linux/include/asm-generic/atomic.h
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   1/*
   2 * Generic C implementation of atomic counter operations. Usable on
   3 * UP systems only. Do not include in machine independent code.
   4 *
   5 * Originally implemented for MN10300.
   6 *
   7 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   8 * Written by David Howells (dhowells@redhat.com)
   9 *
  10 * This program is free software; you can redistribute it and/or
  11 * modify it under the terms of the GNU General Public Licence
  12 * as published by the Free Software Foundation; either version
  13 * 2 of the Licence, or (at your option) any later version.
  14 */
  15#ifndef __ASM_GENERIC_ATOMIC_H
  16#define __ASM_GENERIC_ATOMIC_H
  17
  18#include <asm/cmpxchg.h>
  19
  20#ifdef CONFIG_SMP
  21/* Force people to define core atomics */
  22# if !defined(atomic_add_return) || !defined(atomic_sub_return) || \
  23     !defined(atomic_clear_mask) || !defined(atomic_set_mask)
  24#  error "SMP requires a little arch-specific magic"
  25# endif
  26#endif
  27
  28/*
  29 * Atomic operations that C can't guarantee us.  Useful for
  30 * resource counting etc..
  31 */
  32
  33#define ATOMIC_INIT(i)  { (i) }
  34
  35#ifdef __KERNEL__
  36
  37/**
  38 * atomic_read - read atomic variable
  39 * @v: pointer of type atomic_t
  40 *
  41 * Atomically reads the value of @v.
  42 */
  43#ifndef atomic_read
  44#define atomic_read(v)  (*(volatile int *)&(v)->counter)
  45#endif
  46
  47/**
  48 * atomic_set - set atomic variable
  49 * @v: pointer of type atomic_t
  50 * @i: required value
  51 *
  52 * Atomically sets the value of @v to @i.
  53 */
  54#define atomic_set(v, i) (((v)->counter) = (i))
  55
  56#include <linux/irqflags.h>
  57
  58/**
  59 * atomic_add_return - add integer to atomic variable
  60 * @i: integer value to add
  61 * @v: pointer of type atomic_t
  62 *
  63 * Atomically adds @i to @v and returns the result
  64 */
  65#ifndef atomic_add_return
  66static inline int atomic_add_return(int i, atomic_t *v)
  67{
  68        unsigned long flags;
  69        int temp;
  70
  71        raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
  72        temp = v->counter;
  73        temp += i;
  74        v->counter = temp;
  75        raw_local_irq_restore(flags);
  76
  77        return temp;
  78}
  79#endif
  80
  81/**
  82 * atomic_sub_return - subtract integer from atomic variable
  83 * @i: integer value to subtract
  84 * @v: pointer of type atomic_t
  85 *
  86 * Atomically subtracts @i from @v and returns the result
  87 */
  88#ifndef atomic_sub_return
  89static inline int atomic_sub_return(int i, atomic_t *v)
  90{
  91        unsigned long flags;
  92        int temp;
  93
  94        raw_local_irq_save(flags); /* Don't trace it in an irqsoff handler */
  95        temp = v->counter;
  96        temp -= i;
  97        v->counter = temp;
  98        raw_local_irq_restore(flags);
  99
 100        return temp;
 101}
 102#endif
 103
 104static inline int atomic_add_negative(int i, atomic_t *v)
 105{
 106        return atomic_add_return(i, v) < 0;
 107}
 108
 109static inline void atomic_add(int i, atomic_t *v)
 110{
 111        atomic_add_return(i, v);
 112}
 113
 114static inline void atomic_sub(int i, atomic_t *v)
 115{
 116        atomic_sub_return(i, v);
 117}
 118
 119static inline void atomic_inc(atomic_t *v)
 120{
 121        atomic_add_return(1, v);
 122}
 123
 124static inline void atomic_dec(atomic_t *v)
 125{
 126        atomic_sub_return(1, v);
 127}
 128
 129#define atomic_dec_return(v)            atomic_sub_return(1, (v))
 130#define atomic_inc_return(v)            atomic_add_return(1, (v))
 131
 132#define atomic_sub_and_test(i, v)       (atomic_sub_return((i), (v)) == 0)
 133#define atomic_dec_and_test(v)          (atomic_dec_return(v) == 0)
 134#define atomic_inc_and_test(v)          (atomic_inc_return(v) == 0)
 135
 136#define atomic_xchg(ptr, v)             (xchg(&(ptr)->counter, (v)))
 137#define atomic_cmpxchg(v, old, new)     (cmpxchg(&((v)->counter), (old), (new)))
 138
 139#define cmpxchg_local(ptr, o, n)                                               \
 140        ((__typeof__(*(ptr)))__cmpxchg_local_generic((ptr), (unsigned long)(o),\
 141                        (unsigned long)(n), sizeof(*(ptr))))
 142
 143#define cmpxchg64_local(ptr, o, n) __cmpxchg64_local_generic((ptr), (o), (n))
 144
 145static inline int __atomic_add_unless(atomic_t *v, int a, int u)
 146{
 147  int c, old;
 148  c = atomic_read(v);
 149  while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
 150    c = old;
 151  return c;
 152}
 153
 154/**
 155 * atomic_clear_mask - Atomically clear bits in atomic variable
 156 * @mask: Mask of the bits to be cleared
 157 * @v: pointer of type atomic_t
 158 *
 159 * Atomically clears the bits set in @mask from @v
 160 */
 161#ifndef atomic_clear_mask
 162static inline void atomic_clear_mask(unsigned long mask, atomic_t *v)
 163{
 164        unsigned long flags;
 165
 166        mask = ~mask;
 167        raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
 168        v->counter &= mask;
 169        raw_local_irq_restore(flags);
 170}
 171#endif
 172
 173/**
 174 * atomic_set_mask - Atomically set bits in atomic variable
 175 * @mask: Mask of the bits to be set
 176 * @v: pointer of type atomic_t
 177 *
 178 * Atomically sets the bits set in @mask in @v
 179 */
 180#ifndef atomic_set_mask
 181static inline void atomic_set_mask(unsigned int mask, atomic_t *v)
 182{
 183        unsigned long flags;
 184
 185        raw_local_irq_save(flags); /* Don't trace it in a irqsoff handler */
 186        v->counter |= mask;
 187        raw_local_irq_restore(flags);
 188}
 189#endif
 190
 191/* Assume that atomic operations are already serializing */
 192#define smp_mb__before_atomic_dec()     barrier()
 193#define smp_mb__after_atomic_dec()      barrier()
 194#define smp_mb__before_atomic_inc()     barrier()
 195#define smp_mb__after_atomic_inc()      barrier()
 196
 197#endif /* __KERNEL__ */
 198#endif /* __ASM_GENERIC_ATOMIC_H */
 199
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