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 __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 */