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fdee2e6d MD |
1 | #ifndef _URCU_BP_STATIC_H |
2 | #define _URCU_BP_STATIC_H | |
3 | ||
4 | /* | |
5 | * urcu-bp-static.h | |
6 | * | |
7 | * Userspace RCU 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. | |
fdee2e6d | 11 | * |
6982d6d7 | 12 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
fdee2e6d 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> | |
fdee2e6d MD |
34 | #include <unistd.h> |
35 | ||
36 | #include <urcu/compiler.h> | |
37 | #include <urcu/arch.h> | |
38 | #include <urcu/system.h> | |
a2e7bf9c | 39 | #include <urcu/uatomic.h> |
fdee2e6d | 40 | #include <urcu/list.h> |
bd252a04 | 41 | #include <urcu/tls-compat.h> |
fdee2e6d MD |
42 | |
43 | /* | |
44 | * This code section can only be included in LGPL 2.1 compatible source code. | |
45 | * See below for the function call wrappers which can be used in code meant to | |
46 | * be only linked with the Userspace RCU library. This comes with a small | |
47 | * performance degradation on the read-side due to the added function calls. | |
48 | * This is required to permit relinking with newer versions of the library. | |
49 | */ | |
50 | ||
36bc70a8 MD |
51 | #ifdef __cplusplus |
52 | extern "C" { | |
53 | #endif | |
54 | ||
fdee2e6d MD |
55 | #ifdef DEBUG_RCU |
56 | #define rcu_assert(args...) assert(args) | |
57 | #else | |
58 | #define rcu_assert(args...) | |
59 | #endif | |
60 | ||
52c75091 MD |
61 | enum rcu_state { |
62 | RCU_READER_ACTIVE_CURRENT, | |
63 | RCU_READER_ACTIVE_OLD, | |
64 | RCU_READER_INACTIVE, | |
65 | }; | |
66 | ||
fdee2e6d MD |
67 | #ifdef DEBUG_YIELD |
68 | #include <sched.h> | |
69 | #include <time.h> | |
70 | #include <pthread.h> | |
71 | #include <unistd.h> | |
72 | ||
1de4df4b MD |
73 | #define RCU_YIELD_READ (1 << 0) |
74 | #define RCU_YIELD_WRITE (1 << 1) | |
fdee2e6d MD |
75 | |
76 | /* | |
02be5561 | 77 | * Updates without RCU_MB are much slower. Account this in |
fdee2e6d MD |
78 | * the delay. |
79 | */ | |
80 | /* maximum sleep delay, in us */ | |
81 | #define MAX_SLEEP 50 | |
82 | ||
1de4df4b MD |
83 | extern unsigned int rcu_yield_active; |
84 | extern DECLARE_URCU_TLS(unsigned int, rcu_rand_yield); | |
fdee2e6d | 85 | |
1de4df4b | 86 | static inline void rcu_debug_yield_read(void) |
fdee2e6d | 87 | { |
1de4df4b MD |
88 | if (rcu_yield_active & RCU_YIELD_READ) |
89 | if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1) | |
90 | usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP); | |
fdee2e6d MD |
91 | } |
92 | ||
1de4df4b | 93 | static inline void rcu_debug_yield_write(void) |
fdee2e6d | 94 | { |
1de4df4b MD |
95 | if (rcu_yield_active & RCU_YIELD_WRITE) |
96 | if (rand_r(&URCU_TLS(rcu_rand_yield)) & 0x1) | |
97 | usleep(rand_r(&URCU_TLS(rcu_rand_yield)) % MAX_SLEEP); | |
fdee2e6d MD |
98 | } |
99 | ||
1de4df4b | 100 | static inline void rcu_debug_yield_init(void) |
fdee2e6d | 101 | { |
6ff854ac | 102 | URCU_TLS(rcu_rand_yield) = time(NULL) ^ (unsigned long) pthread_self(); |
fdee2e6d MD |
103 | } |
104 | #else | |
1de4df4b | 105 | static inline void rcu_debug_yield_read(void) |
fdee2e6d MD |
106 | { |
107 | } | |
108 | ||
1de4df4b | 109 | static inline void rcu_debug_yield_write(void) |
fdee2e6d MD |
110 | { |
111 | } | |
112 | ||
1de4df4b | 113 | static inline void rcu_debug_yield_init(void) |
fdee2e6d MD |
114 | { |
115 | ||
116 | } | |
117 | #endif | |
118 | ||
119 | /* | |
02be5561 | 120 | * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use a |
fdee2e6d MD |
121 | * full 8-bits, 16-bits or 32-bits bitmask for the lower order bits. |
122 | */ | |
123 | #define RCU_GP_COUNT (1UL << 0) | |
124 | /* Use the amount of bits equal to half of the architecture long size */ | |
02be5561 MD |
125 | #define RCU_GP_CTR_PHASE (1UL << (sizeof(long) << 2)) |
126 | #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1) | |
fdee2e6d MD |
127 | |
128 | /* | |
129 | * Used internally by _rcu_read_lock. | |
130 | */ | |
131 | extern void rcu_bp_register(void); | |
132 | ||
c13c2e55 MD |
133 | struct rcu_gp { |
134 | /* | |
135 | * Global grace period counter. | |
136 | * Contains the current RCU_GP_CTR_PHASE. | |
137 | * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. | |
138 | * Written to only by writer with mutex taken. | |
139 | * Read by both writer and readers. | |
140 | */ | |
141 | unsigned long ctr; | |
142 | } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); | |
143 | ||
144 | extern struct rcu_gp rcu_gp; | |
fdee2e6d | 145 | |
02be5561 | 146 | struct rcu_reader { |
fdee2e6d | 147 | /* Data used by both reader and synchronize_rcu() */ |
52c75091 | 148 | unsigned long ctr; |
fdee2e6d | 149 | /* Data used for registry */ |
16aa9ee8 | 150 | struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
fdee2e6d MD |
151 | pthread_t tid; |
152 | int alloc; /* registry entry allocated */ | |
153 | }; | |
154 | ||
155 | /* | |
156 | * Bulletproof version keeps a pointer to a registry not part of the TLS. | |
157 | * Adds a pointer dereference on the read-side, but won't require to unregister | |
158 | * the reader thread. | |
159 | */ | |
bd252a04 | 160 | extern DECLARE_URCU_TLS(struct rcu_reader *, rcu_reader); |
fdee2e6d | 161 | |
52c75091 | 162 | static inline enum rcu_state rcu_reader_state(unsigned long *ctr) |
fdee2e6d | 163 | { |
52c75091 | 164 | unsigned long v; |
fdee2e6d | 165 | |
52c75091 MD |
166 | if (ctr == NULL) |
167 | return RCU_READER_INACTIVE; | |
fdee2e6d MD |
168 | /* |
169 | * Make sure both tests below are done on the same version of *value | |
170 | * to insure consistency. | |
171 | */ | |
52c75091 MD |
172 | v = CMM_LOAD_SHARED(*ctr); |
173 | if (!(v & RCU_GP_CTR_NEST_MASK)) | |
174 | return RCU_READER_INACTIVE; | |
c13c2e55 | 175 | if (!((v ^ rcu_gp.ctr) & RCU_GP_CTR_PHASE)) |
52c75091 MD |
176 | return RCU_READER_ACTIVE_CURRENT; |
177 | return RCU_READER_ACTIVE_OLD; | |
fdee2e6d MD |
178 | } |
179 | ||
a5a9f428 | 180 | /* |
c13c2e55 | 181 | * Helper for _rcu_read_lock(). The format of rcu_gp.ctr (as well as |
a5a9f428 PM |
182 | * the per-thread rcu_reader.ctr) has the upper bits containing a count of |
183 | * _rcu_read_lock() nesting, and a lower-order bit that contains either zero | |
184 | * or RCU_GP_CTR_PHASE. The smp_mb_slave() ensures that the accesses in | |
185 | * _rcu_read_lock() happen before the subsequent read-side critical section. | |
186 | */ | |
187 | static inline void _rcu_read_lock_update(unsigned long tmp) | |
188 | { | |
189 | if (caa_likely(!(tmp & RCU_GP_CTR_NEST_MASK))) { | |
c13c2e55 | 190 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, _CMM_LOAD_SHARED(rcu_gp.ctr)); |
a5a9f428 PM |
191 | cmm_smp_mb(); |
192 | } else | |
193 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, tmp + RCU_GP_COUNT); | |
194 | } | |
195 | ||
196 | /* | |
197 | * Enter an RCU read-side critical section. | |
198 | * | |
199 | * The first cmm_barrier() call ensures that the compiler does not reorder | |
200 | * the body of _rcu_read_lock() with a mutex. | |
201 | * | |
202 | * This function and its helper are both less than 10 lines long. The | |
203 | * intent is that this function meets the 10-line criterion in LGPL, | |
204 | * allowing this function to be invoked directly from non-LGPL code. | |
205 | */ | |
fdee2e6d MD |
206 | static inline void _rcu_read_lock(void) |
207 | { | |
52c75091 | 208 | unsigned long tmp; |
fdee2e6d | 209 | |
bd252a04 | 210 | if (caa_unlikely(!URCU_TLS(rcu_reader))) |
a5a9f428 | 211 | rcu_bp_register(); /* If not yet registered. */ |
5481ddb3 | 212 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
bd252a04 | 213 | tmp = URCU_TLS(rcu_reader)->ctr; |
a5a9f428 | 214 | _rcu_read_lock_update(tmp); |
fdee2e6d MD |
215 | } |
216 | ||
a5a9f428 PM |
217 | /* |
218 | * Exit an RCU read-side critical section. This function is less than | |
219 | * 10 lines of code, and is intended to be usable by non-LGPL code, as | |
220 | * called out in LGPL. | |
221 | */ | |
fdee2e6d MD |
222 | static inline void _rcu_read_unlock(void) |
223 | { | |
224 | /* | |
225 | * Finish using rcu before decrementing the pointer. | |
226 | */ | |
5481ddb3 | 227 | cmm_smp_mb(); |
bd252a04 | 228 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader)->ctr, URCU_TLS(rcu_reader)->ctr - RCU_GP_COUNT); |
5481ddb3 | 229 | cmm_barrier(); /* Ensure the compiler does not reorder us with mutex */ |
fdee2e6d MD |
230 | } |
231 | ||
882f3357 MD |
232 | /* |
233 | * Returns whether within a RCU read-side critical section. | |
234 | * | |
235 | * This function is less than 10 lines long. The intent is that this | |
236 | * function meets the 10-line criterion for LGPL, allowing this function | |
237 | * to be invoked directly from non-LGPL code. | |
238 | */ | |
239 | static inline int _rcu_read_ongoing(void) | |
240 | { | |
241 | if (caa_unlikely(!URCU_TLS(rcu_reader))) | |
242 | rcu_bp_register(); /* If not yet registered. */ | |
243 | return URCU_TLS(rcu_reader)->ctr & RCU_GP_CTR_NEST_MASK; | |
244 | } | |
245 | ||
36bc70a8 MD |
246 | #ifdef __cplusplus |
247 | } | |
248 | #endif | |
249 | ||
fdee2e6d | 250 | #endif /* _URCU_BP_STATIC_H */ |