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
;
105 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
106 * available, then we can have call_rcu threads assigned to individual
107 * CPUs rather than only to specific threads.
110 #if defined(HAVE_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID))
113 * Pointer to array of pointers to per-CPU call_rcu_data structures
114 * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an
115 * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a
116 * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer
117 * without mutex. The call_rcu_mutex protects updates.
120 static struct call_rcu_data
**per_cpu_call_rcu_data
;
123 static void maxcpus_reset(void)
128 /* Allocate the array if it has not already been allocated. */
130 static void alloc_cpu_call_rcu_data(void)
132 struct call_rcu_data
**p
;
133 static int warned
= 0;
137 maxcpus
= sysconf(_SC_NPROCESSORS_CONF
);
141 p
= malloc(maxcpus
* sizeof(*per_cpu_call_rcu_data
));
143 memset(p
, '\0', maxcpus
* sizeof(*per_cpu_call_rcu_data
));
144 rcu_set_pointer(&per_cpu_call_rcu_data
, p
);
147 fprintf(stderr
, "[error] liburcu: unable to allocate per-CPU pointer array\n");
153 #else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
156 * per_cpu_call_rcu_data should be constant, but some functions below, used both
157 * for cases where cpu number is available and not available, assume it it not
160 static struct call_rcu_data
**per_cpu_call_rcu_data
= NULL
;
161 static const long maxcpus
= -1;
163 static void maxcpus_reset(void)
167 static void alloc_cpu_call_rcu_data(void)
171 #endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
173 /* Acquire the specified pthread mutex. */
175 static void call_rcu_lock(pthread_mutex_t
*pmp
)
179 ret
= pthread_mutex_lock(pmp
);
184 /* Release the specified pthread mutex. */
186 static void call_rcu_unlock(pthread_mutex_t
*pmp
)
190 ret
= pthread_mutex_unlock(pmp
);
196 * Periodically retry setting CPU affinity if we migrate.
197 * Losing affinity can be caused by CPU hotunplug/hotplug, or by
200 #if HAVE_SCHED_SETAFFINITY
202 int set_thread_cpu_affinity(struct call_rcu_data
*crdp
)
207 if (crdp
->cpu_affinity
< 0)
209 if (++crdp
->gp_count
& SET_AFFINITY_CHECK_PERIOD_MASK
)
211 if (urcu_sched_getcpu() == crdp
->cpu_affinity
)
215 CPU_SET(crdp
->cpu_affinity
, &mask
);
216 #if SCHED_SETAFFINITY_ARGS == 2
217 ret
= sched_setaffinity(0, &mask
);
219 ret
= sched_setaffinity(0, sizeof(mask
), &mask
);
222 * EINVAL is fine: can be caused by hotunplugged CPUs, or by
223 * cpuset(7). This is why we should always retry if we detect
226 if (ret
&& errno
== EINVAL
) {
234 int set_thread_cpu_affinity(struct call_rcu_data
*crdp
)
240 static void call_rcu_wait(struct call_rcu_data
*crdp
)
242 /* Read call_rcu list before read futex */
244 if (uatomic_read(&crdp
->futex
) != -1)
246 while (futex_async(&crdp
->futex
, FUTEX_WAIT
, -1,
250 /* Value already changed. */
253 /* Retry if interrupted by signal. */
254 break; /* Get out of switch. */
256 /* Unexpected error. */
262 static void call_rcu_wake_up(struct call_rcu_data
*crdp
)
264 /* Write to call_rcu list before reading/writing futex */
266 if (caa_unlikely(uatomic_read(&crdp
->futex
) == -1)) {
267 uatomic_set(&crdp
->futex
, 0);
268 if (futex_async(&crdp
->futex
, FUTEX_WAKE
, 1,
274 static void call_rcu_completion_wait(struct call_rcu_completion
*completion
)
276 /* Read completion barrier count before read futex */
278 if (uatomic_read(&completion
->futex
) != -1)
280 while (futex_async(&completion
->futex
, FUTEX_WAIT
, -1,
284 /* Value already changed. */
287 /* Retry if interrupted by signal. */
288 break; /* Get out of switch. */
290 /* Unexpected error. */
296 static void call_rcu_completion_wake_up(struct call_rcu_completion
*completion
)
298 /* Write to completion barrier count before reading/writing futex */
300 if (caa_unlikely(uatomic_read(&completion
->futex
) == -1)) {
301 uatomic_set(&completion
->futex
, 0);
302 if (futex_async(&completion
->futex
, FUTEX_WAKE
, 1,
308 /* This is the code run by each call_rcu thread. */
310 static void *call_rcu_thread(void *arg
)
312 unsigned long cbcount
;
313 struct call_rcu_data
*crdp
= (struct call_rcu_data
*) arg
;
314 int rt
= !!(uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_RT
);
316 if (set_thread_cpu_affinity(crdp
))
320 * If callbacks take a read-side lock, we need to be registered.
322 rcu_register_thread();
324 URCU_TLS(thread_call_rcu_data
) = crdp
;
326 uatomic_dec(&crdp
->futex
);
327 /* Decrement futex before reading call_rcu list */
331 struct cds_wfcq_head cbs_tmp_head
;
332 struct cds_wfcq_tail cbs_tmp_tail
;
333 struct cds_wfcq_node
*cbs
, *cbs_tmp_n
;
334 enum cds_wfcq_ret splice_ret
;
336 if (set_thread_cpu_affinity(crdp
))
339 if (uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSE
) {
341 * Pause requested. Become quiescent: remove
342 * ourself from all global lists, and don't
343 * process any callback. The callback lists may
344 * still be non-empty though.
346 rcu_unregister_thread();
347 cmm_smp_mb__before_uatomic_or();
348 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_PAUSED
);
349 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSE
) != 0)
350 (void) poll(NULL
, 0, 1);
351 uatomic_and(&crdp
->flags
, ~URCU_CALL_RCU_PAUSED
);
352 cmm_smp_mb__after_uatomic_and();
353 rcu_register_thread();
356 cds_wfcq_init(&cbs_tmp_head
, &cbs_tmp_tail
);
357 splice_ret
= __cds_wfcq_splice_blocking(&cbs_tmp_head
,
358 &cbs_tmp_tail
, &crdp
->cbs_head
, &crdp
->cbs_tail
);
359 assert(splice_ret
!= CDS_WFCQ_RET_WOULDBLOCK
);
360 assert(splice_ret
!= CDS_WFCQ_RET_DEST_NON_EMPTY
);
361 if (splice_ret
!= CDS_WFCQ_RET_SRC_EMPTY
) {
364 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head
,
365 &cbs_tmp_tail
, cbs
, cbs_tmp_n
) {
366 struct rcu_head
*rhp
;
368 rhp
= caa_container_of(cbs
,
369 struct rcu_head
, next
);
373 uatomic_sub(&crdp
->qlen
, cbcount
);
375 if (uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOP
)
377 rcu_thread_offline();
379 if (cds_wfcq_empty(&crdp
->cbs_head
,
382 (void) poll(NULL
, 0, 10);
383 uatomic_dec(&crdp
->futex
);
385 * Decrement futex before reading
390 (void) poll(NULL
, 0, 10);
393 (void) poll(NULL
, 0, 10);
399 * Read call_rcu list before write futex.
402 uatomic_set(&crdp
->futex
, 0);
404 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_STOPPED
);
405 rcu_unregister_thread();
410 * Create both a call_rcu thread and the corresponding call_rcu_data
411 * structure, linking the structure in as specified. Caller must hold
415 static void call_rcu_data_init(struct call_rcu_data
**crdpp
,
419 struct call_rcu_data
*crdp
;
422 crdp
= malloc(sizeof(*crdp
));
425 memset(crdp
, '\0', sizeof(*crdp
));
426 cds_wfcq_init(&crdp
->cbs_head
, &crdp
->cbs_tail
);
430 cds_list_add(&crdp
->list
, &call_rcu_data_list
);
431 crdp
->cpu_affinity
= cpu_affinity
;
433 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
435 ret
= pthread_create(&crdp
->tid
, NULL
, call_rcu_thread
, crdp
);
441 * Return a pointer to the call_rcu_data structure for the specified
442 * CPU, returning NULL if there is none. We cannot automatically
443 * created it because the platform we are running on might not define
444 * urcu_sched_getcpu().
446 * The call to this function and use of the returned call_rcu_data
447 * should be protected by RCU read-side lock.
450 struct call_rcu_data
*get_cpu_call_rcu_data(int cpu
)
452 static int warned
= 0;
453 struct call_rcu_data
**pcpu_crdp
;
455 pcpu_crdp
= rcu_dereference(per_cpu_call_rcu_data
);
456 if (pcpu_crdp
== NULL
)
458 if (!warned
&& maxcpus
> 0 && (cpu
< 0 || maxcpus
<= cpu
)) {
459 fprintf(stderr
, "[error] liburcu: get CPU # out of range\n");
462 if (cpu
< 0 || maxcpus
<= cpu
)
464 return rcu_dereference(pcpu_crdp
[cpu
]);
468 * Return the tid corresponding to the call_rcu thread whose
469 * call_rcu_data structure is specified.
472 pthread_t
get_call_rcu_thread(struct call_rcu_data
*crdp
)
478 * Create a call_rcu_data structure (with thread) and return a pointer.
481 static struct call_rcu_data
*__create_call_rcu_data(unsigned long flags
,
484 struct call_rcu_data
*crdp
;
486 call_rcu_data_init(&crdp
, flags
, cpu_affinity
);
490 struct call_rcu_data
*create_call_rcu_data(unsigned long flags
,
493 struct call_rcu_data
*crdp
;
495 call_rcu_lock(&call_rcu_mutex
);
496 crdp
= __create_call_rcu_data(flags
, cpu_affinity
);
497 call_rcu_unlock(&call_rcu_mutex
);
502 * Set the specified CPU to use the specified call_rcu_data structure.
504 * Use NULL to remove a CPU's call_rcu_data structure, but it is
505 * the caller's responsibility to dispose of the removed structure.
506 * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
507 * (prior to NULLing it out, of course).
509 * The caller must wait for a grace-period to pass between return from
510 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
511 * previous call rcu data as argument.
514 int set_cpu_call_rcu_data(int cpu
, struct call_rcu_data
*crdp
)
516 static int warned
= 0;
518 call_rcu_lock(&call_rcu_mutex
);
519 alloc_cpu_call_rcu_data();
520 if (cpu
< 0 || maxcpus
<= cpu
) {
522 fprintf(stderr
, "[error] liburcu: set CPU # out of range\n");
525 call_rcu_unlock(&call_rcu_mutex
);
530 if (per_cpu_call_rcu_data
== NULL
) {
531 call_rcu_unlock(&call_rcu_mutex
);
536 if (per_cpu_call_rcu_data
[cpu
] != NULL
&& crdp
!= NULL
) {
537 call_rcu_unlock(&call_rcu_mutex
);
542 rcu_set_pointer(&per_cpu_call_rcu_data
[cpu
], crdp
);
543 call_rcu_unlock(&call_rcu_mutex
);
548 * Return a pointer to the default call_rcu_data structure, creating
549 * one if need be. Because we never free call_rcu_data structures,
550 * we don't need to be in an RCU read-side critical section.
553 struct call_rcu_data
*get_default_call_rcu_data(void)
555 if (default_call_rcu_data
!= NULL
)
556 return rcu_dereference(default_call_rcu_data
);
557 call_rcu_lock(&call_rcu_mutex
);
558 if (default_call_rcu_data
!= NULL
) {
559 call_rcu_unlock(&call_rcu_mutex
);
560 return default_call_rcu_data
;
562 call_rcu_data_init(&default_call_rcu_data
, 0, -1);
563 call_rcu_unlock(&call_rcu_mutex
);
564 return default_call_rcu_data
;
568 * Return the call_rcu_data structure that applies to the currently
569 * running thread. Any call_rcu_data structure assigned specifically
570 * to this thread has first priority, followed by any call_rcu_data
571 * structure assigned to the CPU on which the thread is running,
572 * followed by the default call_rcu_data structure. If there is not
573 * yet a default call_rcu_data structure, one will be created.
575 * Calls to this function and use of the returned call_rcu_data should
576 * be protected by RCU read-side lock.
578 struct call_rcu_data
*get_call_rcu_data(void)
580 struct call_rcu_data
*crd
;
582 if (URCU_TLS(thread_call_rcu_data
) != NULL
)
583 return URCU_TLS(thread_call_rcu_data
);
586 crd
= get_cpu_call_rcu_data(urcu_sched_getcpu());
591 return get_default_call_rcu_data();
595 * Return a pointer to this task's call_rcu_data if there is one.
598 struct call_rcu_data
*get_thread_call_rcu_data(void)
600 return URCU_TLS(thread_call_rcu_data
);
604 * Set this task's call_rcu_data structure as specified, regardless
605 * of whether or not this task already had one. (This allows switching
606 * to and from real-time call_rcu threads, for example.)
608 * Use NULL to remove a thread's call_rcu_data structure, but it is
609 * the caller's responsibility to dispose of the removed structure.
610 * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
611 * (prior to NULLing it out, of course).
614 void set_thread_call_rcu_data(struct call_rcu_data
*crdp
)
616 URCU_TLS(thread_call_rcu_data
) = crdp
;
620 * Create a separate call_rcu thread for each CPU. This does not
621 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
622 * function if you want that behavior. Should be paired with
623 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
627 int create_all_cpu_call_rcu_data(unsigned long flags
)
630 struct call_rcu_data
*crdp
;
633 call_rcu_lock(&call_rcu_mutex
);
634 alloc_cpu_call_rcu_data();
635 call_rcu_unlock(&call_rcu_mutex
);
640 if (per_cpu_call_rcu_data
== NULL
) {
644 for (i
= 0; i
< maxcpus
; i
++) {
645 call_rcu_lock(&call_rcu_mutex
);
646 if (get_cpu_call_rcu_data(i
)) {
647 call_rcu_unlock(&call_rcu_mutex
);
650 crdp
= __create_call_rcu_data(flags
, i
);
652 call_rcu_unlock(&call_rcu_mutex
);
656 call_rcu_unlock(&call_rcu_mutex
);
657 if ((ret
= set_cpu_call_rcu_data(i
, crdp
)) != 0) {
658 call_rcu_data_free(crdp
);
660 /* it has been created by other thread */
671 * Wake up the call_rcu thread corresponding to the specified
672 * call_rcu_data structure.
674 static void wake_call_rcu_thread(struct call_rcu_data
*crdp
)
676 if (!(_CMM_LOAD_SHARED(crdp
->flags
) & URCU_CALL_RCU_RT
))
677 call_rcu_wake_up(crdp
);
680 static void _call_rcu(struct rcu_head
*head
,
681 void (*func
)(struct rcu_head
*head
),
682 struct call_rcu_data
*crdp
)
684 cds_wfcq_node_init(&head
->next
);
686 cds_wfcq_enqueue(&crdp
->cbs_head
, &crdp
->cbs_tail
, &head
->next
);
687 uatomic_inc(&crdp
->qlen
);
688 wake_call_rcu_thread(crdp
);
692 * Schedule a function to be invoked after a following grace period.
693 * This is the only function that must be called -- the others are
694 * only present to allow applications to tune their use of RCU for
695 * maximum performance.
697 * Note that unless a call_rcu thread has not already been created,
698 * the first invocation of call_rcu() will create one. So, if you
699 * need the first invocation of call_rcu() to be fast, make sure
700 * to create a call_rcu thread first. One way to accomplish this is
701 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
703 * call_rcu must be called by registered RCU read-side threads.
705 void call_rcu(struct rcu_head
*head
,
706 void (*func
)(struct rcu_head
*head
))
708 struct call_rcu_data
*crdp
;
710 /* Holding rcu read-side lock across use of per-cpu crdp */
712 crdp
= get_call_rcu_data();
713 _call_rcu(head
, func
, crdp
);
718 * Free up the specified call_rcu_data structure, terminating the
719 * associated call_rcu thread. The caller must have previously
720 * removed the call_rcu_data structure from per-thread or per-CPU
721 * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
722 * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
723 * per-thread call_rcu_data structures.
725 * We silently refuse to free up the default call_rcu_data structure
726 * because that is where we put any leftover callbacks. Note that
727 * the possibility of self-spawning callbacks makes it impossible
728 * to execute all the callbacks in finite time without putting any
729 * newly spawned callbacks somewhere else. The "somewhere else" of
730 * last resort is the default call_rcu_data structure.
732 * We also silently refuse to free NULL pointers. This simplifies
735 * The caller must wait for a grace-period to pass between return from
736 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
737 * previous call rcu data as argument.
739 * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
740 * a list corruption bug in the 0.7.x series. The equivalent fix
741 * appeared in 0.6.8 for the stable-0.6 branch.
743 void call_rcu_data_free(struct call_rcu_data
*crdp
)
745 if (crdp
== NULL
|| crdp
== default_call_rcu_data
) {
748 if ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0) {
749 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_STOP
);
750 wake_call_rcu_thread(crdp
);
751 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0)
752 (void) poll(NULL
, 0, 1);
754 if (!cds_wfcq_empty(&crdp
->cbs_head
, &crdp
->cbs_tail
)) {
755 /* Create default call rcu data if need be */
756 (void) get_default_call_rcu_data();
757 __cds_wfcq_splice_blocking(&default_call_rcu_data
->cbs_head
,
758 &default_call_rcu_data
->cbs_tail
,
759 &crdp
->cbs_head
, &crdp
->cbs_tail
);
760 uatomic_add(&default_call_rcu_data
->qlen
,
761 uatomic_read(&crdp
->qlen
));
762 wake_call_rcu_thread(default_call_rcu_data
);
765 call_rcu_lock(&call_rcu_mutex
);
766 cds_list_del(&crdp
->list
);
767 call_rcu_unlock(&call_rcu_mutex
);
773 * Clean up all the per-CPU call_rcu threads.
775 void free_all_cpu_call_rcu_data(void)
778 struct call_rcu_data
**crdp
;
779 static int warned
= 0;
784 crdp
= malloc(sizeof(*crdp
) * maxcpus
);
787 fprintf(stderr
, "[error] liburcu: unable to allocate per-CPU pointer array\n");
793 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
794 crdp
[cpu
] = get_cpu_call_rcu_data(cpu
);
795 if (crdp
[cpu
] == NULL
)
797 set_cpu_call_rcu_data(cpu
, NULL
);
800 * Wait for call_rcu sites acting as RCU readers of the
801 * call_rcu_data to become quiescent.
804 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
805 if (crdp
[cpu
] == NULL
)
807 call_rcu_data_free(crdp
[cpu
]);
813 void free_completion(struct urcu_ref
*ref
)
815 struct call_rcu_completion
*completion
;
817 completion
= caa_container_of(ref
, struct call_rcu_completion
, ref
);
822 void _rcu_barrier_complete(struct rcu_head
*head
)
824 struct call_rcu_completion_work
*work
;
825 struct call_rcu_completion
*completion
;
827 work
= caa_container_of(head
, struct call_rcu_completion_work
, head
);
828 completion
= work
->completion
;
829 if (!uatomic_sub_return(&completion
->barrier_count
, 1))
830 call_rcu_completion_wake_up(completion
);
831 urcu_ref_put(&completion
->ref
, free_completion
);
836 * Wait for all in-flight call_rcu callbacks to complete execution.
838 void rcu_barrier(void)
840 struct call_rcu_data
*crdp
;
841 struct call_rcu_completion
*completion
;
845 /* Put in offline state in QSBR. */
846 was_online
= _rcu_read_ongoing();
848 rcu_thread_offline();
850 * Calling a rcu_barrier() within a RCU read-side critical
851 * section is an error.
853 if (_rcu_read_ongoing()) {
854 static int warned
= 0;
857 fprintf(stderr
, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
863 completion
= calloc(sizeof(*completion
), 1);
867 call_rcu_lock(&call_rcu_mutex
);
868 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
871 /* Referenced by rcu_barrier() and each call_rcu thread. */
872 urcu_ref_set(&completion
->ref
, count
+ 1);
873 completion
->barrier_count
= count
;
875 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
876 struct call_rcu_completion_work
*work
;
878 work
= calloc(sizeof(*work
), 1);
881 work
->completion
= completion
;
882 _call_rcu(&work
->head
, _rcu_barrier_complete
, crdp
);
884 call_rcu_unlock(&call_rcu_mutex
);
888 uatomic_dec(&completion
->futex
);
889 /* Decrement futex before reading barrier_count */
891 if (!uatomic_read(&completion
->barrier_count
))
893 call_rcu_completion_wait(completion
);
896 urcu_ref_put(&completion
->ref
, free_completion
);
904 * Acquire the call_rcu_mutex in order to ensure that the child sees
905 * all of the call_rcu() data structures in a consistent state. Ensure
906 * that all call_rcu threads are in a quiescent state across fork.
907 * Suitable for pthread_atfork() and friends.
909 void call_rcu_before_fork(void)
911 struct call_rcu_data
*crdp
;
913 call_rcu_lock(&call_rcu_mutex
);
915 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
916 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_PAUSE
);
917 cmm_smp_mb__after_uatomic_or();
918 wake_call_rcu_thread(crdp
);
920 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
921 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) == 0)
922 (void) poll(NULL
, 0, 1);
927 * Clean up call_rcu data structures in the parent of a successful fork()
928 * that is not followed by exec() in the child. Suitable for
929 * pthread_atfork() and friends.
931 void call_rcu_after_fork_parent(void)
933 struct call_rcu_data
*crdp
;
935 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
936 uatomic_and(&crdp
->flags
, ~URCU_CALL_RCU_PAUSE
);
937 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
938 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) != 0)
939 (void) poll(NULL
, 0, 1);
941 call_rcu_unlock(&call_rcu_mutex
);
945 * Clean up call_rcu data structures in the child of a successful fork()
946 * that is not followed by exec(). Suitable for pthread_atfork() and
949 void call_rcu_after_fork_child(void)
951 struct call_rcu_data
*crdp
, *next
;
953 /* Release the mutex. */
954 call_rcu_unlock(&call_rcu_mutex
);
956 /* Do nothing when call_rcu() has not been used */
957 if (cds_list_empty(&call_rcu_data_list
))
961 * Allocate a new default call_rcu_data structure in order
962 * to get a working call_rcu thread to go with it.
964 default_call_rcu_data
= NULL
;
965 (void)get_default_call_rcu_data();
967 /* Cleanup call_rcu_data pointers before use */
969 free(per_cpu_call_rcu_data
);
970 rcu_set_pointer(&per_cpu_call_rcu_data
, NULL
);
971 URCU_TLS(thread_call_rcu_data
) = NULL
;
974 * Dispose of all of the rest of the call_rcu_data structures.
975 * Leftover call_rcu callbacks will be merged into the new
976 * default call_rcu thread queue.
978 cds_list_for_each_entry_safe(crdp
, next
, &call_rcu_data_list
, list
) {
979 if (crdp
== default_call_rcu_data
)
981 uatomic_set(&crdp
->flags
, URCU_CALL_RCU_STOPPED
);
982 call_rcu_data_free(crdp
);