Fix: Move rand-compat to private src dir
[urcu.git] / include / 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 #include <urcu/debug.h>
45
46 #ifdef __cplusplus
47 extern "C" {
48 #endif
49
50 /* Default is RCU_MEMBARRIER */
51 #if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
52 #define RCU_MEMBARRIER
53 #endif
54
55 /*
56 * This code section can only be included in LGPL 2.1 compatible source code.
57 * See below for the function call wrappers which can be used in code meant to
58 * be only linked with the Userspace RCU library. This comes with a small
59 * performance degradation on the read-side due to the added function calls.
60 * This is required to permit relinking with newer versions of the library.
61 */
62
63 /*
64 * The signal number used by the RCU library can be overridden with
65 * -DSIGRCU= when compiling the library.
66 * Provide backward compatibility for liburcu 0.3.x SIGURCU.
67 */
68 #ifdef SIGURCU
69 #define SIGRCU SIGURCU
70 #endif
71
72 #ifndef SIGRCU
73 #define SIGRCU SIGUSR1
74 #endif
75
76 enum rcu_state {
77 RCU_READER_ACTIVE_CURRENT,
78 RCU_READER_ACTIVE_OLD,
79 RCU_READER_INACTIVE,
80 };
81
82 /*
83 * Slave barriers are only guaranteed to be ordered wrt master barriers.
84 *
85 * The pair ordering is detailed as (O: ordered, X: not ordered) :
86 * slave master
87 * slave X O
88 * master O O
89 */
90
91 #ifdef RCU_MEMBARRIER
92 extern int rcu_has_sys_membarrier;
93
94 static inline void smp_mb_slave(void)
95 {
96 if (caa_likely(rcu_has_sys_membarrier))
97 cmm_barrier();
98 else
99 cmm_smp_mb();
100 }
101 #endif
102
103 #ifdef RCU_MB
104 static inline void smp_mb_slave(void)
105 {
106 cmm_smp_mb();
107 }
108 #endif
109
110 #ifdef RCU_SIGNAL
111 static inline void smp_mb_slave(void)
112 {
113 cmm_barrier();
114 }
115 #endif
116
117 /*
118 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
119 * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
120 */
121 #define RCU_GP_COUNT (1UL << 0)
122 /* Use the amount of bits equal to half of the architecture long size */
123 #define RCU_GP_CTR_PHASE (1UL << (sizeof(unsigned long) << 2))
124 #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
125
126 struct rcu_gp {
127 /*
128 * Global grace period counter.
129 * Contains the current RCU_GP_CTR_PHASE.
130 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
131 * Written to only by writer with mutex taken.
132 * Read by both writer and readers.
133 */
134 unsigned long ctr;
135
136 int32_t futex;
137 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
138
139 extern struct rcu_gp rcu_gp;
140
141 struct rcu_reader {
142 /* Data used by both reader and synchronize_rcu() */
143 unsigned long ctr;
144 char need_mb;
145 /* Data used for registry */
146 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
147 pthread_t tid;
148 /* Reader registered flag, for internal checks. */
149 unsigned int registered:1;
150 };
151
152 extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
153
154 /*
155 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
156 */
157 static inline void wake_up_gp(void)
158 {
159 if (caa_unlikely(uatomic_read(&rcu_gp.futex) == -1)) {
160 uatomic_set(&rcu_gp.futex, 0);
161 /*
162 * Ignoring return value until we can make this function
163 * return something (because urcu_die() is not publicly
164 * exposed).
165 */
166 (void) futex_async(&rcu_gp.futex, FUTEX_WAKE, 1,
167 NULL, NULL, 0);
168 }
169 }
170
171 static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
172 {
173 unsigned long v;
174
175 /*
176 * Make sure both tests below are done on the same version of *value
177 * to insure consistency.
178 */
179 v = CMM_LOAD_SHARED(*ctr);
180 if (!(v & RCU_GP_CTR_NEST_MASK))
181 return RCU_READER_INACTIVE;
182 if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE))
183 return RCU_READER_ACTIVE_CURRENT;
184 return RCU_READER_ACTIVE_OLD;
185 }
186
187 /*
188 * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as
189 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
190 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
191 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
192 * _rcu_read_lock() happen before the subsequent read-side critical section.
193 */
194 static inline void _rcu_read_lock_update(unsigned long tmp)
195 {
196 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
197 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp.ctr));
198 smp_mb_slave();
199 } else
200 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp + RCU_GP_COUNT);
201 }
202
203 /*
204 * Enter an RCU read-side critical section.
205 *
206 * The first cmm_barrier() call ensures that the compiler does not reorder
207 * the body of _rcu_read_lock() with a mutex.
208 *
209 * This function and its helper are both less than 10 lines long. The
210 * intent is that this function meets the 10-line criterion in LGPL,
211 * allowing this function to be invoked directly from non-LGPL code.
212 */
213 static inline void _rcu_read_lock(void)
214 {
215 unsigned long tmp;
216
217 urcu_assert(URCU_TLS(rcu_reader).registered);
218 cmm_barrier();
219 tmp = URCU_TLS(rcu_reader).ctr;
220 urcu_assert((tmp & RCU_GP_CTR_NEST_MASK) != RCU_GP_CTR_NEST_MASK);
221 _rcu_read_lock_update(tmp);
222 }
223
224 /*
225 * This is a helper function for _rcu_read_unlock().
226 *
227 * The first smp_mb_slave() call ensures that the critical section is
228 * seen to precede the store to rcu_reader.ctr.
229 * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
230 * before reading the update-side futex.
231 */
232 static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
233 {
234 if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
235 smp_mb_slave();
236 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
237 smp_mb_slave();
238 wake_up_gp();
239 } else
240 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
241 }
242
243 /*
244 * Exit an RCU read-side crtical section. Both this function and its
245 * helper are smaller than 10 lines of code, and are intended to be
246 * usable by non-LGPL code, as called out in LGPL.
247 */
248 static inline void _rcu_read_unlock(void)
249 {
250 unsigned long tmp;
251
252 urcu_assert(URCU_TLS(rcu_reader).registered);
253 tmp = URCU_TLS(rcu_reader).ctr;
254 urcu_assert(tmp & RCU_GP_CTR_NEST_MASK);
255 _rcu_read_unlock_update_and_wakeup(tmp);
256 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
257 }
258
259 /*
260 * Returns whether within a RCU read-side critical section.
261 *
262 * This function is less than 10 lines long. The intent is that this
263 * function meets the 10-line criterion for LGPL, allowing this function
264 * to be invoked directly from non-LGPL code.
265 */
266 static inline int _rcu_read_ongoing(void)
267 {
268 return URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK;
269 }
270
271 #ifdef __cplusplus
272 }
273 #endif
274
275 #endif /* _URCU_STATIC_H */
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