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 */