rculfhash: number of logically removed nodes should not appear in API
[urcu.git] / urcu / static / urcu-qsbr.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 *
6982d6d7 12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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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>
bc6c15bb 36#include <unistd.h>
6d841bc2 37#include <stdint.h>
7ac06cef 38
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39#include <urcu/compiler.h>
40#include <urcu/arch.h>
7e30abe3 41#include <urcu/system.h>
a2e7bf9c 42#include <urcu/uatomic.h>
4f8e3380 43#include <urcu/list.h>
41849996 44#include <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
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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
76extern unsigned int yield_active;
77extern unsigned int __thread rand_yield;
78
79static 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
86static 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
93static inline void debug_yield_init(void)
94{
95 rand_yield = time(NULL) ^ pthread_self();
96}
97#else
98static inline void debug_yield_read(void)
99{
100}
101
102static inline void debug_yield_write(void)
103{
104}
105
106static inline void debug_yield_init(void)
107{
108
109}
110#endif
111
ac258107 112#define RCU_GP_ONLINE (1UL << 0)
55570466 113#define RCU_GP_CTR (1UL << 1)
ac258107 114
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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 */
02be5561 120extern unsigned long rcu_gp_ctr;
7ac06cef 121
02be5561 122struct rcu_reader {
bd1a5e15 123 /* Data used by both reader and synchronize_rcu() */
4f8e3380 124 unsigned long ctr;
bd1a5e15 125 /* Data used for registry */
16aa9ee8 126 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
83a2c421 127 int waiting;
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128 pthread_t tid;
129};
130
02be5561 131extern struct rcu_reader __thread rcu_reader;
7ac06cef 132
6d841bc2 133extern int32_t gp_futex;
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134
135/*
136 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
137 */
138static inline void wake_up_gp(void)
139{
a0b7f7ea 140 if (caa_unlikely(_CMM_LOAD_SHARED(rcu_reader.waiting))) {
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141 _CMM_STORE_SHARED(rcu_reader.waiting, 0);
142 cmm_smp_mb();
143 if (uatomic_read(&gp_futex) != -1)
144 return;
ec4e58a3 145 uatomic_set(&gp_futex, 0);
0854ccff 146 futex_noasync(&gp_futex, FUTEX_WAKE, 1,
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147 NULL, NULL, 0);
148 }
149}
150
e26fa029 151static inline int rcu_gp_ongoing(unsigned long *ctr)
7ac06cef 152{
e26fa029 153 unsigned long v;
4e560c17 154
6cf3827c 155 v = CMM_LOAD_SHARED(*ctr);
92cb20a8 156 return v && (v != rcu_gp_ctr);
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157}
158
159static inline void _rcu_read_lock(void)
160{
02be5561 161 rcu_assert(rcu_reader.ctr);
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162}
163
164static inline void _rcu_read_unlock(void)
165{
166}
167
168static inline void _rcu_quiescent_state(void)
169{
5481ddb3 170 cmm_smp_mb();
6cf3827c 171 _CMM_STORE_SHARED(rcu_reader.ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
5481ddb3 172 cmm_smp_mb(); /* write rcu_reader.ctr before read futex */
bc6c15bb 173 wake_up_gp();
5481ddb3 174 cmm_smp_mb();
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175}
176
177static inline void _rcu_thread_offline(void)
178{
5481ddb3 179 cmm_smp_mb();
6cf3827c 180 CMM_STORE_SHARED(rcu_reader.ctr, 0);
5481ddb3 181 cmm_smp_mb(); /* write rcu_reader.ctr before read futex */
bc6c15bb 182 wake_up_gp();
5481ddb3 183 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
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184}
185
186static inline void _rcu_thread_online(void)
187{
5481ddb3 188 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
6cf3827c 189 _CMM_STORE_SHARED(rcu_reader.ctr, CMM_LOAD_SHARED(rcu_gp_ctr));
5481ddb3 190 cmm_smp_mb();
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191}
192
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193#ifdef __cplusplus
194}
195#endif
196
7ac06cef 197#endif /* _URCU_QSBR_STATIC_H */
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