Cleanup: remove leftover manual pthread detection
[urcu.git] / urcu-call-rcu-impl.h
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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"
a47dd11c 39#include "compat-getcpu.h"
5161f31e 40#include "urcu/wfcqueue.h"
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41#include "urcu-call-rcu.h"
42#include "urcu-pointer.h"
3c24913f 43#include "urcu/list.h"
41849996 44#include "urcu/futex.h"
bd252a04 45#include "urcu/tls-compat.h"
81dd9134 46#include "urcu/ref.h"
4a6d7378 47#include "urcu-die.h"
b57aee66 48
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49#define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */
50#define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1)
51
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52/* Data structure that identifies a call_rcu thread. */
53
54struct call_rcu_data {
5161f31e 55 /*
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56 * We do not align head on a different cache-line than tail
57 * mainly because call_rcu callback-invocation threads use
58 * batching ("splice") to get an entire list of callbacks, which
59 * effectively empties the queue, and requires to touch the tail
60 * anyway.
5161f31e 61 */
b9f893b6 62 struct cds_wfcq_tail cbs_tail;
0b8ab7df 63 struct cds_wfcq_head cbs_head;
b57aee66 64 unsigned long flags;
6d841bc2 65 int32_t futex;
73987721 66 unsigned long qlen; /* maintained for debugging. */
b57aee66 67 pthread_t tid;
c1d2c60b 68 int cpu_affinity;
8e3690db 69 unsigned long gp_count;
3c24913f 70 struct cds_list_head list;
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71} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
72
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73struct call_rcu_completion {
74 int barrier_count;
75 int32_t futex;
81dd9134 76 struct urcu_ref ref;
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77};
78
79struct call_rcu_completion_work {
80 struct rcu_head head;
81 struct call_rcu_completion *completion;
82};
83
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84/*
85 * List of all call_rcu_data structures to keep valgrind happy.
86 * Protected by call_rcu_mutex.
87 */
88
bab44e28 89static CDS_LIST_HEAD(call_rcu_data_list);
3c24913f 90
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91/* Link a thread using call_rcu() to its call_rcu thread. */
92
bd252a04 93static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data);
b57aee66 94
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95/*
96 * Guard call_rcu thread creation and atfork handlers.
97 */
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98static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
99
100/* If a given thread does not have its own call_rcu thread, this is default. */
101
102static struct call_rcu_data *default_call_rcu_data;
103
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104/*
105 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
106 * available, then we can have call_rcu threads assigned to individual
107 * CPUs rather than only to specific threads.
108 */
109
a47dd11c 110#if defined(HAVE_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID))
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111
112/*
113 * Pointer to array of pointers to per-CPU call_rcu_data structures
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114 * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an
115 * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a
116 * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer
117 * without mutex. The call_rcu_mutex protects updates.
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118 */
119
120static struct call_rcu_data **per_cpu_call_rcu_data;
121static long maxcpus;
122
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123static void maxcpus_reset(void)
124{
125 maxcpus = 0;
126}
127
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128/* Allocate the array if it has not already been allocated. */
129
130static void alloc_cpu_call_rcu_data(void)
131{
132 struct call_rcu_data **p;
133 static int warned = 0;
134
135 if (maxcpus != 0)
136 return;
137 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
138 if (maxcpus <= 0) {
139 return;
140 }
141 p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data));
142 if (p != NULL) {
143 memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data));
618b2595 144 rcu_set_pointer(&per_cpu_call_rcu_data, p);
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145 } else {
146 if (!warned) {
147 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
148 }
149 warned = 1;
150 }
151}
152
63b495d8 153#else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
b57aee66 154
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155/*
156 * per_cpu_call_rcu_data should be constant, but some functions below, used both
157 * for cases where cpu number is available and not available, assume it it not
158 * constant.
159 */
160static struct call_rcu_data **per_cpu_call_rcu_data = NULL;
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161static const long maxcpus = -1;
162
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163static void maxcpus_reset(void)
164{
165}
166
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167static void alloc_cpu_call_rcu_data(void)
168{
169}
170
63b495d8 171#endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
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172
173/* Acquire the specified pthread mutex. */
174
175static void call_rcu_lock(pthread_mutex_t *pmp)
176{
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177 int ret;
178
179 ret = pthread_mutex_lock(pmp);
180 if (ret)
181 urcu_die(ret);
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182}
183
184/* Release the specified pthread mutex. */
185
186static void call_rcu_unlock(pthread_mutex_t *pmp)
187{
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188 int ret;
189
190 ret = pthread_mutex_unlock(pmp);
191 if (ret)
192 urcu_die(ret);
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193}
194
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195/*
196 * Periodically retry setting CPU affinity if we migrate.
197 * Losing affinity can be caused by CPU hotunplug/hotplug, or by
198 * cpuset(7).
199 */
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200#if HAVE_SCHED_SETAFFINITY
201static
202int set_thread_cpu_affinity(struct call_rcu_data *crdp)
203{
204 cpu_set_t mask;
8e3690db 205 int ret;
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206
207 if (crdp->cpu_affinity < 0)
208 return 0;
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209 if (++crdp->gp_count & SET_AFFINITY_CHECK_PERIOD_MASK)
210 return 0;
211 if (urcu_sched_getcpu() == crdp->cpu_affinity)
212 return 0;
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213
214 CPU_ZERO(&mask);
215 CPU_SET(crdp->cpu_affinity, &mask);
216#if SCHED_SETAFFINITY_ARGS == 2
8e3690db 217 ret = sched_setaffinity(0, &mask);
c1d2c60b 218#else
8e3690db 219 ret = sched_setaffinity(0, sizeof(mask), &mask);
c1d2c60b 220#endif
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221 /*
222 * EINVAL is fine: can be caused by hotunplugged CPUs, or by
223 * cpuset(7). This is why we should always retry if we detect
224 * migration.
225 */
226 if (ret && errno == EINVAL) {
227 ret = 0;
228 errno = 0;
229 }
230 return ret;
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231}
232#else
233static
234int set_thread_cpu_affinity(struct call_rcu_data *crdp)
235{
236 return 0;
237}
238#endif
239
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240static void call_rcu_wait(struct call_rcu_data *crdp)
241{
242 /* Read call_rcu list before read futex */
243 cmm_smp_mb();
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244 if (uatomic_read(&crdp->futex) != -1)
245 return;
246 while (futex_async(&crdp->futex, FUTEX_WAIT, -1,
247 NULL, NULL, 0)) {
248 switch (errno) {
249 case EWOULDBLOCK:
250 /* Value already changed. */
251 return;
252 case EINTR:
253 /* Retry if interrupted by signal. */
254 break; /* Get out of switch. */
255 default:
256 /* Unexpected error. */
257 urcu_die(errno);
258 }
259 }
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260}
261
262static void call_rcu_wake_up(struct call_rcu_data *crdp)
263{
264 /* Write to call_rcu list before reading/writing futex */
265 cmm_smp_mb();
a0b7f7ea 266 if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) {
03fe58b3 267 uatomic_set(&crdp->futex, 0);
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268 if (futex_async(&crdp->futex, FUTEX_WAKE, 1,
269 NULL, NULL, 0) < 0)
270 urcu_die(errno);
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271 }
272}
273
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274static void call_rcu_completion_wait(struct call_rcu_completion *completion)
275{
276 /* Read completion barrier count before read futex */
277 cmm_smp_mb();
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278 if (uatomic_read(&completion->futex) != -1)
279 return;
280 while (futex_async(&completion->futex, FUTEX_WAIT, -1,
281 NULL, NULL, 0)) {
282 switch (errno) {
283 case EWOULDBLOCK:
284 /* Value already changed. */
285 return;
286 case EINTR:
287 /* Retry if interrupted by signal. */
288 break; /* Get out of switch. */
289 default:
290 /* Unexpected error. */
291 urcu_die(errno);
292 }
293 }
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294}
295
296static void call_rcu_completion_wake_up(struct call_rcu_completion *completion)
297{
298 /* Write to completion barrier count before reading/writing futex */
299 cmm_smp_mb();
300 if (caa_unlikely(uatomic_read(&completion->futex) == -1)) {
301 uatomic_set(&completion->futex, 0);
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302 if (futex_async(&completion->futex, FUTEX_WAKE, 1,
303 NULL, NULL, 0) < 0)
304 urcu_die(errno);
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305 }
306}
307
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308/* This is the code run by each call_rcu thread. */
309
310static void *call_rcu_thread(void *arg)
311{
312 unsigned long cbcount;
5161f31e 313 struct call_rcu_data *crdp = (struct call_rcu_data *) arg;
2870aa1e 314 int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT);
b57aee66 315
8e3690db 316 if (set_thread_cpu_affinity(crdp))
4a6d7378 317 urcu_die(errno);
c1d2c60b 318
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319 /*
320 * If callbacks take a read-side lock, we need to be registered.
321 */
322 rcu_register_thread();
323
bd252a04 324 URCU_TLS(thread_call_rcu_data) = crdp;
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325 if (!rt) {
326 uatomic_dec(&crdp->futex);
327 /* Decrement futex before reading call_rcu list */
328 cmm_smp_mb();
329 }
b57aee66 330 for (;;) {
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331 struct cds_wfcq_head cbs_tmp_head;
332 struct cds_wfcq_tail cbs_tmp_tail;
333 struct cds_wfcq_node *cbs, *cbs_tmp_n;
ae25b7e2 334 enum cds_wfcq_ret splice_ret;
5161f31e 335
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336 if (set_thread_cpu_affinity(crdp))
337 urcu_die(errno);
338
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339 if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) {
340 /*
341 * Pause requested. Become quiescent: remove
342 * ourself from all global lists, and don't
343 * process any callback. The callback lists may
344 * still be non-empty though.
345 */
346 rcu_unregister_thread();
347 cmm_smp_mb__before_uatomic_or();
348 uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED);
349 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0)
109105b7 350 (void) poll(NULL, 0, 1);
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351 uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED);
352 cmm_smp_mb__after_uatomic_and();
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353 rcu_register_thread();
354 }
355
5161f31e 356 cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
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357 splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head,
358 &cbs_tmp_tail, &crdp->cbs_head, &crdp->cbs_tail);
359 assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK);
360 assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY);
361 if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) {
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362 synchronize_rcu();
363 cbcount = 0;
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364 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head,
365 &cbs_tmp_tail, cbs, cbs_tmp_n) {
366 struct rcu_head *rhp;
367
368 rhp = caa_container_of(cbs,
369 struct rcu_head, next);
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370 rhp->func(rhp);
371 cbcount++;
5161f31e 372 }
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373 uatomic_sub(&crdp->qlen, cbcount);
374 }
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375 if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP)
376 break;
765f3ead 377 rcu_thread_offline();
bc94ca9b 378 if (!rt) {
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379 if (cds_wfcq_empty(&crdp->cbs_head,
380 &crdp->cbs_tail)) {
bc94ca9b 381 call_rcu_wait(crdp);
109105b7 382 (void) poll(NULL, 0, 10);
bc94ca9b 383 uatomic_dec(&crdp->futex);
c768e45e 384 /*
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385 * Decrement futex before reading
386 * call_rcu list.
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387 */
388 cmm_smp_mb();
ccbac24d 389 } else {
109105b7 390 (void) poll(NULL, 0, 10);
c768e45e 391 }
bc94ca9b 392 } else {
109105b7 393 (void) poll(NULL, 0, 10);
b57aee66 394 }
765f3ead 395 rcu_thread_online();
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396 }
397 if (!rt) {
398 /*
399 * Read call_rcu list before write futex.
400 */
401 cmm_smp_mb();
402 uatomic_set(&crdp->futex, 0);
b57aee66 403 }
2870aa1e 404 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED);
765f3ead 405 rcu_unregister_thread();
7106ddf8 406 return NULL;
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407}
408
409/*
410 * Create both a call_rcu thread and the corresponding call_rcu_data
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411 * structure, linking the structure in as specified. Caller must hold
412 * call_rcu_mutex.
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413 */
414
3c24913f 415static void call_rcu_data_init(struct call_rcu_data **crdpp,
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416 unsigned long flags,
417 int cpu_affinity)
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418{
419 struct call_rcu_data *crdp;
4a6d7378 420 int ret;
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421
422 crdp = malloc(sizeof(*crdp));
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423 if (crdp == NULL)
424 urcu_die(errno);
b57aee66 425 memset(crdp, '\0', sizeof(*crdp));
5161f31e 426 cds_wfcq_init(&crdp->cbs_head, &crdp->cbs_tail);
b57aee66 427 crdp->qlen = 0;
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428 crdp->futex = 0;
429 crdp->flags = flags;
3c24913f 430 cds_list_add(&crdp->list, &call_rcu_data_list);
c1d2c60b 431 crdp->cpu_affinity = cpu_affinity;
8e3690db 432 crdp->gp_count = 0;
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433 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
434 *crdpp = crdp;
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435 ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp);
436 if (ret)
437 urcu_die(ret);
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438}
439
440/*
441 * Return a pointer to the call_rcu_data structure for the specified
442 * CPU, returning NULL if there is none. We cannot automatically
443 * created it because the platform we are running on might not define
63b495d8 444 * urcu_sched_getcpu().
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445 *
446 * The call to this function and use of the returned call_rcu_data
447 * should be protected by RCU read-side lock.
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448 */
449
450struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
451{
452 static int warned = 0;
618b2595 453 struct call_rcu_data **pcpu_crdp;
b57aee66 454
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455 pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data);
456 if (pcpu_crdp == NULL)
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457 return NULL;
458 if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) {
459 fprintf(stderr, "[error] liburcu: get CPU # out of range\n");
460 warned = 1;
461 }
462 if (cpu < 0 || maxcpus <= cpu)
463 return NULL;
618b2595 464 return rcu_dereference(pcpu_crdp[cpu]);
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465}
466
467/*
468 * Return the tid corresponding to the call_rcu thread whose
469 * call_rcu_data structure is specified.
470 */
471
472pthread_t get_call_rcu_thread(struct call_rcu_data *crdp)
473{
474 return crdp->tid;
475}
476
477/*
478 * Create a call_rcu_data structure (with thread) and return a pointer.
479 */
480
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481static struct call_rcu_data *__create_call_rcu_data(unsigned long flags,
482 int cpu_affinity)
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483{
484 struct call_rcu_data *crdp;
485
c1d2c60b 486 call_rcu_data_init(&crdp, flags, cpu_affinity);
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487 return crdp;
488}
489
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490struct call_rcu_data *create_call_rcu_data(unsigned long flags,
491 int cpu_affinity)
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492{
493 struct call_rcu_data *crdp;
494
495 call_rcu_lock(&call_rcu_mutex);
c1d2c60b 496 crdp = __create_call_rcu_data(flags, cpu_affinity);
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497 call_rcu_unlock(&call_rcu_mutex);
498 return crdp;
499}
500
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501/*
502 * Set the specified CPU to use the specified call_rcu_data structure.
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503 *
504 * Use NULL to remove a CPU's call_rcu_data structure, but it is
505 * the caller's responsibility to dispose of the removed structure.
506 * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
507 * (prior to NULLing it out, of course).
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508 *
509 * The caller must wait for a grace-period to pass between return from
510 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
511 * previous call rcu data as argument.
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512 */
513
514int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
515{
dcfc8165 516 static int warned = 0;
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517
518 call_rcu_lock(&call_rcu_mutex);
f3776786 519 alloc_cpu_call_rcu_data();
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520 if (cpu < 0 || maxcpus <= cpu) {
521 if (!warned) {
522 fprintf(stderr, "[error] liburcu: set CPU # out of range\n");
523 warned = 1;
524 }
525 call_rcu_unlock(&call_rcu_mutex);
526 errno = EINVAL;
527 return -EINVAL;
528 }
53a55535 529
b57aee66 530 if (per_cpu_call_rcu_data == NULL) {
3670fef2 531 call_rcu_unlock(&call_rcu_mutex);
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532 errno = ENOMEM;
533 return -ENOMEM;
534 }
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535
536 if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) {
537 call_rcu_unlock(&call_rcu_mutex);
538 errno = EEXIST;
539 return -EEXIST;
540 }
541
618b2595 542 rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp);
3670fef2 543 call_rcu_unlock(&call_rcu_mutex);
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544 return 0;
545}
546
547/*
548 * Return a pointer to the default call_rcu_data structure, creating
549 * one if need be. Because we never free call_rcu_data structures,
550 * we don't need to be in an RCU read-side critical section.
551 */
552
553struct call_rcu_data *get_default_call_rcu_data(void)
554{
555 if (default_call_rcu_data != NULL)
556 return rcu_dereference(default_call_rcu_data);
557 call_rcu_lock(&call_rcu_mutex);
558 if (default_call_rcu_data != NULL) {
559 call_rcu_unlock(&call_rcu_mutex);
560 return default_call_rcu_data;
561 }
c1d2c60b 562 call_rcu_data_init(&default_call_rcu_data, 0, -1);
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563 call_rcu_unlock(&call_rcu_mutex);
564 return default_call_rcu_data;
565}
566
567/*
568 * Return the call_rcu_data structure that applies to the currently
569 * running thread. Any call_rcu_data structure assigned specifically
570 * to this thread has first priority, followed by any call_rcu_data
571 * structure assigned to the CPU on which the thread is running,
572 * followed by the default call_rcu_data structure. If there is not
573 * yet a default call_rcu_data structure, one will be created.
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574 *
575 * Calls to this function and use of the returned call_rcu_data should
576 * be protected by RCU read-side lock.
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577 */
578struct call_rcu_data *get_call_rcu_data(void)
579{
9744f3bb 580 struct call_rcu_data *crd;
b57aee66 581
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582 if (URCU_TLS(thread_call_rcu_data) != NULL)
583 return URCU_TLS(thread_call_rcu_data);
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584
585 if (maxcpus > 0) {
63b495d8 586 crd = get_cpu_call_rcu_data(urcu_sched_getcpu());
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587 if (crd)
588 return crd;
b57aee66 589 }
9744f3bb 590
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591 return get_default_call_rcu_data();
592}
593
594/*
595 * Return a pointer to this task's call_rcu_data if there is one.
596 */
597
598struct call_rcu_data *get_thread_call_rcu_data(void)
599{
bd252a04 600 return URCU_TLS(thread_call_rcu_data);
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601}
602
603/*
604 * Set this task's call_rcu_data structure as specified, regardless
605 * of whether or not this task already had one. (This allows switching
606 * to and from real-time call_rcu threads, for example.)
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607 *
608 * Use NULL to remove a thread's call_rcu_data structure, but it is
609 * the caller's responsibility to dispose of the removed structure.
610 * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
611 * (prior to NULLing it out, of course).
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612 */
613
614void set_thread_call_rcu_data(struct call_rcu_data *crdp)
615{
bd252a04 616 URCU_TLS(thread_call_rcu_data) = crdp;
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617}
618
619/*
620 * Create a separate call_rcu thread for each CPU. This does not
621 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
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622 * function if you want that behavior. Should be paired with
623 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
624 * threads.
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625 */
626
627int create_all_cpu_call_rcu_data(unsigned long flags)
628{
629 int i;
630 struct call_rcu_data *crdp;
631 int ret;
632
633 call_rcu_lock(&call_rcu_mutex);
634 alloc_cpu_call_rcu_data();
635 call_rcu_unlock(&call_rcu_mutex);
636 if (maxcpus <= 0) {
637 errno = EINVAL;
638 return -EINVAL;
639 }
640 if (per_cpu_call_rcu_data == NULL) {
641 errno = ENOMEM;
642 return -ENOMEM;
643 }
644 for (i = 0; i < maxcpus; i++) {
645 call_rcu_lock(&call_rcu_mutex);
646 if (get_cpu_call_rcu_data(i)) {
647 call_rcu_unlock(&call_rcu_mutex);
648 continue;
649 }
c1d2c60b 650 crdp = __create_call_rcu_data(flags, i);
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651 if (crdp == NULL) {
652 call_rcu_unlock(&call_rcu_mutex);
653 errno = ENOMEM;
654 return -ENOMEM;
655 }
656 call_rcu_unlock(&call_rcu_mutex);
657 if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) {
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658 call_rcu_data_free(crdp);
659
660 /* it has been created by other thread */
661 if (ret == -EEXIST)
662 continue;
663
664 return ret;
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665 }
666 }
667 return 0;
668}
669
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670/*
671 * Wake up the call_rcu thread corresponding to the specified
672 * call_rcu_data structure.
673 */
674static void wake_call_rcu_thread(struct call_rcu_data *crdp)
675{
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676 if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT))
677 call_rcu_wake_up(crdp);
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678}
679
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680static void _call_rcu(struct rcu_head *head,
681 void (*func)(struct rcu_head *head),
682 struct call_rcu_data *crdp)
683{
684 cds_wfcq_node_init(&head->next);
685 head->func = func;
686 cds_wfcq_enqueue(&crdp->cbs_head, &crdp->cbs_tail, &head->next);
687 uatomic_inc(&crdp->qlen);
688 wake_call_rcu_thread(crdp);
689}
690
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691/*
692 * Schedule a function to be invoked after a following grace period.
693 * This is the only function that must be called -- the others are
694 * only present to allow applications to tune their use of RCU for
695 * maximum performance.
696 *
697 * Note that unless a call_rcu thread has not already been created,
698 * the first invocation of call_rcu() will create one. So, if you
699 * need the first invocation of call_rcu() to be fast, make sure
700 * to create a call_rcu thread first. One way to accomplish this is
701 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
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702 *
703 * call_rcu must be called by registered RCU read-side threads.
b57aee66 704 */
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705void call_rcu(struct rcu_head *head,
706 void (*func)(struct rcu_head *head))
707{
708 struct call_rcu_data *crdp;
709
618b2595 710 /* Holding rcu read-side lock across use of per-cpu crdp */
ffb4aaa7 711 _rcu_read_lock();
b57aee66 712 crdp = get_call_rcu_data();
b7f721d9 713 _call_rcu(head, func, crdp);
ffb4aaa7 714 _rcu_read_unlock();
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715}
716
717/*
718 * Free up the specified call_rcu_data structure, terminating the
719 * associated call_rcu thread. The caller must have previously
720 * removed the call_rcu_data structure from per-thread or per-CPU
721 * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
722 * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
723 * per-thread call_rcu_data structures.
724 *
725 * We silently refuse to free up the default call_rcu_data structure
726 * because that is where we put any leftover callbacks. Note that
727 * the possibility of self-spawning callbacks makes it impossible
728 * to execute all the callbacks in finite time without putting any
729 * newly spawned callbacks somewhere else. The "somewhere else" of
730 * last resort is the default call_rcu_data structure.
731 *
732 * We also silently refuse to free NULL pointers. This simplifies
733 * the calling code.
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734 *
735 * The caller must wait for a grace-period to pass between return from
736 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
737 * previous call rcu data as argument.
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738 *
739 * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
740 * a list corruption bug in the 0.7.x series. The equivalent fix
741 * appeared in 0.6.8 for the stable-0.6 branch.
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742 */
743void call_rcu_data_free(struct call_rcu_data *crdp)
744{
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745 if (crdp == NULL || crdp == default_call_rcu_data) {
746 return;
747 }
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748 if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) {
749 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP);
7106ddf8 750 wake_call_rcu_thread(crdp);
2870aa1e 751 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0)
109105b7 752 (void) poll(NULL, 0, 1);
7106ddf8 753 }
5161f31e 754 if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) {
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755 /* Create default call rcu data if need be */
756 (void) get_default_call_rcu_data();
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757 __cds_wfcq_splice_blocking(&default_call_rcu_data->cbs_head,
758 &default_call_rcu_data->cbs_tail,
759 &crdp->cbs_head, &crdp->cbs_tail);
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760 uatomic_add(&default_call_rcu_data->qlen,
761 uatomic_read(&crdp->qlen));
1e92aa15 762 wake_call_rcu_thread(default_call_rcu_data);
7106ddf8 763 }
59dc9e9d 764
b75dffe6 765 call_rcu_lock(&call_rcu_mutex);
59dc9e9d 766 cds_list_del(&crdp->list);
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767 call_rcu_unlock(&call_rcu_mutex);
768
59dc9e9d 769 free(crdp);
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770}
771
772/*
773 * Clean up all the per-CPU call_rcu threads.
774 */
775void free_all_cpu_call_rcu_data(void)
776{
777 int cpu;
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778 struct call_rcu_data **crdp;
779 static int warned = 0;
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780
781 if (maxcpus <= 0)
782 return;
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783
784 crdp = malloc(sizeof(*crdp) * maxcpus);
785 if (!crdp) {
786 if (!warned) {
787 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
788 }
789 warned = 1;
d31150b4 790 return;
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791 }
792
7106ddf8 793 for (cpu = 0; cpu < maxcpus; cpu++) {
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794 crdp[cpu] = get_cpu_call_rcu_data(cpu);
795 if (crdp[cpu] == NULL)
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796 continue;
797 set_cpu_call_rcu_data(cpu, NULL);
7106ddf8 798 }
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799 /*
800 * Wait for call_rcu sites acting as RCU readers of the
801 * call_rcu_data to become quiescent.
802 */
803 synchronize_rcu();
804 for (cpu = 0; cpu < maxcpus; cpu++) {
805 if (crdp[cpu] == NULL)
806 continue;
807 call_rcu_data_free(crdp[cpu]);
808 }
809 free(crdp);
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810}
811
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812static
813void free_completion(struct urcu_ref *ref)
814{
815 struct call_rcu_completion *completion;
816
817 completion = caa_container_of(ref, struct call_rcu_completion, ref);
818 free(completion);
819}
820
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821static
822void _rcu_barrier_complete(struct rcu_head *head)
823{
824 struct call_rcu_completion_work *work;
825 struct call_rcu_completion *completion;
826
827 work = caa_container_of(head, struct call_rcu_completion_work, head);
828 completion = work->completion;
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829 if (!uatomic_sub_return(&completion->barrier_count, 1))
830 call_rcu_completion_wake_up(completion);
831 urcu_ref_put(&completion->ref, free_completion);
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832 free(work);
833}
834
835/*
836 * Wait for all in-flight call_rcu callbacks to complete execution.
837 */
838void rcu_barrier(void)
839{
840 struct call_rcu_data *crdp;
81dd9134 841 struct call_rcu_completion *completion;
63f0fc6d 842 int count = 0;
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843 int was_online;
844
845 /* Put in offline state in QSBR. */
ffb4aaa7 846 was_online = _rcu_read_ongoing();
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847 if (was_online)
848 rcu_thread_offline();
849 /*
850 * Calling a rcu_barrier() within a RCU read-side critical
851 * section is an error.
852 */
ffb4aaa7 853 if (_rcu_read_ongoing()) {
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854 static int warned = 0;
855
856 if (!warned) {
857 fprintf(stderr, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
858 }
859 warned = 1;
860 goto online;
861 }
862
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863 completion = calloc(sizeof(*completion), 1);
864 if (!completion)
865 urcu_die(errno);
866
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867 call_rcu_lock(&call_rcu_mutex);
868 cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
869 count++;
870
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871 /* Referenced by rcu_barrier() and each call_rcu thread. */
872 urcu_ref_set(&completion->ref, count + 1);
873 completion->barrier_count = count;
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874
875 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
876 struct call_rcu_completion_work *work;
877
878 work = calloc(sizeof(*work), 1);
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879 if (!work)
880 urcu_die(errno);
81dd9134 881 work->completion = completion;
b7f721d9 882 _call_rcu(&work->head, _rcu_barrier_complete, crdp);
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883 }
884 call_rcu_unlock(&call_rcu_mutex);
885
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886 /* Wait for them */
887 for (;;) {
81dd9134 888 uatomic_dec(&completion->futex);
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889 /* Decrement futex before reading barrier_count */
890 cmm_smp_mb();
81dd9134 891 if (!uatomic_read(&completion->barrier_count))
b7f721d9 892 break;
81dd9134 893 call_rcu_completion_wait(completion);
b7f721d9 894 }
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895
896 urcu_ref_put(&completion->ref, free_completion);
897
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898online:
899 if (was_online)
900 rcu_thread_online();
901}
902
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903/*
904 * Acquire the call_rcu_mutex in order to ensure that the child sees
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905 * all of the call_rcu() data structures in a consistent state. Ensure
906 * that all call_rcu threads are in a quiescent state across fork.
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907 * Suitable for pthread_atfork() and friends.
908 */
909void call_rcu_before_fork(void)
910{
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911 struct call_rcu_data *crdp;
912
81ad2e19 913 call_rcu_lock(&call_rcu_mutex);
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914
915 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
916 uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSE);
917 cmm_smp_mb__after_uatomic_or();
918 wake_call_rcu_thread(crdp);
919 }
920 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
921 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0)
109105b7 922 (void) poll(NULL, 0, 1);
e85451a1 923 }
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924}
925
926/*
927 * Clean up call_rcu data structures in the parent of a successful fork()
928 * that is not followed by exec() in the child. Suitable for
929 * pthread_atfork() and friends.
930 */
931void call_rcu_after_fork_parent(void)
932{
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933 struct call_rcu_data *crdp;
934
935 cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
936 uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE);
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937 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
938 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) != 0)
109105b7 939 (void) poll(NULL, 0, 1);
fc236e5e 940 }
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941 call_rcu_unlock(&call_rcu_mutex);
942}
943
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944/*
945 * Clean up call_rcu data structures in the child of a successful fork()
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946 * that is not followed by exec(). Suitable for pthread_atfork() and
947 * friends.
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948 */
949void call_rcu_after_fork_child(void)
950{
077ff173 951 struct call_rcu_data *crdp, *next;
7106ddf8 952
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953 /* Release the mutex. */
954 call_rcu_unlock(&call_rcu_mutex);
955
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956 /* Do nothing when call_rcu() has not been used */
957 if (cds_list_empty(&call_rcu_data_list))
958 return;
959
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960 /*
961 * Allocate a new default call_rcu_data structure in order
962 * to get a working call_rcu thread to go with it.
963 */
964 default_call_rcu_data = NULL;
965 (void)get_default_call_rcu_data();
966
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967 /* Cleanup call_rcu_data pointers before use */
968 maxcpus_reset();
969 free(per_cpu_call_rcu_data);
618b2595 970 rcu_set_pointer(&per_cpu_call_rcu_data, NULL);
bd252a04 971 URCU_TLS(thread_call_rcu_data) = NULL;
60af049d 972
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973 /*
974 * Dispose of all of the rest of the call_rcu_data structures.
975 * Leftover call_rcu callbacks will be merged into the new
976 * default call_rcu thread queue.
977 */
077ff173 978 cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
7106ddf8 979 if (crdp == default_call_rcu_data)
077ff173 980 continue;
2870aa1e 981 uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED);
7106ddf8 982 call_rcu_data_free(crdp);
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983 }
984}
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