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