1. 根目录:
2. include
3. asm-generic
4. atomic64.h

/*
 * Generic implementation of 64-bit atomics using spinlocks,
 * useful on processors that don't have 64-bit atomic instructions.
 *
 * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */
#ifndef _ASM_GENERIC_ATOMIC64_H
#define _ASM_GENERIC_ATOMIC64_H

typedef struct {
	long long counter;
} atomic64_t;

#define ATOMIC64_INIT(i)	{ (i) }

extern long long atomic64_read(const atomic64_t *v);
extern void	 atomic64_set(atomic64_t *v, long long i);
extern void	 atomic64_add(long long a, atomic64_t *v);
extern long long atomic64_add_return(long long a, atomic64_t *v);
extern void	 atomic64_sub(long long a, atomic64_t *v);
extern long long atomic64_sub_return(long long a, atomic64_t *v);
extern long long atomic64_dec_if_positive(atomic64_t *v);
extern long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n);
extern long long atomic64_xchg(atomic64_t *v, long long new);
extern int	 atomic64_add_unless(atomic64_t *v, long long a, long long u);

#define atomic64_add_negative(a, v)	(atomic64_add_return((a), (v)) < 0)
#define atomic64_inc(v)			atomic64_add(1LL, (v))
#define atomic64_inc_return(v)		atomic64_add_return(1LL, (v))
#define atomic64_inc_and_test(v) 	(atomic64_inc_return(v) == 0)
#define atomic64_sub_and_test(a, v)	(atomic64_sub_return((a), (v)) == 0)
#define atomic64_dec(v)			atomic64_sub(1LL, (v))
#define atomic64_dec_return(v)		atomic64_sub_return(1LL, (v))
#define atomic64_dec_and_test(v)	(atomic64_dec_return((v)) == 0)
#define atomic64_inc_not_zero(v) 	atomic64_add_unless((v), 1LL, 0LL)

#endif  /*  _ASM_GENERIC_ATOMIC64_H  */