processor.h

 1/* SPDX-License-Identifier: GPL-2.0-only */
 2/*
 3 * Copyright (C) 2020 ARM Ltd.
 4 */
 5#ifndef __ASM_VDSO_PROCESSOR_H
 6#define __ASM_VDSO_PROCESSOR_H
 7
 8#ifndef __ASSEMBLER__
 9
10#ifdef CONFIG_CPU_LOONGSON64
11/*
12 * Loongson-3's SFB (Store-Fill-Buffer) may buffer writes indefinitely when a
13 * tight read loop is executed, because reads take priority over writes & the
14 * hardware (incorrectly) doesn't ensure that writes will eventually occur.
15 *
16 * Since spin loops of any kind should have a cpu_relax() in them, force an SFB
17 * flush from cpu_relax() such that any pending writes will become visible as
18 * expected.
19 */
20#define cpu_relax()	smp_mb()
21#else
22#define cpu_relax()	barrier()
23#endif
24
25#endif /* __ASSEMBLER__ */
26
27#endif /* __ASM_VDSO_PROCESSOR_H */