include/asm-generic/local.h

   1 #ifndef _ASM_GENERIC_LOCAL_H
   2 #define _ASM_GENERIC_LOCAL_H
   3
   4 #include <linux/config.h>
   5 #include <linux/percpu.h>
   6 #include <linux/hardirq.h>
   7 #include <asm/atomic.h>
   8 #include <asm/types.h>
   9
  10 /*
  11  * A signed long type for operations which are atomic for a single CPU.
  12  * Usually used in combination with per-cpu variables.
  13  *
  14  * This is the default implementation, which uses atomic_long_t.  Which is
  15  * rather pointless.  The whole point behind local_t is that some processors
  16  * can perform atomic adds and subtracts in a manner which is atomic wrt IRQs
  17  * running on this CPU.  local_t allows exploitation of such capabilities.
  18  */
  19
  20 /* Implement in terms of atomics. */
  21
  22 /* Don't use typedef: don't want them to be mixed with atomic_t's. */
  23 typedef struct
  24 {
  25         atomic_long_t a;
  26 } local_t;
  27
  28 #define LOCAL_INIT(i)   { ATOMIC_LONG_INIT(i) }
  29
  30 #define local_read(l)   atomic_long_read(&(l)->a)
  31 #define local_set(l,i)  atomic_long_set((&(l)->a),(i))
  32 #define local_inc(l)    atomic_long_inc(&(l)->a)
  33 #define local_dec(l)    atomic_long_dec(&(l)->a)
  34 #define local_add(i,l)  atomic_long_add((i),(&(l)->a))
  35 #define local_sub(i,l)  atomic_long_sub((i),(&(l)->a))
  36
  37 /* Non-atomic variants, ie. preemption disabled and won't be touched
  38  * in interrupt, etc.  Some archs can optimize this case well. */
  39 #define __local_inc(l)          local_set((l), local_read(l) + 1)
  40 #define __local_dec(l)          local_set((l), local_read(l) - 1)
  41 #define __local_add(i,l)        local_set((l), local_read(l) + (i))
  42 #define __local_sub(i,l)        local_set((l), local_read(l) - (i))
  43
  44 /* Use these for per-cpu local_t variables: on some archs they are
  45  * much more efficient than these naive implementations.  Note they take
  46  * a variable (eg. mystruct.foo), not an address.
  47  */
  48 #define cpu_local_read(v)       local_read(&__get_cpu_var(v))
  49 #define cpu_local_set(v, i)     local_set(&__get_cpu_var(v), (i))
  50 #define cpu_local_inc(v)        local_inc(&__get_cpu_var(v))
  51 #define cpu_local_dec(v)        local_dec(&__get_cpu_var(v))
  52 #define cpu_local_add(i, v)     local_add((i), &__get_cpu_var(v))
  53 #define cpu_local_sub(i, v)     local_sub((i), &__get_cpu_var(v))
  54
  55 /* Non-atomic increments, ie. preemption disabled and won't be touched
  56  * in interrupt, etc.  Some archs can optimize this case well.
  57  */
  58 #define __cpu_local_inc(v)      __local_inc(&__get_cpu_var(v))
  59 #define __cpu_local_dec(v)      __local_dec(&__get_cpu_var(v))
  60 #define __cpu_local_add(i, v)   __local_add((i), &__get_cpu_var(v))
  61 #define __cpu_local_sub(i, v)   __local_sub((i), &__get_cpu_var(v))
  62
  63 #endif /* _ASM_GENERIC_LOCAL_H */