wfstack: implement cds_wfs_pop_all and iterators, document API
[urcu.git] / urcu / static / urcu-qsbr.h
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 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 <assert.h>
35 #include <limits.h>
36 #include <unistd.h>
37 #include <stdint.h>
38
39 #include <urcu/compiler.h>
40 #include <urcu/arch.h>
41 #include <urcu/system.h>
42 #include <urcu/uatomic.h>
43 #include <urcu/list.h>
44 #include <urcu/futex.h>
45 #include <urcu/tls-compat.h>
46
47 #ifdef __cplusplus
48 extern "C" {
49 #endif
50
51 /*
52 * This code section can only be included in LGPL 2.1 compatible source code.
53 * See below for the function call wrappers which can be used in code meant to
54 * be only linked with the Userspace RCU library. This comes with a small
55 * performance degradation on the read-side due to the added function calls.
56 * This is required to permit relinking with newer versions of the library.
57 */
58
59 #ifdef DEBUG_RCU
60 #define rcu_assert(args...) assert(args)
61 #else
62 #define rcu_assert(args...)
63 #endif
64
65 #ifdef DEBUG_YIELD
66 #include <sched.h>
67 #include <time.h>
68 #include <pthread.h>
69 #include <unistd.h>
70
71 #define YIELD_READ (1 << 0)
72 #define YIELD_WRITE (1 << 1)
73
74 /* maximum sleep delay, in us */
75 #define MAX_SLEEP 50
76
77 extern unsigned int yield_active;
78 extern DECLARE_URCU_TLS(unsigned int, rand_yield);
79
80 static inline void debug_yield_read(void)
81 {
82 if (yield_active & YIELD_READ)
83 if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
84 usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
85 }
86
87 static inline void debug_yield_write(void)
88 {
89 if (yield_active & YIELD_WRITE)
90 if (rand_r(&URCU_TLS(rand_yield)) & 0x1)
91 usleep(rand_r(&URCU_TLS(rand_yield)) % MAX_SLEEP);
92 }
93
94 static inline void debug_yield_init(void)
95 {
96 URCU_TLS(rand_yield) = time(NULL) ^ pthread_self();
97 }
98 #else
99 static inline void debug_yield_read(void)
100 {
101 }
102
103 static inline void debug_yield_write(void)
104 {
105 }
106
107 static inline void debug_yield_init(void)
108 {
109
110 }
111 #endif
112
113 #define RCU_GP_ONLINE (1UL << 0)
114 #define RCU_GP_CTR (1UL << 1)
115
116 /*
117 * Global quiescent period counter with low-order bits unused.
118 * Using a int rather than a char to eliminate false register dependencies
119 * causing stalls on some architectures.
120 */
121 extern unsigned long rcu_gp_ctr;
122
123 struct rcu_reader {
124 /* Data used by both reader and synchronize_rcu() */
125 unsigned long ctr;
126 /* Data used for registry */
127 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
128 int waiting;
129 pthread_t tid;
130 };
131
132 extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
133
134 extern int32_t gp_futex;
135
136 /*
137 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
138 */
139 static inline void wake_up_gp(void)
140 {
141 if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader).waiting))) {
142 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).waiting, 0);
143 cmm_smp_mb();
144 if (uatomic_read(&gp_futex) != -1)
145 return;
146 uatomic_set(&gp_futex, 0);
147 futex_noasync(&gp_futex, FUTEX_WAKE, 1,
148 NULL, NULL, 0);
149 }
150 }
151
152 static inline int rcu_gp_ongoing(unsigned long *ctr)
153 {
154 unsigned long v;
155
156 v = CMM_LOAD_SHARED(*ctr);
157 return v && (v != rcu_gp_ctr);
158 }
159
160 /*
161 * Enter an RCU read-side critical section.
162 *
163 * This function is less than 10 lines long. The intent is that this
164 * function meets the 10-line criterion for LGPL, allowing this function
165 * to be invoked directly from non-LGPL code.
166 */
167 static inline void _rcu_read_lock(void)
168 {
169 rcu_assert(URCU_TLS(rcu_reader).ctr);
170 }
171
172 /*
173 * Exit an RCU read-side critical section.
174 *
175 * This function is less than 10 lines long. The intent is that this
176 * function meets the 10-line criterion for LGPL, allowing this function
177 * to be invoked directly from non-LGPL code.
178 */
179 static inline void _rcu_read_unlock(void)
180 {
181 }
182
183 /*
184 * Inform RCU of a quiescent state.
185 *
186 * This function is less than 10 lines long. The intent is that this
187 * function meets the 10-line criterion for LGPL, allowing this function
188 * to be invoked directly from non-LGPL code.
189 */
190 static inline void _rcu_quiescent_state(void)
191 {
192 cmm_smp_mb();
193 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
194 cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
195 wake_up_gp();
196 cmm_smp_mb();
197 }
198
199 /*
200 * Take a thread offline, prohibiting it from entering further RCU
201 * read-side critical sections.
202 *
203 * This function is less than 10 lines long. The intent is that this
204 * function meets the 10-line criterion for LGPL, allowing this function
205 * to be invoked directly from non-LGPL code.
206 */
207 static inline void _rcu_thread_offline(void)
208 {
209 cmm_smp_mb();
210 CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, 0);
211 cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
212 wake_up_gp();
213 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
214 }
215
216 /*
217 * Bring a thread online, allowing it to once again enter RCU
218 * read-side critical sections.
219 *
220 * This function is less than 10 lines long. The intent is that this
221 * function meets the 10-line criterion for LGPL, allowing this function
222 * to be invoked directly from non-LGPL code.
223 */
224 static inline void _rcu_thread_online(void)
225 {
226 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
227 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, CMM_LOAD_SHARED(rcu_gp_ctr));
228 cmm_smp_mb();
229 }
230
231 #ifdef __cplusplus
232 }
233 #endif
234
235 #endif /* _URCU_QSBR_STATIC_H */
This page took 0.033423 seconds and 4 git commands to generate.