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
36 #include "compat-getcpu.h"
37 #include <urcu/assert.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 #ifdef 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
__attribute__((unused
)))
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 urcu_posix_assert(splice_ret
!= CDS_WFCQ_RET_WOULDBLOCK
);
359 urcu_posix_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
]);
467 * Return the tid corresponding to the call_rcu thread whose
468 * call_rcu_data structure is specified.
471 pthread_t
get_call_rcu_thread(struct call_rcu_data
*crdp
)
477 * Create a call_rcu_data structure (with thread) and return a pointer.
480 static struct call_rcu_data
*__create_call_rcu_data(unsigned long flags
,
483 struct call_rcu_data
*crdp
;
485 call_rcu_data_init(&crdp
, flags
, cpu_affinity
);
489 struct call_rcu_data
*create_call_rcu_data(unsigned long flags
,
492 struct call_rcu_data
*crdp
;
494 call_rcu_lock(&call_rcu_mutex
);
495 crdp
= __create_call_rcu_data(flags
, cpu_affinity
);
496 call_rcu_unlock(&call_rcu_mutex
);
501 * Set the specified CPU to use the specified call_rcu_data structure.
503 * Use NULL to remove a CPU's call_rcu_data structure, but it is
504 * the caller's responsibility to dispose of the removed structure.
505 * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
506 * (prior to NULLing it out, of course).
508 * The caller must wait for a grace-period to pass between return from
509 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
510 * previous call rcu data as argument.
513 int set_cpu_call_rcu_data(int cpu
, struct call_rcu_data
*crdp
)
515 static int warned
= 0;
517 call_rcu_lock(&call_rcu_mutex
);
518 alloc_cpu_call_rcu_data();
519 if (cpu
< 0 || maxcpus
<= cpu
) {
521 fprintf(stderr
, "[error] liburcu: set CPU # out of range\n");
524 call_rcu_unlock(&call_rcu_mutex
);
529 if (per_cpu_call_rcu_data
== NULL
) {
530 call_rcu_unlock(&call_rcu_mutex
);
535 if (per_cpu_call_rcu_data
[cpu
] != NULL
&& crdp
!= NULL
) {
536 call_rcu_unlock(&call_rcu_mutex
);
541 rcu_set_pointer(&per_cpu_call_rcu_data
[cpu
], crdp
);
542 call_rcu_unlock(&call_rcu_mutex
);
547 * Return a pointer to the default call_rcu_data structure, creating
548 * one if need be. Because we never free call_rcu_data structures,
549 * we don't need to be in an RCU read-side critical section.
552 struct call_rcu_data
*get_default_call_rcu_data(void)
554 if (default_call_rcu_data
!= NULL
)
555 return rcu_dereference(default_call_rcu_data
);
556 call_rcu_lock(&call_rcu_mutex
);
557 if (default_call_rcu_data
!= NULL
) {
558 call_rcu_unlock(&call_rcu_mutex
);
559 return default_call_rcu_data
;
561 call_rcu_data_init(&default_call_rcu_data
, 0, -1);
562 call_rcu_unlock(&call_rcu_mutex
);
563 return default_call_rcu_data
;
567 * Return the call_rcu_data structure that applies to the currently
568 * running thread. Any call_rcu_data structure assigned specifically
569 * to this thread has first priority, followed by any call_rcu_data
570 * structure assigned to the CPU on which the thread is running,
571 * followed by the default call_rcu_data structure. If there is not
572 * yet a default call_rcu_data structure, one will be created.
574 * Calls to this function and use of the returned call_rcu_data should
575 * be protected by RCU read-side lock.
577 struct call_rcu_data
*get_call_rcu_data(void)
579 struct call_rcu_data
*crd
;
581 if (URCU_TLS(thread_call_rcu_data
) != NULL
)
582 return URCU_TLS(thread_call_rcu_data
);
585 crd
= get_cpu_call_rcu_data(urcu_sched_getcpu());
590 return get_default_call_rcu_data();
594 * Return a pointer to this task's call_rcu_data if there is one.
597 struct call_rcu_data
*get_thread_call_rcu_data(void)
599 return URCU_TLS(thread_call_rcu_data
);
603 * Set this task's call_rcu_data structure as specified, regardless
604 * of whether or not this task already had one. (This allows switching
605 * to and from real-time call_rcu threads, for example.)
607 * Use NULL to remove a thread's call_rcu_data structure, but it is
608 * the caller's responsibility to dispose of the removed structure.
609 * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
610 * (prior to NULLing it out, of course).
613 void set_thread_call_rcu_data(struct call_rcu_data
*crdp
)
615 URCU_TLS(thread_call_rcu_data
) = crdp
;
619 * Create a separate call_rcu thread for each CPU. This does not
620 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
621 * function if you want that behavior. Should be paired with
622 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
626 int create_all_cpu_call_rcu_data(unsigned long flags
)
629 struct call_rcu_data
*crdp
;
632 call_rcu_lock(&call_rcu_mutex
);
633 alloc_cpu_call_rcu_data();
634 call_rcu_unlock(&call_rcu_mutex
);
639 if (per_cpu_call_rcu_data
== NULL
) {
643 for (i
= 0; i
< maxcpus
; i
++) {
644 call_rcu_lock(&call_rcu_mutex
);
645 if (get_cpu_call_rcu_data(i
)) {
646 call_rcu_unlock(&call_rcu_mutex
);
649 crdp
= __create_call_rcu_data(flags
, i
);
651 call_rcu_unlock(&call_rcu_mutex
);
655 call_rcu_unlock(&call_rcu_mutex
);
656 if ((ret
= set_cpu_call_rcu_data(i
, crdp
)) != 0) {
657 call_rcu_data_free(crdp
);
659 /* it has been created by other thread */
670 * Wake up the call_rcu thread corresponding to the specified
671 * call_rcu_data structure.
673 static void wake_call_rcu_thread(struct call_rcu_data
*crdp
)
675 if (!(_CMM_LOAD_SHARED(crdp
->flags
) & URCU_CALL_RCU_RT
))
676 call_rcu_wake_up(crdp
);
679 static void _call_rcu(struct rcu_head
*head
,
680 void (*func
)(struct rcu_head
*head
),
681 struct call_rcu_data
*crdp
)
683 cds_wfcq_node_init(&head
->next
);
685 cds_wfcq_enqueue(&crdp
->cbs_head
, &crdp
->cbs_tail
, &head
->next
);
686 uatomic_inc(&crdp
->qlen
);
687 wake_call_rcu_thread(crdp
);
691 * Schedule a function to be invoked after a following grace period.
692 * This is the only function that must be called -- the others are
693 * only present to allow applications to tune their use of RCU for
694 * maximum performance.
696 * Note that unless a call_rcu thread has not already been created,
697 * the first invocation of call_rcu() will create one. So, if you
698 * need the first invocation of call_rcu() to be fast, make sure
699 * to create a call_rcu thread first. One way to accomplish this is
700 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
702 * call_rcu must be called by registered RCU read-side threads.
704 void call_rcu(struct rcu_head
*head
,
705 void (*func
)(struct rcu_head
*head
))
707 struct call_rcu_data
*crdp
;
709 /* Holding rcu read-side lock across use of per-cpu crdp */
711 crdp
= get_call_rcu_data();
712 _call_rcu(head
, func
, crdp
);
717 * Free up the specified call_rcu_data structure, terminating the
718 * associated call_rcu thread. The caller must have previously
719 * removed the call_rcu_data structure from per-thread or per-CPU
720 * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
721 * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
722 * per-thread call_rcu_data structures.
724 * We silently refuse to free up the default call_rcu_data structure
725 * because that is where we put any leftover callbacks. Note that
726 * the possibility of self-spawning callbacks makes it impossible
727 * to execute all the callbacks in finite time without putting any
728 * newly spawned callbacks somewhere else. The "somewhere else" of
729 * last resort is the default call_rcu_data structure.
731 * We also silently refuse to free NULL pointers. This simplifies
734 * The caller must wait for a grace-period to pass between return from
735 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
736 * previous call rcu data as argument.
738 * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
739 * a list corruption bug in the 0.7.x series. The equivalent fix
740 * appeared in 0.6.8 for the stable-0.6 branch.
742 void call_rcu_data_free(struct call_rcu_data
*crdp
)
744 if (crdp
== NULL
|| crdp
== default_call_rcu_data
) {
747 if ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0) {
748 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_STOP
);
749 wake_call_rcu_thread(crdp
);
750 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0)
751 (void) poll(NULL
, 0, 1);
753 call_rcu_lock(&call_rcu_mutex
);
754 if (!cds_wfcq_empty(&crdp
->cbs_head
, &crdp
->cbs_tail
)) {
755 call_rcu_unlock(&call_rcu_mutex
);
756 /* Create default call rcu data if need be. */
757 /* CBs queued here will be handed to the default list. */
758 (void) get_default_call_rcu_data();
759 call_rcu_lock(&call_rcu_mutex
);
760 __cds_wfcq_splice_blocking(&default_call_rcu_data
->cbs_head
,
761 &default_call_rcu_data
->cbs_tail
,
762 &crdp
->cbs_head
, &crdp
->cbs_tail
);
763 uatomic_add(&default_call_rcu_data
->qlen
,
764 uatomic_read(&crdp
->qlen
));
765 wake_call_rcu_thread(default_call_rcu_data
);
768 cds_list_del(&crdp
->list
);
769 call_rcu_unlock(&call_rcu_mutex
);
775 * Clean up all the per-CPU call_rcu threads.
777 void free_all_cpu_call_rcu_data(void)
780 struct call_rcu_data
**crdp
;
781 static int warned
= 0;
786 crdp
= malloc(sizeof(*crdp
) * maxcpus
);
789 fprintf(stderr
, "[error] liburcu: unable to allocate per-CPU pointer array\n");
795 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
796 crdp
[cpu
] = get_cpu_call_rcu_data(cpu
);
797 if (crdp
[cpu
] == NULL
)
799 set_cpu_call_rcu_data(cpu
, NULL
);
802 * Wait for call_rcu sites acting as RCU readers of the
803 * call_rcu_data to become quiescent.
806 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
807 if (crdp
[cpu
] == NULL
)
809 call_rcu_data_free(crdp
[cpu
]);
815 void free_completion(struct urcu_ref
*ref
)
817 struct call_rcu_completion
*completion
;
819 completion
= caa_container_of(ref
, struct call_rcu_completion
, ref
);
824 void _rcu_barrier_complete(struct rcu_head
*head
)
826 struct call_rcu_completion_work
*work
;
827 struct call_rcu_completion
*completion
;
829 work
= caa_container_of(head
, struct call_rcu_completion_work
, head
);
830 completion
= work
->completion
;
831 if (!uatomic_sub_return(&completion
->barrier_count
, 1))
832 call_rcu_completion_wake_up(completion
);
833 urcu_ref_put(&completion
->ref
, free_completion
);
838 * Wait for all in-flight call_rcu callbacks to complete execution.
840 void rcu_barrier(void)
842 struct call_rcu_data
*crdp
;
843 struct call_rcu_completion
*completion
;
847 /* Put in offline state in QSBR. */
848 was_online
= _rcu_read_ongoing();
850 rcu_thread_offline();
852 * Calling a rcu_barrier() within a RCU read-side critical
853 * section is an error.
855 if (_rcu_read_ongoing()) {
856 static int warned
= 0;
859 fprintf(stderr
, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
865 completion
= calloc(sizeof(*completion
), 1);
869 call_rcu_lock(&call_rcu_mutex
);
870 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
873 /* Referenced by rcu_barrier() and each call_rcu thread. */
874 urcu_ref_set(&completion
->ref
, count
+ 1);
875 completion
->barrier_count
= count
;
877 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
878 struct call_rcu_completion_work
*work
;
880 work
= calloc(sizeof(*work
), 1);
883 work
->completion
= completion
;
884 _call_rcu(&work
->head
, _rcu_barrier_complete
, crdp
);
886 call_rcu_unlock(&call_rcu_mutex
);
890 uatomic_dec(&completion
->futex
);
891 /* Decrement futex before reading barrier_count */
893 if (!uatomic_read(&completion
->barrier_count
))
895 call_rcu_completion_wait(completion
);
898 urcu_ref_put(&completion
->ref
, free_completion
);
906 * Acquire the call_rcu_mutex in order to ensure that the child sees
907 * all of the call_rcu() data structures in a consistent state. Ensure
908 * that all call_rcu threads are in a quiescent state across fork.
909 * Suitable for pthread_atfork() and friends.
911 void call_rcu_before_fork(void)
913 struct call_rcu_data
*crdp
;
914 struct urcu_atfork
*atfork
;
916 call_rcu_lock(&call_rcu_mutex
);
918 atfork
= registered_rculfhash_atfork
;
920 atfork
->before_fork(atfork
->priv
);
922 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
923 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_PAUSE
);
924 cmm_smp_mb__after_uatomic_or();
925 wake_call_rcu_thread(crdp
);
927 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
928 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) == 0)
929 (void) poll(NULL
, 0, 1);
934 * Clean up call_rcu data structures in the parent of a successful fork()
935 * that is not followed by exec() in the child. Suitable for
936 * pthread_atfork() and friends.
938 void call_rcu_after_fork_parent(void)
940 struct call_rcu_data
*crdp
;
941 struct urcu_atfork
*atfork
;
943 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
944 uatomic_and(&crdp
->flags
, ~URCU_CALL_RCU_PAUSE
);
945 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
946 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) != 0)
947 (void) poll(NULL
, 0, 1);
949 atfork
= registered_rculfhash_atfork
;
951 atfork
->after_fork_parent(atfork
->priv
);
952 call_rcu_unlock(&call_rcu_mutex
);
956 * Clean up call_rcu data structures in the child of a successful fork()
957 * that is not followed by exec(). Suitable for pthread_atfork() and
960 void call_rcu_after_fork_child(void)
962 struct call_rcu_data
*crdp
, *next
;
963 struct urcu_atfork
*atfork
;
965 /* Release the mutex. */
966 call_rcu_unlock(&call_rcu_mutex
);
968 atfork
= registered_rculfhash_atfork
;
970 atfork
->after_fork_child(atfork
->priv
);
972 /* Do nothing when call_rcu() has not been used */
973 if (cds_list_empty(&call_rcu_data_list
))
977 * Allocate a new default call_rcu_data structure in order
978 * to get a working call_rcu thread to go with it.
980 default_call_rcu_data
= NULL
;
981 (void)get_default_call_rcu_data();
983 /* Cleanup call_rcu_data pointers before use */
985 free(per_cpu_call_rcu_data
);
986 rcu_set_pointer(&per_cpu_call_rcu_data
, NULL
);
987 URCU_TLS(thread_call_rcu_data
) = NULL
;
990 * Dispose of all of the rest of the call_rcu_data structures.
991 * Leftover call_rcu callbacks will be merged into the new
992 * default call_rcu thread queue.
994 cds_list_for_each_entry_safe(crdp
, next
, &call_rcu_data_list
, list
) {
995 if (crdp
== default_call_rcu_data
)
997 uatomic_set(&crdp
->flags
, URCU_CALL_RCU_STOPPED
);
998 call_rcu_data_free(crdp
);
1002 void urcu_register_rculfhash_atfork(struct urcu_atfork
*atfork
)
1004 call_rcu_lock(&call_rcu_mutex
);
1005 if (registered_rculfhash_atfork_refcount
++)
1007 registered_rculfhash_atfork
= atfork
;
1009 call_rcu_unlock(&call_rcu_mutex
);
1012 void urcu_unregister_rculfhash_atfork(struct urcu_atfork
*atfork
__attribute__((unused
)))
1014 call_rcu_lock(&call_rcu_mutex
);
1015 if (--registered_rculfhash_atfork_refcount
)
1017 registered_rculfhash_atfork
= NULL
;
1019 call_rcu_unlock(&call_rcu_mutex
);