-
Notifications
You must be signed in to change notification settings - Fork 54.5k
/
atomic.h
84 lines (71 loc) · 2.58 KB
/
atomic.h
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
/* 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.
*/
#define atomic_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c))
#define atomic_cond_read_relaxed(v, c) smp_cond_load_relaxed(&(v)->counter, (c))
#define atomic64_cond_read_acquire(v, c) smp_cond_load_acquire(&(v)->counter, (c))
#define atomic64_cond_read_relaxed(v, c) smp_cond_load_relaxed(&(v)->counter, (c))
/*
* 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; \
})
#include <linux/atomic/atomic-arch-fallback.h>
#include <linux/atomic/atomic-long.h>
#include <linux/atomic/atomic-instrumented.h>
#endif /* _LINUX_ATOMIC_H */