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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
13 * 'section' argument. This may be used to affect the parameters governing the
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 */
20#define DECLARE_PER_CPU_SECTION(type, name, section) \
21 extern \
22 __attribute__((__section__(PER_CPU_BASE_SECTION section))) \
23 PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name
24
25#define DEFINE_PER_CPU_SECTION(type, name, section) \
26 __attribute__((__section__(PER_CPU_BASE_SECTION section))) \
27 PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name
28
29/*
30 * Variant on the per-CPU variable declaration/definition theme used for
31 * ordinary per-CPU variables.
32 */
33#define DECLARE_PER_CPU(type, name) \
34 DECLARE_PER_CPU_SECTION(type, name, "")
35
36#define DEFINE_PER_CPU(type, name) \
37 DEFINE_PER_CPU_SECTION(type, name, "")
38
39/*
40 * Declaration/definition used for per-CPU variables that must come first in
41 * the set of variables.
42 */
43#define DECLARE_PER_CPU_FIRST(type, name) \
44 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
45
46#define DEFINE_PER_CPU_FIRST(type, name) \
47 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
48
49/*
50 * Declaration/definition used for per-CPU variables that must be cacheline
51 * aligned under SMP conditions so that, whilst a particular instance of the
52 * data corresponds to a particular CPU, inefficiencies due to direct access by
53 * other CPUs are reduced by preventing the data from unnecessarily spanning
54 * cachelines.
55 *
56 * An example of this would be statistical data, where each CPU's set of data
57 * is updated by that CPU alone, but the data from across all CPUs is collated
58 * by a CPU processing a read from a proc file.
59 */
60#define DECLARE_PER_CPU_SHARED_ALIGNED(type, name) \
61 DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
62 ____cacheline_aligned_in_smp
63
64#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \
65 DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
66 ____cacheline_aligned_in_smp
67
68/*
69 * Declaration/definition used for per-CPU variables that must be page aligned.
70 */
71#define DECLARE_PER_CPU_PAGE_ALIGNED(type, name) \
72 DECLARE_PER_CPU_SECTION(type, name, ".page_aligned")
73
74#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \
75 DEFINE_PER_CPU_SECTION(type, name, ".page_aligned")
76
77/*
78 * Intermodule exports for per-CPU variables.
79 */
80#define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
81#define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
82
83
84#endif /* _LINUX_PERCPU_DEFS_H */