Restrict supported arch ot P6+ on Intel x86 32.
[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>
7ac06cef 44
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45#define futex(...) syscall(__NR_futex, __VA_ARGS__)
46#define FUTEX_WAIT 0
47#define FUTEX_WAKE 1
48
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49/*
50 * This code section can only be included in LGPL 2.1 compatible source code.
51 * See below for the function call wrappers which can be used in code meant to
52 * be only linked with the Userspace RCU library. This comes with a small
53 * performance degradation on the read-side due to the added function calls.
54 * This is required to permit relinking with newer versions of the library.
55 */
56
57/*
58 * If a reader is really non-cooperative and refuses to commit its
4f8e3380 59 * urcu_reader.ctr count to memory (there is no barrier in the reader
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60 * per-se), kick it after a few loops waiting for it.
61 */
62#define KICK_READER_LOOPS 10000
63
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64/*
65 * Active attempts to check for reader Q.S. before calling futex().
66 */
67#define RCU_QS_ACTIVE_ATTEMPTS 100
68
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69#ifdef DEBUG_RCU
70#define rcu_assert(args...) assert(args)
71#else
72#define rcu_assert(args...)
73#endif
74
75#ifdef DEBUG_YIELD
76#include <sched.h>
77#include <time.h>
78#include <pthread.h>
79#include <unistd.h>
80
81#define YIELD_READ (1 << 0)
82#define YIELD_WRITE (1 << 1)
83
84/* maximum sleep delay, in us */
85#define MAX_SLEEP 50
86
87extern unsigned int yield_active;
88extern unsigned int __thread rand_yield;
89
90static inline void debug_yield_read(void)
91{
92 if (yield_active & YIELD_READ)
93 if (rand_r(&rand_yield) & 0x1)
94 usleep(rand_r(&rand_yield) % MAX_SLEEP);
95}
96
97static inline void debug_yield_write(void)
98{
99 if (yield_active & YIELD_WRITE)
100 if (rand_r(&rand_yield) & 0x1)
101 usleep(rand_r(&rand_yield) % MAX_SLEEP);
102}
103
104static inline void debug_yield_init(void)
105{
106 rand_yield = time(NULL) ^ pthread_self();
107}
108#else
109static inline void debug_yield_read(void)
110{
111}
112
113static inline void debug_yield_write(void)
114{
115}
116
117static inline void debug_yield_init(void)
118{
119
120}
121#endif
122
123static inline void reader_barrier()
124{
125 smp_mb();
126}
127
ac258107 128#define RCU_GP_ONLINE (1UL << 0)
55570466 129#define RCU_GP_CTR (1UL << 1)
ac258107 130
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131/*
132 * Global quiescent period counter with low-order bits unused.
133 * Using a int rather than a char to eliminate false register dependencies
134 * causing stalls on some architectures.
135 */
f0f7dbdd 136extern unsigned long urcu_gp_ctr;
7ac06cef 137
4f8e3380 138struct urcu_reader {
bd1a5e15 139 /* Data used by both reader and synchronize_rcu() */
4f8e3380 140 unsigned long ctr;
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141 /* Data used for registry */
142 struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
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143 pthread_t tid;
144};
145
146extern struct urcu_reader __thread urcu_reader;
7ac06cef 147
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148extern int gp_futex;
149
150/*
151 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
152 */
153static inline void wake_up_gp(void)
154{
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155 if (unlikely(uatomic_read(&gp_futex) == -1)) {
156 uatomic_set(&gp_futex, 0);
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157 futex(&gp_futex, FUTEX_WAKE, 1,
158 NULL, NULL, 0);
159 }
160}
161
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162#if (BITS_PER_LONG < 64)
163static inline int rcu_gp_ongoing(unsigned long *value)
164{
165 unsigned long reader_gp;
166
167 if (value == NULL)
168 return 0;
169 reader_gp = LOAD_SHARED(*value);
170 return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
171}
172#else /* !(BITS_PER_LONG < 64) */
f0f7dbdd 173static inline int rcu_gp_ongoing(unsigned long *value)
7ac06cef 174{
f0f7dbdd 175 unsigned long reader_gp;
4e560c17 176
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177 if (value == NULL)
178 return 0;
4e560c17 179 reader_gp = LOAD_SHARED(*value);
f0f7dbdd 180 return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
7ac06cef 181}
47d2f29e 182#endif /* !(BITS_PER_LONG < 64) */
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183
184static inline void _rcu_read_lock(void)
185{
4f8e3380 186 rcu_assert(urcu_reader.ctr);
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187}
188
189static inline void _rcu_read_unlock(void)
190{
191}
192
193static inline void _rcu_quiescent_state(void)
194{
195 smp_mb();
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196 _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
197 smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb 198 wake_up_gp();
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199 smp_mb();
200}
201
202static inline void _rcu_thread_offline(void)
203{
204 smp_mb();
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205 STORE_SHARED(urcu_reader.ctr, 0);
206 smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb 207 wake_up_gp();
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208}
209
210static inline void _rcu_thread_online(void)
211{
4f8e3380 212 _STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr));
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213 smp_mb();
214}
215
7ac06cef 216#endif /* _URCU_QSBR_STATIC_H */
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