Add extern "C" to support linking userspace RCU library with C++ applications
[urcu.git] / urcu-qsbr-static.h
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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@polymtl.ca>
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>
f0f7dbdd 35#include <limits.h>
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36#include <syscall.h>
37#include <unistd.h>
7ac06cef 38
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39#include <urcu/compiler.h>
40#include <urcu/arch.h>
7e30abe3 41#include <urcu/system.h>
48d848c7 42#include <urcu/uatomic_arch.h>
4f8e3380 43#include <urcu/list.h>
0854ccff 44#include <urcu/urcu-futex.h>
bc6c15bb 45
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46#ifdef __cplusplus
47extern "C" {
48#endif
49
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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/*
59 * If a reader is really non-cooperative and refuses to commit its
4f8e3380 60 * urcu_reader.ctr count to memory (there is no barrier in the reader
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61 * per-se), kick it after a few loops waiting for it.
62 */
63#define KICK_READER_LOOPS 10000
64
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65/*
66 * Active attempts to check for reader Q.S. before calling futex().
67 */
68#define RCU_QS_ACTIVE_ATTEMPTS 100
69
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70#ifdef DEBUG_RCU
71#define rcu_assert(args...) assert(args)
72#else
73#define rcu_assert(args...)
74#endif
75
76#ifdef DEBUG_YIELD
77#include <sched.h>
78#include <time.h>
79#include <pthread.h>
80#include <unistd.h>
81
82#define YIELD_READ (1 << 0)
83#define YIELD_WRITE (1 << 1)
84
85/* maximum sleep delay, in us */
86#define MAX_SLEEP 50
87
88extern unsigned int yield_active;
89extern unsigned int __thread rand_yield;
90
91static inline void debug_yield_read(void)
92{
93 if (yield_active & YIELD_READ)
94 if (rand_r(&rand_yield) & 0x1)
95 usleep(rand_r(&rand_yield) % MAX_SLEEP);
96}
97
98static inline void debug_yield_write(void)
99{
100 if (yield_active & YIELD_WRITE)
101 if (rand_r(&rand_yield) & 0x1)
102 usleep(rand_r(&rand_yield) % MAX_SLEEP);
103}
104
105static inline void debug_yield_init(void)
106{
107 rand_yield = time(NULL) ^ pthread_self();
108}
109#else
110static inline void debug_yield_read(void)
111{
112}
113
114static inline void debug_yield_write(void)
115{
116}
117
118static inline void debug_yield_init(void)
119{
120
121}
122#endif
123
124static inline void reader_barrier()
125{
126 smp_mb();
127}
128
ac258107 129#define RCU_GP_ONLINE (1UL << 0)
55570466 130#define RCU_GP_CTR (1UL << 1)
ac258107 131
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132/*
133 * Global quiescent period counter with low-order bits unused.
134 * Using a int rather than a char to eliminate false register dependencies
135 * causing stalls on some architectures.
136 */
f0f7dbdd 137extern unsigned long urcu_gp_ctr;
7ac06cef 138
4f8e3380 139struct urcu_reader {
bd1a5e15 140 /* Data used by both reader and synchronize_rcu() */
4f8e3380 141 unsigned long ctr;
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142 /* Data used for registry */
143 struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
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144 pthread_t tid;
145};
146
147extern struct urcu_reader __thread urcu_reader;
7ac06cef 148
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149extern int gp_futex;
150
151/*
152 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
153 */
154static inline void wake_up_gp(void)
155{
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156 if (unlikely(uatomic_read(&gp_futex) == -1)) {
157 uatomic_set(&gp_futex, 0);
0854ccff 158 futex_noasync(&gp_futex, FUTEX_WAKE, 1,
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159 NULL, NULL, 0);
160 }
161}
162
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163#if (BITS_PER_LONG < 64)
164static inline int rcu_gp_ongoing(unsigned long *value)
165{
166 unsigned long reader_gp;
167
168 if (value == NULL)
169 return 0;
170 reader_gp = LOAD_SHARED(*value);
171 return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
172}
173#else /* !(BITS_PER_LONG < 64) */
f0f7dbdd 174static inline int rcu_gp_ongoing(unsigned long *value)
7ac06cef 175{
f0f7dbdd 176 unsigned long reader_gp;
4e560c17 177
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178 if (value == NULL)
179 return 0;
4e560c17 180 reader_gp = LOAD_SHARED(*value);
f0f7dbdd 181 return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
7ac06cef 182}
47d2f29e 183#endif /* !(BITS_PER_LONG < 64) */
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184
185static inline void _rcu_read_lock(void)
186{
4f8e3380 187 rcu_assert(urcu_reader.ctr);
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188}
189
190static inline void _rcu_read_unlock(void)
191{
192}
193
194static inline void _rcu_quiescent_state(void)
195{
196 smp_mb();
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197 _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
198 smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb 199 wake_up_gp();
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200 smp_mb();
201}
202
203static inline void _rcu_thread_offline(void)
204{
205 smp_mb();
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206 STORE_SHARED(urcu_reader.ctr, 0);
207 smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb 208 wake_up_gp();
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209}
210
211static inline void _rcu_thread_online(void)
212{
4f8e3380 213 _STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr));
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214 smp_mb();
215}
216
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217#ifdef __cplusplus
218}
219#endif
220
7ac06cef 221#endif /* _URCU_QSBR_STATIC_H */
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