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