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 #endif
  36 #ifdef CONFIG_DEBUG_PREEMPT
  37 #define my_cpu_offset per_cpu_offset(smp_processor_id())
  38 #else
  39 #define my_cpu_offset __my_cpu_offset
  40 #endif
  41
  42 /*
  43  * Add a offset to a pointer but keep the pointer as is.
  44  *
  45  * Only S390 provides its own means of moving the pointer.
  46  */
  47 #ifndef SHIFT_PERCPU_PTR
  48 #define SHIFT_PERCPU_PTR(__p, __offset) RELOC_HIDE((__p), (__offset))
  49 #endif
  50
  51 /*
  52  * A percpu variable may point to a discarded regions. The following are
  53  * established ways to produce a usable pointer from the percpu variable
  54  * offset.
  55  */
  56 #define per_cpu(var, cpu) \
  57         (*SHIFT_PERCPU_PTR(&per_cpu_var(var), per_cpu_offset(cpu)))
  58 #define __get_cpu_var(var) \
  59         (*SHIFT_PERCPU_PTR(&per_cpu_var(var), my_cpu_offset))
  60 #define __raw_get_cpu_var(var) \
  61         (*SHIFT_PERCPU_PTR(&per_cpu_var(var), __my_cpu_offset))
  62
  63
  64 #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
  65 extern void setup_per_cpu_areas(void);
  66 #endif
  67
  68 #else /* ! SMP */
  69
  70 #define per_cpu(var, cpu)                       (*((void)(cpu), &per_cpu_var(var)))
  71 #define __get_cpu_var(var)                      per_cpu_var(var)
  72 #define __raw_get_cpu_var(var)                  per_cpu_var(var)
  73
  74 #endif  /* SMP */
  75
  76 #ifndef PER_CPU_ATTRIBUTES
  77 #define PER_CPU_ATTRIBUTES
  78 #endif
  79
  80 #define DECLARE_PER_CPU(type, name) extern PER_CPU_ATTRIBUTES \
  81                                         __typeof__(type) per_cpu_var(name)
  82
  83 /*
  84  * Optional methods for optimized non-lvalue per-cpu variable access.
  85  *
  86  * @var can be a percpu variable or a field of it and its size should
  87  * equal char, int or long.  percpu_read() evaluates to a lvalue and
  88  * all others to void.
  89  *
  90  * These operations are guaranteed to be atomic w.r.t. preemption.
  91  * The generic versions use plain get/put_cpu_var().  Archs are
  92  * encouraged to implement single-instruction alternatives which don't
  93  * require preemption protection.
  94  */
  95 #ifndef percpu_read
  96 # define percpu_read(var)                                               \
  97   ({                                                                    \
  98         typeof(per_cpu_var(var)) __tmp_var__;                           \
  99         __tmp_var__ = get_cpu_var(var);                                 \
 100         put_cpu_var(var);                                               \
 101         __tmp_var__;                                                    \
 102   })
 103 #endif
 104
 105 #define __percpu_generic_to_op(var, val, op)                            \
 106 do {                                                                    \
 107         get_cpu_var(var) op val;                                        \
 108         put_cpu_var(var);                                               \
 109 } while (0)
 110
 111 #ifndef percpu_write
 112 # define percpu_write(var, val)         __percpu_generic_to_op(var, (val), =)
 113 #endif
 114
 115 #ifndef percpu_add
 116 # define percpu_add(var, val)           __percpu_generic_to_op(var, (val), +=)
 117 #endif
 118
 119 #ifndef percpu_sub
 120 # define percpu_sub(var, val)           __percpu_generic_to_op(var, (val), -=)
 121 #endif
 122
 123 #ifndef percpu_and
 124 # define percpu_and(var, val)           __percpu_generic_to_op(var, (val), &=)
 125 #endif
 126
 127 #ifndef percpu_or
 128 # define percpu_or(var, val)            __percpu_generic_to_op(var, (val), |=)
 129 #endif
 130
 131 #ifndef percpu_xor
 132 # define percpu_xor(var, val)           __percpu_generic_to_op(var, (val), ^=)
 133 #endif
 134
 135 #endif /* _ASM_GENERIC_PERCPU_H_ */