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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 | ||
c1d2c60b | 23 | #define _GNU_SOURCE |
b57aee66 PM |
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> |
b57aee66 PM |
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 PM |
36 | |
37 | #include "config.h" | |
38 | #include "urcu/wfqueue.h" | |
39 | #include "urcu-call-rcu.h" | |
40 | #include "urcu-pointer.h" | |
3c24913f | 41 | #include "urcu/list.h" |
41849996 | 42 | #include "urcu/futex.h" |
b57aee66 PM |
43 | |
44 | /* Data structure that identifies a call_rcu thread. */ | |
45 | ||
46 | struct call_rcu_data { | |
47 | struct cds_wfq_queue cbs; | |
48 | unsigned long flags; | |
6d841bc2 | 49 | int32_t futex; |
73987721 | 50 | unsigned long qlen; /* maintained for debugging. */ |
b57aee66 | 51 | pthread_t tid; |
c1d2c60b | 52 | int cpu_affinity; |
3c24913f | 53 | struct cds_list_head list; |
b57aee66 PM |
54 | } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
55 | ||
3c24913f PM |
56 | /* |
57 | * List of all call_rcu_data structures to keep valgrind happy. | |
58 | * Protected by call_rcu_mutex. | |
59 | */ | |
60 | ||
61 | CDS_LIST_HEAD(call_rcu_data_list); | |
62 | ||
b57aee66 PM |
63 | /* Link a thread using call_rcu() to its call_rcu thread. */ |
64 | ||
65 | static __thread struct call_rcu_data *thread_call_rcu_data; | |
66 | ||
483c853e MD |
67 | /* |
68 | * Guard call_rcu thread creation and atfork handlers. | |
69 | */ | |
b57aee66 PM |
70 | static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER; |
71 | ||
72 | /* If a given thread does not have its own call_rcu thread, this is default. */ | |
73 | ||
74 | static struct call_rcu_data *default_call_rcu_data; | |
75 | ||
b57aee66 PM |
76 | /* |
77 | * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are | |
78 | * available, then we can have call_rcu threads assigned to individual | |
79 | * CPUs rather than only to specific threads. | |
80 | */ | |
81 | ||
82 | #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) | |
83 | ||
84 | /* | |
85 | * Pointer to array of pointers to per-CPU call_rcu_data structures | |
618b2595 MD |
86 | * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an |
87 | * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a | |
88 | * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer | |
89 | * without mutex. The call_rcu_mutex protects updates. | |
b57aee66 PM |
90 | */ |
91 | ||
92 | static struct call_rcu_data **per_cpu_call_rcu_data; | |
93 | static long maxcpus; | |
94 | ||
60af049d LJ |
95 | static void maxcpus_reset(void) |
96 | { | |
97 | maxcpus = 0; | |
98 | } | |
99 | ||
b57aee66 PM |
100 | /* Allocate the array if it has not already been allocated. */ |
101 | ||
102 | static void alloc_cpu_call_rcu_data(void) | |
103 | { | |
104 | struct call_rcu_data **p; | |
105 | static int warned = 0; | |
106 | ||
107 | if (maxcpus != 0) | |
108 | return; | |
109 | maxcpus = sysconf(_SC_NPROCESSORS_CONF); | |
110 | if (maxcpus <= 0) { | |
111 | return; | |
112 | } | |
113 | p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data)); | |
114 | if (p != NULL) { | |
115 | memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data)); | |
618b2595 | 116 | rcu_set_pointer(&per_cpu_call_rcu_data, p); |
b57aee66 PM |
117 | } else { |
118 | if (!warned) { | |
119 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); | |
120 | } | |
121 | warned = 1; | |
122 | } | |
123 | } | |
124 | ||
125 | #else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ | |
126 | ||
f9437098 MD |
127 | /* |
128 | * per_cpu_call_rcu_data should be constant, but some functions below, used both | |
129 | * for cases where cpu number is available and not available, assume it it not | |
130 | * constant. | |
131 | */ | |
132 | static struct call_rcu_data **per_cpu_call_rcu_data = NULL; | |
b57aee66 PM |
133 | static const long maxcpus = -1; |
134 | ||
60af049d LJ |
135 | static void maxcpus_reset(void) |
136 | { | |
137 | } | |
138 | ||
b57aee66 PM |
139 | static void alloc_cpu_call_rcu_data(void) |
140 | { | |
141 | } | |
142 | ||
143 | static int sched_getcpu(void) | |
144 | { | |
145 | return -1; | |
146 | } | |
147 | ||
148 | #endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ | |
149 | ||
150 | /* Acquire the specified pthread mutex. */ | |
151 | ||
152 | static void call_rcu_lock(pthread_mutex_t *pmp) | |
153 | { | |
154 | if (pthread_mutex_lock(pmp) != 0) { | |
155 | perror("pthread_mutex_lock"); | |
156 | exit(-1); | |
157 | } | |
158 | } | |
159 | ||
160 | /* Release the specified pthread mutex. */ | |
161 | ||
162 | static void call_rcu_unlock(pthread_mutex_t *pmp) | |
163 | { | |
164 | if (pthread_mutex_unlock(pmp) != 0) { | |
165 | perror("pthread_mutex_unlock"); | |
166 | exit(-1); | |
167 | } | |
168 | } | |
169 | ||
c1d2c60b MD |
170 | #if HAVE_SCHED_SETAFFINITY |
171 | static | |
172 | int set_thread_cpu_affinity(struct call_rcu_data *crdp) | |
173 | { | |
174 | cpu_set_t mask; | |
175 | ||
176 | if (crdp->cpu_affinity < 0) | |
177 | return 0; | |
178 | ||
179 | CPU_ZERO(&mask); | |
180 | CPU_SET(crdp->cpu_affinity, &mask); | |
181 | #if SCHED_SETAFFINITY_ARGS == 2 | |
182 | return sched_setaffinity(0, &mask); | |
183 | #else | |
184 | return sched_setaffinity(0, sizeof(mask), &mask); | |
185 | #endif | |
186 | } | |
187 | #else | |
188 | static | |
189 | int set_thread_cpu_affinity(struct call_rcu_data *crdp) | |
190 | { | |
191 | return 0; | |
192 | } | |
193 | #endif | |
194 | ||
03fe58b3 MD |
195 | static void call_rcu_wait(struct call_rcu_data *crdp) |
196 | { | |
197 | /* Read call_rcu list before read futex */ | |
198 | cmm_smp_mb(); | |
199 | if (uatomic_read(&crdp->futex) == -1) | |
200 | futex_async(&crdp->futex, FUTEX_WAIT, -1, | |
201 | NULL, NULL, 0); | |
202 | } | |
203 | ||
204 | static void call_rcu_wake_up(struct call_rcu_data *crdp) | |
205 | { | |
206 | /* Write to call_rcu list before reading/writing futex */ | |
207 | cmm_smp_mb(); | |
a0b7f7ea | 208 | if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) { |
03fe58b3 MD |
209 | uatomic_set(&crdp->futex, 0); |
210 | futex_async(&crdp->futex, FUTEX_WAKE, 1, | |
211 | NULL, NULL, 0); | |
212 | } | |
213 | } | |
214 | ||
b57aee66 PM |
215 | /* This is the code run by each call_rcu thread. */ |
216 | ||
217 | static void *call_rcu_thread(void *arg) | |
218 | { | |
219 | unsigned long cbcount; | |
220 | struct cds_wfq_node *cbs; | |
221 | struct cds_wfq_node **cbs_tail; | |
222 | struct call_rcu_data *crdp = (struct call_rcu_data *)arg; | |
223 | struct rcu_head *rhp; | |
2870aa1e | 224 | int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT); |
b57aee66 | 225 | |
c1d2c60b MD |
226 | if (set_thread_cpu_affinity(crdp) != 0) { |
227 | perror("pthread_setaffinity_np"); | |
228 | exit(-1); | |
229 | } | |
230 | ||
765f3ead MD |
231 | /* |
232 | * If callbacks take a read-side lock, we need to be registered. | |
233 | */ | |
234 | rcu_register_thread(); | |
235 | ||
b57aee66 | 236 | thread_call_rcu_data = crdp; |
bc94ca9b MD |
237 | if (!rt) { |
238 | uatomic_dec(&crdp->futex); | |
239 | /* Decrement futex before reading call_rcu list */ | |
240 | cmm_smp_mb(); | |
241 | } | |
b57aee66 | 242 | for (;;) { |
483c853e MD |
243 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) { |
244 | /* | |
245 | * Pause requested. Become quiescent: remove | |
246 | * ourself from all global lists, and don't | |
247 | * process any callback. The callback lists may | |
248 | * still be non-empty though. | |
249 | */ | |
250 | rcu_unregister_thread(); | |
251 | cmm_smp_mb__before_uatomic_or(); | |
252 | uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED); | |
253 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0) | |
254 | poll(NULL, 0, 1); | |
255 | rcu_register_thread(); | |
256 | } | |
257 | ||
b57aee66 PM |
258 | if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) { |
259 | while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL) | |
260 | poll(NULL, 0, 1); | |
261 | _CMM_STORE_SHARED(crdp->cbs.head, NULL); | |
262 | cbs_tail = (struct cds_wfq_node **) | |
263 | uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head); | |
264 | synchronize_rcu(); | |
265 | cbcount = 0; | |
266 | do { | |
267 | while (cbs->next == NULL && | |
268 | &cbs->next != cbs_tail) | |
269 | poll(NULL, 0, 1); | |
270 | if (cbs == &crdp->cbs.dummy) { | |
271 | cbs = cbs->next; | |
272 | continue; | |
273 | } | |
274 | rhp = (struct rcu_head *)cbs; | |
275 | cbs = cbs->next; | |
276 | rhp->func(rhp); | |
277 | cbcount++; | |
278 | } while (cbs != NULL); | |
279 | uatomic_sub(&crdp->qlen, cbcount); | |
280 | } | |
bc94ca9b MD |
281 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP) |
282 | break; | |
765f3ead | 283 | rcu_thread_offline(); |
bc94ca9b MD |
284 | if (!rt) { |
285 | if (&crdp->cbs.head | |
286 | == _CMM_LOAD_SHARED(crdp->cbs.tail)) { | |
287 | call_rcu_wait(crdp); | |
288 | poll(NULL, 0, 10); | |
289 | uatomic_dec(&crdp->futex); | |
c768e45e | 290 | /* |
bc94ca9b MD |
291 | * Decrement futex before reading |
292 | * call_rcu list. | |
c768e45e MD |
293 | */ |
294 | cmm_smp_mb(); | |
ccbac24d MD |
295 | } else { |
296 | poll(NULL, 0, 10); | |
c768e45e | 297 | } |
bc94ca9b MD |
298 | } else { |
299 | poll(NULL, 0, 10); | |
b57aee66 | 300 | } |
765f3ead | 301 | rcu_thread_online(); |
bc94ca9b MD |
302 | } |
303 | if (!rt) { | |
304 | /* | |
305 | * Read call_rcu list before write futex. | |
306 | */ | |
307 | cmm_smp_mb(); | |
308 | uatomic_set(&crdp->futex, 0); | |
b57aee66 | 309 | } |
2870aa1e | 310 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED); |
765f3ead | 311 | rcu_unregister_thread(); |
7106ddf8 | 312 | return NULL; |
b57aee66 PM |
313 | } |
314 | ||
315 | /* | |
316 | * Create both a call_rcu thread and the corresponding call_rcu_data | |
3c24913f PM |
317 | * structure, linking the structure in as specified. Caller must hold |
318 | * call_rcu_mutex. | |
b57aee66 PM |
319 | */ |
320 | ||
3c24913f | 321 | static void call_rcu_data_init(struct call_rcu_data **crdpp, |
c1d2c60b MD |
322 | unsigned long flags, |
323 | int cpu_affinity) | |
b57aee66 PM |
324 | { |
325 | struct call_rcu_data *crdp; | |
326 | ||
327 | crdp = malloc(sizeof(*crdp)); | |
328 | if (crdp == NULL) { | |
329 | fprintf(stderr, "Out of memory.\n"); | |
330 | exit(-1); | |
331 | } | |
332 | memset(crdp, '\0', sizeof(*crdp)); | |
333 | cds_wfq_init(&crdp->cbs); | |
334 | crdp->qlen = 0; | |
263e3cf9 MD |
335 | crdp->futex = 0; |
336 | crdp->flags = flags; | |
3c24913f | 337 | cds_list_add(&crdp->list, &call_rcu_data_list); |
c1d2c60b | 338 | crdp->cpu_affinity = cpu_affinity; |
b57aee66 PM |
339 | cmm_smp_mb(); /* Structure initialized before pointer is planted. */ |
340 | *crdpp = crdp; | |
341 | if (pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp) != 0) { | |
342 | perror("pthread_create"); | |
343 | exit(-1); | |
344 | } | |
345 | } | |
346 | ||
347 | /* | |
348 | * Return a pointer to the call_rcu_data structure for the specified | |
349 | * CPU, returning NULL if there is none. We cannot automatically | |
350 | * created it because the platform we are running on might not define | |
351 | * sched_getcpu(). | |
618b2595 MD |
352 | * |
353 | * The call to this function and use of the returned call_rcu_data | |
354 | * should be protected by RCU read-side lock. | |
b57aee66 PM |
355 | */ |
356 | ||
357 | struct call_rcu_data *get_cpu_call_rcu_data(int cpu) | |
358 | { | |
359 | static int warned = 0; | |
618b2595 | 360 | struct call_rcu_data **pcpu_crdp; |
b57aee66 | 361 | |
618b2595 MD |
362 | pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data); |
363 | if (pcpu_crdp == NULL) | |
b57aee66 PM |
364 | return NULL; |
365 | if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) { | |
366 | fprintf(stderr, "[error] liburcu: get CPU # out of range\n"); | |
367 | warned = 1; | |
368 | } | |
369 | if (cpu < 0 || maxcpus <= cpu) | |
370 | return NULL; | |
618b2595 | 371 | return rcu_dereference(pcpu_crdp[cpu]); |
b57aee66 PM |
372 | } |
373 | ||
374 | /* | |
375 | * Return the tid corresponding to the call_rcu thread whose | |
376 | * call_rcu_data structure is specified. | |
377 | */ | |
378 | ||
379 | pthread_t get_call_rcu_thread(struct call_rcu_data *crdp) | |
380 | { | |
381 | return crdp->tid; | |
382 | } | |
383 | ||
384 | /* | |
385 | * Create a call_rcu_data structure (with thread) and return a pointer. | |
386 | */ | |
387 | ||
c1d2c60b MD |
388 | static struct call_rcu_data *__create_call_rcu_data(unsigned long flags, |
389 | int cpu_affinity) | |
b57aee66 PM |
390 | { |
391 | struct call_rcu_data *crdp; | |
392 | ||
c1d2c60b | 393 | call_rcu_data_init(&crdp, flags, cpu_affinity); |
b57aee66 PM |
394 | return crdp; |
395 | } | |
396 | ||
c1d2c60b MD |
397 | struct call_rcu_data *create_call_rcu_data(unsigned long flags, |
398 | int cpu_affinity) | |
3c24913f PM |
399 | { |
400 | struct call_rcu_data *crdp; | |
401 | ||
402 | call_rcu_lock(&call_rcu_mutex); | |
c1d2c60b | 403 | crdp = __create_call_rcu_data(flags, cpu_affinity); |
3c24913f PM |
404 | call_rcu_unlock(&call_rcu_mutex); |
405 | return crdp; | |
406 | } | |
407 | ||
b57aee66 PM |
408 | /* |
409 | * Set the specified CPU to use the specified call_rcu_data structure. | |
7106ddf8 PM |
410 | * |
411 | * Use NULL to remove a CPU's call_rcu_data structure, but it is | |
412 | * the caller's responsibility to dispose of the removed structure. | |
413 | * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure | |
414 | * (prior to NULLing it out, of course). | |
f9da0936 MD |
415 | * |
416 | * The caller must wait for a grace-period to pass between return from | |
417 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the | |
418 | * previous call rcu data as argument. | |
b57aee66 PM |
419 | */ |
420 | ||
421 | int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp) | |
422 | { | |
dcfc8165 | 423 | static int warned = 0; |
b57aee66 PM |
424 | |
425 | call_rcu_lock(&call_rcu_mutex); | |
f3776786 | 426 | alloc_cpu_call_rcu_data(); |
b57aee66 PM |
427 | if (cpu < 0 || maxcpus <= cpu) { |
428 | if (!warned) { | |
429 | fprintf(stderr, "[error] liburcu: set CPU # out of range\n"); | |
430 | warned = 1; | |
431 | } | |
432 | call_rcu_unlock(&call_rcu_mutex); | |
433 | errno = EINVAL; | |
434 | return -EINVAL; | |
435 | } | |
53a55535 | 436 | |
b57aee66 | 437 | if (per_cpu_call_rcu_data == NULL) { |
3670fef2 | 438 | call_rcu_unlock(&call_rcu_mutex); |
b57aee66 PM |
439 | errno = ENOMEM; |
440 | return -ENOMEM; | |
441 | } | |
53a55535 LJ |
442 | |
443 | if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) { | |
444 | call_rcu_unlock(&call_rcu_mutex); | |
445 | errno = EEXIST; | |
446 | return -EEXIST; | |
447 | } | |
448 | ||
618b2595 | 449 | rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp); |
3670fef2 | 450 | call_rcu_unlock(&call_rcu_mutex); |
b57aee66 PM |
451 | return 0; |
452 | } | |
453 | ||
454 | /* | |
455 | * Return a pointer to the default call_rcu_data structure, creating | |
456 | * one if need be. Because we never free call_rcu_data structures, | |
457 | * we don't need to be in an RCU read-side critical section. | |
458 | */ | |
459 | ||
460 | struct call_rcu_data *get_default_call_rcu_data(void) | |
461 | { | |
462 | if (default_call_rcu_data != NULL) | |
463 | return rcu_dereference(default_call_rcu_data); | |
464 | call_rcu_lock(&call_rcu_mutex); | |
465 | if (default_call_rcu_data != NULL) { | |
466 | call_rcu_unlock(&call_rcu_mutex); | |
467 | return default_call_rcu_data; | |
468 | } | |
c1d2c60b | 469 | call_rcu_data_init(&default_call_rcu_data, 0, -1); |
b57aee66 PM |
470 | call_rcu_unlock(&call_rcu_mutex); |
471 | return default_call_rcu_data; | |
472 | } | |
473 | ||
474 | /* | |
475 | * Return the call_rcu_data structure that applies to the currently | |
476 | * running thread. Any call_rcu_data structure assigned specifically | |
477 | * to this thread has first priority, followed by any call_rcu_data | |
478 | * structure assigned to the CPU on which the thread is running, | |
479 | * followed by the default call_rcu_data structure. If there is not | |
480 | * yet a default call_rcu_data structure, one will be created. | |
618b2595 MD |
481 | * |
482 | * Calls to this function and use of the returned call_rcu_data should | |
483 | * be protected by RCU read-side lock. | |
b57aee66 PM |
484 | */ |
485 | struct call_rcu_data *get_call_rcu_data(void) | |
486 | { | |
9744f3bb | 487 | struct call_rcu_data *crd; |
b57aee66 PM |
488 | |
489 | if (thread_call_rcu_data != NULL) | |
490 | return thread_call_rcu_data; | |
9744f3bb LJ |
491 | |
492 | if (maxcpus > 0) { | |
493 | crd = get_cpu_call_rcu_data(sched_getcpu()); | |
494 | if (crd) | |
495 | return crd; | |
b57aee66 | 496 | } |
9744f3bb | 497 | |
b57aee66 PM |
498 | return get_default_call_rcu_data(); |
499 | } | |
500 | ||
501 | /* | |
502 | * Return a pointer to this task's call_rcu_data if there is one. | |
503 | */ | |
504 | ||
505 | struct call_rcu_data *get_thread_call_rcu_data(void) | |
506 | { | |
507 | return thread_call_rcu_data; | |
508 | } | |
509 | ||
510 | /* | |
511 | * Set this task's call_rcu_data structure as specified, regardless | |
512 | * of whether or not this task already had one. (This allows switching | |
513 | * to and from real-time call_rcu threads, for example.) | |
7106ddf8 PM |
514 | * |
515 | * Use NULL to remove a thread's call_rcu_data structure, but it is | |
516 | * the caller's responsibility to dispose of the removed structure. | |
517 | * Use get_thread_call_rcu_data() to obtain a pointer to the old structure | |
518 | * (prior to NULLing it out, of course). | |
b57aee66 PM |
519 | */ |
520 | ||
521 | void set_thread_call_rcu_data(struct call_rcu_data *crdp) | |
522 | { | |
523 | thread_call_rcu_data = crdp; | |
524 | } | |
525 | ||
526 | /* | |
527 | * Create a separate call_rcu thread for each CPU. This does not | |
528 | * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data() | |
0938c541 MD |
529 | * function if you want that behavior. Should be paired with |
530 | * free_all_cpu_call_rcu_data() to teardown these call_rcu worker | |
531 | * threads. | |
b57aee66 PM |
532 | */ |
533 | ||
534 | int create_all_cpu_call_rcu_data(unsigned long flags) | |
535 | { | |
536 | int i; | |
537 | struct call_rcu_data *crdp; | |
538 | int ret; | |
539 | ||
540 | call_rcu_lock(&call_rcu_mutex); | |
541 | alloc_cpu_call_rcu_data(); | |
542 | call_rcu_unlock(&call_rcu_mutex); | |
543 | if (maxcpus <= 0) { | |
544 | errno = EINVAL; | |
545 | return -EINVAL; | |
546 | } | |
547 | if (per_cpu_call_rcu_data == NULL) { | |
548 | errno = ENOMEM; | |
549 | return -ENOMEM; | |
550 | } | |
551 | for (i = 0; i < maxcpus; i++) { | |
552 | call_rcu_lock(&call_rcu_mutex); | |
553 | if (get_cpu_call_rcu_data(i)) { | |
554 | call_rcu_unlock(&call_rcu_mutex); | |
555 | continue; | |
556 | } | |
c1d2c60b | 557 | crdp = __create_call_rcu_data(flags, i); |
b57aee66 PM |
558 | if (crdp == NULL) { |
559 | call_rcu_unlock(&call_rcu_mutex); | |
560 | errno = ENOMEM; | |
561 | return -ENOMEM; | |
562 | } | |
563 | call_rcu_unlock(&call_rcu_mutex); | |
564 | if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) { | |
356c8794 LJ |
565 | call_rcu_data_free(crdp); |
566 | ||
567 | /* it has been created by other thread */ | |
568 | if (ret == -EEXIST) | |
569 | continue; | |
570 | ||
571 | return ret; | |
b57aee66 PM |
572 | } |
573 | } | |
574 | return 0; | |
575 | } | |
576 | ||
7106ddf8 PM |
577 | /* |
578 | * Wake up the call_rcu thread corresponding to the specified | |
579 | * call_rcu_data structure. | |
580 | */ | |
581 | static void wake_call_rcu_thread(struct call_rcu_data *crdp) | |
582 | { | |
263e3cf9 MD |
583 | if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) |
584 | call_rcu_wake_up(crdp); | |
7106ddf8 PM |
585 | } |
586 | ||
b57aee66 PM |
587 | /* |
588 | * Schedule a function to be invoked after a following grace period. | |
589 | * This is the only function that must be called -- the others are | |
590 | * only present to allow applications to tune their use of RCU for | |
591 | * maximum performance. | |
592 | * | |
593 | * Note that unless a call_rcu thread has not already been created, | |
594 | * the first invocation of call_rcu() will create one. So, if you | |
595 | * need the first invocation of call_rcu() to be fast, make sure | |
596 | * to create a call_rcu thread first. One way to accomplish this is | |
597 | * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data(). | |
618b2595 MD |
598 | * |
599 | * call_rcu must be called by registered RCU read-side threads. | |
b57aee66 PM |
600 | */ |
601 | ||
602 | void call_rcu(struct rcu_head *head, | |
603 | void (*func)(struct rcu_head *head)) | |
604 | { | |
605 | struct call_rcu_data *crdp; | |
606 | ||
607 | cds_wfq_node_init(&head->next); | |
608 | head->func = func; | |
618b2595 MD |
609 | /* Holding rcu read-side lock across use of per-cpu crdp */ |
610 | rcu_read_lock(); | |
b57aee66 PM |
611 | crdp = get_call_rcu_data(); |
612 | cds_wfq_enqueue(&crdp->cbs, &head->next); | |
613 | uatomic_inc(&crdp->qlen); | |
7106ddf8 | 614 | wake_call_rcu_thread(crdp); |
618b2595 | 615 | rcu_read_unlock(); |
7106ddf8 PM |
616 | } |
617 | ||
618 | /* | |
619 | * Free up the specified call_rcu_data structure, terminating the | |
620 | * associated call_rcu thread. The caller must have previously | |
621 | * removed the call_rcu_data structure from per-thread or per-CPU | |
622 | * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU | |
623 | * call_rcu_data structures or set_thread_call_rcu_data(NULL) for | |
624 | * per-thread call_rcu_data structures. | |
625 | * | |
626 | * We silently refuse to free up the default call_rcu_data structure | |
627 | * because that is where we put any leftover callbacks. Note that | |
628 | * the possibility of self-spawning callbacks makes it impossible | |
629 | * to execute all the callbacks in finite time without putting any | |
630 | * newly spawned callbacks somewhere else. The "somewhere else" of | |
631 | * last resort is the default call_rcu_data structure. | |
632 | * | |
633 | * We also silently refuse to free NULL pointers. This simplifies | |
634 | * the calling code. | |
f9da0936 MD |
635 | * |
636 | * The caller must wait for a grace-period to pass between return from | |
637 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the | |
638 | * previous call rcu data as argument. | |
7106ddf8 PM |
639 | */ |
640 | void call_rcu_data_free(struct call_rcu_data *crdp) | |
641 | { | |
642 | struct cds_wfq_node *cbs; | |
643 | struct cds_wfq_node **cbs_tail; | |
644 | struct cds_wfq_node **cbs_endprev; | |
645 | ||
646 | if (crdp == NULL || crdp == default_call_rcu_data) { | |
647 | return; | |
648 | } | |
2870aa1e PB |
649 | if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) { |
650 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP); | |
7106ddf8 | 651 | wake_call_rcu_thread(crdp); |
2870aa1e | 652 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) |
7106ddf8 PM |
653 | poll(NULL, 0, 1); |
654 | } | |
655 | if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) { | |
656 | while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL) | |
657 | poll(NULL, 0, 1); | |
658 | _CMM_STORE_SHARED(crdp->cbs.head, NULL); | |
659 | cbs_tail = (struct cds_wfq_node **) | |
660 | uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head); | |
698d0778 MD |
661 | /* Create default call rcu data if need be */ |
662 | (void) get_default_call_rcu_data(); | |
7106ddf8 | 663 | cbs_endprev = (struct cds_wfq_node **) |
a9f29e6e MD |
664 | uatomic_xchg(&default_call_rcu_data->cbs.tail, |
665 | cbs_tail); | |
666 | _CMM_STORE_SHARED(*cbs_endprev, cbs); | |
7106ddf8 PM |
667 | uatomic_add(&default_call_rcu_data->qlen, |
668 | uatomic_read(&crdp->qlen)); | |
1e92aa15 | 669 | wake_call_rcu_thread(default_call_rcu_data); |
7106ddf8 | 670 | } |
59dc9e9d | 671 | |
b75dffe6 | 672 | call_rcu_lock(&call_rcu_mutex); |
59dc9e9d | 673 | cds_list_del(&crdp->list); |
b75dffe6 LJ |
674 | call_rcu_unlock(&call_rcu_mutex); |
675 | ||
59dc9e9d | 676 | free(crdp); |
7106ddf8 PM |
677 | } |
678 | ||
679 | /* | |
680 | * Clean up all the per-CPU call_rcu threads. | |
681 | */ | |
682 | void free_all_cpu_call_rcu_data(void) | |
683 | { | |
684 | int cpu; | |
618b2595 MD |
685 | struct call_rcu_data **crdp; |
686 | static int warned = 0; | |
7106ddf8 PM |
687 | |
688 | if (maxcpus <= 0) | |
689 | return; | |
618b2595 MD |
690 | |
691 | crdp = malloc(sizeof(*crdp) * maxcpus); | |
692 | if (!crdp) { | |
693 | if (!warned) { | |
694 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); | |
695 | } | |
696 | warned = 1; | |
d31150b4 | 697 | return; |
618b2595 MD |
698 | } |
699 | ||
7106ddf8 | 700 | for (cpu = 0; cpu < maxcpus; cpu++) { |
618b2595 MD |
701 | crdp[cpu] = get_cpu_call_rcu_data(cpu); |
702 | if (crdp[cpu] == NULL) | |
7106ddf8 PM |
703 | continue; |
704 | set_cpu_call_rcu_data(cpu, NULL); | |
7106ddf8 | 705 | } |
618b2595 MD |
706 | /* |
707 | * Wait for call_rcu sites acting as RCU readers of the | |
708 | * call_rcu_data to become quiescent. | |
709 | */ | |
710 | synchronize_rcu(); | |
711 | for (cpu = 0; cpu < maxcpus; cpu++) { | |
712 | if (crdp[cpu] == NULL) | |
713 | continue; | |
714 | call_rcu_data_free(crdp[cpu]); | |
715 | } | |
716 | free(crdp); | |
7106ddf8 PM |
717 | } |
718 | ||
81ad2e19 PM |
719 | /* |
720 | * Acquire the call_rcu_mutex in order to ensure that the child sees | |
483c853e MD |
721 | * all of the call_rcu() data structures in a consistent state. Ensure |
722 | * that all call_rcu threads are in a quiescent state across fork. | |
81ad2e19 PM |
723 | * Suitable for pthread_atfork() and friends. |
724 | */ | |
725 | void call_rcu_before_fork(void) | |
726 | { | |
483c853e MD |
727 | struct call_rcu_data *crdp; |
728 | ||
81ad2e19 | 729 | call_rcu_lock(&call_rcu_mutex); |
483c853e MD |
730 | |
731 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { | |
732 | uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSE); | |
733 | cmm_smp_mb__after_uatomic_or(); | |
734 | wake_call_rcu_thread(crdp); | |
735 | } | |
736 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { | |
737 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0) | |
738 | poll(NULL, 0, 1); | |
739 | } | |
81ad2e19 PM |
740 | } |
741 | ||
742 | /* | |
743 | * Clean up call_rcu data structures in the parent of a successful fork() | |
744 | * that is not followed by exec() in the child. Suitable for | |
745 | * pthread_atfork() and friends. | |
746 | */ | |
747 | void call_rcu_after_fork_parent(void) | |
748 | { | |
483c853e MD |
749 | struct call_rcu_data *crdp; |
750 | ||
751 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) | |
752 | uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE); | |
81ad2e19 PM |
753 | call_rcu_unlock(&call_rcu_mutex); |
754 | } | |
755 | ||
7106ddf8 PM |
756 | /* |
757 | * Clean up call_rcu data structures in the child of a successful fork() | |
81ad2e19 PM |
758 | * that is not followed by exec(). Suitable for pthread_atfork() and |
759 | * friends. | |
7106ddf8 PM |
760 | */ |
761 | void call_rcu_after_fork_child(void) | |
762 | { | |
077ff173 | 763 | struct call_rcu_data *crdp, *next; |
7106ddf8 | 764 | |
81ad2e19 PM |
765 | /* Release the mutex. */ |
766 | call_rcu_unlock(&call_rcu_mutex); | |
767 | ||
ad1b9909 LJ |
768 | /* Do nothing when call_rcu() has not been used */ |
769 | if (cds_list_empty(&call_rcu_data_list)) | |
770 | return; | |
771 | ||
7106ddf8 PM |
772 | /* |
773 | * Allocate a new default call_rcu_data structure in order | |
774 | * to get a working call_rcu thread to go with it. | |
775 | */ | |
776 | default_call_rcu_data = NULL; | |
777 | (void)get_default_call_rcu_data(); | |
778 | ||
60af049d LJ |
779 | /* Cleanup call_rcu_data pointers before use */ |
780 | maxcpus_reset(); | |
781 | free(per_cpu_call_rcu_data); | |
618b2595 | 782 | rcu_set_pointer(&per_cpu_call_rcu_data, NULL); |
60af049d LJ |
783 | thread_call_rcu_data = NULL; |
784 | ||
483c853e MD |
785 | /* |
786 | * Dispose of all of the rest of the call_rcu_data structures. | |
787 | * Leftover call_rcu callbacks will be merged into the new | |
788 | * default call_rcu thread queue. | |
789 | */ | |
077ff173 | 790 | cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) { |
7106ddf8 | 791 | if (crdp == default_call_rcu_data) |
077ff173 | 792 | continue; |
2870aa1e | 793 | uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED); |
7106ddf8 | 794 | call_rcu_data_free(crdp); |
b57aee66 PM |
795 | } |
796 | } |