rculfhash: Relax atomicity guarantees required by removal operation
[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 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@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
46 #ifdef __cplusplus
47 extern "C" {
48 #endif
49
50 /*
51 * This code section can only be included in LGPL 2.1 compatible source code.
52 * See below for the function call wrappers which can be used in code meant to
53 * be only linked with the Userspace RCU library. This comes with a small
54 * performance degradation on the read-side due to the added function calls.
55 * This is required to permit relinking with newer versions of the library.
56 */
57
58 #ifdef DEBUG_RCU
59 #define rcu_assert(args...) assert(args)
60 #else
61 #define rcu_assert(args...)
62 #endif
63
64 #ifdef DEBUG_YIELD
65 #include <sched.h>
66 #include <time.h>
67 #include <pthread.h>
68 #include <unistd.h>
69
70 #define YIELD_READ (1 << 0)
71 #define YIELD_WRITE (1 << 1)
72
73 /* maximum sleep delay, in us */
74 #define MAX_SLEEP 50
75
76 extern unsigned int yield_active;
77 extern unsigned int __thread rand_yield;
78
79 static inline void debug_yield_read(void)
80 {
81 if (yield_active & YIELD_READ)
82 if (rand_r(&rand_yield) & 0x1)
83 usleep(rand_r(&rand_yield) % MAX_SLEEP);
84 }
85
86 static inline void debug_yield_write(void)
87 {
88 if (yield_active & YIELD_WRITE)
89 if (rand_r(&rand_yield) & 0x1)
90 usleep(rand_r(&rand_yield) % MAX_SLEEP);
91 }
92
93 static inline void debug_yield_init(void)
94 {
95 rand_yield = time(NULL) ^ pthread_self();
96 }
97 #else
98 static inline void debug_yield_read(void)
99 {
100 }
101
102 static inline void debug_yield_write(void)
103 {
104 }
105
106 static inline void debug_yield_init(void)
107 {
108
109 }
110 #endif
111
112 #define RCU_GP_ONLINE (1UL << 0)
113 #define RCU_GP_CTR (1UL << 1)
114
115 /*
116 * Global quiescent period counter with low-order bits unused.
117 * Using a int rather than a char to eliminate false register dependencies
118 * causing stalls on some architectures.
119 */
120 extern unsigned long rcu_gp_ctr;
121
122 struct rcu_reader {
123 /* Data used by both reader and synchronize_rcu() */
124 unsigned long ctr;
125 /* Data used for registry */
126 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
127 int waiting;
128 pthread_t tid;
129 };
130
131 extern struct rcu_reader __thread rcu_reader;
132
133 extern int32_t gp_futex;
134
135 /*
136 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
137 */
138 static inline void wake_up_gp(void)
139 {
140 if (caa_unlikely(_CMM_LOAD_SHARED(rcu_reader.waiting))) {
141 _CMM_STORE_SHARED(rcu_reader.waiting, 0);
142 cmm_smp_mb();
143 if (uatomic_read(&gp_futex) != -1)
144 return;
145 uatomic_set(&gp_futex, 0);
146 futex_noasync(&gp_futex, FUTEX_WAKE, 1,
147 NULL, NULL, 0);
148 }
149 }
150
151 static inline int rcu_gp_ongoing(unsigned long *ctr)
152 {
153 unsigned long v;
154
155 v = CMM_LOAD_SHARED(*ctr);
156 return v && (v != rcu_gp_ctr);
157 }
158
159 static inline void _rcu_read_lock(void)
160 {
161 rcu_assert(rcu_reader.ctr);
162 }
163
164 static inline void _rcu_read_unlock(void)
165 {
166 }
167
168 static inline void _rcu_quiescent_state(void)
169 {
170 cmm_smp_mb();
171 _CMM_STORE_SHARED(rcu_reader.ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
172 cmm_smp_mb(); /* write rcu_reader.ctr before read futex */
173 wake_up_gp();
174 cmm_smp_mb();
175 }
176
177 static inline void _rcu_thread_offline(void)
178 {
179 cmm_smp_mb();
180 CMM_STORE_SHARED(rcu_reader.ctr, 0);
181 cmm_smp_mb(); /* write rcu_reader.ctr before read futex */
182 wake_up_gp();
183 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
184 }
185
186 static inline void _rcu_thread_online(void)
187 {
188 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
189 _CMM_STORE_SHARED(rcu_reader.ctr, CMM_LOAD_SHARED(rcu_gp_ctr));
190 cmm_smp_mb();
191 }
192
193 #ifdef __cplusplus
194 }
195 #endif
196
197 #endif /* _URCU_QSBR_STATIC_H */
This page took 0.040624 seconds and 4 git commands to generate.