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1 | #ifndef _URCU_QSBR_STATIC_H |
2 | #define _URCU_QSBR_STATIC_H | |
3 | ||
4 | /* | |
5 | * urcu-qsbr-static.h | |
6 | * | |
7 | * Userspace RCU QSBR header. | |
8 | * | |
9 | * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-qsbr.h for linking | |
10 | * dynamically with the userspace rcu QSBR library. | |
11 | * | |
12 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> | |
13 | * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. | |
14 | * | |
15 | * This library is free software; you can redistribute it and/or | |
16 | * modify it under the terms of the GNU Lesser General Public | |
17 | * License as published by the Free Software Foundation; either | |
18 | * version 2.1 of the License, or (at your option) any later version. | |
19 | * | |
20 | * This library is distributed in the hope that it will be useful, | |
21 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
23 | * Lesser General Public License for more details. | |
24 | * | |
25 | * You should have received a copy of the GNU Lesser General Public | |
26 | * License along with this library; if not, write to the Free Software | |
27 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
28 | * | |
29 | * IBM's contributions to this file may be relicensed under LGPLv2 or later. | |
30 | */ | |
31 | ||
32 | #include <stdlib.h> | |
33 | #include <pthread.h> | |
34 | #include <assert.h> | |
35 | ||
36 | #include <compiler.h> | |
37 | #include <arch.h> | |
38 | ||
39 | /* | |
40 | * Identify a shared load. A smp_rmc() or smp_mc() should come before the load. | |
41 | */ | |
42 | #define _LOAD_SHARED(p) ACCESS_ONCE(p) | |
43 | ||
44 | /* | |
45 | * Load a data from shared memory, doing a cache flush if required. | |
46 | */ | |
47 | #define LOAD_SHARED(p) \ | |
48 | ({ \ | |
49 | smp_rmc(); \ | |
50 | _LOAD_SHARED(p); \ | |
51 | }) | |
52 | ||
53 | /* | |
54 | * Identify a shared store. A smp_wmc() or smp_mc() should follow the store. | |
55 | */ | |
56 | #define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); }) | |
57 | ||
58 | /* | |
59 | * Store v into x, where x is located in shared memory. Performs the required | |
60 | * cache flush after writing. Returns v. | |
61 | */ | |
62 | #define STORE_SHARED(x, v) \ | |
63 | ({ \ | |
64 | _STORE_SHARED(x, v); \ | |
65 | smp_wmc(); \ | |
66 | (v); \ | |
67 | }) | |
68 | ||
69 | /** | |
70 | * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable | |
71 | * into a RCU read-side critical section. The pointer can later be safely | |
72 | * dereferenced within the critical section. | |
73 | * | |
74 | * This ensures that the pointer copy is invariant thorough the whole critical | |
75 | * section. | |
76 | * | |
77 | * Inserts memory barriers on architectures that require them (currently only | |
78 | * Alpha) and documents which pointers are protected by RCU. | |
79 | * | |
80 | * Should match rcu_assign_pointer() or rcu_xchg_pointer(). | |
81 | */ | |
82 | ||
83 | #define _rcu_dereference(p) ({ \ | |
84 | typeof(p) _________p1 = LOAD_SHARED(p); \ | |
85 | smp_read_barrier_depends(); \ | |
86 | (_________p1); \ | |
87 | }) | |
88 | ||
89 | /* | |
90 | * This code section can only be included in LGPL 2.1 compatible source code. | |
91 | * See below for the function call wrappers which can be used in code meant to | |
92 | * be only linked with the Userspace RCU library. This comes with a small | |
93 | * performance degradation on the read-side due to the added function calls. | |
94 | * This is required to permit relinking with newer versions of the library. | |
95 | */ | |
96 | ||
97 | /* | |
98 | * If a reader is really non-cooperative and refuses to commit its | |
99 | * rcu_reader_qs_gp count to memory (there is no barrier in the reader | |
100 | * per-se), kick it after a few loops waiting for it. | |
101 | */ | |
102 | #define KICK_READER_LOOPS 10000 | |
103 | ||
104 | #ifdef DEBUG_RCU | |
105 | #define rcu_assert(args...) assert(args) | |
106 | #else | |
107 | #define rcu_assert(args...) | |
108 | #endif | |
109 | ||
110 | #ifdef DEBUG_YIELD | |
111 | #include <sched.h> | |
112 | #include <time.h> | |
113 | #include <pthread.h> | |
114 | #include <unistd.h> | |
115 | ||
116 | #define YIELD_READ (1 << 0) | |
117 | #define YIELD_WRITE (1 << 1) | |
118 | ||
119 | /* maximum sleep delay, in us */ | |
120 | #define MAX_SLEEP 50 | |
121 | ||
122 | extern unsigned int yield_active; | |
123 | extern unsigned int __thread rand_yield; | |
124 | ||
125 | static inline void debug_yield_read(void) | |
126 | { | |
127 | if (yield_active & YIELD_READ) | |
128 | if (rand_r(&rand_yield) & 0x1) | |
129 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
130 | } | |
131 | ||
132 | static inline void debug_yield_write(void) | |
133 | { | |
134 | if (yield_active & YIELD_WRITE) | |
135 | if (rand_r(&rand_yield) & 0x1) | |
136 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
137 | } | |
138 | ||
139 | static inline void debug_yield_init(void) | |
140 | { | |
141 | rand_yield = time(NULL) ^ pthread_self(); | |
142 | } | |
143 | #else | |
144 | static inline void debug_yield_read(void) | |
145 | { | |
146 | } | |
147 | ||
148 | static inline void debug_yield_write(void) | |
149 | { | |
150 | } | |
151 | ||
152 | static inline void debug_yield_init(void) | |
153 | { | |
154 | ||
155 | } | |
156 | #endif | |
157 | ||
158 | static inline void reader_barrier() | |
159 | { | |
160 | smp_mb(); | |
161 | } | |
162 | ||
163 | /* | |
164 | * Global quiescent period counter with low-order bits unused. | |
165 | * Using a int rather than a char to eliminate false register dependencies | |
166 | * causing stalls on some architectures. | |
167 | */ | |
168 | extern long urcu_gp_ctr; | |
169 | ||
170 | extern long __thread rcu_reader_qs_gp; | |
171 | ||
172 | static inline int rcu_gp_ongoing(long *value) | |
173 | { | |
174 | if (value == NULL) | |
175 | return 0; | |
176 | ||
177 | return LOAD_SHARED(*value) & 1; | |
178 | } | |
179 | ||
180 | static inline void _rcu_read_lock(void) | |
181 | { | |
182 | rcu_assert(rcu_reader_qs_gp & 1); | |
183 | } | |
184 | ||
185 | static inline void _rcu_read_unlock(void) | |
186 | { | |
187 | } | |
188 | ||
189 | static inline void _rcu_quiescent_state(void) | |
190 | { | |
191 | smp_mb(); | |
192 | rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1; | |
193 | smp_mb(); | |
194 | } | |
195 | ||
196 | static inline void _rcu_thread_offline(void) | |
197 | { | |
198 | smp_mb(); | |
1a80f356 | 199 | rcu_reader_qs_gp = 0; |
7ac06cef MD |
200 | } |
201 | ||
202 | static inline void _rcu_thread_online(void) | |
203 | { | |
204 | rcu_reader_qs_gp = ACCESS_ONCE(urcu_gp_ctr) + 1; | |
205 | smp_mb(); | |
206 | } | |
207 | ||
208 | /** | |
209 | * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure | |
210 | * meant to be read by RCU read-side critical sections. Returns the assigned | |
211 | * value. | |
212 | * | |
213 | * Documents which pointers will be dereferenced by RCU read-side critical | |
214 | * sections and adds the required memory barriers on architectures requiring | |
215 | * them. It also makes sure the compiler does not reorder code initializing the | |
216 | * data structure before its publication. | |
217 | * | |
218 | * Should match rcu_dereference_pointer(). | |
219 | */ | |
220 | ||
221 | #define _rcu_assign_pointer(p, v) \ | |
222 | ({ \ | |
223 | if (!__builtin_constant_p(v) || \ | |
224 | ((v) != NULL)) \ | |
225 | wmb(); \ | |
226 | STORE_SHARED(p, v); \ | |
227 | }) | |
228 | ||
229 | /** | |
230 | * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous | |
231 | * pointer to the data structure, which can be safely freed after waiting for a | |
232 | * quiescent state using synchronize_rcu(). | |
233 | */ | |
234 | ||
235 | #define _rcu_xchg_pointer(p, v) \ | |
236 | ({ \ | |
237 | if (!__builtin_constant_p(v) || \ | |
238 | ((v) != NULL)) \ | |
239 | wmb(); \ | |
240 | xchg(p, v); \ | |
241 | }) | |
242 | ||
243 | /* | |
244 | * Exchanges the pointer and waits for quiescent state. | |
245 | * The pointer returned can be freed. | |
246 | */ | |
247 | #define _rcu_publish_content(p, v) \ | |
248 | ({ \ | |
249 | void *oldptr; \ | |
250 | oldptr = _rcu_xchg_pointer(p, v); \ | |
251 | synchronize_rcu(); \ | |
252 | oldptr; \ | |
253 | }) | |
254 | ||
255 | #endif /* _URCU_QSBR_STATIC_H */ |