s390 uatomic arch fix
[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/*
47 * This code section can only be included in LGPL 2.1 compatible source code.
48 * See below for the function call wrappers which can be used in code meant to
49 * be only linked with the Userspace RCU library. This comes with a small
50 * performance degradation on the read-side due to the added function calls.
51 * This is required to permit relinking with newer versions of the library.
52 */
53
54/*
55 * If a reader is really non-cooperative and refuses to commit its
4f8e3380 56 * urcu_reader.ctr count to memory (there is no barrier in the reader
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57 * per-se), kick it after a few loops waiting for it.
58 */
59#define KICK_READER_LOOPS 10000
60
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61/*
62 * Active attempts to check for reader Q.S. before calling futex().
63 */
64#define RCU_QS_ACTIVE_ATTEMPTS 100
65
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66#ifdef DEBUG_RCU
67#define rcu_assert(args...) assert(args)
68#else
69#define rcu_assert(args...)
70#endif
71
72#ifdef DEBUG_YIELD
73#include <sched.h>
74#include <time.h>
75#include <pthread.h>
76#include <unistd.h>
77
78#define YIELD_READ (1 << 0)
79#define YIELD_WRITE (1 << 1)
80
81/* maximum sleep delay, in us */
82#define MAX_SLEEP 50
83
84extern unsigned int yield_active;
85extern unsigned int __thread rand_yield;
86
87static inline void debug_yield_read(void)
88{
89 if (yield_active & YIELD_READ)
90 if (rand_r(&rand_yield) & 0x1)
91 usleep(rand_r(&rand_yield) % MAX_SLEEP);
92}
93
94static inline void debug_yield_write(void)
95{
96 if (yield_active & YIELD_WRITE)
97 if (rand_r(&rand_yield) & 0x1)
98 usleep(rand_r(&rand_yield) % MAX_SLEEP);
99}
100
101static inline void debug_yield_init(void)
102{
103 rand_yield = time(NULL) ^ pthread_self();
104}
105#else
106static inline void debug_yield_read(void)
107{
108}
109
110static inline void debug_yield_write(void)
111{
112}
113
114static inline void debug_yield_init(void)
115{
116
117}
118#endif
119
120static inline void reader_barrier()
121{
122 smp_mb();
123}
124
ac258107 125#define RCU_GP_ONLINE (1UL << 0)
55570466 126#define RCU_GP_CTR (1UL << 1)
ac258107 127
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128/*
129 * Global quiescent period counter with low-order bits unused.
130 * Using a int rather than a char to eliminate false register dependencies
131 * causing stalls on some architectures.
132 */
f0f7dbdd 133extern unsigned long urcu_gp_ctr;
7ac06cef 134
4f8e3380 135struct urcu_reader {
bd1a5e15 136 /* Data used by both reader and synchronize_rcu() */
4f8e3380 137 unsigned long ctr;
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138 /* Data used for registry */
139 struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
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140 pthread_t tid;
141};
142
143extern struct urcu_reader __thread urcu_reader;
7ac06cef 144
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145extern int gp_futex;
146
147/*
148 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
149 */
150static inline void wake_up_gp(void)
151{
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152 if (unlikely(uatomic_read(&gp_futex) == -1)) {
153 uatomic_set(&gp_futex, 0);
0854ccff 154 futex_noasync(&gp_futex, FUTEX_WAKE, 1,
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155 NULL, NULL, 0);
156 }
157}
158
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159#if (BITS_PER_LONG < 64)
160static inline int rcu_gp_ongoing(unsigned long *value)
161{
162 unsigned long reader_gp;
163
164 if (value == NULL)
165 return 0;
166 reader_gp = LOAD_SHARED(*value);
167 return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR);
168}
169#else /* !(BITS_PER_LONG < 64) */
f0f7dbdd 170static inline int rcu_gp_ongoing(unsigned long *value)
7ac06cef 171{
f0f7dbdd 172 unsigned long reader_gp;
4e560c17 173
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174 if (value == NULL)
175 return 0;
4e560c17 176 reader_gp = LOAD_SHARED(*value);
f0f7dbdd 177 return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2);
7ac06cef 178}
47d2f29e 179#endif /* !(BITS_PER_LONG < 64) */
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180
181static inline void _rcu_read_lock(void)
182{
4f8e3380 183 rcu_assert(urcu_reader.ctr);
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184}
185
186static inline void _rcu_read_unlock(void)
187{
188}
189
190static inline void _rcu_quiescent_state(void)
191{
192 smp_mb();
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193 _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr));
194 smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb 195 wake_up_gp();
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196 smp_mb();
197}
198
199static inline void _rcu_thread_offline(void)
200{
201 smp_mb();
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202 STORE_SHARED(urcu_reader.ctr, 0);
203 smp_mb(); /* write urcu_reader.ctr before read futex */
bc6c15bb 204 wake_up_gp();
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205}
206
207static inline void _rcu_thread_online(void)
208{
4f8e3380 209 _STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr));
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210 smp_mb();
211}
212
7ac06cef 213#endif /* _URCU_QSBR_STATIC_H */
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