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