Fix: call rcu should call internal RCU API
[urcu.git] / 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
c1d2c60b 23#define _GNU_SOURCE
5161f31e 24#define _LGPL_SOURCE
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25#include <stdio.h>
26#include <pthread.h>
27#include <signal.h>
28#include <assert.h>
29#include <stdlib.h>
6d841bc2 30#include <stdint.h>
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31#include <string.h>
32#include <errno.h>
33#include <poll.h>
34#include <sys/time.h>
b57aee66 35#include <unistd.h>
c1d2c60b 36#include <sched.h>
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37
38#include "config.h"
5161f31e 39#include "urcu/wfcqueue.h"
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40#include "urcu-call-rcu.h"
41#include "urcu-pointer.h"
3c24913f 42#include "urcu/list.h"
41849996 43#include "urcu/futex.h"
bd252a04 44#include "urcu/tls-compat.h"
81dd9134 45#include "urcu/ref.h"
4a6d7378 46#include "urcu-die.h"
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47
48/* Data structure that identifies a call_rcu thread. */
49
50struct call_rcu_data {
5161f31e 51 /*
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52 * We do not align head on a different cache-line than tail
53 * mainly because call_rcu callback-invocation threads use
54 * batching ("splice") to get an entire list of callbacks, which
55 * effectively empties the queue, and requires to touch the tail
56 * anyway.
5161f31e 57 */
b9f893b6 58 struct cds_wfcq_tail cbs_tail;
0b8ab7df 59 struct cds_wfcq_head cbs_head;
b57aee66 60 unsigned long flags;
6d841bc2 61 int32_t futex;
73987721 62 unsigned long qlen; /* maintained for debugging. */
b57aee66 63 pthread_t tid;
c1d2c60b 64 int cpu_affinity;
3c24913f 65 struct cds_list_head list;
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66} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
67
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68struct call_rcu_completion {
69 int barrier_count;
70 int32_t futex;
81dd9134 71 struct urcu_ref ref;
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72};
73
74struct call_rcu_completion_work {
75 struct rcu_head head;
76 struct call_rcu_completion *completion;
77};
78
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79/*
80 * List of all call_rcu_data structures to keep valgrind happy.
81 * Protected by call_rcu_mutex.
82 */
83
bab44e28 84static CDS_LIST_HEAD(call_rcu_data_list);
3c24913f 85
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86/* Link a thread using call_rcu() to its call_rcu thread. */
87
bd252a04 88static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data);
b57aee66 89
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90/*
91 * Guard call_rcu thread creation and atfork handlers.
92 */
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93static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
94
95/* If a given thread does not have its own call_rcu thread, this is default. */
96
97static struct call_rcu_data *default_call_rcu_data;
98
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99/*
100 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
101 * available, then we can have call_rcu threads assigned to individual
102 * CPUs rather than only to specific threads.
103 */
104
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105#ifdef HAVE_SCHED_GETCPU
106
107static int urcu_sched_getcpu(void)
108{
109 return sched_getcpu();
110}
111
112#else /* #ifdef HAVE_SCHED_GETCPU */
113
114static int urcu_sched_getcpu(void)
115{
116 return -1;
117}
118
119#endif /* #else #ifdef HAVE_SCHED_GETCPU */
120
121#if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU)
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122
123/*
124 * Pointer to array of pointers to per-CPU call_rcu_data structures
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125 * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an
126 * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a
127 * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer
128 * without mutex. The call_rcu_mutex protects updates.
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129 */
130
131static struct call_rcu_data **per_cpu_call_rcu_data;
132static long maxcpus;
133
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134static void maxcpus_reset(void)
135{
136 maxcpus = 0;
137}
138
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139/* Allocate the array if it has not already been allocated. */
140
141static void alloc_cpu_call_rcu_data(void)
142{
143 struct call_rcu_data **p;
144 static int warned = 0;
145
146 if (maxcpus != 0)
147 return;
148 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
149 if (maxcpus <= 0) {
150 return;
151 }
152 p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data));
153 if (p != NULL) {
154 memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data));
618b2595 155 rcu_set_pointer(&per_cpu_call_rcu_data, p);
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156 } else {
157 if (!warned) {
158 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
159 }
160 warned = 1;
161 }
162}
163
63b495d8 164#else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
b57aee66 165
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166/*
167 * per_cpu_call_rcu_data should be constant, but some functions below, used both
168 * for cases where cpu number is available and not available, assume it it not
169 * constant.
170 */
171static struct call_rcu_data **per_cpu_call_rcu_data = NULL;
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172static const long maxcpus = -1;
173
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174static void maxcpus_reset(void)
175{
176}
177
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178static void alloc_cpu_call_rcu_data(void)
179{
180}
181
63b495d8 182#endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
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183
184/* Acquire the specified pthread mutex. */
185
186static void call_rcu_lock(pthread_mutex_t *pmp)
187{
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188 int ret;
189
190 ret = pthread_mutex_lock(pmp);
191 if (ret)
192 urcu_die(ret);
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193}
194
195/* Release the specified pthread mutex. */
196
197static void call_rcu_unlock(pthread_mutex_t *pmp)
198{
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199 int ret;
200
201 ret = pthread_mutex_unlock(pmp);
202 if (ret)
203 urcu_die(ret);
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204}
205
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206#if HAVE_SCHED_SETAFFINITY
207static
208int set_thread_cpu_affinity(struct call_rcu_data *crdp)
209{
210 cpu_set_t mask;
211
212 if (crdp->cpu_affinity < 0)
213 return 0;
214
215 CPU_ZERO(&mask);
216 CPU_SET(crdp->cpu_affinity, &mask);
217#if SCHED_SETAFFINITY_ARGS == 2
218 return sched_setaffinity(0, &mask);
219#else
220 return sched_setaffinity(0, sizeof(mask), &mask);
221#endif
222}
223#else
224static
225int set_thread_cpu_affinity(struct call_rcu_data *crdp)
226{
227 return 0;
228}
229#endif
230
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231static void call_rcu_wait(struct call_rcu_data *crdp)
232{
233 /* Read call_rcu list before read futex */
234 cmm_smp_mb();
235 if (uatomic_read(&crdp->futex) == -1)
236 futex_async(&crdp->futex, FUTEX_WAIT, -1,
237 NULL, NULL, 0);
238}
239
240static void call_rcu_wake_up(struct call_rcu_data *crdp)
241{
242 /* Write to call_rcu list before reading/writing futex */
243 cmm_smp_mb();
a0b7f7ea 244 if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) {
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245 uatomic_set(&crdp->futex, 0);
246 futex_async(&crdp->futex, FUTEX_WAKE, 1,
247 NULL, NULL, 0);
248 }
249}
250
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251static void call_rcu_completion_wait(struct call_rcu_completion *completion)
252{
253 /* Read completion barrier count before read futex */
254 cmm_smp_mb();
255 if (uatomic_read(&completion->futex) == -1)
256 futex_async(&completion->futex, FUTEX_WAIT, -1,
257 NULL, NULL, 0);
258}
259
260static void call_rcu_completion_wake_up(struct call_rcu_completion *completion)
261{
262 /* Write to completion barrier count before reading/writing futex */
263 cmm_smp_mb();
264 if (caa_unlikely(uatomic_read(&completion->futex) == -1)) {
265 uatomic_set(&completion->futex, 0);
266 futex_async(&completion->futex, FUTEX_WAKE, 1,
267 NULL, NULL, 0);
268 }
269}
270
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271/* This is the code run by each call_rcu thread. */
272
273static void *call_rcu_thread(void *arg)
274{
275 unsigned long cbcount;
5161f31e 276 struct call_rcu_data *crdp = (struct call_rcu_data *) arg;
2870aa1e 277 int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT);
4a6d7378 278 int ret;
b57aee66 279
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280 ret = set_thread_cpu_affinity(crdp);
281 if (ret)
282 urcu_die(errno);
c1d2c60b 283
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284 /*
285 * If callbacks take a read-side lock, we need to be registered.
286 */
287 rcu_register_thread();
288
bd252a04 289 URCU_TLS(thread_call_rcu_data) = crdp;
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290 if (!rt) {
291 uatomic_dec(&crdp->futex);
292 /* Decrement futex before reading call_rcu list */
293 cmm_smp_mb();
294 }
b57aee66 295 for (;;) {
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296 struct cds_wfcq_head cbs_tmp_head;
297 struct cds_wfcq_tail cbs_tmp_tail;
298 struct cds_wfcq_node *cbs, *cbs_tmp_n;
ae25b7e2 299 enum cds_wfcq_ret splice_ret;
5161f31e 300
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301 if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) {
302 /*
303 * Pause requested. Become quiescent: remove
304 * ourself from all global lists, and don't
305 * process any callback. The callback lists may
306 * still be non-empty though.
307 */
308 rcu_unregister_thread();
309 cmm_smp_mb__before_uatomic_or();
310 uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED);
311 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0)
312 poll(NULL, 0, 1);
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313 uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED);
314 cmm_smp_mb__after_uatomic_and();
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315 rcu_register_thread();
316 }
317
5161f31e 318 cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
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319 splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head,
320 &cbs_tmp_tail, &crdp->cbs_head, &crdp->cbs_tail);
321 assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK);
322 assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY);
323 if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) {
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324 synchronize_rcu();
325 cbcount = 0;
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326 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head,
327 &cbs_tmp_tail, cbs, cbs_tmp_n) {
328 struct rcu_head *rhp;
329
330 rhp = caa_container_of(cbs,
331 struct rcu_head, next);
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332 rhp->func(rhp);
333 cbcount++;
5161f31e 334 }
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335 uatomic_sub(&crdp->qlen, cbcount);
336 }
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337 if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP)
338 break;
765f3ead 339 rcu_thread_offline();
bc94ca9b 340 if (!rt) {
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341 if (cds_wfcq_empty(&crdp->cbs_head,
342 &crdp->cbs_tail)) {
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343 call_rcu_wait(crdp);
344 poll(NULL, 0, 10);
345 uatomic_dec(&crdp->futex);
c768e45e 346 /*
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347 * Decrement futex before reading
348 * call_rcu list.
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349 */
350 cmm_smp_mb();
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351 } else {
352 poll(NULL, 0, 10);
c768e45e 353 }
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354 } else {
355 poll(NULL, 0, 10);
b57aee66 356 }
765f3ead 357 rcu_thread_online();
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358 }
359 if (!rt) {
360 /*
361 * Read call_rcu list before write futex.
362 */
363 cmm_smp_mb();
364 uatomic_set(&crdp->futex, 0);
b57aee66 365 }
2870aa1e 366 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED);
765f3ead 367 rcu_unregister_thread();
7106ddf8 368 return NULL;
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369}
370
371/*
372 * Create both a call_rcu thread and the corresponding call_rcu_data
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373 * structure, linking the structure in as specified. Caller must hold
374 * call_rcu_mutex.
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375 */
376
3c24913f 377static void call_rcu_data_init(struct call_rcu_data **crdpp,
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378 unsigned long flags,
379 int cpu_affinity)
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380{
381 struct call_rcu_data *crdp;
4a6d7378 382 int ret;
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383
384 crdp = malloc(sizeof(*crdp));
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385 if (crdp == NULL)
386 urcu_die(errno);
b57aee66 387 memset(crdp, '\0', sizeof(*crdp));
5161f31e 388 cds_wfcq_init(&crdp->cbs_head, &crdp->cbs_tail);
b57aee66 389 crdp->qlen = 0;
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390 crdp->futex = 0;
391 crdp->flags = flags;
3c24913f 392 cds_list_add(&crdp->list, &call_rcu_data_list);
c1d2c60b 393 crdp->cpu_affinity = cpu_affinity;
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394 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
395 *crdpp = crdp;
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396 ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp);
397 if (ret)
398 urcu_die(ret);
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399}
400
401/*
402 * Return a pointer to the call_rcu_data structure for the specified
403 * CPU, returning NULL if there is none. We cannot automatically
404 * created it because the platform we are running on might not define
63b495d8 405 * urcu_sched_getcpu().
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406 *
407 * The call to this function and use of the returned call_rcu_data
408 * should be protected by RCU read-side lock.
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409 */
410
411struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
412{
413 static int warned = 0;
618b2595 414 struct call_rcu_data **pcpu_crdp;
b57aee66 415
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416 pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data);
417 if (pcpu_crdp == NULL)
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418 return NULL;
419 if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) {
420 fprintf(stderr, "[error] liburcu: get CPU # out of range\n");
421 warned = 1;
422 }
423 if (cpu < 0 || maxcpus <= cpu)
424 return NULL;
618b2595 425 return rcu_dereference(pcpu_crdp[cpu]);
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426}
427
428/*
429 * Return the tid corresponding to the call_rcu thread whose
430 * call_rcu_data structure is specified.
431 */
432
433pthread_t get_call_rcu_thread(struct call_rcu_data *crdp)
434{
435 return crdp->tid;
436}
437
438/*
439 * Create a call_rcu_data structure (with thread) and return a pointer.
440 */
441
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442static struct call_rcu_data *__create_call_rcu_data(unsigned long flags,
443 int cpu_affinity)
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444{
445 struct call_rcu_data *crdp;
446
c1d2c60b 447 call_rcu_data_init(&crdp, flags, cpu_affinity);
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448 return crdp;
449}
450
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451struct call_rcu_data *create_call_rcu_data(unsigned long flags,
452 int cpu_affinity)
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453{
454 struct call_rcu_data *crdp;
455
456 call_rcu_lock(&call_rcu_mutex);
c1d2c60b 457 crdp = __create_call_rcu_data(flags, cpu_affinity);
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458 call_rcu_unlock(&call_rcu_mutex);
459 return crdp;
460}
461
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462/*
463 * Set the specified CPU to use the specified call_rcu_data structure.
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464 *
465 * Use NULL to remove a CPU's call_rcu_data structure, but it is
466 * the caller's responsibility to dispose of the removed structure.
467 * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
468 * (prior to NULLing it out, of course).
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469 *
470 * The caller must wait for a grace-period to pass between return from
471 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
472 * previous call rcu data as argument.
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473 */
474
475int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
476{
dcfc8165 477 static int warned = 0;
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478
479 call_rcu_lock(&call_rcu_mutex);
f3776786 480 alloc_cpu_call_rcu_data();
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481 if (cpu < 0 || maxcpus <= cpu) {
482 if (!warned) {
483 fprintf(stderr, "[error] liburcu: set CPU # out of range\n");
484 warned = 1;
485 }
486 call_rcu_unlock(&call_rcu_mutex);
487 errno = EINVAL;
488 return -EINVAL;
489 }
53a55535 490
b57aee66 491 if (per_cpu_call_rcu_data == NULL) {
3670fef2 492 call_rcu_unlock(&call_rcu_mutex);
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493 errno = ENOMEM;
494 return -ENOMEM;
495 }
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496
497 if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) {
498 call_rcu_unlock(&call_rcu_mutex);
499 errno = EEXIST;
500 return -EEXIST;
501 }
502
618b2595 503 rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp);
3670fef2 504 call_rcu_unlock(&call_rcu_mutex);
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505 return 0;
506}
507
508/*
509 * Return a pointer to the default call_rcu_data structure, creating
510 * one if need be. Because we never free call_rcu_data structures,
511 * we don't need to be in an RCU read-side critical section.
512 */
513
514struct call_rcu_data *get_default_call_rcu_data(void)
515{
516 if (default_call_rcu_data != NULL)
517 return rcu_dereference(default_call_rcu_data);
518 call_rcu_lock(&call_rcu_mutex);
519 if (default_call_rcu_data != NULL) {
520 call_rcu_unlock(&call_rcu_mutex);
521 return default_call_rcu_data;
522 }
c1d2c60b 523 call_rcu_data_init(&default_call_rcu_data, 0, -1);
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524 call_rcu_unlock(&call_rcu_mutex);
525 return default_call_rcu_data;
526}
527
528/*
529 * Return the call_rcu_data structure that applies to the currently
530 * running thread. Any call_rcu_data structure assigned specifically
531 * to this thread has first priority, followed by any call_rcu_data
532 * structure assigned to the CPU on which the thread is running,
533 * followed by the default call_rcu_data structure. If there is not
534 * yet a default call_rcu_data structure, one will be created.
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535 *
536 * Calls to this function and use of the returned call_rcu_data should
537 * be protected by RCU read-side lock.
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538 */
539struct call_rcu_data *get_call_rcu_data(void)
540{
9744f3bb 541 struct call_rcu_data *crd;
b57aee66 542
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543 if (URCU_TLS(thread_call_rcu_data) != NULL)
544 return URCU_TLS(thread_call_rcu_data);
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545
546 if (maxcpus > 0) {
63b495d8 547 crd = get_cpu_call_rcu_data(urcu_sched_getcpu());
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548 if (crd)
549 return crd;
b57aee66 550 }
9744f3bb 551
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552 return get_default_call_rcu_data();
553}
554
555/*
556 * Return a pointer to this task's call_rcu_data if there is one.
557 */
558
559struct call_rcu_data *get_thread_call_rcu_data(void)
560{
bd252a04 561 return URCU_TLS(thread_call_rcu_data);
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562}
563
564/*
565 * Set this task's call_rcu_data structure as specified, regardless
566 * of whether or not this task already had one. (This allows switching
567 * to and from real-time call_rcu threads, for example.)
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568 *
569 * Use NULL to remove a thread's call_rcu_data structure, but it is
570 * the caller's responsibility to dispose of the removed structure.
571 * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
572 * (prior to NULLing it out, of course).
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573 */
574
575void set_thread_call_rcu_data(struct call_rcu_data *crdp)
576{
bd252a04 577 URCU_TLS(thread_call_rcu_data) = crdp;
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578}
579
580/*
581 * Create a separate call_rcu thread for each CPU. This does not
582 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
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583 * function if you want that behavior. Should be paired with
584 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
585 * threads.
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586 */
587
588int create_all_cpu_call_rcu_data(unsigned long flags)
589{
590 int i;
591 struct call_rcu_data *crdp;
592 int ret;
593
594 call_rcu_lock(&call_rcu_mutex);
595 alloc_cpu_call_rcu_data();
596 call_rcu_unlock(&call_rcu_mutex);
597 if (maxcpus <= 0) {
598 errno = EINVAL;
599 return -EINVAL;
600 }
601 if (per_cpu_call_rcu_data == NULL) {
602 errno = ENOMEM;
603 return -ENOMEM;
604 }
605 for (i = 0; i < maxcpus; i++) {
606 call_rcu_lock(&call_rcu_mutex);
607 if (get_cpu_call_rcu_data(i)) {
608 call_rcu_unlock(&call_rcu_mutex);
609 continue;
610 }
c1d2c60b 611 crdp = __create_call_rcu_data(flags, i);
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612 if (crdp == NULL) {
613 call_rcu_unlock(&call_rcu_mutex);
614 errno = ENOMEM;
615 return -ENOMEM;
616 }
617 call_rcu_unlock(&call_rcu_mutex);
618 if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) {
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619 call_rcu_data_free(crdp);
620
621 /* it has been created by other thread */
622 if (ret == -EEXIST)
623 continue;
624
625 return ret;
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626 }
627 }
628 return 0;
629}
630
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631/*
632 * Wake up the call_rcu thread corresponding to the specified
633 * call_rcu_data structure.
634 */
635static void wake_call_rcu_thread(struct call_rcu_data *crdp)
636{
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637 if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT))
638 call_rcu_wake_up(crdp);
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639}
640
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641static void _call_rcu(struct rcu_head *head,
642 void (*func)(struct rcu_head *head),
643 struct call_rcu_data *crdp)
644{
645 cds_wfcq_node_init(&head->next);
646 head->func = func;
647 cds_wfcq_enqueue(&crdp->cbs_head, &crdp->cbs_tail, &head->next);
648 uatomic_inc(&crdp->qlen);
649 wake_call_rcu_thread(crdp);
650}
651
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652/*
653 * Schedule a function to be invoked after a following grace period.
654 * This is the only function that must be called -- the others are
655 * only present to allow applications to tune their use of RCU for
656 * maximum performance.
657 *
658 * Note that unless a call_rcu thread has not already been created,
659 * the first invocation of call_rcu() will create one. So, if you
660 * need the first invocation of call_rcu() to be fast, make sure
661 * to create a call_rcu thread first. One way to accomplish this is
662 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
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663 *
664 * call_rcu must be called by registered RCU read-side threads.
b57aee66 665 */
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666void call_rcu(struct rcu_head *head,
667 void (*func)(struct rcu_head *head))
668{
669 struct call_rcu_data *crdp;
670
618b2595 671 /* Holding rcu read-side lock across use of per-cpu crdp */
ffb4aaa7 672 _rcu_read_lock();
b57aee66 673 crdp = get_call_rcu_data();
b7f721d9 674 _call_rcu(head, func, crdp);
ffb4aaa7 675 _rcu_read_unlock();
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676}
677
678/*
679 * Free up the specified call_rcu_data structure, terminating the
680 * associated call_rcu thread. The caller must have previously
681 * removed the call_rcu_data structure from per-thread or per-CPU
682 * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
683 * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
684 * per-thread call_rcu_data structures.
685 *
686 * We silently refuse to free up the default call_rcu_data structure
687 * because that is where we put any leftover callbacks. Note that
688 * the possibility of self-spawning callbacks makes it impossible
689 * to execute all the callbacks in finite time without putting any
690 * newly spawned callbacks somewhere else. The "somewhere else" of
691 * last resort is the default call_rcu_data structure.
692 *
693 * We also silently refuse to free NULL pointers. This simplifies
694 * the calling code.
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695 *
696 * The caller must wait for a grace-period to pass between return from
697 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
698 * previous call rcu data as argument.
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699 *
700 * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
701 * a list corruption bug in the 0.7.x series. The equivalent fix
702 * appeared in 0.6.8 for the stable-0.6 branch.
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703 */
704void call_rcu_data_free(struct call_rcu_data *crdp)
705{
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706 if (crdp == NULL || crdp == default_call_rcu_data) {
707 return;
708 }
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709 if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) {
710 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP);
7106ddf8 711 wake_call_rcu_thread(crdp);
2870aa1e 712 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0)
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713 poll(NULL, 0, 1);
714 }
5161f31e 715 if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) {
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716 /* Create default call rcu data if need be */
717 (void) get_default_call_rcu_data();
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718 __cds_wfcq_splice_blocking(&default_call_rcu_data->cbs_head,
719 &default_call_rcu_data->cbs_tail,
720 &crdp->cbs_head, &crdp->cbs_tail);
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721 uatomic_add(&default_call_rcu_data->qlen,
722 uatomic_read(&crdp->qlen));
1e92aa15 723 wake_call_rcu_thread(default_call_rcu_data);
7106ddf8 724 }
59dc9e9d 725
b75dffe6 726 call_rcu_lock(&call_rcu_mutex);
59dc9e9d 727 cds_list_del(&crdp->list);
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728 call_rcu_unlock(&call_rcu_mutex);
729
59dc9e9d 730 free(crdp);
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731}
732
733/*
734 * Clean up all the per-CPU call_rcu threads.
735 */
736void free_all_cpu_call_rcu_data(void)
737{
738 int cpu;
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739 struct call_rcu_data **crdp;
740 static int warned = 0;
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741
742 if (maxcpus <= 0)
743 return;
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744
745 crdp = malloc(sizeof(*crdp) * maxcpus);
746 if (!crdp) {
747 if (!warned) {
748 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
749 }
750 warned = 1;
d31150b4 751 return;
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752 }
753
7106ddf8 754 for (cpu = 0; cpu < maxcpus; cpu++) {
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755 crdp[cpu] = get_cpu_call_rcu_data(cpu);
756 if (crdp[cpu] == NULL)
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757 continue;
758 set_cpu_call_rcu_data(cpu, NULL);
7106ddf8 759 }
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760 /*
761 * Wait for call_rcu sites acting as RCU readers of the
762 * call_rcu_data to become quiescent.
763 */
764 synchronize_rcu();
765 for (cpu = 0; cpu < maxcpus; cpu++) {
766 if (crdp[cpu] == NULL)
767 continue;
768 call_rcu_data_free(crdp[cpu]);
769 }
770 free(crdp);
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771}
772
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773static
774void free_completion(struct urcu_ref *ref)
775{
776 struct call_rcu_completion *completion;
777
778 completion = caa_container_of(ref, struct call_rcu_completion, ref);
779 free(completion);
780}
781
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782static
783void _rcu_barrier_complete(struct rcu_head *head)
784{
785 struct call_rcu_completion_work *work;
786 struct call_rcu_completion *completion;
787
788 work = caa_container_of(head, struct call_rcu_completion_work, head);
789 completion = work->completion;
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790 if (!uatomic_sub_return(&completion->barrier_count, 1))
791 call_rcu_completion_wake_up(completion);
792 urcu_ref_put(&completion->ref, free_completion);
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793 free(work);
794}
795
796/*
797 * Wait for all in-flight call_rcu callbacks to complete execution.
798 */
799void rcu_barrier(void)
800{
801 struct call_rcu_data *crdp;
81dd9134 802 struct call_rcu_completion *completion;
63f0fc6d 803 int count = 0;
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804 int was_online;
805
806 /* Put in offline state in QSBR. */
ffb4aaa7 807 was_online = _rcu_read_ongoing();
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808 if (was_online)
809 rcu_thread_offline();
810 /*
811 * Calling a rcu_barrier() within a RCU read-side critical
812 * section is an error.
813 */
ffb4aaa7 814 if (_rcu_read_ongoing()) {
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815 static int warned = 0;
816
817 if (!warned) {
818 fprintf(stderr, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
819 }
820 warned = 1;
821 goto online;
822 }
823
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824 completion = calloc(sizeof(*completion), 1);
825 if (!completion)
826 urcu_die(errno);
827
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828 call_rcu_lock(&call_rcu_mutex);
829 cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
830 count++;
831
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832 /* Referenced by rcu_barrier() and each call_rcu thread. */
833 urcu_ref_set(&completion->ref, count + 1);
834 completion->barrier_count = count;
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835
836 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
837 struct call_rcu_completion_work *work;
838
839 work = calloc(sizeof(*work), 1);
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840 if (!work)
841 urcu_die(errno);
81dd9134 842 work->completion = completion;
b7f721d9 843 _call_rcu(&work->head, _rcu_barrier_complete, crdp);
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844 }
845 call_rcu_unlock(&call_rcu_mutex);
846
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847 /* Wait for them */
848 for (;;) {
81dd9134 849 uatomic_dec(&completion->futex);
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850 /* Decrement futex before reading barrier_count */
851 cmm_smp_mb();
81dd9134 852 if (!uatomic_read(&completion->barrier_count))
b7f721d9 853 break;
81dd9134 854 call_rcu_completion_wait(completion);
b7f721d9 855 }
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856
857 urcu_ref_put(&completion->ref, free_completion);
858
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859online:
860 if (was_online)
861 rcu_thread_online();
862}
863
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864/*
865 * Acquire the call_rcu_mutex in order to ensure that the child sees
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866 * all of the call_rcu() data structures in a consistent state. Ensure
867 * that all call_rcu threads are in a quiescent state across fork.
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868 * Suitable for pthread_atfork() and friends.
869 */
870void call_rcu_before_fork(void)
871{
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872 struct call_rcu_data *crdp;
873
81ad2e19 874 call_rcu_lock(&call_rcu_mutex);
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875
876 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
877 uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSE);
878 cmm_smp_mb__after_uatomic_or();
879 wake_call_rcu_thread(crdp);
880 }
881 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
882 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0)
883 poll(NULL, 0, 1);
884 }
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885}
886
887/*
888 * Clean up call_rcu data structures in the parent of a successful fork()
889 * that is not followed by exec() in the child. Suitable for
890 * pthread_atfork() and friends.
891 */
892void call_rcu_after_fork_parent(void)
893{
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894 struct call_rcu_data *crdp;
895
896 cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
897 uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE);
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898 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
899 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) != 0)
900 poll(NULL, 0, 1);
901 }
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902 call_rcu_unlock(&call_rcu_mutex);
903}
904
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905/*
906 * Clean up call_rcu data structures in the child of a successful fork()
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907 * that is not followed by exec(). Suitable for pthread_atfork() and
908 * friends.
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909 */
910void call_rcu_after_fork_child(void)
911{
077ff173 912 struct call_rcu_data *crdp, *next;
7106ddf8 913
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914 /* Release the mutex. */
915 call_rcu_unlock(&call_rcu_mutex);
916
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917 /* Do nothing when call_rcu() has not been used */
918 if (cds_list_empty(&call_rcu_data_list))
919 return;
920
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921 /*
922 * Allocate a new default call_rcu_data structure in order
923 * to get a working call_rcu thread to go with it.
924 */
925 default_call_rcu_data = NULL;
926 (void)get_default_call_rcu_data();
927
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928 /* Cleanup call_rcu_data pointers before use */
929 maxcpus_reset();
930 free(per_cpu_call_rcu_data);
618b2595 931 rcu_set_pointer(&per_cpu_call_rcu_data, NULL);
bd252a04 932 URCU_TLS(thread_call_rcu_data) = NULL;
60af049d 933
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934 /*
935 * Dispose of all of the rest of the call_rcu_data structures.
936 * Leftover call_rcu callbacks will be merged into the new
937 * default call_rcu thread queue.
938 */
077ff173 939 cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
7106ddf8 940 if (crdp == default_call_rcu_data)
077ff173 941 continue;
2870aa1e 942 uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED);
7106ddf8 943 call_rcu_data_free(crdp);
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944 }
945}
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