[PATCH rcu 3/6] srcu,notifier: Remove #ifdefs in favor of SRCU Tiny srcu_usage

["Paul E. McKenney" <paulmck@xxxxxxxxxx>]

This commit removes two #ifdef directives from include/linux/notifier.h
by causing SRCU Tiny to provide a dummy srcu_usage structure and a dummy
__SRCU_USAGE_INIT() macro.

Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: atthias Brugger <matthias.bgg@xxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
Cc: "Michał Mirosław" <mirq-linux@xxxxxxxxxxxx>
Cc: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Cc: Sachin Sant <sachinp@xxxxxxxxxxxxx>
Cc: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 include/linux/notifier.h | 11 -----------
 include/linux/srcutiny.h |  7 +++++++
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index 86544707236a..45702bdcbceb 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -73,9 +73,7 @@ struct raw_notifier_head {
 
 struct srcu_notifier_head {
 	struct mutex mutex;
-#ifdef CONFIG_TREE_SRCU
 	struct srcu_usage srcuu;
-#endif
 	struct srcu_struct srcu;
 	struct notifier_block __rcu *head;
 };
@@ -106,7 +104,6 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
 #define RAW_NOTIFIER_INIT(name)	{				\
 		.head = NULL }
 
-#ifdef CONFIG_TREE_SRCU
 #define SRCU_NOTIFIER_INIT(name, pcpu)				\
 	{							\
 		.mutex = __MUTEX_INITIALIZER(name.mutex),	\
@@ -114,14 +111,6 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
 		.srcuu = __SRCU_USAGE_INIT(name.srcuu),		\
 		.srcu = __SRCU_STRUCT_INIT(name.srcu, name.srcuu, pcpu), \
 	}
-#else
-#define SRCU_NOTIFIER_INIT(name, pcpu)				\
-	{							\
-		.mutex = __MUTEX_INITIALIZER(name.mutex),	\
-		.head = NULL,					\
-		.srcu = __SRCU_STRUCT_INIT(name.srcu, name.srcuu, pcpu), \
-	}
-#endif
 
 #define ATOMIC_NOTIFIER_HEAD(name)				\
 	struct atomic_notifier_head name =			\
diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
index ebd72491af99..06ce65518974 100644
--- a/include/linux/srcutiny.h
+++ b/include/linux/srcutiny.h
@@ -48,6 +48,13 @@ void srcu_drive_gp(struct work_struct *wp);
 #define DEFINE_STATIC_SRCU(name) \
 	static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name)
 
+// Dummy structure for srcu_notifier_head.
+struct srcu_usage {
+	char srcuu_dummy;
+};
+
+#define __SRCU_USAGE_INIT(name) { .srcuu_dummy = 0, }
+
 void synchronize_srcu(struct srcu_struct *ssp);
 
 /*
-- 
2.40.1