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David Howells5028eaa2009-04-21 23:00:29 +01001#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
Tejun Heo7c756e62009-06-24 15:13:50 +090013 * 'sec' argument. This may be used to affect the parameters governing the
David Howells5028eaa2009-04-21 23:00:29 +010014 * 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 */
Tejun Heo7c756e62009-06-24 15:13:50 +090020#define __PCPU_ATTRS(sec) \
21 __attribute__((section(PER_CPU_BASE_SECTION sec))) \
22 PER_CPU_ATTRIBUTES
David Howells5028eaa2009-04-21 23:00:29 +010023
Tejun Heo7c756e62009-06-24 15:13:50 +090024#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; \
Tejun Heo1a8dd302009-06-29 17:45:39 +090059 extern __PCPU_ATTRS(sec) __typeof__(type) per_cpu__##name
Tejun Heo7c756e62009-06-24 15:13:50 +090060
61#define DEFINE_PER_CPU_SECTION(type, name, sec) \
62 __PCPU_DUMMY_ATTRS char __pcpu_scope_##name; \
Tejun Heo0f5e4812009-10-29 22:34:12 +090063 extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
Tejun Heo7c756e62009-06-24 15:13:50 +090064 __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \
Tejun Heoc43768c2009-07-04 07:13:18 +090065 __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \
Tejun Heob01e8dc2009-06-30 11:41:18 -070066 __typeof__(type) per_cpu__##name
Tejun Heo7c756e62009-06-24 15:13:50 +090067#else
68/*
69 * Normal declaration and definition macros.
70 */
71#define DECLARE_PER_CPU_SECTION(type, name, sec) \
72 extern __PCPU_ATTRS(sec) __typeof__(type) per_cpu__##name
73
74#define DEFINE_PER_CPU_SECTION(type, name, sec) \
Tejun Heoc43768c2009-07-04 07:13:18 +090075 __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \
76 __typeof__(type) per_cpu__##name
Tejun Heo7c756e62009-06-24 15:13:50 +090077#endif
David Howells5028eaa2009-04-21 23:00:29 +010078
79/*
80 * Variant on the per-CPU variable declaration/definition theme used for
81 * ordinary per-CPU variables.
82 */
83#define DECLARE_PER_CPU(type, name) \
84 DECLARE_PER_CPU_SECTION(type, name, "")
85
86#define DEFINE_PER_CPU(type, name) \
87 DEFINE_PER_CPU_SECTION(type, name, "")
88
89/*
90 * Declaration/definition used for per-CPU variables that must come first in
91 * the set of variables.
92 */
93#define DECLARE_PER_CPU_FIRST(type, name) \
94 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
95
96#define DEFINE_PER_CPU_FIRST(type, name) \
97 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
98
99/*
100 * Declaration/definition used for per-CPU variables that must be cacheline
101 * aligned under SMP conditions so that, whilst a particular instance of the
102 * data corresponds to a particular CPU, inefficiencies due to direct access by
103 * other CPUs are reduced by preventing the data from unnecessarily spanning
104 * cachelines.
105 *
106 * An example of this would be statistical data, where each CPU's set of data
107 * is updated by that CPU alone, but the data from across all CPUs is collated
108 * by a CPU processing a read from a proc file.
109 */
110#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \
111 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
112 ____cacheline_aligned_in_smp
113
114#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
115 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
116 ____cacheline_aligned_in_smp
117
Jeremy Fitzhardinge53f82452009-09-03 14:31:44 -0700118#define DECLARE_PER_CPU_ALIGNED(type, name) \
119 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
120 ____cacheline_aligned
121
122#define DEFINE_PER_CPU_ALIGNED(type, name) \
123 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_ALIGNED_SECTION) \
124 ____cacheline_aligned
125
David Howells5028eaa2009-04-21 23:00:29 +0100126/*
127 * Declaration/definition used for per-CPU variables that must be page aligned.
128 */
Tejun Heo3e352aa2009-08-03 14:10:11 +0900129#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
130 DECLARE_PER_CPU_SECTION(type, name, ".page_aligned") \
131 __aligned(PAGE_SIZE)
David Howells5028eaa2009-04-21 23:00:29 +0100132
133#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
Tejun Heo3e352aa2009-08-03 14:10:11 +0900134 DEFINE_PER_CPU_SECTION(type, name, ".page_aligned") \
135 __aligned(PAGE_SIZE)
David Howells5028eaa2009-04-21 23:00:29 +0100136
137/*
138 * Intermodule exports for per-CPU variables.
139 */
140#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
141#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
142
143
144#endif /* _LINUX_PERCPU_DEFS_H */