fix wait_for_quiescent_state
[urcu.git] / urcu.h
CommitLineData
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1#ifndef _URCU_H
2#define _URCU_H
3
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4/*
5 * urcu.h
6 *
7 * Userspace RCU header
8 *
9 * Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
10 *
11 * Distributed under GPLv2
12 */
13
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14/* The "volatile" is due to gcc bugs */
15#define barrier() __asm__ __volatile__("": : :"memory")
16
17/* x86 32/64 specific */
18#define mb() asm volatile("mfence":::"memory")
19#define rmb() asm volatile("lfence":::"memory")
20#define wmb() asm volatile("sfence" ::: "memory")
21
22
23
24/* x86 32 */
25static inline void atomic_inc(int *v)
26{
27 asm volatile("lock; incl %0"
f69f195a 28 : "+m" (*v));
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29}
30
31/* Nop everywhere except on alpha. */
32#define smp_read_barrier_depends()
33
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34/*
35 * Prevent the compiler from merging or refetching accesses. The compiler
36 * is also forbidden from reordering successive instances of ACCESS_ONCE(),
37 * but only when the compiler is aware of some particular ordering. One way
38 * to make the compiler aware of ordering is to put the two invocations of
39 * ACCESS_ONCE() in different C statements.
40 *
41 * This macro does absolutely -nothing- to prevent the CPU from reordering,
42 * merging, or refetching absolutely anything at any time. Its main intended
43 * use is to mediate communication between process-level code and irq/NMI
44 * handlers, all running on the same CPU.
45 */
46#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
47
48/**
49 * rcu_dereference - fetch an RCU-protected pointer in an
50 * RCU read-side critical section. This pointer may later
51 * be safely dereferenced.
52 *
53 * Inserts memory barriers on architectures that require them
54 * (currently only the Alpha), and, more importantly, documents
55 * exactly which pointers are protected by RCU.
56 */
57
58#define rcu_dereference(p) ({ \
59 typeof(p) _________p1 = ACCESS_ONCE(p); \
60 smp_read_barrier_depends(); \
61 (_________p1); \
62 })
63
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64#define SIGURCU SIGUSR1
65
66/* Global quiescent period parity */
67extern int urcu_qparity;
68
69extern int __thread urcu_active_readers[2];
70
71static inline int get_urcu_qparity(void)
72{
73 return urcu_qparity;
74}
75
76/*
77 * returns urcu_parity.
78 */
79static inline int rcu_read_lock(void)
80{
81 int urcu_parity = get_urcu_qparity();
82 urcu_active_readers[urcu_parity]++;
83 /*
84 * Increment active readers count before accessing the pointer.
85 * See force_mb_all_threads().
86 */
87 barrier();
88 return urcu_parity;
89}
90
91static inline void rcu_read_unlock(int urcu_parity)
92{
93 barrier();
94 /*
95 * Finish using rcu before decrementing the pointer.
96 * See force_mb_all_threads().
97 */
98 urcu_active_readers[urcu_parity]--;
99}
100
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101extern void rcu_write_lock(void);
102extern void rcu_write_unlock(void);
103
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104extern void *urcu_publish_content(void **ptr, void *new);
105
106/*
107 * Reader thread registration.
108 */
109extern void urcu_register_thread(void);
110extern void urcu_register_thread(void);
111
112#endif /* _URCU_H */
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