79 строки
2.2 KiB
C
79 строки
2.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* Atomic operations usable in machine independent code */
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#ifndef _LINUX_ATOMIC_H
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#define _LINUX_ATOMIC_H
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#include <linux/types.h>
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#include <asm/atomic.h>
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#include <asm/barrier.h>
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/*
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* Relaxed variants of xchg, cmpxchg and some atomic operations.
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*
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* We support four variants:
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*
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* - Fully ordered: The default implementation, no suffix required.
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* - Acquire: Provides ACQUIRE semantics, _acquire suffix.
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* - Release: Provides RELEASE semantics, _release suffix.
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* - Relaxed: No ordering guarantees, _relaxed suffix.
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*
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* For compound atomics performing both a load and a store, ACQUIRE
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* semantics apply only to the load and RELEASE semantics only to the
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* store portion of the operation. Note that a failed cmpxchg_acquire
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* does -not- imply any memory ordering constraints.
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*
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* See Documentation/memory-barriers.txt for ACQUIRE/RELEASE definitions.
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*/
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/*
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* The idea here is to build acquire/release variants by adding explicit
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* barriers on top of the relaxed variant. In the case where the relaxed
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* variant is already fully ordered, no additional barriers are needed.
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*
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* If an architecture overrides __atomic_acquire_fence() it will probably
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* want to define smp_mb__after_spinlock().
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*/
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#ifndef __atomic_acquire_fence
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#define __atomic_acquire_fence smp_mb__after_atomic
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#endif
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#ifndef __atomic_release_fence
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#define __atomic_release_fence smp_mb__before_atomic
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#endif
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#ifndef __atomic_pre_full_fence
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#define __atomic_pre_full_fence smp_mb__before_atomic
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#endif
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#ifndef __atomic_post_full_fence
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#define __atomic_post_full_fence smp_mb__after_atomic
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#endif
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#define __atomic_op_acquire(op, args...) \
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({ \
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typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
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__atomic_acquire_fence(); \
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__ret; \
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})
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#define __atomic_op_release(op, args...) \
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({ \
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__atomic_release_fence(); \
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op##_relaxed(args); \
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})
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#define __atomic_op_fence(op, args...) \
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({ \
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typeof(op##_relaxed(args)) __ret; \
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__atomic_pre_full_fence(); \
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__ret = op##_relaxed(args); \
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__atomic_post_full_fence(); \
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__ret; \
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})
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#include <linux/atomic-fallback.h>
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#include <asm-generic/atomic-long.h>
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#endif /* _LINUX_ATOMIC_H */
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