1/* SPDX-License-Identifier: GPL-2.0 */
2/* Atomic operations usable in machine independent code */
3#ifndef _LINUX_ATOMIC_H
4#define _LINUX_ATOMIC_H
5#include <linux/types.h>
6
7#include <asm/atomic.h>
8#include <asm/barrier.h>
9
10/*
11 * Relaxed variants of xchg, cmpxchg and some atomic operations.
12 *
13 * We support four variants:
14 *
15 * - Fully ordered: The default implementation, no suffix required.
16 * - Acquire: Provides ACQUIRE semantics, _acquire suffix.
17 * - Release: Provides RELEASE semantics, _release suffix.
18 * - Relaxed: No ordering guarantees, _relaxed suffix.
19 *
20 * For compound atomics performing both a load and a store, ACQUIRE
21 * semantics apply only to the load and RELEASE semantics only to the
22 * store portion of the operation. Note that a failed cmpxchg_acquire
23 * does -not- imply any memory ordering constraints.
24 *
25 * See Documentation/memory-barriers.txt for ACQUIRE/RELEASE definitions.
26 */
27
28#define atomic_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c))
29#define atomic_cond_read_relaxed(v, c) smp_cond_load_relaxed(&(v)->counter, (c))
30
31#define atomic64_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c))
32#define atomic64_cond_read_relaxed(v, c) smp_cond_load_relaxed(&(v)->counter, (c))
33
34/*
35 * The idea here is to build acquire/release variants by adding explicit
36 * barriers on top of the relaxed variant. In the case where the relaxed
37 * variant is already fully ordered, no additional barriers are needed.
38 *
39 * If an architecture overrides __atomic_acquire_fence() it will probably
40 * want to define smp_mb__after_spinlock().
41 */
42#ifndef __atomic_acquire_fence
43#define __atomic_acquire_fence smp_mb__after_atomic
44#endif
45
46#ifndef __atomic_release_fence
47#define __atomic_release_fence smp_mb__before_atomic
48#endif
49
50#ifndef __atomic_pre_full_fence
51#define __atomic_pre_full_fence smp_mb__before_atomic
52#endif
53
54#ifndef __atomic_post_full_fence
55#define __atomic_post_full_fence smp_mb__after_atomic
56#endif
57
58#define __atomic_op_acquire(op, args...) \
59({ \
60 typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
61 __atomic_acquire_fence(); \
62 __ret; \
63})
64
65#define __atomic_op_release(op, args...) \
66({ \
67 __atomic_release_fence(); \
68 op##_relaxed(args); \
69})
70
71#define __atomic_op_fence(op, args...) \
72({ \
73 typeof(op##_relaxed(args)) __ret; \
74 __atomic_pre_full_fence(); \
75 __ret = op##_relaxed(args); \
76 __atomic_post_full_fence(); \
77 __ret; \
78})
79
80#include <linux/atomic/atomic-arch-fallback.h>
81#include <linux/atomic/atomic-long.h>
82#include <linux/atomic/atomic-instrumented.h>
83
84#endif /* _LINUX_ATOMIC_H */
85