Cleanup: urcu: remove unused membarrier "group" parameter
[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 #include <urcu/rand-compat.h>
45 #include <urcu/debug.h>
46
47 #ifdef __cplusplus
48 extern "C" {
49 #endif
50
51 /* Default is RCU_MEMBARRIER */
52 #if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
53 #define RCU_MEMBARRIER
54 #endif
55
56 /*
57 * This code section can only be included in LGPL 2.1 compatible source code.
58 * See below for the function call wrappers which can be used in code meant to
59 * be only linked with the Userspace RCU library. This comes with a small
60 * performance degradation on the read-side due to the added function calls.
61 * This is required to permit relinking with newer versions of the library.
62 */
63
64 /*
65 * The signal number used by the RCU library can be overridden with
66 * -DSIGRCU= when compiling the library.
67 * Provide backward compatibility for liburcu 0.3.x SIGURCU.
68 */
69 #ifdef SIGURCU
70 #define SIGRCU SIGURCU
71 #endif
72
73 #ifndef SIGRCU
74 #define SIGRCU SIGUSR1
75 #endif
76
77 enum rcu_state {
78 RCU_READER_ACTIVE_CURRENT,
79 RCU_READER_ACTIVE_OLD,
80 RCU_READER_INACTIVE,
81 };
82
83 /*
84 * Slave barriers are only guaranteed to be ordered wrt master barriers.
85 *
86 * The pair ordering is detailed as (O: ordered, X: not ordered) :
87 * slave master
88 * slave X O
89 * master O O
90 */
91
92 #ifdef RCU_MEMBARRIER
93 extern int rcu_has_sys_membarrier;
94
95 static inline void smp_mb_slave(void)
96 {
97 if (caa_likely(rcu_has_sys_membarrier))
98 cmm_barrier();
99 else
100 cmm_smp_mb();
101 }
102 #endif
103
104 #ifdef RCU_MB
105 static inline void smp_mb_slave(void)
106 {
107 cmm_smp_mb();
108 }
109 #endif
110
111 #ifdef RCU_SIGNAL
112 static inline void smp_mb_slave(void)
113 {
114 cmm_barrier();
115 }
116 #endif
117
118 /*
119 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
120 * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
121 */
122 #define RCU_GP_COUNT (1UL << 0)
123 /* Use the amount of bits equal to half of the architecture long size */
124 #define RCU_GP_CTR_PHASE (1UL << (sizeof(unsigned long) << 2))
125 #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
126
127 struct rcu_gp {
128 /*
129 * Global grace period counter.
130 * Contains the current RCU_GP_CTR_PHASE.
131 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
132 * Written to only by writer with mutex taken.
133 * Read by both writer and readers.
134 */
135 unsigned long ctr;
136
137 int32_t futex;
138 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
139
140 extern struct rcu_gp rcu_gp;
141
142 struct rcu_reader {
143 /* Data used by both reader and synchronize_rcu() */
144 unsigned long ctr;
145 char need_mb;
146 /* Data used for registry */
147 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
148 pthread_t tid;
149 /* Reader registered flag, for internal checks. */
150 unsigned int registered:1;
151 };
152
153 extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
154
155 /*
156 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
157 */
158 static inline void wake_up_gp(void)
159 {
160 if (caa_unlikely(uatomic_read(&rcu_gp.futex) == -1)) {
161 uatomic_set(&rcu_gp.futex, 0);
162 /*
163 * Ignoring return value until we can make this function
164 * return something (because urcu_die() is not publicly
165 * exposed).
166 */
167 (void) futex_async(&rcu_gp.futex, FUTEX_WAKE, 1,
168 NULL, NULL, 0);
169 }
170 }
171
172 static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
173 {
174 unsigned long v;
175
176 /*
177 * Make sure both tests below are done on the same version of *value
178 * to insure consistency.
179 */
180 v = CMM_LOAD_SHARED(*ctr);
181 if (!(v & RCU_GP_CTR_NEST_MASK))
182 return RCU_READER_INACTIVE;
183 if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE))
184 return RCU_READER_ACTIVE_CURRENT;
185 return RCU_READER_ACTIVE_OLD;
186 }
187
188 /*
189 * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as
190 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
191 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
192 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
193 * _rcu_read_lock() happen before the subsequent read-side critical section.
194 */
195 static inline void _rcu_read_lock_update(unsigned long tmp)
196 {
197 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
198 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp.ctr));
199 smp_mb_slave();
200 } else
201 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp + RCU_GP_COUNT);
202 }
203
204 /*
205 * Enter an RCU read-side critical section.
206 *
207 * The first cmm_barrier() call ensures that the compiler does not reorder
208 * the body of _rcu_read_lock() with a mutex.
209 *
210 * This function and its helper are both less than 10 lines long. The
211 * intent is that this function meets the 10-line criterion in LGPL,
212 * allowing this function to be invoked directly from non-LGPL code.
213 */
214 static inline void _rcu_read_lock(void)
215 {
216 unsigned long tmp;
217
218 urcu_assert(URCU_TLS(rcu_reader).registered);
219 cmm_barrier();
220 tmp = URCU_TLS(rcu_reader).ctr;
221 urcu_assert((tmp & RCU_GP_CTR_NEST_MASK) != RCU_GP_CTR_NEST_MASK);
222 _rcu_read_lock_update(tmp);
223 }
224
225 /*
226 * This is a helper function for _rcu_read_unlock().
227 *
228 * The first smp_mb_slave() call ensures that the critical section is
229 * seen to precede the store to rcu_reader.ctr.
230 * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
231 * before reading the update-side futex.
232 */
233 static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
234 {
235 if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
236 smp_mb_slave();
237 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
238 smp_mb_slave();
239 wake_up_gp();
240 } else
241 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
242 }
243
244 /*
245 * Exit an RCU read-side crtical section. Both this function and its
246 * helper are smaller than 10 lines of code, and are intended to be
247 * usable by non-LGPL code, as called out in LGPL.
248 */
249 static inline void _rcu_read_unlock(void)
250 {
251 unsigned long tmp;
252
253 urcu_assert(URCU_TLS(rcu_reader).registered);
254 tmp = URCU_TLS(rcu_reader).ctr;
255 urcu_assert(tmp & RCU_GP_CTR_NEST_MASK);
256 _rcu_read_unlock_update_and_wakeup(tmp);
257 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
258 }
259
260 /*
261 * Returns whether within a RCU read-side critical section.
262 *
263 * This function is less than 10 lines long. The intent is that this
264 * function meets the 10-line criterion for LGPL, allowing this function
265 * to be invoked directly from non-LGPL code.
266 */
267 static inline int _rcu_read_ongoing(void)
268 {
269 return URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK;
270 }
271
272 #ifdef __cplusplus
273 }
274 #endif
275
276 #endif /* _URCU_STATIC_H */
This page took 0.049534 seconds and 4 git commands to generate.