urcu call_rcu: Use RCU read-side protection for per-cpu call_rcu data
[urcu.git] / urcu-call-rcu-impl.h
1 /*
2 * urcu-call-rcu.c
3 *
4 * Userspace RCU library - batch memory reclamation with kernel API
5 *
6 * Copyright (c) 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com>
7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 #define _GNU_SOURCE
24 #include <stdio.h>
25 #include <pthread.h>
26 #include <signal.h>
27 #include <assert.h>
28 #include <stdlib.h>
29 #include <stdint.h>
30 #include <string.h>
31 #include <errno.h>
32 #include <poll.h>
33 #include <sys/time.h>
34 #include <unistd.h>
35 #include <sched.h>
36
37 #include "config.h"
38 #include "urcu/wfqueue.h"
39 #include "urcu-call-rcu.h"
40 #include "urcu-pointer.h"
41 #include "urcu/list.h"
42 #include "urcu/futex.h"
43
44 /* Data structure that identifies a call_rcu thread. */
45
46 struct call_rcu_data {
47 struct cds_wfq_queue cbs;
48 unsigned long flags;
49 int32_t futex;
50 unsigned long qlen; /* maintained for debugging. */
51 pthread_t tid;
52 int cpu_affinity;
53 struct cds_list_head list;
54 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
55
56 /*
57 * List of all call_rcu_data structures to keep valgrind happy.
58 * Protected by call_rcu_mutex.
59 */
60
61 CDS_LIST_HEAD(call_rcu_data_list);
62
63 /* Link a thread using call_rcu() to its call_rcu thread. */
64
65 static __thread struct call_rcu_data *thread_call_rcu_data;
66
67 /* Guard call_rcu thread creation. */
68
69 static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
70
71 /* If a given thread does not have its own call_rcu thread, this is default. */
72
73 static struct call_rcu_data *default_call_rcu_data;
74
75 /*
76 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
77 * available, then we can have call_rcu threads assigned to individual
78 * CPUs rather than only to specific threads.
79 */
80
81 #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
82
83 /*
84 * Pointer to array of pointers to per-CPU call_rcu_data structures
85 * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an
86 * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a
87 * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer
88 * without mutex. The call_rcu_mutex protects updates.
89 */
90
91 static struct call_rcu_data **per_cpu_call_rcu_data;
92 static long maxcpus;
93
94 static void maxcpus_reset(void)
95 {
96 maxcpus = 0;
97 }
98
99 /* Allocate the array if it has not already been allocated. */
100
101 static void alloc_cpu_call_rcu_data(void)
102 {
103 struct call_rcu_data **p;
104 static int warned = 0;
105
106 if (maxcpus != 0)
107 return;
108 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
109 if (maxcpus <= 0) {
110 return;
111 }
112 p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data));
113 if (p != NULL) {
114 memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data));
115 rcu_set_pointer(&per_cpu_call_rcu_data, p);
116 } else {
117 if (!warned) {
118 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
119 }
120 warned = 1;
121 }
122 }
123
124 #else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
125
126 /*
127 * per_cpu_call_rcu_data should be constant, but some functions below, used both
128 * for cases where cpu number is available and not available, assume it it not
129 * constant.
130 */
131 static struct call_rcu_data **per_cpu_call_rcu_data = NULL;
132 static const long maxcpus = -1;
133
134 static void maxcpus_reset(void)
135 {
136 }
137
138 static void alloc_cpu_call_rcu_data(void)
139 {
140 }
141
142 static int sched_getcpu(void)
143 {
144 return -1;
145 }
146
147 #endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
148
149 /* Acquire the specified pthread mutex. */
150
151 static void call_rcu_lock(pthread_mutex_t *pmp)
152 {
153 if (pthread_mutex_lock(pmp) != 0) {
154 perror("pthread_mutex_lock");
155 exit(-1);
156 }
157 }
158
159 /* Release the specified pthread mutex. */
160
161 static void call_rcu_unlock(pthread_mutex_t *pmp)
162 {
163 if (pthread_mutex_unlock(pmp) != 0) {
164 perror("pthread_mutex_unlock");
165 exit(-1);
166 }
167 }
168
169 #if HAVE_SCHED_SETAFFINITY
170 static
171 int set_thread_cpu_affinity(struct call_rcu_data *crdp)
172 {
173 cpu_set_t mask;
174
175 if (crdp->cpu_affinity < 0)
176 return 0;
177
178 CPU_ZERO(&mask);
179 CPU_SET(crdp->cpu_affinity, &mask);
180 #if SCHED_SETAFFINITY_ARGS == 2
181 return sched_setaffinity(0, &mask);
182 #else
183 return sched_setaffinity(0, sizeof(mask), &mask);
184 #endif
185 }
186 #else
187 static
188 int set_thread_cpu_affinity(struct call_rcu_data *crdp)
189 {
190 return 0;
191 }
192 #endif
193
194 static void call_rcu_wait(struct call_rcu_data *crdp)
195 {
196 /* Read call_rcu list before read futex */
197 cmm_smp_mb();
198 if (uatomic_read(&crdp->futex) == -1)
199 futex_async(&crdp->futex, FUTEX_WAIT, -1,
200 NULL, NULL, 0);
201 }
202
203 static void call_rcu_wake_up(struct call_rcu_data *crdp)
204 {
205 /* Write to call_rcu list before reading/writing futex */
206 cmm_smp_mb();
207 if (unlikely(uatomic_read(&crdp->futex) == -1)) {
208 uatomic_set(&crdp->futex, 0);
209 futex_async(&crdp->futex, FUTEX_WAKE, 1,
210 NULL, NULL, 0);
211 }
212 }
213
214 /* This is the code run by each call_rcu thread. */
215
216 static void *call_rcu_thread(void *arg)
217 {
218 unsigned long cbcount;
219 struct cds_wfq_node *cbs;
220 struct cds_wfq_node **cbs_tail;
221 struct call_rcu_data *crdp = (struct call_rcu_data *)arg;
222 struct rcu_head *rhp;
223 int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT);
224
225 if (set_thread_cpu_affinity(crdp) != 0) {
226 perror("pthread_setaffinity_np");
227 exit(-1);
228 }
229
230 /*
231 * If callbacks take a read-side lock, we need to be registered.
232 */
233 rcu_register_thread();
234
235 thread_call_rcu_data = crdp;
236 if (!rt) {
237 uatomic_dec(&crdp->futex);
238 /* Decrement futex before reading call_rcu list */
239 cmm_smp_mb();
240 }
241 for (;;) {
242 if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) {
243 while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL)
244 poll(NULL, 0, 1);
245 _CMM_STORE_SHARED(crdp->cbs.head, NULL);
246 cbs_tail = (struct cds_wfq_node **)
247 uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head);
248 synchronize_rcu();
249 cbcount = 0;
250 do {
251 while (cbs->next == NULL &&
252 &cbs->next != cbs_tail)
253 poll(NULL, 0, 1);
254 if (cbs == &crdp->cbs.dummy) {
255 cbs = cbs->next;
256 continue;
257 }
258 rhp = (struct rcu_head *)cbs;
259 cbs = cbs->next;
260 rhp->func(rhp);
261 cbcount++;
262 } while (cbs != NULL);
263 uatomic_sub(&crdp->qlen, cbcount);
264 }
265 if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP)
266 break;
267 rcu_thread_offline();
268 if (!rt) {
269 if (&crdp->cbs.head
270 == _CMM_LOAD_SHARED(crdp->cbs.tail)) {
271 call_rcu_wait(crdp);
272 poll(NULL, 0, 10);
273 uatomic_dec(&crdp->futex);
274 /*
275 * Decrement futex before reading
276 * call_rcu list.
277 */
278 cmm_smp_mb();
279 } else {
280 poll(NULL, 0, 10);
281 }
282 } else {
283 poll(NULL, 0, 10);
284 }
285 rcu_thread_online();
286 }
287 if (!rt) {
288 /*
289 * Read call_rcu list before write futex.
290 */
291 cmm_smp_mb();
292 uatomic_set(&crdp->futex, 0);
293 }
294 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED);
295 rcu_unregister_thread();
296 return NULL;
297 }
298
299 /*
300 * Create both a call_rcu thread and the corresponding call_rcu_data
301 * structure, linking the structure in as specified. Caller must hold
302 * call_rcu_mutex.
303 */
304
305 static void call_rcu_data_init(struct call_rcu_data **crdpp,
306 unsigned long flags,
307 int cpu_affinity)
308 {
309 struct call_rcu_data *crdp;
310
311 crdp = malloc(sizeof(*crdp));
312 if (crdp == NULL) {
313 fprintf(stderr, "Out of memory.\n");
314 exit(-1);
315 }
316 memset(crdp, '\0', sizeof(*crdp));
317 cds_wfq_init(&crdp->cbs);
318 crdp->qlen = 0;
319 crdp->futex = 0;
320 crdp->flags = flags;
321 cds_list_add(&crdp->list, &call_rcu_data_list);
322 crdp->cpu_affinity = cpu_affinity;
323 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
324 *crdpp = crdp;
325 if (pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp) != 0) {
326 perror("pthread_create");
327 exit(-1);
328 }
329 }
330
331 /*
332 * Return a pointer to the call_rcu_data structure for the specified
333 * CPU, returning NULL if there is none. We cannot automatically
334 * created it because the platform we are running on might not define
335 * sched_getcpu().
336 *
337 * The call to this function and use of the returned call_rcu_data
338 * should be protected by RCU read-side lock.
339 */
340
341 struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
342 {
343 static int warned = 0;
344 struct call_rcu_data **pcpu_crdp;
345
346 pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data);
347 if (pcpu_crdp == NULL)
348 return NULL;
349 if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) {
350 fprintf(stderr, "[error] liburcu: get CPU # out of range\n");
351 warned = 1;
352 }
353 if (cpu < 0 || maxcpus <= cpu)
354 return NULL;
355 return rcu_dereference(pcpu_crdp[cpu]);
356 }
357
358 /*
359 * Return the tid corresponding to the call_rcu thread whose
360 * call_rcu_data structure is specified.
361 */
362
363 pthread_t get_call_rcu_thread(struct call_rcu_data *crdp)
364 {
365 return crdp->tid;
366 }
367
368 /*
369 * Create a call_rcu_data structure (with thread) and return a pointer.
370 */
371
372 static struct call_rcu_data *__create_call_rcu_data(unsigned long flags,
373 int cpu_affinity)
374 {
375 struct call_rcu_data *crdp;
376
377 call_rcu_data_init(&crdp, flags, cpu_affinity);
378 return crdp;
379 }
380
381 struct call_rcu_data *create_call_rcu_data(unsigned long flags,
382 int cpu_affinity)
383 {
384 struct call_rcu_data *crdp;
385
386 call_rcu_lock(&call_rcu_mutex);
387 crdp = __create_call_rcu_data(flags, cpu_affinity);
388 call_rcu_unlock(&call_rcu_mutex);
389 return crdp;
390 }
391
392 /*
393 * Set the specified CPU to use the specified call_rcu_data structure.
394 *
395 * Use NULL to remove a CPU's call_rcu_data structure, but it is
396 * the caller's responsibility to dispose of the removed structure.
397 * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
398 * (prior to NULLing it out, of course).
399 */
400
401 int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
402 {
403 static int warned = 0;
404
405 call_rcu_lock(&call_rcu_mutex);
406 alloc_cpu_call_rcu_data();
407 if (cpu < 0 || maxcpus <= cpu) {
408 if (!warned) {
409 fprintf(stderr, "[error] liburcu: set CPU # out of range\n");
410 warned = 1;
411 }
412 call_rcu_unlock(&call_rcu_mutex);
413 errno = EINVAL;
414 return -EINVAL;
415 }
416
417 if (per_cpu_call_rcu_data == NULL) {
418 call_rcu_unlock(&call_rcu_mutex);
419 errno = ENOMEM;
420 return -ENOMEM;
421 }
422
423 if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) {
424 call_rcu_unlock(&call_rcu_mutex);
425 errno = EEXIST;
426 return -EEXIST;
427 }
428
429 rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp);
430 call_rcu_unlock(&call_rcu_mutex);
431 return 0;
432 }
433
434 /*
435 * Return a pointer to the default call_rcu_data structure, creating
436 * one if need be. Because we never free call_rcu_data structures,
437 * we don't need to be in an RCU read-side critical section.
438 */
439
440 struct call_rcu_data *get_default_call_rcu_data(void)
441 {
442 if (default_call_rcu_data != NULL)
443 return rcu_dereference(default_call_rcu_data);
444 call_rcu_lock(&call_rcu_mutex);
445 if (default_call_rcu_data != NULL) {
446 call_rcu_unlock(&call_rcu_mutex);
447 return default_call_rcu_data;
448 }
449 call_rcu_data_init(&default_call_rcu_data, 0, -1);
450 call_rcu_unlock(&call_rcu_mutex);
451 return default_call_rcu_data;
452 }
453
454 /*
455 * Return the call_rcu_data structure that applies to the currently
456 * running thread. Any call_rcu_data structure assigned specifically
457 * to this thread has first priority, followed by any call_rcu_data
458 * structure assigned to the CPU on which the thread is running,
459 * followed by the default call_rcu_data structure. If there is not
460 * yet a default call_rcu_data structure, one will be created.
461 *
462 * Calls to this function and use of the returned call_rcu_data should
463 * be protected by RCU read-side lock.
464 */
465 struct call_rcu_data *get_call_rcu_data(void)
466 {
467 struct call_rcu_data *crd;
468
469 if (thread_call_rcu_data != NULL)
470 return thread_call_rcu_data;
471
472 if (maxcpus > 0) {
473 crd = get_cpu_call_rcu_data(sched_getcpu());
474 if (crd)
475 return crd;
476 }
477
478 return get_default_call_rcu_data();
479 }
480
481 /*
482 * Return a pointer to this task's call_rcu_data if there is one.
483 */
484
485 struct call_rcu_data *get_thread_call_rcu_data(void)
486 {
487 return thread_call_rcu_data;
488 }
489
490 /*
491 * Set this task's call_rcu_data structure as specified, regardless
492 * of whether or not this task already had one. (This allows switching
493 * to and from real-time call_rcu threads, for example.)
494 *
495 * Use NULL to remove a thread's call_rcu_data structure, but it is
496 * the caller's responsibility to dispose of the removed structure.
497 * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
498 * (prior to NULLing it out, of course).
499 */
500
501 void set_thread_call_rcu_data(struct call_rcu_data *crdp)
502 {
503 thread_call_rcu_data = crdp;
504 }
505
506 /*
507 * Create a separate call_rcu thread for each CPU. This does not
508 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
509 * function if you want that behavior. Should be paired with
510 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
511 * threads.
512 */
513
514 int create_all_cpu_call_rcu_data(unsigned long flags)
515 {
516 int i;
517 struct call_rcu_data *crdp;
518 int ret;
519
520 call_rcu_lock(&call_rcu_mutex);
521 alloc_cpu_call_rcu_data();
522 call_rcu_unlock(&call_rcu_mutex);
523 if (maxcpus <= 0) {
524 errno = EINVAL;
525 return -EINVAL;
526 }
527 if (per_cpu_call_rcu_data == NULL) {
528 errno = ENOMEM;
529 return -ENOMEM;
530 }
531 for (i = 0; i < maxcpus; i++) {
532 call_rcu_lock(&call_rcu_mutex);
533 if (get_cpu_call_rcu_data(i)) {
534 call_rcu_unlock(&call_rcu_mutex);
535 continue;
536 }
537 crdp = __create_call_rcu_data(flags, i);
538 if (crdp == NULL) {
539 call_rcu_unlock(&call_rcu_mutex);
540 errno = ENOMEM;
541 return -ENOMEM;
542 }
543 call_rcu_unlock(&call_rcu_mutex);
544 if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) {
545 call_rcu_data_free(crdp);
546
547 /* it has been created by other thread */
548 if (ret == -EEXIST)
549 continue;
550
551 return ret;
552 }
553 }
554 return 0;
555 }
556
557 /*
558 * Wake up the call_rcu thread corresponding to the specified
559 * call_rcu_data structure.
560 */
561 static void wake_call_rcu_thread(struct call_rcu_data *crdp)
562 {
563 if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT))
564 call_rcu_wake_up(crdp);
565 }
566
567 /*
568 * Schedule a function to be invoked after a following grace period.
569 * This is the only function that must be called -- the others are
570 * only present to allow applications to tune their use of RCU for
571 * maximum performance.
572 *
573 * Note that unless a call_rcu thread has not already been created,
574 * the first invocation of call_rcu() will create one. So, if you
575 * need the first invocation of call_rcu() to be fast, make sure
576 * to create a call_rcu thread first. One way to accomplish this is
577 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
578 *
579 * call_rcu must be called by registered RCU read-side threads.
580 */
581
582 void call_rcu(struct rcu_head *head,
583 void (*func)(struct rcu_head *head))
584 {
585 struct call_rcu_data *crdp;
586
587 cds_wfq_node_init(&head->next);
588 head->func = func;
589 /* Holding rcu read-side lock across use of per-cpu crdp */
590 rcu_read_lock();
591 crdp = get_call_rcu_data();
592 cds_wfq_enqueue(&crdp->cbs, &head->next);
593 uatomic_inc(&crdp->qlen);
594 wake_call_rcu_thread(crdp);
595 rcu_read_unlock();
596 }
597
598 /*
599 * Free up the specified call_rcu_data structure, terminating the
600 * associated call_rcu thread. The caller must have previously
601 * removed the call_rcu_data structure from per-thread or per-CPU
602 * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
603 * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
604 * per-thread call_rcu_data structures.
605 *
606 * We silently refuse to free up the default call_rcu_data structure
607 * because that is where we put any leftover callbacks. Note that
608 * the possibility of self-spawning callbacks makes it impossible
609 * to execute all the callbacks in finite time without putting any
610 * newly spawned callbacks somewhere else. The "somewhere else" of
611 * last resort is the default call_rcu_data structure.
612 *
613 * We also silently refuse to free NULL pointers. This simplifies
614 * the calling code.
615 */
616 void call_rcu_data_free(struct call_rcu_data *crdp)
617 {
618 struct cds_wfq_node *cbs;
619 struct cds_wfq_node **cbs_tail;
620 struct cds_wfq_node **cbs_endprev;
621
622 if (crdp == NULL || crdp == default_call_rcu_data) {
623 return;
624 }
625 if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) {
626 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP);
627 wake_call_rcu_thread(crdp);
628 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0)
629 poll(NULL, 0, 1);
630 }
631 if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) {
632 while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL)
633 poll(NULL, 0, 1);
634 _CMM_STORE_SHARED(crdp->cbs.head, NULL);
635 cbs_tail = (struct cds_wfq_node **)
636 uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head);
637 /* Create default call rcu data if need be */
638 (void) get_default_call_rcu_data();
639 cbs_endprev = (struct cds_wfq_node **)
640 uatomic_xchg(&default_call_rcu_data, cbs_tail);
641 *cbs_endprev = cbs;
642 uatomic_add(&default_call_rcu_data->qlen,
643 uatomic_read(&crdp->qlen));
644 wake_call_rcu_thread(default_call_rcu_data);
645 }
646
647 call_rcu_lock(&call_rcu_mutex);
648 cds_list_del(&crdp->list);
649 call_rcu_unlock(&call_rcu_mutex);
650
651 free(crdp);
652 }
653
654 /*
655 * Clean up all the per-CPU call_rcu threads.
656 */
657 void free_all_cpu_call_rcu_data(void)
658 {
659 int cpu;
660 struct call_rcu_data **crdp;
661 static int warned = 0;
662
663 if (maxcpus <= 0)
664 return;
665
666 crdp = malloc(sizeof(*crdp) * maxcpus);
667 if (!crdp) {
668 if (!warned) {
669 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
670 }
671 warned = 1;
672 }
673
674 for (cpu = 0; cpu < maxcpus; cpu++) {
675 crdp[cpu] = get_cpu_call_rcu_data(cpu);
676 if (crdp[cpu] == NULL)
677 continue;
678 set_cpu_call_rcu_data(cpu, NULL);
679 }
680 /*
681 * Wait for call_rcu sites acting as RCU readers of the
682 * call_rcu_data to become quiescent.
683 */
684 synchronize_rcu();
685 for (cpu = 0; cpu < maxcpus; cpu++) {
686 if (crdp[cpu] == NULL)
687 continue;
688 call_rcu_data_free(crdp[cpu]);
689 }
690 free(crdp);
691 }
692
693 /*
694 * Acquire the call_rcu_mutex in order to ensure that the child sees
695 * all of the call_rcu() data structures in a consistent state.
696 * Suitable for pthread_atfork() and friends.
697 */
698 void call_rcu_before_fork(void)
699 {
700 call_rcu_lock(&call_rcu_mutex);
701 }
702
703 /*
704 * Clean up call_rcu data structures in the parent of a successful fork()
705 * that is not followed by exec() in the child. Suitable for
706 * pthread_atfork() and friends.
707 */
708 void call_rcu_after_fork_parent(void)
709 {
710 call_rcu_unlock(&call_rcu_mutex);
711 }
712
713 /*
714 * Clean up call_rcu data structures in the child of a successful fork()
715 * that is not followed by exec(). Suitable for pthread_atfork() and
716 * friends.
717 */
718 void call_rcu_after_fork_child(void)
719 {
720 struct call_rcu_data *crdp, *next;
721
722 /* Release the mutex. */
723 call_rcu_unlock(&call_rcu_mutex);
724
725 /* Do nothing when call_rcu() has not been used */
726 if (cds_list_empty(&call_rcu_data_list))
727 return;
728
729 /*
730 * Allocate a new default call_rcu_data structure in order
731 * to get a working call_rcu thread to go with it.
732 */
733 default_call_rcu_data = NULL;
734 (void)get_default_call_rcu_data();
735
736 /* Cleanup call_rcu_data pointers before use */
737 maxcpus_reset();
738 free(per_cpu_call_rcu_data);
739 rcu_set_pointer(&per_cpu_call_rcu_data, NULL);
740 thread_call_rcu_data = NULL;
741
742 /* Dispose of all of the rest of the call_rcu_data structures. */
743 cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
744 if (crdp == default_call_rcu_data)
745 continue;
746 uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED);
747 call_rcu_data_free(crdp);
748 }
749 }
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