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7ac06cef MD |
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> | |
f0f7dbdd | 35 | #include <limits.h> |
ae62b5e8 | 36 | #include <sched.h> |
ee72ef6e | 37 | #include <sys/time.h> |
7ac06cef MD |
38 | |
39 | #include <compiler.h> | |
40 | #include <arch.h> | |
41 | ||
42 | /* | |
43 | * Identify a shared load. A smp_rmc() or smp_mc() should come before the load. | |
44 | */ | |
45 | #define _LOAD_SHARED(p) ACCESS_ONCE(p) | |
46 | ||
47 | /* | |
48 | * Load a data from shared memory, doing a cache flush if required. | |
49 | */ | |
50 | #define LOAD_SHARED(p) \ | |
51 | ({ \ | |
52 | smp_rmc(); \ | |
53 | _LOAD_SHARED(p); \ | |
54 | }) | |
55 | ||
56 | /* | |
57 | * Identify a shared store. A smp_wmc() or smp_mc() should follow the store. | |
58 | */ | |
59 | #define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); }) | |
60 | ||
61 | /* | |
62 | * Store v into x, where x is located in shared memory. Performs the required | |
63 | * cache flush after writing. Returns v. | |
64 | */ | |
65 | #define STORE_SHARED(x, v) \ | |
66 | ({ \ | |
67 | _STORE_SHARED(x, v); \ | |
68 | smp_wmc(); \ | |
69 | (v); \ | |
70 | }) | |
71 | ||
72 | /** | |
73 | * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable | |
74 | * into a RCU read-side critical section. The pointer can later be safely | |
75 | * dereferenced within the critical section. | |
76 | * | |
77 | * This ensures that the pointer copy is invariant thorough the whole critical | |
78 | * section. | |
79 | * | |
80 | * Inserts memory barriers on architectures that require them (currently only | |
81 | * Alpha) and documents which pointers are protected by RCU. | |
82 | * | |
83 | * Should match rcu_assign_pointer() or rcu_xchg_pointer(). | |
84 | */ | |
85 | ||
86 | #define _rcu_dereference(p) ({ \ | |
87 | typeof(p) _________p1 = LOAD_SHARED(p); \ | |
88 | smp_read_barrier_depends(); \ | |
89 | (_________p1); \ | |
90 | }) | |
91 | ||
92 | /* | |
93 | * This code section can only be included in LGPL 2.1 compatible source code. | |
94 | * See below for the function call wrappers which can be used in code meant to | |
95 | * be only linked with the Userspace RCU library. This comes with a small | |
96 | * performance degradation on the read-side due to the added function calls. | |
97 | * This is required to permit relinking with newer versions of the library. | |
98 | */ | |
99 | ||
100 | /* | |
101 | * If a reader is really non-cooperative and refuses to commit its | |
8b25e300 | 102 | * rcu_reader qs_gp count to memory (there is no barrier in the reader |
7ac06cef MD |
103 | * per-se), kick it after a few loops waiting for it. |
104 | */ | |
105 | #define KICK_READER_LOOPS 10000 | |
106 | ||
bc6c15bb | 107 | /* |
ae62b5e8 | 108 | * Active attempts to check for reader Q.S. before calling sched_yield(). |
bc6c15bb MD |
109 | */ |
110 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
111 | ||
7ac06cef MD |
112 | #ifdef DEBUG_RCU |
113 | #define rcu_assert(args...) assert(args) | |
114 | #else | |
115 | #define rcu_assert(args...) | |
116 | #endif | |
117 | ||
118 | #ifdef DEBUG_YIELD | |
119 | #include <sched.h> | |
120 | #include <time.h> | |
121 | #include <pthread.h> | |
122 | #include <unistd.h> | |
123 | ||
124 | #define YIELD_READ (1 << 0) | |
125 | #define YIELD_WRITE (1 << 1) | |
126 | ||
127 | /* maximum sleep delay, in us */ | |
128 | #define MAX_SLEEP 50 | |
129 | ||
130 | extern unsigned int yield_active; | |
131 | extern unsigned int __thread rand_yield; | |
132 | ||
133 | static inline void debug_yield_read(void) | |
134 | { | |
135 | if (yield_active & YIELD_READ) | |
136 | if (rand_r(&rand_yield) & 0x1) | |
137 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
138 | } | |
139 | ||
140 | static inline void debug_yield_write(void) | |
141 | { | |
142 | if (yield_active & YIELD_WRITE) | |
143 | if (rand_r(&rand_yield) & 0x1) | |
144 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
145 | } | |
146 | ||
147 | static inline void debug_yield_init(void) | |
148 | { | |
149 | rand_yield = time(NULL) ^ pthread_self(); | |
150 | } | |
151 | #else | |
152 | static inline void debug_yield_read(void) | |
153 | { | |
154 | } | |
155 | ||
156 | static inline void debug_yield_write(void) | |
157 | { | |
158 | } | |
159 | ||
160 | static inline void debug_yield_init(void) | |
161 | { | |
162 | ||
163 | } | |
164 | #endif | |
165 | ||
166 | static inline void reader_barrier() | |
167 | { | |
168 | smp_mb(); | |
169 | } | |
170 | ||
ac258107 | 171 | #define RCU_GP_ONLINE (1UL << 0) |
ae62b5e8 MD |
172 | #define RCU_GP_ONGOING (1UL << 1) |
173 | #define RCU_GP_CTR (1UL << 2) | |
ac258107 | 174 | |
7ac06cef MD |
175 | /* |
176 | * Global quiescent period counter with low-order bits unused. | |
177 | * Using a int rather than a char to eliminate false register dependencies | |
178 | * causing stalls on some architectures. | |
179 | */ | |
f0f7dbdd | 180 | extern unsigned long urcu_gp_ctr; |
7ac06cef | 181 | |
8b25e300 MD |
182 | struct urcu_reader_status { |
183 | unsigned long qs_gp; | |
184 | unsigned long gp_waiting; | |
ee72ef6e MD |
185 | unsigned long qs_time_delta_usec; |
186 | struct timeval qs_time_last; | |
8b25e300 MD |
187 | }; |
188 | ||
189 | extern struct urcu_reader_status __thread urcu_reader_status; | |
7ac06cef | 190 | |
47d2f29e MD |
191 | #if (BITS_PER_LONG < 64) |
192 | static inline int rcu_gp_ongoing(unsigned long *value) | |
193 | { | |
194 | unsigned long reader_gp; | |
195 | ||
196 | if (value == NULL) | |
197 | return 0; | |
198 | reader_gp = LOAD_SHARED(*value); | |
199 | return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR); | |
200 | } | |
201 | #else /* !(BITS_PER_LONG < 64) */ | |
f0f7dbdd | 202 | static inline int rcu_gp_ongoing(unsigned long *value) |
7ac06cef | 203 | { |
f0f7dbdd | 204 | unsigned long reader_gp; |
4e560c17 | 205 | |
7ac06cef MD |
206 | if (value == NULL) |
207 | return 0; | |
4e560c17 | 208 | reader_gp = LOAD_SHARED(*value); |
f0f7dbdd | 209 | return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2); |
7ac06cef | 210 | } |
47d2f29e | 211 | #endif /* !(BITS_PER_LONG < 64) */ |
7ac06cef MD |
212 | |
213 | static inline void _rcu_read_lock(void) | |
214 | { | |
8b25e300 | 215 | rcu_assert(urcu_reader_status.qs_gp); |
7ac06cef MD |
216 | } |
217 | ||
218 | static inline void _rcu_read_unlock(void) | |
219 | { | |
220 | } | |
221 | ||
222 | static inline void _rcu_quiescent_state(void) | |
223 | { | |
ae62b5e8 | 224 | long gp_ctr; |
539718ae | 225 | struct timeval current_time, delta_time; |
ae62b5e8 MD |
226 | |
227 | smp_mb(); | |
ee72ef6e | 228 | gettimeofday(¤t_time, NULL); |
539718ae MD |
229 | timersub(¤t_time, &urcu_reader_status.qs_time_last, &delta_time); |
230 | if (delta_time.tv_sec >= 1) | |
ee72ef6e MD |
231 | _STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 1000000); |
232 | else | |
233 | _STORE_SHARED(urcu_reader_status.qs_time_delta_usec, | |
539718ae | 234 | (unsigned long)delta_time.tv_usec); |
ee72ef6e | 235 | urcu_reader_status.qs_time_last = current_time; |
8b25e300 MD |
236 | /* |
237 | * volatile accesses can be reordered by the compiler when put in the | |
238 | * same expression. | |
239 | */ | |
240 | if (unlikely((gp_ctr = LOAD_SHARED(urcu_gp_ctr)) & RCU_GP_ONGOING) && | |
241 | unlikely(urcu_reader_status.gp_waiting)) { | |
242 | _STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr); | |
ae62b5e8 | 243 | sched_yield(); |
8b25e300 MD |
244 | } else { |
245 | _STORE_SHARED(urcu_reader_status.qs_gp, gp_ctr); | |
ae62b5e8 | 246 | } |
7ac06cef MD |
247 | smp_mb(); |
248 | } | |
249 | ||
250 | static inline void _rcu_thread_offline(void) | |
251 | { | |
252 | smp_mb(); | |
8b25e300 | 253 | STORE_SHARED(urcu_reader_status.qs_gp, 0); |
b3c4dd1a MD |
254 | if (unlikely(LOAD_SHARED(urcu_gp_ctr) & RCU_GP_ONGOING) && |
255 | unlikely(urcu_reader_status.gp_waiting)) { | |
256 | sched_yield(); | |
257 | } | |
7ac06cef MD |
258 | } |
259 | ||
260 | static inline void _rcu_thread_online(void) | |
261 | { | |
539718ae | 262 | struct timeval current_time, delta_time; |
ee72ef6e MD |
263 | |
264 | gettimeofday(¤t_time, NULL); | |
539718ae MD |
265 | timersub(¤t_time, &urcu_reader_status.qs_time_last, &delta_time); |
266 | if (delta_time.tv_sec >= 1) | |
ee72ef6e MD |
267 | _STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 1000000); |
268 | else | |
269 | _STORE_SHARED(urcu_reader_status.qs_time_delta_usec, | |
539718ae | 270 | (unsigned long)delta_time.tv_usec); |
ee72ef6e MD |
271 | urcu_reader_status.qs_time_last = current_time; |
272 | _STORE_SHARED(urcu_reader_status.qs_time_delta_usec, 0); | |
b3c4dd1a | 273 | _STORE_SHARED(urcu_reader_status.qs_gp, LOAD_SHARED(urcu_gp_ctr)); |
7ac06cef MD |
274 | smp_mb(); |
275 | } | |
276 | ||
277 | /** | |
278 | * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure | |
279 | * meant to be read by RCU read-side critical sections. Returns the assigned | |
280 | * value. | |
281 | * | |
282 | * Documents which pointers will be dereferenced by RCU read-side critical | |
283 | * sections and adds the required memory barriers on architectures requiring | |
284 | * them. It also makes sure the compiler does not reorder code initializing the | |
285 | * data structure before its publication. | |
286 | * | |
287 | * Should match rcu_dereference_pointer(). | |
288 | */ | |
289 | ||
290 | #define _rcu_assign_pointer(p, v) \ | |
291 | ({ \ | |
292 | if (!__builtin_constant_p(v) || \ | |
293 | ((v) != NULL)) \ | |
294 | wmb(); \ | |
295 | STORE_SHARED(p, v); \ | |
296 | }) | |
297 | ||
4d1ce26f MD |
298 | /** |
299 | * _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer | |
300 | * is as expected by "old". If succeeds, returns the previous pointer to the | |
301 | * data structure, which can be safely freed after waiting for a quiescent state | |
302 | * using synchronize_rcu(). If fails (unexpected value), returns old (which | |
303 | * should not be freed !). | |
304 | */ | |
305 | ||
306 | #define _rcu_cmpxchg_pointer(p, old, _new) \ | |
307 | ({ \ | |
308 | if (!__builtin_constant_p(_new) || \ | |
309 | ((_new) != NULL)) \ | |
310 | wmb(); \ | |
311 | cmpxchg(p, old, _new); \ | |
312 | }) | |
313 | ||
7ac06cef MD |
314 | /** |
315 | * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous | |
316 | * pointer to the data structure, which can be safely freed after waiting for a | |
317 | * quiescent state using synchronize_rcu(). | |
318 | */ | |
319 | ||
320 | #define _rcu_xchg_pointer(p, v) \ | |
321 | ({ \ | |
322 | if (!__builtin_constant_p(v) || \ | |
323 | ((v) != NULL)) \ | |
324 | wmb(); \ | |
325 | xchg(p, v); \ | |
326 | }) | |
327 | ||
328 | /* | |
329 | * Exchanges the pointer and waits for quiescent state. | |
330 | * The pointer returned can be freed. | |
331 | */ | |
332 | #define _rcu_publish_content(p, v) \ | |
333 | ({ \ | |
334 | void *oldptr; \ | |
335 | oldptr = _rcu_xchg_pointer(p, v); \ | |
336 | synchronize_rcu(); \ | |
337 | oldptr; \ | |
338 | }) | |
339 | ||
340 | #endif /* _URCU_QSBR_STATIC_H */ |