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atomic32.c

/*
 * atomic32.c: 32-bit atomic_t implementation
 *
 * Copyright (C) 2004 Keith M Wesolowski
 * Copyright (C) 2007 Kyle McMartin
 * 
 * Based on asm-parisc/atomic.h Copyright (C) 2000 Philipp Rumpf
 */

#include <asm/atomic.h>
#include <linux/spinlock.h>
#include <linux/module.h>

#ifdef CONFIG_SMP
#define ATOMIC_HASH_SIZE      4
#define ATOMIC_HASH(a)  (&__atomic_hash[(((unsigned long)a)>>8) & (ATOMIC_HASH_SIZE-1)])

spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] = {
      [0 ... (ATOMIC_HASH_SIZE-1)] = SPIN_LOCK_UNLOCKED
};

#else /* SMP */

static DEFINE_SPINLOCK(dummy);
#define ATOMIC_HASH_SIZE      1
#define ATOMIC_HASH(a)        (&dummy)

#endif /* SMP */

int __atomic_add_return(int i, atomic_t *v)
{
      int ret;
      unsigned long flags;
      spin_lock_irqsave(ATOMIC_HASH(v), flags);

      ret = (v->counter += i);

      spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
      return ret;
}
EXPORT_SYMBOL(__atomic_add_return);

int atomic_cmpxchg(atomic_t *v, int old, int new)
{
      int ret;
      unsigned long flags;

      spin_lock_irqsave(ATOMIC_HASH(v), flags);
      ret = v->counter;
      if (likely(ret == old))
            v->counter = new;

      spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
      return ret;
}
EXPORT_SYMBOL(atomic_cmpxchg);

int atomic_add_unless(atomic_t *v, int a, int u)
{
      int ret;
      unsigned long flags;

      spin_lock_irqsave(ATOMIC_HASH(v), flags);
      ret = v->counter;
      if (ret != u)
            v->counter += a;
      spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
      return ret != u;
}
EXPORT_SYMBOL(atomic_add_unless);

/* Atomic operations are already serializing */
void atomic_set(atomic_t *v, int i)
{
      unsigned long flags;

      spin_lock_irqsave(ATOMIC_HASH(v), flags);
      v->counter = i;
      spin_unlock_irqrestore(ATOMIC_HASH(v), flags);
}
EXPORT_SYMBOL(atomic_set);

unsigned long ___set_bit(unsigned long *addr, unsigned long mask)
{
      unsigned long old, flags;

      spin_lock_irqsave(ATOMIC_HASH(addr), flags);
      old = *addr;
      *addr = old | mask;
      spin_unlock_irqrestore(ATOMIC_HASH(addr), flags);

      return old & mask;
}
EXPORT_SYMBOL(___set_bit);

unsigned long ___clear_bit(unsigned long *addr, unsigned long mask)
{
      unsigned long old, flags;

      spin_lock_irqsave(ATOMIC_HASH(addr), flags);
      old = *addr;
      *addr = old & ~mask;
      spin_unlock_irqrestore(ATOMIC_HASH(addr), flags);

      return old & mask;
}
EXPORT_SYMBOL(___clear_bit);

unsigned long ___change_bit(unsigned long *addr, unsigned long mask)
{
      unsigned long old, flags;

      spin_lock_irqsave(ATOMIC_HASH(addr), flags);
      old = *addr;
      *addr = old ^ mask;
      spin_unlock_irqrestore(ATOMIC_HASH(addr), flags);

      return old & mask;
}
EXPORT_SYMBOL(___change_bit);

unsigned long __cmpxchg_u32(volatile u32 *ptr, u32 old, u32 new)
{
      unsigned long flags;
      u32 prev;

      spin_lock_irqsave(ATOMIC_HASH(ptr), flags);
      if ((prev = *ptr) == old)
            *ptr = new;
      spin_unlock_irqrestore(ATOMIC_HASH(ptr), flags);

      return (unsigned long)prev;
}
EXPORT_SYMBOL(__cmpxchg_u32);

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