linux/include/asm-generic/local64.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_GENERIC_LOCAL64_H
#define _ASM_GENERIC_LOCAL64_H

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

/*
 * A signed long type for operations which are atomic for a single CPU.
 * Usually used in combination with per-cpu variables.
 *
 * This is the default implementation, which uses atomic64_t.  Which is
 * rather pointless.  The whole point behind local64_t is that some processors
 * can perform atomic adds and subtracts in a manner which is atomic wrt IRQs
 * running on this CPU.  local64_t allows exploitation of such capabilities.
 */

/* Implement in terms of atomics. */

#if BITS_PER_LONG == 64

#include <asm/local.h>

local64_t;

#define LOCAL64_INIT(i) …

#define local64_read(l) …
#define local64_set(l,i) …
#define local64_inc(l) …
#define local64_dec(l) …
#define local64_add(i,l) …
#define local64_sub(i,l) …

#define local64_sub_and_test(i, l) …
#define local64_dec_and_test(l) …
#define local64_inc_and_test(l) …
#define local64_add_negative(i, l) …
#define local64_add_return(i, l) …
#define local64_sub_return(i, l) …
#define local64_inc_return(l) …

static inline s64 local64_cmpxchg(local64_t *l, s64 old, s64 new)
{ … }

static inline bool local64_try_cmpxchg(local64_t *l, s64 *old, s64 new)
{ … }

#define local64_xchg(l, n) …
#define local64_add_unless(l, _a, u) …
#define local64_inc_not_zero(l) …

/* Non-atomic variants, ie. preemption disabled and won't be touched
 * in interrupt, etc.  Some archs can optimize this case well. */
#define __local64_inc(l) …
#define __local64_dec(l) …
#define __local64_add(i,l) …
#define __local64_sub(i,l) …

#else /* BITS_PER_LONG != 64 */

#include <linux/atomic.h>

/* Don't use typedef: don't want them to be mixed with atomic_t's. */
typedef struct {
	atomic64_t a;
} local64_t;

#define LOCAL64_INIT …

#define local64_read …
#define local64_set …
#define local64_inc …
#define local64_dec …
#define local64_add …
#define local64_sub …

#define local64_sub_and_test …
#define local64_dec_and_test …
#define local64_inc_and_test …
#define local64_add_negative …
#define local64_add_return …
#define local64_sub_return …
#define local64_inc_return …

#define local64_cmpxchg …
#define local64_try_cmpxchg …
#define local64_xchg …
#define local64_add_unless …
#define local64_inc_not_zero …

/* Non-atomic variants, ie. preemption disabled and won't be touched
 * in interrupt, etc.  Some archs can optimize this case well. */
#define __local64_inc …
#define __local64_dec …
#define __local64_add …
#define __local64_sub …

#endif /* BITS_PER_LONG != 64 */

#endif /* _ASM_GENERIC_LOCAL64_H */