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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> |
bc6c15bb MD |
36 | #include <syscall.h> |
37 | #include <unistd.h> | |
7ac06cef | 38 | |
ec4e58a3 MD |
39 | #include <urcu/compiler.h> |
40 | #include <urcu/arch.h> | |
1ccf9cbe | 41 | #include <urcu/arch_uatomic.h> |
4f8e3380 | 42 | #include <urcu/list.h> |
7ac06cef MD |
43 | |
44 | /* | |
45 | * Identify a shared load. A smp_rmc() or smp_mc() should come before the load. | |
46 | */ | |
47 | #define _LOAD_SHARED(p) ACCESS_ONCE(p) | |
48 | ||
49 | /* | |
50 | * Load a data from shared memory, doing a cache flush if required. | |
51 | */ | |
52 | #define LOAD_SHARED(p) \ | |
53 | ({ \ | |
54 | smp_rmc(); \ | |
55 | _LOAD_SHARED(p); \ | |
56 | }) | |
57 | ||
58 | /* | |
59 | * Identify a shared store. A smp_wmc() or smp_mc() should follow the store. | |
60 | */ | |
61 | #define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); }) | |
62 | ||
63 | /* | |
64 | * Store v into x, where x is located in shared memory. Performs the required | |
65 | * cache flush after writing. Returns v. | |
66 | */ | |
67 | #define STORE_SHARED(x, v) \ | |
68 | ({ \ | |
69 | _STORE_SHARED(x, v); \ | |
70 | smp_wmc(); \ | |
71 | (v); \ | |
72 | }) | |
73 | ||
74 | /** | |
75 | * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable | |
76 | * into a RCU read-side critical section. The pointer can later be safely | |
77 | * dereferenced within the critical section. | |
78 | * | |
79 | * This ensures that the pointer copy is invariant thorough the whole critical | |
80 | * section. | |
81 | * | |
82 | * Inserts memory barriers on architectures that require them (currently only | |
83 | * Alpha) and documents which pointers are protected by RCU. | |
84 | * | |
85 | * Should match rcu_assign_pointer() or rcu_xchg_pointer(). | |
86 | */ | |
87 | ||
88 | #define _rcu_dereference(p) ({ \ | |
89 | typeof(p) _________p1 = LOAD_SHARED(p); \ | |
90 | smp_read_barrier_depends(); \ | |
91 | (_________p1); \ | |
92 | }) | |
93 | ||
bc6c15bb MD |
94 | #define futex(...) syscall(__NR_futex, __VA_ARGS__) |
95 | #define FUTEX_WAIT 0 | |
96 | #define FUTEX_WAKE 1 | |
97 | ||
7ac06cef MD |
98 | /* |
99 | * This code section can only be included in LGPL 2.1 compatible source code. | |
100 | * See below for the function call wrappers which can be used in code meant to | |
101 | * be only linked with the Userspace RCU library. This comes with a small | |
102 | * performance degradation on the read-side due to the added function calls. | |
103 | * This is required to permit relinking with newer versions of the library. | |
104 | */ | |
105 | ||
106 | /* | |
107 | * If a reader is really non-cooperative and refuses to commit its | |
4f8e3380 | 108 | * urcu_reader.ctr count to memory (there is no barrier in the reader |
7ac06cef MD |
109 | * per-se), kick it after a few loops waiting for it. |
110 | */ | |
111 | #define KICK_READER_LOOPS 10000 | |
112 | ||
bc6c15bb MD |
113 | /* |
114 | * Active attempts to check for reader Q.S. before calling futex(). | |
115 | */ | |
116 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
117 | ||
7ac06cef MD |
118 | #ifdef DEBUG_RCU |
119 | #define rcu_assert(args...) assert(args) | |
120 | #else | |
121 | #define rcu_assert(args...) | |
122 | #endif | |
123 | ||
124 | #ifdef DEBUG_YIELD | |
125 | #include <sched.h> | |
126 | #include <time.h> | |
127 | #include <pthread.h> | |
128 | #include <unistd.h> | |
129 | ||
130 | #define YIELD_READ (1 << 0) | |
131 | #define YIELD_WRITE (1 << 1) | |
132 | ||
133 | /* maximum sleep delay, in us */ | |
134 | #define MAX_SLEEP 50 | |
135 | ||
136 | extern unsigned int yield_active; | |
137 | extern unsigned int __thread rand_yield; | |
138 | ||
139 | static inline void debug_yield_read(void) | |
140 | { | |
141 | if (yield_active & YIELD_READ) | |
142 | if (rand_r(&rand_yield) & 0x1) | |
143 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
144 | } | |
145 | ||
146 | static inline void debug_yield_write(void) | |
147 | { | |
148 | if (yield_active & YIELD_WRITE) | |
149 | if (rand_r(&rand_yield) & 0x1) | |
150 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
151 | } | |
152 | ||
153 | static inline void debug_yield_init(void) | |
154 | { | |
155 | rand_yield = time(NULL) ^ pthread_self(); | |
156 | } | |
157 | #else | |
158 | static inline void debug_yield_read(void) | |
159 | { | |
160 | } | |
161 | ||
162 | static inline void debug_yield_write(void) | |
163 | { | |
164 | } | |
165 | ||
166 | static inline void debug_yield_init(void) | |
167 | { | |
168 | ||
169 | } | |
170 | #endif | |
171 | ||
172 | static inline void reader_barrier() | |
173 | { | |
174 | smp_mb(); | |
175 | } | |
176 | ||
ac258107 | 177 | #define RCU_GP_ONLINE (1UL << 0) |
55570466 | 178 | #define RCU_GP_CTR (1UL << 1) |
ac258107 | 179 | |
7ac06cef MD |
180 | /* |
181 | * Global quiescent period counter with low-order bits unused. | |
182 | * Using a int rather than a char to eliminate false register dependencies | |
183 | * causing stalls on some architectures. | |
184 | */ | |
f0f7dbdd | 185 | extern unsigned long urcu_gp_ctr; |
7ac06cef | 186 | |
4f8e3380 | 187 | struct urcu_reader { |
bd1a5e15 | 188 | /* Data used by both reader and synchronize_rcu() */ |
4f8e3380 | 189 | unsigned long ctr; |
bd1a5e15 MD |
190 | /* Data used for registry */ |
191 | struct list_head head __attribute__((aligned(CACHE_LINE_SIZE))); | |
4f8e3380 MD |
192 | pthread_t tid; |
193 | }; | |
194 | ||
195 | extern struct urcu_reader __thread urcu_reader; | |
7ac06cef | 196 | |
bc6c15bb MD |
197 | extern int gp_futex; |
198 | ||
199 | /* | |
200 | * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. | |
201 | */ | |
202 | static inline void wake_up_gp(void) | |
203 | { | |
ec4e58a3 MD |
204 | if (unlikely(uatomic_read(&gp_futex) == -1)) { |
205 | uatomic_set(&gp_futex, 0); | |
bc6c15bb MD |
206 | futex(&gp_futex, FUTEX_WAKE, 1, |
207 | NULL, NULL, 0); | |
208 | } | |
209 | } | |
210 | ||
47d2f29e MD |
211 | #if (BITS_PER_LONG < 64) |
212 | static inline int rcu_gp_ongoing(unsigned long *value) | |
213 | { | |
214 | unsigned long reader_gp; | |
215 | ||
216 | if (value == NULL) | |
217 | return 0; | |
218 | reader_gp = LOAD_SHARED(*value); | |
219 | return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR); | |
220 | } | |
221 | #else /* !(BITS_PER_LONG < 64) */ | |
f0f7dbdd | 222 | static inline int rcu_gp_ongoing(unsigned long *value) |
7ac06cef | 223 | { |
f0f7dbdd | 224 | unsigned long reader_gp; |
4e560c17 | 225 | |
7ac06cef MD |
226 | if (value == NULL) |
227 | return 0; | |
4e560c17 | 228 | reader_gp = LOAD_SHARED(*value); |
f0f7dbdd | 229 | return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2); |
7ac06cef | 230 | } |
47d2f29e | 231 | #endif /* !(BITS_PER_LONG < 64) */ |
7ac06cef MD |
232 | |
233 | static inline void _rcu_read_lock(void) | |
234 | { | |
4f8e3380 | 235 | rcu_assert(urcu_reader.ctr); |
7ac06cef MD |
236 | } |
237 | ||
238 | static inline void _rcu_read_unlock(void) | |
239 | { | |
240 | } | |
241 | ||
242 | static inline void _rcu_quiescent_state(void) | |
243 | { | |
244 | smp_mb(); | |
4f8e3380 MD |
245 | _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr)); |
246 | smp_mb(); /* write urcu_reader.ctr before read futex */ | |
bc6c15bb | 247 | wake_up_gp(); |
7ac06cef MD |
248 | smp_mb(); |
249 | } | |
250 | ||
251 | static inline void _rcu_thread_offline(void) | |
252 | { | |
253 | smp_mb(); | |
4f8e3380 MD |
254 | STORE_SHARED(urcu_reader.ctr, 0); |
255 | smp_mb(); /* write urcu_reader.ctr before read futex */ | |
bc6c15bb | 256 | wake_up_gp(); |
7ac06cef MD |
257 | } |
258 | ||
259 | static inline void _rcu_thread_online(void) | |
260 | { | |
4f8e3380 | 261 | _STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr)); |
7ac06cef MD |
262 | smp_mb(); |
263 | } | |
264 | ||
265 | /** | |
266 | * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure | |
267 | * meant to be read by RCU read-side critical sections. Returns the assigned | |
268 | * value. | |
269 | * | |
270 | * Documents which pointers will be dereferenced by RCU read-side critical | |
271 | * sections and adds the required memory barriers on architectures requiring | |
272 | * them. It also makes sure the compiler does not reorder code initializing the | |
273 | * data structure before its publication. | |
274 | * | |
275 | * Should match rcu_dereference_pointer(). | |
276 | */ | |
277 | ||
278 | #define _rcu_assign_pointer(p, v) \ | |
279 | ({ \ | |
280 | if (!__builtin_constant_p(v) || \ | |
281 | ((v) != NULL)) \ | |
282 | wmb(); \ | |
283 | STORE_SHARED(p, v); \ | |
284 | }) | |
285 | ||
4d1ce26f MD |
286 | /** |
287 | * _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer | |
288 | * is as expected by "old". If succeeds, returns the previous pointer to the | |
289 | * data structure, which can be safely freed after waiting for a quiescent state | |
290 | * using synchronize_rcu(). If fails (unexpected value), returns old (which | |
291 | * should not be freed !). | |
292 | */ | |
293 | ||
294 | #define _rcu_cmpxchg_pointer(p, old, _new) \ | |
295 | ({ \ | |
296 | if (!__builtin_constant_p(_new) || \ | |
297 | ((_new) != NULL)) \ | |
298 | wmb(); \ | |
ec4e58a3 | 299 | uatomic_cmpxchg(p, old, _new); \ |
4d1ce26f MD |
300 | }) |
301 | ||
7ac06cef MD |
302 | /** |
303 | * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous | |
304 | * pointer to the data structure, which can be safely freed after waiting for a | |
305 | * quiescent state using synchronize_rcu(). | |
306 | */ | |
307 | ||
308 | #define _rcu_xchg_pointer(p, v) \ | |
309 | ({ \ | |
310 | if (!__builtin_constant_p(v) || \ | |
311 | ((v) != NULL)) \ | |
312 | wmb(); \ | |
ec4e58a3 | 313 | uatomic_xchg(p, v); \ |
7ac06cef MD |
314 | }) |
315 | ||
316 | /* | |
317 | * Exchanges the pointer and waits for quiescent state. | |
318 | * The pointer returned can be freed. | |
319 | */ | |
320 | #define _rcu_publish_content(p, v) \ | |
321 | ({ \ | |
322 | void *oldptr; \ | |
323 | oldptr = _rcu_xchg_pointer(p, v); \ | |
324 | synchronize_rcu(); \ | |
325 | oldptr; \ | |
326 | }) | |
327 | ||
328 | #endif /* _URCU_QSBR_STATIC_H */ |