path: root/include/linux/atomic.h

/* SPDX-License-Identifier: GPL-2.0 */
/* Atomic operations usable in machine independent code */
#ifndef _LINUX_ATOMIC_H
#define _LINUX_ATOMIC_H
#include <linux/types.h>

#include <asm/atomic.h>
#include <asm/barrier.h>

/*
 * Relaxed variants of xchg, cmpxchg and some atomic operations.
 *
 * We support four variants:
 *
 * - Fully ordered: The default implementation, no suffix required.
 * - Acquire: Provides ACQUIRE semantics, _acquire suffix.
 * - Release: Provides RELEASE semantics, _release suffix.
 * - Relaxed: No ordering guarantees, _relaxed suffix.
 *
 * For compound atomics performing both a load and a store, ACQUIRE
 * semantics apply only to the load and RELEASE semantics only to the
 * store portion of the operation. Note that a failed cmpxchg_acquire
 * does -not- imply any memory ordering constraints.
 *
 * See Documentation/memory-barriers.txt for ACQUIRE/RELEASE definitions.
 */

#ifndef atomic_read_acquire
#define  atomic_read_acquire(v)		smp_load_acquire(&(v)->counter)
#endif

#ifndef atomic_set_release
#define  atomic_set_release(v, i)	smp_store_release(&(v)->counter, (i))
#endif

/*
 * The idea here is to build acquire/release variants by adding explicit
 * barriers on top of the relaxed variant. In the case where the relaxed
 * variant is already fully ordered, no additional barriers are needed.
 *
 * If an architecture overrides __atomic_acquire_fence() it will probably
 * want to define smp_mb__after_spinlock().
 */
#ifndef __atomic_acquire_fence
#define __atomic_acquire_fence		smp_mb__after_atomic
#endif

#ifndef __atomic_release_fence
#define __atomic_release_fence		smp_mb__before_atomic
#endif

#ifndef __atomic_pre_full_fence
#define __atomic_pre_full_fence		smp_mb__before_atomic
#endif

#ifndef __atomic_post_full_fence
#define __atomic_post_full_fence	smp_mb__after_atomic
#endif

#define __atomic_op_acquire(op, args...)				\
({									\
	typeof(op##_relaxed(args)) __ret  = op##_relaxed(args);		\
	__atomic_acquire_fence();					\
	__ret;								\
})

#define __atomic_op_release(op, args...)				\
({									\
	__atomic_release_fence();					\
	op##_relaxed(args);						\
})

#define __atomic_op_fence(op, args...)					\
({									\
	typeof(op##_relaxed(args)) __ret;				\
	__atomic_pre_full_fence();					\
	__ret = op##_relaxed(args);					\
	__atomic_post_full_fence();					\
	__ret;								\
})

/* atomic_add_return_relaxed */
#ifndef atomic_add_return_relaxed
#define  atomic_add_return_relaxed	atomic_add_return
#define  atomic_add_return_acquire	atomic_add_return
#define  atomic_add_return_release	atomic_add_return

#else /* atomic_add_return_relaxed */

#ifndef atomic_add_return_acquire
#define  atomic_add_return_acquire(...)					\
	__atomic_op_acquire(atomic_add_return, __VA_ARGS__)
#endif

#ifndef atomic_add_return_release
#define  atomic_add_return_release(...)					\
	__atomic_op_release(atomic_add_return, __VA_ARGS__)
#endif

#ifndef atomic_add_return
#define  atomic_add_return(...)						\
	__atomic_op_fence(atomic_add_return, __VA_ARGS__)
#endif
#endif /* atomic_add_return_relaxed */

#ifndef atomic_inc
#define atomic_inc(v)			atomic_add(1, (v))
#endif

/* atomic_inc_return_relaxed */
#ifndef atomic_inc_return_relaxed

#ifndef atomic_inc_return
#define atomic_inc_return(v)		atomic_add_return(1, (v))
#define atomic_inc_return_relaxed(v)	atomic_add_return_relaxed(1, (v))
#define atomic_inc_return_acquire(v)	atomic_add_return_acquire(1, (v))
#define atomic_inc_return_release(v)	atomic_add_return_release(1, (v))
#else /* atomic_inc_return */
#define  atomic_inc_return_relaxed	atomic_inc_return
#define  atomic_inc_return_acquire	atomic_inc_return
#define  atomic_inc_return_release	atomic_inc_return
#endif /* atomic_inc_return */

#else /* atomic_inc_return_relaxed */

#ifndef atomic_inc_return_acquire
#define  atomic_inc_return_acquire(...)					\
	__atomic_op_acquire(atomic_inc_return, __VA_ARGS__)
#endif

#ifndef atomic_inc_return_release
#define  atomic_inc_return_release(...)					\
	__atomic_op_release(atomic_inc_return, __VA_ARGS__)
#endif

#ifndef atomic_inc_return
#define  atomic_inc_return(...)						\
	__atomic_op_fence(atomic_inc_return, __VA_ARGS__)
#endif
#endif /* atomic_inc_return_relaxed */

/* atomic_sub_return_relaxed */
#ifndef atomic_sub_return_relaxed
#define  atomic_sub_return_relaxed	atomic_sub_return
#define  atomic_sub_return_acquire	atomic_sub_return
#define  atomic_sub_return_release	atomic_sub_return

#else /* atomic_sub_return_relaxed */

#ifndef atomic_sub_return_acquire
#define  atomic_sub_return_acquire(...)					\
	__atomic_op_acquire(atomic_sub_return, __VA_ARGS__)
#endif

#ifndef atomic_sub_return_release
#define  atomic_sub_return_release(...)					\
	__atomic_op_release(atomic_sub_return, __VA_ARGS__)
#endif

#ifndef atomic_sub_return
#define  atomic_sub_return(...)						\
	__atomic_op_fence(atomic_sub_return, __VA_ARGS__)
#endif
#endif /* atomic_sub_return_relaxed */

#ifndef atomic_dec
#define atomic_dec(v)			atomic_sub(1, (v))
#endif

/* atomic_dec_return_relaxed */
#ifndef atomic_dec_return_relaxed

#ifndef atomic_dec_return
#define atomic_dec_return(v)		atomic_sub_return(1, (v))
#define atomic_dec_return_relaxed(v)	atomic_sub_return_relaxed(1, (v))
#define atomic_dec_return_acquire(v)	atomic_sub_return_acquire(1, (v))
#define atomic_dec_return_release(v)	atomic_sub_return_release(1, (v))
#else /* atomic_dec_return */
#define  atomic_dec_return_relaxed	atomic_dec_return
#define  atomic_dec_return_acquire	atomic_dec_return
#define  atomic_dec_return_release	atomic_dec_return
#endif /* atomic_dec_return */

#else /* atomic_dec_return_relaxed */

#ifndef atomic_dec_return_acquire
#define  atomic_dec_return_acquire(...)					\
	__atomic_op_acquire(atomic_dec_return, __VA_ARGS__)
#endif

#ifndef atomic_dec_return_release
#define  atomic_dec_return_release(...)					\
	__atomic_op_release(atomic_dec_return, __VA_ARGS__)
#endif

#ifndef atomic_dec_return
#define  atomic_dec_return(...)						\
	__atomic_op_fence(atomic_dec_return, __VA_ARGS__)
#endif
#endif /* atomic_dec_return_relaxed */


/* atomic_fetch_add_relaxed */
#ifndef atomic_fetch_add_relaxed
#define atomic_fetch_add_relaxed	atomic_fetch_add
#define atomic_fetch_add_acquire	atomic_fetch_add
#define atomic_fetch_add_release	atomic_fetch_add

#else /* atomic_fetch_add_relaxed */

#ifndef atomic_fetch_add_acquire
#define atomic_fet