Update support for MEMBARRIER_QUERY
[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/* Default is RCU_MEMBARRIER */
49#if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
50#define RCU_MEMBARRIER
51#endif
52
53#ifdef RCU_MEMBARRIER
54#include <unistd.h>
55#include <sys/syscall.h>
56
57/* If the headers do not support SYS_membarrier, statically use RCU_MB */
58#ifdef SYS_membarrier
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59# define MEMBARRIER_EXPEDITED (1 << 0)
60# define MEMBARRIER_DELAYED (1 << 1)
61# define MEMBARRIER_QUERY (1 << 16)
f0708810 62# define membarrier(...) syscall(__NR_membarrier, __VA_ARGS__)
fdf01eed 63#else
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64# undef RCU_MEMBARRIER
65# define RCU_MB
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66#endif
67#endif
68
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69/*
70 * This code section can only be included in LGPL 2.1 compatible source code.
71 * See below for the function call wrappers which can be used in code meant to
72 * be only linked with the Userspace RCU library. This comes with a small
73 * performance degradation on the read-side due to the added function calls.
74 * This is required to permit relinking with newer versions of the library.
75 */
76
77/*
78 * The signal number used by the RCU library can be overridden with
02be5561 79 * -DSIGRCU= when compiling the library.
adcfce54 80 */
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81#ifndef SIGRCU
82#define SIGRCU SIGUSR1
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83#endif
84
85/*
86 * If a reader is really non-cooperative and refuses to commit its
02be5561 87 * rcu_active_readers count to memory (there is no barrier in the reader
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88 * per-se), kick it after a few loops waiting for it.
89 */
90#define KICK_READER_LOOPS 10000
91
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92/*
93 * Active attempts to check for reader Q.S. before calling futex().
94 */
95#define RCU_QS_ACTIVE_ATTEMPTS 100
96
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97#ifdef DEBUG_RCU
98#define rcu_assert(args...) assert(args)
99#else
100#define rcu_assert(args...)
101#endif
102
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103#ifdef DEBUG_YIELD
104#include <sched.h>
105#include <time.h>
106#include <pthread.h>
107#include <unistd.h>
108
109#define YIELD_READ (1 << 0)
110#define YIELD_WRITE (1 << 1)
111
b4ce1526 112/*
fdf01eed 113 * Updates with RCU_SIGNAL are much slower. Account this in the delay.
b4ce1526 114 */
fdf01eed 115#ifdef RCU_SIGNAL
adcfce54 116/* maximum sleep delay, in us */
adcfce54 117#define MAX_SLEEP 30000
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118#else
119#define MAX_SLEEP 50
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120#endif
121
122extern unsigned int yield_active;
123extern unsigned int __thread rand_yield;
124
125static inline void debug_yield_read(void)
126{
127 if (yield_active & YIELD_READ)
128 if (rand_r(&rand_yield) & 0x1)
129 usleep(rand_r(&rand_yield) % MAX_SLEEP);
130}
131
132static inline void debug_yield_write(void)
133{
134 if (yield_active & YIELD_WRITE)
135 if (rand_r(&rand_yield) & 0x1)
136 usleep(rand_r(&rand_yield) % MAX_SLEEP);
137}
138
139static inline void debug_yield_init(void)
140{
141 rand_yield = time(NULL) ^ pthread_self();
142}
143#else
144static inline void debug_yield_read(void)
145{
146}
147
148static inline void debug_yield_write(void)
149{
150}
151
152static inline void debug_yield_init(void)
153{
154
155}
156#endif
157
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158#ifdef RCU_MEMBARRIER
159extern int has_sys_membarrier;
160
161static inline void smp_mb_light()
162{
163 if (likely(has_sys_membarrier))
164 barrier();
165 else
166 smp_mb();
167}
168#endif
169
02be5561 170#ifdef RCU_MB
9d7e3f89 171static inline void smp_mb_light()
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172{
173 smp_mb();
174}
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175#endif
176
177#ifdef RCU_SIGNAL
9d7e3f89 178static inline void smp_mb_light()
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179{
180 barrier();
181}
182#endif
183
184/*
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185 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
186 * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
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187 */
188#define RCU_GP_COUNT (1UL << 0)
189/* Use the amount of bits equal to half of the architecture long size */
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190#define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2))
191#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
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192
193/*
194 * Global quiescent period counter with low-order bits unused.
195 * Using a int rather than a char to eliminate false register dependencies
196 * causing stalls on some architectures.
197 */
02be5561 198extern long rcu_gp_ctr;
adcfce54 199
02be5561 200struct rcu_reader {
bd1a5e15 201 /* Data used by both reader and synchronize_rcu() */
e3b0cef0 202 long ctr;
e3b0cef0 203 char need_mb;
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204 /* Data used for registry */
205 struct list_head head __attribute__((aligned(CACHE_LINE_SIZE)));
206 pthread_t tid;
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207};
208
02be5561 209extern struct rcu_reader __thread rcu_reader;
adcfce54 210
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211extern int gp_futex;
212
213/*
214 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
215 */
216static inline void wake_up_gp(void)
217{
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218 if (unlikely(uatomic_read(&gp_futex) == -1)) {
219 uatomic_set(&gp_futex, 0);
0854ccff 220 futex_async(&gp_futex, FUTEX_WAKE, 1,
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221 NULL, NULL, 0);
222 }
223}
224
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225static inline int rcu_old_gp_ongoing(long *value)
226{
227 long v;
228
229 if (value == NULL)
230 return 0;
231 /*
232 * Make sure both tests below are done on the same version of *value
233 * to insure consistency.
234 */
235 v = LOAD_SHARED(*value);
236 return (v & RCU_GP_CTR_NEST_MASK) &&
02be5561 237 ((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE);
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238}
239
240static inline void _rcu_read_lock(void)
241{
242 long tmp;
243
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244 tmp = rcu_reader.ctr;
245 /*
246 * rcu_gp_ctr is
247 * RCU_GP_COUNT | (~RCU_GP_CTR_PHASE or RCU_GP_CTR_PHASE)
248 */
67ef1a2c 249 if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
02be5561 250 _STORE_SHARED(rcu_reader.ctr, _LOAD_SHARED(rcu_gp_ctr));
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251 /*
252 * Set active readers count for outermost nesting level before
9d7e3f89 253 * accessing the pointer. See smp_mb_heavy().
67ef1a2c 254 */
9d7e3f89 255 smp_mb_light();
67ef1a2c 256 } else {
02be5561 257 _STORE_SHARED(rcu_reader.ctr, tmp + RCU_GP_COUNT);
67ef1a2c 258 }
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259}
260
261static inline void _rcu_read_unlock(void)
262{
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263 long tmp;
264
02be5561 265 tmp = rcu_reader.ctr;
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266 /*
267 * Finish using rcu before decrementing the pointer.
9d7e3f89 268 * See smp_mb_heavy().
adcfce54 269 */
bc6c15bb 270 if (likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
9d7e3f89 271 smp_mb_light();
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272 _STORE_SHARED(rcu_reader.ctr, rcu_reader.ctr - RCU_GP_COUNT);
273 /* write rcu_reader.ctr before read futex */
9d7e3f89 274 smp_mb_light();
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275 wake_up_gp();
276 } else {
02be5561 277 _STORE_SHARED(rcu_reader.ctr, rcu_reader.ctr - RCU_GP_COUNT);
bc6c15bb 278 }
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279}
280
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281#ifdef __cplusplus
282}
283#endif
284
adcfce54 285#endif /* _URCU_STATIC_H */
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