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