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27b012e2 MD |
1 | #ifndef _URCU_H |
2 | #define _URCU_H | |
3 | ||
b257a10b MD |
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 | ||
27b012e2 MD |
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 */ | |
25 | static inline void atomic_inc(int *v) | |
26 | { | |
27 | asm volatile("lock; incl %0" | |
f69f195a | 28 | : "+m" (*v)); |
27b012e2 MD |
29 | } |
30 | ||
31 | /* Nop everywhere except on alpha. */ | |
32 | #define smp_read_barrier_depends() | |
33 | ||
41718ff9 MD |
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 | ||
27b012e2 MD |
64 | #define SIGURCU SIGUSR1 |
65 | ||
66 | /* Global quiescent period parity */ | |
67 | extern int urcu_qparity; | |
68 | ||
69 | extern int __thread urcu_active_readers[2]; | |
70 | ||
71 | static inline int get_urcu_qparity(void) | |
72 | { | |
73 | return urcu_qparity; | |
74 | } | |
75 | ||
76 | /* | |
77 | * returns urcu_parity. | |
78 | */ | |
79 | static 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 | ||
91 | static 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 | ||
41718ff9 MD |
101 | extern void rcu_write_lock(void); |
102 | extern void rcu_write_unlock(void); | |
103 | ||
27b012e2 MD |
104 | extern void *urcu_publish_content(void **ptr, void *new); |
105 | ||
106 | /* | |
107 | * Reader thread registration. | |
108 | */ | |
109 | extern void urcu_register_thread(void); | |
110 | extern void urcu_register_thread(void); | |
111 | ||
112 | #endif /* _URCU_H */ |