Revert "Use initial-exec tls model"
[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"
5161f31e 38#include "urcu/wfcqueue.h"
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39#include "urcu-call-rcu.h"
40#include "urcu-pointer.h"
3c24913f 41#include "urcu/list.h"
41849996 42#include "urcu/futex.h"
bd252a04 43#include "urcu/tls-compat.h"
81dd9134 44#include "urcu/ref.h"
4a6d7378 45#include "urcu-die.h"
b57aee66 46
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47#define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */
48#define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1)
49
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50/* Data structure that identifies a call_rcu thread. */
51
52struct call_rcu_data {
5161f31e 53 /*
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54 * We do not align head on a different cache-line than tail
55 * mainly because call_rcu callback-invocation threads use
56 * batching ("splice") to get an entire list of callbacks, which
57 * effectively empties the queue, and requires to touch the tail
58 * anyway.
5161f31e 59 */
b9f893b6 60 struct cds_wfcq_tail cbs_tail;
0b8ab7df 61 struct cds_wfcq_head cbs_head;
b57aee66 62 unsigned long flags;
6d841bc2 63 int32_t futex;
73987721 64 unsigned long qlen; /* maintained for debugging. */
b57aee66 65 pthread_t tid;
c1d2c60b 66 int cpu_affinity;
8e3690db 67 unsigned long gp_count;
3c24913f 68 struct cds_list_head list;
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69} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
70
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71struct call_rcu_completion {
72 int barrier_count;
73 int32_t futex;
81dd9134 74 struct urcu_ref ref;
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75};
76
77struct call_rcu_completion_work {
78 struct rcu_head head;
79 struct call_rcu_completion *completion;
80};
81
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82/*
83 * List of all call_rcu_data structures to keep valgrind happy.
84 * Protected by call_rcu_mutex.
85 */
86
bab44e28 87static CDS_LIST_HEAD(call_rcu_data_list);
3c24913f 88
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89/* Link a thread using call_rcu() to its call_rcu thread. */
90
2f661865 91static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data);
b57aee66 92
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93/*
94 * Guard call_rcu thread creation and atfork handlers.
95 */
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96static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
97
98/* If a given thread does not have its own call_rcu thread, this is default. */
99
100static struct call_rcu_data *default_call_rcu_data;
101
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102static struct urcu_atfork *registered_rculfhash_atfork;
103static unsigned long registered_rculfhash_atfork_refcount;
104
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105/*
106 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
107 * available, then we can have call_rcu threads assigned to individual
108 * CPUs rather than only to specific threads.
109 */
110
a47dd11c 111#if defined(HAVE_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID))
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112
113/*
114 * Pointer to array of pointers to per-CPU call_rcu_data structures
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115 * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an
116 * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a
117 * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer
118 * without mutex. The call_rcu_mutex protects updates.
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119 */
120
121static struct call_rcu_data **per_cpu_call_rcu_data;
122static long maxcpus;
123
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124static void maxcpus_reset(void)
125{
126 maxcpus = 0;
127}
128
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129/* Allocate the array if it has not already been allocated. */
130
131static void alloc_cpu_call_rcu_data(void)
132{
133 struct call_rcu_data **p;
134 static int warned = 0;
135
136 if (maxcpus != 0)
137 return;
138 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
139 if (maxcpus <= 0) {
140 return;
141 }
142 p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data));
143 if (p != NULL) {
144 memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data));
618b2595 145 rcu_set_pointer(&per_cpu_call_rcu_data, p);
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146 } else {
147 if (!warned) {
148 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
149 }
150 warned = 1;
151 }
152}
153
63b495d8 154#else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
b57aee66 155
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156/*
157 * per_cpu_call_rcu_data should be constant, but some functions below, used both
158 * for cases where cpu number is available and not available, assume it it not
159 * constant.
160 */
161static struct call_rcu_data **per_cpu_call_rcu_data = NULL;
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162static const long maxcpus = -1;
163
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164static void maxcpus_reset(void)
165{
166}
167
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168static void alloc_cpu_call_rcu_data(void)
169{
170}
171
63b495d8 172#endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */
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173
174/* Acquire the specified pthread mutex. */
175
176static void call_rcu_lock(pthread_mutex_t *pmp)
177{
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178 int ret;
179
180 ret = pthread_mutex_lock(pmp);
181 if (ret)
182 urcu_die(ret);
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183}
184
185/* Release the specified pthread mutex. */
186
187static void call_rcu_unlock(pthread_mutex_t *pmp)
188{
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189 int ret;
190
191 ret = pthread_mutex_unlock(pmp);
192 if (ret)
193 urcu_die(ret);
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194}
195
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196/*
197 * Periodically retry setting CPU affinity if we migrate.
198 * Losing affinity can be caused by CPU hotunplug/hotplug, or by
199 * cpuset(7).
200 */
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201#if HAVE_SCHED_SETAFFINITY
202static
203int set_thread_cpu_affinity(struct call_rcu_data *crdp)
204{
205 cpu_set_t mask;
8e3690db 206 int ret;
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207
208 if (crdp->cpu_affinity < 0)
209 return 0;
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210 if (++crdp->gp_count & SET_AFFINITY_CHECK_PERIOD_MASK)
211 return 0;
212 if (urcu_sched_getcpu() == crdp->cpu_affinity)
213 return 0;
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214
215 CPU_ZERO(&mask);
216 CPU_SET(crdp->cpu_affinity, &mask);
217#if SCHED_SETAFFINITY_ARGS == 2
8e3690db 218 ret = sched_setaffinity(0, &mask);
c1d2c60b 219#else
8e3690db 220 ret = sched_setaffinity(0, sizeof(mask), &mask);
c1d2c60b 221#endif
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222 /*
223 * EINVAL is fine: can be caused by hotunplugged CPUs, or by
224 * cpuset(7). This is why we should always retry if we detect
225 * migration.
226 */
227 if (ret && errno == EINVAL) {
228 ret = 0;
229 errno = 0;
230 }
231 return ret;
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232}
233#else
234static
235int set_thread_cpu_affinity(struct call_rcu_data *crdp)
236{
237 return 0;
238}
239#endif
240
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241static void call_rcu_wait(struct call_rcu_data *crdp)
242{
243 /* Read call_rcu list before read futex */
244 cmm_smp_mb();
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245 if (uatomic_read(&crdp->futex) != -1)
246 return;
247 while (futex_async(&crdp->futex, FUTEX_WAIT, -1,
248 NULL, NULL, 0)) {
249 switch (errno) {
250 case EWOULDBLOCK:
251 /* Value already changed. */
252 return;
253 case EINTR:
254 /* Retry if interrupted by signal. */
255 break; /* Get out of switch. */
256 default:
257 /* Unexpected error. */
258 urcu_die(errno);
259 }
260 }
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261}
262
263static void call_rcu_wake_up(struct call_rcu_data *crdp)
264{
265 /* Write to call_rcu list before reading/writing futex */
266 cmm_smp_mb();
a0b7f7ea 267 if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) {
03fe58b3 268 uatomic_set(&crdp->futex, 0);
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269 if (futex_async(&crdp->futex, FUTEX_WAKE, 1,
270 NULL, NULL, 0) < 0)
271 urcu_die(errno);
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272 }
273}
274
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275static void call_rcu_completion_wait(struct call_rcu_completion *completion)
276{
277 /* Read completion barrier count before read futex */
278 cmm_smp_mb();
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279 if (uatomic_read(&completion->futex) != -1)
280 return;
281 while (futex_async(&completion->futex, FUTEX_WAIT, -1,
282 NULL, NULL, 0)) {
283 switch (errno) {
284 case EWOULDBLOCK:
285 /* Value already changed. */
286 return;
287 case EINTR:
288 /* Retry if interrupted by signal. */
289 break; /* Get out of switch. */
290 default:
291 /* Unexpected error. */
292 urcu_die(errno);
293 }
294 }
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295}
296
297static void call_rcu_completion_wake_up(struct call_rcu_completion *completion)
298{
299 /* Write to completion barrier count before reading/writing futex */
300 cmm_smp_mb();
301 if (caa_unlikely(uatomic_read(&completion->futex) == -1)) {
302 uatomic_set(&completion->futex, 0);
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303 if (futex_async(&completion->futex, FUTEX_WAKE, 1,
304 NULL, NULL, 0) < 0)
305 urcu_die(errno);
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306 }
307}
308
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309/* This is the code run by each call_rcu thread. */
310
311static void *call_rcu_thread(void *arg)
312{
313 unsigned long cbcount;
5161f31e 314 struct call_rcu_data *crdp = (struct call_rcu_data *) arg;
2870aa1e 315 int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT);
b57aee66 316
8e3690db 317 if (set_thread_cpu_affinity(crdp))
4a6d7378 318 urcu_die(errno);
c1d2c60b 319
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320 /*
321 * If callbacks take a read-side lock, we need to be registered.
322 */
323 rcu_register_thread();
324
bd252a04 325 URCU_TLS(thread_call_rcu_data) = crdp;
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326 if (!rt) {
327 uatomic_dec(&crdp->futex);
328 /* Decrement futex before reading call_rcu list */
329 cmm_smp_mb();
330 }
b57aee66 331 for (;;) {
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332 struct cds_wfcq_head cbs_tmp_head;
333 struct cds_wfcq_tail cbs_tmp_tail;
334 struct cds_wfcq_node *cbs, *cbs_tmp_n;
ae25b7e2 335 enum cds_wfcq_ret splice_ret;
5161f31e 336
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337 if (set_thread_cpu_affinity(crdp))
338 urcu_die(errno);
339
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340 if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) {
341 /*
342 * Pause requested. Become quiescent: remove
343 * ourself from all global lists, and don't
344 * process any callback. The callback lists may
345 * still be non-empty though.
346 */
347 rcu_unregister_thread();
348 cmm_smp_mb__before_uatomic_or();
349 uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED);
350 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0)
109105b7 351 (void) poll(NULL, 0, 1);
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352 uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED);
353 cmm_smp_mb__after_uatomic_and();
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354 rcu_register_thread();
355 }
356
5161f31e 357 cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
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358 splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head,
359 &cbs_tmp_tail, &crdp->cbs_head, &crdp->cbs_tail);
360 assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK);
361 assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY);
362 if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) {
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363 synchronize_rcu();
364 cbcount = 0;
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365 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head,
366 &cbs_tmp_tail, cbs, cbs_tmp_n) {
367 struct rcu_head *rhp;
368
369 rhp = caa_container_of(cbs,
370 struct rcu_head, next);
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371 rhp->func(rhp);
372 cbcount++;
5161f31e 373 }
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374 uatomic_sub(&crdp->qlen, cbcount);
375 }
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376 if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP)
377 break;
765f3ead 378 rcu_thread_offline();
bc94ca9b 379 if (!rt) {
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380 if (cds_wfcq_empty(&crdp->cbs_head,
381 &crdp->cbs_tail)) {
bc94ca9b 382 call_rcu_wait(crdp);
109105b7 383 (void) poll(NULL, 0, 10);
bc94ca9b 384 uatomic_dec(&crdp->futex);
c768e45e 385 /*
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386 * Decrement futex before reading
387 * call_rcu list.
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388 */
389 cmm_smp_mb();
ccbac24d 390 } else {
109105b7 391 (void) poll(NULL, 0, 10);
c768e45e 392 }
bc94ca9b 393 } else {
109105b7 394 (void) poll(NULL, 0, 10);
b57aee66 395 }
765f3ead 396 rcu_thread_online();
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397 }
398 if (!rt) {
399 /*
400 * Read call_rcu list before write futex.
401 */
402 cmm_smp_mb();
403 uatomic_set(&crdp->futex, 0);
b57aee66 404 }
2870aa1e 405 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED);
765f3ead 406 rcu_unregister_thread();
7106ddf8 407 return NULL;
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408}
409
410/*
411 * Create both a call_rcu thread and the corresponding call_rcu_data
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412 * structure, linking the structure in as specified. Caller must hold
413 * call_rcu_mutex.
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414 */
415
3c24913f 416static void call_rcu_data_init(struct call_rcu_data **crdpp,
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417 unsigned long flags,
418 int cpu_affinity)
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419{
420 struct call_rcu_data *crdp;
4a6d7378 421 int ret;
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422
423 crdp = malloc(sizeof(*crdp));
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424 if (crdp == NULL)
425 urcu_die(errno);
b57aee66 426 memset(crdp, '\0', sizeof(*crdp));
5161f31e 427 cds_wfcq_init(&crdp->cbs_head, &crdp->cbs_tail);
b57aee66 428 crdp->qlen = 0;
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429 crdp->futex = 0;
430 crdp->flags = flags;
3c24913f 431 cds_list_add(&crdp->list, &call_rcu_data_list);
c1d2c60b 432 crdp->cpu_affinity = cpu_affinity;
8e3690db 433 crdp->gp_count = 0;
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434 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
435 *crdpp = crdp;
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436 ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp);
437 if (ret)
438 urcu_die(ret);
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439}
440
441/*
442 * Return a pointer to the call_rcu_data structure for the specified
443 * CPU, returning NULL if there is none. We cannot automatically
444 * created it because the platform we are running on might not define
63b495d8 445 * urcu_sched_getcpu().
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446 *
447 * The call to this function and use of the returned call_rcu_data
448 * should be protected by RCU read-side lock.
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449 */
450
451struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
452{
453 static int warned = 0;
618b2595 454 struct call_rcu_data **pcpu_crdp;
b57aee66 455
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456 pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data);
457 if (pcpu_crdp == NULL)
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458 return NULL;
459 if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) {
460 fprintf(stderr, "[error] liburcu: get CPU # out of range\n");
461 warned = 1;
462 }
463 if (cpu < 0 || maxcpus <= cpu)
464 return NULL;
618b2595 465 return rcu_dereference(pcpu_crdp[cpu]);
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466}
467
468/*
469 * Return the tid corresponding to the call_rcu thread whose
470 * call_rcu_data structure is specified.
471 */
472
473pthread_t get_call_rcu_thread(struct call_rcu_data *crdp)
474{
475 return crdp->tid;
476}
477
478/*
479 * Create a call_rcu_data structure (with thread) and return a pointer.
480 */
481
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482static struct call_rcu_data *__create_call_rcu_data(unsigned long flags,
483 int cpu_affinity)
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484{
485 struct call_rcu_data *crdp;
486
c1d2c60b 487 call_rcu_data_init(&crdp, flags, cpu_affinity);
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488 return crdp;
489}
490
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491struct call_rcu_data *create_call_rcu_data(unsigned long flags,
492 int cpu_affinity)
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493{
494 struct call_rcu_data *crdp;
495
496 call_rcu_lock(&call_rcu_mutex);
c1d2c60b 497 crdp = __create_call_rcu_data(flags, cpu_affinity);
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498 call_rcu_unlock(&call_rcu_mutex);
499 return crdp;
500}
501
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502/*
503 * Set the specified CPU to use the specified call_rcu_data structure.
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504 *
505 * Use NULL to remove a CPU's call_rcu_data structure, but it is
506 * the caller's responsibility to dispose of the removed structure.
507 * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure
508 * (prior to NULLing it out, of course).
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509 *
510 * The caller must wait for a grace-period to pass between return from
511 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
512 * previous call rcu data as argument.
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513 */
514
515int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
516{
dcfc8165 517 static int warned = 0;
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518
519 call_rcu_lock(&call_rcu_mutex);
f3776786 520 alloc_cpu_call_rcu_data();
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521 if (cpu < 0 || maxcpus <= cpu) {
522 if (!warned) {
523 fprintf(stderr, "[error] liburcu: set CPU # out of range\n");
524 warned = 1;
525 }
526 call_rcu_unlock(&call_rcu_mutex);
527 errno = EINVAL;
528 return -EINVAL;
529 }
53a55535 530
b57aee66 531 if (per_cpu_call_rcu_data == NULL) {
3670fef2 532 call_rcu_unlock(&call_rcu_mutex);
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533 errno = ENOMEM;
534 return -ENOMEM;
535 }
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LJ
536
537 if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) {
538 call_rcu_unlock(&call_rcu_mutex);
539 errno = EEXIST;
540 return -EEXIST;
541 }
542
618b2595 543 rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp);
3670fef2 544 call_rcu_unlock(&call_rcu_mutex);
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545 return 0;
546}
547
548/*
549 * Return a pointer to the default call_rcu_data structure, creating
550 * one if need be. Because we never free call_rcu_data structures,
551 * we don't need to be in an RCU read-side critical section.
552 */
553
554struct call_rcu_data *get_default_call_rcu_data(void)
555{
556 if (default_call_rcu_data != NULL)
557 return rcu_dereference(default_call_rcu_data);
558 call_rcu_lock(&call_rcu_mutex);
559 if (default_call_rcu_data != NULL) {
560 call_rcu_unlock(&call_rcu_mutex);
561 return default_call_rcu_data;
562 }
c1d2c60b 563 call_rcu_data_init(&default_call_rcu_data, 0, -1);
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564 call_rcu_unlock(&call_rcu_mutex);
565 return default_call_rcu_data;
566}
567
568/*
569 * Return the call_rcu_data structure that applies to the currently
570 * running thread. Any call_rcu_data structure assigned specifically
571 * to this thread has first priority, followed by any call_rcu_data
572 * structure assigned to the CPU on which the thread is running,
573 * followed by the default call_rcu_data structure. If there is not
574 * yet a default call_rcu_data structure, one will be created.
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575 *
576 * Calls to this function and use of the returned call_rcu_data should
577 * be protected by RCU read-side lock.
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578 */
579struct call_rcu_data *get_call_rcu_data(void)
580{
9744f3bb 581 struct call_rcu_data *crd;
b57aee66 582
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583 if (URCU_TLS(thread_call_rcu_data) != NULL)
584 return URCU_TLS(thread_call_rcu_data);
9744f3bb
LJ
585
586 if (maxcpus > 0) {
63b495d8 587 crd = get_cpu_call_rcu_data(urcu_sched_getcpu());
9744f3bb
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588 if (crd)
589 return crd;
b57aee66 590 }
9744f3bb 591
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592 return get_default_call_rcu_data();
593}
594
595/*
596 * Return a pointer to this task's call_rcu_data if there is one.
597 */
598
599struct call_rcu_data *get_thread_call_rcu_data(void)
600{
bd252a04 601 return URCU_TLS(thread_call_rcu_data);
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602}
603
604/*
605 * Set this task's call_rcu_data structure as specified, regardless
606 * of whether or not this task already had one. (This allows switching
607 * to and from real-time call_rcu threads, for example.)
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608 *
609 * Use NULL to remove a thread's call_rcu_data structure, but it is
610 * the caller's responsibility to dispose of the removed structure.
611 * Use get_thread_call_rcu_data() to obtain a pointer to the old structure
612 * (prior to NULLing it out, of course).
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613 */
614
615void set_thread_call_rcu_data(struct call_rcu_data *crdp)
616{
bd252a04 617 URCU_TLS(thread_call_rcu_data) = crdp;
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618}
619
620/*
621 * Create a separate call_rcu thread for each CPU. This does not
622 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
0938c541
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623 * function if you want that behavior. Should be paired with
624 * free_all_cpu_call_rcu_data() to teardown these call_rcu worker
625 * threads.
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626 */
627
628int create_all_cpu_call_rcu_data(unsigned long flags)
629{
630 int i;
631 struct call_rcu_data *crdp;
632 int ret;
633
634 call_rcu_lock(&call_rcu_mutex);
635 alloc_cpu_call_rcu_data();
636 call_rcu_unlock(&call_rcu_mutex);
637 if (maxcpus <= 0) {
638 errno = EINVAL;
639 return -EINVAL;
640 }
641 if (per_cpu_call_rcu_data == NULL) {
642 errno = ENOMEM;
643 return -ENOMEM;
644 }
645 for (i = 0; i < maxcpus; i++) {
646 call_rcu_lock(&call_rcu_mutex);
647 if (get_cpu_call_rcu_data(i)) {
648 call_rcu_unlock(&call_rcu_mutex);
649 continue;
650 }
c1d2c60b 651 crdp = __create_call_rcu_data(flags, i);
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652 if (crdp == NULL) {
653 call_rcu_unlock(&call_rcu_mutex);
654 errno = ENOMEM;
655 return -ENOMEM;
656 }
657 call_rcu_unlock(&call_rcu_mutex);
658 if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) {
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659 call_rcu_data_free(crdp);
660
661 /* it has been created by other thread */
662 if (ret == -EEXIST)
663 continue;
664
665 return ret;
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666 }
667 }
668 return 0;
669}
670
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671/*
672 * Wake up the call_rcu thread corresponding to the specified
673 * call_rcu_data structure.
674 */
675static void wake_call_rcu_thread(struct call_rcu_data *crdp)
676{
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677 if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT))
678 call_rcu_wake_up(crdp);
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679}
680
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681static void _call_rcu(struct rcu_head *head,
682 void (*func)(struct rcu_head *head),
683 struct call_rcu_data *crdp)
684{
685 cds_wfcq_node_init(&head->next);
686 head->func = func;
687 cds_wfcq_enqueue(&crdp->cbs_head, &crdp->cbs_tail, &head->next);
688 uatomic_inc(&crdp->qlen);
689 wake_call_rcu_thread(crdp);
690}
691
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692/*
693 * Schedule a function to be invoked after a following grace period.
694 * This is the only function that must be called -- the others are
695 * only present to allow applications to tune their use of RCU for
696 * maximum performance.
697 *
698 * Note that unless a call_rcu thread has not already been created,
699 * the first invocation of call_rcu() will create one. So, if you
700 * need the first invocation of call_rcu() to be fast, make sure
701 * to create a call_rcu thread first. One way to accomplish this is
702 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
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703 *
704 * call_rcu must be called by registered RCU read-side threads.
b57aee66 705 */
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706void call_rcu(struct rcu_head *head,
707 void (*func)(struct rcu_head *head))
708{
709 struct call_rcu_data *crdp;
710
618b2595 711 /* Holding rcu read-side lock across use of per-cpu crdp */
ffb4aaa7 712 _rcu_read_lock();
b57aee66 713 crdp = get_call_rcu_data();
b7f721d9 714 _call_rcu(head, func, crdp);
ffb4aaa7 715 _rcu_read_unlock();
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716}
717
718/*
719 * Free up the specified call_rcu_data structure, terminating the
720 * associated call_rcu thread. The caller must have previously
721 * removed the call_rcu_data structure from per-thread or per-CPU
722 * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU
723 * call_rcu_data structures or set_thread_call_rcu_data(NULL) for
724 * per-thread call_rcu_data structures.
725 *
726 * We silently refuse to free up the default call_rcu_data structure
727 * because that is where we put any leftover callbacks. Note that
728 * the possibility of self-spawning callbacks makes it impossible
729 * to execute all the callbacks in finite time without putting any
730 * newly spawned callbacks somewhere else. The "somewhere else" of
731 * last resort is the default call_rcu_data structure.
732 *
733 * We also silently refuse to free NULL pointers. This simplifies
734 * the calling code.
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735 *
736 * The caller must wait for a grace-period to pass between return from
737 * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the
738 * previous call rcu data as argument.
03e5118f
MD
739 *
740 * Note: introducing __cds_wfcq_splice_blocking() in this function fixed
741 * a list corruption bug in the 0.7.x series. The equivalent fix
742 * appeared in 0.6.8 for the stable-0.6 branch.
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743 */
744void call_rcu_data_free(struct call_rcu_data *crdp)
745{
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746 if (crdp == NULL || crdp == default_call_rcu_data) {
747 return;
748 }
2870aa1e
PB
749 if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) {
750 uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP);
7106ddf8 751 wake_call_rcu_thread(crdp);
2870aa1e 752 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0)
109105b7 753 (void) poll(NULL, 0, 1);
7106ddf8 754 }
5161f31e 755 if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) {
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756 /* Create default call rcu data if need be */
757 (void) get_default_call_rcu_data();
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MD
758 __cds_wfcq_splice_blocking(&default_call_rcu_data->cbs_head,
759 &default_call_rcu_data->cbs_tail,
760 &crdp->cbs_head, &crdp->cbs_tail);
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761 uatomic_add(&default_call_rcu_data->qlen,
762 uatomic_read(&crdp->qlen));
1e92aa15 763 wake_call_rcu_thread(default_call_rcu_data);
7106ddf8 764 }
59dc9e9d 765
b75dffe6 766 call_rcu_lock(&call_rcu_mutex);
59dc9e9d 767 cds_list_del(&crdp->list);
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768 call_rcu_unlock(&call_rcu_mutex);
769
59dc9e9d 770 free(crdp);
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771}
772
773/*
774 * Clean up all the per-CPU call_rcu threads.
775 */
776void free_all_cpu_call_rcu_data(void)
777{
778 int cpu;
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779 struct call_rcu_data **crdp;
780 static int warned = 0;
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781
782 if (maxcpus <= 0)
783 return;
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784
785 crdp = malloc(sizeof(*crdp) * maxcpus);
786 if (!crdp) {
787 if (!warned) {
788 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
789 }
790 warned = 1;
d31150b4 791 return;
618b2595
MD
792 }
793
7106ddf8 794 for (cpu = 0; cpu < maxcpus; cpu++) {
618b2595
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795 crdp[cpu] = get_cpu_call_rcu_data(cpu);
796 if (crdp[cpu] == NULL)
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797 continue;
798 set_cpu_call_rcu_data(cpu, NULL);
7106ddf8 799 }
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800 /*
801 * Wait for call_rcu sites acting as RCU readers of the
802 * call_rcu_data to become quiescent.
803 */
804 synchronize_rcu();
805 for (cpu = 0; cpu < maxcpus; cpu++) {
806 if (crdp[cpu] == NULL)
807 continue;
808 call_rcu_data_free(crdp[cpu]);
809 }
810 free(crdp);
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811}
812
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813static
814void free_completion(struct urcu_ref *ref)
815{
816 struct call_rcu_completion *completion;
817
818 completion = caa_container_of(ref, struct call_rcu_completion, ref);
819 free(completion);
820}
821
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MD
822static
823void _rcu_barrier_complete(struct rcu_head *head)
824{
825 struct call_rcu_completion_work *work;
826 struct call_rcu_completion *completion;
827
828 work = caa_container_of(head, struct call_rcu_completion_work, head);
829 completion = work->completion;
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KF
830 if (!uatomic_sub_return(&completion->barrier_count, 1))
831 call_rcu_completion_wake_up(completion);
832 urcu_ref_put(&completion->ref, free_completion);
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MD
833 free(work);
834}
835
836/*
837 * Wait for all in-flight call_rcu callbacks to complete execution.
838 */
839void rcu_barrier(void)
840{
841 struct call_rcu_data *crdp;
81dd9134 842 struct call_rcu_completion *completion;
63f0fc6d 843 int count = 0;
b7f721d9
MD
844 int was_online;
845
846 /* Put in offline state in QSBR. */
ffb4aaa7 847 was_online = _rcu_read_ongoing();
b7f721d9
MD
848 if (was_online)
849 rcu_thread_offline();
850 /*
851 * Calling a rcu_barrier() within a RCU read-side critical
852 * section is an error.
853 */
ffb4aaa7 854 if (_rcu_read_ongoing()) {
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MD
855 static int warned = 0;
856
857 if (!warned) {
858 fprintf(stderr, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n");
859 }
860 warned = 1;
861 goto online;
862 }
863
81dd9134
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864 completion = calloc(sizeof(*completion), 1);
865 if (!completion)
866 urcu_die(errno);
867
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868 call_rcu_lock(&call_rcu_mutex);
869 cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
870 count++;
871
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872 /* Referenced by rcu_barrier() and each call_rcu thread. */
873 urcu_ref_set(&completion->ref, count + 1);
874 completion->barrier_count = count;
b7f721d9
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875
876 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
877 struct call_rcu_completion_work *work;
878
879 work = calloc(sizeof(*work), 1);
63f0fc6d
MD
880 if (!work)
881 urcu_die(errno);
81dd9134 882 work->completion = completion;
b7f721d9 883 _call_rcu(&work->head, _rcu_barrier_complete, crdp);
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884 }
885 call_rcu_unlock(&call_rcu_mutex);
886
b7f721d9
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887 /* Wait for them */
888 for (;;) {
81dd9134 889 uatomic_dec(&completion->futex);
b7f721d9
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890 /* Decrement futex before reading barrier_count */
891 cmm_smp_mb();
81dd9134 892 if (!uatomic_read(&completion->barrier_count))
b7f721d9 893 break;
81dd9134 894 call_rcu_completion_wait(completion);
b7f721d9 895 }
81dd9134
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896
897 urcu_ref_put(&completion->ref, free_completion);
898
b7f721d9
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899online:
900 if (was_online)
901 rcu_thread_online();
902}
903
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904/*
905 * Acquire the call_rcu_mutex in order to ensure that the child sees
e85451a1
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906 * all of the call_rcu() data structures in a consistent state. Ensure
907 * that all call_rcu threads are in a quiescent state across fork.
81ad2e19
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908 * Suitable for pthread_atfork() and friends.
909 */
910void call_rcu_before_fork(void)
911{
e85451a1 912 struct call_rcu_data *crdp;
d0ec0ed2 913 struct urcu_atfork *atfork;
e85451a1 914
81ad2e19 915 call_rcu_lock(&call_rcu_mutex);
e85451a1 916
d0ec0ed2
MD
917 atfork = registered_rculfhash_atfork;
918 if (atfork)
919 atfork->before_fork(atfork->priv);
920
e85451a1
MD
921 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
922 uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSE);
923 cmm_smp_mb__after_uatomic_or();
924 wake_call_rcu_thread(crdp);
925 }
926 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
927 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0)
109105b7 928 (void) poll(NULL, 0, 1);
e85451a1 929 }
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930}
931
932/*
933 * Clean up call_rcu data structures in the parent of a successful fork()
934 * that is not followed by exec() in the child. Suitable for
935 * pthread_atfork() and friends.
936 */
937void call_rcu_after_fork_parent(void)
938{
e85451a1 939 struct call_rcu_data *crdp;
d0ec0ed2 940 struct urcu_atfork *atfork;
e85451a1
MD
941
942 cds_list_for_each_entry(crdp, &call_rcu_data_list, list)
943 uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE);
fc236e5e
KF
944 cds_list_for_each_entry(crdp, &call_rcu_data_list, list) {
945 while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) != 0)
109105b7 946 (void) poll(NULL, 0, 1);
fc236e5e 947 }
d0ec0ed2
MD
948 atfork = registered_rculfhash_atfork;
949 if (atfork)
950 atfork->after_fork_parent(atfork->priv);
81ad2e19
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951 call_rcu_unlock(&call_rcu_mutex);
952}
953
7106ddf8
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954/*
955 * Clean up call_rcu data structures in the child of a successful fork()
81ad2e19
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956 * that is not followed by exec(). Suitable for pthread_atfork() and
957 * friends.
7106ddf8
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958 */
959void call_rcu_after_fork_child(void)
960{
077ff173 961 struct call_rcu_data *crdp, *next;
d0ec0ed2 962 struct urcu_atfork *atfork;
7106ddf8 963
81ad2e19
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964 /* Release the mutex. */
965 call_rcu_unlock(&call_rcu_mutex);
966
d0ec0ed2
MD
967 atfork = registered_rculfhash_atfork;
968 if (atfork)
969 atfork->after_fork_child(atfork->priv);
970
ad1b9909
LJ
971 /* Do nothing when call_rcu() has not been used */
972 if (cds_list_empty(&call_rcu_data_list))
973 return;
974
7106ddf8
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975 /*
976 * Allocate a new default call_rcu_data structure in order
977 * to get a working call_rcu thread to go with it.
978 */
979 default_call_rcu_data = NULL;
980 (void)get_default_call_rcu_data();
981
60af049d
LJ
982 /* Cleanup call_rcu_data pointers before use */
983 maxcpus_reset();
984 free(per_cpu_call_rcu_data);
618b2595 985 rcu_set_pointer(&per_cpu_call_rcu_data, NULL);
bd252a04 986 URCU_TLS(thread_call_rcu_data) = NULL;
60af049d 987
e85451a1
MD
988 /*
989 * Dispose of all of the rest of the call_rcu_data structures.
990 * Leftover call_rcu callbacks will be merged into the new
991 * default call_rcu thread queue.
992 */
077ff173 993 cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) {
7106ddf8 994 if (crdp == default_call_rcu_data)
077ff173 995 continue;
2870aa1e 996 uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED);
7106ddf8 997 call_rcu_data_free(crdp);
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998 }
999}
d0ec0ed2
MD
1000
1001void urcu_register_rculfhash_atfork(struct urcu_atfork *atfork)
1002{
1003 call_rcu_lock(&call_rcu_mutex);
1004 if (registered_rculfhash_atfork_refcount++)
1005 goto end;
1006 registered_rculfhash_atfork = atfork;
1007end:
1008 call_rcu_unlock(&call_rcu_mutex);
1009}
1010
1011void urcu_unregister_rculfhash_atfork(struct urcu_atfork *atfork)
1012{
1013 call_rcu_lock(&call_rcu_mutex);
1014 if (--registered_rculfhash_atfork_refcount)
1015 goto end;
1016 registered_rculfhash_atfork = NULL;
1017end:
1018 call_rcu_unlock(&call_rcu_mutex);
1019}
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