Cleanup: urcu: remove unused membarrier "group" parameter
[urcu.git] / 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>
e1c0b55c 44#include <urcu/rand-compat.h>
a77f7d82 45#include <urcu/debug.h>
bc6c15bb 46
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47#ifdef __cplusplus
48extern "C" {
49#endif
50
65f1e634 51/* Default is RCU_MEMBARRIER */
fdf01eed 52#if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
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53#define RCU_MEMBARRIER
54#endif
55
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56/*
57 * This code section can only be included in LGPL 2.1 compatible source code.
58 * See below for the function call wrappers which can be used in code meant to
59 * be only linked with the Userspace RCU library. This comes with a small
60 * performance degradation on the read-side due to the added function calls.
61 * This is required to permit relinking with newer versions of the library.
62 */
63
64/*
65 * The signal number used by the RCU library can be overridden with
02be5561 66 * -DSIGRCU= when compiling the library.
ddf7eefb 67 * Provide backward compatibility for liburcu 0.3.x SIGURCU.
adcfce54 68 */
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69#ifdef SIGURCU
70#define SIGRCU SIGURCU
71#endif
72
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73#ifndef SIGRCU
74#define SIGRCU SIGUSR1
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75#endif
76
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77enum rcu_state {
78 RCU_READER_ACTIVE_CURRENT,
79 RCU_READER_ACTIVE_OLD,
80 RCU_READER_INACTIVE,
81};
82
25cc6d18 83/*
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84 * Slave barriers are only guaranteed to be ordered wrt master barriers.
85 *
86 * The pair ordering is detailed as (O: ordered, X: not ordered) :
87 * slave master
88 * slave X O
89 * master O O
90 */
91
fdf01eed 92#ifdef RCU_MEMBARRIER
1de4df4b 93extern int rcu_has_sys_membarrier;
fdf01eed 94
a4922ed9 95static inline void smp_mb_slave(void)
fdf01eed 96{
1de4df4b 97 if (caa_likely(rcu_has_sys_membarrier))
5481ddb3 98 cmm_barrier();
fdf01eed 99 else
5481ddb3 100 cmm_smp_mb();
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101}
102#endif
103
02be5561 104#ifdef RCU_MB
a4922ed9 105static inline void smp_mb_slave(void)
adcfce54 106{
5481ddb3 107 cmm_smp_mb();
adcfce54 108}
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109#endif
110
111#ifdef RCU_SIGNAL
a4922ed9 112static inline void smp_mb_slave(void)
adcfce54 113{
5481ddb3 114 cmm_barrier();
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115}
116#endif
117
118/*
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119 * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
120 * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
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121 */
122#define RCU_GP_COUNT (1UL << 0)
123/* Use the amount of bits equal to half of the architecture long size */
27d65bc5 124#define RCU_GP_CTR_PHASE (1UL << (sizeof(unsigned long) << 2))
02be5561 125#define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1)
adcfce54 126
4de0cd31 127struct rcu_gp {
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128 /*
129 * Global grace period counter.
130 * Contains the current RCU_GP_CTR_PHASE.
131 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
132 * Written to only by writer with mutex taken.
133 * Read by both writer and readers.
134 */
135 unsigned long ctr;
136
137 int32_t futex;
138} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
139
4de0cd31 140extern struct rcu_gp rcu_gp;
adcfce54 141
02be5561 142struct rcu_reader {
bd1a5e15 143 /* Data used by both reader and synchronize_rcu() */
27d65bc5 144 unsigned long ctr;
e3b0cef0 145 char need_mb;
bd1a5e15 146 /* Data used for registry */
16aa9ee8 147 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
bd1a5e15 148 pthread_t tid;
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149 /* Reader registered flag, for internal checks. */
150 unsigned int registered:1;
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151};
152
bd252a04 153extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
adcfce54 154
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155/*
156 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
157 */
158static inline void wake_up_gp(void)
159{
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160 if (caa_unlikely(uatomic_read(&rcu_gp.futex) == -1)) {
161 uatomic_set(&rcu_gp.futex, 0);
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162 /*
163 * Ignoring return value until we can make this function
164 * return something (because urcu_die() is not publicly
165 * exposed).
166 */
167 (void) futex_async(&rcu_gp.futex, FUTEX_WAKE, 1,
168 NULL, NULL, 0);
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169 }
170}
171
fd189fa5 172static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
adcfce54 173{
27d65bc5 174 unsigned long v;
adcfce54 175
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176 /*
177 * Make sure both tests below are done on the same version of *value
178 * to insure consistency.
179 */
6cf3827c 180 v = CMM_LOAD_SHARED(*ctr);
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181 if (!(v & RCU_GP_CTR_NEST_MASK))
182 return RCU_READER_INACTIVE;
ed1b099e 183 if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE))
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184 return RCU_READER_ACTIVE_CURRENT;
185 return RCU_READER_ACTIVE_OLD;
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186}
187
a5a9f428 188/*
ed1b099e 189 * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as
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190 * the per-thread rcu_reader.ctr) has the upper bits containing a count of
191 * _rcu_read_lock() nesting, and a lower-order bit that contains either zero
192 * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in
193 * _rcu_read_lock() happen before the subsequent read-side critical section.
194 */
195static inline void _rcu_read_lock_update(unsigned long tmp)
adcfce54 196{
a0b7f7ea 197 if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
ed1b099e 198 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, _CMM_LOAD_SHARED(rcu_gp.ctr));
a4922ed9 199 smp_mb_slave();
a5a9f428 200 } else
bd252a04 201 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp + RCU_GP_COUNT);
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202}
203
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204/*
205 * Enter an RCU read-side critical section.
206 *
207 * The first cmm_barrier() call ensures that the compiler does not reorder
208 * the body of _rcu_read_lock() with a mutex.
209 *
210 * This function and its helper are both less than 10 lines long. The
211 * intent is that this function meets the 10-line criterion in LGPL,
212 * allowing this function to be invoked directly from non-LGPL code.
213 */
214static inline void _rcu_read_lock(void)
adcfce54 215{
27d65bc5 216 unsigned long tmp;
bc6c15bb 217
a77f7d82 218 urcu_assert(URCU_TLS(rcu_reader).registered);
a5a9f428 219 cmm_barrier();
bd252a04 220 tmp = URCU_TLS(rcu_reader).ctr;
6ef5ddc9 221 urcu_assert((tmp & RCU_GP_CTR_NEST_MASK) != RCU_GP_CTR_NEST_MASK);
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222 _rcu_read_lock_update(tmp);
223}
224
225/*
226 * This is a helper function for _rcu_read_unlock().
227 *
228 * The first smp_mb_slave() call ensures that the critical section is
229 * seen to precede the store to rcu_reader.ctr.
230 * The second smp_mb_slave() call ensures that we write to rcu_reader.ctr
231 * before reading the update-side futex.
232 */
233static inline void _rcu_read_unlock_update_and_wakeup(unsigned long tmp)
234{
a0b7f7ea 235 if (caa_likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
a4922ed9 236 smp_mb_slave();
343c8b13 237 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
a4922ed9 238 smp_mb_slave();
bc6c15bb 239 wake_up_gp();
a5a9f428 240 } else
343c8b13 241 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, tmp - RCU_GP_COUNT);
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242}
243
244/*
245 * Exit an RCU read-side crtical section. Both this function and its
246 * helper are smaller than 10 lines of code, and are intended to be
247 * usable by non-LGPL code, as called out in LGPL.
248 */
249static inline void _rcu_read_unlock(void)
250{
251 unsigned long tmp;
252
a77f7d82 253 urcu_assert(URCU_TLS(rcu_reader).registered);
a5a9f428 254 tmp = URCU_TLS(rcu_reader).ctr;
343c8b13 255 urcu_assert(tmp & RCU_GP_CTR_NEST_MASK);
a5a9f428 256 _rcu_read_unlock_update_and_wakeup(tmp);
5481ddb3 257 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
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258}
259
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260/*
261 * Returns whether within a RCU read-side critical section.
262 *
263 * This function is less than 10 lines long. The intent is that this
264 * function meets the 10-line criterion for LGPL, allowing this function
265 * to be invoked directly from non-LGPL code.
266 */
267static inline int _rcu_read_ongoing(void)
268{
269 return URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK;
270}
271
ad918eeb 272#ifdef __cplusplus
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273}
274#endif
275
adcfce54 276#endif /* _URCU_STATIC_H */
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