include/asm-generic/percpu.h

   1 #ifndef _ASM_GENERIC_PERCPU_H_
   2 #define _ASM_GENERIC_PERCPU_H_
   3 #include <linux/compiler.h>
   4 #include <linux/threads.h>
   5
   6 /*
   7  * Determine the real variable name from the name visible in the
   8  * kernel sources.
   9  */
  10 #define per_cpu_var(var) per_cpu__##var
  11
  12 #ifdef CONFIG_SMP
  13
  14 /*
  15  * per_cpu_offset() is the offset that has to be added to a
  16  * percpu variable to get to the instance for a certain processor.
  17  *
  18  * Most arches use the __per_cpu_offset array for those offsets but
  19  * some arches have their own ways of determining the offset (x86_64, s390).
  20  */
  21 #ifndef __per_cpu_offset
  22 extern unsigned long __per_cpu_offset[NR_CPUS];
  23
  24 #define per_cpu_offset(x) (__per_cpu_offset[x])
  25 #endif
  26
  27 /*
  28  * Determine the offset for the currently active processor.
  29  * An arch may define __my_cpu_offset to provide a more effective
  30  * means of obtaining the offset to the per cpu variables of the
  31  * current processor.
  32  */
  33 #ifndef __my_cpu_offset
  34 #define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())
  35 #define my_cpu_offset per_cpu_offset(smp_processor_id())
  36 #else
  37 #define my_cpu_offset __my_cpu_offset
  38 #endif
  39
  40 /*
  41  * Add a offset to a pointer but keep the pointer as is.
  42  *
  43  * Only S390 provides its own means of moving the pointer.
  44  */
  45 #ifndef SHIFT_PERCPU_PTR
  46 #define SHIFT_PERCPU_PTR(__p, __offset) RELOC_HIDE((__p), (__offset))
  47 #endif
  48
  49 /*
  50  * A percpu variable may point to a discarded regions. The following are
  51  * established ways to produce a usable pointer from the percpu variable
  52  * offset.
  53  */
  54 #define per_cpu(var, cpu) \
  55         (*SHIFT_PERCPU_PTR(&per_cpu_var(var), per_cpu_offset(cpu)))
  56 #define __get_cpu_var(var) \
  57         (*SHIFT_PERCPU_PTR(&per_cpu_var(var), my_cpu_offset))
  58 #define __raw_get_cpu_var(var) \
  59         (*SHIFT_PERCPU_PTR(&per_cpu_var(var), __my_cpu_offset))
  60
  61
  62 #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
  63 extern void setup_per_cpu_areas(void);
  64 #endif
  65
  66 #else /* ! SMP */
  67
  68 #define per_cpu(var, cpu)                       (*((void)(cpu), &per_cpu_var(var)))
  69 #define __get_cpu_var(var)                      per_cpu_var(var)
  70 #define __raw_get_cpu_var(var)                  per_cpu_var(var)
  71
  72 #endif  /* SMP */
  73
  74 #ifndef PER_CPU_ATTRIBUTES
  75 #define PER_CPU_ATTRIBUTES
  76 #endif
  77
  78 #define DECLARE_PER_CPU(type, name) extern PER_CPU_ATTRIBUTES \
  79                                         __typeof__(type) per_cpu_var(name)
  80
  81 #endif /* _ASM_GENERIC_PERCPU_H_ */