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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 | * | |
9 | * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-qsbr.h for linking | |
10 | * dynamically with the userspace rcu QSBR library. | |
11 | * | |
12 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> | |
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 MD |
36 | #include <syscall.h> |
37 | #include <unistd.h> | |
7ac06cef | 38 | |
ec4e58a3 MD |
39 | #include <urcu/compiler.h> |
40 | #include <urcu/arch.h> | |
7e30abe3 | 41 | #include <urcu/system.h> |
48d848c7 | 42 | #include <urcu/uatomic_arch.h> |
4f8e3380 | 43 | #include <urcu/list.h> |
0854ccff | 44 | #include <urcu/urcu-futex.h> |
bc6c15bb | 45 | |
7ac06cef MD |
46 | /* |
47 | * This code section can only be included in LGPL 2.1 compatible source code. | |
48 | * See below for the function call wrappers which can be used in code meant to | |
49 | * be only linked with the Userspace RCU library. This comes with a small | |
50 | * performance degradation on the read-side due to the added function calls. | |
51 | * This is required to permit relinking with newer versions of the library. | |
52 | */ | |
53 | ||
54 | /* | |
55 | * If a reader is really non-cooperative and refuses to commit its | |
4f8e3380 | 56 | * urcu_reader.ctr count to memory (there is no barrier in the reader |
7ac06cef MD |
57 | * per-se), kick it after a few loops waiting for it. |
58 | */ | |
59 | #define KICK_READER_LOOPS 10000 | |
60 | ||
bc6c15bb MD |
61 | /* |
62 | * Active attempts to check for reader Q.S. before calling futex(). | |
63 | */ | |
64 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
65 | ||
7ac06cef MD |
66 | #ifdef DEBUG_RCU |
67 | #define rcu_assert(args...) assert(args) | |
68 | #else | |
69 | #define rcu_assert(args...) | |
70 | #endif | |
71 | ||
72 | #ifdef DEBUG_YIELD | |
73 | #include <sched.h> | |
74 | #include <time.h> | |
75 | #include <pthread.h> | |
76 | #include <unistd.h> | |
77 | ||
78 | #define YIELD_READ (1 << 0) | |
79 | #define YIELD_WRITE (1 << 1) | |
80 | ||
81 | /* maximum sleep delay, in us */ | |
82 | #define MAX_SLEEP 50 | |
83 | ||
84 | extern unsigned int yield_active; | |
85 | extern unsigned int __thread rand_yield; | |
86 | ||
87 | static inline void debug_yield_read(void) | |
88 | { | |
89 | if (yield_active & YIELD_READ) | |
90 | if (rand_r(&rand_yield) & 0x1) | |
91 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
92 | } | |
93 | ||
94 | static inline void debug_yield_write(void) | |
95 | { | |
96 | if (yield_active & YIELD_WRITE) | |
97 | if (rand_r(&rand_yield) & 0x1) | |
98 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
99 | } | |
100 | ||
101 | static inline void debug_yield_init(void) | |
102 | { | |
103 | rand_yield = time(NULL) ^ pthread_self(); | |
104 | } | |
105 | #else | |
106 | static inline void debug_yield_read(void) | |
107 | { | |
108 | } | |
109 | ||
110 | static inline void debug_yield_write(void) | |
111 | { | |
112 | } | |
113 | ||
114 | static inline void debug_yield_init(void) | |
115 | { | |
116 | ||
117 | } | |
118 | #endif | |
119 | ||
120 | static inline void reader_barrier() | |
121 | { | |
122 | smp_mb(); | |
123 | } | |
124 | ||
ac258107 | 125 | #define RCU_GP_ONLINE (1UL << 0) |
55570466 | 126 | #define RCU_GP_CTR (1UL << 1) |
ac258107 | 127 | |
7ac06cef MD |
128 | /* |
129 | * Global quiescent period counter with low-order bits unused. | |
130 | * Using a int rather than a char to eliminate false register dependencies | |
131 | * causing stalls on some architectures. | |
132 | */ | |
f0f7dbdd | 133 | extern unsigned long urcu_gp_ctr; |
7ac06cef | 134 | |
4f8e3380 | 135 | struct urcu_reader { |
bd1a5e15 | 136 | /* Data used by both reader and synchronize_rcu() */ |
4f8e3380 | 137 | unsigned long ctr; |
bd1a5e15 MD |
138 | /* Data used for registry */ |
139 | struct list_head head __attribute__((aligned(CACHE_LINE_SIZE))); | |
4f8e3380 MD |
140 | pthread_t tid; |
141 | }; | |
142 | ||
143 | extern struct urcu_reader __thread urcu_reader; | |
7ac06cef | 144 | |
bc6c15bb MD |
145 | extern int gp_futex; |
146 | ||
147 | /* | |
148 | * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. | |
149 | */ | |
150 | static inline void wake_up_gp(void) | |
151 | { | |
ec4e58a3 MD |
152 | if (unlikely(uatomic_read(&gp_futex) == -1)) { |
153 | uatomic_set(&gp_futex, 0); | |
0854ccff | 154 | futex_noasync(&gp_futex, FUTEX_WAKE, 1, |
bc6c15bb MD |
155 | NULL, NULL, 0); |
156 | } | |
157 | } | |
158 | ||
47d2f29e MD |
159 | #if (BITS_PER_LONG < 64) |
160 | static inline int rcu_gp_ongoing(unsigned long *value) | |
161 | { | |
162 | unsigned long reader_gp; | |
163 | ||
164 | if (value == NULL) | |
165 | return 0; | |
166 | reader_gp = LOAD_SHARED(*value); | |
167 | return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR); | |
168 | } | |
169 | #else /* !(BITS_PER_LONG < 64) */ | |
f0f7dbdd | 170 | static inline int rcu_gp_ongoing(unsigned long *value) |
7ac06cef | 171 | { |
f0f7dbdd | 172 | unsigned long reader_gp; |
4e560c17 | 173 | |
7ac06cef MD |
174 | if (value == NULL) |
175 | return 0; | |
4e560c17 | 176 | reader_gp = LOAD_SHARED(*value); |
f0f7dbdd | 177 | return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2); |
7ac06cef | 178 | } |
47d2f29e | 179 | #endif /* !(BITS_PER_LONG < 64) */ |
7ac06cef MD |
180 | |
181 | static inline void _rcu_read_lock(void) | |
182 | { | |
4f8e3380 | 183 | rcu_assert(urcu_reader.ctr); |
7ac06cef MD |
184 | } |
185 | ||
186 | static inline void _rcu_read_unlock(void) | |
187 | { | |
188 | } | |
189 | ||
190 | static inline void _rcu_quiescent_state(void) | |
191 | { | |
192 | smp_mb(); | |
4f8e3380 MD |
193 | _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr)); |
194 | smp_mb(); /* write urcu_reader.ctr before read futex */ | |
bc6c15bb | 195 | wake_up_gp(); |
7ac06cef MD |
196 | smp_mb(); |
197 | } | |
198 | ||
199 | static inline void _rcu_thread_offline(void) | |
200 | { | |
201 | smp_mb(); | |
4f8e3380 MD |
202 | STORE_SHARED(urcu_reader.ctr, 0); |
203 | smp_mb(); /* write urcu_reader.ctr before read futex */ | |
bc6c15bb | 204 | wake_up_gp(); |
7ac06cef MD |
205 | } |
206 | ||
207 | static inline void _rcu_thread_online(void) | |
208 | { | |
4f8e3380 | 209 | _STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr)); |
7ac06cef MD |
210 | smp_mb(); |
211 | } | |
212 | ||
7ac06cef | 213 | #endif /* _URCU_QSBR_STATIC_H */ |