include/asm-generic/atomic.h

   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 #include <asm/barrier.h>
  20
  21 /*
  22  * atomic_$op() - $op integer to atomic variable
  23  * @i: integer value to $op
  24  * @v: pointer to the atomic variable
  25  *
  26  * Atomically $ops @i to @v. Does not strictly guarantee a memory-barrier, use
  27  * smp_mb__{before,after}_atomic().
  28  */
  29
  30 /*
  31  * atomic_$op_return() - $op interer to atomic variable and returns the result
  32  * @i: integer value to $op
  33  * @v: pointer to the atomic variable
  34  *
  35  * Atomically $ops @i to @v. Does imply a full memory barrier.
  36  */
  37
  38 #ifdef CONFIG_SMP
  39
  40 /* we can build all atomic primitives from cmpxchg */
  41
  42 #define ATOMIC_OP(op, c_op)                                             \
  43 static inline void atomic_##op(int i, atomic_t *v)                      \
  44 {                                                                       \
  45         int c, old;                                                     \
  46                                                                         \
  47         c = v->counter;                                                 \
  48         while ((old = cmpxchg(&v->counter, c, c c_op i)) != c)          \
  49                 c = old;                                                \
  50 }
  51
  52 #define ATOMIC_OP_RETURN(op, c_op)                                      \
  53 static inline int atomic_##op##_return(int i, atomic_t *v)              \
  54 {                                                                       \
  55         int c, old;                                                     \
  56                                                                         \
  57         c = v->counter;                                                 \
  58         while ((old = cmpxchg(&v->counter, c, c c_op i)) != c)          \
  59                 c = old;                                                \
  60                                                                         \
  61         return c c_op i;                                                \
  62 }
  63
  64 #else
  65
  66 #include <linux/irqflags.h>
  67
  68 #define ATOMIC_OP(op, c_op)                                             \
  69 static inline void atomic_##op(int i, atomic_t *v)                      \
  70 {                                                                       \
  71         unsigned long flags;                                            \
  72                                                                         \
  73         raw_local_irq_save(flags);                                      \
  74         v->counter = v->counter c_op i;                                 \
  75         raw_local_irq_restore(flags);                                   \
  76 }
  77
  78 #define ATOMIC_OP_RETURN(op, c_op)                                      \
  79 static inline int atomic_##op##_return(int i, atomic_t *v)              \
  80 {                                                                       \
  81         unsigned long flags;                                            \
  82         int ret;                                                        \
  83                                                                         \
  84         raw_local_irq_save(flags);                                      \
  85         ret = (v->counter = v->counter c_op i);                         \
  86         raw_local_irq_restore(flags);                                   \
  87                                                                         \
  88         return ret;                                                     \
  89 }
  90
  91 #endif /* CONFIG_SMP */
  92
  93 #ifndef atomic_add_return
  94 ATOMIC_OP_RETURN(add, +)
  95 #endif
  96
  97 #ifndef atomic_sub_return
  98 ATOMIC_OP_RETURN(sub, -)
  99 #endif
 100
 101 #ifndef atomic_and
 102 ATOMIC_OP(and, &)
 103 #endif
 104
 105 #ifndef atomic_or
 106 ATOMIC_OP(or, |)
 107 #endif
 108
 109 #ifndef atomic_xor
 110 ATOMIC_OP(xor, ^)
 111 #endif
 112
 113 #undef ATOMIC_OP_RETURN
 114 #undef ATOMIC_OP
 115
 116 /*
 117  * Atomic operations that C can't guarantee us.  Useful for
 118  * resource counting etc..
 119  */
 120
 121 #define ATOMIC_INIT(i)  { (i) }
 122
 123 /**
 124  * atomic_read - read atomic variable
 125  * @v: pointer of type atomic_t
 126  *
 127  * Atomically reads the value of @v.
 128  */
 129 #ifndef atomic_read
 130 #define atomic_read(v)  READ_ONCE((v)->counter)
 131 #endif
 132
 133 /**
 134  * atomic_set - set atomic variable
 135  * @v: pointer of type atomic_t
 136  * @i: required value
 137  *
 138  * Atomically sets the value of @v to @i.
 139  */
 140 #define atomic_set(v, i) WRITE_ONCE(((v)->counter), (i))
 141
 142 #include <linux/irqflags.h>
 143
 144 static inline int atomic_add_negative(int i, atomic_t *v)
 145 {
 146         return atomic_add_return(i, v) < 0;
 147 }
 148
 149 static inline void atomic_add(int i, atomic_t *v)
 150 {
 151         atomic_add_return(i, v);
 152 }
 153
 154 static inline void atomic_sub(int i, atomic_t *v)
 155 {
 156         atomic_sub_return(i, v);
 157 }
 158
 159 static inline void atomic_inc(atomic_t *v)
 160 {
 161         atomic_add_return(1, v);
 162 }
 163
 164 static inline void atomic_dec(atomic_t *v)
 165 {
 166         atomic_sub_return(1, v);
 167 }
 168
 169 #define atomic_dec_return(v)            atomic_sub_return(1, (v))
 170 #define atomic_inc_return(v)            atomic_add_return(1, (v))
 171
 172 #define atomic_sub_and_test(i, v)       (atomic_sub_return((i), (v)) == 0)
 173 #define atomic_dec_and_test(v)          (atomic_dec_return(v) == 0)
 174 #define atomic_inc_and_test(v)          (atomic_inc_return(v) == 0)
 175
 176 #define atomic_xchg(ptr, v)             (xchg(&(ptr)->counter, (v)))
 177 #define atomic_cmpxchg(v, old, new)     (cmpxchg(&((v)->counter), (old), (new)))
 178
 179 static inline int __atomic_add_unless(atomic_t *v, int a, int u)
 180 {
 181         int c, old;
 182         c = atomic_read(v);
 183         while (c != u && (old = atomic_cmpxchg(v, c, c + a)) != c)
 184                 c = old;
 185         return c;
 186 }
 187
 188 #endif /* __ASM_GENERIC_ATOMIC_H */