4 * Userspace RCU library - batch memory reclamation with kernel API
6 * Copyright (c) 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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.
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.
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
37 #include "compat-getcpu.h"
38 #include <urcu/wfcqueue.h>
39 #include <urcu/call-rcu.h>
40 #include <urcu/pointer.h>
41 #include <urcu/list.h>
42 #include <urcu/futex.h>
43 #include <urcu/tls-compat.h>
46 #include "urcu-utils.h"
48 #define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */
49 #define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1)
51 /* Data structure that identifies a call_rcu thread. */
53 struct call_rcu_data
{
55 * We do not align head on a different cache-line than tail
56 * mainly because call_rcu callback-invocation threads use
57 * batching ("splice") to get an entire list of callbacks, which
58 * effectively empties the queue, and requires to touch the tail
61 struct cds_wfcq_tail cbs_tail
;
62 struct cds_wfcq_head cbs_head
;
65 unsigned long qlen
; /* maintained for debugging. */
68 unsigned long gp_count
;
69 struct cds_list_head list
;
70 } __attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
72 struct call_rcu_completion
{
78 struct call_rcu_completion_work
{
80 struct call_rcu_completion
*completion
;
84 * List of all call_rcu_data structures to keep valgrind happy.
85 * Protected by call_rcu_mutex.
88 static CDS_LIST_HEAD(call_rcu_data_list
);
90 /* Link a thread using call_rcu() to its call_rcu thread. */
92 static DEFINE_URCU_TLS(struct call_rcu_data
*, thread_call_rcu_data
);
95 * Guard call_rcu thread creation and atfork handlers.
97 static pthread_mutex_t call_rcu_mutex
= PTHREAD_MUTEX_INITIALIZER
;
99 /* If a given thread does not have its own call_rcu thread, this is default. */
101 static struct call_rcu_data
*default_call_rcu_data
;
103 static struct urcu_atfork
*registered_rculfhash_atfork
;
104 static unsigned long registered_rculfhash_atfork_refcount
;
107 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
108 * available, then we can have call_rcu threads assigned to individual
109 * CPUs rather than only to specific threads.
112 #if defined(HAVE_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID))
115 * Pointer to array of pointers to per-CPU call_rcu_data structures
116 * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an
117 * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a
118 * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer
119 * without mutex. The call_rcu_mutex protects updates.
122 static struct call_rcu_data
**per_cpu_call_rcu_data
;
125 static void maxcpus_reset(void)
130 /* Allocate the array if it has not already been allocated. */
132 static void alloc_cpu_call_rcu_data(void)
134 struct call_rcu_data
**p
;
135 static int warned
= 0;
139 maxcpus
= sysconf(_SC_NPROCESSORS_CONF
);
143 p
= malloc(maxcpus
* sizeof(*per_cpu_call_rcu_data
));
145 memset(p
, '\0', maxcpus
* sizeof(*per_cpu_call_rcu_data
));
146 rcu_set_pointer(&per_cpu_call_rcu_data
, p
);
149 fprintf(stderr
, "[error] liburcu: unable to allocate per-CPU pointer array\n");
155 #else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
158 * per_cpu_call_rcu_data should be constant, but some functions below, used both
159 * for cases where cpu number is available and not available, assume it it not
162 static struct call_rcu_data
**per_cpu_call_rcu_data
= NULL
;
163 static const long maxcpus
= -1;
165 static void maxcpus_reset(void)
169 static void alloc_cpu_call_rcu_data(void)
173 #endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
175 /* Acquire the specified pthread mutex. */
177 static void call_rcu_lock(pthread_mutex_t
*pmp
)
181 ret
= pthread_mutex_lock(pmp
);
186 /* Release the specified pthread mutex. */
188 static void call_rcu_unlock(pthread_mutex_t
*pmp
)
192 ret
= pthread_mutex_unlock(pmp
);
198 * Periodically retry setting CPU affinity if we migrate.
199 * Losing affinity can be caused by CPU hotunplug/hotplug, or by
202 #if HAVE_SCHED_SETAFFINITY
204 int set_thread_cpu_affinity(struct call_rcu_data
*crdp
)
209 if (crdp
->cpu_affinity
< 0)
211 if (++crdp
->gp_count
& SET_AFFINITY_CHECK_PERIOD_MASK
)
213 if (urcu_sched_getcpu() == crdp
->cpu_affinity
)
217 CPU_SET(crdp
->cpu_affinity
, &mask
);
218 ret
= sched_setaffinity(0, sizeof(mask
), &mask
);
221 * EINVAL is fine: can be caused by hotunplugged CPUs, or by
222 * cpuset(7). This is why we should always retry if we detect
225 if (ret
&& errno
== EINVAL
) {
233 int set_thread_cpu_affinity(struct call_rcu_data
*crdp
)
239 static void call_rcu_wait(struct call_rcu_data
*crdp
)
241 /* Read call_rcu list before read futex */
243 if (uatomic_read(&crdp
->futex
) != -1)
245 while (futex_async(&crdp
->futex
, FUTEX_WAIT
, -1,
249 /* Value already changed. */
252 /* Retry if interrupted by signal. */
253 break; /* Get out of switch. */
255 /* Unexpected error. */
261 static void call_rcu_wake_up(struct call_rcu_data
*crdp
)
263 /* Write to call_rcu list before reading/writing futex */
265 if (caa_unlikely(uatomic_read(&crdp
->futex
) == -1)) {
266 uatomic_set(&crdp
->futex
, 0);
267 if (futex_async(&crdp
->futex
, FUTEX_WAKE
, 1,
273 static void call_rcu_completion_wait(struct call_rcu_completion
*completion
)
275 /* Read completion barrier count before read futex */
277 if (uatomic_read(&completion
->futex
) != -1)
279 while (futex_async(&completion
->futex
, FUTEX_WAIT
, -1,
283 /* Value already changed. */
286 /* Retry if interrupted by signal. */
287 break; /* Get out of switch. */
289 /* Unexpected error. */
295 static void call_rcu_completion_wake_up(struct call_rcu_completion
*completion
)
297 /* Write to completion barrier count before reading/writing futex */
299 if (caa_unlikely(uatomic_read(&completion
->futex
) == -1)) {
300 uatomic_set(&completion
->futex
, 0);
301 if (futex_async(&completion
->futex
, FUTEX_WAKE
, 1,
307 /* This is the code run by each call_rcu thread. */
309 static void *call_rcu_thread(void *arg
)
311 unsigned long cbcount
;
312 struct call_rcu_data
*crdp
= (struct call_rcu_data
*) arg
;
313 int rt
= !!(uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_RT
);
315 if (set_thread_cpu_affinity(crdp
))
319 * If callbacks take a read-side lock, we need to be registered.
321 rcu_register_thread();
323 URCU_TLS(thread_call_rcu_data
) = crdp
;
325 uatomic_dec(&crdp
->futex
);
326 /* Decrement futex before reading call_rcu list */
330 struct cds_wfcq_head cbs_tmp_head
;
331 struct cds_wfcq_tail cbs_tmp_tail
;
332 struct cds_wfcq_node
*cbs
, *cbs_tmp_n
;
333 enum cds_wfcq_ret splice_ret
;
335 if (set_thread_cpu_affinity(crdp
))
338 if (uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSE
) {
340 * Pause requested. Become quiescent: remove
341 * ourself from all global lists, and don't
342 * process any callback. The callback lists may
343 * still be non-empty though.
345 rcu_unregister_thread();
346 cmm_smp_mb__before_uatomic_or();
347 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_PAUSED
);
348 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSE
) != 0)
349 (void) poll(NULL
, 0, 1);
350 uatomic_and(&crdp
->flags
, ~URCU_CALL_RCU_PAUSED
);
351 cmm_smp_mb__after_uatomic_and();
352 rcu_register_thread();
355 cds_wfcq_init(&cbs_tmp_head
, &cbs_tmp_tail
);
356 splice_ret
= __cds_wfcq_splice_blocking(&cbs_tmp_head
,
357 &cbs_tmp_tail
, &crdp
->cbs_head
, &crdp
->cbs_tail
);
358 assert(splice_ret
!= CDS_WFCQ_RET_WOULDBLOCK
);
359 assert(splice_ret
!= CDS_WFCQ_RET_DEST_NON_EMPTY
);
360 if (splice_ret
!= CDS_WFCQ_RET_SRC_EMPTY
) {
363 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head
,
364 &cbs_tmp_tail
, cbs
, cbs_tmp_n
) {
365 struct rcu_head
*rhp
;
367 rhp
= caa_container_of(cbs
,
368 struct rcu_head
, next
);
372 uatomic_sub(&crdp
->qlen
, cbcount
);
374 if (uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOP
)
376 rcu_thread_offline();
378 if (cds_wfcq_empty(&crdp
->cbs_head
,
381 (void) poll(NULL
, 0, 10);
382 uatomic_dec(&crdp
->futex
);
384 * Decrement futex before reading
389 (void) poll(NULL
, 0, 10);
392 (void) poll(NULL
, 0, 10);
398 * Read call_rcu list before write futex.
401 uatomic_set(&crdp
->futex
, 0);
403 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_STOPPED
);
404 rcu_unregister_thread();
409 * Create both a call_rcu thread and the corresponding call_rcu_data
410 * structure, linking the structure in as specified. Caller must hold
414 static void call_rcu_data_init(struct call_rcu_data
**crdpp
,
418 struct call_rcu_data
*crdp
;
421 crdp
= malloc(sizeof(*crdp
));
424 memset(crdp
, '\0', sizeof(*crdp
));
425 cds_wfcq_init(&crdp
->cbs_head
, &crdp
->cbs_tail
);
429 cds_list_add(&crdp
->list
, &call_rcu_data_list
);
430 crdp
->cpu_affinity
= cpu_affinity
;
432 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
434 ret
= pthread_create(&crdp
->tid
, NULL
, call_rcu_thread
, crdp
);
440 * Return a pointer to the call_rcu_data structure for the specified
441 * CPU, returning NULL if there is none. We cannot automatically
442 * created it because the platform we are running on might not define
443 * urcu_sched_getcpu().
445 * The call to this function and use of the returned call_rcu_data
446 * should be protected by RCU read-side lock.
449 struct call_rcu_data
*get_cpu_call_rcu_data(int cpu
)
451 static int warned
= 0;
452 struct call_rcu_data
**pcpu_crdp
;
454 pcpu_crdp
= rcu_dereference(per_cpu_call_rcu_data
);
455 if (pcpu_crdp
== NULL
)
457 if (!warned
&& maxcpus
> 0 && (cpu
< 0 || maxcpus
<= cpu
)) {
458 fprintf(stderr
, "[error] liburcu: get CPU # out of range\n");
461 if (cpu
< 0 || maxcpus
<= cpu
)
463 return rcu_dereference(pcpu_crdp
[cpu
]);
465 URCU_ATTR_ALIAS(urcu_stringify(get_cpu_call_rcu_data
))
466 struct call_rcu_data
*alias_get_cpu_call_rcu_data();
469 * Return the tid corresponding to the call_rcu thread whose
470 * call_rcu_data structure is specified.
473 pthread_t
get_call_rcu_thread(struct call_rcu_data
*crdp
)
477 URCU_ATTR_ALIAS(urcu_stringify(get_call_rcu_thread
))
478 pthread_t
alias_get_call_rcu_thread();
481 * Create a call_rcu_data structure (with thread) and return a pointer.
484 static struct call_rcu_data
*__create_call_rcu_data(unsigned long flags
,
487 struct call_rcu_data
*crdp
;
489 call_rcu_data_init(&crdp
, flags
, cpu_affinity
);
493 URCU_ATTR_ALIAS(urcu_stringify(create_call_rcu_data
))
494 struct call_rcu_data
*alias_create_call_rcu_data();
495 struct call_rcu_data
*create_call_rcu_data(unsigned long flags
,
498 struct call_rcu_data
*crdp
;
500 call_rcu_lock(&call_rcu_mutex
);
501 crdp
= __create_call_rcu_data(flags
, cpu_affinity
);
502 call_rcu_unlock(&call_rcu_mutex
);
507 * Set the specified CPU to use the specified call_rcu_data structure.
509 * Use NULL to remove a CPU's call_rcu_data structure, but it is
510 * the caller's responsibility to dispose of the removed structure.
511 * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
512 * (prior to NULLing it out, of course).
514 * The caller must wait for a grace-period to pass between return from
515 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
516 * previous call rcu data as argument.
519 int set_cpu_call_rcu_data(int cpu
, struct call_rcu_data
*crdp
)
521 static int warned
= 0;
523 call_rcu_lock(&call_rcu_mutex
);
524 alloc_cpu_call_rcu_data();
525 if (cpu
< 0 || maxcpus
<= cpu
) {
527 fprintf(stderr
, "[error] liburcu: set CPU # out of range\n");
530 call_rcu_unlock(&call_rcu_mutex
);
535 if (per_cpu_call_rcu_data
== NULL
) {
536 call_rcu_unlock(&call_rcu_mutex
);
541 if (per_cpu_call_rcu_data
[cpu
] != NULL
&& crdp
!= NULL
) {
542 call_rcu_unlock(&call_rcu_mutex
);
547 rcu_set_pointer(&per_cpu_call_rcu_data
[cpu
], crdp
);
548 call_rcu_unlock(&call_rcu_mutex
);
551 URCU_ATTR_ALIAS(urcu_stringify(set_cpu_call_rcu_data
))
552 int alias_set_cpu_call_rcu_data();
555 * Return a pointer to the default call_rcu_data structure, creating
556 * one if need be. Because we never free call_rcu_data structures,
557 * we don't need to be in an RCU read-side critical section.
560 struct call_rcu_data
*get_default_call_rcu_data(void)
562 if (default_call_rcu_data
!= NULL
)
563 return rcu_dereference(default_call_rcu_data
);
564 call_rcu_lock(&call_rcu_mutex
);
565 if (default_call_rcu_data
!= NULL
) {
566 call_rcu_unlock(&call_rcu_mutex
);
567 return default_call_rcu_data
;
569 call_rcu_data_init(&default_call_rcu_data
, 0, -1);
570 call_rcu_unlock(&call_rcu_mutex
);
571 return default_call_rcu_data
;
573 URCU_ATTR_ALIAS(urcu_stringify(get_default_call_rcu_data
))
574 struct call_rcu_data
*alias_get_default_call_rcu_data();
577 * Return the call_rcu_data structure that applies to the currently
578 * running thread. Any call_rcu_data structure assigned specifically
579 * to this thread has first priority, followed by any call_rcu_data
580 * structure assigned to the CPU on which the thread is running,
581 * followed by the default call_rcu_data structure. If there is not
582 * yet a default call_rcu_data structure, one will be created.
584 * Calls to this function and use of the returned call_rcu_data should
585 * be protected by RCU read-side lock.
587 struct call_rcu_data
*get_call_rcu_data(void)
589 struct call_rcu_data
*crd
;
591 if (URCU_TLS(thread_call_rcu_data
) != NULL
)
592 return URCU_TLS(thread_call_rcu_data
);
595 crd
= get_cpu_call_rcu_data(urcu_sched_getcpu());
600 return get_default_call_rcu_data();
602 URCU_ATTR_ALIAS(urcu_stringify(get_call_rcu_data
))
603 struct call_rcu_data
*alias_get_call_rcu_data();
606 * Return a pointer to this task's call_rcu_data if there is one.
609 struct call_rcu_data
*get_thread_call_rcu_data(void)
611 return URCU_TLS(thread_call_rcu_data
);
613 URCU_ATTR_ALIAS(urcu_stringify(get_thread_call_rcu_data
))
614 struct call_rcu_data
*alias_get_thread_call_rcu_data();
617 * Set this task's call_rcu_data structure as specified, regardless
618 * of whether or not this task already had one. (This allows switching
619 * to and from real-time call_rcu threads, for example.)
621 * Use NULL to remove a thread's call_rcu_data structure, but it is
622 * the caller's responsibility to dispose of the removed structure.
623 * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
624 * (prior to NULLing it out, of course).
627 void set_thread_call_rcu_data(struct call_rcu_data
*crdp
)
629 URCU_TLS(thread_call_rcu_data
) = crdp
;
631 URCU_ATTR_ALIAS(urcu_stringify(set_thread_call_rcu_data
))
632 void alias_set_thread_call_rcu_data();
635 * Create a separate call_rcu thread for each CPU. This does not
636 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
637 * function if you want that behavior. Should be paired with
638 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
642 int create_all_cpu_call_rcu_data(unsigned long flags
)
645 struct call_rcu_data
*crdp
;
648 call_rcu_lock(&call_rcu_mutex
);
649 alloc_cpu_call_rcu_data();
650 call_rcu_unlock(&call_rcu_mutex
);
655 if (per_cpu_call_rcu_data
== NULL
) {
659 for (i
= 0; i
< maxcpus
; i
++) {
660 call_rcu_lock(&call_rcu_mutex
);
661 if (get_cpu_call_rcu_data(i
)) {
662 call_rcu_unlock(&call_rcu_mutex
);
665 crdp
= __create_call_rcu_data(flags
, i
);
667 call_rcu_unlock(&call_rcu_mutex
);
671 call_rcu_unlock(&call_rcu_mutex
);
672 if ((ret
= set_cpu_call_rcu_data(i
, crdp
)) != 0) {
673 call_rcu_data_free(crdp
);
675 /* it has been created by other thread */
684 URCU_ATTR_ALIAS(urcu_stringify(create_all_cpu_call_rcu_data
))
685 int alias_create_all_cpu_call_rcu_data();
688 * Wake up the call_rcu thread corresponding to the specified
689 * call_rcu_data structure.
691 static void wake_call_rcu_thread(struct call_rcu_data
*crdp
)
693 if (!(_CMM_LOAD_SHARED(crdp
->flags
) & URCU_CALL_RCU_RT
))
694 call_rcu_wake_up(crdp
);
697 static void _call_rcu(struct rcu_head
*head
,
698 void (*func
)(struct rcu_head
*head
),
699 struct call_rcu_data
*crdp
)
701 cds_wfcq_node_init(&head
->next
);
703 cds_wfcq_enqueue(&crdp
->cbs_head
, &crdp
->cbs_tail
, &head
->next
);
704 uatomic_inc(&crdp
->qlen
);
705 wake_call_rcu_thread(crdp
);
709 * Schedule a function to be invoked after a following grace period.
710 * This is the only function that must be called -- the others are
711 * only present to allow applications to tune their use of RCU for
712 * maximum performance.
714 * Note that unless a call_rcu thread has not already been created,
715 * the first invocation of call_rcu() will create one. So, if you
716 * need the first invocation of call_rcu() to be fast, make sure
717 * to create a call_rcu thread first. One way to accomplish this is
718 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
720 * call_rcu must be called by registered RCU read-side threads.
722 void call_rcu(struct rcu_head
*head
,
723 void (*func
)(struct rcu_head
*head
))
725 struct call_rcu_data
*crdp
;
727 /* Holding rcu read-side lock across use of per-cpu crdp */
729 crdp
= get_call_rcu_data();
730 _call_rcu(head
, func
, crdp
);
733 URCU_ATTR_ALIAS(urcu_stringify(call_rcu
)) void alias_call_rcu();
736 * Free up the specified call_rcu_data structure, terminating the
737 * associated call_rcu thread. The caller must have previously
738 * removed the call_rcu_data structure from per-thread or per-CPU
739 * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
740 * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
741 * per-thread call_rcu_data structures.
743 * We silently refuse to free up the default call_rcu_data structure
744 * because that is where we put any leftover callbacks. Note that
745 * the possibility of self-spawning callbacks makes it impossible
746 * to execute all the callbacks in finite time without putting any
747 * newly spawned callbacks somewhere else. The "somewhere else" of
748 * last resort is the default call_rcu_data structure.
750 * We also silently refuse to free NULL pointers. This simplifies
753 * The caller must wait for a grace-period to pass between return from
754 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
755 * previous call rcu data as argument.
757 * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
758 * a list corruption bug in the 0.7.x series. The equivalent fix
759 * appeared in 0.6.8 for the stable-0.6 branch.
761 void call_rcu_data_free(struct call_rcu_data
*crdp
)
763 if (crdp
== NULL
|| crdp
== default_call_rcu_data
) {
766 if ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0) {
767 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_STOP
);
768 wake_call_rcu_thread(crdp
);
769 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0)
770 (void) poll(NULL
, 0, 1);
772 call_rcu_lock(&call_rcu_mutex
);
773 if (!cds_wfcq_empty(&crdp
->cbs_head
, &crdp
->cbs_tail
)) {
774 call_rcu_unlock(&call_rcu_mutex
);
775 /* Create default call rcu data if need be. */
776 /* CBs queued here will be handed to the default list. */
777 (void) get_default_call_rcu_data();
778 call_rcu_lock(&call_rcu_mutex
);
779 __cds_wfcq_splice_blocking(&default_call_rcu_data
->cbs_head
,
780 &default_call_rcu_data
->cbs_tail
,
781 &crdp
->cbs_head
, &crdp
->cbs_tail
);
782 uatomic_add(&default_call_rcu_data
->qlen
,
783 uatomic_read(&crdp
->qlen
));
784 wake_call_rcu_thread(default_call_rcu_data
);
787 cds_list_del(&crdp
->list
);
788 call_rcu_unlock(&call_rcu_mutex
);
792 URCU_ATTR_ALIAS(urcu_stringify(call_rcu_data_free
))
793 void alias_call_rcu_data_free();
796 * Clean up all the per-CPU call_rcu threads.
798 void free_all_cpu_call_rcu_data(void)
801 struct call_rcu_data
**crdp
;
802 static int warned
= 0;
807 crdp
= malloc(sizeof(*crdp
) * maxcpus
);
810 fprintf(stderr
, "[error] liburcu: unable to allocate per-CPU pointer array\n");
816 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
817 crdp
[cpu
] = get_cpu_call_rcu_data(cpu
);
818 if (crdp
[cpu
] == NULL
)
820 set_cpu_call_rcu_data(cpu
, NULL
);
823 * Wait for call_rcu sites acting as RCU readers of the
824 * call_rcu_data to become quiescent.
827 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
828 if (crdp
[cpu
] == NULL
)
830 call_rcu_data_free(crdp
[cpu
]);
835 /* ABI6 has a non-namespaced free_all_cpu_call_rcu_data for qsbr */
836 #undef free_all_cpu_call_rcu_data
837 URCU_ATTR_ALIAS("urcu_qsbr_free_all_cpu_call_rcu_data")
838 void free_all_cpu_call_rcu_data();
839 #define free_all_cpu_call_rcu_data urcu_qsbr_free_all_cpu_call_rcu_data
841 URCU_ATTR_ALIAS(urcu_stringify(free_all_cpu_call_rcu_data
))
842 void alias_free_all_cpu_call_rcu_data();
846 void free_completion(struct urcu_ref
*ref
)
848 struct call_rcu_completion
*completion
;
850 completion
= caa_container_of(ref
, struct call_rcu_completion
, ref
);
855 void _rcu_barrier_complete(struct rcu_head
*head
)
857 struct call_rcu_completion_work
*work
;
858 struct call_rcu_completion
*completion
;
860 work
= caa_container_of(head
, struct call_rcu_completion_work
, head
);
861 completion
= work
->completion
;
862 if (!uatomic_sub_return(&completion
->barrier_count
, 1))
863 call_rcu_completion_wake_up(completion
);
864 urcu_ref_put(&completion
->ref
, free_completion
);
869 * Wait for all in-flight call_rcu callbacks to complete execution.
871 void rcu_barrier(void)
873 struct call_rcu_data
*crdp
;
874 struct call_rcu_completion
*completion
;
878 /* Put in offline state in QSBR. */
879 was_online
= _rcu_read_ongoing();
881 rcu_thread_offline();
883 * Calling a rcu_barrier() within a RCU read-side critical
884 * section is an error.
886 if (_rcu_read_ongoing()) {
887 static int warned
= 0;
890 fprintf(stderr
, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
896 completion
= calloc(sizeof(*completion
), 1);
900 call_rcu_lock(&call_rcu_mutex
);
901 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
904 /* Referenced by rcu_barrier() and each call_rcu thread. */
905 urcu_ref_set(&completion
->ref
, count
+ 1);
906 completion
->barrier_count
= count
;
908 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
909 struct call_rcu_completion_work
*work
;
911 work
= calloc(sizeof(*work
), 1);
914 work
->completion
= completion
;
915 _call_rcu(&work
->head
, _rcu_barrier_complete
, crdp
);
917 call_rcu_unlock(&call_rcu_mutex
);
921 uatomic_dec(&completion
->futex
);
922 /* Decrement futex before reading barrier_count */
924 if (!uatomic_read(&completion
->barrier_count
))
926 call_rcu_completion_wait(completion
);
929 urcu_ref_put(&completion
->ref
, free_completion
);
935 URCU_ATTR_ALIAS(urcu_stringify(rcu_barrier
))
936 void alias_rcu_barrier();
939 * Acquire the call_rcu_mutex in order to ensure that the child sees
940 * all of the call_rcu() data structures in a consistent state. Ensure
941 * that all call_rcu threads are in a quiescent state across fork.
942 * Suitable for pthread_atfork() and friends.
944 void call_rcu_before_fork(void)
946 struct call_rcu_data
*crdp
;
947 struct urcu_atfork
*atfork
;
949 call_rcu_lock(&call_rcu_mutex
);
951 atfork
= registered_rculfhash_atfork
;
953 atfork
->before_fork(atfork
->priv
);
955 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
956 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_PAUSE
);
957 cmm_smp_mb__after_uatomic_or();
958 wake_call_rcu_thread(crdp
);
960 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
961 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) == 0)
962 (void) poll(NULL
, 0, 1);
965 URCU_ATTR_ALIAS(urcu_stringify(call_rcu_before_fork
))
966 void alias_call_rcu_before_fork();
969 * Clean up call_rcu data structures in the parent of a successful fork()
970 * that is not followed by exec() in the child. Suitable for
971 * pthread_atfork() and friends.
973 void call_rcu_after_fork_parent(void)
975 struct call_rcu_data
*crdp
;
976 struct urcu_atfork
*atfork
;
978 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
979 uatomic_and(&crdp
->flags
, ~URCU_CALL_RCU_PAUSE
);
980 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
981 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) != 0)
982 (void) poll(NULL
, 0, 1);
984 atfork
= registered_rculfhash_atfork
;
986 atfork
->after_fork_parent(atfork
->priv
);
987 call_rcu_unlock(&call_rcu_mutex
);
989 URCU_ATTR_ALIAS(urcu_stringify(call_rcu_after_fork_parent
))
990 void alias_call_rcu_after_fork_parent();
993 * Clean up call_rcu data structures in the child of a successful fork()
994 * that is not followed by exec(). Suitable for pthread_atfork() and
997 void call_rcu_after_fork_child(void)
999 struct call_rcu_data
*crdp
, *next
;
1000 struct urcu_atfork
*atfork
;
1002 /* Release the mutex. */
1003 call_rcu_unlock(&call_rcu_mutex
);
1005 atfork
= registered_rculfhash_atfork
;
1007 atfork
->after_fork_child(atfork
->priv
);
1009 /* Do nothing when call_rcu() has not been used */
1010 if (cds_list_empty(&call_rcu_data_list
))
1014 * Allocate a new default call_rcu_data structure in order
1015 * to get a working call_rcu thread to go with it.
1017 default_call_rcu_data
= NULL
;
1018 (void)get_default_call_rcu_data();
1020 /* Cleanup call_rcu_data pointers before use */
1022 free(per_cpu_call_rcu_data
);
1023 rcu_set_pointer(&per_cpu_call_rcu_data
, NULL
);
1024 URCU_TLS(thread_call_rcu_data
) = NULL
;
1027 * Dispose of all of the rest of the call_rcu_data structures.
1028 * Leftover call_rcu callbacks will be merged into the new
1029 * default call_rcu thread queue.
1031 cds_list_for_each_entry_safe(crdp
, next
, &call_rcu_data_list
, list
) {
1032 if (crdp
== default_call_rcu_data
)
1034 uatomic_set(&crdp
->flags
, URCU_CALL_RCU_STOPPED
);
1035 call_rcu_data_free(crdp
);
1038 URCU_ATTR_ALIAS(urcu_stringify(call_rcu_after_fork_child
))
1039 void alias_call_rcu_after_fork_child();
1041 void urcu_register_rculfhash_atfork(struct urcu_atfork
*atfork
)
1043 call_rcu_lock(&call_rcu_mutex
);
1044 if (registered_rculfhash_atfork_refcount
++)
1046 registered_rculfhash_atfork
= atfork
;
1048 call_rcu_unlock(&call_rcu_mutex
);
1050 URCU_ATTR_ALIAS(urcu_stringify(urcu_register_rculfhash_atfork
))
1051 void alias_urcu_register_rculfhash_atfork();
1053 void urcu_unregister_rculfhash_atfork(struct urcu_atfork
*atfork
__attribute__((unused
)))
1055 call_rcu_lock(&call_rcu_mutex
);
1056 if (--registered_rculfhash_atfork_refcount
)
1058 registered_rculfhash_atfork
= NULL
;
1060 call_rcu_unlock(&call_rcu_mutex
);
1062 URCU_ATTR_ALIAS(urcu_stringify(urcu_unregister_rculfhash_atfork
))
1063 void alias_urcu_unregister_rculfhash_atfork();