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