Add extern "C" to support linking userspace RCU library with C++ applications
[urcu.git] / urcu-static.h
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1#ifndef _URCU_STATIC_H
2#define _URCU_STATIC_H
3
4/*
5 * urcu-static.h
6 *
d2d23035 7 * Userspace RCU header.
adcfce54 8 *
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9 * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
10 * dynamically with the userspace rcu library.
adcfce54 11 *
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12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
13 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
adcfce54 14 *
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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
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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>
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34#include <syscall.h>
35#include <unistd.h>
adcfce54 36
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37#include <urcu/compiler.h>
38#include <urcu/arch.h>
7e30abe3 39#include <urcu/system.h>
48d848c7 40#include <urcu/uatomic_arch.h>
e3b0cef0 41#include <urcu/list.h>
0854ccff 42#include <urcu/urcu-futex.h>
bc6c15bb 43
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44#ifdef __cplusplus
45extern "C" {
46#endif
47
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48/*
49 * This code section can only be included in LGPL 2.1 compatible source code.
50 * See below for the function call wrappers which can be used in code meant to
51 * be only linked with the Userspace RCU library. This comes with a small
52 * performance degradation on the read-side due to the added function calls.
53 * This is required to permit relinking with newer versions of the library.
54 */
55
56/*
57 * The signal number used by the RCU library can be overridden with
58 * -DSIGURCU= when compiling the library.
59 */
60#ifndef SIGURCU
61#define SIGURCU SIGUSR1
62#endif
63
64/*
65 * If a reader is really non-cooperative and refuses to commit its
66 * urcu_active_readers count to memory (there is no barrier in the reader
67 * per-se), kick it after a few loops waiting for it.
68 */
69#define KICK_READER_LOOPS 10000
70
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71/*
72 * Active attempts to check for reader Q.S. before calling futex().
73 */
74#define RCU_QS_ACTIVE_ATTEMPTS 100
75
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76#ifdef DEBUG_RCU
77#define rcu_assert(args...) assert(args)
78#else
79#define rcu_assert(args...)
80#endif
81
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82#ifdef DEBUG_YIELD
83#include <sched.h>
84#include <time.h>
85#include <pthread.h>
86#include <unistd.h>
87
88#define YIELD_READ (1 << 0)
89#define YIELD_WRITE (1 << 1)
90
b4ce1526 91/*
0a1d290b 92 * Updates without URCU_MB are much slower. Account this in
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93 * the delay.
94 */
0a1d290b 95#ifdef URCU_MB
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96/* maximum sleep delay, in us */
97#define MAX_SLEEP 50
98#else
99#define MAX_SLEEP 30000
100#endif
101
102extern unsigned int yield_active;
103extern unsigned int __thread rand_yield;
104
105static inline void debug_yield_read(void)
106{
107 if (yield_active & YIELD_READ)
108 if (rand_r(&rand_yield) & 0x1)
109 usleep(rand_r(&rand_yield) % MAX_SLEEP);
110}
111
112static inline void debug_yield_write(void)
113{
114 if (yield_active & YIELD_WRITE)
115 if (rand_r(&rand_yield) & 0x1)
116 usleep(rand_r(&rand_yield) % MAX_SLEEP);
117}
118
119static inline void debug_yield_init(void)
120{
121 rand_yield = time(NULL) ^ pthread_self();
122}
123#else
124static inline void debug_yield_read(void)
125{
126}
127
128static inline void debug_yield_write(void)
129{
130}
131
132static inline void debug_yield_init(void)
133{
134
135}
136#endif
137
0a1d290b 138#ifdef URCU_MB
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139static inline void reader_barrier()
140{
141 smp_mb();
142}
143#else
144static inline void reader_barrier()
145{
146 barrier();
147}
148#endif
149
150/*
151 * The trick here is that RCU_GP_CTR_BIT must be a multiple of 8 so we can use a
152 * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
153 */
154#define RCU_GP_COUNT (1UL << 0)
155/* Use the amount of bits equal to half of the architecture long size */
156#define RCU_GP_CTR_BIT (1UL << (sizeof(long) << 2))
157#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1)
158
159/*
160 * Global quiescent period counter with low-order bits unused.
161 * Using a int rather than a char to eliminate false register dependencies
162 * causing stalls on some architectures.
163 */
164extern long urcu_gp_ctr;
165
e3b0cef0 166struct urcu_reader {
bd1a5e15 167 /* Data used by both reader and synchronize_rcu() */
e3b0cef0 168 long ctr;
e3b0cef0 169 char need_mb;
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170 /* Data used for registry */
171 struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
172 pthread_t tid;
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173};
174
175extern struct urcu_reader __thread urcu_reader;
adcfce54 176
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177extern int gp_futex;
178
179/*
180 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
181 */
182static inline void wake_up_gp(void)
183{
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184 if (unlikely(uatomic_read(&gp_futex) == -1)) {
185 uatomic_set(&gp_futex, 0);
0854ccff 186 futex_async(&gp_futex, FUTEX_WAKE, 1,
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187 NULL, NULL, 0);
188 }
189}
190
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191static inline int rcu_old_gp_ongoing(long *value)
192{
193 long v;
194
195 if (value == NULL)
196 return 0;
197 /*
198 * Make sure both tests below are done on the same version of *value
199 * to insure consistency.
200 */
201 v = LOAD_SHARED(*value);
202 return (v & RCU_GP_CTR_NEST_MASK) &&
203 ((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT);
204}
205
206static inline void _rcu_read_lock(void)
207{
208 long tmp;
209
e3b0cef0 210 tmp = urcu_reader.ctr;
adcfce54 211 /* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */
67ef1a2c 212 if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
e3b0cef0 213 _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
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214 /*
215 * Set active readers count for outermost nesting level before
216 * accessing the pointer. See force_mb_all_threads().
217 */
218 reader_barrier();
219 } else {
e3b0cef0 220 _STORE_SHARED(urcu_reader.ctr, tmp + RCU_GP_COUNT);
67ef1a2c 221 }
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222}
223
224static inline void _rcu_read_unlock(void)
225{
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226 long tmp;
227
e3b0cef0 228 tmp = urcu_reader.ctr;
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229 /*
230 * Finish using rcu before decrementing the pointer.
231 * See force_mb_all_threads().
232 */
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233 if (likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
234 reader_barrier();
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235 _STORE_SHARED(urcu_reader.ctr, urcu_reader.ctr - RCU_GP_COUNT);
236 /* write urcu_reader.ctr before read futex */
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237 reader_barrier();
238 wake_up_gp();
239 } else {
e3b0cef0 240 _STORE_SHARED(urcu_reader.ctr, urcu_reader.ctr - RCU_GP_COUNT);
bc6c15bb 241 }
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242}
243
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244#ifdef __cplusplus
245}
246#endif
247
adcfce54 248#endif /* _URCU_STATIC_H */
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