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adcfce54 MD |
1 | #ifndef _URCU_STATIC_H |
2 | #define _URCU_STATIC_H | |
3 | ||
4 | /* | |
5 | * urcu-static.h | |
6 | * | |
d2d23035 | 7 | * Userspace RCU header. |
adcfce54 | 8 | * |
d2d23035 MD |
9 | * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking |
10 | * dynamically with the userspace rcu library. | |
adcfce54 | 11 | * |
d2d23035 MD |
12 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> |
13 | * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. | |
adcfce54 | 14 | * |
d2d23035 MD |
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 | |
adcfce54 MD |
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> | |
bc6c15bb MD |
34 | #include <syscall.h> |
35 | #include <unistd.h> | |
adcfce54 | 36 | |
ec4e58a3 MD |
37 | #include <urcu/compiler.h> |
38 | #include <urcu/arch.h> | |
7e30abe3 | 39 | #include <urcu/system.h> |
48d848c7 | 40 | #include <urcu/uatomic_arch.h> |
e3b0cef0 | 41 | #include <urcu/list.h> |
0854ccff | 42 | #include <urcu/urcu-futex.h> |
bc6c15bb | 43 | |
adcfce54 MD |
44 | /* |
45 | * This code section can only be included in LGPL 2.1 compatible source code. | |
46 | * See below for the function call wrappers which can be used in code meant to | |
47 | * be only linked with the Userspace RCU library. This comes with a small | |
48 | * performance degradation on the read-side due to the added function calls. | |
49 | * This is required to permit relinking with newer versions of the library. | |
50 | */ | |
51 | ||
52 | /* | |
53 | * The signal number used by the RCU library can be overridden with | |
54 | * -DSIGURCU= when compiling the library. | |
55 | */ | |
56 | #ifndef SIGURCU | |
57 | #define SIGURCU SIGUSR1 | |
58 | #endif | |
59 | ||
60 | /* | |
61 | * If a reader is really non-cooperative and refuses to commit its | |
62 | * urcu_active_readers count to memory (there is no barrier in the reader | |
63 | * per-se), kick it after a few loops waiting for it. | |
64 | */ | |
65 | #define KICK_READER_LOOPS 10000 | |
66 | ||
bc6c15bb MD |
67 | /* |
68 | * Active attempts to check for reader Q.S. before calling futex(). | |
69 | */ | |
70 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
71 | ||
7ac06cef MD |
72 | #ifdef DEBUG_RCU |
73 | #define rcu_assert(args...) assert(args) | |
74 | #else | |
75 | #define rcu_assert(args...) | |
76 | #endif | |
77 | ||
adcfce54 MD |
78 | #ifdef DEBUG_YIELD |
79 | #include <sched.h> | |
80 | #include <time.h> | |
81 | #include <pthread.h> | |
82 | #include <unistd.h> | |
83 | ||
84 | #define YIELD_READ (1 << 0) | |
85 | #define YIELD_WRITE (1 << 1) | |
86 | ||
b4ce1526 | 87 | /* |
0a1d290b | 88 | * Updates without URCU_MB are much slower. Account this in |
b4ce1526 MD |
89 | * the delay. |
90 | */ | |
0a1d290b | 91 | #ifdef URCU_MB |
adcfce54 MD |
92 | /* maximum sleep delay, in us */ |
93 | #define MAX_SLEEP 50 | |
94 | #else | |
95 | #define MAX_SLEEP 30000 | |
96 | #endif | |
97 | ||
98 | extern unsigned int yield_active; | |
99 | extern unsigned int __thread rand_yield; | |
100 | ||
101 | static inline void debug_yield_read(void) | |
102 | { | |
103 | if (yield_active & YIELD_READ) | |
104 | if (rand_r(&rand_yield) & 0x1) | |
105 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
106 | } | |
107 | ||
108 | static inline void debug_yield_write(void) | |
109 | { | |
110 | if (yield_active & YIELD_WRITE) | |
111 | if (rand_r(&rand_yield) & 0x1) | |
112 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
113 | } | |
114 | ||
115 | static inline void debug_yield_init(void) | |
116 | { | |
117 | rand_yield = time(NULL) ^ pthread_self(); | |
118 | } | |
119 | #else | |
120 | static inline void debug_yield_read(void) | |
121 | { | |
122 | } | |
123 | ||
124 | static inline void debug_yield_write(void) | |
125 | { | |
126 | } | |
127 | ||
128 | static inline void debug_yield_init(void) | |
129 | { | |
130 | ||
131 | } | |
132 | #endif | |
133 | ||
0a1d290b | 134 | #ifdef URCU_MB |
adcfce54 MD |
135 | static inline void reader_barrier() |
136 | { | |
137 | smp_mb(); | |
138 | } | |
139 | #else | |
140 | static inline void reader_barrier() | |
141 | { | |
142 | barrier(); | |
143 | } | |
144 | #endif | |
145 | ||
146 | /* | |
147 | * The trick here is that RCU_GP_CTR_BIT must be a multiple of 8 so we can use a | |
148 | * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits. | |
149 | */ | |
150 | #define RCU_GP_COUNT (1UL << 0) | |
151 | /* Use the amount of bits equal to half of the architecture long size */ | |
152 | #define RCU_GP_CTR_BIT (1UL << (sizeof(long) << 2)) | |
153 | #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_BIT - 1) | |
154 | ||
155 | /* | |
156 | * Global quiescent period counter with low-order bits unused. | |
157 | * Using a int rather than a char to eliminate false register dependencies | |
158 | * causing stalls on some architectures. | |
159 | */ | |
160 | extern long urcu_gp_ctr; | |
161 | ||
e3b0cef0 | 162 | struct urcu_reader { |
bd1a5e15 | 163 | /* Data used by both reader and synchronize_rcu() */ |
e3b0cef0 | 164 | long ctr; |
e3b0cef0 | 165 | char need_mb; |
bd1a5e15 MD |
166 | /* Data used for registry */ |
167 | struct list_head head __attribute__((aligned(CACHE_LINE_SIZE))); | |
168 | pthread_t tid; | |
e3b0cef0 MD |
169 | }; |
170 | ||
171 | extern struct urcu_reader __thread urcu_reader; | |
adcfce54 | 172 | |
bc6c15bb MD |
173 | extern int gp_futex; |
174 | ||
175 | /* | |
176 | * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. | |
177 | */ | |
178 | static inline void wake_up_gp(void) | |
179 | { | |
ec4e58a3 MD |
180 | if (unlikely(uatomic_read(&gp_futex) == -1)) { |
181 | uatomic_set(&gp_futex, 0); | |
0854ccff | 182 | futex_async(&gp_futex, FUTEX_WAKE, 1, |
bc6c15bb MD |
183 | NULL, NULL, 0); |
184 | } | |
185 | } | |
186 | ||
adcfce54 MD |
187 | static inline int rcu_old_gp_ongoing(long *value) |
188 | { | |
189 | long v; | |
190 | ||
191 | if (value == NULL) | |
192 | return 0; | |
193 | /* | |
194 | * Make sure both tests below are done on the same version of *value | |
195 | * to insure consistency. | |
196 | */ | |
197 | v = LOAD_SHARED(*value); | |
198 | return (v & RCU_GP_CTR_NEST_MASK) && | |
199 | ((v ^ urcu_gp_ctr) & RCU_GP_CTR_BIT); | |
200 | } | |
201 | ||
202 | static inline void _rcu_read_lock(void) | |
203 | { | |
204 | long tmp; | |
205 | ||
e3b0cef0 | 206 | tmp = urcu_reader.ctr; |
adcfce54 | 207 | /* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */ |
67ef1a2c | 208 | if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) { |
e3b0cef0 | 209 | _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr)); |
67ef1a2c MD |
210 | /* |
211 | * Set active readers count for outermost nesting level before | |
212 | * accessing the pointer. See force_mb_all_threads(). | |
213 | */ | |
214 | reader_barrier(); | |
215 | } else { | |
e3b0cef0 | 216 | _STORE_SHARED(urcu_reader.ctr, tmp + RCU_GP_COUNT); |
67ef1a2c | 217 | } |
adcfce54 MD |
218 | } |
219 | ||
220 | static inline void _rcu_read_unlock(void) | |
221 | { | |
bc6c15bb MD |
222 | long tmp; |
223 | ||
e3b0cef0 | 224 | tmp = urcu_reader.ctr; |
adcfce54 MD |
225 | /* |
226 | * Finish using rcu before decrementing the pointer. | |
227 | * See force_mb_all_threads(). | |
228 | */ | |
bc6c15bb MD |
229 | if (likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) { |
230 | reader_barrier(); | |
e3b0cef0 MD |
231 | _STORE_SHARED(urcu_reader.ctr, urcu_reader.ctr - RCU_GP_COUNT); |
232 | /* write urcu_reader.ctr before read futex */ | |
bc6c15bb MD |
233 | reader_barrier(); |
234 | wake_up_gp(); | |
235 | } else { | |
e3b0cef0 | 236 | _STORE_SHARED(urcu_reader.ctr, urcu_reader.ctr - RCU_GP_COUNT); |
bc6c15bb | 237 | } |
adcfce54 MD |
238 | } |
239 | ||
adcfce54 | 240 | #endif /* _URCU_STATIC_H */ |