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
39 #include "compat-getcpu.h"
40 #include "urcu/wfcqueue.h"
41 #include "urcu-call-rcu.h"
42 #include "urcu-pointer.h"
43 #include "urcu/list.h"
44 #include "urcu/futex.h"
45 #include "urcu/tls-compat.h"
49 #define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */
50 #define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1)
52 /* Data structure that identifies a call_rcu thread. */
54 struct call_rcu_data
{
56 * We do not align head on a different cache-line than tail
57 * mainly because call_rcu callback-invocation threads use
58 * batching ("splice") to get an entire list of callbacks, which
59 * effectively empties the queue, and requires to touch the tail
62 struct cds_wfcq_tail cbs_tail
;
63 struct cds_wfcq_head cbs_head
;
66 unsigned long qlen
; /* maintained for debugging. */
69 unsigned long gp_count
;
70 struct cds_list_head list
;
71 } __attribute__((aligned(CAA_CACHE_LINE_SIZE
)));
73 struct call_rcu_completion
{
79 struct call_rcu_completion_work
{
81 struct call_rcu_completion
*completion
;
85 * List of all call_rcu_data structures to keep valgrind happy.
86 * Protected by call_rcu_mutex.
89 static CDS_LIST_HEAD(call_rcu_data_list
);
91 /* Link a thread using call_rcu() to its call_rcu thread. */
93 static DEFINE_URCU_TLS(struct call_rcu_data
*, thread_call_rcu_data
);
96 * Guard call_rcu thread creation and atfork handlers.
98 static pthread_mutex_t call_rcu_mutex
= PTHREAD_MUTEX_INITIALIZER
;
100 /* If a given thread does not have its own call_rcu thread, this is default. */
102 static struct call_rcu_data
*default_call_rcu_data
;
104 static struct urcu_atfork
*registered_rculfhash_atfork
;
105 static unsigned long registered_rculfhash_atfork_refcount
;
108 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
109 * available, then we can have call_rcu threads assigned to individual
110 * CPUs rather than only to specific threads.
113 #if defined(HAVE_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID))
116 * Pointer to array of pointers to per-CPU call_rcu_data structures
117 * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an
118 * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a
119 * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer
120 * without mutex. The call_rcu_mutex protects updates.
123 static struct call_rcu_data
**per_cpu_call_rcu_data
;
126 static void maxcpus_reset(void)
131 /* Allocate the array if it has not already been allocated. */
133 static void alloc_cpu_call_rcu_data(void)
135 struct call_rcu_data
**p
;
136 static int warned
= 0;
140 maxcpus
= sysconf(_SC_NPROCESSORS_CONF
);
144 p
= malloc(maxcpus
* sizeof(*per_cpu_call_rcu_data
));
146 memset(p
, '\0', maxcpus
* sizeof(*per_cpu_call_rcu_data
));
147 rcu_set_pointer(&per_cpu_call_rcu_data
, p
);
150 fprintf(stderr
, "[error] liburcu: unable to allocate per-CPU pointer array\n");
156 #else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
159 * per_cpu_call_rcu_data should be constant, but some functions below, used both
160 * for cases where cpu number is available and not available, assume it it not
163 static struct call_rcu_data
**per_cpu_call_rcu_data
= NULL
;
164 static const long maxcpus
= -1;
166 static void maxcpus_reset(void)
170 static void alloc_cpu_call_rcu_data(void)
174 #endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
176 /* Acquire the specified pthread mutex. */
178 static void call_rcu_lock(pthread_mutex_t
*pmp
)
182 ret
= pthread_mutex_lock(pmp
);
187 /* Release the specified pthread mutex. */
189 static void call_rcu_unlock(pthread_mutex_t
*pmp
)
193 ret
= pthread_mutex_unlock(pmp
);
199 * Periodically retry setting CPU affinity if we migrate.
200 * Losing affinity can be caused by CPU hotunplug/hotplug, or by
203 #if HAVE_SCHED_SETAFFINITY
205 int set_thread_cpu_affinity(struct call_rcu_data
*crdp
)
210 if (crdp
->cpu_affinity
< 0)
212 if (++crdp
->gp_count
& SET_AFFINITY_CHECK_PERIOD_MASK
)
214 if (urcu_sched_getcpu() == crdp
->cpu_affinity
)
218 CPU_SET(crdp
->cpu_affinity
, &mask
);
219 #if SCHED_SETAFFINITY_ARGS == 2
220 ret
= sched_setaffinity(0, &mask
);
222 ret
= sched_setaffinity(0, sizeof(mask
), &mask
);
225 * EINVAL is fine: can be caused by hotunplugged CPUs, or by
226 * cpuset(7). This is why we should always retry if we detect
229 if (ret
&& errno
== EINVAL
) {
237 int set_thread_cpu_affinity(struct call_rcu_data
*crdp
)
243 static void call_rcu_wait(struct call_rcu_data
*crdp
)
245 /* Read call_rcu list before read futex */
247 if (uatomic_read(&crdp
->futex
) != -1)
249 while (futex_async(&crdp
->futex
, FUTEX_WAIT
, -1,
253 /* Value already changed. */
256 /* Retry if interrupted by signal. */
257 break; /* Get out of switch. */
259 /* Unexpected error. */
265 static void call_rcu_wake_up(struct call_rcu_data
*crdp
)
267 /* Write to call_rcu list before reading/writing futex */
269 if (caa_unlikely(uatomic_read(&crdp
->futex
) == -1)) {
270 uatomic_set(&crdp
->futex
, 0);
271 if (futex_async(&crdp
->futex
, FUTEX_WAKE
, 1,
277 static void call_rcu_completion_wait(struct call_rcu_completion
*completion
)
279 /* Read completion barrier count before read futex */
281 if (uatomic_read(&completion
->futex
) != -1)
283 while (futex_async(&completion
->futex
, FUTEX_WAIT
, -1,
287 /* Value already changed. */
290 /* Retry if interrupted by signal. */
291 break; /* Get out of switch. */
293 /* Unexpected error. */
299 static void call_rcu_completion_wake_up(struct call_rcu_completion
*completion
)
301 /* Write to completion barrier count before reading/writing futex */
303 if (caa_unlikely(uatomic_read(&completion
->futex
) == -1)) {
304 uatomic_set(&completion
->futex
, 0);
305 if (futex_async(&completion
->futex
, FUTEX_WAKE
, 1,
311 /* This is the code run by each call_rcu thread. */
313 static void *call_rcu_thread(void *arg
)
315 unsigned long cbcount
;
316 struct call_rcu_data
*crdp
= (struct call_rcu_data
*) arg
;
317 int rt
= !!(uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_RT
);
319 if (set_thread_cpu_affinity(crdp
))
323 * If callbacks take a read-side lock, we need to be registered.
325 rcu_register_thread();
327 URCU_TLS(thread_call_rcu_data
) = crdp
;
329 uatomic_dec(&crdp
->futex
);
330 /* Decrement futex before reading call_rcu list */
334 struct cds_wfcq_head cbs_tmp_head
;
335 struct cds_wfcq_tail cbs_tmp_tail
;
336 struct cds_wfcq_node
*cbs
, *cbs_tmp_n
;
337 enum cds_wfcq_ret splice_ret
;
339 if (set_thread_cpu_affinity(crdp
))
342 if (uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSE
) {
344 * Pause requested. Become quiescent: remove
345 * ourself from all global lists, and don't
346 * process any callback. The callback lists may
347 * still be non-empty though.
349 rcu_unregister_thread();
350 cmm_smp_mb__before_uatomic_or();
351 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_PAUSED
);
352 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSE
) != 0)
353 (void) poll(NULL
, 0, 1);
354 uatomic_and(&crdp
->flags
, ~URCU_CALL_RCU_PAUSED
);
355 cmm_smp_mb__after_uatomic_and();
356 rcu_register_thread();
359 cds_wfcq_init(&cbs_tmp_head
, &cbs_tmp_tail
);
360 splice_ret
= __cds_wfcq_splice_blocking(&cbs_tmp_head
,
361 &cbs_tmp_tail
, &crdp
->cbs_head
, &crdp
->cbs_tail
);
362 assert(splice_ret
!= CDS_WFCQ_RET_WOULDBLOCK
);
363 assert(splice_ret
!= CDS_WFCQ_RET_DEST_NON_EMPTY
);
364 if (splice_ret
!= CDS_WFCQ_RET_SRC_EMPTY
) {
367 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head
,
368 &cbs_tmp_tail
, cbs
, cbs_tmp_n
) {
369 struct rcu_head
*rhp
;
371 rhp
= caa_container_of(cbs
,
372 struct rcu_head
, next
);
376 uatomic_sub(&crdp
->qlen
, cbcount
);
378 if (uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOP
)
380 rcu_thread_offline();
382 if (cds_wfcq_empty(&crdp
->cbs_head
,
385 (void) poll(NULL
, 0, 10);
386 uatomic_dec(&crdp
->futex
);
388 * Decrement futex before reading
393 (void) poll(NULL
, 0, 10);
396 (void) poll(NULL
, 0, 10);
402 * Read call_rcu list before write futex.
405 uatomic_set(&crdp
->futex
, 0);
407 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_STOPPED
);
408 rcu_unregister_thread();
413 * Create both a call_rcu thread and the corresponding call_rcu_data
414 * structure, linking the structure in as specified. Caller must hold
418 static void call_rcu_data_init(struct call_rcu_data
**crdpp
,
422 struct call_rcu_data
*crdp
;
425 crdp
= malloc(sizeof(*crdp
));
428 memset(crdp
, '\0', sizeof(*crdp
));
429 cds_wfcq_init(&crdp
->cbs_head
, &crdp
->cbs_tail
);
433 cds_list_add(&crdp
->list
, &call_rcu_data_list
);
434 crdp
->cpu_affinity
= cpu_affinity
;
436 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
438 ret
= pthread_create(&crdp
->tid
, NULL
, call_rcu_thread
, crdp
);
444 * Return a pointer to the call_rcu_data structure for the specified
445 * CPU, returning NULL if there is none. We cannot automatically
446 * created it because the platform we are running on might not define
447 * urcu_sched_getcpu().
449 * The call to this function and use of the returned call_rcu_data
450 * should be protected by RCU read-side lock.
453 struct call_rcu_data
*get_cpu_call_rcu_data(int cpu
)
455 static int warned
= 0;
456 struct call_rcu_data
**pcpu_crdp
;
458 pcpu_crdp
= rcu_dereference(per_cpu_call_rcu_data
);
459 if (pcpu_crdp
== NULL
)
461 if (!warned
&& maxcpus
> 0 && (cpu
< 0 || maxcpus
<= cpu
)) {
462 fprintf(stderr
, "[error] liburcu: get CPU # out of range\n");
465 if (cpu
< 0 || maxcpus
<= cpu
)
467 return rcu_dereference(pcpu_crdp
[cpu
]);
471 * Return the tid corresponding to the call_rcu thread whose
472 * call_rcu_data structure is specified.
475 pthread_t
get_call_rcu_thread(struct call_rcu_data
*crdp
)
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 struct call_rcu_data
*create_call_rcu_data(unsigned long flags
,
496 struct call_rcu_data
*crdp
;
498 call_rcu_lock(&call_rcu_mutex
);
499 crdp
= __create_call_rcu_data(flags
, cpu_affinity
);
500 call_rcu_unlock(&call_rcu_mutex
);
505 * Set the specified CPU to use the specified call_rcu_data structure.
507 * Use NULL to remove a CPU's call_rcu_data structure, but it is
508 * the caller's responsibility to dispose of the removed structure.
509 * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
510 * (prior to NULLing it out, of course).
512 * The caller must wait for a grace-period to pass between return from
513 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
514 * previous call rcu data as argument.
517 int set_cpu_call_rcu_data(int cpu
, struct call_rcu_data
*crdp
)
519 static int warned
= 0;
521 call_rcu_lock(&call_rcu_mutex
);
522 alloc_cpu_call_rcu_data();
523 if (cpu
< 0 || maxcpus
<= cpu
) {
525 fprintf(stderr
, "[error] liburcu: set CPU # out of range\n");
528 call_rcu_unlock(&call_rcu_mutex
);
533 if (per_cpu_call_rcu_data
== NULL
) {
534 call_rcu_unlock(&call_rcu_mutex
);
539 if (per_cpu_call_rcu_data
[cpu
] != NULL
&& crdp
!= NULL
) {
540 call_rcu_unlock(&call_rcu_mutex
);
545 rcu_set_pointer(&per_cpu_call_rcu_data
[cpu
], crdp
);
546 call_rcu_unlock(&call_rcu_mutex
);
551 * Return a pointer to the default call_rcu_data structure, creating
552 * one if need be. Because we never free call_rcu_data structures,
553 * we don't need to be in an RCU read-side critical section.
556 struct call_rcu_data
*get_default_call_rcu_data(void)
558 if (default_call_rcu_data
!= NULL
)
559 return rcu_dereference(default_call_rcu_data
);
560 call_rcu_lock(&call_rcu_mutex
);
561 if (default_call_rcu_data
!= NULL
) {
562 call_rcu_unlock(&call_rcu_mutex
);
563 return default_call_rcu_data
;
565 call_rcu_data_init(&default_call_rcu_data
, 0, -1);
566 call_rcu_unlock(&call_rcu_mutex
);
567 return default_call_rcu_data
;
571 * Return the call_rcu_data structure that applies to the currently
572 * running thread. Any call_rcu_data structure assigned specifically
573 * to this thread has first priority, followed by any call_rcu_data
574 * structure assigned to the CPU on which the thread is running,
575 * followed by the default call_rcu_data structure. If there is not
576 * yet a default call_rcu_data structure, one will be created.
578 * Calls to this function and use of the returned call_rcu_data should
579 * be protected by RCU read-side lock.
581 struct call_rcu_data
*get_call_rcu_data(void)
583 struct call_rcu_data
*crd
;
585 if (URCU_TLS(thread_call_rcu_data
) != NULL
)
586 return URCU_TLS(thread_call_rcu_data
);
589 crd
= get_cpu_call_rcu_data(urcu_sched_getcpu());
594 return get_default_call_rcu_data();
598 * Return a pointer to this task's call_rcu_data if there is one.
601 struct call_rcu_data
*get_thread_call_rcu_data(void)
603 return URCU_TLS(thread_call_rcu_data
);
607 * Set this task's call_rcu_data structure as specified, regardless
608 * of whether or not this task already had one. (This allows switching
609 * to and from real-time call_rcu threads, for example.)
611 * Use NULL to remove a thread's call_rcu_data structure, but it is
612 * the caller's responsibility to dispose of the removed structure.
613 * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
614 * (prior to NULLing it out, of course).
617 void set_thread_call_rcu_data(struct call_rcu_data
*crdp
)
619 URCU_TLS(thread_call_rcu_data
) = crdp
;
623 * Create a separate call_rcu thread for each CPU. This does not
624 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
625 * function if you want that behavior. Should be paired with
626 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
630 int create_all_cpu_call_rcu_data(unsigned long flags
)
633 struct call_rcu_data
*crdp
;
636 call_rcu_lock(&call_rcu_mutex
);
637 alloc_cpu_call_rcu_data();
638 call_rcu_unlock(&call_rcu_mutex
);
643 if (per_cpu_call_rcu_data
== NULL
) {
647 for (i
= 0; i
< maxcpus
; i
++) {
648 call_rcu_lock(&call_rcu_mutex
);
649 if (get_cpu_call_rcu_data(i
)) {
650 call_rcu_unlock(&call_rcu_mutex
);
653 crdp
= __create_call_rcu_data(flags
, i
);
655 call_rcu_unlock(&call_rcu_mutex
);
659 call_rcu_unlock(&call_rcu_mutex
);
660 if ((ret
= set_cpu_call_rcu_data(i
, crdp
)) != 0) {
661 call_rcu_data_free(crdp
);
663 /* it has been created by other thread */
674 * Wake up the call_rcu thread corresponding to the specified
675 * call_rcu_data structure.
677 static void wake_call_rcu_thread(struct call_rcu_data
*crdp
)
679 if (!(_CMM_LOAD_SHARED(crdp
->flags
) & URCU_CALL_RCU_RT
))
680 call_rcu_wake_up(crdp
);
683 static void _call_rcu(struct rcu_head
*head
,
684 void (*func
)(struct rcu_head
*head
),
685 struct call_rcu_data
*crdp
)
687 cds_wfcq_node_init(&head
->next
);
689 cds_wfcq_enqueue(&crdp
->cbs_head
, &crdp
->cbs_tail
, &head
->next
);
690 uatomic_inc(&crdp
->qlen
);
691 wake_call_rcu_thread(crdp
);
695 * Schedule a function to be invoked after a following grace period.
696 * This is the only function that must be called -- the others are
697 * only present to allow applications to tune their use of RCU for
698 * maximum performance.
700 * Note that unless a call_rcu thread has not already been created,
701 * the first invocation of call_rcu() will create one. So, if you
702 * need the first invocation of call_rcu() to be fast, make sure
703 * to create a call_rcu thread first. One way to accomplish this is
704 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
706 * call_rcu must be called by registered RCU read-side threads.
708 void call_rcu(struct rcu_head
*head
,
709 void (*func
)(struct rcu_head
*head
))
711 struct call_rcu_data
*crdp
;
713 /* Holding rcu read-side lock across use of per-cpu crdp */
715 crdp
= get_call_rcu_data();
716 _call_rcu(head
, func
, crdp
);
721 * Free up the specified call_rcu_data structure, terminating the
722 * associated call_rcu thread. The caller must have previously
723 * removed the call_rcu_data structure from per-thread or per-CPU
724 * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
725 * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
726 * per-thread call_rcu_data structures.
728 * We silently refuse to free up the default call_rcu_data structure
729 * because that is where we put any leftover callbacks. Note that
730 * the possibility of self-spawning callbacks makes it impossible
731 * to execute all the callbacks in finite time without putting any
732 * newly spawned callbacks somewhere else. The "somewhere else" of
733 * last resort is the default call_rcu_data structure.
735 * We also silently refuse to free NULL pointers. This simplifies
738 * The caller must wait for a grace-period to pass between return from
739 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
740 * previous call rcu data as argument.
742 * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
743 * a list corruption bug in the 0.7.x series. The equivalent fix
744 * appeared in 0.6.8 for the stable-0.6 branch.
746 void call_rcu_data_free(struct call_rcu_data
*crdp
)
748 if (crdp
== NULL
|| crdp
== default_call_rcu_data
) {
751 if ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0) {
752 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_STOP
);
753 wake_call_rcu_thread(crdp
);
754 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0)
755 (void) poll(NULL
, 0, 1);
757 if (!cds_wfcq_empty(&crdp
->cbs_head
, &crdp
->cbs_tail
)) {
758 /* Create default call rcu data if need be */
759 (void) get_default_call_rcu_data();
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 call_rcu_lock(&call_rcu_mutex
);
769 cds_list_del(&crdp
->list
);
770 call_rcu_unlock(&call_rcu_mutex
);
776 * Clean up all the per-CPU call_rcu threads.
778 void free_all_cpu_call_rcu_data(void)
781 struct call_rcu_data
**crdp
;
782 static int warned
= 0;
787 crdp
= malloc(sizeof(*crdp
) * maxcpus
);
790 fprintf(stderr
, "[error] liburcu: unable to allocate per-CPU pointer array\n");
796 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
797 crdp
[cpu
] = get_cpu_call_rcu_data(cpu
);
798 if (crdp
[cpu
] == NULL
)
800 set_cpu_call_rcu_data(cpu
, NULL
);
803 * Wait for call_rcu sites acting as RCU readers of the
804 * call_rcu_data to become quiescent.
807 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
808 if (crdp
[cpu
] == NULL
)
810 call_rcu_data_free(crdp
[cpu
]);
816 void free_completion(struct urcu_ref
*ref
)
818 struct call_rcu_completion
*completion
;
820 completion
= caa_container_of(ref
, struct call_rcu_completion
, ref
);
825 void _rcu_barrier_complete(struct rcu_head
*head
)
827 struct call_rcu_completion_work
*work
;
828 struct call_rcu_completion
*completion
;
830 work
= caa_container_of(head
, struct call_rcu_completion_work
, head
);
831 completion
= work
->completion
;
832 if (!uatomic_sub_return(&completion
->barrier_count
, 1))
833 call_rcu_completion_wake_up(completion
);
834 urcu_ref_put(&completion
->ref
, free_completion
);
839 * Wait for all in-flight call_rcu callbacks to complete execution.
841 void rcu_barrier(void)
843 struct call_rcu_data
*crdp
;
844 struct call_rcu_completion
*completion
;
848 /* Put in offline state in QSBR. */
849 was_online
= _rcu_read_ongoing();
851 rcu_thread_offline();
853 * Calling a rcu_barrier() within a RCU read-side critical
854 * section is an error.
856 if (_rcu_read_ongoing()) {
857 static int warned
= 0;
860 fprintf(stderr
, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
866 completion
= calloc(sizeof(*completion
), 1);
870 call_rcu_lock(&call_rcu_mutex
);
871 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
874 /* Referenced by rcu_barrier() and each call_rcu thread. */
875 urcu_ref_set(&completion
->ref
, count
+ 1);
876 completion
->barrier_count
= count
;
878 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
879 struct call_rcu_completion_work
*work
;
881 work
= calloc(sizeof(*work
), 1);
884 work
->completion
= completion
;
885 _call_rcu(&work
->head
, _rcu_barrier_complete
, crdp
);
887 call_rcu_unlock(&call_rcu_mutex
);
891 uatomic_dec(&completion
->futex
);
892 /* Decrement futex before reading barrier_count */
894 if (!uatomic_read(&completion
->barrier_count
))
896 call_rcu_completion_wait(completion
);
899 urcu_ref_put(&completion
->ref
, free_completion
);
907 * Acquire the call_rcu_mutex in order to ensure that the child sees
908 * all of the call_rcu() data structures in a consistent state. Ensure
909 * that all call_rcu threads are in a quiescent state across fork.
910 * Suitable for pthread_atfork() and friends.
912 void call_rcu_before_fork(void)
914 struct call_rcu_data
*crdp
;
915 struct urcu_atfork
*atfork
;
917 call_rcu_lock(&call_rcu_mutex
);
919 atfork
= registered_rculfhash_atfork
;
921 atfork
->before_fork(atfork
->priv
);
923 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
924 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_PAUSE
);
925 cmm_smp_mb__after_uatomic_or();
926 wake_call_rcu_thread(crdp
);
928 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
929 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) == 0)
930 (void) poll(NULL
, 0, 1);
935 * Clean up call_rcu data structures in the parent of a successful fork()
936 * that is not followed by exec() in the child. Suitable for
937 * pthread_atfork() and friends.
939 void call_rcu_after_fork_parent(void)
941 struct call_rcu_data
*crdp
;
942 struct urcu_atfork
*atfork
;
944 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
945 uatomic_and(&crdp
->flags
, ~URCU_CALL_RCU_PAUSE
);
946 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
947 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) != 0)
948 (void) poll(NULL
, 0, 1);
950 atfork
= registered_rculfhash_atfork
;
952 atfork
->after_fork_parent(atfork
->priv
);
953 call_rcu_unlock(&call_rcu_mutex
);
957 * Clean up call_rcu data structures in the child of a successful fork()
958 * that is not followed by exec(). Suitable for pthread_atfork() and
961 void call_rcu_after_fork_child(void)
963 struct call_rcu_data
*crdp
, *next
;
964 struct urcu_atfork
*atfork
;
966 /* Release the mutex. */
967 call_rcu_unlock(&call_rcu_mutex
);
969 atfork
= registered_rculfhash_atfork
;
971 atfork
->after_fork_child(atfork
->priv
);
973 /* Do nothing when call_rcu() has not been used */
974 if (cds_list_empty(&call_rcu_data_list
))
978 * Allocate a new default call_rcu_data structure in order
979 * to get a working call_rcu thread to go with it.
981 default_call_rcu_data
= NULL
;
982 (void)get_default_call_rcu_data();
984 /* Cleanup call_rcu_data pointers before use */
986 free(per_cpu_call_rcu_data
);
987 rcu_set_pointer(&per_cpu_call_rcu_data
, NULL
);
988 URCU_TLS(thread_call_rcu_data
) = NULL
;
991 * Dispose of all of the rest of the call_rcu_data structures.
992 * Leftover call_rcu callbacks will be merged into the new
993 * default call_rcu thread queue.
995 cds_list_for_each_entry_safe(crdp
, next
, &call_rcu_data_list
, list
) {
996 if (crdp
== default_call_rcu_data
)
998 uatomic_set(&crdp
->flags
, URCU_CALL_RCU_STOPPED
);
999 call_rcu_data_free(crdp
);
1003 void urcu_register_rculfhash_atfork(struct urcu_atfork
*atfork
)
1005 call_rcu_lock(&call_rcu_mutex
);
1006 if (registered_rculfhash_atfork_refcount
++)
1008 registered_rculfhash_atfork
= atfork
;
1010 call_rcu_unlock(&call_rcu_mutex
);
1013 void urcu_unregister_rculfhash_atfork(struct urcu_atfork
*atfork
)
1015 call_rcu_lock(&call_rcu_mutex
);
1016 if (--registered_rculfhash_atfork_refcount
)
1018 registered_rculfhash_atfork
= NULL
;
1020 call_rcu_unlock(&call_rcu_mutex
);