| 1 | #ifndef _URCU_STATIC_H |
| 2 | #define _URCU_STATIC_H |
| 3 | |
| 4 | /* |
| 5 | * urcu-static.h |
| 6 | * |
| 7 | * Userspace RCU header. |
| 8 | * |
| 9 | * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking |
| 10 | * dynamically with the userspace rcu 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 <syscall.h> |
| 35 | #include <unistd.h> |
| 36 | |
| 37 | #include <urcu/compiler.h> |
| 38 | #include <urcu/arch.h> |
| 39 | #include <urcu/system.h> |
| 40 | #include <urcu/uatomic_arch.h> |
| 41 | #include <urcu/list.h> |
| 42 | #include <urcu/urcu-futex.h> |
| 43 | |
| 44 | #ifdef __cplusplus |
| 45 | extern "C" { |
| 46 | #endif |
| 47 | |
| 48 | /* Default is RCU_MEMBARRIER */ |
| 49 | #if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL) |
| 50 | #define RCU_MEMBARRIER |
| 51 | #endif |
| 52 | |
| 53 | #ifdef RCU_MEMBARRIER |
| 54 | #include <unistd.h> |
| 55 | #include <sys/syscall.h> |
| 56 | |
| 57 | /* If the headers do not support SYS_membarrier, statically use RCU_MB */ |
| 58 | #ifdef SYS_membarrier |
| 59 | # define MEMBARRIER_EXPEDITED (1 << 0) |
| 60 | # define MEMBARRIER_DELAYED (1 << 1) |
| 61 | # define MEMBARRIER_QUERY (1 << 16) |
| 62 | # define membarrier(...) syscall(SYS_membarrier, __VA_ARGS__) |
| 63 | #else |
| 64 | # undef RCU_MEMBARRIER |
| 65 | # define RCU_MB |
| 66 | #endif |
| 67 | #endif |
| 68 | |
| 69 | /* |
| 70 | * This code section can only be included in LGPL 2.1 compatible source code. |
| 71 | * See below for the function call wrappers which can be used in code meant to |
| 72 | * be only linked with the Userspace RCU library. This comes with a small |
| 73 | * performance degradation on the read-side due to the added function calls. |
| 74 | * This is required to permit relinking with newer versions of the library. |
| 75 | */ |
| 76 | |
| 77 | /* |
| 78 | * The signal number used by the RCU library can be overridden with |
| 79 | * -DSIGRCU= when compiling the library. |
| 80 | * Provide backward compatibility for liburcu 0.3.x SIGURCU. |
| 81 | */ |
| 82 | #ifdef SIGURCU |
| 83 | #define SIGRCU SIGURCU |
| 84 | #endif |
| 85 | |
| 86 | #ifndef SIGRCU |
| 87 | #define SIGRCU SIGUSR1 |
| 88 | #endif |
| 89 | |
| 90 | /* |
| 91 | * If a reader is really non-cooperative and refuses to commit its |
| 92 | * rcu_active_readers count to memory (there is no barrier in the reader |
| 93 | * per-se), kick it after a few loops waiting for it. |
| 94 | */ |
| 95 | #define KICK_READER_LOOPS 10000 |
| 96 | |
| 97 | /* |
| 98 | * Active attempts to check for reader Q.S. before calling futex(). |
| 99 | */ |
| 100 | #define RCU_QS_ACTIVE_ATTEMPTS 100 |
| 101 | |
| 102 | #ifdef DEBUG_RCU |
| 103 | #define rcu_assert(args...) assert(args) |
| 104 | #else |
| 105 | #define rcu_assert(args...) |
| 106 | #endif |
| 107 | |
| 108 | #ifdef DEBUG_YIELD |
| 109 | #include <sched.h> |
| 110 | #include <time.h> |
| 111 | #include <pthread.h> |
| 112 | #include <unistd.h> |
| 113 | |
| 114 | #define YIELD_READ (1 << 0) |
| 115 | #define YIELD_WRITE (1 << 1) |
| 116 | |
| 117 | /* |
| 118 | * Updates with RCU_SIGNAL are much slower. Account this in the delay. |
| 119 | */ |
| 120 | #ifdef RCU_SIGNAL |
| 121 | /* maximum sleep delay, in us */ |
| 122 | #define MAX_SLEEP 30000 |
| 123 | #else |
| 124 | #define MAX_SLEEP 50 |
| 125 | #endif |
| 126 | |
| 127 | extern unsigned int yield_active; |
| 128 | extern unsigned int __thread rand_yield; |
| 129 | |
| 130 | static inline void debug_yield_read(void) |
| 131 | { |
| 132 | if (yield_active & YIELD_READ) |
| 133 | if (rand_r(&rand_yield) & 0x1) |
| 134 | usleep(rand_r(&rand_yield) % MAX_SLEEP); |
| 135 | } |
| 136 | |
| 137 | static inline void debug_yield_write(void) |
| 138 | { |
| 139 | if (yield_active & YIELD_WRITE) |
| 140 | if (rand_r(&rand_yield) & 0x1) |
| 141 | usleep(rand_r(&rand_yield) % MAX_SLEEP); |
| 142 | } |
| 143 | |
| 144 | static inline void debug_yield_init(void) |
| 145 | { |
| 146 | rand_yield = time(NULL) ^ pthread_self(); |
| 147 | } |
| 148 | #else |
| 149 | static inline void debug_yield_read(void) |
| 150 | { |
| 151 | } |
| 152 | |
| 153 | static inline void debug_yield_write(void) |
| 154 | { |
| 155 | } |
| 156 | |
| 157 | static inline void debug_yield_init(void) |
| 158 | { |
| 159 | |
| 160 | } |
| 161 | #endif |
| 162 | |
| 163 | /* |
| 164 | * RCU memory barrier broadcast group. Currently, only broadcast to all process |
| 165 | * threads is supported (group 0). |
| 166 | * |
| 167 | * Slave barriers are only guaranteed to be ordered wrt master barriers. |
| 168 | * |
| 169 | * The pair ordering is detailed as (O: ordered, X: not ordered) : |
| 170 | * slave master |
| 171 | * slave X O |
| 172 | * master O O |
| 173 | */ |
| 174 | |
| 175 | #define MB_GROUP_ALL 0 |
| 176 | #define RCU_MB_GROUP MB_GROUP_ALL |
| 177 | |
| 178 | #ifdef RCU_MEMBARRIER |
| 179 | extern int has_sys_membarrier; |
| 180 | |
| 181 | static inline void smp_mb_slave(int group) |
| 182 | { |
| 183 | if (likely(has_sys_membarrier)) |
| 184 | barrier(); |
| 185 | else |
| 186 | smp_mb(); |
| 187 | } |
| 188 | #endif |
| 189 | |
| 190 | #ifdef RCU_MB |
| 191 | static inline void smp_mb_slave(int group) |
| 192 | { |
| 193 | smp_mb(); |
| 194 | } |
| 195 | #endif |
| 196 | |
| 197 | #ifdef RCU_SIGNAL |
| 198 | static inline void smp_mb_slave(int group) |
| 199 | { |
| 200 | barrier(); |
| 201 | } |
| 202 | #endif |
| 203 | |
| 204 | /* |
| 205 | * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use |
| 206 | * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits. |
| 207 | */ |
| 208 | #define RCU_GP_COUNT (1UL << 0) |
| 209 | /* Use the amount of bits equal to half of the architecture long size */ |
| 210 | #define RCU_GP_CTR_PHASE (1UL << (sizeof(unsigned long) << 2)) |
| 211 | #define RCU_GP_CTR_NEST_MASK (RCU_GP_CTR_PHASE - 1) |
| 212 | |
| 213 | /* |
| 214 | * Global quiescent period counter with low-order bits unused. |
| 215 | * Using a int rather than a char to eliminate false register dependencies |
| 216 | * causing stalls on some architectures. |
| 217 | */ |
| 218 | extern unsigned long rcu_gp_ctr; |
| 219 | |
| 220 | struct rcu_reader { |
| 221 | /* Data used by both reader and synchronize_rcu() */ |
| 222 | unsigned long ctr; |
| 223 | char need_mb; |
| 224 | /* Data used for registry */ |
| 225 | struct list_head node __attribute__((aligned(CACHE_LINE_SIZE))); |
| 226 | pthread_t tid; |
| 227 | }; |
| 228 | |
| 229 | extern struct rcu_reader __thread rcu_reader; |
| 230 | |
| 231 | extern int gp_futex; |
| 232 | |
| 233 | /* |
| 234 | * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. |
| 235 | */ |
| 236 | static inline void wake_up_gp(void) |
| 237 | { |
| 238 | if (unlikely(uatomic_read(&gp_futex) == -1)) { |
| 239 | uatomic_set(&gp_futex, 0); |
| 240 | futex_async(&gp_futex, FUTEX_WAKE, 1, |
| 241 | NULL, NULL, 0); |
| 242 | } |
| 243 | } |
| 244 | |
| 245 | static inline int rcu_gp_ongoing(unsigned long *ctr) |
| 246 | { |
| 247 | unsigned long v; |
| 248 | |
| 249 | /* |
| 250 | * Make sure both tests below are done on the same version of *value |
| 251 | * to insure consistency. |
| 252 | */ |
| 253 | v = LOAD_SHARED(*ctr); |
| 254 | return (v & RCU_GP_CTR_NEST_MASK) && |
| 255 | ((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE); |
| 256 | } |
| 257 | |
| 258 | static inline void _rcu_read_lock(void) |
| 259 | { |
| 260 | unsigned long tmp; |
| 261 | |
| 262 | tmp = rcu_reader.ctr; |
| 263 | /* |
| 264 | * rcu_gp_ctr is |
| 265 | * RCU_GP_COUNT | (~RCU_GP_CTR_PHASE or RCU_GP_CTR_PHASE) |
| 266 | */ |
| 267 | if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) { |
| 268 | _STORE_SHARED(rcu_reader.ctr, _LOAD_SHARED(rcu_gp_ctr)); |
| 269 | /* |
| 270 | * Set active readers count for outermost nesting level before |
| 271 | * accessing the pointer. See smp_mb_master(). |
| 272 | */ |
| 273 | smp_mb_slave(RCU_MB_GROUP); |
| 274 | } else { |
| 275 | _STORE_SHARED(rcu_reader.ctr, tmp + RCU_GP_COUNT); |
| 276 | } |
| 277 | } |
| 278 | |
| 279 | static inline void _rcu_read_unlock(void) |
| 280 | { |
| 281 | unsigned long tmp; |
| 282 | |
| 283 | tmp = rcu_reader.ctr; |
| 284 | /* |
| 285 | * Finish using rcu before decrementing the pointer. |
| 286 | * See smp_mb_master(). |
| 287 | */ |
| 288 | if (likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) { |
| 289 | smp_mb_slave(RCU_MB_GROUP); |
| 290 | _STORE_SHARED(rcu_reader.ctr, rcu_reader.ctr - RCU_GP_COUNT); |
| 291 | /* write rcu_reader.ctr before read futex */ |
| 292 | smp_mb_slave(RCU_MB_GROUP); |
| 293 | wake_up_gp(); |
| 294 | } else { |
| 295 | _STORE_SHARED(rcu_reader.ctr, rcu_reader.ctr - RCU_GP_COUNT); |
| 296 | } |
| 297 | } |
| 298 | |
| 299 | #ifdef __cplusplus |
| 300 | } |
| 301 | #endif |
| 302 | |
| 303 | #endif /* _URCU_STATIC_H */ |