include/asm-generic/atomic.h

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