[deliverable/linux.git] / include / linux / percpu-defs.h

#ifndef _LINUX_PERCPU_DEFS_H
#define _LINUX_PERCPU_DEFS_H

/*
 * Base implementations of per-CPU variable declarations and definitions, where
 * the section in which the variable is to be placed is provided by the
 * 'sec' argument.  This may be used to affect the parameters governing the
 * variable's storage.
 *
 * NOTE!  The sections for the DECLARE and for the DEFINE must match, lest
 * linkage errors occur due the compiler generating the wrong code to access
 * that section.
 */
#define __PCPU_ATTRS(sec)						\
	__attribute__((section(PER_CPU_BASE_SECTION sec)))		\
	PER_CPU_ATTRIBUTES

#define __PCPU_DUMMY_ATTRS						\
	__attribute__((section(".discard"), unused))

/*
 * s390 and alpha modules require percpu variables to be defined as
 * weak to force the compiler to generate GOT based external
 * references for them.  This is necessary because percpu sections
 * will be located outside of the usually addressable area.
 *
 * This definition puts the following two extra restrictions when
 * defining percpu variables.
 *
 * 1. The symbol must be globally unique, even the static ones.
 * 2. Static percpu variables cannot be defined inside a function.
 *
 * Archs which need weak percpu definitions should define
 * ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
 *
 * To ensure that the generic code observes the above two
 * restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
 * definition is used for all cases.
 */
#if defined(ARCH_NEEDS_WEAK_PER_CPU) || defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
/*
 * __pcpu_scope_* dummy variable is used to enforce scope.  It
 * receives the static modifier when it's used in front of
 * DEFINE_PER_CPU() and will trigger build failure if
 * DECLARE_PER_CPU() is used for the same variable.
 *
 * __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
 * such that hidden weak symbol collision, which will cause unrelated
 * variables to share the same address, can be detected during build.
 */
#define DECLARE_PER_CPU_SECTION(type, name, sec)			\
	extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name;		\
	extern __PCPU_ATTRS(sec) __typeof__(type) name

#define DEFINE_PER_CPU_SECTION(type, name, sec)				\
	__PCPU_DUMMY_ATTRS char __pcpu_scope_##name;			\
	extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name;		\
	__PCPU_DUMMY_ATTRS char __pcpu_unique_##name;			\
	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak			\
	__typeof__(type) name
#else
/*
 * Normal declaration and definition macros.
 */
#define DECLARE_PER_CPU_SECTION(type, name, sec)			\
	extern __PCPU_ATTRS(sec) __typeof__(type) name

#define DEFINE_PER_CPU_SECTION(type, name, sec)				\
	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES			\
	__typeof__(type) name
#endif

/*
 * Variant on the per-CPU variable declaration/definition theme used for
 * ordinary per-CPU variables.
 */
#define DECLARE_PER_CPU(type, name)					\
	DECLARE_PER_CPU_SECTION(type, name, "")

#define DEFINE_PER_CPU(type, name)					\
	DEFINE_PER_CPU_SECTION(type, name, "")

/*
 * Declaration/definition used for per-CPU variables that must come first in
 * the set of variables.
 */
#define DECLARE_PER_CPU_FIRST(type, name)				\
	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)

#define DEFINE_PER_CPU_FIRST(type, name)				\
	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)

/*
 * Declaration/definition used for per-CPU variables that must be cacheline
 * aligned under SMP conditions so that, whilst a particular instance of the
 * data corresponds to a particular CPU, inefficiencies due to direct access by
 * other CPUs are reduced by preventing the data from unnecessarily spanning
 * cachelines.
 *
 * An example of this would be statistical data, where each CPU's set of data
 * is updated by that CPU alone, but the data from across all CPUs is collated
 * by a CPU processing a read from a proc file.
 */
#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name)			\
	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
	____cacheline_aligned_in_smp

#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name)			\
	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
	____cacheline_aligned_in_smp

#define DECLARE_PER_CPU_ALIGNED(type, name)				\
	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)	\
	____cacheline_aligned

#define DEFINE_PER_CPU_ALIGNED(type, name)				\
	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION)	\
	____cacheline_aligned

/*
 * Declaration/definition used for per-CPU variables that must be page aligned.
 */
#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name)			\
	DECLARE_PER_CPU_SECTION(type, name, ".page_aligned")		\
	__aligned(PAGE_SIZE)

#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name)				\
	DEFINE_PER_CPU_SECTION(type, name, ".page_aligned")		\
	__aligned(PAGE_SIZE)

/*
 * Intermodule exports for per-CPU variables.
 */
#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var)
#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var)


#endif /* _LINUX_PERCPU_DEFS_H */
Commit	Line	Data
5028eaa9 DH	1	#ifndef _LINUX_PERCPU_DEFS_H
	2	#define _LINUX_PERCPU_DEFS_H
	3
5028eaa9 DH	4	/*
	5	* Base implementations of per-CPU variable declarations and definitions, where
	6	* the section in which the variable is to be placed is provided by the
7c756e6e	7	* 'sec' argument. This may be used to affect the parameters governing the
5028eaa9 DH	8	* variable's storage.
	9	*
	10	* NOTE! The sections for the DECLARE and for the DEFINE must match, lest
	11	* linkage errors occur due the compiler generating the wrong code to access
	12	* that section.
	13	*/
7c756e6e TH	14	#define __PCPU_ATTRS(sec) \
	15	__attribute__((section(PER_CPU_BASE_SECTION sec))) \
	16	PER_CPU_ATTRIBUTES
	17
	18	#define __PCPU_DUMMY_ATTRS \
	19	__attribute__((section(".discard"), unused))
	20
	21	/*
	22	* s390 and alpha modules require percpu variables to be defined as
	23	* weak to force the compiler to generate GOT based external
	24	* references for them. This is necessary because percpu sections
	25	* will be located outside of the usually addressable area.
	26	*
	27	* This definition puts the following two extra restrictions when
	28	* defining percpu variables.
	29	*
	30	* 1. The symbol must be globally unique, even the static ones.
	31	* 2. Static percpu variables cannot be defined inside a function.
	32	*
	33	* Archs which need weak percpu definitions should define
	34	* ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
	35	*
	36	* To ensure that the generic code observes the above two
	37	* restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
	38	* definition is used for all cases.
	39	*/
	40	#if defined(ARCH_NEEDS_WEAK_PER_CPU) \|\| defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
	41	/*
	42	* __pcpu_scope_* dummy variable is used to enforce scope. It
	43	* receives the static modifier when it's used in front of
	44	* DEFINE_PER_CPU() and will trigger build failure if
	45	* DECLARE_PER_CPU() is used for the same variable.
	46	*
	47	* __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
	48	* such that hidden weak symbol collision, which will cause unrelated
	49	* variables to share the same address, can be detected during build.
	50	*/
	51	#define DECLARE_PER_CPU_SECTION(type, name, sec) \
	52	extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
dd17c8f7	53	extern __PCPU_ATTRS(sec) __typeof__(type) name
7c756e6e TH	54
	55	#define DEFINE_PER_CPU_SECTION(type, name, sec) \
	56	__PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
0f5e4816	57	extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
7c756e6e	58	__PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
c43768cb	59	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \
dd17c8f7	60	__typeof__(type) name
7c756e6e TH	61	#else
	62	/*
	63	* Normal declaration and definition macros.
	64	*/
	65	#define DECLARE_PER_CPU_SECTION(type, name, sec) \
dd17c8f7	66	extern __PCPU_ATTRS(sec) __typeof__(type) name
7c756e6e TH	67
7c756e6e TH	68	#define DEFINE_PER_CPU_SECTION(type, name, sec) \
c43768cb	69	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \
dd17c8f7	70	__typeof__(type) name
7c756e6e	71	#endif
5028eaa9 DH	72
	73	/*
	74	* Variant on the per-CPU variable declaration/definition theme used for
	75	* ordinary per-CPU variables.
	76	*/
	77	#define DECLARE_PER_CPU(type, name) \
	78	DECLARE_PER_CPU_SECTION(type, name, "")
	79
	80	#define DEFINE_PER_CPU(type, name) \
	81	DEFINE_PER_CPU_SECTION(type, name, "")
	82
	83	/*
	84	* Declaration/definition used for per-CPU variables that must come first in
	85	* the set of variables.
	86	*/
	87	#define DECLARE_PER_CPU_FIRST(type, name) \
	88	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
	89
	90	#define DEFINE_PER_CPU_FIRST(type, name) \
	91	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
	92
	93	/*
	94	* Declaration/definition used for per-CPU variables that must be cacheline
	95	* aligned under SMP conditions so that, whilst a particular instance of the
	96	* data corresponds to a particular CPU, inefficiencies due to direct access by
	97	* other CPUs are reduced by preventing the data from unnecessarily spanning
	98	* cachelines.
	99	*
	100	* An example of this would be statistical data, where each CPU's set of data
	101	* is updated by that CPU alone, but the data from across all CPUs is collated
	102	* by a CPU processing a read from a proc file.
	103	*/
	104	#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \
	105	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
	106	____cacheline_aligned_in_smp
	107
	108	#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
	109	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
	110	____cacheline_aligned_in_smp
	111
53f82452 JF	112	#define DECLARE_PER_CPU_ALIGNED(type, name) \
	113	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
	114	____cacheline_aligned
	115
	116	#define DEFINE_PER_CPU_ALIGNED(type, name) \
	117	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
	118	____cacheline_aligned
	119
5028eaa9 DH	120	/*
	121	* Declaration/definition used for per-CPU variables that must be page aligned.
	122	*/
3e352aa8 TH	123	#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
	124	DECLARE_PER_CPU_SECTION(type, name, ".page_aligned") \
	125	__aligned(PAGE_SIZE)
5028eaa9 DH	126
5028eaa9 DH	127	#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
3e352aa8 TH	128	DEFINE_PER_CPU_SECTION(type, name, ".page_aligned") \
3e352aa8 TH	129	__aligned(PAGE_SIZE)
5028eaa9 DH	130
	131	/*
	132	* Intermodule exports for per-CPU variables.
	133	*/
dd17c8f7 RR	134	#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(var)
dd17c8f7 RR	135	#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(var)
5028eaa9 DH	136
	137
	138	#endif /* _LINUX_PERCPU_DEFS_H */