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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> |
7ac06cef | 44 | |
bc6c15bb MD |
45 | #define futex(...) syscall(__NR_futex, __VA_ARGS__) |
46 | #define FUTEX_WAIT 0 | |
47 | #define FUTEX_WAKE 1 | |
48 | ||
7ac06cef MD |
49 | /* |
50 | * This code section can only be included in LGPL 2.1 compatible source code. | |
51 | * See below for the function call wrappers which can be used in code meant to | |
52 | * be only linked with the Userspace RCU library. This comes with a small | |
53 | * performance degradation on the read-side due to the added function calls. | |
54 | * This is required to permit relinking with newer versions of the library. | |
55 | */ | |
56 | ||
57 | /* | |
58 | * If a reader is really non-cooperative and refuses to commit its | |
4f8e3380 | 59 | * urcu_reader.ctr count to memory (there is no barrier in the reader |
7ac06cef MD |
60 | * per-se), kick it after a few loops waiting for it. |
61 | */ | |
62 | #define KICK_READER_LOOPS 10000 | |
63 | ||
bc6c15bb MD |
64 | /* |
65 | * Active attempts to check for reader Q.S. before calling futex(). | |
66 | */ | |
67 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
68 | ||
7ac06cef MD |
69 | #ifdef DEBUG_RCU |
70 | #define rcu_assert(args...) assert(args) | |
71 | #else | |
72 | #define rcu_assert(args...) | |
73 | #endif | |
74 | ||
75 | #ifdef DEBUG_YIELD | |
76 | #include <sched.h> | |
77 | #include <time.h> | |
78 | #include <pthread.h> | |
79 | #include <unistd.h> | |
80 | ||
81 | #define YIELD_READ (1 << 0) | |
82 | #define YIELD_WRITE (1 << 1) | |
83 | ||
84 | /* maximum sleep delay, in us */ | |
85 | #define MAX_SLEEP 50 | |
86 | ||
87 | extern unsigned int yield_active; | |
88 | extern unsigned int __thread rand_yield; | |
89 | ||
90 | static inline void debug_yield_read(void) | |
91 | { | |
92 | if (yield_active & YIELD_READ) | |
93 | if (rand_r(&rand_yield) & 0x1) | |
94 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
95 | } | |
96 | ||
97 | static inline void debug_yield_write(void) | |
98 | { | |
99 | if (yield_active & YIELD_WRITE) | |
100 | if (rand_r(&rand_yield) & 0x1) | |
101 | usleep(rand_r(&rand_yield) % MAX_SLEEP); | |
102 | } | |
103 | ||
104 | static inline void debug_yield_init(void) | |
105 | { | |
106 | rand_yield = time(NULL) ^ pthread_self(); | |
107 | } | |
108 | #else | |
109 | static inline void debug_yield_read(void) | |
110 | { | |
111 | } | |
112 | ||
113 | static inline void debug_yield_write(void) | |
114 | { | |
115 | } | |
116 | ||
117 | static inline void debug_yield_init(void) | |
118 | { | |
119 | ||
120 | } | |
121 | #endif | |
122 | ||
123 | static inline void reader_barrier() | |
124 | { | |
125 | smp_mb(); | |
126 | } | |
127 | ||
ac258107 | 128 | #define RCU_GP_ONLINE (1UL << 0) |
55570466 | 129 | #define RCU_GP_CTR (1UL << 1) |
ac258107 | 130 | |
7ac06cef MD |
131 | /* |
132 | * Global quiescent period counter with low-order bits unused. | |
133 | * Using a int rather than a char to eliminate false register dependencies | |
134 | * causing stalls on some architectures. | |
135 | */ | |
f0f7dbdd | 136 | extern unsigned long urcu_gp_ctr; |
7ac06cef | 137 | |
4f8e3380 | 138 | struct urcu_reader { |
bd1a5e15 | 139 | /* Data used by both reader and synchronize_rcu() */ |
4f8e3380 | 140 | unsigned long ctr; |
bd1a5e15 MD |
141 | /* Data used for registry */ |
142 | struct list_head head __attribute__((aligned(CACHE_LINE_SIZE))); | |
4f8e3380 MD |
143 | pthread_t tid; |
144 | }; | |
145 | ||
146 | extern struct urcu_reader __thread urcu_reader; | |
7ac06cef | 147 | |
bc6c15bb MD |
148 | extern int gp_futex; |
149 | ||
150 | /* | |
151 | * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. | |
152 | */ | |
153 | static inline void wake_up_gp(void) | |
154 | { | |
ec4e58a3 MD |
155 | if (unlikely(uatomic_read(&gp_futex) == -1)) { |
156 | uatomic_set(&gp_futex, 0); | |
bc6c15bb MD |
157 | futex(&gp_futex, FUTEX_WAKE, 1, |
158 | NULL, NULL, 0); | |
159 | } | |
160 | } | |
161 | ||
47d2f29e MD |
162 | #if (BITS_PER_LONG < 64) |
163 | static inline int rcu_gp_ongoing(unsigned long *value) | |
164 | { | |
165 | unsigned long reader_gp; | |
166 | ||
167 | if (value == NULL) | |
168 | return 0; | |
169 | reader_gp = LOAD_SHARED(*value); | |
170 | return reader_gp && ((reader_gp ^ urcu_gp_ctr) & RCU_GP_CTR); | |
171 | } | |
172 | #else /* !(BITS_PER_LONG < 64) */ | |
f0f7dbdd | 173 | static inline int rcu_gp_ongoing(unsigned long *value) |
7ac06cef | 174 | { |
f0f7dbdd | 175 | unsigned long reader_gp; |
4e560c17 | 176 | |
7ac06cef MD |
177 | if (value == NULL) |
178 | return 0; | |
4e560c17 | 179 | reader_gp = LOAD_SHARED(*value); |
f0f7dbdd | 180 | return reader_gp && (reader_gp - urcu_gp_ctr > ULONG_MAX / 2); |
7ac06cef | 181 | } |
47d2f29e | 182 | #endif /* !(BITS_PER_LONG < 64) */ |
7ac06cef MD |
183 | |
184 | static inline void _rcu_read_lock(void) | |
185 | { | |
4f8e3380 | 186 | rcu_assert(urcu_reader.ctr); |
7ac06cef MD |
187 | } |
188 | ||
189 | static inline void _rcu_read_unlock(void) | |
190 | { | |
191 | } | |
192 | ||
193 | static inline void _rcu_quiescent_state(void) | |
194 | { | |
195 | smp_mb(); | |
4f8e3380 MD |
196 | _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr)); |
197 | smp_mb(); /* write urcu_reader.ctr before read futex */ | |
bc6c15bb | 198 | wake_up_gp(); |
7ac06cef MD |
199 | smp_mb(); |
200 | } | |
201 | ||
202 | static inline void _rcu_thread_offline(void) | |
203 | { | |
204 | smp_mb(); | |
4f8e3380 MD |
205 | STORE_SHARED(urcu_reader.ctr, 0); |
206 | smp_mb(); /* write urcu_reader.ctr before read futex */ | |
bc6c15bb | 207 | wake_up_gp(); |
7ac06cef MD |
208 | } |
209 | ||
210 | static inline void _rcu_thread_online(void) | |
211 | { | |
4f8e3380 | 212 | _STORE_SHARED(urcu_reader.ctr, LOAD_SHARED(urcu_gp_ctr)); |
7ac06cef MD |
213 | smp_mb(); |
214 | } | |
215 | ||
7ac06cef | 216 | #endif /* _URCU_QSBR_STATIC_H */ |