Merge branch 'for-linus' of git://git.infradead.org/users/eparis/notify
[linux-2.6.git] / include / linux / percpu-defs.h
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
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 PER_CPU_DEF_ATTRIBUTES                       \
28         __typeof__(type) per_cpu__##name
29
30 /*
31  * Variant on the per-CPU variable declaration/definition theme used for
32  * ordinary per-CPU variables.
33  */
34 #define DECLARE_PER_CPU(type, name)                                     \
35         DECLARE_PER_CPU_SECTION(type, name, "")
36
37 #define DEFINE_PER_CPU(type, name)                                      \
38         DEFINE_PER_CPU_SECTION(type, name, "")
39
40 /*
41  * Declaration/definition used for per-CPU variables that must come first in
42  * the set of variables.
43  */
44 #define DECLARE_PER_CPU_FIRST(type, name)                               \
45         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
46
47 #define DEFINE_PER_CPU_FIRST(type, name)                                \
48         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_FIRST_SECTION)
49
50 /*
51  * Declaration/definition used for per-CPU variables that must be cacheline
52  * aligned under SMP conditions so that, whilst a particular instance of the
53  * data corresponds to a particular CPU, inefficiencies due to direct access by
54  * other CPUs are reduced by preventing the data from unnecessarily spanning
55  * cachelines.
56  *
57  * An example of this would be statistical data, where each CPU's set of data
58  * is updated by that CPU alone, but the data from across all CPUs is collated
59  * by a CPU processing a read from a proc file.
60  */
61 #define DECLARE_PER_CPU_SHARED_ALIGNED(type, name)                      \
62         DECLARE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
63         ____cacheline_aligned_in_smp
64
65 #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name)                       \
66         DEFINE_PER_CPU_SECTION(type, name, PER_CPU_SHARED_ALIGNED_SECTION) \
67         ____cacheline_aligned_in_smp
68
69 /*
70  * Declaration/definition used for per-CPU variables that must be page aligned.
71  */
72 #define DECLARE_PER_CPU_PAGE_ALIGNED(type, name)                                \
73         DECLARE_PER_CPU_SECTION(type, name, ".page_aligned")
74
75 #define DEFINE_PER_CPU_PAGE_ALIGNED(type, name)                         \
76         DEFINE_PER_CPU_SECTION(type, name, ".page_aligned")
77
78 /*
79  * Intermodule exports for per-CPU variables.
80  */
81 #define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var)
82 #define EXPORT_PER_CPU_SYMBOL_GPL(var) EXPORT_SYMBOL_GPL(per_cpu__##var)
83
84
85 #endif /* _LINUX_PERCPU_DEFS_H */