Document rcu_register_thread in README
[userspace-rcu.git] / arch_atomic_x86.h
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1#ifndef _ARCH_ATOMIC_X86_H
2#define _ARCH_ATOMIC_X86_H
3
4/*
5 * Copyright (c) 1991-1994 by Xerox Corporation. All rights reserved.
6 * Copyright (c) 1996-1999 by Silicon Graphics. All rights reserved.
7 * Copyright (c) 1999-2004 Hewlett-Packard Development Company, L.P.
8 * Copyright (c) 2009 Mathieu Desnoyers
9 *
10 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
11 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
12 *
13 * Permission is hereby granted to use or copy this program
14 * for any purpose, provided the above notices are retained on all copies.
15 * Permission to modify the code and to distribute modified code is granted,
16 * provided the above notices are retained, and a notice that the code was
17 * modified is included with the above copyright notice.
18 *
19 * Code inspired from libatomic_ops-1.2, inherited in part from the
20 * Boehm-Demers-Weiser conservative garbage collector.
21 */
22
23#ifndef BITS_PER_LONG
24#define BITS_PER_LONG (__SIZEOF_LONG__ * 8)
25#endif
26
27#ifndef _INCLUDE_API_H
28
29/*
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30 * Derived from AO_compare_and_swap() and AO_test_and_set_full().
31 */
32
33static __attribute__((always_inline))
34unsigned int atomic_exchange_32(volatile unsigned int *addr, unsigned int val)
35{
36 unsigned int result;
37
38 __asm__ __volatile__(
39 /* Note: the "xchg" instruction does not need a "lock" prefix */
40 "xchgl %0, %1"
41 : "=&r"(result), "=m"(*addr)
42 : "0" (val), "m"(*addr)
43 : "memory");
44
45 return result;
46}
47
48#if (BITS_PER_LONG == 64)
49
50static __attribute__((always_inline))
51unsigned long atomic_exchange_64(volatile unsigned long *addr,
52 unsigned long val)
53{
54 unsigned long result;
55
56 __asm__ __volatile__(
57 /* Note: the "xchg" instruction does not need a "lock" prefix */
58 "xchgq %0, %1"
59 : "=&r"(result), "=m"(*addr)
60 : "0" (val), "m"(*addr)
61 : "memory");
62
63 return result;
64}
65
66#endif
67
68static __attribute__((always_inline))
69unsigned long _atomic_exchange(volatile void *addr, unsigned long val, int len)
70{
71 switch (len) {
72 case 4: return atomic_exchange_32(addr, val);
73#if (BITS_PER_LONG == 64)
74 case 8: return atomic_exchange_64(addr, val);
75#endif
76 }
77 /* generate an illegal instruction. Cannot catch this with linker tricks
78 * when optimizations are disabled. */
79 __asm__ __volatile__("ud2");
80 return 0;
81}
82
83#define xchg(addr, v) \
84 ((__typeof__(*(addr))) _atomic_exchange((addr), (unsigned long)(v), \
85 sizeof(*(addr))))
86
87#endif /* #ifndef _INCLUDE_API_H */
88
89#endif /* ARCH_ATOMIC_X86_H */
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