include/asm-generic/local.h

#ifndef _ASM_GENERIC_LOCAL_H
#define _ASM_GENERIC_LOCAL_H

#include <linux/config.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <asm/types.h>

/* An unsigned long type for operations which are atomic for a single
 * CPU.  Usually used in combination with per-cpu variables. */

#if BITS_PER_LONG == 32
/* Implement in terms of atomics. */

/* Don't use typedef: don't want them to be mixed with atomic_t's. */
typedef struct
{
	atomic_t a;
} local_t;

#define LOCAL_INIT(i)	{ ATOMIC_INIT(i) }

#define local_read(l)	((unsigned long)atomic_read(&(l)->a))
#define local_set(l,i)	atomic_set((&(l)->a),(i))
#define local_inc(l)	atomic_inc(&(l)->a)
#define local_dec(l)	atomic_dec(&(l)->a)
#define local_add(i,l)	atomic_add((i),(&(l)->a))
#define local_sub(i,l)	atomic_sub((i),(&(l)->a))

/* Non-atomic variants, ie. preemption disabled and won't be touched
 * in interrupt, etc.  Some archs can optimize this case well. */
#define __local_inc(l)		local_set((l), local_read(l) + 1)
#define __local_dec(l)		local_set((l), local_read(l) - 1)
#define __local_add(i,l)	local_set((l), local_read(l) + (i))
#define __local_sub(i,l)	local_set((l), local_read(l) - (i))

#else /* ... can't use atomics. */
/* Implement in terms of three variables.
   Another option would be to use local_irq_save/restore. */

typedef struct
{
	/* 0 = in hardirq, 1 = in softirq, 2 = usermode. */
	unsigned long v[3];
} local_t;

#define _LOCAL_VAR(l)	((l)->v[!in_interrupt() + !in_irq()])

#define LOCAL_INIT(i)	{ { (i), 0, 0 } }

static inline unsigned long local_read(local_t *l)
{
	return l->v[0] + l->v[1] + l->v[2];
}

static inline void local_set(local_t *l, unsigned long v)
{
	l->v[0] = v;
	l->v[1] = l->v[2] = 0;
}

static inline void local_inc(local_t *l)
{
	preempt_disable();
	_LOCAL_VAR(l)++;
	preempt_enable();
}

static inline void local_dec(local_t *l)
{
	preempt_disable();
	_LOCAL_VAR(l)--;
	preempt_enable();
}

static inline void local_add(unsigned long v, local_t *l)
{
	preempt_disable();
	_LOCAL_VAR(l) += v;
	preempt_enable();
}

static inline void local_sub(unsigned long v, local_t *l)
{
	preempt_disable();
	_LOCAL_VAR(l) -= v;
	preempt_enable();
}

/* Non-atomic variants, ie. preemption disabled and won't be touched
 * in interrupt, etc.  Some archs can optimize this case well. */
#define __local_inc(l)		((l)->v[0]++)
#define __local_dec(l)		((l)->v[0]--)
#define __local_add(i,l)	((l)->v[0] += (i))
#define __local_sub(i,l)	((l)->v[0] -= (i))

#endif /* Non-atomic implementation */

/* Use these for per-cpu local_t variables: on some archs they are
 * much more efficient than these naive implementations.  Note they take
 * a variable (eg. mystruct.foo), not an address.
 */
#define cpu_local_read(v)	local_read(&__get_cpu_var(v))
#define cpu_local_set(v, i)	local_set(&__get_cpu_var(v), (i))
#define cpu_local_inc(v)	local_inc(&__get_cpu_var(v))
#define cpu_local_dec(v)	local_dec(&__get_cpu_var(v))
#define cpu_local_add(i, v)	local_add((i), &__get_cpu_var(v))
#define cpu_local_sub(i, v)	local_sub((i), &__get_cpu_var(v))

/* Non-atomic increments, ie. preemption disabled and won't be touched
 * in interrupt, etc.  Some archs can optimize this case well.
 */
#define __cpu_local_inc(v)	__local_inc(&__get_cpu_var(v))
#define __cpu_local_dec(v)	__local_dec(&__get_cpu_var(v))
#define __cpu_local_add(i, v)	__local_add((i), &__get_cpu_var(v))
#define __cpu_local_sub(i, v)	__local_sub((i), &__get_cpu_var(v))

#endif /* _ASM_GENERIC_LOCAL_H */