nb);
 extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
 		struct notifier_block *nb);
-extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
-		struct notifier_block *nb);
 
 extern int blocking_notifier_chain_cond_register(
 		struct blocking_notifier_head *nh,
@@ -134,8 +120,6 @@ extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
 		struct notifier_block *nb);
 extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
 		struct notifier_block *nb);
-extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
-		struct notifier_block *nb);
 
 extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
 		unsigned long val, void *v);
@@ -149,10 +133,6 @@ extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
 		unsigned long val, void *v);
 extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
 	unsigned long val, void *v, int nr_to_call, int *nr_calls);
-extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
-		unsigned long val, void *v);
-extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
-	unsigned long val, void *v, int nr_to_call, int *nr_calls);
 
 #define NOTIFY_DONE		0x0000		/* Don't care */
 #define NOTIFY_OK		0x0001		/* Suits me */
@@ -211,5 +191,30 @@ static inline int notifier_to_errno(int ret)
 
 extern struct blocking_notifier_head reboot_notifier_list;
 
+#ifdef CONFIG_SRCU
+
+struct srcu_notifier_head {
+	struct mutex mutex;
+	struct srcu_struct srcu;
+	struct notifier_block __rcu *head;
+};
+
+/* srcu_notifier_heads must be initialized and cleaned up dynamically
+ * srcu_notifier_heads cannot be initialized statically
+ */
+extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
+#define srcu_cleanup_notifier_head(name) cleanup_srcu_struct(&(name)->srcu)
+
+extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
+		struct notifier_block *nb);
+extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
+		struct notifier_block *nb);
+extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
+		unsigned long val, void *v);
+extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
+	unsigned long val, void *v, int nr_to_call, int *nr_calls);
+
+#endif /* CONFIG_SRCU */
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_NOTIFIER_H */
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 9cfd962..ed9c389 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -26,6 +26,8 @@
  *
  */
 
+#ifdef CONFIG_SRCU
+
 #ifndef _LINUX_SRCU_H
 #define _LINUX_SRCU_H
 
@@ -249,4 +251,6 @@ static inline void smp_mb__after_srcu_read_unlock(void)
 	/* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
 }
 
-#endif
+#endif /* _LINUX_SRCU_H */
+
+#endif /* CONFIG_SRCU */
-- 
1.9.1

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