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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> | |
34 | #include <syscall.h> | |
35 | #include <unistd.h> | |
c1d2c60b | 36 | #include <sched.h> |
b57aee66 PM |
37 | |
38 | #include "config.h" | |
39 | #include "urcu/wfqueue.h" | |
40 | #include "urcu-call-rcu.h" | |
41 | #include "urcu-pointer.h" | |
3c24913f | 42 | #include "urcu/list.h" |
41849996 | 43 | #include "urcu/futex.h" |
b57aee66 PM |
44 | |
45 | /* Data structure that identifies a call_rcu thread. */ | |
46 | ||
47 | struct call_rcu_data { | |
48 | struct cds_wfq_queue cbs; | |
49 | unsigned long flags; | |
6d841bc2 | 50 | int32_t futex; |
73987721 | 51 | unsigned long qlen; /* maintained for debugging. */ |
b57aee66 | 52 | pthread_t tid; |
c1d2c60b | 53 | int cpu_affinity; |
3c24913f | 54 | struct cds_list_head list; |
b57aee66 PM |
55 | } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
56 | ||
3c24913f PM |
57 | /* |
58 | * List of all call_rcu_data structures to keep valgrind happy. | |
59 | * Protected by call_rcu_mutex. | |
60 | */ | |
61 | ||
62 | CDS_LIST_HEAD(call_rcu_data_list); | |
63 | ||
b57aee66 PM |
64 | /* Link a thread using call_rcu() to its call_rcu thread. */ |
65 | ||
66 | static __thread struct call_rcu_data *thread_call_rcu_data; | |
67 | ||
68 | /* Guard call_rcu thread creation. */ | |
69 | ||
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 | |
86 | * and # CPUs. | |
87 | */ | |
88 | ||
89 | static struct call_rcu_data **per_cpu_call_rcu_data; | |
90 | static long maxcpus; | |
91 | ||
263e3cf9 MD |
92 | static void call_rcu_wait(struct call_rcu_data *crdp) |
93 | { | |
94 | /* Read call_rcu list before read futex */ | |
95 | cmm_smp_mb(); | |
96 | if (uatomic_read(&crdp->futex) == -1) | |
97 | futex_async(&crdp->futex, FUTEX_WAIT, -1, | |
98 | NULL, NULL, 0); | |
99 | } | |
100 | ||
101 | static void call_rcu_wake_up(struct call_rcu_data *crdp) | |
102 | { | |
103 | /* Write to call_rcu list before reading/writing futex */ | |
104 | cmm_smp_mb(); | |
105 | if (unlikely(uatomic_read(&crdp->futex) == -1)) { | |
106 | uatomic_set(&crdp->futex, 0); | |
107 | futex_async(&crdp->futex, FUTEX_WAKE, 1, | |
108 | NULL, NULL, 0); | |
109 | } | |
110 | } | |
111 | ||
b57aee66 PM |
112 | /* Allocate the array if it has not already been allocated. */ |
113 | ||
114 | static void alloc_cpu_call_rcu_data(void) | |
115 | { | |
116 | struct call_rcu_data **p; | |
117 | static int warned = 0; | |
118 | ||
119 | if (maxcpus != 0) | |
120 | return; | |
121 | maxcpus = sysconf(_SC_NPROCESSORS_CONF); | |
122 | if (maxcpus <= 0) { | |
123 | return; | |
124 | } | |
125 | p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data)); | |
126 | if (p != NULL) { | |
127 | memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data)); | |
128 | per_cpu_call_rcu_data = p; | |
129 | } else { | |
130 | if (!warned) { | |
131 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); | |
132 | } | |
133 | warned = 1; | |
134 | } | |
135 | } | |
136 | ||
137 | #else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ | |
138 | ||
139 | static const struct call_rcu_data **per_cpu_call_rcu_data = NULL; | |
140 | static const long maxcpus = -1; | |
141 | ||
142 | static void alloc_cpu_call_rcu_data(void) | |
143 | { | |
144 | } | |
145 | ||
146 | static int sched_getcpu(void) | |
147 | { | |
148 | return -1; | |
149 | } | |
150 | ||
151 | #endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ | |
152 | ||
153 | /* Acquire the specified pthread mutex. */ | |
154 | ||
155 | static void call_rcu_lock(pthread_mutex_t *pmp) | |
156 | { | |
157 | if (pthread_mutex_lock(pmp) != 0) { | |
158 | perror("pthread_mutex_lock"); | |
159 | exit(-1); | |
160 | } | |
161 | } | |
162 | ||
163 | /* Release the specified pthread mutex. */ | |
164 | ||
165 | static void call_rcu_unlock(pthread_mutex_t *pmp) | |
166 | { | |
167 | if (pthread_mutex_unlock(pmp) != 0) { | |
168 | perror("pthread_mutex_unlock"); | |
169 | exit(-1); | |
170 | } | |
171 | } | |
172 | ||
c1d2c60b MD |
173 | #if HAVE_SCHED_SETAFFINITY |
174 | static | |
175 | int set_thread_cpu_affinity(struct call_rcu_data *crdp) | |
176 | { | |
177 | cpu_set_t mask; | |
178 | ||
179 | if (crdp->cpu_affinity < 0) | |
180 | return 0; | |
181 | ||
182 | CPU_ZERO(&mask); | |
183 | CPU_SET(crdp->cpu_affinity, &mask); | |
184 | #if SCHED_SETAFFINITY_ARGS == 2 | |
185 | return sched_setaffinity(0, &mask); | |
186 | #else | |
187 | return sched_setaffinity(0, sizeof(mask), &mask); | |
188 | #endif | |
189 | } | |
190 | #else | |
191 | static | |
192 | int set_thread_cpu_affinity(struct call_rcu_data *crdp) | |
193 | { | |
194 | return 0; | |
195 | } | |
196 | #endif | |
197 | ||
b57aee66 PM |
198 | /* This is the code run by each call_rcu thread. */ |
199 | ||
200 | static void *call_rcu_thread(void *arg) | |
201 | { | |
202 | unsigned long cbcount; | |
203 | struct cds_wfq_node *cbs; | |
204 | struct cds_wfq_node **cbs_tail; | |
205 | struct call_rcu_data *crdp = (struct call_rcu_data *)arg; | |
206 | struct rcu_head *rhp; | |
2870aa1e | 207 | int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT); |
b57aee66 | 208 | |
c1d2c60b MD |
209 | if (set_thread_cpu_affinity(crdp) != 0) { |
210 | perror("pthread_setaffinity_np"); | |
211 | exit(-1); | |
212 | } | |
213 | ||
b57aee66 | 214 | thread_call_rcu_data = crdp; |
bc94ca9b MD |
215 | if (!rt) { |
216 | uatomic_dec(&crdp->futex); | |
217 | /* Decrement futex before reading call_rcu list */ | |
218 | cmm_smp_mb(); | |
219 | } | |
b57aee66 PM |
220 | for (;;) { |
221 | if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) { | |
222 | while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL) | |
223 | poll(NULL, 0, 1); | |
224 | _CMM_STORE_SHARED(crdp->cbs.head, NULL); | |
225 | cbs_tail = (struct cds_wfq_node **) | |
226 | uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head); | |
227 | synchronize_rcu(); | |
228 | cbcount = 0; | |
229 | do { | |
230 | while (cbs->next == NULL && | |
231 | &cbs->next != cbs_tail) | |
232 | poll(NULL, 0, 1); | |
233 | if (cbs == &crdp->cbs.dummy) { | |
234 | cbs = cbs->next; | |
235 | continue; | |
236 | } | |
237 | rhp = (struct rcu_head *)cbs; | |
238 | cbs = cbs->next; | |
239 | rhp->func(rhp); | |
240 | cbcount++; | |
241 | } while (cbs != NULL); | |
242 | uatomic_sub(&crdp->qlen, cbcount); | |
243 | } | |
bc94ca9b MD |
244 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP) |
245 | break; | |
246 | if (!rt) { | |
247 | if (&crdp->cbs.head | |
248 | == _CMM_LOAD_SHARED(crdp->cbs.tail)) { | |
249 | call_rcu_wait(crdp); | |
250 | poll(NULL, 0, 10); | |
251 | uatomic_dec(&crdp->futex); | |
c768e45e | 252 | /* |
bc94ca9b MD |
253 | * Decrement futex before reading |
254 | * call_rcu list. | |
c768e45e MD |
255 | */ |
256 | cmm_smp_mb(); | |
ccbac24d MD |
257 | } else { |
258 | poll(NULL, 0, 10); | |
c768e45e | 259 | } |
bc94ca9b MD |
260 | } else { |
261 | poll(NULL, 0, 10); | |
b57aee66 | 262 | } |
bc94ca9b MD |
263 | } |
264 | if (!rt) { | |
265 | /* | |
266 | * Read call_rcu list before write futex. | |
267 | */ | |
268 | cmm_smp_mb(); | |
269 | uatomic_set(&crdp->futex, 0); | |
b57aee66 | 270 | } |
2870aa1e | 271 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED); |
7106ddf8 | 272 | return NULL; |
b57aee66 PM |
273 | } |
274 | ||
275 | /* | |
276 | * Create both a call_rcu thread and the corresponding call_rcu_data | |
3c24913f PM |
277 | * structure, linking the structure in as specified. Caller must hold |
278 | * call_rcu_mutex. | |
b57aee66 PM |
279 | */ |
280 | ||
3c24913f | 281 | static void call_rcu_data_init(struct call_rcu_data **crdpp, |
c1d2c60b MD |
282 | unsigned long flags, |
283 | int cpu_affinity) | |
b57aee66 PM |
284 | { |
285 | struct call_rcu_data *crdp; | |
286 | ||
287 | crdp = malloc(sizeof(*crdp)); | |
288 | if (crdp == NULL) { | |
289 | fprintf(stderr, "Out of memory.\n"); | |
290 | exit(-1); | |
291 | } | |
292 | memset(crdp, '\0', sizeof(*crdp)); | |
293 | cds_wfq_init(&crdp->cbs); | |
294 | crdp->qlen = 0; | |
263e3cf9 MD |
295 | crdp->futex = 0; |
296 | crdp->flags = flags; | |
3c24913f | 297 | cds_list_add(&crdp->list, &call_rcu_data_list); |
c1d2c60b | 298 | crdp->cpu_affinity = cpu_affinity; |
b57aee66 PM |
299 | cmm_smp_mb(); /* Structure initialized before pointer is planted. */ |
300 | *crdpp = crdp; | |
301 | if (pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp) != 0) { | |
302 | perror("pthread_create"); | |
303 | exit(-1); | |
304 | } | |
305 | } | |
306 | ||
307 | /* | |
308 | * Return a pointer to the call_rcu_data structure for the specified | |
309 | * CPU, returning NULL if there is none. We cannot automatically | |
310 | * created it because the platform we are running on might not define | |
311 | * sched_getcpu(). | |
312 | */ | |
313 | ||
314 | struct call_rcu_data *get_cpu_call_rcu_data(int cpu) | |
315 | { | |
316 | static int warned = 0; | |
317 | ||
318 | if (per_cpu_call_rcu_data == NULL) | |
319 | return NULL; | |
320 | if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) { | |
321 | fprintf(stderr, "[error] liburcu: get CPU # out of range\n"); | |
322 | warned = 1; | |
323 | } | |
324 | if (cpu < 0 || maxcpus <= cpu) | |
325 | return NULL; | |
326 | return per_cpu_call_rcu_data[cpu]; | |
327 | } | |
328 | ||
329 | /* | |
330 | * Return the tid corresponding to the call_rcu thread whose | |
331 | * call_rcu_data structure is specified. | |
332 | */ | |
333 | ||
334 | pthread_t get_call_rcu_thread(struct call_rcu_data *crdp) | |
335 | { | |
336 | return crdp->tid; | |
337 | } | |
338 | ||
339 | /* | |
340 | * Create a call_rcu_data structure (with thread) and return a pointer. | |
341 | */ | |
342 | ||
c1d2c60b MD |
343 | static struct call_rcu_data *__create_call_rcu_data(unsigned long flags, |
344 | int cpu_affinity) | |
b57aee66 PM |
345 | { |
346 | struct call_rcu_data *crdp; | |
347 | ||
c1d2c60b | 348 | call_rcu_data_init(&crdp, flags, cpu_affinity); |
b57aee66 PM |
349 | return crdp; |
350 | } | |
351 | ||
c1d2c60b MD |
352 | struct call_rcu_data *create_call_rcu_data(unsigned long flags, |
353 | int cpu_affinity) | |
3c24913f PM |
354 | { |
355 | struct call_rcu_data *crdp; | |
356 | ||
357 | call_rcu_lock(&call_rcu_mutex); | |
c1d2c60b | 358 | crdp = __create_call_rcu_data(flags, cpu_affinity); |
3c24913f PM |
359 | call_rcu_unlock(&call_rcu_mutex); |
360 | return crdp; | |
361 | } | |
362 | ||
b57aee66 PM |
363 | /* |
364 | * Set the specified CPU to use the specified call_rcu_data structure. | |
7106ddf8 PM |
365 | * |
366 | * Use NULL to remove a CPU's call_rcu_data structure, but it is | |
367 | * the caller's responsibility to dispose of the removed structure. | |
368 | * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure | |
369 | * (prior to NULLing it out, of course). | |
b57aee66 PM |
370 | */ |
371 | ||
372 | int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp) | |
373 | { | |
374 | int warned = 0; | |
375 | ||
376 | call_rcu_lock(&call_rcu_mutex); | |
377 | if (cpu < 0 || maxcpus <= cpu) { | |
378 | if (!warned) { | |
379 | fprintf(stderr, "[error] liburcu: set CPU # out of range\n"); | |
380 | warned = 1; | |
381 | } | |
382 | call_rcu_unlock(&call_rcu_mutex); | |
383 | errno = EINVAL; | |
384 | return -EINVAL; | |
385 | } | |
386 | alloc_cpu_call_rcu_data(); | |
387 | call_rcu_unlock(&call_rcu_mutex); | |
388 | if (per_cpu_call_rcu_data == NULL) { | |
389 | errno = ENOMEM; | |
390 | return -ENOMEM; | |
391 | } | |
392 | per_cpu_call_rcu_data[cpu] = crdp; | |
393 | return 0; | |
394 | } | |
395 | ||
396 | /* | |
397 | * Return a pointer to the default call_rcu_data structure, creating | |
398 | * one if need be. Because we never free call_rcu_data structures, | |
399 | * we don't need to be in an RCU read-side critical section. | |
400 | */ | |
401 | ||
402 | struct call_rcu_data *get_default_call_rcu_data(void) | |
403 | { | |
404 | if (default_call_rcu_data != NULL) | |
405 | return rcu_dereference(default_call_rcu_data); | |
406 | call_rcu_lock(&call_rcu_mutex); | |
407 | if (default_call_rcu_data != NULL) { | |
408 | call_rcu_unlock(&call_rcu_mutex); | |
409 | return default_call_rcu_data; | |
410 | } | |
c1d2c60b | 411 | call_rcu_data_init(&default_call_rcu_data, 0, -1); |
b57aee66 PM |
412 | call_rcu_unlock(&call_rcu_mutex); |
413 | return default_call_rcu_data; | |
414 | } | |
415 | ||
416 | /* | |
417 | * Return the call_rcu_data structure that applies to the currently | |
418 | * running thread. Any call_rcu_data structure assigned specifically | |
419 | * to this thread has first priority, followed by any call_rcu_data | |
420 | * structure assigned to the CPU on which the thread is running, | |
421 | * followed by the default call_rcu_data structure. If there is not | |
422 | * yet a default call_rcu_data structure, one will be created. | |
423 | */ | |
424 | struct call_rcu_data *get_call_rcu_data(void) | |
425 | { | |
426 | int curcpu; | |
427 | static int warned = 0; | |
428 | ||
429 | if (thread_call_rcu_data != NULL) | |
430 | return thread_call_rcu_data; | |
431 | if (maxcpus <= 0) | |
432 | return get_default_call_rcu_data(); | |
433 | curcpu = sched_getcpu(); | |
434 | if (!warned && (curcpu < 0 || maxcpus <= curcpu)) { | |
435 | fprintf(stderr, "[error] liburcu: gcrd CPU # out of range\n"); | |
436 | warned = 1; | |
437 | } | |
438 | if (curcpu >= 0 && maxcpus > curcpu && | |
439 | per_cpu_call_rcu_data != NULL && | |
440 | per_cpu_call_rcu_data[curcpu] != NULL) | |
441 | return per_cpu_call_rcu_data[curcpu]; | |
442 | return get_default_call_rcu_data(); | |
443 | } | |
444 | ||
445 | /* | |
446 | * Return a pointer to this task's call_rcu_data if there is one. | |
447 | */ | |
448 | ||
449 | struct call_rcu_data *get_thread_call_rcu_data(void) | |
450 | { | |
451 | return thread_call_rcu_data; | |
452 | } | |
453 | ||
454 | /* | |
455 | * Set this task's call_rcu_data structure as specified, regardless | |
456 | * of whether or not this task already had one. (This allows switching | |
457 | * to and from real-time call_rcu threads, for example.) | |
7106ddf8 PM |
458 | * |
459 | * Use NULL to remove a thread's call_rcu_data structure, but it is | |
460 | * the caller's responsibility to dispose of the removed structure. | |
461 | * Use get_thread_call_rcu_data() to obtain a pointer to the old structure | |
462 | * (prior to NULLing it out, of course). | |
b57aee66 PM |
463 | */ |
464 | ||
465 | void set_thread_call_rcu_data(struct call_rcu_data *crdp) | |
466 | { | |
467 | thread_call_rcu_data = crdp; | |
468 | } | |
469 | ||
470 | /* | |
471 | * Create a separate call_rcu thread for each CPU. This does not | |
472 | * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data() | |
473 | * function if you want that behavior. | |
474 | */ | |
475 | ||
476 | int create_all_cpu_call_rcu_data(unsigned long flags) | |
477 | { | |
478 | int i; | |
479 | struct call_rcu_data *crdp; | |
480 | int ret; | |
481 | ||
482 | call_rcu_lock(&call_rcu_mutex); | |
483 | alloc_cpu_call_rcu_data(); | |
484 | call_rcu_unlock(&call_rcu_mutex); | |
485 | if (maxcpus <= 0) { | |
486 | errno = EINVAL; | |
487 | return -EINVAL; | |
488 | } | |
489 | if (per_cpu_call_rcu_data == NULL) { | |
490 | errno = ENOMEM; | |
491 | return -ENOMEM; | |
492 | } | |
493 | for (i = 0; i < maxcpus; i++) { | |
494 | call_rcu_lock(&call_rcu_mutex); | |
495 | if (get_cpu_call_rcu_data(i)) { | |
496 | call_rcu_unlock(&call_rcu_mutex); | |
497 | continue; | |
498 | } | |
c1d2c60b | 499 | crdp = __create_call_rcu_data(flags, i); |
b57aee66 PM |
500 | if (crdp == NULL) { |
501 | call_rcu_unlock(&call_rcu_mutex); | |
502 | errno = ENOMEM; | |
503 | return -ENOMEM; | |
504 | } | |
505 | call_rcu_unlock(&call_rcu_mutex); | |
506 | if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) { | |
507 | /* FIXME: Leaks crdp for now. */ | |
508 | return ret; /* Can happen on race. */ | |
509 | } | |
510 | } | |
511 | return 0; | |
512 | } | |
513 | ||
7106ddf8 PM |
514 | /* |
515 | * Wake up the call_rcu thread corresponding to the specified | |
516 | * call_rcu_data structure. | |
517 | */ | |
518 | static void wake_call_rcu_thread(struct call_rcu_data *crdp) | |
519 | { | |
263e3cf9 MD |
520 | if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) |
521 | call_rcu_wake_up(crdp); | |
7106ddf8 PM |
522 | } |
523 | ||
b57aee66 PM |
524 | /* |
525 | * Schedule a function to be invoked after a following grace period. | |
526 | * This is the only function that must be called -- the others are | |
527 | * only present to allow applications to tune their use of RCU for | |
528 | * maximum performance. | |
529 | * | |
530 | * Note that unless a call_rcu thread has not already been created, | |
531 | * the first invocation of call_rcu() will create one. So, if you | |
532 | * need the first invocation of call_rcu() to be fast, make sure | |
533 | * to create a call_rcu thread first. One way to accomplish this is | |
534 | * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data(). | |
535 | */ | |
536 | ||
537 | void call_rcu(struct rcu_head *head, | |
538 | void (*func)(struct rcu_head *head)) | |
539 | { | |
540 | struct call_rcu_data *crdp; | |
541 | ||
542 | cds_wfq_node_init(&head->next); | |
543 | head->func = func; | |
544 | crdp = get_call_rcu_data(); | |
545 | cds_wfq_enqueue(&crdp->cbs, &head->next); | |
546 | uatomic_inc(&crdp->qlen); | |
7106ddf8 PM |
547 | wake_call_rcu_thread(crdp); |
548 | } | |
549 | ||
550 | /* | |
551 | * Free up the specified call_rcu_data structure, terminating the | |
552 | * associated call_rcu thread. The caller must have previously | |
553 | * removed the call_rcu_data structure from per-thread or per-CPU | |
554 | * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU | |
555 | * call_rcu_data structures or set_thread_call_rcu_data(NULL) for | |
556 | * per-thread call_rcu_data structures. | |
557 | * | |
558 | * We silently refuse to free up the default call_rcu_data structure | |
559 | * because that is where we put any leftover callbacks. Note that | |
560 | * the possibility of self-spawning callbacks makes it impossible | |
561 | * to execute all the callbacks in finite time without putting any | |
562 | * newly spawned callbacks somewhere else. The "somewhere else" of | |
563 | * last resort is the default call_rcu_data structure. | |
564 | * | |
565 | * We also silently refuse to free NULL pointers. This simplifies | |
566 | * the calling code. | |
567 | */ | |
568 | void call_rcu_data_free(struct call_rcu_data *crdp) | |
569 | { | |
570 | struct cds_wfq_node *cbs; | |
571 | struct cds_wfq_node **cbs_tail; | |
572 | struct cds_wfq_node **cbs_endprev; | |
573 | ||
574 | if (crdp == NULL || crdp == default_call_rcu_data) { | |
575 | return; | |
576 | } | |
2870aa1e PB |
577 | if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) { |
578 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP); | |
7106ddf8 | 579 | wake_call_rcu_thread(crdp); |
2870aa1e | 580 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) |
7106ddf8 PM |
581 | poll(NULL, 0, 1); |
582 | } | |
583 | if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) { | |
584 | while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL) | |
585 | poll(NULL, 0, 1); | |
586 | _CMM_STORE_SHARED(crdp->cbs.head, NULL); | |
587 | cbs_tail = (struct cds_wfq_node **) | |
588 | uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head); | |
589 | cbs_endprev = (struct cds_wfq_node **) | |
590 | uatomic_xchg(&default_call_rcu_data, cbs_tail); | |
591 | *cbs_endprev = cbs; | |
592 | uatomic_add(&default_call_rcu_data->qlen, | |
593 | uatomic_read(&crdp->qlen)); | |
594 | cds_list_del(&crdp->list); | |
595 | free(crdp); | |
596 | } | |
597 | } | |
598 | ||
599 | /* | |
600 | * Clean up all the per-CPU call_rcu threads. | |
601 | */ | |
602 | void free_all_cpu_call_rcu_data(void) | |
603 | { | |
604 | int cpu; | |
605 | struct call_rcu_data *crdp; | |
606 | ||
607 | if (maxcpus <= 0) | |
608 | return; | |
609 | for (cpu = 0; cpu < maxcpus; cpu++) { | |
610 | crdp = get_cpu_call_rcu_data(cpu); | |
611 | if (crdp == NULL) | |
612 | continue; | |
613 | set_cpu_call_rcu_data(cpu, NULL); | |
614 | call_rcu_data_free(crdp); | |
615 | } | |
616 | } | |
617 | ||
81ad2e19 PM |
618 | /* |
619 | * Acquire the call_rcu_mutex in order to ensure that the child sees | |
620 | * all of the call_rcu() data structures in a consistent state. | |
621 | * Suitable for pthread_atfork() and friends. | |
622 | */ | |
623 | void call_rcu_before_fork(void) | |
624 | { | |
625 | call_rcu_lock(&call_rcu_mutex); | |
626 | } | |
627 | ||
628 | /* | |
629 | * Clean up call_rcu data structures in the parent of a successful fork() | |
630 | * that is not followed by exec() in the child. Suitable for | |
631 | * pthread_atfork() and friends. | |
632 | */ | |
633 | void call_rcu_after_fork_parent(void) | |
634 | { | |
635 | call_rcu_unlock(&call_rcu_mutex); | |
636 | } | |
637 | ||
7106ddf8 PM |
638 | /* |
639 | * Clean up call_rcu data structures in the child of a successful fork() | |
81ad2e19 PM |
640 | * that is not followed by exec(). Suitable for pthread_atfork() and |
641 | * friends. | |
7106ddf8 PM |
642 | */ |
643 | void call_rcu_after_fork_child(void) | |
644 | { | |
645 | struct call_rcu_data *crdp; | |
646 | ||
81ad2e19 PM |
647 | /* Release the mutex. */ |
648 | call_rcu_unlock(&call_rcu_mutex); | |
649 | ||
7106ddf8 PM |
650 | /* |
651 | * Allocate a new default call_rcu_data structure in order | |
652 | * to get a working call_rcu thread to go with it. | |
653 | */ | |
654 | default_call_rcu_data = NULL; | |
655 | (void)get_default_call_rcu_data(); | |
656 | ||
657 | /* Dispose of all of the rest of the call_rcu_data structures. */ | |
658 | while (call_rcu_data_list.next != call_rcu_data_list.prev) { | |
659 | crdp = cds_list_entry(call_rcu_data_list.prev, | |
660 | struct call_rcu_data, list); | |
661 | if (crdp == default_call_rcu_data) | |
662 | crdp = cds_list_entry(crdp->list.prev, | |
663 | struct call_rcu_data, list); | |
2870aa1e | 664 | uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED); |
7106ddf8 | 665 | call_rcu_data_free(crdp); |
b57aee66 PM |
666 | } |
667 | } |