consolidate WARN_...ONCE() static variables

Due to the alignment of following variables, these typically consume
more than just the single byte that 'bool' requires, and as there are a
few hundred instances, the cache pollution (not so much the waste of
memory) sums up.  Put these variables into their own section, outside of
any half way frequently used memory range.

Do the same also to the __warned variable of rcu_lockdep_assert().
(Don't, however, include the ones used by printk_once() and alike, as
they can potentially be hot.)

Signed-off-by: Jan Beulich <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: jbeulich

include/asm-generic/bug.h

@@ -134,7 +134,7 @@ extern void warn_slowpath_null(const char *file, const int line);
 #endif
 
 #define WARN_ON_ONCE(condition)	({				\
-	static bool __warned;					\
+	static bool __section(.data.unlikely) __warned;		\
 	int __ret_warn_once = !!(condition);			\
 								\
 	if (unlikely(__ret_warn_once))				\
@@ -144,7 +144,7 @@ extern void warn_slowpath_null(const char *file, const int line);
 })
 
 #define WARN_ONCE(condition, format...)	({			\
-	static bool __warned;					\
+	static bool __section(.data.unlikely) __warned;		\
 	int __ret_warn_once = !!(condition);			\
 								\
 	if (unlikely(__ret_warn_once))				\
@@ -154,7 +154,7 @@ extern void warn_slowpath_null(const char *file, const int line);
 })
 
 #define WARN_TAINT_ONCE(condition, taint, format...)	({	\
-	static bool __warned;					\
+	static bool __section(.data.unlikely) __warned;		\
 	int __ret_warn_once = !!(condition);			\
 								\
 	if (unlikely(__ret_warn_once))				\

include/asm-generic/vmlinux.lds.h

@@ -167,6 +167,7 @@
 	CPU_KEEP(exit.data)						\
 	MEM_KEEP(init.data)						\
 	MEM_KEEP(exit.data)						\
+	*(.data.unlikely)						\
 	STRUCT_ALIGN();							\
 	*(__tracepoints)						\
 	/* implement dynamic printk debug */				\

include/linux/rcupdate.h

@@ -418,7 +418,7 @@ extern int rcu_my_thread_group_empty(void);
  */
 #define rcu_lockdep_assert(c, s)					\
 	do {								\
-		static bool __warned;					\
+		static bool __section(.data.unlikely) __warned;		\
 		if (debug_lockdep_rcu_enabled() && !__warned && !(c)) {	\
 			__warned = true;				\
 			lockdep_rcu_suspicious(__FILE__, __LINE__, s);	\