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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 |
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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; \ | |
0f5e4816 | 63 | extern __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \ |
7c756e6e | 64 | __PCPU_DUMMY_ATTRS char __pcpu_unique_##name; \ |
c43768cb TH |
65 | __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES __weak \ |
66 | __typeof__(type) per_cpu__##name | |
7c756e6e TH |
67 | #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) \ | |
c43768cb | 75 | __PCPU_ATTRS(sec) PER_CPU_DEF_ATTRIBUTES \ |
b01e8dc3 | 76 | __typeof__(type) per_cpu__##name |
7c756e6e | 77 | #endif |
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78 | |
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 | ||
53f82452 JF |
118 | #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 | ||
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126 | /* |
127 | * Declaration/definition used for per-CPU variables that must be page aligned. | |
128 | */ | |
3e352aa8 TH |
129 | #define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \ |
130 | DECLARE_PER_CPU_SECTION(type, name, ".page_aligned") \ | |
131 | __aligned(PAGE_SIZE) | |
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132 | |
133 | #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \ | |
3e352aa8 TH |
134 | DEFINE_PER_CPU_SECTION(type, name, ".page_aligned") \ |
135 | __aligned(PAGE_SIZE) | |
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136 | |
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 */ |