/* 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 */