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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (C) 2019 Google LLC.
*/
#ifndef __ASM_RWONCE_H
#define __ASM_RWONCE_H
#ifdef CONFIG_SMP
#include <asm/barrier.h>
/*
* Alpha is apparently daft enough to reorder address-dependent loads
* on some CPU implementations. Knock some common sense into it with
* a memory barrier in READ_ONCE().
*
* For the curious, more information about this unusual reordering is
* available in chapter 15 of the "perfbook":
*
* https://kernel.org/pub/linux/kernel/people/paulmck/perfbook/perfbook.html
*
*/
#define __READ_ONCE(x) \
({ \
__unqual_scalar_typeof(x) __x = \
(*(volatile typeof(__x) *)(&(x))); \
mb(); \
(typeof(x))__x; \
})
#endif /* CONFIG_SMP */
#include <asm-generic/rwonce.h>
#endif /* __ASM_RWONCE_H */
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