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
mremap_wrapper(void * old_address,size_t old_size,size_t new_size,int flags)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
mremap_wrapper(void * old_address,size_t old_size,size_t new_size,int flags)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 __attribute__((destructor)) urcu_bp_exit(void);
124
125 #ifndef CONFIG_RCU_FORCE_SYS_MEMBARRIER
126 int urcu_bp_has_sys_membarrier;
127 #endif
128
129 /*
130 * rcu_gp_lock ensures mutual exclusion between threads calling
131 * synchronize_rcu().
132 */
133 static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
134 /*
135 * rcu_registry_lock ensures mutual exclusion between threads
136 * registering and unregistering themselves to/from the registry, and
137 * with threads reading that registry from synchronize_rcu(). However,
138 * this lock is not held all the way through the completion of awaiting
139 * for the grace period. It is sporadically released between iterations
140 * on the registry.
141 * rcu_registry_lock may nest inside rcu_gp_lock.
142 */
143 static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER;
144
145 static pthread_mutex_t init_lock = PTHREAD_MUTEX_INITIALIZER;
146 static int initialized;
147
148 static pthread_key_t urcu_bp_key;
149
150 struct urcu_bp_gp urcu_bp_gp = { .ctr = URCU_BP_GP_COUNT };
151
152 /*
153 * Pointer to registry elements. Written to only by each individual reader. Read
154 * by both the reader and the writers.
155 */
156 DEFINE_URCU_TLS(struct urcu_bp_reader *, urcu_bp_reader);
157
158 static CDS_LIST_HEAD(registry);
159
160 struct registry_chunk {
161 size_t data_len; /* data length */
162 size_t used; /* amount of data used */
163 struct cds_list_head node; /* chunk_list node */
164 char data[];
165 };
166
167 struct registry_arena {
168 struct cds_list_head chunk_list;
169 };
170
171 static struct registry_arena registry_arena = {
172 .chunk_list = CDS_LIST_HEAD_INIT(registry_arena.chunk_list),
173 };
174
175 /* Saved fork signal mask, protected by rcu_gp_lock */
176 static sigset_t saved_fork_signal_mask;
177
mutex_lock(pthread_mutex_t * mutex)178 static void mutex_lock(pthread_mutex_t *mutex)
179 {
180 int ret;
181
182 #ifndef DISTRUST_SIGNALS_EXTREME
183 ret = pthread_mutex_lock(mutex);
184 if (ret)
185 urcu_die(ret);
186 #else /* #ifndef DISTRUST_SIGNALS_EXTREME */
187 while ((ret = pthread_mutex_trylock(mutex)) != 0) {
188 if (ret != EBUSY && ret != EINTR)
189 urcu_die(ret);
190 poll(NULL,0,10);
191 }
192 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
193 }
194
mutex_unlock(pthread_mutex_t * mutex)195 static void mutex_unlock(pthread_mutex_t *mutex)
196 {
197 int ret;
198
199 ret = pthread_mutex_unlock(mutex);
200 if (ret)
201 urcu_die(ret);
202 }
203
smp_mb_master(void)204 static void smp_mb_master(void)
205 {
206 if (caa_likely(urcu_bp_has_sys_membarrier)) {
207 if (membarrier(MEMBARRIER_CMD_PRIVATE_EXPEDITED, 0))
208 urcu_die(errno);
209 } else {
210 cmm_smp_mb();
211 }
212 }
213
214 /*
215 * Always called with rcu_registry lock held. Releases this lock between
216 * iterations and grabs it again. Holds the lock when it returns.
217 */
wait_for_readers(struct cds_list_head * input_readers,struct cds_list_head * cur_snap_readers,struct cds_list_head * qsreaders)218 static void wait_for_readers(struct cds_list_head *input_readers,
219 struct cds_list_head *cur_snap_readers,
220 struct cds_list_head *qsreaders)
221 {
222 unsigned int wait_loops = 0;
223 struct urcu_bp_reader *index, *tmp;
224
225 /*
226 * Wait for each thread URCU_TLS(urcu_bp_reader).ctr to either
227 * indicate quiescence (not nested), or observe the current
228 * rcu_gp.ctr value.
229 */
230 for (;;) {
231 if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS)
232 wait_loops++;
233
234 cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
235 switch (urcu_bp_reader_state(&index->ctr)) {
236 case URCU_BP_READER_ACTIVE_CURRENT:
237 if (cur_snap_readers) {
238 cds_list_move(&index->node,
239 cur_snap_readers);
240 break;
241 }
242 /* Fall-through */
243 case URCU_BP_READER_INACTIVE:
244 cds_list_move(&index->node, qsreaders);
245 break;
246 case URCU_BP_READER_ACTIVE_OLD:
247 /*
248 * Old snapshot. Leaving node in
249 * input_readers will make us busy-loop
250 * until the snapshot becomes current or
251 * the reader becomes inactive.
252 */
253 break;
254 }
255 }
256
257 if (cds_list_empty(input_readers)) {
258 break;
259 } else {
260 /* Temporarily unlock the registry lock. */
261 mutex_unlock(&rcu_registry_lock);
262 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS)
263 (void) poll(NULL, 0, RCU_SLEEP_DELAY_MS);
264 else
265 caa_cpu_relax();
266 /* Re-lock the registry lock before the next loop. */
267 mutex_lock(&rcu_registry_lock);
268 }
269 }
270 }
271
urcu_bp_synchronize_rcu(void)272 void urcu_bp_synchronize_rcu(void)
273 {
274 CDS_LIST_HEAD(cur_snap_readers);
275 CDS_LIST_HEAD(qsreaders);
276 sigset_t newmask, oldmask;
277 int ret;
278
279 ret = sigfillset(&newmask);
280 assert(!ret);
281 ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
282 assert(!ret);
283
284 mutex_lock(&rcu_gp_lock);
285
286 mutex_lock(&rcu_registry_lock);
287
288 if (cds_list_empty(®istry))
289 goto out;
290
291 /* All threads should read qparity before accessing data structure
292 * where new ptr points to. */
293 /* Write new ptr before changing the qparity */
294 smp_mb_master();
295
296 /*
297 * Wait for readers to observe original parity or be quiescent.
298 * wait_for_readers() can release and grab again rcu_registry_lock
299 * interally.
300 */
301 wait_for_readers(®istry, &cur_snap_readers, &qsreaders);
302
303 /*
304 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
305 * model easier to understand. It does not have a big performance impact
306 * anyway, given this is the write-side.
307 */
308 cmm_smp_mb();
309
310 /* Switch parity: 0 -> 1, 1 -> 0 */
311 CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ URCU_BP_GP_CTR_PHASE);
312
313 /*
314 * Must commit qparity update to memory before waiting for other parity
315 * quiescent state. Failure to do so could result in the writer waiting
316 * forever while new readers are always accessing data (no progress).
317 * Ensured by CMM_STORE_SHARED and CMM_LOAD_SHARED.
318 */
319
320 /*
321 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
322 * model easier to understand. It does not have a big performance impact
323 * anyway, given this is the write-side.
324 */
325 cmm_smp_mb();
326
327 /*
328 * Wait for readers to observe new parity or be quiescent.
329 * wait_for_readers() can release and grab again rcu_registry_lock
330 * interally.
331 */
332 wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
333
334 /*
335 * Put quiescent reader list back into registry.
336 */
337 cds_list_splice(&qsreaders, ®istry);
338
339 /*
340 * Finish waiting for reader threads before letting the old ptr being
341 * freed.
342 */
343 smp_mb_master();
344 out:
345 mutex_unlock(&rcu_registry_lock);
346 mutex_unlock(&rcu_gp_lock);
347 ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
348 assert(!ret);
349 }
350
351 /*
352 * library wrappers to be used by non-LGPL compatible source code.
353 */
354
urcu_bp_read_lock(void)355 void urcu_bp_read_lock(void)
356 {
357 _urcu_bp_read_lock();
358 }
359
urcu_bp_read_unlock(void)360 void urcu_bp_read_unlock(void)
361 {
362 _urcu_bp_read_unlock();
363 }
364
urcu_bp_read_ongoing(void)365 int urcu_bp_read_ongoing(void)
366 {
367 return _urcu_bp_read_ongoing();
368 }
369
370 /*
371 * Only grow for now. If empty, allocate a ARENA_INIT_ALLOC sized chunk.
372 * Else, try expanding the last chunk. If this fails, allocate a new
373 * chunk twice as big as the last chunk.
374 * Memory used by chunks _never_ moves. A chunk could theoretically be
375 * freed when all "used" slots are released, but we don't do it at this
376 * point.
377 */
378 static
expand_arena(struct registry_arena * arena)379 void expand_arena(struct registry_arena *arena)
380 {
381 struct registry_chunk *new_chunk, *last_chunk;
382 size_t old_chunk_len, new_chunk_len;
383
384 /* No chunk. */
385 if (cds_list_empty(&arena->chunk_list)) {
386 assert(ARENA_INIT_ALLOC >=
387 sizeof(struct registry_chunk)
388 + sizeof(struct rcu_reader));
389 new_chunk_len = ARENA_INIT_ALLOC;
390 new_chunk = (struct registry_chunk *) mmap(NULL,
391 new_chunk_len,
392 PROT_READ | PROT_WRITE,
393 MAP_ANONYMOUS | MAP_PRIVATE,
394 -1, 0);
395 if (new_chunk == MAP_FAILED)
396 abort();
397 memset(new_chunk, 0, new_chunk_len);
398 new_chunk->data_len =
399 new_chunk_len - sizeof(struct registry_chunk);
400 cds_list_add_tail(&new_chunk->node, &arena->chunk_list);
401 return; /* We're done. */
402 }
403
404 /* Try expanding last chunk. */
405 last_chunk = cds_list_entry(arena->chunk_list.prev,
406 struct registry_chunk, node);
407 old_chunk_len =
408 last_chunk->data_len + sizeof(struct registry_chunk);
409 new_chunk_len = old_chunk_len << 1;
410
411 /* Don't allow memory mapping to move, just expand. */
412 new_chunk = mremap_wrapper(last_chunk, old_chunk_len,
413 new_chunk_len, 0);
414 if (new_chunk != MAP_FAILED) {
415 /* Should not have moved. */
416 assert(new_chunk == last_chunk);
417 memset((char *) last_chunk + old_chunk_len, 0,
418 new_chunk_len - old_chunk_len);
419 last_chunk->data_len =
420 new_chunk_len - sizeof(struct registry_chunk);
421 return; /* We're done. */
422 }
423
424 /* Remap did not succeed, we need to add a new chunk. */
425 new_chunk = (struct registry_chunk *) mmap(NULL,
426 new_chunk_len,
427 PROT_READ | PROT_WRITE,
428 MAP_ANONYMOUS | MAP_PRIVATE,
429 -1, 0);
430 if (new_chunk == MAP_FAILED)
431 abort();
432 memset(new_chunk, 0, new_chunk_len);
433 new_chunk->data_len =
434 new_chunk_len - sizeof(struct registry_chunk);
435 cds_list_add_tail(&new_chunk->node, &arena->chunk_list);
436 }
437
438 static
arena_alloc(struct registry_arena * arena)439 struct rcu_reader *arena_alloc(struct registry_arena *arena)
440 {
441 struct registry_chunk *chunk;
442 struct rcu_reader *rcu_reader_reg;
443 int expand_done = 0; /* Only allow to expand once per alloc */
444 size_t len = sizeof(struct rcu_reader);
445
446 retry:
447 cds_list_for_each_entry(chunk, &arena->chunk_list, node) {
448 if (chunk->data_len - chunk->used < len)
449 continue;
450 /* Find spot */
451 for (rcu_reader_reg = (struct rcu_reader *) &chunk->data[0];
452 rcu_reader_reg < (struct rcu_reader *) &chunk->data[chunk->data_len];
453 rcu_reader_reg++) {
454 if (!rcu_reader_reg->alloc) {
455 rcu_reader_reg->alloc = 1;
456 chunk->used += len;
457 return rcu_reader_reg;
458 }
459 }
460 }
461
462 if (!expand_done) {
463 expand_arena(arena);
464 expand_done = 1;
465 goto retry;
466 }
467
468 return NULL;
469 }
470
471 /* Called with signals off and mutex locked */
472 static
add_thread(void)473 void add_thread(void)
474 {
475 struct rcu_reader *rcu_reader_reg;
476 int ret;
477
478 rcu_reader_reg = arena_alloc(®istry_arena);
479 if (!rcu_reader_reg)
480 abort();
481 ret = pthread_setspecific(urcu_bp_key, rcu_reader_reg);
482 if (ret)
483 abort();
484
485 /* Add to registry */
486 rcu_reader_reg->tid = pthread_self();
487 assert(rcu_reader_reg->ctr == 0);
488 cds_list_add(&rcu_reader_reg->node, ®istry);
489 /*
490 * Reader threads are pointing to the reader registry. This is
491 * why its memory should never be relocated.
492 */
493 URCU_TLS(urcu_bp_reader) = rcu_reader_reg;
494 }
495
496 /* Called with mutex locked */
497 static
cleanup_thread(struct registry_chunk * chunk,struct rcu_reader * rcu_reader_reg)498 void cleanup_thread(struct registry_chunk *chunk,
499 struct rcu_reader *rcu_reader_reg)
500 {
501 rcu_reader_reg->ctr = 0;
502 cds_list_del(&rcu_reader_reg->node);
503 rcu_reader_reg->tid = 0;
504 rcu_reader_reg->alloc = 0;
505 chunk->used -= sizeof(struct rcu_reader);
506 }
507
508 static
find_chunk(struct rcu_reader * rcu_reader_reg)509 struct registry_chunk *find_chunk(struct rcu_reader *rcu_reader_reg)
510 {
511 struct registry_chunk *chunk;
512
513 cds_list_for_each_entry(chunk, ®istry_arena.chunk_list, node) {
514 if (rcu_reader_reg < (struct rcu_reader *) &chunk->data[0])
515 continue;
516 if (rcu_reader_reg >= (struct rcu_reader *) &chunk->data[chunk->data_len])
517 continue;
518 return chunk;
519 }
520 return NULL;
521 }
522
523 /* Called with signals off and mutex locked */
524 static
remove_thread(struct rcu_reader * rcu_reader_reg)525 void remove_thread(struct rcu_reader *rcu_reader_reg)
526 {
527 cleanup_thread(find_chunk(rcu_reader_reg), rcu_reader_reg);
528 URCU_TLS(urcu_bp_reader) = NULL;
529 }
530
531 /* Disable signals, take mutex, add to registry */
urcu_bp_register(void)532 void urcu_bp_register(void)
533 {
534 sigset_t newmask, oldmask;
535 int ret;
536
537 ret = sigfillset(&newmask);
538 if (ret)
539 abort();
540 ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
541 if (ret)
542 abort();
543
544 /*
545 * Check if a signal concurrently registered our thread since
546 * the check in rcu_read_lock().
547 */
548 if (URCU_TLS(urcu_bp_reader))
549 goto end;
550
551 /*
552 * Take care of early registration before urcu_bp constructor.
553 */
554 _urcu_bp_init();
555
556 mutex_lock(&rcu_registry_lock);
557 add_thread();
558 mutex_unlock(&rcu_registry_lock);
559 end:
560 ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
561 if (ret)
562 abort();
563 }
564
urcu_bp_register_thread(void)565 void urcu_bp_register_thread(void)
566 {
567 if (caa_unlikely(!URCU_TLS(urcu_bp_reader)))
568 urcu_bp_register(); /* If not yet registered. */
569 }
570
571 /* Disable signals, take mutex, remove from registry */
572 static
urcu_bp_unregister(struct rcu_reader * rcu_reader_reg)573 void urcu_bp_unregister(struct rcu_reader *rcu_reader_reg)
574 {
575 sigset_t newmask, oldmask;
576 int ret;
577
578 ret = sigfillset(&newmask);
579 if (ret)
580 abort();
581 ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
582 if (ret)
583 abort();
584
585 mutex_lock(&rcu_registry_lock);
586 remove_thread(rcu_reader_reg);
587 mutex_unlock(&rcu_registry_lock);
588 ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
589 if (ret)
590 abort();
591 urcu_bp_exit();
592 }
593
594 /*
595 * Remove thread from the registry when it exits, and flag it as
596 * destroyed so garbage collection can take care of it.
597 */
598 static
urcu_bp_thread_exit_notifier(void * rcu_key)599 void urcu_bp_thread_exit_notifier(void *rcu_key)
600 {
601 urcu_bp_unregister(rcu_key);
602 }
603
604 #ifdef CONFIG_RCU_FORCE_SYS_MEMBARRIER
605 static
urcu_bp_sys_membarrier_status(bool available)606 void urcu_bp_sys_membarrier_status(bool available)
607 {
608 if (!available)
609 abort();
610 }
611 #else
612 static
urcu_bp_sys_membarrier_status(bool available)613 void urcu_bp_sys_membarrier_status(bool available)
614 {
615 if (!available)
616 return;
617 urcu_bp_has_sys_membarrier = 1;
618 }
619 #endif
620
621 static
urcu_bp_sys_membarrier_init(void)622 void urcu_bp_sys_membarrier_init(void)
623 {
624 bool available = false;
625 int mask;
626
627 mask = membarrier(MEMBARRIER_CMD_QUERY, 0);
628 if (mask >= 0) {
629 if (mask & MEMBARRIER_CMD_PRIVATE_EXPEDITED) {
630 if (membarrier(MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, 0))
631 urcu_die(errno);
632 available = true;
633 }
634 }
635 urcu_bp_sys_membarrier_status(available);
636 }
637
638 static
_urcu_bp_init(void)639 void _urcu_bp_init(void)
640 {
641 mutex_lock(&init_lock);
642 if (!urcu_bp_refcount++) {
643 int ret;
644
645 ret = pthread_key_create(&urcu_bp_key,
646 urcu_bp_thread_exit_notifier);
647 if (ret)
648 abort();
649 urcu_bp_sys_membarrier_init();
650 initialized = 1;
651 }
652 mutex_unlock(&init_lock);
653 }
654
655 static
urcu_bp_exit(void)656 void urcu_bp_exit(void)
657 {
658 mutex_lock(&init_lock);
659 if (!--urcu_bp_refcount) {
660 struct registry_chunk *chunk, *tmp;
661 int ret;
662
663 cds_list_for_each_entry_safe(chunk, tmp,
664 ®istry_arena.chunk_list, node) {
665 munmap((void *) chunk, chunk->data_len
666 + sizeof(struct registry_chunk));
667 }
668 CDS_INIT_LIST_HEAD(®istry_arena.chunk_list);
669 ret = pthread_key_delete(urcu_bp_key);
670 if (ret)
671 abort();
672 }
673 mutex_unlock(&init_lock);
674 }
675
676 /*
677 * Holding the rcu_gp_lock and rcu_registry_lock across fork will make
678 * sure we fork() don't race with a concurrent thread executing with
679 * any of those locks held. This ensures that the registry and data
680 * protected by rcu_gp_lock are in a coherent state in the child.
681 */
urcu_bp_before_fork(void)682 void urcu_bp_before_fork(void)
683 {
684 sigset_t newmask, oldmask;
685 int ret;
686
687 ret = sigfillset(&newmask);
688 assert(!ret);
689 ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
690 assert(!ret);
691 mutex_lock(&rcu_gp_lock);
692 mutex_lock(&rcu_registry_lock);
693 saved_fork_signal_mask = oldmask;
694 }
695
urcu_bp_after_fork_parent(void)696 void urcu_bp_after_fork_parent(void)
697 {
698 sigset_t oldmask;
699 int ret;
700
701 oldmask = saved_fork_signal_mask;
702 mutex_unlock(&rcu_registry_lock);
703 mutex_unlock(&rcu_gp_lock);
704 ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
705 assert(!ret);
706 }
707
708 /*
709 * Prune all entries from registry except our own thread. Fits the Linux
710 * fork behavior. Called with rcu_gp_lock and rcu_registry_lock held.
711 */
712 static
urcu_bp_prune_registry(void)713 void urcu_bp_prune_registry(void)
714 {
715 struct registry_chunk *chunk;
716 struct urcu_bp_reader *rcu_reader_reg;
717
718 cds_list_for_each_entry(chunk, ®istry_arena.chunk_list, node) {
719 for (rcu_reader_reg = (struct urcu_bp_reader *) &chunk->data[0];
720 rcu_reader_reg < (struct urcu_bp_reader *) &chunk->data[chunk->data_len];
721 rcu_reader_reg++) {
722 if (!rcu_reader_reg->alloc)
723 continue;
724 if (rcu_reader_reg->tid == pthread_self())
725 continue;
726 cleanup_thread(chunk, rcu_reader_reg);
727 }
728 }
729 }
730
urcu_bp_after_fork_child(void)731 void urcu_bp_after_fork_child(void)
732 {
733 sigset_t oldmask;
734 int ret;
735
736 urcu_bp_prune_registry();
737 oldmask = saved_fork_signal_mask;
738 mutex_unlock(&rcu_registry_lock);
739 mutex_unlock(&rcu_gp_lock);
740 ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
741 assert(!ret);
742 }
743
urcu_bp_dereference_sym(void * p)744 void *urcu_bp_dereference_sym(void *p)
745 {
746 return _rcu_dereference(p);
747 }
748
urcu_bp_set_pointer_sym(void ** p,void * v)749 void *urcu_bp_set_pointer_sym(void **p, void *v)
750 {
751 cmm_wmb();
752 uatomic_set(p, v);
753 return v;
754 }
755
urcu_bp_xchg_pointer_sym(void ** p,void * v)756 void *urcu_bp_xchg_pointer_sym(void **p, void *v)
757 {
758 cmm_wmb();
759 return uatomic_xchg(p, v);
760 }
761
urcu_bp_cmpxchg_pointer_sym(void ** p,void * old,void * _new)762 void *urcu_bp_cmpxchg_pointer_sym(void **p, void *old, void *_new)
763 {
764 cmm_wmb();
765 return uatomic_cmpxchg(p, old, _new);
766 }
767
768 DEFINE_RCU_FLAVOR(rcu_flavor);
769
770 #include "urcu-call-rcu-impl.h"
771 #include "urcu-defer-impl.h"
772