linux/include/asm-generic/local.h
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   1#ifndef _ASM_GENERIC_LOCAL_H
   2#define _ASM_GENERIC_LOCAL_H
   3
   4#include <linux/percpu.h>
   5#include <linux/atomic.h>
   6#include <asm/types.h>
   7
   8/*
   9 * A signed long type for operations which are atomic for a single CPU.
  10 * Usually used in combination with per-cpu variables.
  11 *
  12 * This is the default implementation, which uses atomic_long_t.  Which is
  13 * rather pointless.  The whole point behind local_t is that some processors
  14 * can perform atomic adds and subtracts in a manner which is atomic wrt IRQs
  15 * running on this CPU.  local_t allows exploitation of such capabilities.
  16 */
  17
  18/* Implement in terms of atomics. */
  19
  20/* Don't use typedef: don't want them to be mixed with atomic_t's. */
  21typedef struct
  22{
  23        atomic_long_t a;
  24} local_t;
  25
  26#define LOCAL_INIT(i)   { ATOMIC_LONG_INIT(i) }
  27
  28#define local_read(l)   atomic_long_read(&(l)->a)
  29#define local_set(l,i)  atomic_long_set((&(l)->a),(i))
  30#define local_inc(l)    atomic_long_inc(&(l)->a)
  31#define local_dec(l)    atomic_long_dec(&(l)->a)
  32#define local_add(i,l)  atomic_long_add((i),(&(l)->a))
  33#define local_sub(i,l)  atomic_long_sub((i),(&(l)->a))
  34
  35#define local_sub_and_test(i, l) atomic_long_sub_and_test((i), (&(l)->a))
  36#define local_dec_and_test(l) atomic_long_dec_and_test(&(l)->a)
  37#define local_inc_and_test(l) atomic_long_inc_and_test(&(l)->a)
  38#define local_add_negative(i, l) atomic_long_add_negative((i), (&(l)->a))
  39#define local_add_return(i, l) atomic_long_add_return((i), (&(l)->a))
  40#define local_sub_return(i, l) atomic_long_sub_return((i), (&(l)->a))
  41#define local_inc_return(l) atomic_long_inc_return(&(l)->a)
  42
  43#define local_cmpxchg(l, o, n) atomic_long_cmpxchg((&(l)->a), (o), (n))
  44#define local_xchg(l, n) atomic_long_xchg((&(l)->a), (n))
  45#define local_add_unless(l, _a, u) atomic_long_add_unless((&(l)->a), (_a), (u))
  46#define local_inc_not_zero(l) atomic_long_inc_not_zero(&(l)->a)
  47
  48/* Non-atomic variants, ie. preemption disabled and won't be touched
  49 * in interrupt, etc.  Some archs can optimize this case well. */
  50#define __local_inc(l)          local_set((l), local_read(l) + 1)
  51#define __local_dec(l)          local_set((l), local_read(l) - 1)
  52#define __local_add(i,l)        local_set((l), local_read(l) + (i))
  53#define __local_sub(i,l)        local_set((l), local_read(l) - (i))
  54
  55#endif /* _ASM_GENERIC_LOCAL_H */
  56
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