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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>
7 #include <asm/atomic.h>
8 #include <asm/barrier.h>
11 * Relaxed variants of xchg, cmpxchg and some atomic operations.
13 * We support four variants:
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.
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.
25 * See Documentation/memory-barriers.txt for ACQUIRE/RELEASE definitions.
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))
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))
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.
39 * If an architecture overrides __atomic_acquire_fence() it will probably
40 * want to define smp_mb__after_spinlock().
42 #ifndef __atomic_acquire_fence
43 #define __atomic_acquire_fence smp_mb__after_atomic
46 #ifndef __atomic_release_fence
47 #define __atomic_release_fence smp_mb__before_atomic
50 #ifndef __atomic_pre_full_fence
51 #define __atomic_pre_full_fence smp_mb__before_atomic
54 #ifndef __atomic_post_full_fence
55 #define __atomic_post_full_fence smp_mb__after_atomic
58 #define __atomic_op_acquire(op, args...) \
60 typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
61 __atomic_acquire_fence(); \
65 #define __atomic_op_release(op, args...) \
67 __atomic_release_fence(); \
71 #define __atomic_op_fence(op, args...) \
73 typeof(op##_relaxed(args)) __ret; \
74 __atomic_pre_full_fence(); \
75 __ret = op##_relaxed(args); \
76 __atomic_post_full_fence(); \
81 #include <linux/atomic-arch-fallback.h>
82 #include <asm-generic/atomic-instrumented.h>
84 #include <linux/atomic-fallback.h>
87 #include <asm-generic/atomic-long.h>
89 #endif /* _LINUX_ATOMIC_H */