Cleanup: remove trailing whitespaces at EOL
[urcu.git] / urcu / static / urcu-qsbr.h
CommitLineData
7ac06cef
MD
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 *
a5a9f428
PM
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.
7ac06cef 11 *
6982d6d7 12 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
7ac06cef
MD
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>
f0f7dbdd 34#include <limits.h>
bc6c15bb 35#include <unistd.h>
6d841bc2 36#include <stdint.h>
7ac06cef 37
ec4e58a3
MD
38#include <urcu/compiler.h>
39#include <urcu/arch.h>
7e30abe3 40#include <urcu/system.h>
a2e7bf9c 41#include <urcu/uatomic.h>
4f8e3380 42#include <urcu/list.h>
41849996 43#include <urcu/futex.h>
bd252a04 44#include <urcu/tls-compat.h>
a77f7d82 45#include <urcu/debug.h>
bc6c15bb 46
36bc70a8
MD
47#ifdef __cplusplus
48extern "C" {
67ecffc0 49#endif
36bc70a8 50
7ac06cef
MD
51/*
52 * This code section can only be included in LGPL 2.1 compatible source code.
53 * See below for the function call wrappers which can be used in code meant to
54 * be only linked with the Userspace RCU library. This comes with a small
55 * performance degradation on the read-side due to the added function calls.
56 * This is required to permit relinking with newer versions of the library.
57 */
58
708d89f0
MD
59enum rcu_state {
60 RCU_READER_ACTIVE_CURRENT,
61 RCU_READER_ACTIVE_OLD,
62 RCU_READER_INACTIVE,
63};
64
ac258107 65#define RCU_GP_ONLINE (1UL << 0)
55570466 66#define RCU_GP_CTR (1UL << 1)
ac258107 67
4de0cd31 68struct rcu_gp {
15302e28
LJ
69 /*
70 * Global quiescent period counter with low-order bits unused.
71 * Using a int rather than a char to eliminate false register
72 * dependencies causing stalls on some architectures.
73 */
74 unsigned long ctr;
75
76 int32_t futex;
77} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
78
4de0cd31 79extern struct rcu_gp rcu_gp;
7ac06cef 80
02be5561 81struct rcu_reader {
bd1a5e15 82 /* Data used by both reader and synchronize_rcu() */
4f8e3380 83 unsigned long ctr;
bd1a5e15 84 /* Data used for registry */
16aa9ee8 85 struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
83a2c421 86 int waiting;
4f8e3380 87 pthread_t tid;
a77f7d82
MD
88 /* Reader registered flag, for internal checks. */
89 unsigned int registered:1;
4f8e3380
MD
90};
91
bd252a04 92extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader);
7ac06cef 93
bc6c15bb
MD
94/*
95 * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
96 */
97static inline void wake_up_gp(void)
98{
bd252a04
MD
99 if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader).waiting))) {
100 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).waiting, 0);
83a2c421 101 cmm_smp_mb();
15302e28 102 if (uatomic_read(&rcu_gp.futex) != -1)
83a2c421 103 return;
15302e28 104 uatomic_set(&rcu_gp.futex, 0);
b0a841b4
MD
105 /*
106 * Ignoring return value until we can make this function
107 * return something (because urcu_die() is not publicly
108 * exposed).
109 */
110 (void) futex_noasync(&rcu_gp.futex, FUTEX_WAKE, 1,
111 NULL, NULL, 0);
bc6c15bb
MD
112 }
113}
114
708d89f0 115static inline enum rcu_state rcu_reader_state(unsigned long *ctr)
7ac06cef 116{
e26fa029 117 unsigned long v;
4e560c17 118
6cf3827c 119 v = CMM_LOAD_SHARED(*ctr);
708d89f0
MD
120 if (!v)
121 return RCU_READER_INACTIVE;
15302e28 122 if (v == rcu_gp.ctr)
708d89f0
MD
123 return RCU_READER_ACTIVE_CURRENT;
124 return RCU_READER_ACTIVE_OLD;
7ac06cef
MD
125}
126
a5a9f428
PM
127/*
128 * Enter an RCU read-side critical section.
129 *
130 * This function is less than 10 lines long. The intent is that this
131 * function meets the 10-line criterion for LGPL, allowing this function
132 * to be invoked directly from non-LGPL code.
133 */
7ac06cef
MD
134static inline void _rcu_read_lock(void)
135{
a77f7d82 136 urcu_assert(URCU_TLS(rcu_reader).ctr);
7ac06cef
MD
137}
138
a5a9f428
PM
139/*
140 * Exit an RCU read-side critical section.
141 *
142 * This function is less than 10 lines long. The intent is that this
143 * function meets the 10-line criterion for LGPL, allowing this function
144 * to be invoked directly from non-LGPL code.
145 */
7ac06cef
MD
146static inline void _rcu_read_unlock(void)
147{
a77f7d82 148 urcu_assert(URCU_TLS(rcu_reader).ctr);
7ac06cef
MD
149}
150
882f3357
MD
151/*
152 * Returns whether within a RCU read-side critical section.
153 *
154 * This function is less than 10 lines long. The intent is that this
155 * function meets the 10-line criterion for LGPL, allowing this function
156 * to be invoked directly from non-LGPL code.
157 */
158static inline int _rcu_read_ongoing(void)
159{
160 return URCU_TLS(rcu_reader).ctr;
161}
162
f864c15d
MD
163/*
164 * This is a helper function for _rcu_quiescent_state().
165 * The first cmm_smp_mb() ensures memory accesses in the prior read-side
166 * critical sections are not reordered with store to
167 * URCU_TLS(rcu_reader).ctr, and ensures that mutexes held within an
168 * offline section that would happen to end with this
169 * rcu_quiescent_state() call are not reordered with
170 * store to URCU_TLS(rcu_reader).ctr.
171 */
172static inline void _rcu_quiescent_state_update_and_wakeup(unsigned long gp_ctr)
173{
174 cmm_smp_mb();
175 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, gp_ctr);
176 cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
177 wake_up_gp();
178 cmm_smp_mb();
179}
180
a5a9f428
PM
181/*
182 * Inform RCU of a quiescent state.
183 *
184 * This function is less than 10 lines long. The intent is that this
185 * function meets the 10-line criterion for LGPL, allowing this function
186 * to be invoked directly from non-LGPL code.
f864c15d
MD
187 *
188 * We skip the memory barriers and gp store if our local ctr already
15302e28 189 * matches the global rcu_gp.ctr value: this is OK because a prior
f864c15d
MD
190 * _rcu_quiescent_state() or _rcu_thread_online() already updated it
191 * within our thread, so we have no quiescent state to report.
a5a9f428 192 */
7ac06cef
MD
193static inline void _rcu_quiescent_state(void)
194{
f864c15d
MD
195 unsigned long gp_ctr;
196
a77f7d82 197 urcu_assert(URCU_TLS(rcu_reader).registered);
15302e28 198 if ((gp_ctr = CMM_LOAD_SHARED(rcu_gp.ctr)) == URCU_TLS(rcu_reader).ctr)
f864c15d
MD
199 return;
200 _rcu_quiescent_state_update_and_wakeup(gp_ctr);
7ac06cef
MD
201}
202
a5a9f428
PM
203/*
204 * Take a thread offline, prohibiting it from entering further RCU
205 * read-side critical sections.
206 *
207 * This function is less than 10 lines long. The intent is that this
208 * function meets the 10-line criterion for LGPL, allowing this function
209 * to be invoked directly from non-LGPL code.
210 */
7ac06cef
MD
211static inline void _rcu_thread_offline(void)
212{
a77f7d82 213 urcu_assert(URCU_TLS(rcu_reader).registered);
5481ddb3 214 cmm_smp_mb();
bd252a04
MD
215 CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, 0);
216 cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */
bc6c15bb 217 wake_up_gp();
5481ddb3 218 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
7ac06cef
MD
219}
220
a5a9f428
PM
221/*
222 * Bring a thread online, allowing it to once again enter RCU
223 * read-side critical sections.
224 *
225 * This function is less than 10 lines long. The intent is that this
226 * function meets the 10-line criterion for LGPL, allowing this function
227 * to be invoked directly from non-LGPL code.
228 */
7ac06cef
MD
229static inline void _rcu_thread_online(void)
230{
a77f7d82 231 urcu_assert(URCU_TLS(rcu_reader).registered);
5481ddb3 232 cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */
15302e28 233 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, CMM_LOAD_SHARED(rcu_gp.ctr));
5481ddb3 234 cmm_smp_mb();
7ac06cef
MD
235}
236
67ecffc0 237#ifdef __cplusplus
36bc70a8
MD
238}
239#endif
240
7ac06cef 241#endif /* _URCU_QSBR_STATIC_H */
This page took 0.095118 seconds and 4 git commands to generate.