x86: Define early read-mostly per-cpu macros

Some read-mostly per-cpu data may need to be declared or defined
early, so it can be initialized and accessed before per_cpu
areas are allocated.

Only the data that resides in the per_cpu areas should be
read-mostly, as there is little benefit in optimizing cache
lines on initialization.

Signed-off-by: Ido Yariv <ido@wizery.com>
[ Added the missing declarations in !SMP code. ]
Signed-off-by: Vlad Zolotarov <vlad@scalemp.com>
Acked-by: Shai Fultheim <shai@scalemp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/46188571.ddB8aVQYWo@vlad
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/percpu.h

@@ -551,6 +551,12 @@ DECLARE_PER_CPU(unsigned long, this_cpu_off);
 				{ [0 ... NR_CPUS-1] = _initvalue };	\
 	__typeof__(_type) *_name##_early_ptr __refdata = _name##_early_map
 
+#define DEFINE_EARLY_PER_CPU_READ_MOSTLY(_type, _name, _initvalue)	\
+	DEFINE_PER_CPU_READ_MOSTLY(_type, _name) = _initvalue;		\
+	__typeof__(_type) _name##_early_map[NR_CPUS] __initdata =	\
+				{ [0 ... NR_CPUS-1] = _initvalue };	\
+	__typeof__(_type) *_name##_early_ptr __refdata = _name##_early_map
+
 #define EXPORT_EARLY_PER_CPU_SYMBOL(_name)			\
 	EXPORT_PER_CPU_SYMBOL(_name)
 
@@ -559,6 +565,11 @@ DECLARE_PER_CPU(unsigned long, this_cpu_off);
 	extern __typeof__(_type) *_name##_early_ptr;		\
 	extern __typeof__(_type)  _name##_early_map[]
 
+#define DECLARE_EARLY_PER_CPU_READ_MOSTLY(_type, _name)		\
+	DECLARE_PER_CPU_READ_MOSTLY(_type, _name);		\
+	extern __typeof__(_type) *_name##_early_ptr;		\
+	extern __typeof__(_type)  _name##_early_map[]
+
 #define	early_per_cpu_ptr(_name) (_name##_early_ptr)
 #define	early_per_cpu_map(_name, _idx) (_name##_early_map[_idx])
 #define	early_per_cpu(_name, _cpu) 				\
@@ -570,12 +581,18 @@ DECLARE_PER_CPU(unsigned long, this_cpu_off);
 #define	DEFINE_EARLY_PER_CPU(_type, _name, _initvalue)		\
 	DEFINE_PER_CPU(_type, _name) = _initvalue
 
+#define DEFINE_EARLY_PER_CPU_READ_MOSTLY(_type, _name, _initvalue)	\
+	DEFINE_PER_CPU_READ_MOSTLY(_type, _name) = _initvalue
+
 #define EXPORT_EARLY_PER_CPU_SYMBOL(_name)			\
 	EXPORT_PER_CPU_SYMBOL(_name)
 
 #define DECLARE_EARLY_PER_CPU(_type, _name)			\
 	DECLARE_PER_CPU(_type, _name)
 
+#define DECLARE_EARLY_PER_CPU_READ_MOSTLY(_type, _name)		\
+	DECLARE_PER_CPU_READ_MOSTLY(_type, _name)
+
 #define	early_per_cpu(_name, _cpu) per_cpu(_name, _cpu)
 #define	early_per_cpu_ptr(_name) NULL
 /* no early_per_cpu_map() */