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 #if SCHED_SETAFFINITY_ARGS == 2
219 ret
= sched_setaffinity(0, &mask
);
221 ret
= sched_setaffinity(0, sizeof(mask
), &mask
);
224 * EINVAL is fine: can be caused by hotunplugged CPUs, or by
225 * cpuset(7). This is why we should always retry if we detect
228 if (ret
&& errno
== EINVAL
) {
236 int set_thread_cpu_affinity(struct call_rcu_data
*crdp
)
242 static void call_rcu_wait(struct call_rcu_data
*crdp
)
244 /* Read call_rcu list before read futex */
246 if (uatomic_read(&crdp
->futex
) != -1)
248 while (futex_async(&crdp
->futex
, FUTEX_WAIT
, -1,
252 /* Value already changed. */
255 /* Retry if interrupted by signal. */
256 break; /* Get out of switch. */
258 /* Unexpected error. */
264 static void call_rcu_wake_up(struct call_rcu_data
*crdp
)
266 /* Write to call_rcu list before reading/writing futex */
268 if (caa_unlikely(uatomic_read(&crdp
->futex
) == -1)) {
269 uatomic_set(&crdp
->futex
, 0);
270 if (futex_async(&crdp
->futex
, FUTEX_WAKE
, 1,
276 static void call_rcu_completion_wait(struct call_rcu_completion
*completion
)
278 /* Read completion barrier count before read futex */
280 if (uatomic_read(&completion
->futex
) != -1)
282 while (futex_async(&completion
->futex
, FUTEX_WAIT
, -1,
286 /* Value already changed. */
289 /* Retry if interrupted by signal. */
290 break; /* Get out of switch. */
292 /* Unexpected error. */
298 static void call_rcu_completion_wake_up(struct call_rcu_completion
*completion
)
300 /* Write to completion barrier count before reading/writing futex */
302 if (caa_unlikely(uatomic_read(&completion
->futex
) == -1)) {
303 uatomic_set(&completion
->futex
, 0);
304 if (futex_async(&completion
->futex
, FUTEX_WAKE
, 1,
310 /* This is the code run by each call_rcu thread. */
312 static void *call_rcu_thread(void *arg
)
314 unsigned long cbcount
;
315 struct call_rcu_data
*crdp
= (struct call_rcu_data
*) arg
;
316 int rt
= !!(uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_RT
);
318 if (set_thread_cpu_affinity(crdp
))
322 * If callbacks take a read-side lock, we need to be registered.
324 rcu_register_thread();
326 URCU_TLS(thread_call_rcu_data
) = crdp
;
328 uatomic_dec(&crdp
->futex
);
329 /* Decrement futex before reading call_rcu list */
333 struct cds_wfcq_head cbs_tmp_head
;
334 struct cds_wfcq_tail cbs_tmp_tail
;
335 struct cds_wfcq_node
*cbs
, *cbs_tmp_n
;
336 enum cds_wfcq_ret splice_ret
;
338 if (set_thread_cpu_affinity(crdp
))
341 if (uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSE
) {
343 * Pause requested. Become quiescent: remove
344 * ourself from all global lists, and don't
345 * process any callback. The callback lists may
346 * still be non-empty though.
348 rcu_unregister_thread();
349 cmm_smp_mb__before_uatomic_or();
350 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_PAUSED
);
351 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSE
) != 0)
352 (void) poll(NULL
, 0, 1);
353 uatomic_and(&crdp
->flags
, ~URCU_CALL_RCU_PAUSED
);
354 cmm_smp_mb__after_uatomic_and();
355 rcu_register_thread();
358 cds_wfcq_init(&cbs_tmp_head
, &cbs_tmp_tail
);
359 splice_ret
= __cds_wfcq_splice_blocking(&cbs_tmp_head
,
360 &cbs_tmp_tail
, &crdp
->cbs_head
, &crdp
->cbs_tail
);
361 assert(splice_ret
!= CDS_WFCQ_RET_WOULDBLOCK
);
362 assert(splice_ret
!= CDS_WFCQ_RET_DEST_NON_EMPTY
);
363 if (splice_ret
!= CDS_WFCQ_RET_SRC_EMPTY
) {
366 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head
,
367 &cbs_tmp_tail
, cbs
, cbs_tmp_n
) {
368 struct rcu_head
*rhp
;
370 rhp
= caa_container_of(cbs
,
371 struct rcu_head
, next
);
375 uatomic_sub(&crdp
->qlen
, cbcount
);
377 if (uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOP
)
379 rcu_thread_offline();
381 if (cds_wfcq_empty(&crdp
->cbs_head
,
384 (void) poll(NULL
, 0, 10);
385 uatomic_dec(&crdp
->futex
);
387 * Decrement futex before reading
392 (void) poll(NULL
, 0, 10);
395 (void) poll(NULL
, 0, 10);
401 * Read call_rcu list before write futex.
404 uatomic_set(&crdp
->futex
, 0);
406 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_STOPPED
);
407 rcu_unregister_thread();
412 * Create both a call_rcu thread and the corresponding call_rcu_data
413 * structure, linking the structure in as specified. Caller must hold
417 static void call_rcu_data_init(struct call_rcu_data
**crdpp
,
421 struct call_rcu_data
*crdp
;
424 crdp
= malloc(sizeof(*crdp
));
427 memset(crdp
, '\0', sizeof(*crdp
));
428 cds_wfcq_init(&crdp
->cbs_head
, &crdp
->cbs_tail
);
432 cds_list_add(&crdp
->list
, &call_rcu_data_list
);
433 crdp
->cpu_affinity
= cpu_affinity
;
435 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
437 ret
= pthread_create(&crdp
->tid
, NULL
, call_rcu_thread
, crdp
);
443 * Return a pointer to the call_rcu_data structure for the specified
444 * CPU, returning NULL if there is none. We cannot automatically
445 * created it because the platform we are running on might not define
446 * urcu_sched_getcpu().
448 * The call to this function and use of the returned call_rcu_data
449 * should be protected by RCU read-side lock.
452 struct call_rcu_data
*get_cpu_call_rcu_data(int cpu
)
454 static int warned
= 0;
455 struct call_rcu_data
**pcpu_crdp
;
457 pcpu_crdp
= rcu_dereference(per_cpu_call_rcu_data
);
458 if (pcpu_crdp
== NULL
)
460 if (!warned
&& maxcpus
> 0 && (cpu
< 0 || maxcpus
<= cpu
)) {
461 fprintf(stderr
, "[error] liburcu: get CPU # out of range\n");
464 if (cpu
< 0 || maxcpus
<= cpu
)
466 return rcu_dereference(pcpu_crdp
[cpu
]);
468 URCU_ATTR_ALIAS(urcu_stringify(get_cpu_call_rcu_data
))
469 struct call_rcu_data
*alias_get_cpu_call_rcu_data();
472 * Return the tid corresponding to the call_rcu thread whose
473 * call_rcu_data structure is specified.
476 pthread_t
get_call_rcu_thread(struct call_rcu_data
*crdp
)
480 URCU_ATTR_ALIAS(urcu_stringify(get_call_rcu_thread
))
481 pthread_t
alias_get_call_rcu_thread();
484 * Create a call_rcu_data structure (with thread) and return a pointer.
487 static struct call_rcu_data
*__create_call_rcu_data(unsigned long flags
,
490 struct call_rcu_data
*crdp
;
492 call_rcu_data_init(&crdp
, flags
, cpu_affinity
);
496 URCU_ATTR_ALIAS(urcu_stringify(create_call_rcu_data
))
497 struct call_rcu_data
*alias_create_call_rcu_data();
498 struct call_rcu_data
*create_call_rcu_data(unsigned long flags
,
501 struct call_rcu_data
*crdp
;
503 call_rcu_lock(&call_rcu_mutex
);
504 crdp
= __create_call_rcu_data(flags
, cpu_affinity
);
505 call_rcu_unlock(&call_rcu_mutex
);
510 * Set the specified CPU to use the specified call_rcu_data structure.
512 * Use NULL to remove a CPU's call_rcu_data structure, but it is
513 * the caller's responsibility to dispose of the removed structure.
514 * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
515 * (prior to NULLing it out, of course).
517 * The caller must wait for a grace-period to pass between return from
518 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
519 * previous call rcu data as argument.
522 int set_cpu_call_rcu_data(int cpu
, struct call_rcu_data
*crdp
)
524 static int warned
= 0;
526 call_rcu_lock(&call_rcu_mutex
);
527 alloc_cpu_call_rcu_data();
528 if (cpu
< 0 || maxcpus
<= cpu
) {
530 fprintf(stderr
, "[error] liburcu: set CPU # out of range\n");
533 call_rcu_unlock(&call_rcu_mutex
);
538 if (per_cpu_call_rcu_data
== NULL
) {
539 call_rcu_unlock(&call_rcu_mutex
);
544 if (per_cpu_call_rcu_data
[cpu
] != NULL
&& crdp
!= NULL
) {
545 call_rcu_unlock(&call_rcu_mutex
);
550 rcu_set_pointer(&per_cpu_call_rcu_data
[cpu
], crdp
);
551 call_rcu_unlock(&call_rcu_mutex
);
554 URCU_ATTR_ALIAS(urcu_stringify(set_cpu_call_rcu_data
))
555 int alias_set_cpu_call_rcu_data();
558 * Return a pointer to the default call_rcu_data structure, creating
559 * one if need be. Because we never free call_rcu_data structures,
560 * we don't need to be in an RCU read-side critical section.
563 struct call_rcu_data
*get_default_call_rcu_data(void)
565 if (default_call_rcu_data
!= NULL
)
566 return rcu_dereference(default_call_rcu_data
);
567 call_rcu_lock(&call_rcu_mutex
);
568 if (default_call_rcu_data
!= NULL
) {
569 call_rcu_unlock(&call_rcu_mutex
);
570 return default_call_rcu_data
;
572 call_rcu_data_init(&default_call_rcu_data
, 0, -1);
573 call_rcu_unlock(&call_rcu_mutex
);
574 return default_call_rcu_data
;
576 URCU_ATTR_ALIAS(urcu_stringify(get_default_call_rcu_data
))
577 struct call_rcu_data
*alias_get_default_call_rcu_data();
580 * Return the call_rcu_data structure that applies to the currently
581 * running thread. Any call_rcu_data structure assigned specifically
582 * to this thread has first priority, followed by any call_rcu_data
583 * structure assigned to the CPU on which the thread is running,
584 * followed by the default call_rcu_data structure. If there is not
585 * yet a default call_rcu_data structure, one will be created.
587 * Calls to this function and use of the returned call_rcu_data should
588 * be protected by RCU read-side lock.
590 struct call_rcu_data
*get_call_rcu_data(void)
592 struct call_rcu_data
*crd
;
594 if (URCU_TLS(thread_call_rcu_data
) != NULL
)
595 return URCU_TLS(thread_call_rcu_data
);
598 crd
= get_cpu_call_rcu_data(urcu_sched_getcpu());
603 return get_default_call_rcu_data();
605 URCU_ATTR_ALIAS(urcu_stringify(get_call_rcu_data
))
606 struct call_rcu_data
*alias_get_call_rcu_data();
609 * Return a pointer to this task's call_rcu_data if there is one.
612 struct call_rcu_data
*get_thread_call_rcu_data(void)
614 return URCU_TLS(thread_call_rcu_data
);
616 URCU_ATTR_ALIAS(urcu_stringify(get_thread_call_rcu_data
))
617 struct call_rcu_data
*alias_get_thread_call_rcu_data();
620 * Set this task's call_rcu_data structure as specified, regardless
621 * of whether or not this task already had one. (This allows switching
622 * to and from real-time call_rcu threads, for example.)
624 * Use NULL to remove a thread's call_rcu_data structure, but it is
625 * the caller's responsibility to dispose of the removed structure.
626 * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
627 * (prior to NULLing it out, of course).
630 void set_thread_call_rcu_data(struct call_rcu_data
*crdp
)
632 URCU_TLS(thread_call_rcu_data
) = crdp
;
634 URCU_ATTR_ALIAS(urcu_stringify(set_thread_call_rcu_data
))
635 void alias_set_thread_call_rcu_data();
638 * Create a separate call_rcu thread for each CPU. This does not
639 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
640 * function if you want that behavior. Should be paired with
641 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
645 int create_all_cpu_call_rcu_data(unsigned long flags
)
648 struct call_rcu_data
*crdp
;
651 call_rcu_lock(&call_rcu_mutex
);
652 alloc_cpu_call_rcu_data();
653 call_rcu_unlock(&call_rcu_mutex
);
658 if (per_cpu_call_rcu_data
== NULL
) {
662 for (i
= 0; i
< maxcpus
; i
++) {
663 call_rcu_lock(&call_rcu_mutex
);
664 if (get_cpu_call_rcu_data(i
)) {
665 call_rcu_unlock(&call_rcu_mutex
);
668 crdp
= __create_call_rcu_data(flags
, i
);
670 call_rcu_unlock(&call_rcu_mutex
);
674 call_rcu_unlock(&call_rcu_mutex
);
675 if ((ret
= set_cpu_call_rcu_data(i
, crdp
)) != 0) {
676 call_rcu_data_free(crdp
);
678 /* it has been created by other thread */
687 URCU_ATTR_ALIAS(urcu_stringify(create_all_cpu_call_rcu_data
))
688 int alias_create_all_cpu_call_rcu_data();
691 * Wake up the call_rcu thread corresponding to the specified
692 * call_rcu_data structure.
694 static void wake_call_rcu_thread(struct call_rcu_data
*crdp
)
696 if (!(_CMM_LOAD_SHARED(crdp
->flags
) & URCU_CALL_RCU_RT
))
697 call_rcu_wake_up(crdp
);
700 static void _call_rcu(struct rcu_head
*head
,
701 void (*func
)(struct rcu_head
*head
),
702 struct call_rcu_data
*crdp
)
704 cds_wfcq_node_init(&head
->next
);
706 cds_wfcq_enqueue(&crdp
->cbs_head
, &crdp
->cbs_tail
, &head
->next
);
707 uatomic_inc(&crdp
->qlen
);
708 wake_call_rcu_thread(crdp
);
712 * Schedule a function to be invoked after a following grace period.
713 * This is the only function that must be called -- the others are
714 * only present to allow applications to tune their use of RCU for
715 * maximum performance.
717 * Note that unless a call_rcu thread has not already been created,
718 * the first invocation of call_rcu() will create one. So, if you
719 * need the first invocation of call_rcu() to be fast, make sure
720 * to create a call_rcu thread first. One way to accomplish this is
721 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
723 * call_rcu must be called by registered RCU read-side threads.
725 void call_rcu(struct rcu_head
*head
,
726 void (*func
)(struct rcu_head
*head
))
728 struct call_rcu_data
*crdp
;
730 /* Holding rcu read-side lock across use of per-cpu crdp */
732 crdp
= get_call_rcu_data();
733 _call_rcu(head
, func
, crdp
);
736 URCU_ATTR_ALIAS(urcu_stringify(call_rcu
)) void alias_call_rcu();
739 * Free up the specified call_rcu_data structure, terminating the
740 * associated call_rcu thread. The caller must have previously
741 * removed the call_rcu_data structure from per-thread or per-CPU
742 * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
743 * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
744 * per-thread call_rcu_data structures.
746 * We silently refuse to free up the default call_rcu_data structure
747 * because that is where we put any leftover callbacks. Note that
748 * the possibility of self-spawning callbacks makes it impossible
749 * to execute all the callbacks in finite time without putting any
750 * newly spawned callbacks somewhere else. The "somewhere else" of
751 * last resort is the default call_rcu_data structure.
753 * We also silently refuse to free NULL pointers. This simplifies
756 * The caller must wait for a grace-period to pass between return from
757 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
758 * previous call rcu data as argument.
760 * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
761 * a list corruption bug in the 0.7.x series. The equivalent fix
762 * appeared in 0.6.8 for the stable-0.6 branch.
764 void call_rcu_data_free(struct call_rcu_data
*crdp
)
766 if (crdp
== NULL
|| crdp
== default_call_rcu_data
) {
769 if ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0) {
770 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_STOP
);
771 wake_call_rcu_thread(crdp
);
772 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_STOPPED
) == 0)
773 (void) poll(NULL
, 0, 1);
775 call_rcu_lock(&call_rcu_mutex
);
776 if (!cds_wfcq_empty(&crdp
->cbs_head
, &crdp
->cbs_tail
)) {
777 call_rcu_unlock(&call_rcu_mutex
);
778 /* Create default call rcu data if need be. */
779 /* CBs queued here will be handed to the default list. */
780 (void) get_default_call_rcu_data();
781 call_rcu_lock(&call_rcu_mutex
);
782 __cds_wfcq_splice_blocking(&default_call_rcu_data
->cbs_head
,
783 &default_call_rcu_data
->cbs_tail
,
784 &crdp
->cbs_head
, &crdp
->cbs_tail
);
785 uatomic_add(&default_call_rcu_data
->qlen
,
786 uatomic_read(&crdp
->qlen
));
787 wake_call_rcu_thread(default_call_rcu_data
);
790 cds_list_del(&crdp
->list
);
791 call_rcu_unlock(&call_rcu_mutex
);
795 URCU_ATTR_ALIAS(urcu_stringify(call_rcu_data_free
))
796 void alias_call_rcu_data_free();
799 * Clean up all the per-CPU call_rcu threads.
801 void free_all_cpu_call_rcu_data(void)
804 struct call_rcu_data
**crdp
;
805 static int warned
= 0;
810 crdp
= malloc(sizeof(*crdp
) * maxcpus
);
813 fprintf(stderr
, "[error] liburcu: unable to allocate per-CPU pointer array\n");
819 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
820 crdp
[cpu
] = get_cpu_call_rcu_data(cpu
);
821 if (crdp
[cpu
] == NULL
)
823 set_cpu_call_rcu_data(cpu
, NULL
);
826 * Wait for call_rcu sites acting as RCU readers of the
827 * call_rcu_data to become quiescent.
830 for (cpu
= 0; cpu
< maxcpus
; cpu
++) {
831 if (crdp
[cpu
] == NULL
)
833 call_rcu_data_free(crdp
[cpu
]);
838 /* ABI6 has a non-namespaced free_all_cpu_call_rcu_data for qsbr */
839 #undef free_all_cpu_call_rcu_data
840 URCU_ATTR_ALIAS("urcu_qsbr_free_all_cpu_call_rcu_data")
841 void free_all_cpu_call_rcu_data();
842 #define free_all_cpu_call_rcu_data urcu_qsbr_free_all_cpu_call_rcu_data
844 URCU_ATTR_ALIAS(urcu_stringify(free_all_cpu_call_rcu_data
))
845 void alias_free_all_cpu_call_rcu_data();
849 void free_completion(struct urcu_ref
*ref
)
851 struct call_rcu_completion
*completion
;
853 completion
= caa_container_of(ref
, struct call_rcu_completion
, ref
);
858 void _rcu_barrier_complete(struct rcu_head
*head
)
860 struct call_rcu_completion_work
*work
;
861 struct call_rcu_completion
*completion
;
863 work
= caa_container_of(head
, struct call_rcu_completion_work
, head
);
864 completion
= work
->completion
;
865 if (!uatomic_sub_return(&completion
->barrier_count
, 1))
866 call_rcu_completion_wake_up(completion
);
867 urcu_ref_put(&completion
->ref
, free_completion
);
872 * Wait for all in-flight call_rcu callbacks to complete execution.
874 void rcu_barrier(void)
876 struct call_rcu_data
*crdp
;
877 struct call_rcu_completion
*completion
;
881 /* Put in offline state in QSBR. */
882 was_online
= _rcu_read_ongoing();
884 rcu_thread_offline();
886 * Calling a rcu_barrier() within a RCU read-side critical
887 * section is an error.
889 if (_rcu_read_ongoing()) {
890 static int warned
= 0;
893 fprintf(stderr
, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
899 completion
= calloc(sizeof(*completion
), 1);
903 call_rcu_lock(&call_rcu_mutex
);
904 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
907 /* Referenced by rcu_barrier() and each call_rcu thread. */
908 urcu_ref_set(&completion
->ref
, count
+ 1);
909 completion
->barrier_count
= count
;
911 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
912 struct call_rcu_completion_work
*work
;
914 work
= calloc(sizeof(*work
), 1);
917 work
->completion
= completion
;
918 _call_rcu(&work
->head
, _rcu_barrier_complete
, crdp
);
920 call_rcu_unlock(&call_rcu_mutex
);
924 uatomic_dec(&completion
->futex
);
925 /* Decrement futex before reading barrier_count */
927 if (!uatomic_read(&completion
->barrier_count
))
929 call_rcu_completion_wait(completion
);
932 urcu_ref_put(&completion
->ref
, free_completion
);
938 URCU_ATTR_ALIAS(urcu_stringify(rcu_barrier
))
939 void alias_rcu_barrier();
942 * Acquire the call_rcu_mutex in order to ensure that the child sees
943 * all of the call_rcu() data structures in a consistent state. Ensure
944 * that all call_rcu threads are in a quiescent state across fork.
945 * Suitable for pthread_atfork() and friends.
947 void call_rcu_before_fork(void)
949 struct call_rcu_data
*crdp
;
950 struct urcu_atfork
*atfork
;
952 call_rcu_lock(&call_rcu_mutex
);
954 atfork
= registered_rculfhash_atfork
;
956 atfork
->before_fork(atfork
->priv
);
958 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
959 uatomic_or(&crdp
->flags
, URCU_CALL_RCU_PAUSE
);
960 cmm_smp_mb__after_uatomic_or();
961 wake_call_rcu_thread(crdp
);
963 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
964 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) == 0)
965 (void) poll(NULL
, 0, 1);
968 URCU_ATTR_ALIAS(urcu_stringify(call_rcu_before_fork
))
969 void alias_call_rcu_before_fork();
972 * Clean up call_rcu data structures in the parent of a successful fork()
973 * that is not followed by exec() in the child. Suitable for
974 * pthread_atfork() and friends.
976 void call_rcu_after_fork_parent(void)
978 struct call_rcu_data
*crdp
;
979 struct urcu_atfork
*atfork
;
981 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
)
982 uatomic_and(&crdp
->flags
, ~URCU_CALL_RCU_PAUSE
);
983 cds_list_for_each_entry(crdp
, &call_rcu_data_list
, list
) {
984 while ((uatomic_read(&crdp
->flags
) & URCU_CALL_RCU_PAUSED
) != 0)
985 (void) poll(NULL
, 0, 1);
987 atfork
= registered_rculfhash_atfork
;
989 atfork
->after_fork_parent(atfork
->priv
);
990 call_rcu_unlock(&call_rcu_mutex
);
992 URCU_ATTR_ALIAS(urcu_stringify(call_rcu_after_fork_parent
))
993 void alias_call_rcu_after_fork_parent();
996 * Clean up call_rcu data structures in the child of a successful fork()
997 * that is not followed by exec(). Suitable for pthread_atfork() and
1000 void call_rcu_after_fork_child(void)
1002 struct call_rcu_data
*crdp
, *next
;
1003 struct urcu_atfork
*atfork
;
1005 /* Release the mutex. */
1006 call_rcu_unlock(&call_rcu_mutex
);
1008 atfork
= registered_rculfhash_atfork
;
1010 atfork
->after_fork_child(atfork
->priv
);
1012 /* Do nothing when call_rcu() has not been used */
1013 if (cds_list_empty(&call_rcu_data_list
))
1017 * Allocate a new default call_rcu_data structure in order
1018 * to get a working call_rcu thread to go with it.
1020 default_call_rcu_data
= NULL
;
1021 (void)get_default_call_rcu_data();
1023 /* Cleanup call_rcu_data pointers before use */
1025 free(per_cpu_call_rcu_data
);
1026 rcu_set_pointer(&per_cpu_call_rcu_data
, NULL
);
1027 URCU_TLS(thread_call_rcu_data
) = NULL
;
1030 * Dispose of all of the rest of the call_rcu_data structures.
1031 * Leftover call_rcu callbacks will be merged into the new
1032 * default call_rcu thread queue.
1034 cds_list_for_each_entry_safe(crdp
, next
, &call_rcu_data_list
, list
) {
1035 if (crdp
== default_call_rcu_data
)
1037 uatomic_set(&crdp
->flags
, URCU_CALL_RCU_STOPPED
);
1038 call_rcu_data_free(crdp
);
1041 URCU_ATTR_ALIAS(urcu_stringify(call_rcu_after_fork_child
))
1042 void alias_call_rcu_after_fork_child();
1044 void urcu_register_rculfhash_atfork(struct urcu_atfork
*atfork
)
1046 call_rcu_lock(&call_rcu_mutex
);
1047 if (registered_rculfhash_atfork_refcount
++)
1049 registered_rculfhash_atfork
= atfork
;
1051 call_rcu_unlock(&call_rcu_mutex
);
1053 URCU_ATTR_ALIAS(urcu_stringify(urcu_register_rculfhash_atfork
))
1054 void alias_urcu_register_rculfhash_atfork();
1056 void urcu_unregister_rculfhash_atfork(struct urcu_atfork
*atfork
)
1058 call_rcu_lock(&call_rcu_mutex
);
1059 if (--registered_rculfhash_atfork_refcount
)
1061 registered_rculfhash_atfork
= NULL
;
1063 call_rcu_unlock(&call_rcu_mutex
);
1065 URCU_ATTR_ALIAS(urcu_stringify(urcu_unregister_rculfhash_atfork
))
1066 void alias_urcu_unregister_rculfhash_atfork();