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

#ifndef _LINUX_PERCPU_DEFS_H
#define _LINUX_PERCPU_DEFS_H

/*
 * Determine the real variable name from the name visible in the
 * kernel sources.
 */
#define per_cpu_var(var) per_cpu__##var

/*
 * 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) per_cpu__##name

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

#define DEFINE_PER_CPU_SECTION(type, name, sec)				\
	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES			\
	__typeof__(type) per_cpu__##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(per_cpu__##var)
#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)


#endif /* _LINUX_PERCPU_DEFS_H */
Commit	Line	Data
5028eaa9 DH	1	#ifndef _LINUX_PERCPU_DEFS_H
	2	#define _LINUX_PERCPU_DEFS_H
	3
	4	/*
	5	* Determine the real variable name from the name visible in the
	6	* kernel sources.
	7	*/
	8	#define per_cpu_var(var) per_cpu__##var
	9
	10	/*
	11	* Base implementations of per-CPU variable declarations and definitions, where
	12	* the section in which the variable is to be placed is provided by the
7c756e6e	13	* 'sec' argument. This may be used to affect the parameters governing the
5028eaa9 DH	14	* variable's storage.
	15	*
	16	* NOTE! The sections for the DECLARE and for the DEFINE must match, lest
	17	* linkage errors occur due the compiler generating the wrong code to access
	18	* that section.
	19	*/
7c756e6e TH	20	#define __PCPU_ATTRS(sec) \
	21	__attribute__((section(PER_CPU_BASE_SECTION sec))) \
	22	PER_CPU_ATTRIBUTES
	23
	24	#define __PCPU_DUMMY_ATTRS \
	25	__attribute__((section(".discard"), unused))
	26
	27	/*
	28	* s390 and alpha modules require percpu variables to be defined as
	29	* weak to force the compiler to generate GOT based external
	30	* references for them. This is necessary because percpu sections
	31	* will be located outside of the usually addressable area.
	32	*
	33	* This definition puts the following two extra restrictions when
	34	* defining percpu variables.
	35	*
	36	* 1. The symbol must be globally unique, even the static ones.
	37	* 2. Static percpu variables cannot be defined inside a function.
	38	*
	39	* Archs which need weak percpu definitions should define
	40	* ARCH_NEEDS_WEAK_PER_CPU in asm/percpu.h when necessary.
	41	*
	42	* To ensure that the generic code observes the above two
	43	* restrictions, if CONFIG_DEBUG_FORCE_WEAK_PER_CPU is set weak
	44	* definition is used for all cases.
	45	*/
	46	#if defined(ARCH_NEEDS_WEAK_PER_CPU) \|\| defined(CONFIG_DEBUG_FORCE_WEAK_PER_CPU)
	47	/*
	48	* __pcpu_scope_* dummy variable is used to enforce scope. It
	49	* receives the static modifier when it's used in front of
	50	* DEFINE_PER_CPU() and will trigger build failure if
	51	* DECLARE_PER_CPU() is used for the same variable.
	52	*
	53	* __pcpu_unique_* dummy variable is used to enforce symbol uniqueness
	54	* such that hidden weak symbol collision, which will cause unrelated
	55	* variables to share the same address, can be detected during build.
	56	*/
	57	#define DECLARE_PER_CPU_SECTION(type, name, sec) \
	58	extern __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
1a8dd307	59	extern __PCPU_ATTRS(sec) __typeof__(type) per_cpu__##name
7c756e6e TH	60
	61	#define DEFINE_PER_CPU_SECTION(type, name, sec) \
	62	__PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
	63	__PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
c43768cb TH	64	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \
c43768cb TH	65	__typeof__(type) per_cpu__##name
7c756e6e TH	66	#else
	67	/*
	68	* Normal declaration and definition macros.
	69	*/
	70	#define DECLARE_PER_CPU_SECTION(type, name, sec) \
	71	extern __PCPU_ATTRS(sec) __typeof__(type) per_cpu__##name
	72
	73	#define DEFINE_PER_CPU_SECTION(type, name, sec) \
c43768cb	74	__PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \
b01e8dc3	75	__typeof__(type) per_cpu__##name
7c756e6e	76	#endif
5028eaa9 DH	77
	78	/*
	79	* Variant on the per-CPU variable declaration/definition theme used for
	80	* ordinary per-CPU variables.
	81	*/
	82	#define DECLARE_PER_CPU(type, name) \
	83	DECLARE_PER_CPU_SECTION(type, name, "")
	84
	85	#define DEFINE_PER_CPU(type, name) \
	86	DEFINE_PER_CPU_SECTION(type, name, "")
	87
	88	/*
	89	* Declaration/definition used for per-CPU variables that must come first in
	90	* the set of variables.
	91	*/
	92	#define DECLARE_PER_CPU_FIRST(type, name) \
	93	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
	94
	95	#define DEFINE_PER_CPU_FIRST(type, name) \
	96	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
	97
	98	/*
	99	* Declaration/definition used for per-CPU variables that must be cacheline
	100	* aligned under SMP conditions so that, whilst a particular instance of the
	101	* data corresponds to a particular CPU, inefficiencies due to direct access by
	102	* other CPUs are reduced by preventing the data from unnecessarily spanning
	103	* cachelines.
	104	*
	105	* An example of this would be statistical data, where each CPU's set of data
	106	* is updated by that CPU alone, but the data from across all CPUs is collated
	107	* by a CPU processing a read from a proc file.
	108	*/
	109	#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \
	110	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
	111	____cacheline_aligned_in_smp
	112
	113	#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
	114	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
	115	____cacheline_aligned_in_smp
	116
53f82452 JF	117	#define DECLARE_PER_CPU_ALIGNED(type, name) \
	118	DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
	119	____cacheline_aligned
	120
	121	#define DEFINE_PER_CPU_ALIGNED(type, name) \
	122	DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
	123	____cacheline_aligned
	124
5028eaa9 DH	125	/*
	126	* Declaration/definition used for per-CPU variables that must be page aligned.
	127	*/
3e352aa8 TH	128	#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
	129	DECLARE_PER_CPU_SECTION(type, name, ".page_aligned") \
	130	__aligned(PAGE_SIZE)
5028eaa9 DH	131
5028eaa9 DH	132	#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
3e352aa8 TH	133	DEFINE_PER_CPU_SECTION(type, name, ".page_aligned") \
3e352aa8 TH	134	__aligned(PAGE_SIZE)
5028eaa9 DH	135
	136	/*
	137	* Intermodule exports for per-CPU variables.
	138	*/
	139	#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
	140	#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
	141
	142
	143	#endif /* _LINUX_PERCPU_DEFS_H */