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d3d3857f MJ |
1 | // SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
2 | // SPDX-FileCopyrightText: 2009 Paul E. McKenney, IBM Corporation. | |
3 | // | |
4 | // SPDX-License-Identifier: LGPL-2.1-or-later | |
5 | ||
7ac06cef MD |
6 | #ifndef _URCU_QSBR_STATIC_H |
7 | #define _URCU_QSBR_STATIC_H | |
8 | ||
9 | /* | |
7ac06cef MD |
10 | * Userspace RCU QSBR header. |
11 | * | |
a5a9f428 PM |
12 | * TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU |
13 | * RELEASE. See urcu.h for linking dynamically with the userspace rcu library. | |
7ac06cef | 14 | * |
7ac06cef MD |
15 | * IBM's contributions to this file may be relicensed under LGPLv2 or later. |
16 | */ | |
17 | ||
18 | #include <stdlib.h> | |
19 | #include <pthread.h> | |
f0f7dbdd | 20 | #include <limits.h> |
bc6c15bb | 21 | #include <unistd.h> |
6d841bc2 | 22 | #include <stdint.h> |
7ac06cef | 23 | |
601922a8 | 24 | #include <urcu/annotate.h> |
01477510 | 25 | #include <urcu/debug.h> |
ec4e58a3 MD |
26 | #include <urcu/compiler.h> |
27 | #include <urcu/arch.h> | |
7e30abe3 | 28 | #include <urcu/system.h> |
a2e7bf9c | 29 | #include <urcu/uatomic.h> |
4f8e3380 | 30 | #include <urcu/list.h> |
41849996 | 31 | #include <urcu/futex.h> |
bd252a04 | 32 | #include <urcu/tls-compat.h> |
4477a870 | 33 | #include <urcu/static/urcu-common.h> |
bc6c15bb | 34 | |
36bc70a8 MD |
35 | #ifdef __cplusplus |
36 | extern "C" { | |
67ecffc0 | 37 | #endif |
36bc70a8 | 38 | |
7ac06cef MD |
39 | /* |
40 | * This code section can only be included in LGPL 2.1 compatible source code. | |
41 | * See below for the function call wrappers which can be used in code meant to | |
42 | * be only linked with the Userspace RCU library. This comes with a small | |
43 | * performance degradation on the read-side due to the added function calls. | |
44 | * This is required to permit relinking with newer versions of the library. | |
45 | */ | |
46 | ||
4477a870 MD |
47 | #define URCU_QSBR_GP_ONLINE (1UL << 0) |
48 | #define URCU_QSBR_GP_CTR (1UL << 1) | |
15302e28 | 49 | |
4477a870 | 50 | extern struct urcu_gp urcu_qsbr_gp; |
7ac06cef | 51 | |
4477a870 | 52 | struct urcu_qsbr_reader { |
bd1a5e15 | 53 | /* Data used by both reader and synchronize_rcu() */ |
4f8e3380 | 54 | unsigned long ctr; |
bd1a5e15 | 55 | /* Data used for registry */ |
16aa9ee8 | 56 | struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
83a2c421 | 57 | int waiting; |
4f8e3380 | 58 | pthread_t tid; |
a77f7d82 MD |
59 | /* Reader registered flag, for internal checks. */ |
60 | unsigned int registered:1; | |
4f8e3380 MD |
61 | }; |
62 | ||
4477a870 | 63 | extern DECLARE_URCU_TLS(struct urcu_qsbr_reader, urcu_qsbr_reader); |
7ac06cef | 64 | |
bc6c15bb MD |
65 | /* |
66 | * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. | |
67 | */ | |
4477a870 | 68 | static inline void urcu_qsbr_wake_up_gp(void) |
bc6c15bb | 69 | { |
4477a870 MD |
70 | if (caa_unlikely(_CMM_LOAD_SHARED(URCU_TLS(urcu_qsbr_reader).waiting))) { |
71 | _CMM_STORE_SHARED(URCU_TLS(urcu_qsbr_reader).waiting, 0); | |
83a2c421 | 72 | cmm_smp_mb(); |
4477a870 | 73 | if (uatomic_read(&urcu_qsbr_gp.futex) != -1) |
83a2c421 | 74 | return; |
4477a870 | 75 | uatomic_set(&urcu_qsbr_gp.futex, 0); |
b0a841b4 MD |
76 | /* |
77 | * Ignoring return value until we can make this function | |
78 | * return something (because urcu_die() is not publicly | |
79 | * exposed). | |
80 | */ | |
4477a870 | 81 | (void) futex_noasync(&urcu_qsbr_gp.futex, FUTEX_WAKE, 1, |
b0a841b4 | 82 | NULL, NULL, 0); |
bc6c15bb MD |
83 | } |
84 | } | |
85 | ||
601922a8 OD |
86 | static inline enum urcu_state urcu_qsbr_reader_state(unsigned long *ctr, |
87 | cmm_annotate_t *group) | |
7ac06cef | 88 | { |
e26fa029 | 89 | unsigned long v; |
4e560c17 | 90 | |
601922a8 OD |
91 | v = uatomic_load(ctr, CMM_RELAXED); |
92 | cmm_annotate_group_mem_acquire(group, ctr); | |
93 | ||
708d89f0 | 94 | if (!v) |
4477a870 MD |
95 | return URCU_READER_INACTIVE; |
96 | if (v == urcu_qsbr_gp.ctr) | |
97 | return URCU_READER_ACTIVE_CURRENT; | |
98 | return URCU_READER_ACTIVE_OLD; | |
7ac06cef MD |
99 | } |
100 | ||
a5a9f428 PM |
101 | /* |
102 | * Enter an RCU read-side critical section. | |
103 | * | |
104 | * This function is less than 10 lines long. The intent is that this | |
105 | * function meets the 10-line criterion for LGPL, allowing this function | |
106 | * to be invoked directly from non-LGPL code. | |
107 | */ | |
4477a870 | 108 | static inline void _urcu_qsbr_read_lock(void) |
7ac06cef | 109 | { |
2a27e931 | 110 | urcu_assert_debug(URCU_TLS(urcu_qsbr_reader).ctr); |
7ac06cef MD |
111 | } |
112 | ||
a5a9f428 PM |
113 | /* |
114 | * Exit an RCU read-side critical section. | |
115 | * | |
116 | * This function is less than 10 lines long. The intent is that this | |
117 | * function meets the 10-line criterion for LGPL, allowing this function | |
118 | * to be invoked directly from non-LGPL code. | |
119 | */ | |
4477a870 | 120 | static inline void _urcu_qsbr_read_unlock(void) |
7ac06cef | 121 | { |
2a27e931 | 122 | urcu_assert_debug(URCU_TLS(urcu_qsbr_reader).ctr); |
7ac06cef MD |
123 | } |
124 | ||
882f3357 MD |
125 | /* |
126 | * Returns whether within a RCU read-side critical section. | |
127 | * | |
128 | * This function is less than 10 lines long. The intent is that this | |
129 | * function meets the 10-line criterion for LGPL, allowing this function | |
130 | * to be invoked directly from non-LGPL code. | |
131 | */ | |
4477a870 | 132 | static inline int _urcu_qsbr_read_ongoing(void) |
882f3357 | 133 | { |
4477a870 | 134 | return URCU_TLS(urcu_qsbr_reader).ctr; |
882f3357 MD |
135 | } |
136 | ||
f864c15d MD |
137 | /* |
138 | * This is a helper function for _rcu_quiescent_state(). | |
139 | * The first cmm_smp_mb() ensures memory accesses in the prior read-side | |
140 | * critical sections are not reordered with store to | |
4477a870 | 141 | * URCU_TLS(urcu_qsbr_reader).ctr, and ensures that mutexes held within an |
f864c15d | 142 | * offline section that would happen to end with this |
4477a870 MD |
143 | * urcu_qsbr_quiescent_state() call are not reordered with |
144 | * store to URCU_TLS(urcu_qsbr_reader).ctr. | |
f864c15d | 145 | */ |
4477a870 | 146 | static inline void _urcu_qsbr_quiescent_state_update_and_wakeup(unsigned long gp_ctr) |
f864c15d | 147 | { |
601922a8 OD |
148 | uatomic_store(&URCU_TLS(urcu_qsbr_reader).ctr, gp_ctr, CMM_SEQ_CST); |
149 | ||
150 | /* write URCU_TLS(urcu_qsbr_reader).ctr before read futex */ | |
4477a870 | 151 | urcu_qsbr_wake_up_gp(); |
f864c15d MD |
152 | cmm_smp_mb(); |
153 | } | |
154 | ||
a5a9f428 PM |
155 | /* |
156 | * Inform RCU of a quiescent state. | |
157 | * | |
158 | * This function is less than 10 lines long. The intent is that this | |
159 | * function meets the 10-line criterion for LGPL, allowing this function | |
160 | * to be invoked directly from non-LGPL code. | |
f864c15d MD |
161 | * |
162 | * We skip the memory barriers and gp store if our local ctr already | |
4477a870 | 163 | * matches the global urcu_qsbr_gp.ctr value: this is OK because a prior |
f864c15d MD |
164 | * _rcu_quiescent_state() or _rcu_thread_online() already updated it |
165 | * within our thread, so we have no quiescent state to report. | |
a5a9f428 | 166 | */ |
4477a870 | 167 | static inline void _urcu_qsbr_quiescent_state(void) |
7ac06cef | 168 | { |
f864c15d MD |
169 | unsigned long gp_ctr; |
170 | ||
2a27e931 | 171 | urcu_assert_debug(URCU_TLS(urcu_qsbr_reader).registered); |
601922a8 OD |
172 | gp_ctr = uatomic_load(&urcu_qsbr_gp.ctr, CMM_RELAXED); |
173 | if (gp_ctr == URCU_TLS(urcu_qsbr_reader).ctr) | |
f864c15d | 174 | return; |
4477a870 | 175 | _urcu_qsbr_quiescent_state_update_and_wakeup(gp_ctr); |
7ac06cef MD |
176 | } |
177 | ||
a5a9f428 PM |
178 | /* |
179 | * Take a thread offline, prohibiting it from entering further RCU | |
180 | * read-side critical sections. | |
181 | * | |
182 | * This function is less than 10 lines long. The intent is that this | |
183 | * function meets the 10-line criterion for LGPL, allowing this function | |
184 | * to be invoked directly from non-LGPL code. | |
185 | */ | |
4477a870 | 186 | static inline void _urcu_qsbr_thread_offline(void) |
7ac06cef | 187 | { |
2a27e931 | 188 | urcu_assert_debug(URCU_TLS(urcu_qsbr_reader).registered); |
601922a8 OD |
189 | uatomic_store(&URCU_TLS(urcu_qsbr_reader).ctr, 0, CMM_SEQ_CST); |
190 | /* write URCU_TLS(urcu_qsbr_reader).ctr before read futex */ | |
4477a870 | 191 | urcu_qsbr_wake_up_gp(); |
5481ddb3 | 192 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
7ac06cef MD |
193 | } |
194 | ||
a5a9f428 PM |
195 | /* |
196 | * Bring a thread online, allowing it to once again enter RCU | |
197 | * read-side critical sections. | |
198 | * | |
199 | * This function is less than 10 lines long. The intent is that this | |
200 | * function meets the 10-line criterion for LGPL, allowing this function | |
201 | * to be invoked directly from non-LGPL code. | |
202 | */ | |
4477a870 | 203 | static inline void _urcu_qsbr_thread_online(void) |
7ac06cef | 204 | { |
601922a8 OD |
205 | unsigned long *pctr = &URCU_TLS(urcu_qsbr_reader).ctr; |
206 | unsigned long ctr; | |
207 | ||
2a27e931 | 208 | urcu_assert_debug(URCU_TLS(urcu_qsbr_reader).registered); |
5481ddb3 | 209 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
601922a8 OD |
210 | ctr = uatomic_load(&urcu_qsbr_gp.ctr, CMM_RELAXED); |
211 | cmm_annotate_mem_acquire(&urcu_qsbr_gp.ctr); | |
212 | uatomic_store(pctr, ctr, CMM_RELAXED); | |
5481ddb3 | 213 | cmm_smp_mb(); |
7ac06cef MD |
214 | } |
215 | ||
67ecffc0 | 216 | #ifdef __cplusplus |
36bc70a8 MD |
217 | } |
218 | #endif | |
219 | ||
7ac06cef | 220 | #endif /* _URCU_QSBR_STATIC_H */ |