1/*
2 * Generic barrier definitions, originally based on MN10300 definitions.
3 *
4 * It should be possible to use these on really simple architectures,
5 * but it serves more as a starting point for new ports.
6 *
7 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
8 * Written by David Howells (dhowells@redhat.com)
9 *
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public Licence
12 * as published by the Free Software Foundation; either version
13 * 2 of the Licence, or (at your option) any later version.
14 */
15#ifndef __ASM_GENERIC_BARRIER_H
16#define __ASM_GENERIC_BARRIER_H
17
18#ifndef __ASSEMBLY__
19
20#include <linux/compiler.h>
21
22#ifndef nop
23#define nop()	asm volatile ("nop")
24#endif
25
26/*
27 * Force strict CPU ordering. And yes, this is required on UP too when we're
28 * talking to devices.
29 *
30 * Fall back to compiler barriers if nothing better is provided.
31 */
32
33#ifndef mb
34#define mb()	barrier()
35#endif
36
37#ifndef rmb
38#define rmb()	mb()
39#endif
40
41#ifndef wmb
42#define wmb()	mb()
43#endif
44
45#ifndef dma_rmb
46#define dma_rmb()	rmb()
47#endif
48
49#ifndef dma_wmb
50#define dma_wmb()	wmb()
51#endif
52
53#ifndef read_barrier_depends
54#define read_barrier_depends()		do { } while (0)
55#endif
56
57#ifdef CONFIG_SMP
58#define smp_mb()	mb()
59#define smp_rmb()	rmb()
60#define smp_wmb()	wmb()
61#define smp_read_barrier_depends()	read_barrier_depends()
62#else
63#define smp_mb()	barrier()
64#define smp_rmb()	barrier()
65#define smp_wmb()	barrier()
66#define smp_read_barrier_depends()	do { } while (0)
67#endif
68
69#ifndef set_mb
70#define set_mb(var, value)  do { (var) = (value); mb(); } while (0)
71#endif
72
73#ifndef smp_mb__before_atomic
74#define smp_mb__before_atomic()	smp_mb()
75#endif
76
77#ifndef smp_mb__after_atomic
78#define smp_mb__after_atomic()	smp_mb()
79#endif
80
81#define smp_store_release(p, v)						\
82do {									\
83	compiletime_assert_atomic_type(*p);				\
84	smp_mb();							\
85	ACCESS_ONCE(*p) = (v);						\
86} while (0)
87
88#define smp_load_acquire(p)						\
89({									\
90	typeof(*p) ___p1 = ACCESS_ONCE(*p);				\
91	compiletime_assert_atomic_type(*p);				\
92	smp_mb();							\
93	___p1;								\
94})
95
96#endif /* !__ASSEMBLY__ */
97#endif /* __ASM_GENERIC_BARRIER_H */
98