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[urcu.git] / src / urcu-call-rcu-impl.h
CommitLineData
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1/*
2 * urcu-call-rcu.c
3 *
4 * Userspace RCU library - batch memory reclamation with kernel API
5 *
6 * Copyright (c) 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com>
7 *
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.
12 *
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.
17 *
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
21 */
22
5161f31e 23#define _LGPL_SOURCE
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24#include <stdio.h>
25#include <pthread.h>
26#include <signal.h>
27#include <assert.h>
28#include <stdlib.h>
6d841bc2 29#include <stdint.h>
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30#include <string.h>
31#include <errno.h>
32#include <poll.h>
33#include <sys/time.h>
b57aee66 34#include <unistd.h>
c1d2c60b 35#include <sched.h>
b57aee66 36
a47dd11c 37#include "compat-getcpu.h"
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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>
44#include <urcu/ref.h>
4a6d7378 45#include "urcu-die.h"
4477a870 46#include "urcu-utils.h"
b57aee66 47
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48#define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */
49#define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1)
50
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51/* Data structure that identifies a call_rcu thread. */
52
53struct call_rcu_data {
5161f31e 54 /*
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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
59 * anyway.
5161f31e 60 */
b9f893b6 61 struct cds_wfcq_tail cbs_tail;
0b8ab7df 62 struct cds_wfcq_head cbs_head;
b57aee66 63 unsigned long flags;
6d841bc2 64 int32_t futex;
73987721 65 unsigned long qlen; /* maintained for debugging. */
b57aee66 66 pthread_t tid;
c1d2c60b 67 int cpu_affinity;
8e3690db 68 unsigned long gp_count;
3c24913f 69 struct cds_list_head list;
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70} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
71
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72struct call_rcu_completion {
73 int barrier_count;
74 int32_t futex;
81dd9134 75 struct urcu_ref ref;
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76};
77
78struct call_rcu_completion_work {
79 struct rcu_head head;
80 struct call_rcu_completion *completion;
81};
82
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83/*
84 * List of all call_rcu_data structures to keep valgrind happy.
85 * Protected by call_rcu_mutex.
86 */
87
bab44e28 88static CDS_LIST_HEAD(call_rcu_data_list);
3c24913f 89
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90/* Link a thread using call_rcu() to its call_rcu thread. */
91
2f661865 92static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data);
b57aee66 93
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94/*
95 * Guard call_rcu thread creation and atfork handlers.
96 */
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97static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
98
99/* If a given thread does not have its own call_rcu thread, this is default. */
100
101static struct call_rcu_data *default_call_rcu_data;
102
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103static struct urcu_atfork *registered_rculfhash_atfork;
104static unsigned long registered_rculfhash_atfork_refcount;
105
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106/*
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.
110 */
111
a47dd11c 112#if defined(HAVE_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID))
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113
114/*
115 * Pointer to array of pointers to per-CPU call_rcu_data structures
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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.
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120 */
121
122static struct call_rcu_data **per_cpu_call_rcu_data;
123static long maxcpus;
124
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125static void maxcpus_reset(void)
126{
127 maxcpus = 0;
128}
129
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130/* Allocate the array if it has not already been allocated. */
131
132static void alloc_cpu_call_rcu_data(void)
133{
134 struct call_rcu_data **p;
135 static int warned = 0;
136
137 if (maxcpus != 0)
138 return;
139 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
140 if (maxcpus <= 0) {
141 return;
142 }
143 p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data));
144 if (p != NULL) {
145 memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data));
618b2595 146 rcu_set_pointer(&per_cpu_call_rcu_data, p);
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147 } else {
148 if (!warned) {
149 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
150 }
151 warned = 1;
152 }
153}
154
63b495d8 155#else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
b57aee66 156
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157/*
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
160 * constant.
161 */
162static struct call_rcu_data **per_cpu_call_rcu_data = NULL;
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163static const long maxcpus = -1;
164
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165static void maxcpus_reset(void)
166{
167}
168
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169static void alloc_cpu_call_rcu_data(void)
170{
171}
172
63b495d8 173#endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
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174
175/* Acquire the specified pthread mutex. */
176
177static void call_rcu_lock(pthread_mutex_t *pmp)
178{
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179 int ret;
180
181 ret = pthread_mutex_lock(pmp);
182 if (ret)
183 urcu_die(ret);
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184}
185
186/* Release the specified pthread mutex. */
187
188static void call_rcu_unlock(pthread_mutex_t *pmp)
189{
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190 int ret;
191
192 ret = pthread_mutex_unlock(pmp);
193 if (ret)
194 urcu_die(ret);
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195}
196
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197/*
198 * Periodically retry setting CPU affinity if we migrate.
199 * Losing affinity can be caused by CPU hotunplug/hotplug, or by
200 * cpuset(7).
201 */
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202#if HAVE_SCHED_SETAFFINITY
203static
204int set_thread_cpu_affinity(struct call_rcu_data *crdp)
205{
206 cpu_set_t mask;
8e3690db 207 int ret;
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208
209 if (crdp->cpu_affinity < 0)
210 return 0;
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211 if (++crdp->gp_count & SET_AFFINITY_CHECK_PERIOD_MASK)
212 return 0;
213 if (urcu_sched_getcpu() == crdp->cpu_affinity)
214 return 0;
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215
216 CPU_ZERO(&mask);
217 CPU_SET(crdp->cpu_affinity, &mask);
218#if SCHED_SETAFFINITY_ARGS == 2
8e3690db 219 ret = sched_setaffinity(0, &mask);
c1d2c60b 220#else
8e3690db 221 ret = sched_setaffinity(0, sizeof(mask), &mask);
c1d2c60b 222#endif
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223 /*
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
226 * migration.
227 */
228 if (ret && errno == EINVAL) {
229 ret = 0;
230 errno = 0;
231 }
232 return ret;
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233}
234#else
235static
236int set_thread_cpu_affinity(struct call_rcu_data *crdp)
237{
238 return 0;
239}
240#endif
241
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242static void call_rcu_wait(struct call_rcu_data *crdp)
243{
244 /* Read call_rcu list before read futex */
245 cmm_smp_mb();
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246 if (uatomic_read(&crdp->futex) != -1)
247 return;
248 while (futex_async(&crdp->futex, FUTEX_WAIT, -1,
249 NULL, NULL, 0)) {
250 switch (errno) {
251 case EWOULDBLOCK:
252 /* Value already changed. */
253 return;
254 case EINTR:
255 /* Retry if interrupted by signal. */
256 break; /* Get out of switch. */
257 default:
258 /* Unexpected error. */
259 urcu_die(errno);
260 }
261 }
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262}
263
264static void call_rcu_wake_up(struct call_rcu_data *crdp)
265{
266 /* Write to call_rcu list before reading/writing futex */
267 cmm_smp_mb();
a0b7f7ea 268 if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) {
03fe58b3 269 uatomic_set(&crdp->futex, 0);
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270 if (futex_async(&crdp->futex, FUTEX_WAKE, 1,
271 NULL, NULL, 0) < 0)
272 urcu_die(errno);
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273 }
274}
275
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276static void call_rcu_completion_wait(struct call_rcu_completion *completion)
277{
278 /* Read completion barrier count before read futex */
279 cmm_smp_mb();
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280 if (uatomic_read(&completion->futex) != -1)
281 return;
282 while (futex_async(&completion->futex, FUTEX_WAIT, -1,
283 NULL, NULL, 0)) {
284 switch (errno) {
285 case EWOULDBLOCK:
286 /* Value already changed. */
287 return;
288 case EINTR:
289 /* Retry if interrupted by signal. */
290 break; /* Get out of switch. */
291 default:
292 /* Unexpected error. */
293 urcu_die(errno);
294 }
295 }
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296}
297
298static void call_rcu_completion_wake_up(struct call_rcu_completion *completion)
299{
300 /* Write to completion barrier count before reading/writing futex */
301 cmm_smp_mb();
302 if (caa_unlikely(uatomic_read(&completion->futex) == -1)) {
303 uatomic_set(&completion->futex, 0);
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304 if (futex_async(&completion->futex, FUTEX_WAKE, 1,
305 NULL, NULL, 0) < 0)
306 urcu_die(errno);
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307 }
308}
309
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310/* This is the code run by each call_rcu thread. */
311
312static void *call_rcu_thread(void *arg)
313{
314 unsigned long cbcount;
5161f31e 315 struct call_rcu_data *crdp = (struct call_rcu_data *) arg;
2870aa1e 316 int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT);
b57aee66 317
8e3690db 318 if (set_thread_cpu_affinity(crdp))
4a6d7378 319 urcu_die(errno);
c1d2c60b 320
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321 /*
322 * If callbacks take a read-side lock, we need to be registered.
323 */
324 rcu_register_thread();
325
bd252a04 326 URCU_TLS(thread_call_rcu_data) = crdp;
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327 if (!rt) {
328 uatomic_dec(&crdp->futex);
329 /* Decrement futex before reading call_rcu list */
330 cmm_smp_mb();
331 }
b57aee66 332 for (;;) {
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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;
ae25b7e2 336 enum cds_wfcq_ret splice_ret;
5161f31e 337
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338 if (set_thread_cpu_affinity(crdp))
339 urcu_die(errno);
340
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341 if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) {
342 /*
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.
347 */
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)
109105b7 352 (void) poll(NULL, 0, 1);
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353 uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED);
354 cmm_smp_mb__after_uatomic_and();
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355 rcu_register_thread();
356 }
357
5161f31e 358 cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
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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) {
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364 synchronize_rcu();
365 cbcount = 0;
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366 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head,
367 &cbs_tmp_tail, cbs, cbs_tmp_n) {
368 struct rcu_head *rhp;
369
370 rhp = caa_container_of(cbs,
371 struct rcu_head, next);
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372 rhp->func(rhp);
373 cbcount++;
5161f31e 374 }
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375 uatomic_sub(&crdp->qlen, cbcount);
376 }
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377 if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP)
378 break;
765f3ead 379 rcu_thread_offline();
bc94ca9b 380 if (!rt) {
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381 if (cds_wfcq_empty(&crdp->cbs_head,
382 &crdp->cbs_tail)) {
bc94ca9b 383 call_rcu_wait(crdp);
109105b7 384 (void) poll(NULL, 0, 10);
bc94ca9b 385 uatomic_dec(&crdp->futex);
c768e45e 386 /*
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387 * Decrement futex before reading
388 * call_rcu list.
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389 */
390 cmm_smp_mb();
ccbac24d 391 } else {
109105b7 392 (void) poll(NULL, 0, 10);
c768e45e 393 }
bc94ca9b 394 } else {
109105b7 395 (void) poll(NULL, 0, 10);
b57aee66 396 }
765f3ead 397 rcu_thread_online();
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398 }
399 if (!rt) {
400 /*
401 * Read call_rcu list before write futex.
402 */
403 cmm_smp_mb();
404 uatomic_set(&crdp->futex, 0);
b57aee66 405 }
2870aa1e 406 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED);
765f3ead 407 rcu_unregister_thread();
7106ddf8 408 return NULL;
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409}
410
411/*
412 * Create both a call_rcu thread and the corresponding call_rcu_data
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413 * structure, linking the structure in as specified. Caller must hold
414 * call_rcu_mutex.
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415 */
416
3c24913f 417static void call_rcu_data_init(struct call_rcu_data **crdpp,
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418 unsigned long flags,
419 int cpu_affinity)
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420{
421 struct call_rcu_data *crdp;
4a6d7378 422 int ret;
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423
424 crdp = malloc(sizeof(*crdp));
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425 if (crdp == NULL)
426 urcu_die(errno);
b57aee66 427 memset(crdp, '\0', sizeof(*crdp));
5161f31e 428 cds_wfcq_init(&crdp->cbs_head, &crdp->cbs_tail);
b57aee66 429 crdp->qlen = 0;
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430 crdp->futex = 0;
431 crdp->flags = flags;
3c24913f 432 cds_list_add(&crdp->list, &call_rcu_data_list);
c1d2c60b 433 crdp->cpu_affinity = cpu_affinity;
8e3690db 434 crdp->gp_count = 0;
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435 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
436 *crdpp = crdp;
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437 ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp);
438 if (ret)
439 urcu_die(ret);
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440}
441
442/*
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
63b495d8 446 * urcu_sched_getcpu().
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447 *
448 * The call to this function and use of the returned call_rcu_data
449 * should be protected by RCU read-side lock.
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450 */
451
452struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
453{
454 static int warned = 0;
618b2595 455 struct call_rcu_data **pcpu_crdp;
b57aee66 456
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457 pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data);
458 if (pcpu_crdp == NULL)
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459 return NULL;
460 if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) {
461 fprintf(stderr, "[error] liburcu: get CPU # out of range\n");
462 warned = 1;
463 }
464 if (cpu < 0 || maxcpus <= cpu)
465 return NULL;
618b2595 466 return rcu_dereference(pcpu_crdp[cpu]);
b57aee66 467}
ce28e67a 468URCU_ATTR_ALIAS(urcu_stringify(get_cpu_call_rcu_data))
4477a870 469struct call_rcu_data *alias_get_cpu_call_rcu_data();
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470
471/*
472 * Return the tid corresponding to the call_rcu thread whose
473 * call_rcu_data structure is specified.
474 */
475
476pthread_t get_call_rcu_thread(struct call_rcu_data *crdp)
477{
478 return crdp->tid;
479}
ce28e67a 480URCU_ATTR_ALIAS(urcu_stringify(get_call_rcu_thread))
4477a870 481pthread_t alias_get_call_rcu_thread();
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482
483/*
484 * Create a call_rcu_data structure (with thread) and return a pointer.
485 */
486
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487static struct call_rcu_data *__create_call_rcu_data(unsigned long flags,
488 int cpu_affinity)
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489{
490 struct call_rcu_data *crdp;
491
c1d2c60b 492 call_rcu_data_init(&crdp, flags, cpu_affinity);
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493 return crdp;
494}
495
ce28e67a 496URCU_ATTR_ALIAS(urcu_stringify(create_call_rcu_data))
4477a870 497struct call_rcu_data *alias_create_call_rcu_data();
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498struct call_rcu_data *create_call_rcu_data(unsigned long flags,
499 int cpu_affinity)
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500{
501 struct call_rcu_data *crdp;
502
503 call_rcu_lock(&call_rcu_mutex);
c1d2c60b 504 crdp = __create_call_rcu_data(flags, cpu_affinity);
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505 call_rcu_unlock(&call_rcu_mutex);
506 return crdp;
507}
508
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509/*
510 * Set the specified CPU to use the specified call_rcu_data structure.
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511 *
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).
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516 *
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.
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520 */
521
522int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
523{
dcfc8165 524 static int warned = 0;
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525
526 call_rcu_lock(&call_rcu_mutex);
f3776786 527 alloc_cpu_call_rcu_data();
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528 if (cpu < 0 || maxcpus <= cpu) {
529 if (!warned) {
530 fprintf(stderr, "[error] liburcu: set CPU # out of range\n");
531 warned = 1;
532 }
533 call_rcu_unlock(&call_rcu_mutex);
534 errno = EINVAL;
535 return -EINVAL;
536 }
53a55535 537
b57aee66 538 if (per_cpu_call_rcu_data == NULL) {
3670fef2 539 call_rcu_unlock(&call_rcu_mutex);
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540 errno = ENOMEM;
541 return -ENOMEM;
542 }
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543
544 if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) {
545 call_rcu_unlock(&call_rcu_mutex);
546 errno = EEXIST;
547 return -EEXIST;
548 }
549
618b2595 550 rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp);
3670fef2 551 call_rcu_unlock(&call_rcu_mutex);
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552 return 0;
553}
ce28e67a 554URCU_ATTR_ALIAS(urcu_stringify(set_cpu_call_rcu_data))
4477a870 555int alias_set_cpu_call_rcu_data();
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556
557/*
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.
561 */
562
563struct call_rcu_data *get_default_call_rcu_data(void)
564{
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;
571 }
c1d2c60b 572 call_rcu_data_init(&default_call_rcu_data, 0, -1);
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573 call_rcu_unlock(&call_rcu_mutex);
574 return default_call_rcu_data;
575}
ce28e67a 576URCU_ATTR_ALIAS(urcu_stringify(get_default_call_rcu_data))
4477a870 577struct call_rcu_data *alias_get_default_call_rcu_data();
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578
579/*
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.
618b2595
MD
586 *
587 * Calls to this function and use of the returned call_rcu_data should
588 * be protected by RCU read-side lock.
b57aee66
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589 */
590struct call_rcu_data *get_call_rcu_data(void)
591{
9744f3bb 592 struct call_rcu_data *crd;
b57aee66 593
bd252a04
MD
594 if (URCU_TLS(thread_call_rcu_data) != NULL)
595 return URCU_TLS(thread_call_rcu_data);
9744f3bb
LJ
596
597 if (maxcpus > 0) {
63b495d8 598 crd = get_cpu_call_rcu_data(urcu_sched_getcpu());
9744f3bb
LJ
599 if (crd)
600 return crd;
b57aee66 601 }
9744f3bb 602
b57aee66
PM
603 return get_default_call_rcu_data();
604}
ce28e67a 605URCU_ATTR_ALIAS(urcu_stringify(get_call_rcu_data))
4477a870 606struct call_rcu_data *alias_get_call_rcu_data();
b57aee66
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607
608/*
609 * Return a pointer to this task's call_rcu_data if there is one.
610 */
611
612struct call_rcu_data *get_thread_call_rcu_data(void)
613{
bd252a04 614 return URCU_TLS(thread_call_rcu_data);
b57aee66 615}
ce28e67a 616URCU_ATTR_ALIAS(urcu_stringify(get_thread_call_rcu_data))
4477a870 617struct call_rcu_data *alias_get_thread_call_rcu_data();
b57aee66
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618
619/*
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.)
7106ddf8
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623 *
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).
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628 */
629
630void set_thread_call_rcu_data(struct call_rcu_data *crdp)
631{
bd252a04 632 URCU_TLS(thread_call_rcu_data) = crdp;
b57aee66 633}
ce28e67a 634URCU_ATTR_ALIAS(urcu_stringify(set_thread_call_rcu_data))
4477a870 635void alias_set_thread_call_rcu_data();
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636
637/*
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()
0938c541
MD
640 * function if you want that behavior. Should be paired with
641 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
642 * threads.
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643 */
644
645int create_all_cpu_call_rcu_data(unsigned long flags)
646{
647 int i;
648 struct call_rcu_data *crdp;
649 int ret;
650
651 call_rcu_lock(&call_rcu_mutex);
652 alloc_cpu_call_rcu_data();
653 call_rcu_unlock(&call_rcu_mutex);
654 if (maxcpus <= 0) {
655 errno = EINVAL;
656 return -EINVAL;
657 }
658 if (per_cpu_call_rcu_data == NULL) {
659 errno = ENOMEM;
660 return -ENOMEM;
661 }
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);
666 continue;
667 }
c1d2c60b 668 crdp = __create_call_rcu_data(flags, i);
b57aee66
PM
669 if (crdp == NULL) {
670 call_rcu_unlock(&call_rcu_mutex);
671 errno = ENOMEM;
672 return -ENOMEM;
673 }
674 call_rcu_unlock(&call_rcu_mutex);
675 if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) {
356c8794
LJ
676 call_rcu_data_free(crdp);
677
678 /* it has been created by other thread */
679 if (ret == -EEXIST)
680 continue;
681
682 return ret;
b57aee66
PM
683 }
684 }
685 return 0;
686}
ce28e67a 687URCU_ATTR_ALIAS(urcu_stringify(create_all_cpu_call_rcu_data))
4477a870 688int alias_create_all_cpu_call_rcu_data();
b57aee66 689
7106ddf8
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690/*
691 * Wake up the call_rcu thread corresponding to the specified
692 * call_rcu_data structure.
693 */
694static void wake_call_rcu_thread(struct call_rcu_data *crdp)
695{
263e3cf9
MD
696 if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT))
697 call_rcu_wake_up(crdp);
7106ddf8
PM
698}
699
b7f721d9
MD
700static void _call_rcu(struct rcu_head *head,
701 void (*func)(struct rcu_head *head),
702 struct call_rcu_data *crdp)
703{
704 cds_wfcq_node_init(&head->next);
705 head->func = func;
706 cds_wfcq_enqueue(&crdp->cbs_head, &crdp->cbs_tail, &head->next);
707 uatomic_inc(&crdp->qlen);
708 wake_call_rcu_thread(crdp);
709}
710
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711/*
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.
716 *
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().
618b2595
MD
722 *
723 * call_rcu must be called by registered RCU read-side threads.
b57aee66 724 */
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725void call_rcu(struct rcu_head *head,
726 void (*func)(struct rcu_head *head))
727{
728 struct call_rcu_data *crdp;
729
618b2595 730 /* Holding rcu read-side lock across use of per-cpu crdp */
ffb4aaa7 731 _rcu_read_lock();
b57aee66 732 crdp = get_call_rcu_data();
b7f721d9 733 _call_rcu(head, func, crdp);
ffb4aaa7 734 _rcu_read_unlock();
7106ddf8 735}
ce28e67a 736URCU_ATTR_ALIAS(urcu_stringify(call_rcu)) void alias_call_rcu();
7106ddf8
PM
737
738/*
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.
745 *
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.
752 *
753 * We also silently refuse to free NULL pointers. This simplifies
754 * the calling code.
f9da0936
MD
755 *
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.
03e5118f
MD
759 *
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.
7106ddf8
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763 */
764void call_rcu_data_free(struct call_rcu_data *crdp)
765{
7106ddf8
PM
766 if (crdp == NULL || crdp == default_call_rcu_data) {
767 return;
768 }
2870aa1e
PB
769 if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) {
770 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP);
7106ddf8 771 wake_call_rcu_thread(crdp);
2870aa1e 772 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0)
109105b7 773 (void) poll(NULL, 0, 1);
7106ddf8 774 }
51b98c3c 775 call_rcu_lock(&call_rcu_mutex);
5161f31e 776 if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) {
51b98c3c
PM
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. */
698d0778 780 (void) get_default_call_rcu_data();
51b98c3c 781 call_rcu_lock(&call_rcu_mutex);
5161f31e
MD
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);
7106ddf8
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785 uatomic_add(&default_call_rcu_data->qlen,
786 uatomic_read(&crdp->qlen));
1e92aa15 787 wake_call_rcu_thread(default_call_rcu_data);
7106ddf8 788 }
59dc9e9d
LJ
789
790 cds_list_del(&crdp->list);
b75dffe6
LJ
791 call_rcu_unlock(&call_rcu_mutex);
792
59dc9e9d 793 free(crdp);
7106ddf8 794}
ce28e67a 795URCU_ATTR_ALIAS(urcu_stringify(call_rcu_data_free))
4477a870 796void alias_call_rcu_data_free();
7106ddf8
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797
798/*
799 * Clean up all the per-CPU call_rcu threads.
800 */
801void free_all_cpu_call_rcu_data(void)
802{
803 int cpu;
618b2595
MD
804 struct call_rcu_data **crdp;
805 static int warned = 0;
7106ddf8
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806
807 if (maxcpus <= 0)
808 return;
618b2595
MD
809
810 crdp = malloc(sizeof(*crdp) * maxcpus);
811 if (!crdp) {
812 if (!warned) {
813 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
814 }
815 warned = 1;
d31150b4 816 return;
618b2595
MD
817 }
818
7106ddf8 819 for (cpu = 0; cpu < maxcpus; cpu++) {
618b2595
MD
820 crdp[cpu] = get_cpu_call_rcu_data(cpu);
821 if (crdp[cpu] == NULL)
7106ddf8
PM
822 continue;
823 set_cpu_call_rcu_data(cpu, NULL);
7106ddf8 824 }
618b2595
MD
825 /*
826 * Wait for call_rcu sites acting as RCU readers of the
827 * call_rcu_data to become quiescent.
828 */
829 synchronize_rcu();
830 for (cpu = 0; cpu < maxcpus; cpu++) {
831 if (crdp[cpu] == NULL)
832 continue;
833 call_rcu_data_free(crdp[cpu]);
834 }
835 free(crdp);
7106ddf8 836}
4477a870
MD
837#ifdef RCU_QSBR
838/* ABI6 has a non-namespaced free_all_cpu_call_rcu_data for qsbr */
839#undef free_all_cpu_call_rcu_data
ce28e67a 840URCU_ATTR_ALIAS("urcu_qsbr_free_all_cpu_call_rcu_data")
4477a870
MD
841void free_all_cpu_call_rcu_data();
842#define free_all_cpu_call_rcu_data urcu_qsbr_free_all_cpu_call_rcu_data
843#else
ce28e67a 844URCU_ATTR_ALIAS(urcu_stringify(free_all_cpu_call_rcu_data))
4477a870
MD
845void alias_free_all_cpu_call_rcu_data();
846#endif
7106ddf8 847
81dd9134
KF
848static
849void free_completion(struct urcu_ref *ref)
850{
851 struct call_rcu_completion *completion;
852
853 completion = caa_container_of(ref, struct call_rcu_completion, ref);
854 free(completion);
855}
856
b7f721d9
MD
857static
858void _rcu_barrier_complete(struct rcu_head *head)
859{
860 struct call_rcu_completion_work *work;
861 struct call_rcu_completion *completion;
862
863 work = caa_container_of(head, struct call_rcu_completion_work, head);
864 completion = work->completion;
81dd9134
KF
865 if (!uatomic_sub_return(&completion->barrier_count, 1))
866 call_rcu_completion_wake_up(completion);
867 urcu_ref_put(&completion->ref, free_completion);
b7f721d9
MD
868 free(work);
869}
870
871/*
872 * Wait for all in-flight call_rcu callbacks to complete execution.
873 */
874void rcu_barrier(void)
875{
876 struct call_rcu_data *crdp;
81dd9134 877 struct call_rcu_completion *completion;
63f0fc6d 878 int count = 0;
b7f721d9
MD
879 int was_online;
880
881 /* Put in offline state in QSBR. */
ffb4aaa7 882 was_online = _rcu_read_ongoing();
b7f721d9
MD
883 if (was_online)
884 rcu_thread_offline();
885 /*
886 * Calling a rcu_barrier() within a RCU read-side critical
887 * section is an error.
888 */
ffb4aaa7 889 if (_rcu_read_ongoing()) {
b7f721d9
MD
890 static int warned = 0;
891
892 if (!warned) {
893 fprintf(stderr, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
894 }
895 warned = 1;
896 goto online;
897 }
898
81dd9134
KF
899 completion = calloc(sizeof(*completion), 1);
900 if (!completion)
901 urcu_die(errno);
902
b7f721d9
MD
903 call_rcu_lock(&call_rcu_mutex);
904 cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
905 count++;
906
81dd9134
KF
907 /* Referenced by rcu_barrier() and each call_rcu thread. */
908 urcu_ref_set(&completion->ref, count + 1);
909 completion->barrier_count = count;
b7f721d9
MD
910
911 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
912 struct call_rcu_completion_work *work;
913
914 work = calloc(sizeof(*work), 1);
63f0fc6d
MD
915 if (!work)
916 urcu_die(errno);
81dd9134 917 work->completion = completion;
b7f721d9 918 _call_rcu(&work->head, _rcu_barrier_complete, crdp);
b7f721d9
MD
919 }
920 call_rcu_unlock(&call_rcu_mutex);
921
b7f721d9
MD
922 /* Wait for them */
923 for (;;) {
81dd9134 924 uatomic_dec(&completion->futex);
b7f721d9
MD
925 /* Decrement futex before reading barrier_count */
926 cmm_smp_mb();
81dd9134 927 if (!uatomic_read(&completion->barrier_count))
b7f721d9 928 break;
81dd9134 929 call_rcu_completion_wait(completion);
b7f721d9 930 }
81dd9134
KF
931
932 urcu_ref_put(&completion->ref, free_completion);
933
b7f721d9
MD
934online:
935 if (was_online)
936 rcu_thread_online();
937}
ce28e67a 938URCU_ATTR_ALIAS(urcu_stringify(rcu_barrier))
4477a870 939void alias_rcu_barrier();
b7f721d9 940
81ad2e19
PM
941/*
942 * Acquire the call_rcu_mutex in order to ensure that the child sees
e85451a1
MD
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.
81ad2e19
PM
945 * Suitable for pthread_atfork() and friends.
946 */
947void call_rcu_before_fork(void)
948{
e85451a1 949 struct call_rcu_data *crdp;
d0ec0ed2 950 struct urcu_atfork *atfork;
e85451a1 951
81ad2e19 952 call_rcu_lock(&call_rcu_mutex);
e85451a1 953
d0ec0ed2
MD
954 atfork = registered_rculfhash_atfork;
955 if (atfork)
956 atfork->before_fork(atfork->priv);
957
e85451a1
MD
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);
962 }
963 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
964 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0)
109105b7 965 (void) poll(NULL, 0, 1);
e85451a1 966 }
81ad2e19 967}
ce28e67a 968URCU_ATTR_ALIAS(urcu_stringify(call_rcu_before_fork))
4477a870 969void alias_call_rcu_before_fork();
81ad2e19
PM
970
971/*
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.
975 */
976void call_rcu_after_fork_parent(void)
977{
e85451a1 978 struct call_rcu_data *crdp;
d0ec0ed2 979 struct urcu_atfork *atfork;
e85451a1
MD
980
981 cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
982 uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE);
fc236e5e
KF
983 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
984 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) != 0)
109105b7 985 (void) poll(NULL, 0, 1);
fc236e5e 986 }
d0ec0ed2
MD
987 atfork = registered_rculfhash_atfork;
988 if (atfork)
989 atfork->after_fork_parent(atfork->priv);
81ad2e19
PM
990 call_rcu_unlock(&call_rcu_mutex);
991}
ce28e67a 992URCU_ATTR_ALIAS(urcu_stringify(call_rcu_after_fork_parent))
4477a870 993void alias_call_rcu_after_fork_parent();
81ad2e19 994
7106ddf8
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995/*
996 * Clean up call_rcu data structures in the child of a successful fork()
81ad2e19
PM
997 * that is not followed by exec(). Suitable for pthread_atfork() and
998 * friends.
7106ddf8
PM
999 */
1000void call_rcu_after_fork_child(void)
1001{
077ff173 1002 struct call_rcu_data *crdp, *next;
d0ec0ed2 1003 struct urcu_atfork *atfork;
7106ddf8 1004
81ad2e19
PM
1005 /* Release the mutex. */
1006 call_rcu_unlock(&call_rcu_mutex);
1007
d0ec0ed2
MD
1008 atfork = registered_rculfhash_atfork;
1009 if (atfork)
1010 atfork->after_fork_child(atfork->priv);
1011
ad1b9909
LJ
1012 /* Do nothing when call_rcu() has not been used */
1013 if (cds_list_empty(&call_rcu_data_list))
1014 return;
1015
7106ddf8
PM
1016 /*
1017 * Allocate a new default call_rcu_data structure in order
1018 * to get a working call_rcu thread to go with it.
1019 */
1020 default_call_rcu_data = NULL;
1021 (void)get_default_call_rcu_data();
1022
60af049d
LJ
1023 /* Cleanup call_rcu_data pointers before use */
1024 maxcpus_reset();
1025 free(per_cpu_call_rcu_data);
618b2595 1026 rcu_set_pointer(&per_cpu_call_rcu_data, NULL);
bd252a04 1027 URCU_TLS(thread_call_rcu_data) = NULL;
60af049d 1028
e85451a1
MD
1029 /*
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.
1033 */
077ff173 1034 cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
7106ddf8 1035 if (crdp == default_call_rcu_data)
077ff173 1036 continue;
2870aa1e 1037 uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED);
7106ddf8 1038 call_rcu_data_free(crdp);
b57aee66
PM
1039 }
1040}
ce28e67a 1041URCU_ATTR_ALIAS(urcu_stringify(call_rcu_after_fork_child))
4477a870 1042void alias_call_rcu_after_fork_child();
d0ec0ed2
MD
1043
1044void urcu_register_rculfhash_atfork(struct urcu_atfork *atfork)
1045{
1046 call_rcu_lock(&call_rcu_mutex);
1047 if (registered_rculfhash_atfork_refcount++)
1048 goto end;
1049 registered_rculfhash_atfork = atfork;
1050end:
1051 call_rcu_unlock(&call_rcu_mutex);
1052}
ce28e67a 1053URCU_ATTR_ALIAS(urcu_stringify(urcu_register_rculfhash_atfork))
4477a870 1054void alias_urcu_register_rculfhash_atfork();
d0ec0ed2
MD
1055
1056void urcu_unregister_rculfhash_atfork(struct urcu_atfork *atfork)
1057{
1058 call_rcu_lock(&call_rcu_mutex);
1059 if (--registered_rculfhash_atfork_refcount)
1060 goto end;
1061 registered_rculfhash_atfork = NULL;
1062end:
1063 call_rcu_unlock(&call_rcu_mutex);
1064}
ce28e67a 1065URCU_ATTR_ALIAS(urcu_stringify(urcu_unregister_rculfhash_atfork))
4477a870 1066void alias_urcu_unregister_rculfhash_atfork();
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