src/urcu-bp.c

   1 /*
   2  * urcu-bp.c
   3  *
   4  * Userspace RCU library, "bulletproof" version.
   5  *
   6  * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  *
  23  * IBM's contributions to this file may be relicensed under LGPLv2 or later.
  24  */
  25
  26 #define URCU_NO_COMPAT_IDENTIFIERS
  27 #define _LGPL_SOURCE
  28 #include <stdio.h>
  29 #include <pthread.h>
  30 #include <signal.h>
  31 #include <assert.h>
  32 #include <stdlib.h>
  33 #include <string.h>
  34 #include <errno.h>
  35 #include <poll.h>
  36 #include <unistd.h>
  37 #include <stdbool.h>
  38 #include <sys/mman.h>
  39
  40 #include <urcu/config.h>
  41 #include <urcu/arch.h>
  42 #include <urcu/wfcqueue.h>
  43 #include <urcu/map/urcu-bp.h>
  44 #include <urcu/static/urcu-bp.h>
  45 #include <urcu/pointer.h>
  46 #include <urcu/tls-compat.h>
  47
  48 #include "urcu-die.h"
  49 #include "urcu-utils.h"
  50
  51 #define URCU_API_MAP
  52 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
  53 #undef _LGPL_SOURCE
  54 #include <urcu/urcu-bp.h>
  55 #define _LGPL_SOURCE
  56
  57 #ifndef MAP_ANONYMOUS
  58 #define MAP_ANONYMOUS MAP_ANON
  59 #endif
  60
  61 #ifdef __linux__
  62 static
  63 void *mremap_wrapper(void *old_address, size_t old_size,
  64                 size_t new_size, int flags)
  65 {
  66         return mremap(old_address, old_size, new_size, flags);
  67 }
  68 #else
  69
  70 #define MREMAP_MAYMOVE  1
  71 #define MREMAP_FIXED    2
  72
  73 /*
  74  * mremap wrapper for non-Linux systems not allowing MAYMOVE.
  75  * This is not generic.
  76 */
  77 static
  78 void *mremap_wrapper(void *old_address __attribute__((unused)),
  79                 size_t old_size __attribute__((unused)),
  80                 size_t new_size __attribute__((unused)),
  81                 int flags)
  82 {
  83         assert(!(flags & MREMAP_MAYMOVE));
  84
  85         return MAP_FAILED;
  86 }
  87 #endif
  88
  89 /* Sleep delay in ms */
  90 #define RCU_SLEEP_DELAY_MS      10
  91 #define INIT_NR_THREADS         8
  92 #define ARENA_INIT_ALLOC                \
  93         sizeof(struct registry_chunk)   \
  94         + INIT_NR_THREADS * sizeof(struct urcu_bp_reader)
  95
  96 /*
  97  * Active attempts to check for reader Q.S. before calling sleep().
  98  */
  99 #define RCU_QS_ACTIVE_ATTEMPTS 100
 100
 101 static
 102 int urcu_bp_refcount;
 103
 104 /* If the headers do not support membarrier system call, fall back smp_mb. */
 105 #ifdef __NR_membarrier
 106 # define membarrier(...)                syscall(__NR_membarrier, __VA_ARGS__)
 107 #else
 108 # define membarrier(...)                -ENOSYS
 109 #endif
 110
 111 enum membarrier_cmd {
 112         MEMBARRIER_CMD_QUERY                            = 0,
 113         MEMBARRIER_CMD_SHARED                           = (1 << 0),
 114         /* reserved for MEMBARRIER_CMD_SHARED_EXPEDITED (1 << 1) */
 115         /* reserved for MEMBARRIER_CMD_PRIVATE (1 << 2) */
 116         MEMBARRIER_CMD_PRIVATE_EXPEDITED                = (1 << 3),
 117         MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED       = (1 << 4),
 118 };
 119
 120 static
 121 void __attribute__((constructor)) _urcu_bp_init(void);
 122 static
 123 void urcu_bp_exit(void);
 124 static
 125 void __attribute__((destructor)) urcu_bp_exit_destructor(void);
 126 static void urcu_call_rcu_exit(void);
 127
 128 #ifndef CONFIG_RCU_FORCE_SYS_MEMBARRIER
 129 int urcu_bp_has_sys_membarrier;
 130 #endif
 131
 132 /*
 133  * rcu_gp_lock ensures mutual exclusion between threads calling
 134  * synchronize_rcu().
 135  */
 136 static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
 137 /*
 138  * rcu_registry_lock ensures mutual exclusion between threads
 139  * registering and unregistering themselves to/from the registry, and
 140  * with threads reading that registry from synchronize_rcu(). However,
 141  * this lock is not held all the way through the completion of awaiting
 142  * for the grace period. It is sporadically released between iterations
 143  * on the registry.
 144  * rcu_registry_lock may nest inside rcu_gp_lock.
 145  */
 146 static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER;
 147
 148 static pthread_mutex_t init_lock = PTHREAD_MUTEX_INITIALIZER;
 149 static int initialized;
 150
 151 static pthread_key_t urcu_bp_key;
 152
 153 struct urcu_bp_gp urcu_bp_gp = { .ctr = URCU_BP_GP_COUNT };
 154 URCU_ATTR_ALIAS("urcu_bp_gp") extern struct urcu_bp_gp rcu_gp_bp;
 155
 156 /*
 157  * Pointer to registry elements. Written to only by each individual reader. Read
 158  * by both the reader and the writers.
 159  */
 160 DEFINE_URCU_TLS(struct urcu_bp_reader *, urcu_bp_reader);
 161 DEFINE_URCU_TLS_ALIAS(struct urcu_bp_reader *, urcu_bp_reader, rcu_reader_bp);
 162
 163 static CDS_LIST_HEAD(registry);
 164
 165 struct registry_chunk {
 166         size_t data_len;                /* data length */
 167         size_t used;                    /* amount of data used */
 168         struct cds_list_head node;      /* chunk_list node */
 169         char data[];
 170 };
 171
 172 struct registry_arena {
 173         struct cds_list_head chunk_list;
 174 };
 175
 176 static struct registry_arena registry_arena = {
 177         .chunk_list = CDS_LIST_HEAD_INIT(registry_arena.chunk_list),
 178 };
 179
 180 /* Saved fork signal mask, protected by rcu_gp_lock */
 181 static sigset_t saved_fork_signal_mask;
 182
 183 static void mutex_lock(pthread_mutex_t *mutex)
 184 {
 185         int ret;
 186
 187 #ifndef DISTRUST_SIGNALS_EXTREME
 188         ret = pthread_mutex_lock(mutex);
 189         if (ret)
 190                 urcu_die(ret);
 191 #else /* #ifndef DISTRUST_SIGNALS_EXTREME */
 192         while ((ret = pthread_mutex_trylock(mutex)) != 0) {
 193                 if (ret != EBUSY && ret != EINTR)
 194                         urcu_die(ret);
 195                 poll(NULL,0,10);
 196         }
 197 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
 198 }
 199
 200 static void mutex_unlock(pthread_mutex_t *mutex)
 201 {
 202         int ret;
 203
 204         ret = pthread_mutex_unlock(mutex);
 205         if (ret)
 206                 urcu_die(ret);
 207 }
 208
 209 static void smp_mb_master(void)
 210 {
 211         if (caa_likely(urcu_bp_has_sys_membarrier)) {
 212                 if (membarrier(MEMBARRIER_CMD_PRIVATE_EXPEDITED, 0))
 213                         urcu_die(errno);
 214         } else {
 215                 cmm_smp_mb();
 216         }
 217 }
 218
 219 /*
 220  * Always called with rcu_registry lock held. Releases this lock between
 221  * iterations and grabs it again. Holds the lock when it returns.
 222  */
 223 static void wait_for_readers(struct cds_list_head *input_readers,
 224                         struct cds_list_head *cur_snap_readers,
 225                         struct cds_list_head *qsreaders)
 226 {
 227         unsigned int wait_loops = 0;
 228         struct urcu_bp_reader *index, *tmp;
 229
 230         /*
 231          * Wait for each thread URCU_TLS(urcu_bp_reader).ctr to either
 232          * indicate quiescence (not nested), or observe the current
 233          * rcu_gp.ctr value.
 234          */
 235         for (;;) {
 236                 if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS)
 237                         wait_loops++;
 238
 239                 cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
 240                         switch (urcu_bp_reader_state(&index->ctr)) {
 241                         case URCU_BP_READER_ACTIVE_CURRENT:
 242                                 if (cur_snap_readers) {
 243                                         cds_list_move(&index->node,
 244                                                 cur_snap_readers);
 245                                         break;
 246                                 }
 247                                 /* Fall-through */
 248                         case URCU_BP_READER_INACTIVE:
 249                                 cds_list_move(&index->node, qsreaders);
 250                                 break;
 251                         case URCU_BP_READER_ACTIVE_OLD:
 252                                 /*
 253                                  * Old snapshot. Leaving node in
 254                                  * input_readers will make us busy-loop
 255                                  * until the snapshot becomes current or
 256                                  * the reader becomes inactive.
 257                                  */
 258                                 break;
 259                         }
 260                 }
 261
 262                 if (cds_list_empty(input_readers)) {
 263                         break;
 264                 } else {
 265                         /* Temporarily unlock the registry lock. */
 266                         mutex_unlock(&rcu_registry_lock);
 267                         if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS)
 268                                 (void) poll(NULL, 0, RCU_SLEEP_DELAY_MS);
 269                         else
 270                                 caa_cpu_relax();
 271                         /* Re-lock the registry lock before the next loop. */
 272                         mutex_lock(&rcu_registry_lock);
 273                 }
 274         }
 275 }
 276
 277 void urcu_bp_synchronize_rcu(void)
 278 {
 279         CDS_LIST_HEAD(cur_snap_readers);
 280         CDS_LIST_HEAD(qsreaders);
 281         sigset_t newmask, oldmask;
 282         int ret;
 283
 284         ret = sigfillset(&newmask);
 285         assert(!ret);
 286         ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
 287         assert(!ret);
 288
 289         mutex_lock(&rcu_gp_lock);
 290
 291         mutex_lock(&rcu_registry_lock);
 292
 293         if (cds_list_empty(&registry))
 294                 goto out;
 295
 296         /* All threads should read qparity before accessing data structure
 297          * where new ptr points to. */
 298         /* Write new ptr before changing the qparity */
 299         smp_mb_master();
 300
 301         /*
 302          * Wait for readers to observe original parity or be quiescent.
 303          * wait_for_readers() can release and grab again rcu_registry_lock
 304          * interally.
 305          */
 306         wait_for_readers(&registry, &cur_snap_readers, &qsreaders);
 307
 308         /*
 309          * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
 310          * model easier to understand. It does not have a big performance impact
 311          * anyway, given this is the write-side.
 312          */
 313         cmm_smp_mb();
 314
 315         /* Switch parity: 0 -> 1, 1 -> 0 */
 316         CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ URCU_BP_GP_CTR_PHASE);
 317
 318         /*
 319          * Must commit qparity update to memory before waiting for other parity
 320          * quiescent state. Failure to do so could result in the writer waiting
 321          * forever while new readers are always accessing data (no progress).
 322          * Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED.
 323          */
 324
 325         /*
 326          * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
 327          * model easier to understand. It does not have a big performance impact
 328          * anyway, given this is the write-side.
 329          */
 330         cmm_smp_mb();
 331
 332         /*
 333          * Wait for readers to observe new parity or be quiescent.
 334          * wait_for_readers() can release and grab again rcu_registry_lock
 335          * interally.
 336          */
 337         wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
 338
 339         /*
 340          * Put quiescent reader list back into registry.
 341          */
 342         cds_list_splice(&qsreaders, &registry);
 343
 344         /*
 345          * Finish waiting for reader threads before letting the old ptr being
 346          * freed.
 347          */
 348         smp_mb_master();
 349 out:
 350         mutex_unlock(&rcu_registry_lock);
 351         mutex_unlock(&rcu_gp_lock);
 352         ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 353         assert(!ret);
 354 }
 355 URCU_ATTR_ALIAS("urcu_bp_synchronize_rcu") void synchronize_rcu_bp();
 356
 357 /*
 358  * library wrappers to be used by non-LGPL compatible source code.
 359  */
 360
 361 void urcu_bp_read_lock(void)
 362 {
 363         _urcu_bp_read_lock();
 364 }
 365 URCU_ATTR_ALIAS("urcu_bp_read_lock") void rcu_read_lock_bp();
 366
 367 void urcu_bp_read_unlock(void)
 368 {
 369         _urcu_bp_read_unlock();
 370 }
 371 URCU_ATTR_ALIAS("urcu_bp_read_unlock") void rcu_read_unlock_bp();
 372
 373 int urcu_bp_read_ongoing(void)
 374 {
 375         return _urcu_bp_read_ongoing();
 376 }
 377 URCU_ATTR_ALIAS("urcu_bp_read_ongoing") int rcu_read_ongoing_bp();
 378
 379 /*
 380  * Only grow for now. If empty, allocate a ARENA_INIT_ALLOC sized chunk.
 381  * Else, try expanding the last chunk. If this fails, allocate a new
 382  * chunk twice as big as the last chunk.
 383  * Memory used by chunks _never_ moves. A chunk could theoretically be
 384  * freed when all "used" slots are released, but we don't do it at this
 385  * point.
 386  */
 387 static
 388 void expand_arena(struct registry_arena *arena)
 389 {
 390         struct registry_chunk *new_chunk, *last_chunk;
 391         size_t old_chunk_len, new_chunk_len;
 392
 393         /* No chunk. */
 394         if (cds_list_empty(&arena->chunk_list)) {
 395                 assert(ARENA_INIT_ALLOC >=
 396                         sizeof(struct registry_chunk)
 397                         + sizeof(struct rcu_reader));
 398                 new_chunk_len = ARENA_INIT_ALLOC;
 399                 new_chunk = (struct registry_chunk *) mmap(NULL,
 400                         new_chunk_len,
 401                         PROT_READ | PROT_WRITE,
 402                         MAP_ANONYMOUS | MAP_PRIVATE,
 403                         -1, 0);
 404                 if (new_chunk == MAP_FAILED)
 405                         abort();
 406                 memset(new_chunk, 0, new_chunk_len);
 407                 new_chunk->data_len =
 408                         new_chunk_len - sizeof(struct registry_chunk);
 409                 cds_list_add_tail(&new_chunk->node, &arena->chunk_list);
 410                 return;         /* We're done. */
 411         }
 412
 413         /* Try expanding last chunk. */
 414         last_chunk = cds_list_entry(arena->chunk_list.prev,
 415                 struct registry_chunk, node);
 416         old_chunk_len =
 417                 last_chunk->data_len + sizeof(struct registry_chunk);
 418         new_chunk_len = old_chunk_len << 1;
 419
 420         /* Don't allow memory mapping to move, just expand. */
 421         new_chunk = mremap_wrapper(last_chunk, old_chunk_len,
 422                 new_chunk_len, 0);
 423         if (new_chunk != MAP_FAILED) {
 424                 /* Should not have moved. */
 425                 assert(new_chunk == last_chunk);
 426                 memset((char *) last_chunk + old_chunk_len, 0,
 427                         new_chunk_len - old_chunk_len);
 428                 last_chunk->data_len =
 429                         new_chunk_len - sizeof(struct registry_chunk);
 430                 return;         /* We're done. */
 431         }
 432
 433         /* Remap did not succeed, we need to add a new chunk. */
 434         new_chunk = (struct registry_chunk *) mmap(NULL,
 435                 new_chunk_len,
 436                 PROT_READ | PROT_WRITE,
 437                 MAP_ANONYMOUS | MAP_PRIVATE,
 438                 -1, 0);
 439         if (new_chunk == MAP_FAILED)
 440                 abort();
 441         memset(new_chunk, 0, new_chunk_len);
 442         new_chunk->data_len =
 443                 new_chunk_len - sizeof(struct registry_chunk);
 444         cds_list_add_tail(&new_chunk->node, &arena->chunk_list);
 445 }
 446
 447 static
 448 struct rcu_reader *arena_alloc(struct registry_arena *arena)
 449 {
 450         struct registry_chunk *chunk;
 451         struct rcu_reader *rcu_reader_reg;
 452         int expand_done = 0;    /* Only allow to expand once per alloc */
 453         size_t len = sizeof(struct rcu_reader);
 454
 455 retry:
 456         cds_list_for_each_entry(chunk, &arena->chunk_list, node) {
 457                 if (chunk->data_len - chunk->used < len)
 458                         continue;
 459                 /* Find spot */
 460                 for (rcu_reader_reg = (struct rcu_reader *) &chunk->data[0];
 461                                 rcu_reader_reg < (struct rcu_reader *) &chunk->data[chunk->data_len];
 462                                 rcu_reader_reg++) {
 463                         if (!rcu_reader_reg->alloc) {
 464                                 rcu_reader_reg->alloc = 1;
 465                                 chunk->used += len;
 466                                 return rcu_reader_reg;
 467                         }
 468                 }
 469         }
 470
 471         if (!expand_done) {
 472                 expand_arena(arena);
 473                 expand_done = 1;
 474                 goto retry;
 475         }
 476
 477         return NULL;
 478 }
 479
 480 /* Called with signals off and mutex locked */
 481 static
 482 void add_thread(void)
 483 {
 484         struct rcu_reader *rcu_reader_reg;
 485         int ret;
 486
 487         rcu_reader_reg = arena_alloc(&registry_arena);
 488         if (!rcu_reader_reg)
 489                 abort();
 490         ret = pthread_setspecific(urcu_bp_key, rcu_reader_reg);
 491         if (ret)
 492                 abort();
 493
 494         /* Add to registry */
 495         rcu_reader_reg->tid = pthread_self();
 496         assert(rcu_reader_reg->ctr == 0);
 497         cds_list_add(&rcu_reader_reg->node, &registry);
 498         /*
 499          * Reader threads are pointing to the reader registry. This is
 500          * why its memory should never be relocated.
 501          */
 502         URCU_TLS(urcu_bp_reader) = rcu_reader_reg;
 503 }
 504
 505 /* Called with mutex locked */
 506 static
 507 void cleanup_thread(struct registry_chunk *chunk,
 508                 struct rcu_reader *rcu_reader_reg)
 509 {
 510         rcu_reader_reg->ctr = 0;
 511         cds_list_del(&rcu_reader_reg->node);
 512         rcu_reader_reg->tid = 0;
 513         rcu_reader_reg->alloc = 0;
 514         chunk->used -= sizeof(struct rcu_reader);
 515 }
 516
 517 static
 518 struct registry_chunk *find_chunk(struct rcu_reader *rcu_reader_reg)
 519 {
 520         struct registry_chunk *chunk;
 521
 522         cds_list_for_each_entry(chunk, &registry_arena.chunk_list, node) {
 523                 if (rcu_reader_reg < (struct rcu_reader *) &chunk->data[0])
 524                         continue;
 525                 if (rcu_reader_reg >= (struct rcu_reader *) &chunk->data[chunk->data_len])
 526                         continue;
 527                 return chunk;
 528         }
 529         return NULL;
 530 }
 531
 532 /* Called with signals off and mutex locked */
 533 static
 534 void remove_thread(struct rcu_reader *rcu_reader_reg)
 535 {
 536         cleanup_thread(find_chunk(rcu_reader_reg), rcu_reader_reg);
 537         URCU_TLS(urcu_bp_reader) = NULL;
 538 }
 539
 540 /* Disable signals, take mutex, add to registry */
 541 void urcu_bp_register(void)
 542 {
 543         sigset_t newmask, oldmask;
 544         int ret;
 545
 546         ret = sigfillset(&newmask);
 547         if (ret)
 548                 abort();
 549         ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
 550         if (ret)
 551                 abort();
 552
 553         /*
 554          * Check if a signal concurrently registered our thread since
 555          * the check in rcu_read_lock().
 556          */
 557         if (URCU_TLS(urcu_bp_reader))
 558                 goto end;
 559
 560         /*
 561          * Take care of early registration before urcu_bp constructor.
 562          */
 563         _urcu_bp_init();
 564
 565         mutex_lock(&rcu_registry_lock);
 566         add_thread();
 567         mutex_unlock(&rcu_registry_lock);
 568 end:
 569         ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 570         if (ret)
 571                 abort();
 572 }
 573 URCU_ATTR_ALIAS("urcu_bp_register") void rcu_bp_register();
 574
 575 void urcu_bp_register_thread(void)
 576 {
 577         if (caa_unlikely(!URCU_TLS(urcu_bp_reader)))
 578                 urcu_bp_register(); /* If not yet registered. */
 579 }
 580
 581 /* Disable signals, take mutex, remove from registry */
 582 static
 583 void urcu_bp_unregister(struct rcu_reader *rcu_reader_reg)
 584 {
 585         sigset_t newmask, oldmask;
 586         int ret;
 587
 588         ret = sigfillset(&newmask);
 589         if (ret)
 590                 abort();
 591         ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
 592         if (ret)
 593                 abort();
 594
 595         mutex_lock(&rcu_registry_lock);
 596         remove_thread(rcu_reader_reg);
 597         mutex_unlock(&rcu_registry_lock);
 598         ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 599         if (ret)
 600                 abort();
 601         urcu_bp_exit();
 602 }
 603
 604 /*
 605  * Remove thread from the registry when it exits, and flag it as
 606  * destroyed so garbage collection can take care of it.
 607  */
 608 static
 609 void urcu_bp_thread_exit_notifier(void *rcu_key)
 610 {
 611         urcu_bp_unregister(rcu_key);
 612 }
 613
 614 #ifdef CONFIG_RCU_FORCE_SYS_MEMBARRIER
 615 static
 616 void urcu_bp_sys_membarrier_status(bool available)
 617 {
 618         if (!available)
 619                 abort();
 620 }
 621 #else
 622 static
 623 void urcu_bp_sys_membarrier_status(bool available)
 624 {
 625         if (!available)
 626                 return;
 627         urcu_bp_has_sys_membarrier = 1;
 628 }
 629 #endif
 630
 631 static
 632 void urcu_bp_sys_membarrier_init(void)
 633 {
 634         bool available = false;
 635         int mask;
 636
 637         mask = membarrier(MEMBARRIER_CMD_QUERY, 0);
 638         if (mask >= 0) {
 639                 if (mask & MEMBARRIER_CMD_PRIVATE_EXPEDITED) {
 640                         if (membarrier(MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, 0))
 641                                 urcu_die(errno);
 642                         available = true;
 643                 }
 644         }
 645         urcu_bp_sys_membarrier_status(available);
 646 }
 647
 648 static
 649 void _urcu_bp_init(void)
 650 {
 651         mutex_lock(&init_lock);
 652         if (!urcu_bp_refcount++) {
 653                 int ret;
 654
 655                 ret = pthread_key_create(&urcu_bp_key,
 656                                 urcu_bp_thread_exit_notifier);
 657                 if (ret)
 658                         abort();
 659                 urcu_bp_sys_membarrier_init();
 660                 initialized = 1;
 661         }
 662         mutex_unlock(&init_lock);
 663 }
 664
 665 static
 666 void urcu_bp_exit(void)
 667 {
 668         mutex_lock(&init_lock);
 669         if (!--urcu_bp_refcount) {
 670                 struct registry_chunk *chunk, *tmp;
 671                 int ret;
 672
 673                 cds_list_for_each_entry_safe(chunk, tmp,
 674                                 &registry_arena.chunk_list, node) {
 675                         munmap((void *) chunk, chunk->data_len
 676                                         + sizeof(struct registry_chunk));
 677                 }
 678                 CDS_INIT_LIST_HEAD(&registry_arena.chunk_list);
 679                 ret = pthread_key_delete(urcu_bp_key);
 680                 if (ret)
 681                         abort();
 682         }
 683         mutex_unlock(&init_lock);
 684 }
 685
 686 static
 687 void urcu_bp_exit_destructor(void)
 688 {
 689         urcu_call_rcu_exit();
 690         urcu_bp_exit();
 691 }
 692
 693 /*
 694  * Holding the rcu_gp_lock and rcu_registry_lock across fork will make
 695  * sure we fork() don't race with a concurrent thread executing with
 696  * any of those locks held. This ensures that the registry and data
 697  * protected by rcu_gp_lock are in a coherent state in the child.
 698  */
 699 void urcu_bp_before_fork(void)
 700 {
 701         sigset_t newmask, oldmask;
 702         int ret;
 703
 704         ret = sigfillset(&newmask);
 705         assert(!ret);
 706         ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
 707         assert(!ret);
 708         mutex_lock(&rcu_gp_lock);
 709         mutex_lock(&rcu_registry_lock);
 710         saved_fork_signal_mask = oldmask;
 711 }
 712 URCU_ATTR_ALIAS("urcu_bp_before_fork") void rcu_bp_before_fork();
 713
 714 void urcu_bp_after_fork_parent(void)
 715 {
 716         sigset_t oldmask;
 717         int ret;
 718
 719         oldmask = saved_fork_signal_mask;
 720         mutex_unlock(&rcu_registry_lock);
 721         mutex_unlock(&rcu_gp_lock);
 722         ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 723         assert(!ret);
 724 }
 725 URCU_ATTR_ALIAS("urcu_bp_after_fork_parent")
 726 void rcu_bp_after_fork_parent(void);
 727
 728 /*
 729  * Prune all entries from registry except our own thread. Fits the Linux
 730  * fork behavior. Called with rcu_gp_lock and rcu_registry_lock held.
 731  */
 732 static
 733 void urcu_bp_prune_registry(void)
 734 {
 735         struct registry_chunk *chunk;
 736         struct urcu_bp_reader *rcu_reader_reg;
 737
 738         cds_list_for_each_entry(chunk, &registry_arena.chunk_list, node) {
 739                 for (rcu_reader_reg = (struct urcu_bp_reader *) &chunk->data[0];
 740                                 rcu_reader_reg < (struct urcu_bp_reader *) &chunk->data[chunk->data_len];
 741                                 rcu_reader_reg++) {
 742                         if (!rcu_reader_reg->alloc)
 743                                 continue;
 744                         if (rcu_reader_reg->tid == pthread_self())
 745                                 continue;
 746                         cleanup_thread(chunk, rcu_reader_reg);
 747                 }
 748         }
 749 }
 750
 751 void urcu_bp_after_fork_child(void)
 752 {
 753         sigset_t oldmask;
 754         int ret;
 755
 756         urcu_bp_prune_registry();
 757         oldmask = saved_fork_signal_mask;
 758         mutex_unlock(&rcu_registry_lock);
 759         mutex_unlock(&rcu_gp_lock);
 760         ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 761         assert(!ret);
 762 }
 763 URCU_ATTR_ALIAS("urcu_bp_after_fork_child")
 764 void rcu_bp_after_fork_child(void);
 765
 766 void *urcu_bp_dereference_sym(void *p)
 767 {
 768         return _rcu_dereference(p);
 769 }
 770 URCU_ATTR_ALIAS("urcu_bp_dereference_sym")
 771 void *rcu_dereference_sym_bp();
 772
 773 void *urcu_bp_set_pointer_sym(void **p, void *v)
 774 {
 775         cmm_wmb();
 776         uatomic_set(p, v);
 777         return v;
 778 }
 779 URCU_ATTR_ALIAS("urcu_bp_set_pointer_sym")
 780 void *rcu_set_pointer_sym_bp();
 781
 782 void *urcu_bp_xchg_pointer_sym(void **p, void *v)
 783 {
 784         cmm_wmb();
 785         return uatomic_xchg(p, v);
 786 }
 787 URCU_ATTR_ALIAS("urcu_bp_xchg_pointer_sym")
 788 void *rcu_xchg_pointer_sym_bp();
 789
 790 void *urcu_bp_cmpxchg_pointer_sym(void **p, void *old, void *_new)
 791 {
 792         cmm_wmb();
 793         return uatomic_cmpxchg(p, old, _new);
 794 }
 795 URCU_ATTR_ALIAS("urcu_bp_cmpxchg_pointer_sym")
 796 void *rcu_cmpxchg_pointer_sym_bp();
 797
 798 DEFINE_RCU_FLAVOR(rcu_flavor);
 799 DEFINE_RCU_FLAVOR_ALIAS(rcu_flavor, alias_rcu_flavor);
 800
 801 #include "urcu-call-rcu-impl.h"
 802 #include "urcu-defer-impl.h"