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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 | ||
65 | #ifdef DEBUG_YIELD | |
66 | #include <sched.h> | |
67 | #include <time.h> | |
68 | #include <pthread.h> | |
69 | #include <unistd.h> | |
70 | ||
1de4df4b MD |
71 | #define RCU_YIELD_READ (1 << 0) |
72 | #define RCU_YIELD_WRITE (1 << 1) | |
7ac06cef MD |
73 | |
74 | /* maximum sleep delay, in us */ | |
75 | #define MAX_SLEEP 50 | |
76 | ||
1de4df4b MD |
77 | extern unsigned int rcu_yield_active; |
78 | extern DECLARE_URCU_TLS(unsigned int, rcu_rand_yield); | |
7ac06cef | 79 | |
1de4df4b | 80 | static inline void rcu_debug_yield_read(void) |
7ac06cef | 81 | { |
1de4df4b MD |
82 | if (rcu_yield_active & RCU_YIELD_READ) |
83 | if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1) | |
84 | usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP); | |
7ac06cef MD |
85 | } |
86 | ||
1de4df4b | 87 | static inline void rcu_debug_yield_write(void) |
7ac06cef | 88 | { |
1de4df4b MD |
89 | if (rcu_yield_active & RCU_YIELD_WRITE) |
90 | if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1) | |
91 | usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP); | |
7ac06cef MD |
92 | } |
93 | ||
1de4df4b | 94 | static inline void rcu_debug_yield_init(void) |
7ac06cef | 95 | { |
6ff854ac | 96 | URCU_TLS(rcu_rand_yield) = time(NULL) ^ (unsigned long) pthread_self(); |
7ac06cef MD |
97 | } |
98 | #else | |
1de4df4b | 99 | static inline void rcu_debug_yield_read(void) |
7ac06cef MD |
100 | { |
101 | } | |
102 | ||
1de4df4b | 103 | static inline void rcu_debug_yield_write(void) |
7ac06cef MD |
104 | { |
105 | } | |
106 | ||
1de4df4b | 107 | static inline void rcu_debug_yield_init(void) |
7ac06cef MD |
108 | { |
109 | ||
110 | } | |
111 | #endif | |
112 | ||
ac258107 | 113 | #define RCU_GP_ONLINE (1UL << 0) |
55570466 | 114 | #define RCU_GP_CTR (1UL << 1) |
ac258107 | 115 | |
7ac06cef MD |
116 | /* |
117 | * Global quiescent period counter with low-order bits unused. | |
118 | * Using a int rather than a char to eliminate false register dependencies | |
119 | * causing stalls on some architectures. | |
120 | */ | |
02be5561 | 121 | extern unsigned long rcu_gp_ctr; |
7ac06cef | 122 | |
02be5561 | 123 | struct rcu_reader { |
bd1a5e15 | 124 | /* Data used by both reader and synchronize_rcu() */ |
4f8e3380 | 125 | unsigned long ctr; |
bd1a5e15 | 126 | /* Data used for registry */ |
16aa9ee8 | 127 | struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
83a2c421 | 128 | int waiting; |
4f8e3380 MD |
129 | pthread_t tid; |
130 | }; | |
131 | ||
bd252a04 | 132 | extern DECLARE_URCU_TLS(struct rcu_reader, rcu_reader); |
7ac06cef | 133 | |
1de4df4b | 134 | extern int32_t rcu_gp_futex; |
bc6c15bb MD |
135 | |
136 | /* | |
137 | * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. | |
138 | */ | |
139 | static inline void wake_up_gp(void) | |
140 | { | |
bd252a04 MD |
141 | if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(rcu_reader).waiting))) { |
142 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).waiting, 0); | |
83a2c421 | 143 | cmm_smp_mb(); |
1de4df4b | 144 | if (uatomic_read(&rcu_gp_futex) != -1) |
83a2c421 | 145 | return; |
1de4df4b MD |
146 | uatomic_set(&rcu_gp_futex, 0); |
147 | futex_noasync(&rcu_gp_futex, FUTEX_WAKE, 1, | |
bc6c15bb MD |
148 | NULL, NULL, 0); |
149 | } | |
150 | } | |
151 | ||
e26fa029 | 152 | static inline int rcu_gp_ongoing(unsigned long *ctr) |
7ac06cef | 153 | { |
e26fa029 | 154 | unsigned long v; |
4e560c17 | 155 | |
6cf3827c | 156 | v = CMM_LOAD_SHARED(*ctr); |
92cb20a8 | 157 | return v && (v != rcu_gp_ctr); |
7ac06cef MD |
158 | } |
159 | ||
a5a9f428 PM |
160 | /* |
161 | * Enter an RCU read-side critical section. | |
162 | * | |
163 | * This function is less than 10 lines long. The intent is that this | |
164 | * function meets the 10-line criterion for LGPL, allowing this function | |
165 | * to be invoked directly from non-LGPL code. | |
166 | */ | |
7ac06cef MD |
167 | static inline void _rcu_read_lock(void) |
168 | { | |
bd252a04 | 169 | rcu_assert(URCU_TLS(rcu_reader).ctr); |
7ac06cef MD |
170 | } |
171 | ||
a5a9f428 PM |
172 | /* |
173 | * Exit an RCU read-side critical section. | |
174 | * | |
175 | * This function is less than 10 lines long. The intent is that this | |
176 | * function meets the 10-line criterion for LGPL, allowing this function | |
177 | * to be invoked directly from non-LGPL code. | |
178 | */ | |
7ac06cef MD |
179 | static inline void _rcu_read_unlock(void) |
180 | { | |
181 | } | |
182 | ||
f864c15d MD |
183 | /* |
184 | * This is a helper function for _rcu_quiescent_state(). | |
185 | * The first cmm_smp_mb() ensures memory accesses in the prior read-side | |
186 | * critical sections are not reordered with store to | |
187 | * URCU_TLS(rcu_reader).ctr, and ensures that mutexes held within an | |
188 | * offline section that would happen to end with this | |
189 | * rcu_quiescent_state() call are not reordered with | |
190 | * store to URCU_TLS(rcu_reader).ctr. | |
191 | */ | |
192 | static inline void _rcu_quiescent_state_update_and_wakeup(unsigned long gp_ctr) | |
193 | { | |
194 | cmm_smp_mb(); | |
195 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, gp_ctr); | |
196 | cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */ | |
197 | wake_up_gp(); | |
198 | cmm_smp_mb(); | |
199 | } | |
200 | ||
a5a9f428 PM |
201 | /* |
202 | * Inform RCU of a quiescent state. | |
203 | * | |
204 | * This function is less than 10 lines long. The intent is that this | |
205 | * function meets the 10-line criterion for LGPL, allowing this function | |
206 | * to be invoked directly from non-LGPL code. | |
f864c15d MD |
207 | * |
208 | * We skip the memory barriers and gp store if our local ctr already | |
209 | * matches the global rcu_gp_ctr value: this is OK because a prior | |
210 | * _rcu_quiescent_state() or _rcu_thread_online() already updated it | |
211 | * within our thread, so we have no quiescent state to report. | |
a5a9f428 | 212 | */ |
7ac06cef MD |
213 | static inline void _rcu_quiescent_state(void) |
214 | { | |
f864c15d MD |
215 | unsigned long gp_ctr; |
216 | ||
217 | if ((gp_ctr = CMM_LOAD_SHARED(rcu_gp_ctr)) == URCU_TLS(rcu_reader).ctr) | |
218 | return; | |
219 | _rcu_quiescent_state_update_and_wakeup(gp_ctr); | |
7ac06cef MD |
220 | } |
221 | ||
a5a9f428 PM |
222 | /* |
223 | * Take a thread offline, prohibiting it from entering further 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_offline(void) |
231 | { | |
5481ddb3 | 232 | cmm_smp_mb(); |
bd252a04 MD |
233 | CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, 0); |
234 | cmm_smp_mb(); /* write URCU_TLS(rcu_reader).ctr before read futex */ | |
bc6c15bb | 235 | wake_up_gp(); |
5481ddb3 | 236 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
7ac06cef MD |
237 | } |
238 | ||
a5a9f428 PM |
239 | /* |
240 | * Bring a thread online, allowing it to once again enter RCU | |
241 | * read-side critical sections. | |
242 | * | |
243 | * This function is less than 10 lines long. The intent is that this | |
244 | * function meets the 10-line criterion for LGPL, allowing this function | |
245 | * to be invoked directly from non-LGPL code. | |
246 | */ | |
7ac06cef MD |
247 | static inline void _rcu_thread_online(void) |
248 | { | |
5481ddb3 | 249 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
bd252a04 | 250 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).ctr, CMM_LOAD_SHARED(rcu_gp_ctr)); |
5481ddb3 | 251 | cmm_smp_mb(); |
7ac06cef MD |
252 | } |
253 | ||
36bc70a8 MD |
254 | #ifdef __cplusplus |
255 | } | |
256 | #endif | |
257 | ||
7ac06cef | 258 | #endif /* _URCU_QSBR_STATIC_H */ |