urcu/static/urcu.h

   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@efficios.com>
  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 <unistd.h>
  35 #include <stdint.h>
  36
  37 #include <urcu/compiler.h>
  38 #include <urcu/arch.h>
  39 #include <urcu/system.h>
  40 #include <urcu/uatomic.h>
  41 #include <urcu/list.h>
  42 #include <urcu/futex.h>
  43
  44 #ifdef __cplusplus
  45 extern "C" {
  46 #endif
  47
  48 /* Default is RCU_MEMBARRIER on linux */
  49 #if !defined(RCU_MEMBARRIER) && !defined(RCU_MB) && !defined(RCU_SIGNAL)
  50 # ifdef __linux__
  51 # define RCU_MEMBARRIER
  52 # else
  53 # define RCU_MB
  54 # endif
  55 #endif
  56
  57 #ifdef RCU_MEMBARRIER
  58 #include <syscall.h>
  59
  60 /* If the headers do not support SYS_membarrier, statically use RCU_MB */
  61 #ifdef SYS_membarrier
  62 # define MEMBARRIER_EXPEDITED           (1 << 0)
  63 # define MEMBARRIER_DELAYED             (1 << 1)
  64 # define MEMBARRIER_QUERY               (1 << 16)
  65 # define membarrier(...)                syscall(SYS_membarrier, __VA_ARGS__)
  66 #else
  67 # undef RCU_MEMBARRIER
  68 # define RCU_MB
  69 #endif
  70 #endif
  71
  72 /*
  73  * This code section can only be included in LGPL 2.1 compatible source code.
  74  * See below for the function call wrappers which can be used in code meant to
  75  * be only linked with the Userspace RCU library. This comes with a small
  76  * performance degradation on the read-side due to the added function calls.
  77  * This is required to permit relinking with newer versions of the library.
  78  */
  79
  80 /*
  81  * The signal number used by the RCU library can be overridden with
  82  * -DSIGRCU= when compiling the library.
  83  * Provide backward compatibility for liburcu 0.3.x SIGURCU.
  84  */
  85 #ifdef SIGURCU
  86 #define SIGRCU SIGURCU
  87 #endif
  88
  89 #ifndef SIGRCU
  90 #define SIGRCU SIGUSR1
  91 #endif
  92
  93 /*
  94  * If a reader is really non-cooperative and refuses to commit its
  95  * rcu_active_readers count to memory (there is no barrier in the reader
  96  * per-se), kick it after a few loops waiting for it.
  97  */
  98 #define KICK_READER_LOOPS 10000
  99
 100 /*
 101  * Active attempts to check for reader Q.S. before calling futex().
 102  */
 103 #define RCU_QS_ACTIVE_ATTEMPTS 100
 104
 105 #ifdef DEBUG_RCU
 106 #define rcu_assert(args...)     assert(args)
 107 #else
 108 #define rcu_assert(args...)
 109 #endif
 110
 111 #ifdef DEBUG_YIELD
 112 #include <sched.h>
 113 #include <time.h>
 114 #include <pthread.h>
 115 #include <unistd.h>
 116
 117 #define YIELD_READ      (1 << 0)
 118 #define YIELD_WRITE     (1 << 1)
 119
 120 /*
 121  * Updates with RCU_SIGNAL are much slower. Account this in the delay.
 122  */
 123 #ifdef RCU_SIGNAL
 124 /* maximum sleep delay, in us */
 125 #define MAX_SLEEP 30000
 126 #else
 127 #define MAX_SLEEP 50
 128 #endif
 129
 130 extern unsigned int yield_active;
 131 extern unsigned int __thread rand_yield;
 132
 133 static inline void debug_yield_read(void)
 134 {
 135         if (yield_active & YIELD_READ)
 136                 if (rand_r(&rand_yield) & 0x1)
 137                         usleep(rand_r(&rand_yield) % MAX_SLEEP);
 138 }
 139
 140 static inline void debug_yield_write(void)
 141 {
 142         if (yield_active & YIELD_WRITE)
 143                 if (rand_r(&rand_yield) & 0x1)
 144                         usleep(rand_r(&rand_yield) % MAX_SLEEP);
 145 }
 146
 147 static inline void debug_yield_init(void)
 148 {
 149         rand_yield = time(NULL) ^ pthread_self();
 150 }
 151 #else
 152 static inline void debug_yield_read(void)
 153 {
 154 }
 155
 156 static inline void debug_yield_write(void)
 157 {
 158 }
 159
 160 static inline void debug_yield_init(void)
 161 {
 162
 163 }
 164 #endif
 165
 166 /*
 167  * RCU memory barrier broadcast group. Currently, only broadcast to all process
 168  * threads is supported (group 0).
 169  *
 170  * Slave barriers are only guaranteed to be ordered wrt master barriers.
 171  *
 172  * The pair ordering is detailed as (O: ordered, X: not ordered) :
 173  *               slave  master
 174  *        slave    X      O
 175  *        master   O      O
 176  */
 177
 178 #define MB_GROUP_ALL            0
 179 #define RCU_MB_GROUP            MB_GROUP_ALL
 180
 181 #ifdef RCU_MEMBARRIER
 182 extern int has_sys_membarrier;
 183
 184 static inline void smp_mb_slave(int group)
 185 {
 186         if (likely(has_sys_membarrier))
 187                 cmm_barrier();
 188         else
 189                 cmm_smp_mb();
 190 }
 191 #endif
 192
 193 #ifdef RCU_MB
 194 static inline void smp_mb_slave(int group)
 195 {
 196         cmm_smp_mb();
 197 }
 198 #endif
 199
 200 #ifdef RCU_SIGNAL
 201 static inline void smp_mb_slave(int group)
 202 {
 203         cmm_barrier();
 204 }
 205 #endif
 206
 207 /*
 208  * The trick here is that RCU_GP_CTR_PHASE must be a multiple of 8 so we can use
 209  * a full 8-bits, 16-bits or 32-bits bitmask for the lower order bits.
 210  */
 211 #define RCU_GP_COUNT            (1UL << 0)
 212 /* Use the amount of bits equal to half of the architecture long size */
 213 #define RCU_GP_CTR_PHASE        (1UL << (sizeof(unsigned long) << 2))
 214 #define RCU_GP_CTR_NEST_MASK    (RCU_GP_CTR_PHASE - 1)
 215
 216 /*
 217  * Global quiescent period counter with low-order bits unused.
 218  * Using a int rather than a char to eliminate false register dependencies
 219  * causing stalls on some architectures.
 220  */
 221 extern unsigned long rcu_gp_ctr;
 222
 223 struct rcu_reader {
 224         /* Data used by both reader and synchronize_rcu() */
 225         unsigned long ctr;
 226         char need_mb;
 227         /* Data used for registry */
 228         struct cds_list_head node __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 229         pthread_t tid;
 230 };
 231
 232 extern struct rcu_reader __thread rcu_reader;
 233
 234 extern int32_t gp_futex;
 235
 236 /*
 237  * Wake-up waiting synchronize_rcu(). Called from many concurrent threads.
 238  */
 239 static inline void wake_up_gp(void)
 240 {
 241         if (unlikely(uatomic_read(&gp_futex) == -1)) {
 242                 uatomic_set(&gp_futex, 0);
 243                 futex_async(&gp_futex, FUTEX_WAKE, 1,
 244                       NULL, NULL, 0);
 245         }
 246 }
 247
 248 static inline int rcu_gp_ongoing(unsigned long *ctr)
 249 {
 250         unsigned long v;
 251
 252         /*
 253          * Make sure both tests below are done on the same version of *value
 254          * to insure consistency.
 255          */
 256         v = CMM_LOAD_SHARED(*ctr);
 257         return (v & RCU_GP_CTR_NEST_MASK) &&
 258                  ((v ^ rcu_gp_ctr) & RCU_GP_CTR_PHASE);
 259 }
 260
 261 static inline void _rcu_read_lock(void)
 262 {
 263         unsigned long tmp;
 264
 265         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 266         tmp = rcu_reader.ctr;
 267         /*
 268          * rcu_gp_ctr is
 269          *   RCU_GP_COUNT | (~RCU_GP_CTR_PHASE or RCU_GP_CTR_PHASE)
 270          */
 271         if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) {
 272                 _CMM_STORE_SHARED(rcu_reader.ctr, _CMM_LOAD_SHARED(rcu_gp_ctr));
 273                 /*
 274                  * Set active readers count for outermost nesting level before
 275                  * accessing the pointer. See smp_mb_master().
 276                  */
 277                 smp_mb_slave(RCU_MB_GROUP);
 278         } else {
 279                 _CMM_STORE_SHARED(rcu_reader.ctr, tmp + RCU_GP_COUNT);
 280         }
 281 }
 282
 283 static inline void _rcu_read_unlock(void)
 284 {
 285         unsigned long tmp;
 286
 287         tmp = rcu_reader.ctr;
 288         /*
 289          * Finish using rcu before decrementing the pointer.
 290          * See smp_mb_master().
 291          */
 292         if (likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) {
 293                 smp_mb_slave(RCU_MB_GROUP);
 294                 _CMM_STORE_SHARED(rcu_reader.ctr, rcu_reader.ctr - RCU_GP_COUNT);
 295                 /* write rcu_reader.ctr before read futex */
 296                 smp_mb_slave(RCU_MB_GROUP);
 297                 wake_up_gp();
 298         } else {
 299                 _CMM_STORE_SHARED(rcu_reader.ctr, rcu_reader.ctr - RCU_GP_COUNT);
 300         }
 301         cmm_barrier();  /* Ensure the compiler does not reorder us with mutex */
 302 }
 303
 304 #ifdef __cplusplus
 305 }
 306 #endif
 307
 308 #endif /* _URCU_STATIC_H */