Commit | Line | Data |
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b57aee66 PM |
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 |
b57aee66 PM |
24 | #include <stdio.h> |
25 | #include <pthread.h> | |
26 | #include <signal.h> | |
b57aee66 | 27 | #include <stdlib.h> |
6d841bc2 | 28 | #include <stdint.h> |
b57aee66 PM |
29 | #include <string.h> |
30 | #include <errno.h> | |
31 | #include <poll.h> | |
32 | #include <sys/time.h> | |
b57aee66 | 33 | #include <unistd.h> |
c1d2c60b | 34 | #include <sched.h> |
b57aee66 | 35 | |
a47dd11c | 36 | #include "compat-getcpu.h" |
01477510 | 37 | #include <urcu/assert.h> |
4477a870 MD |
38 | #include <urcu/wfcqueue.h> |
39 | #include <urcu/call-rcu.h> | |
40 | #include <urcu/pointer.h> | |
41 | #include <urcu/list.h> | |
42 | #include <urcu/futex.h> | |
43 | #include <urcu/tls-compat.h> | |
44 | #include <urcu/ref.h> | |
4a6d7378 | 45 | #include "urcu-die.h" |
4477a870 | 46 | #include "urcu-utils.h" |
5cfe81b7 | 47 | #include "compat-smp.h" |
b57aee66 | 48 | |
8e3690db MD |
49 | #define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */ |
50 | #define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1) | |
51 | ||
b57aee66 PM |
52 | /* Data structure that identifies a call_rcu thread. */ |
53 | ||
54 | struct call_rcu_data { | |
5161f31e | 55 | /* |
0b8ab7df MD |
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; |
b57aee66 PM |
71 | } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
72 | ||
b7f721d9 MD |
73 | struct call_rcu_completion { |
74 | int barrier_count; | |
75 | int32_t futex; | |
81dd9134 | 76 | struct urcu_ref ref; |
b7f721d9 MD |
77 | }; |
78 | ||
79 | struct call_rcu_completion_work { | |
80 | struct rcu_head head; | |
81 | struct call_rcu_completion *completion; | |
82 | }; | |
83 | ||
1cf55ba4 MD |
84 | enum crdf_flags { |
85 | CRDF_FLAG_JOIN_THREAD = (1 << 0), | |
86 | }; | |
87 | ||
3c24913f PM |
88 | /* |
89 | * List of all call_rcu_data structures to keep valgrind happy. | |
90 | * Protected by call_rcu_mutex. | |
91 | */ | |
92 | ||
bab44e28 | 93 | static CDS_LIST_HEAD(call_rcu_data_list); |
3c24913f | 94 | |
b57aee66 PM |
95 | /* Link a thread using call_rcu() to its call_rcu thread. */ |
96 | ||
2f661865 | 97 | static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data); |
b57aee66 | 98 | |
e85451a1 MD |
99 | /* |
100 | * Guard call_rcu thread creation and atfork handlers. | |
101 | */ | |
b57aee66 PM |
102 | static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER; |
103 | ||
104 | /* If a given thread does not have its own call_rcu thread, this is default. */ | |
105 | ||
106 | static struct call_rcu_data *default_call_rcu_data; | |
107 | ||
d0ec0ed2 | 108 | static struct urcu_atfork *registered_rculfhash_atfork; |
d0ec0ed2 | 109 | |
b57aee66 PM |
110 | /* |
111 | * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are | |
112 | * available, then we can have call_rcu threads assigned to individual | |
113 | * CPUs rather than only to specific threads. | |
114 | */ | |
115 | ||
a47dd11c | 116 | #if defined(HAVE_SYSCONF) && (defined(HAVE_SCHED_GETCPU) || defined(HAVE_GETCPUID)) |
b57aee66 PM |
117 | |
118 | /* | |
119 | * Pointer to array of pointers to per-CPU call_rcu_data structures | |
618b2595 MD |
120 | * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an |
121 | * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a | |
122 | * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer | |
123 | * without mutex. The call_rcu_mutex protects updates. | |
b57aee66 PM |
124 | */ |
125 | ||
126 | static struct call_rcu_data **per_cpu_call_rcu_data; | |
5cfe81b7 | 127 | static long cpus_array_len; |
b57aee66 | 128 | |
5cfe81b7 | 129 | static void cpus_array_len_reset(void) |
60af049d | 130 | { |
5cfe81b7 | 131 | cpus_array_len = 0; |
60af049d LJ |
132 | } |
133 | ||
b57aee66 PM |
134 | /* Allocate the array if it has not already been allocated. */ |
135 | ||
136 | static void alloc_cpu_call_rcu_data(void) | |
137 | { | |
138 | struct call_rcu_data **p; | |
139 | static int warned = 0; | |
140 | ||
5cfe81b7 | 141 | if (cpus_array_len != 0) |
b57aee66 | 142 | return; |
5cfe81b7 MJ |
143 | cpus_array_len = get_possible_cpus_array_len(); |
144 | if (cpus_array_len <= 0) { | |
b57aee66 PM |
145 | return; |
146 | } | |
5cfe81b7 | 147 | p = malloc(cpus_array_len * sizeof(*per_cpu_call_rcu_data)); |
b57aee66 | 148 | if (p != NULL) { |
5cfe81b7 | 149 | memset(p, '\0', cpus_array_len * sizeof(*per_cpu_call_rcu_data)); |
618b2595 | 150 | rcu_set_pointer(&per_cpu_call_rcu_data, p); |
b57aee66 PM |
151 | } else { |
152 | if (!warned) { | |
153 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); | |
154 | } | |
155 | warned = 1; | |
156 | } | |
157 | } | |
158 | ||
63b495d8 | 159 | #else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */ |
b57aee66 | 160 | |
f9437098 MD |
161 | /* |
162 | * per_cpu_call_rcu_data should be constant, but some functions below, used both | |
163 | * for cases where cpu number is available and not available, assume it it not | |
164 | * constant. | |
165 | */ | |
166 | static struct call_rcu_data **per_cpu_call_rcu_data = NULL; | |
5cfe81b7 | 167 | static const long cpus_array_len = -1; |
b57aee66 | 168 | |
5cfe81b7 | 169 | static void cpus_array_len_reset(void) |
60af049d LJ |
170 | { |
171 | } | |
172 | ||
b57aee66 PM |
173 | static void alloc_cpu_call_rcu_data(void) |
174 | { | |
175 | } | |
176 | ||
63b495d8 | 177 | #endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */ |
b57aee66 PM |
178 | |
179 | /* Acquire the specified pthread mutex. */ | |
180 | ||
181 | static void call_rcu_lock(pthread_mutex_t *pmp) | |
182 | { | |
4a6d7378 MD |
183 | int ret; |
184 | ||
185 | ret = pthread_mutex_lock(pmp); | |
186 | if (ret) | |
187 | urcu_die(ret); | |
b57aee66 PM |
188 | } |
189 | ||
190 | /* Release the specified pthread mutex. */ | |
191 | ||
192 | static void call_rcu_unlock(pthread_mutex_t *pmp) | |
193 | { | |
4a6d7378 MD |
194 | int ret; |
195 | ||
196 | ret = pthread_mutex_unlock(pmp); | |
197 | if (ret) | |
198 | urcu_die(ret); | |
b57aee66 PM |
199 | } |
200 | ||
8e3690db MD |
201 | /* |
202 | * Periodically retry setting CPU affinity if we migrate. | |
203 | * Losing affinity can be caused by CPU hotunplug/hotplug, or by | |
204 | * cpuset(7). | |
205 | */ | |
2388c075 | 206 | #ifdef HAVE_SCHED_SETAFFINITY |
c1d2c60b MD |
207 | static |
208 | int set_thread_cpu_affinity(struct call_rcu_data *crdp) | |
209 | { | |
210 | cpu_set_t mask; | |
8e3690db | 211 | int ret; |
c1d2c60b MD |
212 | |
213 | if (crdp->cpu_affinity < 0) | |
214 | return 0; | |
8e3690db MD |
215 | if (++crdp->gp_count & SET_AFFINITY_CHECK_PERIOD_MASK) |
216 | return 0; | |
217 | if (urcu_sched_getcpu() == crdp->cpu_affinity) | |
218 | return 0; | |
c1d2c60b MD |
219 | |
220 | CPU_ZERO(&mask); | |
221 | CPU_SET(crdp->cpu_affinity, &mask); | |
8e3690db | 222 | ret = sched_setaffinity(0, sizeof(mask), &mask); |
0614a2e6 | 223 | |
8e3690db MD |
224 | /* |
225 | * EINVAL is fine: can be caused by hotunplugged CPUs, or by | |
226 | * cpuset(7). This is why we should always retry if we detect | |
227 | * migration. | |
228 | */ | |
229 | if (ret && errno == EINVAL) { | |
230 | ret = 0; | |
231 | errno = 0; | |
232 | } | |
233 | return ret; | |
c1d2c60b MD |
234 | } |
235 | #else | |
236 | static | |
a142df4e | 237 | int set_thread_cpu_affinity(struct call_rcu_data *crdp __attribute__((unused))) |
c1d2c60b MD |
238 | { |
239 | return 0; | |
240 | } | |
241 | #endif | |
242 | ||
03fe58b3 MD |
243 | static void call_rcu_wait(struct call_rcu_data *crdp) |
244 | { | |
245 | /* Read call_rcu list before read futex */ | |
246 | cmm_smp_mb(); | |
98d705dd MD |
247 | while (uatomic_read(&crdp->futex) == -1) { |
248 | if (!futex_async(&crdp->futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { | |
249 | /* | |
250 | * Prior queued wakeups queued by unrelated code | |
251 | * using the same address can cause futex wait to | |
252 | * return 0 even through the futex value is still | |
253 | * -1 (spurious wakeups). Check the value again | |
254 | * in user-space to validate whether it really | |
255 | * differs from -1. | |
256 | */ | |
257 | continue; | |
258 | } | |
b0a841b4 | 259 | switch (errno) { |
98d705dd | 260 | case EAGAIN: |
b0a841b4 MD |
261 | /* Value already changed. */ |
262 | return; | |
263 | case EINTR: | |
264 | /* Retry if interrupted by signal. */ | |
98d705dd | 265 | break; /* Get out of switch. Check again. */ |
b0a841b4 MD |
266 | default: |
267 | /* Unexpected error. */ | |
268 | urcu_die(errno); | |
269 | } | |
270 | } | |
03fe58b3 MD |
271 | } |
272 | ||
273 | static void call_rcu_wake_up(struct call_rcu_data *crdp) | |
274 | { | |
275 | /* Write to call_rcu list before reading/writing futex */ | |
276 | cmm_smp_mb(); | |
a0b7f7ea | 277 | if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) { |
03fe58b3 | 278 | uatomic_set(&crdp->futex, 0); |
b0a841b4 MD |
279 | if (futex_async(&crdp->futex, FUTEX_WAKE, 1, |
280 | NULL, NULL, 0) < 0) | |
281 | urcu_die(errno); | |
03fe58b3 MD |
282 | } |
283 | } | |
284 | ||
b7f721d9 MD |
285 | static void call_rcu_completion_wait(struct call_rcu_completion *completion) |
286 | { | |
287 | /* Read completion barrier count before read futex */ | |
288 | cmm_smp_mb(); | |
98d705dd MD |
289 | while (uatomic_read(&completion->futex) == -1) { |
290 | if (!futex_async(&completion->futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { | |
291 | /* | |
292 | * Prior queued wakeups queued by unrelated code | |
293 | * using the same address can cause futex wait to | |
294 | * return 0 even through the futex value is still | |
295 | * -1 (spurious wakeups). Check the value again | |
296 | * in user-space to validate whether it really | |
297 | * differs from -1. | |
298 | */ | |
299 | continue; | |
300 | } | |
b0a841b4 | 301 | switch (errno) { |
98d705dd | 302 | case EAGAIN: |
b0a841b4 MD |
303 | /* Value already changed. */ |
304 | return; | |
305 | case EINTR: | |
306 | /* Retry if interrupted by signal. */ | |
98d705dd | 307 | break; /* Get out of switch. Check again. */ |
b0a841b4 MD |
308 | default: |
309 | /* Unexpected error. */ | |
310 | urcu_die(errno); | |
311 | } | |
312 | } | |
b7f721d9 MD |
313 | } |
314 | ||
315 | static void call_rcu_completion_wake_up(struct call_rcu_completion *completion) | |
316 | { | |
317 | /* Write to completion barrier count before reading/writing futex */ | |
318 | cmm_smp_mb(); | |
319 | if (caa_unlikely(uatomic_read(&completion->futex) == -1)) { | |
320 | uatomic_set(&completion->futex, 0); | |
b0a841b4 MD |
321 | if (futex_async(&completion->futex, FUTEX_WAKE, 1, |
322 | NULL, NULL, 0) < 0) | |
323 | urcu_die(errno); | |
b7f721d9 MD |
324 | } |
325 | } | |
326 | ||
b57aee66 PM |
327 | /* This is the code run by each call_rcu thread. */ |
328 | ||
329 | static void *call_rcu_thread(void *arg) | |
330 | { | |
331 | unsigned long cbcount; | |
5161f31e | 332 | struct call_rcu_data *crdp = (struct call_rcu_data *) arg; |
2870aa1e | 333 | int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT); |
b57aee66 | 334 | |
8e3690db | 335 | if (set_thread_cpu_affinity(crdp)) |
4a6d7378 | 336 | urcu_die(errno); |
c1d2c60b | 337 | |
765f3ead MD |
338 | /* |
339 | * If callbacks take a read-side lock, we need to be registered. | |
340 | */ | |
341 | rcu_register_thread(); | |
342 | ||
bd252a04 | 343 | URCU_TLS(thread_call_rcu_data) = crdp; |
bc94ca9b MD |
344 | if (!rt) { |
345 | uatomic_dec(&crdp->futex); | |
346 | /* Decrement futex before reading call_rcu list */ | |
347 | cmm_smp_mb(); | |
348 | } | |
b57aee66 | 349 | for (;;) { |
5161f31e MD |
350 | struct cds_wfcq_head cbs_tmp_head; |
351 | struct cds_wfcq_tail cbs_tmp_tail; | |
352 | struct cds_wfcq_node *cbs, *cbs_tmp_n; | |
ae25b7e2 | 353 | enum cds_wfcq_ret splice_ret; |
5161f31e | 354 | |
8e3690db MD |
355 | if (set_thread_cpu_affinity(crdp)) |
356 | urcu_die(errno); | |
357 | ||
e85451a1 MD |
358 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) { |
359 | /* | |
360 | * Pause requested. Become quiescent: remove | |
361 | * ourself from all global lists, and don't | |
362 | * process any callback. The callback lists may | |
363 | * still be non-empty though. | |
364 | */ | |
365 | rcu_unregister_thread(); | |
366 | cmm_smp_mb__before_uatomic_or(); | |
367 | uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED); | |
368 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0) | |
109105b7 | 369 | (void) poll(NULL, 0, 1); |
fc236e5e KF |
370 | uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED); |
371 | cmm_smp_mb__after_uatomic_and(); | |
e85451a1 MD |
372 | rcu_register_thread(); |
373 | } | |
374 | ||
5161f31e | 375 | cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail); |
ae25b7e2 MD |
376 | splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head, |
377 | &cbs_tmp_tail, &crdp->cbs_head, &crdp->cbs_tail); | |
01477510 FD |
378 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK); |
379 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY); | |
ae25b7e2 | 380 | if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) { |
b57aee66 PM |
381 | synchronize_rcu(); |
382 | cbcount = 0; | |
5161f31e MD |
383 | __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head, |
384 | &cbs_tmp_tail, cbs, cbs_tmp_n) { | |
385 | struct rcu_head *rhp; | |
386 | ||
387 | rhp = caa_container_of(cbs, | |
388 | struct rcu_head, next); | |
b57aee66 PM |
389 | rhp->func(rhp); |
390 | cbcount++; | |
5161f31e | 391 | } |
b57aee66 PM |
392 | uatomic_sub(&crdp->qlen, cbcount); |
393 | } | |
bc94ca9b MD |
394 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP) |
395 | break; | |
765f3ead | 396 | rcu_thread_offline(); |
bc94ca9b | 397 | if (!rt) { |
5161f31e MD |
398 | if (cds_wfcq_empty(&crdp->cbs_head, |
399 | &crdp->cbs_tail)) { | |
bc94ca9b | 400 | call_rcu_wait(crdp); |
109105b7 | 401 | (void) poll(NULL, 0, 10); |
bc94ca9b | 402 | uatomic_dec(&crdp->futex); |
c768e45e | 403 | /* |
bc94ca9b MD |
404 | * Decrement futex before reading |
405 | * call_rcu list. | |
c768e45e MD |
406 | */ |
407 | cmm_smp_mb(); | |
ccbac24d | 408 | } else { |
109105b7 | 409 | (void) poll(NULL, 0, 10); |
c768e45e | 410 | } |
bc94ca9b | 411 | } else { |
109105b7 | 412 | (void) poll(NULL, 0, 10); |
b57aee66 | 413 | } |
765f3ead | 414 | rcu_thread_online(); |
bc94ca9b MD |
415 | } |
416 | if (!rt) { | |
417 | /* | |
418 | * Read call_rcu list before write futex. | |
419 | */ | |
420 | cmm_smp_mb(); | |
421 | uatomic_set(&crdp->futex, 0); | |
b57aee66 | 422 | } |
2870aa1e | 423 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED); |
765f3ead | 424 | rcu_unregister_thread(); |
7106ddf8 | 425 | return NULL; |
b57aee66 PM |
426 | } |
427 | ||
428 | /* | |
429 | * Create both a call_rcu thread and the corresponding call_rcu_data | |
3c24913f PM |
430 | * structure, linking the structure in as specified. Caller must hold |
431 | * call_rcu_mutex. | |
b57aee66 PM |
432 | */ |
433 | ||
3c24913f | 434 | static void call_rcu_data_init(struct call_rcu_data **crdpp, |
c1d2c60b MD |
435 | unsigned long flags, |
436 | int cpu_affinity) | |
b57aee66 PM |
437 | { |
438 | struct call_rcu_data *crdp; | |
4a6d7378 | 439 | int ret; |
ea3a28a3 | 440 | sigset_t newmask, oldmask; |
b57aee66 PM |
441 | |
442 | crdp = malloc(sizeof(*crdp)); | |
4a6d7378 MD |
443 | if (crdp == NULL) |
444 | urcu_die(errno); | |
b57aee66 | 445 | memset(crdp, '\0', sizeof(*crdp)); |
5161f31e | 446 | cds_wfcq_init(&crdp->cbs_head, &crdp->cbs_tail); |
b57aee66 | 447 | crdp->qlen = 0; |
263e3cf9 MD |
448 | crdp->futex = 0; |
449 | crdp->flags = flags; | |
3c24913f | 450 | cds_list_add(&crdp->list, &call_rcu_data_list); |
c1d2c60b | 451 | crdp->cpu_affinity = cpu_affinity; |
8e3690db | 452 | crdp->gp_count = 0; |
90f72b8c | 453 | rcu_set_pointer(crdpp, crdp); |
ea3a28a3 MD |
454 | |
455 | ret = sigfillset(&newmask); | |
456 | urcu_posix_assert(!ret); | |
457 | ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask); | |
458 | urcu_posix_assert(!ret); | |
459 | ||
4a6d7378 MD |
460 | ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp); |
461 | if (ret) | |
462 | urcu_die(ret); | |
ea3a28a3 MD |
463 | |
464 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
465 | urcu_posix_assert(!ret); | |
b57aee66 PM |
466 | } |
467 | ||
468 | /* | |
469 | * Return a pointer to the call_rcu_data structure for the specified | |
470 | * CPU, returning NULL if there is none. We cannot automatically | |
471 | * created it because the platform we are running on might not define | |
63b495d8 | 472 | * urcu_sched_getcpu(). |
618b2595 MD |
473 | * |
474 | * The call to this function and use of the returned call_rcu_data | |
475 | * should be protected by RCU read-side lock. | |
b57aee66 PM |
476 | */ |
477 | ||
478 | struct call_rcu_data *get_cpu_call_rcu_data(int cpu) | |
479 | { | |
480 | static int warned = 0; | |
618b2595 | 481 | struct call_rcu_data **pcpu_crdp; |
b57aee66 | 482 | |
618b2595 MD |
483 | pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data); |
484 | if (pcpu_crdp == NULL) | |
b57aee66 | 485 | return NULL; |
5cfe81b7 | 486 | if (!warned && cpus_array_len > 0 && (cpu < 0 || cpus_array_len <= cpu)) { |
b57aee66 PM |
487 | fprintf(stderr, "[error] liburcu: get CPU # out of range\n"); |
488 | warned = 1; | |
489 | } | |
5cfe81b7 | 490 | if (cpu < 0 || cpus_array_len <= cpu) |
b57aee66 | 491 | return NULL; |
618b2595 | 492 | return rcu_dereference(pcpu_crdp[cpu]); |
b57aee66 PM |
493 | } |
494 | ||
495 | /* | |
496 | * Return the tid corresponding to the call_rcu thread whose | |
497 | * call_rcu_data structure is specified. | |
498 | */ | |
499 | ||
500 | pthread_t get_call_rcu_thread(struct call_rcu_data *crdp) | |
501 | { | |
502 | return crdp->tid; | |
503 | } | |
504 | ||
505 | /* | |
506 | * Create a call_rcu_data structure (with thread) and return a pointer. | |
507 | */ | |
508 | ||
c1d2c60b MD |
509 | static struct call_rcu_data *__create_call_rcu_data(unsigned long flags, |
510 | int cpu_affinity) | |
b57aee66 PM |
511 | { |
512 | struct call_rcu_data *crdp; | |
513 | ||
c1d2c60b | 514 | call_rcu_data_init(&crdp, flags, cpu_affinity); |
b57aee66 PM |
515 | return crdp; |
516 | } | |
517 | ||
c1d2c60b MD |
518 | struct call_rcu_data *create_call_rcu_data(unsigned long flags, |
519 | int cpu_affinity) | |
3c24913f PM |
520 | { |
521 | struct call_rcu_data *crdp; | |
522 | ||
523 | call_rcu_lock(&call_rcu_mutex); | |
c1d2c60b | 524 | crdp = __create_call_rcu_data(flags, cpu_affinity); |
3c24913f PM |
525 | call_rcu_unlock(&call_rcu_mutex); |
526 | return crdp; | |
527 | } | |
528 | ||
b57aee66 PM |
529 | /* |
530 | * Set the specified CPU to use the specified call_rcu_data structure. | |
7106ddf8 PM |
531 | * |
532 | * Use NULL to remove a CPU's call_rcu_data structure, but it is | |
533 | * the caller's responsibility to dispose of the removed structure. | |
534 | * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure | |
535 | * (prior to NULLing it out, of course). | |
f9da0936 MD |
536 | * |
537 | * The caller must wait for a grace-period to pass between return from | |
538 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the | |
539 | * previous call rcu data as argument. | |
b57aee66 PM |
540 | */ |
541 | ||
542 | int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp) | |
543 | { | |
dcfc8165 | 544 | static int warned = 0; |
b57aee66 PM |
545 | |
546 | call_rcu_lock(&call_rcu_mutex); | |
f3776786 | 547 | alloc_cpu_call_rcu_data(); |
5cfe81b7 | 548 | if (cpu < 0 || cpus_array_len <= cpu) { |
b57aee66 PM |
549 | if (!warned) { |
550 | fprintf(stderr, "[error] liburcu: set CPU # out of range\n"); | |
551 | warned = 1; | |
552 | } | |
553 | call_rcu_unlock(&call_rcu_mutex); | |
554 | errno = EINVAL; | |
555 | return -EINVAL; | |
556 | } | |
53a55535 | 557 | |
b57aee66 | 558 | if (per_cpu_call_rcu_data == NULL) { |
3670fef2 | 559 | call_rcu_unlock(&call_rcu_mutex); |
b57aee66 PM |
560 | errno = ENOMEM; |
561 | return -ENOMEM; | |
562 | } | |
53a55535 LJ |
563 | |
564 | if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) { | |
565 | call_rcu_unlock(&call_rcu_mutex); | |
566 | errno = EEXIST; | |
567 | return -EEXIST; | |
568 | } | |
569 | ||
618b2595 | 570 | rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp); |
3670fef2 | 571 | call_rcu_unlock(&call_rcu_mutex); |
b57aee66 PM |
572 | return 0; |
573 | } | |
574 | ||
575 | /* | |
576 | * Return a pointer to the default call_rcu_data structure, creating | |
90f72b8c MD |
577 | * one if need be. |
578 | * | |
579 | * The call to this function with intent to use the returned | |
580 | * call_rcu_data should be protected by RCU read-side lock. | |
b57aee66 PM |
581 | */ |
582 | ||
583 | struct call_rcu_data *get_default_call_rcu_data(void) | |
584 | { | |
90f72b8c MD |
585 | struct call_rcu_data *crdp; |
586 | ||
587 | crdp = rcu_dereference(default_call_rcu_data); | |
588 | if (crdp != NULL) | |
589 | return crdp; | |
590 | ||
b57aee66 | 591 | call_rcu_lock(&call_rcu_mutex); |
90f72b8c MD |
592 | if (default_call_rcu_data == NULL) |
593 | call_rcu_data_init(&default_call_rcu_data, 0, -1); | |
594 | crdp = default_call_rcu_data; | |
b57aee66 | 595 | call_rcu_unlock(&call_rcu_mutex); |
90f72b8c MD |
596 | |
597 | return crdp; | |
b57aee66 PM |
598 | } |
599 | ||
600 | /* | |
601 | * Return the call_rcu_data structure that applies to the currently | |
602 | * running thread. Any call_rcu_data structure assigned specifically | |
603 | * to this thread has first priority, followed by any call_rcu_data | |
604 | * structure assigned to the CPU on which the thread is running, | |
605 | * followed by the default call_rcu_data structure. If there is not | |
606 | * yet a default call_rcu_data structure, one will be created. | |
618b2595 MD |
607 | * |
608 | * Calls to this function and use of the returned call_rcu_data should | |
609 | * be protected by RCU read-side lock. | |
b57aee66 PM |
610 | */ |
611 | struct call_rcu_data *get_call_rcu_data(void) | |
612 | { | |
9744f3bb | 613 | struct call_rcu_data *crd; |
b57aee66 | 614 | |
bd252a04 MD |
615 | if (URCU_TLS(thread_call_rcu_data) != NULL) |
616 | return URCU_TLS(thread_call_rcu_data); | |
9744f3bb | 617 | |
5cfe81b7 | 618 | if (cpus_array_len > 0) { |
63b495d8 | 619 | crd = get_cpu_call_rcu_data(urcu_sched_getcpu()); |
9744f3bb LJ |
620 | if (crd) |
621 | return crd; | |
b57aee66 | 622 | } |
9744f3bb | 623 | |
b57aee66 PM |
624 | return get_default_call_rcu_data(); |
625 | } | |
626 | ||
627 | /* | |
628 | * Return a pointer to this task's call_rcu_data if there is one. | |
629 | */ | |
630 | ||
631 | struct call_rcu_data *get_thread_call_rcu_data(void) | |
632 | { | |
bd252a04 | 633 | return URCU_TLS(thread_call_rcu_data); |
b57aee66 PM |
634 | } |
635 | ||
636 | /* | |
637 | * Set this task's call_rcu_data structure as specified, regardless | |
638 | * of whether or not this task already had one. (This allows switching | |
639 | * to and from real-time call_rcu threads, for example.) | |
7106ddf8 PM |
640 | * |
641 | * Use NULL to remove a thread's call_rcu_data structure, but it is | |
642 | * the caller's responsibility to dispose of the removed structure. | |
643 | * Use get_thread_call_rcu_data() to obtain a pointer to the old structure | |
644 | * (prior to NULLing it out, of course). | |
b57aee66 PM |
645 | */ |
646 | ||
647 | void set_thread_call_rcu_data(struct call_rcu_data *crdp) | |
648 | { | |
bd252a04 | 649 | URCU_TLS(thread_call_rcu_data) = crdp; |
b57aee66 PM |
650 | } |
651 | ||
652 | /* | |
653 | * Create a separate call_rcu thread for each CPU. This does not | |
654 | * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data() | |
0938c541 MD |
655 | * function if you want that behavior. Should be paired with |
656 | * free_all_cpu_call_rcu_data() to teardown these call_rcu worker | |
657 | * threads. | |
b57aee66 PM |
658 | */ |
659 | ||
660 | int create_all_cpu_call_rcu_data(unsigned long flags) | |
661 | { | |
662 | int i; | |
663 | struct call_rcu_data *crdp; | |
664 | int ret; | |
665 | ||
666 | call_rcu_lock(&call_rcu_mutex); | |
667 | alloc_cpu_call_rcu_data(); | |
668 | call_rcu_unlock(&call_rcu_mutex); | |
5cfe81b7 | 669 | if (cpus_array_len <= 0) { |
b57aee66 PM |
670 | errno = EINVAL; |
671 | return -EINVAL; | |
672 | } | |
673 | if (per_cpu_call_rcu_data == NULL) { | |
674 | errno = ENOMEM; | |
675 | return -ENOMEM; | |
676 | } | |
5cfe81b7 | 677 | for (i = 0; i < cpus_array_len; i++) { |
b57aee66 PM |
678 | call_rcu_lock(&call_rcu_mutex); |
679 | if (get_cpu_call_rcu_data(i)) { | |
680 | call_rcu_unlock(&call_rcu_mutex); | |
681 | continue; | |
682 | } | |
c1d2c60b | 683 | crdp = __create_call_rcu_data(flags, i); |
b57aee66 PM |
684 | if (crdp == NULL) { |
685 | call_rcu_unlock(&call_rcu_mutex); | |
686 | errno = ENOMEM; | |
687 | return -ENOMEM; | |
688 | } | |
689 | call_rcu_unlock(&call_rcu_mutex); | |
690 | if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) { | |
356c8794 LJ |
691 | call_rcu_data_free(crdp); |
692 | ||
693 | /* it has been created by other thread */ | |
694 | if (ret == -EEXIST) | |
695 | continue; | |
696 | ||
697 | return ret; | |
b57aee66 PM |
698 | } |
699 | } | |
700 | return 0; | |
701 | } | |
702 | ||
7106ddf8 PM |
703 | /* |
704 | * Wake up the call_rcu thread corresponding to the specified | |
705 | * call_rcu_data structure. | |
706 | */ | |
707 | static void wake_call_rcu_thread(struct call_rcu_data *crdp) | |
708 | { | |
263e3cf9 MD |
709 | if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) |
710 | call_rcu_wake_up(crdp); | |
7106ddf8 PM |
711 | } |
712 | ||
b7f721d9 MD |
713 | static void _call_rcu(struct rcu_head *head, |
714 | void (*func)(struct rcu_head *head), | |
715 | struct call_rcu_data *crdp) | |
716 | { | |
717 | cds_wfcq_node_init(&head->next); | |
718 | head->func = func; | |
719 | cds_wfcq_enqueue(&crdp->cbs_head, &crdp->cbs_tail, &head->next); | |
720 | uatomic_inc(&crdp->qlen); | |
721 | wake_call_rcu_thread(crdp); | |
722 | } | |
723 | ||
b57aee66 PM |
724 | /* |
725 | * Schedule a function to be invoked after a following grace period. | |
726 | * This is the only function that must be called -- the others are | |
727 | * only present to allow applications to tune their use of RCU for | |
728 | * maximum performance. | |
729 | * | |
730 | * Note that unless a call_rcu thread has not already been created, | |
731 | * the first invocation of call_rcu() will create one. So, if you | |
732 | * need the first invocation of call_rcu() to be fast, make sure | |
733 | * to create a call_rcu thread first. One way to accomplish this is | |
734 | * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data(). | |
618b2595 MD |
735 | * |
736 | * call_rcu must be called by registered RCU read-side threads. | |
b57aee66 | 737 | */ |
b57aee66 PM |
738 | void call_rcu(struct rcu_head *head, |
739 | void (*func)(struct rcu_head *head)) | |
740 | { | |
741 | struct call_rcu_data *crdp; | |
742 | ||
618b2595 | 743 | /* Holding rcu read-side lock across use of per-cpu crdp */ |
ffb4aaa7 | 744 | _rcu_read_lock(); |
b57aee66 | 745 | crdp = get_call_rcu_data(); |
b7f721d9 | 746 | _call_rcu(head, func, crdp); |
ffb4aaa7 | 747 | _rcu_read_unlock(); |
7106ddf8 PM |
748 | } |
749 | ||
750 | /* | |
751 | * Free up the specified call_rcu_data structure, terminating the | |
752 | * associated call_rcu thread. The caller must have previously | |
753 | * removed the call_rcu_data structure from per-thread or per-CPU | |
754 | * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU | |
755 | * call_rcu_data structures or set_thread_call_rcu_data(NULL) for | |
756 | * per-thread call_rcu_data structures. | |
757 | * | |
758 | * We silently refuse to free up the default call_rcu_data structure | |
759 | * because that is where we put any leftover callbacks. Note that | |
760 | * the possibility of self-spawning callbacks makes it impossible | |
761 | * to execute all the callbacks in finite time without putting any | |
762 | * newly spawned callbacks somewhere else. The "somewhere else" of | |
763 | * last resort is the default call_rcu_data structure. | |
764 | * | |
765 | * We also silently refuse to free NULL pointers. This simplifies | |
766 | * the calling code. | |
f9da0936 MD |
767 | * |
768 | * The caller must wait for a grace-period to pass between return from | |
769 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the | |
770 | * previous call rcu data as argument. | |
03e5118f MD |
771 | * |
772 | * Note: introducing __cds_wfcq_splice_blocking() in this function fixed | |
773 | * a list corruption bug in the 0.7.x series. The equivalent fix | |
774 | * appeared in 0.6.8 for the stable-0.6 branch. | |
7106ddf8 | 775 | */ |
1cf55ba4 MD |
776 | static |
777 | void _call_rcu_data_free(struct call_rcu_data *crdp, unsigned int flags) | |
7106ddf8 | 778 | { |
7106ddf8 PM |
779 | if (crdp == NULL || crdp == default_call_rcu_data) { |
780 | return; | |
781 | } | |
2870aa1e PB |
782 | if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) { |
783 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP); | |
7106ddf8 | 784 | wake_call_rcu_thread(crdp); |
2870aa1e | 785 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) |
109105b7 | 786 | (void) poll(NULL, 0, 1); |
7106ddf8 | 787 | } |
51b98c3c | 788 | call_rcu_lock(&call_rcu_mutex); |
5161f31e | 789 | if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) { |
51b98c3c PM |
790 | call_rcu_unlock(&call_rcu_mutex); |
791 | /* Create default call rcu data if need be. */ | |
792 | /* CBs queued here will be handed to the default list. */ | |
698d0778 | 793 | (void) get_default_call_rcu_data(); |
51b98c3c | 794 | call_rcu_lock(&call_rcu_mutex); |
5161f31e MD |
795 | __cds_wfcq_splice_blocking(&default_call_rcu_data->cbs_head, |
796 | &default_call_rcu_data->cbs_tail, | |
797 | &crdp->cbs_head, &crdp->cbs_tail); | |
7106ddf8 PM |
798 | uatomic_add(&default_call_rcu_data->qlen, |
799 | uatomic_read(&crdp->qlen)); | |
1e92aa15 | 800 | wake_call_rcu_thread(default_call_rcu_data); |
7106ddf8 | 801 | } |
59dc9e9d LJ |
802 | |
803 | cds_list_del(&crdp->list); | |
b75dffe6 LJ |
804 | call_rcu_unlock(&call_rcu_mutex); |
805 | ||
1cf55ba4 MD |
806 | if (flags & CRDF_FLAG_JOIN_THREAD) { |
807 | int ret; | |
808 | ||
809 | ret = pthread_join(get_call_rcu_thread(crdp), NULL); | |
810 | if (ret) | |
811 | urcu_die(ret); | |
812 | } | |
59dc9e9d | 813 | free(crdp); |
7106ddf8 PM |
814 | } |
815 | ||
1cf55ba4 MD |
816 | void call_rcu_data_free(struct call_rcu_data *crdp) |
817 | { | |
818 | _call_rcu_data_free(crdp, CRDF_FLAG_JOIN_THREAD); | |
819 | } | |
820 | ||
7106ddf8 PM |
821 | /* |
822 | * Clean up all the per-CPU call_rcu threads. | |
823 | */ | |
824 | void free_all_cpu_call_rcu_data(void) | |
825 | { | |
826 | int cpu; | |
618b2595 MD |
827 | struct call_rcu_data **crdp; |
828 | static int warned = 0; | |
7106ddf8 | 829 | |
5cfe81b7 | 830 | if (cpus_array_len <= 0) |
7106ddf8 | 831 | return; |
618b2595 | 832 | |
5cfe81b7 | 833 | crdp = malloc(sizeof(*crdp) * cpus_array_len); |
618b2595 MD |
834 | if (!crdp) { |
835 | if (!warned) { | |
836 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); | |
837 | } | |
838 | warned = 1; | |
d31150b4 | 839 | return; |
618b2595 MD |
840 | } |
841 | ||
5cfe81b7 | 842 | for (cpu = 0; cpu < cpus_array_len; cpu++) { |
618b2595 MD |
843 | crdp[cpu] = get_cpu_call_rcu_data(cpu); |
844 | if (crdp[cpu] == NULL) | |
7106ddf8 PM |
845 | continue; |
846 | set_cpu_call_rcu_data(cpu, NULL); | |
7106ddf8 | 847 | } |
618b2595 MD |
848 | /* |
849 | * Wait for call_rcu sites acting as RCU readers of the | |
850 | * call_rcu_data to become quiescent. | |
851 | */ | |
852 | synchronize_rcu(); | |
5cfe81b7 | 853 | for (cpu = 0; cpu < cpus_array_len; cpu++) { |
618b2595 MD |
854 | if (crdp[cpu] == NULL) |
855 | continue; | |
856 | call_rcu_data_free(crdp[cpu]); | |
857 | } | |
858 | free(crdp); | |
7106ddf8 PM |
859 | } |
860 | ||
81dd9134 KF |
861 | static |
862 | void free_completion(struct urcu_ref *ref) | |
863 | { | |
864 | struct call_rcu_completion *completion; | |
865 | ||
866 | completion = caa_container_of(ref, struct call_rcu_completion, ref); | |
867 | free(completion); | |
868 | } | |
869 | ||
b7f721d9 MD |
870 | static |
871 | void _rcu_barrier_complete(struct rcu_head *head) | |
872 | { | |
873 | struct call_rcu_completion_work *work; | |
874 | struct call_rcu_completion *completion; | |
875 | ||
876 | work = caa_container_of(head, struct call_rcu_completion_work, head); | |
877 | completion = work->completion; | |
81dd9134 KF |
878 | if (!uatomic_sub_return(&completion->barrier_count, 1)) |
879 | call_rcu_completion_wake_up(completion); | |
880 | urcu_ref_put(&completion->ref, free_completion); | |
b7f721d9 MD |
881 | free(work); |
882 | } | |
883 | ||
884 | /* | |
885 | * Wait for all in-flight call_rcu callbacks to complete execution. | |
886 | */ | |
887 | void rcu_barrier(void) | |
888 | { | |
889 | struct call_rcu_data *crdp; | |
81dd9134 | 890 | struct call_rcu_completion *completion; |
63f0fc6d | 891 | int count = 0; |
b7f721d9 MD |
892 | int was_online; |
893 | ||
894 | /* Put in offline state in QSBR. */ | |
ffb4aaa7 | 895 | was_online = _rcu_read_ongoing(); |
b7f721d9 MD |
896 | if (was_online) |
897 | rcu_thread_offline(); | |
898 | /* | |
899 | * Calling a rcu_barrier() within a RCU read-side critical | |
900 | * section is an error. | |
901 | */ | |
ffb4aaa7 | 902 | if (_rcu_read_ongoing()) { |
b7f721d9 MD |
903 | static int warned = 0; |
904 | ||
905 | if (!warned) { | |
906 | fprintf(stderr, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n"); | |
907 | } | |
908 | warned = 1; | |
909 | goto online; | |
910 | } | |
911 | ||
81dd9134 KF |
912 | completion = calloc(sizeof(*completion), 1); |
913 | if (!completion) | |
914 | urcu_die(errno); | |
915 | ||
b7f721d9 MD |
916 | call_rcu_lock(&call_rcu_mutex); |
917 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) | |
918 | count++; | |
919 | ||
81dd9134 KF |
920 | /* Referenced by rcu_barrier() and each call_rcu thread. */ |
921 | urcu_ref_set(&completion->ref, count + 1); | |
922 | completion->barrier_count = count; | |
b7f721d9 MD |
923 | |
924 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { | |
925 | struct call_rcu_completion_work *work; | |
926 | ||
927 | work = calloc(sizeof(*work), 1); | |
63f0fc6d MD |
928 | if (!work) |
929 | urcu_die(errno); | |
81dd9134 | 930 | work->completion = completion; |
b7f721d9 | 931 | _call_rcu(&work->head, _rcu_barrier_complete, crdp); |
b7f721d9 MD |
932 | } |
933 | call_rcu_unlock(&call_rcu_mutex); | |
934 | ||
b7f721d9 MD |
935 | /* Wait for them */ |
936 | for (;;) { | |
81dd9134 | 937 | uatomic_dec(&completion->futex); |
b7f721d9 MD |
938 | /* Decrement futex before reading barrier_count */ |
939 | cmm_smp_mb(); | |
81dd9134 | 940 | if (!uatomic_read(&completion->barrier_count)) |
b7f721d9 | 941 | break; |
81dd9134 | 942 | call_rcu_completion_wait(completion); |
b7f721d9 | 943 | } |
81dd9134 KF |
944 | |
945 | urcu_ref_put(&completion->ref, free_completion); | |
946 | ||
b7f721d9 MD |
947 | online: |
948 | if (was_online) | |
949 | rcu_thread_online(); | |
950 | } | |
951 | ||
81ad2e19 PM |
952 | /* |
953 | * Acquire the call_rcu_mutex in order to ensure that the child sees | |
e85451a1 MD |
954 | * all of the call_rcu() data structures in a consistent state. Ensure |
955 | * that all call_rcu threads are in a quiescent state across fork. | |
81ad2e19 PM |
956 | * Suitable for pthread_atfork() and friends. |
957 | */ | |
958 | void call_rcu_before_fork(void) | |
959 | { | |
e85451a1 | 960 | struct call_rcu_data *crdp; |
d0ec0ed2 | 961 | struct urcu_atfork *atfork; |
e85451a1 | 962 | |
81ad2e19 | 963 | call_rcu_lock(&call_rcu_mutex); |
e85451a1 | 964 | |
d0ec0ed2 MD |
965 | atfork = registered_rculfhash_atfork; |
966 | if (atfork) | |
967 | atfork->before_fork(atfork->priv); | |
968 | ||
e85451a1 MD |
969 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { |
970 | uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSE); | |
971 | cmm_smp_mb__after_uatomic_or(); | |
972 | wake_call_rcu_thread(crdp); | |
973 | } | |
974 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { | |
975 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0) | |
109105b7 | 976 | (void) poll(NULL, 0, 1); |
e85451a1 | 977 | } |
81ad2e19 PM |
978 | } |
979 | ||
980 | /* | |
981 | * Clean up call_rcu data structures in the parent of a successful fork() | |
982 | * that is not followed by exec() in the child. Suitable for | |
983 | * pthread_atfork() and friends. | |
984 | */ | |
985 | void call_rcu_after_fork_parent(void) | |
986 | { | |
e85451a1 | 987 | struct call_rcu_data *crdp; |
d0ec0ed2 | 988 | struct urcu_atfork *atfork; |
e85451a1 MD |
989 | |
990 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) | |
991 | uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE); | |
fc236e5e KF |
992 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { |
993 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) != 0) | |
109105b7 | 994 | (void) poll(NULL, 0, 1); |
fc236e5e | 995 | } |
d0ec0ed2 MD |
996 | atfork = registered_rculfhash_atfork; |
997 | if (atfork) | |
998 | atfork->after_fork_parent(atfork->priv); | |
81ad2e19 PM |
999 | call_rcu_unlock(&call_rcu_mutex); |
1000 | } | |
1001 | ||
7106ddf8 PM |
1002 | /* |
1003 | * Clean up call_rcu data structures in the child of a successful fork() | |
81ad2e19 PM |
1004 | * that is not followed by exec(). Suitable for pthread_atfork() and |
1005 | * friends. | |
7106ddf8 PM |
1006 | */ |
1007 | void call_rcu_after_fork_child(void) | |
1008 | { | |
077ff173 | 1009 | struct call_rcu_data *crdp, *next; |
d0ec0ed2 | 1010 | struct urcu_atfork *atfork; |
7106ddf8 | 1011 | |
81ad2e19 PM |
1012 | /* Release the mutex. */ |
1013 | call_rcu_unlock(&call_rcu_mutex); | |
1014 | ||
d0ec0ed2 MD |
1015 | atfork = registered_rculfhash_atfork; |
1016 | if (atfork) | |
1017 | atfork->after_fork_child(atfork->priv); | |
1018 | ||
ad1b9909 LJ |
1019 | /* Do nothing when call_rcu() has not been used */ |
1020 | if (cds_list_empty(&call_rcu_data_list)) | |
1021 | return; | |
1022 | ||
7106ddf8 PM |
1023 | /* |
1024 | * Allocate a new default call_rcu_data structure in order | |
1025 | * to get a working call_rcu thread to go with it. | |
1026 | */ | |
1027 | default_call_rcu_data = NULL; | |
1028 | (void)get_default_call_rcu_data(); | |
1029 | ||
60af049d | 1030 | /* Cleanup call_rcu_data pointers before use */ |
5cfe81b7 | 1031 | cpus_array_len_reset(); |
60af049d | 1032 | free(per_cpu_call_rcu_data); |
618b2595 | 1033 | rcu_set_pointer(&per_cpu_call_rcu_data, NULL); |
bd252a04 | 1034 | URCU_TLS(thread_call_rcu_data) = NULL; |
60af049d | 1035 | |
e85451a1 MD |
1036 | /* |
1037 | * Dispose of all of the rest of the call_rcu_data structures. | |
1038 | * Leftover call_rcu callbacks will be merged into the new | |
1039 | * default call_rcu thread queue. | |
1040 | */ | |
077ff173 | 1041 | cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) { |
7106ddf8 | 1042 | if (crdp == default_call_rcu_data) |
077ff173 | 1043 | continue; |
2870aa1e | 1044 | uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED); |
1cf55ba4 MD |
1045 | /* |
1046 | * Do not join the thread because it does not exist in | |
1047 | * the child. | |
1048 | */ | |
1049 | _call_rcu_data_free(crdp, 0); | |
b57aee66 PM |
1050 | } |
1051 | } | |
d0ec0ed2 MD |
1052 | |
1053 | void urcu_register_rculfhash_atfork(struct urcu_atfork *atfork) | |
1054 | { | |
b047e7a7 MD |
1055 | if (CMM_LOAD_SHARED(registered_rculfhash_atfork)) |
1056 | return; | |
d0ec0ed2 | 1057 | call_rcu_lock(&call_rcu_mutex); |
b047e7a7 MD |
1058 | if (!registered_rculfhash_atfork) |
1059 | registered_rculfhash_atfork = atfork; | |
d0ec0ed2 MD |
1060 | call_rcu_unlock(&call_rcu_mutex); |
1061 | } | |
1062 | ||
b047e7a7 MD |
1063 | /* |
1064 | * This unregistration function is deprecated, meant only for internal | |
1065 | * use by rculfhash. | |
1066 | */ | |
1067 | __attribute__((noreturn)) | |
70469b43 | 1068 | void urcu_unregister_rculfhash_atfork(struct urcu_atfork *atfork __attribute__((unused))) |
d0ec0ed2 | 1069 | { |
b047e7a7 | 1070 | urcu_die(EPERM); |
d0ec0ed2 | 1071 | } |
90f72b8c MD |
1072 | |
1073 | /* | |
1074 | * Teardown the default call_rcu worker thread if there are no queued | |
1075 | * callbacks on process exit. This prevents leaking memory. | |
1076 | * | |
1077 | * Here is how an application can ensure graceful teardown of this | |
1078 | * worker thread: | |
1079 | * | |
1080 | * - An application queuing call_rcu callbacks should invoke | |
1081 | * rcu_barrier() before it exits. | |
1082 | * - When chaining call_rcu callbacks, the number of calls to | |
1083 | * rcu_barrier() on application exit must match at least the maximum | |
1084 | * number of chained callbacks. | |
1085 | * - If an application chains callbacks endlessly, it would have to be | |
1086 | * modified to stop chaining callbacks when it detects an application | |
1087 | * exit (e.g. with a flag), and wait for quiescence with rcu_barrier() | |
1088 | * after setting that flag. | |
1089 | * - The statements above apply to a library which queues call_rcu | |
1090 | * callbacks, only it needs to invoke rcu_barrier in its library | |
1091 | * destructor. | |
1092 | * | |
1093 | * Note that this function does not presume it is being called when the | |
1094 | * application is single-threaded even though this is invoked from a | |
1095 | * destructor: this function synchronizes against concurrent calls to | |
1096 | * get_default_call_rcu_data(). | |
1097 | */ | |
1098 | static void urcu_call_rcu_exit(void) | |
1099 | { | |
1100 | struct call_rcu_data *crdp; | |
1101 | bool teardown = true; | |
1102 | ||
1103 | if (default_call_rcu_data == NULL) | |
1104 | return; | |
1105 | call_rcu_lock(&call_rcu_mutex); | |
1106 | /* | |
1107 | * If the application leaves callbacks in the default call_rcu | |
1108 | * worker queue, keep the default worker in place. | |
1109 | */ | |
1110 | crdp = default_call_rcu_data; | |
1111 | if (!crdp) { | |
1112 | teardown = false; | |
1113 | goto unlock; | |
1114 | } | |
1115 | if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) { | |
1116 | teardown = false; | |
1117 | goto unlock; | |
1118 | } | |
1119 | rcu_set_pointer(&default_call_rcu_data, NULL); | |
1120 | unlock: | |
1121 | call_rcu_unlock(&call_rcu_mutex); | |
1122 | if (teardown) { | |
1123 | synchronize_rcu(); | |
1124 | call_rcu_data_free(crdp); | |
1125 | } | |
1126 | } |