/* * 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. */#include <linux/types.h>#include <linux/cache.h>#include <linux/spinlock.h>#include <linux/init.h>#include <linux/export.h>#include <linux/atomic.h> /* * We use a hashed array of spinlocks to provide exclusive access * to each atomic64_t variable.  Since this is expected to used on * systems with small numbers of CPUs (<= 4 or so), we use a * relatively small array of 16 spinlocks to avoid wasting too much * memory on the spinlock array. */#define NR_LOCKS	16 /* * Ensure each lock is in a separate cacheline. */static union {	raw_spinlock_t lock;	char pad[L1_CACHE_BYTES];} atomic64_lock[NR_LOCKS] __cacheline_aligned_in_smp; static inline raw_spinlock_t *lock_addr(const atomic64_t *v){	unsigned long addr = (unsigned long) v; 	addr >>= L1_CACHE_SHIFT;	addr ^= (addr >> 8) ^ (addr >> 16);	return &atomic64_lock[addr & (NR_LOCKS - 1)].lock;} long long atomic64_read(const atomic64_t *v){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v);	long long val; 	raw_spin_lock_irqsave(lock, flags);	val = v->counter;	raw_spin_unlock_irqrestore(lock, flags);	return val;}EXPORT_SYMBOL(atomic64_read); void atomic64_set(atomic64_t *v, long long i){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v); 	raw_spin_lock_irqsave(lock, flags);	v->counter = i;	raw_spin_unlock_irqrestore(lock, flags);}EXPORT_SYMBOL(atomic64_set); void atomic64_add(long long a, atomic64_t *v){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v); 	raw_spin_lock_irqsave(lock, flags);	v->counter += a;	raw_spin_unlock_irqrestore(lock, flags);}EXPORT_SYMBOL(atomic64_add); long long atomic64_add_return(long long a, atomic64_t *v){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v);	long long val; 	raw_spin_lock_irqsave(lock, flags);	val = v->counter += a;	raw_spin_unlock_irqrestore(lock, flags);	return val;}EXPORT_SYMBOL(atomic64_add_return); void atomic64_sub(long long a, atomic64_t *v){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v); 	raw_spin_lock_irqsave(lock, flags);	v->counter -= a;	raw_spin_unlock_irqrestore(lock, flags);}EXPORT_SYMBOL(atomic64_sub); long long atomic64_sub_return(long long a, atomic64_t *v){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v);	long long val; 	raw_spin_lock_irqsave(lock, flags);	val = v->counter -= a;	raw_spin_unlock_irqrestore(lock, flags);	return val;}EXPORT_SYMBOL(atomic64_sub_return); long long atomic64_dec_if_positive(atomic64_t *v){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v);	long long val; 	raw_spin_lock_irqsave(lock, flags);	val = v->counter - 1;	if (val >= 0)		v->counter = val;	raw_spin_unlock_irqrestore(lock, flags);	return val;}EXPORT_SYMBOL(atomic64_dec_if_positive); long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v);	long long val; 	raw_spin_lock_irqsave(lock, flags);	val = v->counter;	if (val == o)		v->counter = n;	raw_spin_unlock_irqrestore(lock, flags);	return val;}EXPORT_SYMBOL(atomic64_cmpxchg); long long atomic64_xchg(atomic64_t *v, long long new){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v);	long long val; 	raw_spin_lock_irqsave(lock, flags);	val = v->counter;	v->counter = new;	raw_spin_unlock_irqrestore(lock, flags);	return val;}EXPORT_SYMBOL(atomic64_xchg); int atomic64_add_unless(atomic64_t *v, long long a, long long u){	unsigned long flags;	raw_spinlock_t *lock = lock_addr(v);	int ret = 0; 	raw_spin_lock_irqsave(lock, flags);	if (v->counter != u) {		v->counter += a;		ret = 1;	}	raw_spin_unlock_irqrestore(lock, flags);	return ret;}EXPORT_SYMBOL(atomic64_add_unless); static int init_atomic64_lock(void){	int i; 	for (i = 0; i < NR_LOCKS; ++i)		raw_spin_lock_init(&atomic64_lock[i].lock);	return 0;} pure_initcall(init_atomic64_lock);