Add rcu_read_ongoing() API to each urcu flavor
[urcu.git] / urcu / static / urcu.h
1 #ifndef _URCU_STATIC_H
2 #define _URCU_STATIC_H
3
4 /*
5 * urcu-static.h
6 *
7 * Userspace RCU header.
8 *
9 * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
10 * RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
11 *
12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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 <unistd.h>
35 #include <stdint.h>
36
37 #include <urcu/compiler.h>
38 #include <urcu/arch.h>
39 #include <urcu/system.h>
40 #include <urcu/uatomic.h>
41 #include <urcu/list.h>
42 #include <urcu/futex.h>
43 #include <urcu/tls-compat.h>
44
45 #ifdef __cplusplus
46 extern "C" {
47 #endif
48
49 /* Default is RCU_MEMBARRIER */
50 #if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
51 #define RCU_MEMBARRIER
52 #endif
53
54 /*
55 * RCU_MEMBARRIER is only possibly available on Linux. Fallback to RCU_MB
56 * otherwise.
57 */
58 #if !defined(__linux__) && defined(RCU_MEMBARRIER)
59 #undef RCU_MEMBARRIER
60 #define RCU_MB
61 #endif
62
63 #ifdef RCU_MEMBARRIER
64 #include <syscall.h>
65
66 /* If the headers do not support SYS_membarrier, statically use RCU_MB */
67 #ifdef SYS_membarrier
68 # define MEMBARRIER_EXPEDITED (1 << 0)
69 # define MEMBARRIER_DELAYED (1 << 1)
70 # define MEMBARRIER_QUERY (1 << 16)
71 # define membarrier(...) syscall(SYS_membarrier, __VA_ARGS__)
72 #else
73 # undef RCU_MEMBARRIER
74 # define RCU_MB
75 #endif
76 #endif
77
78 /*
79 * This code section can only be included in LGPL 2.1 compatible source code.
80 * See below for the function call wrappers which can be used in code meant to
81 * be only linked with the Userspace RCU library. This comes with a small
82 * performance degradation on the read-side due to the added function calls.
83 * This is required to permit relinking with newer versions of the library.
84 */
85
86 /*
87 * The signal number used by the RCU library can be overridden with
88 * -DSIGRCU= when compiling the library.
89 * Provide backward compatibility for liburcu 0.3.x SIGURCU.
90 */
91 #ifdef SIGURCU
92 #define SIGRCU SIGURCU
93 #endif
94
95 #ifndef SIGRCU
96 #define SIGRCU SIGUSR1
97 #endif
98
99 enum rcu_state {
100 RCU_READER_ACTIVE_CURRENT,
101 RCU_READER_ACTIVE_OLD,
102 RCU_READER_INACTIVE,
103 };
104
105 #ifdef DEBUG_RCU
106 #define rcu_assert(args...) assert(args)
107 #else
108 #define rcu_assert(args...)
109 #endif
110
111 #ifdef DEBUG_YIELD
112 #include <sched.h>
113 #include <time.h>
114 #include <pthread.h>
115 #include <unistd.h>
116
117 #define RCU_YIELD_READ (1 << 0)
118 #define RCU_YIELD_WRITE (1 << 1)
119
120 /*
121 * Updates with RCU_SIGNAL are much slower. Account this in the delay.
122 */
123 #ifdef RCU_SIGNAL
124 /* maximum sleep delay, in us */
125 #define MAX_SLEEP 30000
126 #else
127 #define MAX_SLEEP 50
128 #endif
129
130 extern unsigned int rcu_yield_active;
131 extern DECLARE_URCU_TLS(unsigned int, rcu_rand_yield);
132
133 static inline void rcu_debug_yield_read(void)
134 {
135 if (rcu_yield_active & RCU_YIELD_READ)
136 if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1)
137 usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP);
138 }
139
140 static inline void rcu_debug_yield_write(void)
141 {
142 if (rcu_yield_active & RCU_YIELD_WRITE)
143 if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1)
144 usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP);
145 }
146
147 static inline void rcu_debug_yield_init(void)
148 {
149 URCU_TLS(rcu_rand_yield) = time(NULL) ^ (unsigned long) pthread_self();
150 }
151 #else
152 static inline void rcu_debug_yield_read(void)
153 {
154 }
155
156 static inline void rcu_debug_yield_write(void)
157 {
158 }
159
160 static inline void rcu_debug_yield_init(void)
161 {
162
163 }
164 #endif
165
166 /*
167 * RCU memory barrier broadcast group. Currently, only broadcast to all process
168 * threads is supported (group 0).
169 *
170 * Slave barriers are only guaranteed to be ordered wrt master barriers.
171 *
172 * The pair ordering is detailed as (O: ordered, X: not ordered) :
173 * slave master
174 * slave X O
175 * master O O
176 */
177
178 #define MB_GROUP_ALL 0
179 #define RCU_MB_GROUP MB_GROUP_ALL
180
181 #ifdef RCU_MEMBARRIER
182 extern int rcu_has_sys_membarrier;
183
184 static inline void smp_mb_slave(int group)
185 {
186 if (caa_likely(rcu_has_sys_membarrier))
187 cmm_barrier();
188 else
189 cmm_smp_mb();
190 }
191 #endif
192
193 #ifdef RCU_MB
194 static inline void smp_mb_slave(int group)
195 {
196 cmm_smp_mb();
197 }
198 #endif
199
200 #ifdef RCU_SIGNAL
201 static inline void smp_mb_slave(int group)
202 {
203 cmm_barrier();
204 }
205 #endif
206
207 /*
208 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
209 * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
210 */
211 #define RCU_GP_COUNT (1UL << 0)
212 /* Use the amount of bits equal to half of the architecture long size */
213 #define RCU_GP_CTR_PHASE (1UL << (sizeof(unsigned long) << 2))
214 #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
215
216 /*
217 * Global quiescent period counter with low-order bits unused.
218 * Using a int rather than a char to eliminate false register dependencies
219 * causing stalls on some architectures.
220 */
221 extern unsigned long rcu_gp_ctr;
222
223 struct rcu_reader {
224 /* Data used by both reader and synchronize_rcu() */
225 unsigned long ctr;
226 char need_mb;
227 /* Data used for registry */
228 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
229 pthread_t tid;
230 };
231
232 extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
233
234 extern int32_t rcu_gp_futex;
235
236 /*
237 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
238 */
239 static inline void wake_up_gp(void)
240 {
241 if (caa_unlikely(uatomic_read(&rcu_gp_futex) == -1)) {
242 uatomic_set(&rcu_gp_futex, 0);
243 futex_async(&rcu_gp_futex, FUTEX_WAKE, 1,
244 NULL, NULL, 0);
245 }
246 }
247
248 static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
249 {
250 unsigned long v;
251
252 /*
253 * Make sure both tests below are done on the same version of *value
254 * to insure consistency.
255 */
256 v = CMM_LOAD_SHARED(*ctr);
257 if (!(v & RCU_GP_CTR_NEST_MASK))
258 return RCU_READER_INACTIVE;
259 if (!((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE))
260 return RCU_READER_ACTIVE_CURRENT;
261 return RCU_READER_ACTIVE_OLD;
262 }
263
264 /*
265 * Helper for _rcu_read_lock(). The format of rcu_gp_ctr (as well as
266 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
267 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
268 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
269 * _rcu_read_lock() happen before the subsequent read-side critical section.
270 */
271 static inline void _rcu_read_lock_update(unsigned long tmp)
272 {
273 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
274 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
275 smp_mb_slave(RCU_MB_GROUP);
276 } else
277 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp + RCU_GP_COUNT);
278 }
279
280 /*
281 * Enter an RCU read-side critical section.
282 *
283 * The first cmm_barrier() call ensures that the compiler does not reorder
284 * the body of _rcu_read_lock() with a mutex.
285 *
286 * This function and its helper are both less than 10 lines long. The
287 * intent is that this function meets the 10-line criterion in LGPL,
288 * allowing this function to be invoked directly from non-LGPL code.
289 */
290 static inline void _rcu_read_lock(void)
291 {
292 unsigned long tmp;
293
294 cmm_barrier();
295 tmp = URCU_TLS(rcu_reader).ctr;
296 _rcu_read_lock_update(tmp);
297 }
298
299 /*
300 * This is a helper function for _rcu_read_unlock().
301 *
302 * The first smp_mb_slave() call ensures that the critical section is
303 * seen to precede the store to rcu_reader.ctr.
304 * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
305 * before reading the update-side futex.
306 */
307 static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
308 {
309 if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
310 smp_mb_slave(RCU_MB_GROUP);
311 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
312 smp_mb_slave(RCU_MB_GROUP);
313 wake_up_gp();
314 } else
315 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, URCU_TLS(rcu_reader).ctr - RCU_GP_COUNT);
316 }
317
318 /*
319 * Exit an RCU read-side crtical section. Both this function and its
320 * helper are smaller than 10 lines of code, and are intended to be
321 * usable by non-LGPL code, as called out in LGPL.
322 */
323 static inline void _rcu_read_unlock(void)
324 {
325 unsigned long tmp;
326
327 tmp = URCU_TLS(rcu_reader).ctr;
328 _rcu_read_unlock_update_and_wakeup(tmp);
329 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
330 }
331
332 /*
333 * Returns whether within a RCU read-side critical section.
334 *
335 * This function is less than 10 lines long. The intent is that this
336 * function meets the 10-line criterion for LGPL, allowing this function
337 * to be invoked directly from non-LGPL code.
338 */
339 static inline int _rcu_read_ongoing(void)
340 {
341 return URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK;
342 }
343
344 #ifdef __cplusplus
345 }
346 #endif
347
348 #endif /* _URCU_STATIC_H */
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