arch/alpha/include/asm/atomic.h

#ifndef _ALPHA_ATOMIC_H
#define _ALPHA_ATOMIC_H

#include <linux/types.h>
#include <asm/barrier.h>

/*
 * Atomic operations that C can't guarantee us.  Useful for
 * resource counting etc...
 *
 * But use these as seldom as possible since they are much slower
 * than regular operations.
 */


#define ATOMIC_INIT(i)		( (atomic_t) { (i) } )
#define ATOMIC64_INIT(i)	( (atomic64_t) { (i) } )

#define atomic_read(v)		(*(volatile int *)&(v)->counter)
#define atomic64_read(v)	(*(volatile long *)&(v)->counter)

#define atomic_set(v,i)		((v)->counter = (i))
#define atomic64_set(v,i)	((v)->counter = (i))

/*
 * To get proper branch prediction for the main line, we must branch
 * forward to code at the end of this object's .text section, then
 * branch back to restart the operation.
 */

static __inline__ void atomic_add(int i, atomic_t * v)
{
	unsigned long temp;
	__asm__ __volatile__(
	"1:	ldl_l %0,%1\n"
	"	addl %0,%2,%0\n"
	"	stl_c %0,%1\n"
	"	beq %0,2f\n"
	".subsection 2\n"
	"2:	br 1b\n"
	".previous"
	:"=&r" (temp), "=m" (v->counter)
	:"Ir" (i), "m" (v->counter));
}

static __inline__ void atomic64_add(long i, atomic64_t * v)
{
	unsigned long temp;
	__asm__ __volatile__(
	"1:	ldq_l %0,%1\n"
	"	addq %0,%2,%0\n"
	"	stq_c %0,%1\n"
	"	beq %0,2f\n"
	".subsection 2\n"
	"2:	br 1b\n"
	".previous"
	:"=&r" (temp), "=m" (v->counter)
	:"Ir" (i), "m" (v->counter));
}

static __inline__ void atomic_sub(int i, atomic_t * v)
{
	unsigned long temp;
	__asm__ __volatile__(
	"1:	ldl_l %0,%1\n"
	"	subl %0,%2,%0\n"
	"	stl_c %0,%1\n"
	"	beq %0,2f\n"
	".subsection 2\n"
	"2:	br 1b\n"
	".previous"
	:"=&r" (temp), "=m" (v->counter)
	:"Ir" (i), "m" (v->counter));
}

static __inline__ void atomic64_sub(long i, atomic64_t * v)
{
	unsigned long temp;
	__asm__ __volatile__(
	"1:	ldq_l %0,%1\n"
	"	subq %0,%2,%0\n"
	"	stq_c %0,%1\n"
	"	beq %0,2f\n"
	".subsection 2\n"
	"2:	br 1b\n"
	".previous"
	:"=&r" (temp), "=m" (v->counter)
	:"Ir" (i), "m" (v->counter));
}


/*
 * Same as above, but return the result value
 */
static inline int atomic_add_return(int i, atomic_t *v)
{
	long temp, result;
	smp_mb();
	__asm__ __volatile__(
	"1:	ldl_l %0,%1\n"
	"	addl %0,%3,%2\n"
	"	addl %0,%3,%0\n"
	"	stl_c %0,%1\n"
	"	beq %0,2f\n"
	".subsection 2\n"
	"2:	br 1b\n"
	".previous"
	:"=&r" (temp), "=m" (v->counter), "=&r" (result)
	:"Ir" (i), "m" (v->counter) : "memory");
	smp_mb();
	return result;
}

static __inline__ long atomic64_add_return(long i, atomic64_t * v)
{
	long temp, result;
	smp_mb();
	__asm__ __volatile__(
	"1:	ldq_l %0,%1\n"
	"	addq %0,%3,%2\n"
	"	addq %0,%3,%0\n"
	"	stq_c %0,%1\n"
	"	beq %0,2f\n"
	".subsection 2\n"
	"2:	br 1b\n"
	".previous"
	:"=&r" (temp), "=m" (v->counter), "=&r" (result)
	:"Ir" (i), "m" (v->counter) : "memory");
	smp_mb();
	return result;
}

static __inline__ long atomic_sub_return(int i, atomic_t * v)
{
	long temp, result;
	smp_mb();
	__asm__ __volatile__(
	"1:	ldl_l %0,%1\n"
	"	subl %0,%3,%2\n"
	"	subl %0,%3,%0\n"
	"	stl_c %0,%1\n"
	"	beq %0,2f\n"
	".subsection 2\n"
	"2:	br 1b\n"
	".previous"
	:"=&r" (temp), "=m" (v->counter), "=&r" (result)
	:"Ir" (i), "m" (v->counter) : "memory");
	smp_mb();
	return result;
}

static __inline__ long atomic64_sub_return(long i, atomic64_t * v)
{
	long temp, result;
	smp_mb();
	__asm__ __volatile__(
	"1:	ldq_l %0,%1\n"
	"	subq %0,%3,%2\n"
	"	subq %0,%3,%0\n"
	"	stq_c %0,%1\n"
	"	beq %0,2f\n"
	".subsection 2\n"
	"2:	br 1b\n"
	".previous"
	:"=&r" (temp), "=m" (v->counter), "=&r" (result)
	:"Ir" (i), "m" (v->counter) : "memory");
	smp_mb();
	return result;
}

/*
 * Atomic exchange routines.
 */

#define __ASM__MB
#define ____xchg(type, args...)		__xchg ## type ## _local(args)
#define ____cmpxchg(type, args...)	__cmpxchg ## type ## _local(args)
#include <asm/xchg.h>

#define xchg_local(ptr,x)						\
  ({									\
     __typeof__(*(ptr)) _x_ = (x);					\
     (__typeof__(*(ptr))) __xchg_local((ptr), (unsigned long)_x_,	\
				       sizeof(*(ptr)));			\
  })

#define cmpxchg_local(ptr, o, n)					\
  ({									\
     __typeof__(*(ptr)) _o_ = (o);					\
     __typeof__(*(ptr)) _n_ = (n);					\
     (__typeof__(*(ptr))) __cmpxchg_local((ptr), (unsigned long)_o_,	\
					  (unsigned long)_n_,		\
					  sizeof(*(ptr)));		\
  })

#define cmpxchg64_local(ptr, o, n)					\
  ({									\
	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
	cmpxchg_local((ptr), (o), (n));					\
  })

#ifdef CONFIG_SMP
#undef __ASM__MB
#define __ASM__MB	"\tmb\n"
#endif
#undef ____xchg
#undef ____cmpxchg
#define ____xchg(type, args...)		__xchg ##type(args)
#define ____cmpxchg(type, args...)	__cmpxchg ##type(args)
#include <asm/xchg.h>

#define xchg(ptr,x)							\
  ({									\
     __typeof__(*(ptr)) _x_ = (x);					\
     (__typeof__(*(ptr))) __xchg((ptr), (unsigned long)_x_,		\
				 sizeof(*(ptr)));			\
  })

#define cmpxchg(ptr, o, n)						\
  ({									\
     __typeof__(*(ptr)) _o_ = (o);					\
     __typeof__(*(ptr)) _n_ = (n);					\
     (__typeof__(*(ptr))) __cmpxchg((ptr), (unsigned long)_o_,		\
				    (unsigned long)_n_,	sizeof(*(ptr)));\
  })

#define cmpxchg64(ptr, o, n)						\
  ({									\
	BUILD_BUG_ON(sizeof(*(ptr)) != 8);				\
	cmpxchg((ptr), (o), (n));					\
  })

#undef __ASM__MB
#undef ____cmpxchg

#define __HAVE_ARCH_CMPXCHG 1

#define atomic64_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), old, new))
#define atomic64_xchg(v, new) (xchg(&((v)->counter), new))

#define atomic_cmpxchg(v, old, new) (cmpxchg(&((v)->counter), old, new))
#define atomic_xchg(v, new) (xchg(&((v)->counter), new))

/**
 * __atomic_add_unless - add unless the number is a given value
 * @v: pointer of type atomic_t
 * @a: the amount to add to v...
 * @u: ...unless v is equal to u.
 *
 * Atomically adds @a to @v, so long as it was not @u.
 * Returns the old value of @v.
 */
static __inline__ int __atomic_add_unless(atomic_t *v, int a, int u)
{
	int c, old;
	c = atomic_read(v);
	for (;;) {
		if (unlikely(c == (u)))
			break;
		old = atomic_cmpxchg((v), c, c + (a));
		if (likely(old == c))
			break;
		c = old;
	}
	return c;
}


/**
 * atomic64_add_unless - add unless the number is a given value
 * @v: pointer of type atomic64_t
 * @a: the amount to add to v...
 * @u: ...unless v is equal to u.
 *
 * Atomically adds @a to @v, so long as it was not @u.
 * Returns the old value of @v.
 */
static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
{
	long c, old;
	c = atomic64_read(v);
	for (;;) {
		if (unlikely(c == (u)))
			break;
		old = atomic64_cmpxchg((v), c, c + (a));
		if (likely(old == c))
			break;
		c = old;
	}
	return c != (u);
}

#define atomic64_inc_not_zero(v) atomic64_add_unless((v), 1, 0)

#define atomic_add_negative(a, v) (atomic_add_return((a), (v)) < 0)
#define atomic64_add_negative(a, v) (atomic64_add_return((a), (v)) < 0)

#define atomic_dec_return(v) atomic_sub_return(1,(v))
#define atomic64_dec_return(v) atomic64_sub_return(1,(v))

#define atomic_inc_return(v) atomic_add_return(1,(v))
#define atomic64_inc_return(v) atomic64_add_return(1,(v))

#define atomic_sub_and_test(i,v) (atomic_sub_return((i), (v)) == 0)
#define atomic64_sub_and_test(i,v) (atomic64_sub_return((i), (v)) == 0)

#define atomic_inc_and_test(v) (atomic_add_return(1, (v)) == 0)
#define atomic64_inc_and_test(v) (atomic64_add_return(1, (v)) == 0)

#define atomic_dec_and_test(v) (atomic_sub_return(1, (v)) == 0)
#define atomic64_dec_and_test(v) (atomic64_sub_return(1, (v)) == 0)

#define atomic_inc(v) atomic_add(1,(v))
#define atomic64_inc(v) atomic64_add(1,(v))

#define atomic_dec(v) atomic_sub(1,(v))
#define atomic64_dec(v) atomic64_sub(1,(v))

#define smp_mb__before_atomic_dec()	smp_mb()
#define smp_mb__after_atomic_dec()	smp_mb()
#define smp_mb__before_atomic_inc()	smp_mb()
#define smp_mb__after_atomic_inc()	smp_mb()

#endif /* _ALPHA_ATOMIC_H */