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   1 /*
   2  * atomic32.c: 32-bit atomic_t implementation
   3  *
   4  * Copyright (C) 2004 Keith M Wesolowski
   5  *
   6  * Based on asm-parisc/atomic.h Copyright (C) 2000 Philipp Rumpf
   7  */
   8
   9 #include <asm/atomic.h>
  10 #include <linux/spinlock.h>
  11 #include <linux/module.h>
  12
  13 #ifdef CONFIG_SMP
  14 #define ATOMIC_HASH_SIZE        4
  15 #define ATOMIC_HASH(a)  (&__atomic_hash[(((unsigned long)a)>>8) & (ATOMIC_HASH_SIZE-1)])
  16
  17 spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] = {
  18         [0 ... (ATOMIC_HASH_SIZE-1)] = SPIN_LOCK_UNLOCKED
  19 };
  20
  21 #else /* SMP */
  22
  23 static DEFINE_SPINLOCK(dummy);
  24 #define ATOMIC_HASH_SIZE        1
  25 #define ATOMIC_HASH(a)          (&dummy)
  26
  27 #endif /* SMP */
  28
  29 int __atomic_add_return(int i, atomic_t *v)
  30 {
  31         int ret;
  32         unsigned long flags;
  33         spin_lock_irqsave(ATOMIC_HASH(v), flags);
  34
  35         ret = (v->counter += i);
  36
  37         spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
  38         return ret;
  39 }
  40 EXPORT_SYMBOL(__atomic_add_return);
  41
  42 int atomic_cmpxchg(atomic_t *v, int old, int new)
  43 {
  44         int ret;
  45         unsigned long flags;
  46
  47         spin_lock_irqsave(ATOMIC_HASH(v), flags);
  48         ret = v->counter;
  49         if (likely(ret == old))
  50                 v->counter = new;
  51
  52         spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
  53         return ret;
  54 }
  55
  56 int atomic_add_unless(atomic_t *v, int a, int u)
  57 {
  58         int ret;
  59         unsigned long flags;
  60
  61         spin_lock_irqsave(ATOMIC_HASH(v), flags);
  62         ret = v->counter;
  63         if (ret != u)
  64                 v->counter += a;
  65         spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
  66         return ret != u;
  67 }
  68
  69 /* Atomic operations are already serializing */
  70 void atomic_set(atomic_t *v, int i)
  71 {
  72         unsigned long flags;
  73
  74         spin_lock_irqsave(ATOMIC_HASH(v), flags);
  75         v->counter = i;
  76         spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
  77 }
  78 EXPORT_SYMBOL(atomic_set);