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 #define __per_cpu_var_lock(var) per_cpu__lock_##var##_locked
  13 #define __per_cpu_var_lock_var(var) per_cpu__##var##_locked
  14
  15 #ifdef CONFIG_SMP
  16
  17 /*
  18  * per_cpu_offset() is the offset that has to be added to a
  19  * percpu variable to get to the instance for a certain processor.
  20  *
  21  * Most arches use the __per_cpu_offset array for those offsets but
  22  * some arches have their own ways of determining the offset (x86_64, s390).
  23  */
  24 #ifndef __per_cpu_offset
  25 extern unsigned long __per_cpu_offset[NR_CPUS];
  26
  27 #define per_cpu_offset(x) (__per_cpu_offset[x])
  28 #endif
  29
  30 /*
  31  * Determine the offset for the currently active processor.
  32  * An arch may define __my_cpu_offset to provide a more effective
  33  * means of obtaining the offset to the per cpu variables of the
  34  * current processor.
  35  */
  36 #ifndef __my_cpu_offset
  37 #define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())
  38 #endif
  39 #ifdef CONFIG_DEBUG_PREEMPT
  40 #define my_cpu_offset per_cpu_offset(smp_processor_id())
  41 #else
  42 #define my_cpu_offset __my_cpu_offset
  43 #endif
  44
  45 /*
  46  * Add a offset to a pointer but keep the pointer as is.
  47  *
  48  * Only S390 provides its own means of moving the pointer.
  49  */
  50 #ifndef SHIFT_PERCPU_PTR
  51 #define SHIFT_PERCPU_PTR(__p, __offset) RELOC_HIDE((__p), (__offset))
  52 #endif
  53
  54 /*
  55  * A percpu variable may point to a discarded regions. The following are
  56  * established ways to produce a usable pointer from the percpu variable
  57  * offset.
  58  */
  59 #define per_cpu(var, cpu) \
  60         (*SHIFT_PERCPU_PTR(&per_cpu_var(var), per_cpu_offset(cpu)))
  61 #define __get_cpu_var(var) \
  62         (*SHIFT_PERCPU_PTR(&per_cpu_var(var), my_cpu_offset))
  63 #define __raw_get_cpu_var(var) \
  64         (*SHIFT_PERCPU_PTR(&per_cpu_var(var), __my_cpu_offset))
  65
  66 #define per_cpu_lock(var, cpu) \
  67         (*SHIFT_PERCPU_PTR(&__per_cpu_var_lock(var), per_cpu_offset(cpu)))
  68 #define per_cpu_var_locked(var, cpu) \
  69         (*SHIFT_PERCPU_PTR(&__per_cpu_var_lock_var(var), per_cpu_offset(cpu)))
  70 #define __get_cpu_lock(var, cpu) \
  71                 per_cpu_lock(var, cpu)
  72 #define __get_cpu_var_locked(var, cpu) \
  73                 per_cpu_var_locked(var, cpu)
  74
  75 #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
  76 extern void setup_per_cpu_areas(void);
  77 #endif
  78
  79 #else /* ! SMP */
  80
  81 #define per_cpu(var, cpu)                       (*((void)(cpu), &per_cpu_var(var)))
  82 #define per_cpu_var_locked(var, cpu)            (*((void)(cpu), &__per_cpu_var_lock_var(var)))
  83 #define __get_cpu_var(var)                      per_cpu_var(var)
  84 #define __raw_get_cpu_var(var)                  per_cpu_var(var)
  85 #define __get_cpu_lock(var, cpu)                __per_cpu_var_lock(var)
  86 #define __get_cpu_var_locked(var, cpu)          __per_cpu_var_lock_var(var)
  87 #endif  /* SMP */
  88
  89 #ifndef PER_CPU_ATTRIBUTES
  90 #define PER_CPU_ATTRIBUTES
  91 #endif
  92
  93 #define DECLARE_PER_CPU(type, name) extern PER_CPU_ATTRIBUTES \
  94                                         __typeof__(type) per_cpu_var(name)
  95 #define DECLARE_PER_CPU_LOCKED(type, name)                                      \
  96         extern PER_CPU_ATTRIBUTES spinlock_t __per_cpu_var_lock(name);          \
  97         extern PER_CPU_ATTRIBUTES __typeof__(type) __per_cpu_var_lock_var(name)
  98
  99 /*
 100  * Optional methods for optimized non-lvalue per-cpu variable access.
 101  *
 102  * @var can be a percpu variable or a field of it and its size should
 103  * equal char, int or long.  percpu_read() evaluates to a lvalue and
 104  * all others to void.
 105  *
 106  * These operations are guaranteed to be atomic w.r.t. preemption.
 107  * The generic versions use plain get/put_cpu_var().  Archs are
 108  * encouraged to implement single-instruction alternatives which don't
 109  * require preemption protection.
 110  */
 111 #ifndef percpu_read
 112 # define percpu_read(var)                                               \
 113   ({                                                                    \
 114         typeof(per_cpu_var(var)) __tmp_var__;                           \
 115         __tmp_var__ = get_cpu_var(var);                                 \
 116         put_cpu_var(var);                                               \
 117         __tmp_var__;                                                    \
 118   })
 119 #endif
 120
 121 #define __percpu_generic_to_op(var, val, op)                            \
 122 do {                                                                    \
 123         get_cpu_var(var) op val;                                        \
 124         put_cpu_var(var);                                               \
 125 } while (0)
 126
 127 #ifndef percpu_write
 128 # define percpu_write(var, val)         __percpu_generic_to_op(var, (val), =)
 129 #endif
 130
 131 #ifndef percpu_add
 132 # define percpu_add(var, val)           __percpu_generic_to_op(var, (val), +=)
 133 #endif
 134
 135 #ifndef percpu_sub
 136 # define percpu_sub(var, val)           __percpu_generic_to_op(var, (val), -=)
 137 #endif
 138
 139 #ifndef percpu_and
 140 # define percpu_and(var, val)           __percpu_generic_to_op(var, (val), &=)
 141 #endif
 142
 143 #ifndef percpu_or
 144 # define percpu_or(var, val)            __percpu_generic_to_op(var, (val), |=)
 145 #endif
 146
 147 #ifndef percpu_xor
 148 # define percpu_xor(var, val)           __percpu_generic_to_op(var, (val), ^=)
 149 #endif
 150
 151 #endif /* _ASM_GENERIC_PERCPU_H_ */