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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> | |
34 | #include <assert.h> | |
f0f7dbdd | 35 | #include <limits.h> |
bc6c15bb | 36 | #include <unistd.h> |
6d841bc2 | 37 | #include <stdint.h> |
7ac06cef | 38 | |
ec4e58a3 MD |
39 | #include <urcu/compiler.h> |
40 | #include <urcu/arch.h> | |
7e30abe3 | 41 | #include <urcu/system.h> |
a2e7bf9c | 42 | #include <urcu/uatomic.h> |
4f8e3380 | 43 | #include <urcu/list.h> |
41849996 | 44 | #include <urcu/futex.h> |
bd252a04 | 45 | #include <urcu/tls-compat.h> |
bc6c15bb | 46 | |
36bc70a8 MD |
47 | #ifdef __cplusplus |
48 | extern "C" { | |
49 | #endif | |
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 | ||
7ac06cef MD |
59 | #ifdef DEBUG_RCU |
60 | #define rcu_assert(args...) assert(args) | |
61 | #else | |
62 | #define rcu_assert(args...) | |
63 | #endif | |
64 | ||
708d89f0 MD |
65 | enum rcu_state { |
66 | RCU_READER_ACTIVE_CURRENT, | |
67 | RCU_READER_ACTIVE_OLD, | |
68 | RCU_READER_INACTIVE, | |
69 | }; | |
70 | ||
ac258107 | 71 | #define RCU_GP_ONLINE (1UL << 0) |
55570466 | 72 | #define RCU_GP_CTR (1UL << 1) |
ac258107 | 73 | |
4de0cd31 | 74 | struct rcu_gp { |
15302e28 LJ |
75 | /* |
76 | * Global quiescent period counter with low-order bits unused. | |
77 | * Using a int rather than a char to eliminate false register | |
78 | * dependencies causing stalls on some architectures. | |
79 | */ | |
80 | unsigned long ctr; | |
81 | ||
82 | int32_t futex; | |
83 | } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); | |
84 | ||
4de0cd31 | 85 | extern struct rcu_gp rcu_gp; |
7ac06cef | 86 | |
02be5561 | 87 | struct rcu_reader { |
bd1a5e15 | 88 | /* Data used by both reader and synchronize_rcu() */ |
4f8e3380 | 89 | unsigned long ctr; |
bd1a5e15 | 90 | /* Data used for registry */ |
16aa9ee8 | 91 | struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
83a2c421 | 92 | int waiting; |
4f8e3380 MD |
93 | pthread_t tid; |
94 | }; | |
95 | ||
bd252a04 | 96 | extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader); |
7ac06cef | 97 | |
bc6c15bb MD |
98 | /* |
99 | * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. | |
100 | */ | |
101 | static inline void wake_up_gp(void) | |
102 | { | |
bd252a04 MD |
103 | if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader).waiting))) { |
104 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).waiting, 0); | |
83a2c421 | 105 | cmm_smp_mb(); |
15302e28 | 106 | if (uatomic_read(&rcu_gp.futex) != -1) |
83a2c421 | 107 | return; |
15302e28 | 108 | uatomic_set(&rcu_gp.futex, 0); |
52c67a3d MD |
109 | /* |
110 | * Ignoring return value until we can make this function | |
111 | * return something (because urcu_die() is not publicly | |
112 | * exposed). | |
113 | */ | |
114 | (void) futex_noasync(&rcu_gp.futex, FUTEX_WAKE, 1, | |
115 | NULL, NULL, 0); | |
bc6c15bb MD |
116 | } |
117 | } | |
118 | ||
708d89f0 | 119 | static inline enum rcu_state rcu_reader_state(unsigned long *ctr) |
7ac06cef | 120 | { |
e26fa029 | 121 | unsigned long v; |
4e560c17 | 122 | |
6cf3827c | 123 | v = CMM_LOAD_SHARED(*ctr); |
708d89f0 MD |
124 | if (!v) |
125 | return RCU_READER_INACTIVE; | |
15302e28 | 126 | if (v == rcu_gp.ctr) |
708d89f0 MD |
127 | return RCU_READER_ACTIVE_CURRENT; |
128 | return RCU_READER_ACTIVE_OLD; | |
7ac06cef MD |
129 | } |
130 | ||
a5a9f428 PM |
131 | /* |
132 | * Enter an RCU read-side critical section. | |
133 | * | |
134 | * This function is less than 10 lines long. The intent is that this | |
135 | * function meets the 10-line criterion for LGPL, allowing this function | |
136 | * to be invoked directly from non-LGPL code. | |
137 | */ | |
7ac06cef MD |
138 | static inline void _rcu_read_lock(void) |
139 | { | |
bd252a04 | 140 | rcu_assert(URCU_TLS(rcu_reader).ctr); |
7ac06cef MD |
141 | } |
142 | ||
a5a9f428 PM |
143 | /* |
144 | * Exit an RCU read-side critical section. | |
145 | * | |
146 | * This function is less than 10 lines long. The intent is that this | |
147 | * function meets the 10-line criterion for LGPL, allowing this function | |
148 | * to be invoked directly from non-LGPL code. | |
149 | */ | |
7ac06cef MD |
150 | static inline void _rcu_read_unlock(void) |
151 | { | |
152 | } | |
153 | ||
882f3357 MD |
154 | /* |
155 | * Returns whether within a RCU read-side critical section. | |
156 | * | |
157 | * This function is less than 10 lines long. The intent is that this | |
158 | * function meets the 10-line criterion for LGPL, allowing this function | |
159 | * to be invoked directly from non-LGPL code. | |
160 | */ | |
161 | static inline int _rcu_read_ongoing(void) | |
162 | { | |
163 | return URCU_TLS(rcu_reader).ctr; | |
164 | } | |
165 | ||
f864c15d MD |
166 | /* |
167 | * This is a helper function for _rcu_quiescent_state(). | |
168 | * The first cmm_smp_mb() ensures memory accesses in the prior read-side | |
169 | * critical sections are not reordered with store to | |
170 | * URCU_TLS(rcu_reader).ctr, and ensures that mutexes held within an | |
171 | * offline section that would happen to end with this | |
172 | * rcu_quiescent_state() call are not reordered with | |
173 | * store to URCU_TLS(rcu_reader).ctr. | |
174 | */ | |
175 | static inline void _rcu_quiescent_state_update_and_wakeup(unsigned long gp_ctr) | |
176 | { | |
177 | cmm_smp_mb(); | |
178 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, gp_ctr); | |
179 | cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */ | |
180 | wake_up_gp(); | |
181 | cmm_smp_mb(); | |
182 | } | |
183 | ||
a5a9f428 PM |
184 | /* |
185 | * Inform RCU of a quiescent state. | |
186 | * | |
187 | * This function is less than 10 lines long. The intent is that this | |
188 | * function meets the 10-line criterion for LGPL, allowing this function | |
189 | * to be invoked directly from non-LGPL code. | |
f864c15d MD |
190 | * |
191 | * We skip the memory barriers and gp store if our local ctr already | |
15302e28 | 192 | * matches the global rcu_gp.ctr value: this is OK because a prior |
f864c15d MD |
193 | * _rcu_quiescent_state() or _rcu_thread_online() already updated it |
194 | * within our thread, so we have no quiescent state to report. | |
a5a9f428 | 195 | */ |
7ac06cef MD |
196 | static inline void _rcu_quiescent_state(void) |
197 | { | |
f864c15d MD |
198 | unsigned long gp_ctr; |
199 | ||
15302e28 | 200 | if ((gp_ctr = CMM_LOAD_SHARED(rcu_gp.ctr)) == URCU_TLS(rcu_reader).ctr) |
f864c15d MD |
201 | return; |
202 | _rcu_quiescent_state_update_and_wakeup(gp_ctr); | |
7ac06cef MD |
203 | } |
204 | ||
a5a9f428 PM |
205 | /* |
206 | * Take a thread offline, prohibiting it from entering further RCU | |
207 | * read-side critical sections. | |
208 | * | |
209 | * This function is less than 10 lines long. The intent is that this | |
210 | * function meets the 10-line criterion for LGPL, allowing this function | |
211 | * to be invoked directly from non-LGPL code. | |
212 | */ | |
7ac06cef MD |
213 | static inline void _rcu_thread_offline(void) |
214 | { | |
5481ddb3 | 215 | cmm_smp_mb(); |
bd252a04 MD |
216 | CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, 0); |
217 | cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */ | |
bc6c15bb | 218 | wake_up_gp(); |
5481ddb3 | 219 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
7ac06cef MD |
220 | } |
221 | ||
a5a9f428 PM |
222 | /* |
223 | * Bring a thread online, allowing it to once again enter RCU | |
224 | * read-side critical sections. | |
225 | * | |
226 | * This function is less than 10 lines long. The intent is that this | |
227 | * function meets the 10-line criterion for LGPL, allowing this function | |
228 | * to be invoked directly from non-LGPL code. | |
229 | */ | |
7ac06cef MD |
230 | static inline void _rcu_thread_online(void) |
231 | { | |
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 | ||
36bc70a8 MD |
237 | #ifdef __cplusplus |
238 | } | |
239 | #endif | |
240 | ||
7ac06cef | 241 | #endif /* _URCU_QSBR_STATIC_H */ |