Fix: Move rand-compat to private src dir
[urcu.git] / include / urcu / static / urcu.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 CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
10 * RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
adcfce54 11 *
6982d6d7 12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
d2d23035 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>
bc6c15bb 34#include <unistd.h>
6d841bc2 35#include <stdint.h>
adcfce54 36
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37#include <urcu/compiler.h>
38#include <urcu/arch.h>
7e30abe3 39#include <urcu/system.h>
a2e7bf9c 40#include <urcu/uatomic.h>
e3b0cef0 41#include <urcu/list.h>
41849996 42#include <urcu/futex.h>
bd252a04 43#include <urcu/tls-compat.h>
a77f7d82 44#include <urcu/debug.h>
bc6c15bb 45
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46#ifdef __cplusplus
47extern "C" {
67ecffc0 48#endif
36bc70a8 49
65f1e634 50/* Default is RCU_MEMBARRIER */
fdf01eed 51#if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
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52#define RCU_MEMBARRIER
53#endif
54
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55/*
56 * This code section can only be included in LGPL 2.1 compatible source code.
57 * See below for the function call wrappers which can be used in code meant to
58 * be only linked with the Userspace RCU library. This comes with a small
59 * performance degradation on the read-side due to the added function calls.
60 * This is required to permit relinking with newer versions of the library.
61 */
62
63/*
64 * The signal number used by the RCU library can be overridden with
02be5561 65 * -DSIGRCU= when compiling the library.
ddf7eefb 66 * Provide backward compatibility for liburcu 0.3.x SIGURCU.
adcfce54 67 */
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68#ifdef SIGURCU
69#define SIGRCU SIGURCU
70#endif
71
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72#ifndef SIGRCU
73#define SIGRCU SIGUSR1
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74#endif
75
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76enum rcu_state {
77 RCU_READER_ACTIVE_CURRENT,
78 RCU_READER_ACTIVE_OLD,
79 RCU_READER_INACTIVE,
80};
81
25cc6d18 82/*
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83 * Slave barriers are only guaranteed to be ordered wrt master barriers.
84 *
85 * The pair ordering is detailed as (O: ordered, X: not ordered) :
86 * slave master
87 * slave X O
88 * master O O
89 */
90
fdf01eed 91#ifdef RCU_MEMBARRIER
1de4df4b 92extern int rcu_has_sys_membarrier;
fdf01eed 93
a4922ed9 94static inline void smp_mb_slave(void)
fdf01eed 95{
1de4df4b 96 if (caa_likely(rcu_has_sys_membarrier))
5481ddb3 97 cmm_barrier();
fdf01eed 98 else
5481ddb3 99 cmm_smp_mb();
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100}
101#endif
102
02be5561 103#ifdef RCU_MB
a4922ed9 104static inline void smp_mb_slave(void)
adcfce54 105{
5481ddb3 106 cmm_smp_mb();
adcfce54 107}
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108#endif
109
110#ifdef RCU_SIGNAL
a4922ed9 111static inline void smp_mb_slave(void)
adcfce54 112{
5481ddb3 113 cmm_barrier();
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114}
115#endif
116
117/*
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118 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
119 * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
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120 */
121#define RCU_GP_COUNT (1UL << 0)
122/* Use the amount of bits equal to half of the architecture long size */
27d65bc5 123#define RCU_GP_CTR_PHASE (1UL << (sizeof(unsigned long) << 2))
02be5561 124#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
adcfce54 125
4de0cd31 126struct rcu_gp {
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127 /*
128 * Global grace period counter.
129 * Contains the current RCU_GP_CTR_PHASE.
130 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
131 * Written to only by writer with mutex taken.
132 * Read by both writer and readers.
133 */
134 unsigned long ctr;
135
136 int32_t futex;
137} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
138
4de0cd31 139extern struct rcu_gp rcu_gp;
adcfce54 140
02be5561 141struct rcu_reader {
bd1a5e15 142 /* Data used by both reader and synchronize_rcu() */
27d65bc5 143 unsigned long ctr;
e3b0cef0 144 char need_mb;
bd1a5e15 145 /* Data used for registry */
16aa9ee8 146 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
bd1a5e15 147 pthread_t tid;
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148 /* Reader registered flag, for internal checks. */
149 unsigned int registered:1;
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150};
151
bd252a04 152extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
adcfce54 153
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154/*
155 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
156 */
157static inline void wake_up_gp(void)
158{
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159 if (caa_unlikely(uatomic_read(&rcu_gp.futex) == -1)) {
160 uatomic_set(&rcu_gp.futex, 0);
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161 /*
162 * Ignoring return value until we can make this function
163 * return something (because urcu_die() is not publicly
164 * exposed).
165 */
166 (void) futex_async(&rcu_gp.futex, FUTEX_WAKE, 1,
167 NULL, NULL, 0);
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168 }
169}
170
fd189fa5 171static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
adcfce54 172{
27d65bc5 173 unsigned long v;
adcfce54 174
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175 /*
176 * Make sure both tests below are done on the same version of *value
177 * to insure consistency.
178 */
6cf3827c 179 v = CMM_LOAD_SHARED(*ctr);
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180 if (!(v & RCU_GP_CTR_NEST_MASK))
181 return RCU_READER_INACTIVE;
ed1b099e 182 if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE))
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183 return RCU_READER_ACTIVE_CURRENT;
184 return RCU_READER_ACTIVE_OLD;
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185}
186
a5a9f428 187/*
ed1b099e 188 * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as
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189 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
190 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
191 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
192 * _rcu_read_lock() happen before the subsequent read-side critical section.
193 */
194static inline void _rcu_read_lock_update(unsigned long tmp)
adcfce54 195{
a0b7f7ea 196 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
ed1b099e 197 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp.ctr));
a4922ed9 198 smp_mb_slave();
a5a9f428 199 } else
bd252a04 200 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp + RCU_GP_COUNT);
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201}
202
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203/*
204 * Enter an RCU read-side critical section.
205 *
206 * The first cmm_barrier() call ensures that the compiler does not reorder
207 * the body of _rcu_read_lock() with a mutex.
208 *
209 * This function and its helper are both less than 10 lines long. The
210 * intent is that this function meets the 10-line criterion in LGPL,
211 * allowing this function to be invoked directly from non-LGPL code.
212 */
213static inline void _rcu_read_lock(void)
adcfce54 214{
27d65bc5 215 unsigned long tmp;
bc6c15bb 216
a77f7d82 217 urcu_assert(URCU_TLS(rcu_reader).registered);
a5a9f428 218 cmm_barrier();
bd252a04 219 tmp = URCU_TLS(rcu_reader).ctr;
6ef5ddc9 220 urcu_assert((tmp & RCU_GP_CTR_NEST_MASK) != RCU_GP_CTR_NEST_MASK);
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221 _rcu_read_lock_update(tmp);
222}
223
224/*
225 * This is a helper function for _rcu_read_unlock().
226 *
227 * The first smp_mb_slave() call ensures that the critical section is
228 * seen to precede the store to rcu_reader.ctr.
229 * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
230 * before reading the update-side futex.
231 */
232static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
233{
a0b7f7ea 234 if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
a4922ed9 235 smp_mb_slave();
343c8b13 236 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
a4922ed9 237 smp_mb_slave();
bc6c15bb 238 wake_up_gp();
a5a9f428 239 } else
343c8b13 240 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
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241}
242
243/*
244 * Exit an RCU read-side crtical section. Both this function and its
245 * helper are smaller than 10 lines of code, and are intended to be
246 * usable by non-LGPL code, as called out in LGPL.
247 */
248static inline void _rcu_read_unlock(void)
249{
250 unsigned long tmp;
251
a77f7d82 252 urcu_assert(URCU_TLS(rcu_reader).registered);
a5a9f428 253 tmp = URCU_TLS(rcu_reader).ctr;
343c8b13 254 urcu_assert(tmp & RCU_GP_CTR_NEST_MASK);
a5a9f428 255 _rcu_read_unlock_update_and_wakeup(tmp);
5481ddb3 256 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
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257}
258
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259/*
260 * Returns whether within a RCU read-side critical section.
261 *
262 * This function is less than 10 lines long. The intent is that this
263 * function meets the 10-line criterion for LGPL, allowing this function
264 * to be invoked directly from non-LGPL code.
265 */
266static inline int _rcu_read_ongoing(void)
267{
268 return URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK;
269}
270
ad918eeb 271#ifdef __cplusplus
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272}
273#endif
274
adcfce54 275#endif /* _URCU_STATIC_H */
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