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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> | |
29 | #include <string.h> | |
30 | #include <errno.h> | |
31 | #include <poll.h> | |
32 | #include <sys/time.h> | |
33 | #include <syscall.h> | |
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" |
263e3cf9 | 42 | #include "urcu/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; | |
49 | pthread_mutex_t mtx; | |
263e3cf9 | 50 | int 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; | |
207 | ||
c1d2c60b MD |
208 | if (set_thread_cpu_affinity(crdp) != 0) { |
209 | perror("pthread_setaffinity_np"); | |
210 | exit(-1); | |
211 | } | |
212 | ||
b57aee66 PM |
213 | thread_call_rcu_data = crdp; |
214 | for (;;) { | |
c768e45e MD |
215 | if (!(crdp->flags & URCU_CALL_RCU_RT)) { |
216 | uatomic_dec(&crdp->futex); | |
217 | /* Decrement futex before reading call_rcu list */ | |
218 | cmm_smp_mb(); | |
219 | } | |
b57aee66 PM |
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 | } | |
c768e45e MD |
243 | if (crdp->flags & URCU_CALL_RCU_STOP) { |
244 | if (!(crdp->flags & URCU_CALL_RCU_RT)) { | |
245 | /* | |
246 | * Read call_rcu list before write futex. | |
247 | */ | |
248 | cmm_smp_mb(); | |
249 | uatomic_set(&crdp->futex, 0); | |
250 | } | |
7106ddf8 | 251 | break; |
c768e45e MD |
252 | } |
253 | if (!(crdp->flags & URCU_CALL_RCU_RT)) { | |
263e3cf9 MD |
254 | if (&crdp->cbs.head == _CMM_LOAD_SHARED(crdp->cbs.tail)) |
255 | call_rcu_wait(crdp); | |
b57aee66 | 256 | } |
c768e45e | 257 | poll(NULL, 0, 10); |
b57aee66 | 258 | } |
7106ddf8 PM |
259 | call_rcu_lock(&crdp->mtx); |
260 | crdp->flags |= URCU_CALL_RCU_STOPPED; | |
261 | call_rcu_unlock(&crdp->mtx); | |
262 | return NULL; | |
b57aee66 PM |
263 | } |
264 | ||
265 | /* | |
266 | * Create both a call_rcu thread and the corresponding call_rcu_data | |
3c24913f PM |
267 | * structure, linking the structure in as specified. Caller must hold |
268 | * call_rcu_mutex. | |
b57aee66 PM |
269 | */ |
270 | ||
3c24913f | 271 | static void call_rcu_data_init(struct call_rcu_data **crdpp, |
c1d2c60b MD |
272 | unsigned long flags, |
273 | int cpu_affinity) | |
b57aee66 PM |
274 | { |
275 | struct call_rcu_data *crdp; | |
276 | ||
277 | crdp = malloc(sizeof(*crdp)); | |
278 | if (crdp == NULL) { | |
279 | fprintf(stderr, "Out of memory.\n"); | |
280 | exit(-1); | |
281 | } | |
282 | memset(crdp, '\0', sizeof(*crdp)); | |
283 | cds_wfq_init(&crdp->cbs); | |
284 | crdp->qlen = 0; | |
285 | if (pthread_mutex_init(&crdp->mtx, NULL) != 0) { | |
286 | perror("pthread_mutex_init"); | |
287 | exit(-1); | |
288 | } | |
263e3cf9 MD |
289 | crdp->futex = 0; |
290 | crdp->flags = flags; | |
3c24913f | 291 | cds_list_add(&crdp->list, &call_rcu_data_list); |
c1d2c60b | 292 | crdp->cpu_affinity = cpu_affinity; |
b57aee66 PM |
293 | cmm_smp_mb(); /* Structure initialized before pointer is planted. */ |
294 | *crdpp = crdp; | |
295 | if (pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp) != 0) { | |
296 | perror("pthread_create"); | |
297 | exit(-1); | |
298 | } | |
299 | } | |
300 | ||
301 | /* | |
302 | * Return a pointer to the call_rcu_data structure for the specified | |
303 | * CPU, returning NULL if there is none. We cannot automatically | |
304 | * created it because the platform we are running on might not define | |
305 | * sched_getcpu(). | |
306 | */ | |
307 | ||
308 | struct call_rcu_data *get_cpu_call_rcu_data(int cpu) | |
309 | { | |
310 | static int warned = 0; | |
311 | ||
312 | if (per_cpu_call_rcu_data == NULL) | |
313 | return NULL; | |
314 | if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) { | |
315 | fprintf(stderr, "[error] liburcu: get CPU # out of range\n"); | |
316 | warned = 1; | |
317 | } | |
318 | if (cpu < 0 || maxcpus <= cpu) | |
319 | return NULL; | |
320 | return per_cpu_call_rcu_data[cpu]; | |
321 | } | |
322 | ||
323 | /* | |
324 | * Return the tid corresponding to the call_rcu thread whose | |
325 | * call_rcu_data structure is specified. | |
326 | */ | |
327 | ||
328 | pthread_t get_call_rcu_thread(struct call_rcu_data *crdp) | |
329 | { | |
330 | return crdp->tid; | |
331 | } | |
332 | ||
333 | /* | |
334 | * Create a call_rcu_data structure (with thread) and return a pointer. | |
335 | */ | |
336 | ||
c1d2c60b MD |
337 | static struct call_rcu_data *__create_call_rcu_data(unsigned long flags, |
338 | int cpu_affinity) | |
b57aee66 PM |
339 | { |
340 | struct call_rcu_data *crdp; | |
341 | ||
c1d2c60b | 342 | call_rcu_data_init(&crdp, flags, cpu_affinity); |
b57aee66 PM |
343 | return crdp; |
344 | } | |
345 | ||
c1d2c60b MD |
346 | struct call_rcu_data *create_call_rcu_data(unsigned long flags, |
347 | int cpu_affinity) | |
3c24913f PM |
348 | { |
349 | struct call_rcu_data *crdp; | |
350 | ||
351 | call_rcu_lock(&call_rcu_mutex); | |
c1d2c60b | 352 | crdp = __create_call_rcu_data(flags, cpu_affinity); |
3c24913f PM |
353 | call_rcu_unlock(&call_rcu_mutex); |
354 | return crdp; | |
355 | } | |
356 | ||
b57aee66 PM |
357 | /* |
358 | * Set the specified CPU to use the specified call_rcu_data structure. | |
7106ddf8 PM |
359 | * |
360 | * Use NULL to remove a CPU's call_rcu_data structure, but it is | |
361 | * the caller's responsibility to dispose of the removed structure. | |
362 | * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure | |
363 | * (prior to NULLing it out, of course). | |
b57aee66 PM |
364 | */ |
365 | ||
366 | int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp) | |
367 | { | |
368 | int warned = 0; | |
369 | ||
370 | call_rcu_lock(&call_rcu_mutex); | |
371 | if (cpu < 0 || maxcpus <= cpu) { | |
372 | if (!warned) { | |
373 | fprintf(stderr, "[error] liburcu: set CPU # out of range\n"); | |
374 | warned = 1; | |
375 | } | |
376 | call_rcu_unlock(&call_rcu_mutex); | |
377 | errno = EINVAL; | |
378 | return -EINVAL; | |
379 | } | |
380 | alloc_cpu_call_rcu_data(); | |
381 | call_rcu_unlock(&call_rcu_mutex); | |
382 | if (per_cpu_call_rcu_data == NULL) { | |
383 | errno = ENOMEM; | |
384 | return -ENOMEM; | |
385 | } | |
386 | per_cpu_call_rcu_data[cpu] = crdp; | |
387 | return 0; | |
388 | } | |
389 | ||
390 | /* | |
391 | * Return a pointer to the default call_rcu_data structure, creating | |
392 | * one if need be. Because we never free call_rcu_data structures, | |
393 | * we don't need to be in an RCU read-side critical section. | |
394 | */ | |
395 | ||
396 | struct call_rcu_data *get_default_call_rcu_data(void) | |
397 | { | |
398 | if (default_call_rcu_data != NULL) | |
399 | return rcu_dereference(default_call_rcu_data); | |
400 | call_rcu_lock(&call_rcu_mutex); | |
401 | if (default_call_rcu_data != NULL) { | |
402 | call_rcu_unlock(&call_rcu_mutex); | |
403 | return default_call_rcu_data; | |
404 | } | |
c1d2c60b | 405 | call_rcu_data_init(&default_call_rcu_data, 0, -1); |
b57aee66 PM |
406 | call_rcu_unlock(&call_rcu_mutex); |
407 | return default_call_rcu_data; | |
408 | } | |
409 | ||
410 | /* | |
411 | * Return the call_rcu_data structure that applies to the currently | |
412 | * running thread. Any call_rcu_data structure assigned specifically | |
413 | * to this thread has first priority, followed by any call_rcu_data | |
414 | * structure assigned to the CPU on which the thread is running, | |
415 | * followed by the default call_rcu_data structure. If there is not | |
416 | * yet a default call_rcu_data structure, one will be created. | |
417 | */ | |
418 | struct call_rcu_data *get_call_rcu_data(void) | |
419 | { | |
420 | int curcpu; | |
421 | static int warned = 0; | |
422 | ||
423 | if (thread_call_rcu_data != NULL) | |
424 | return thread_call_rcu_data; | |
425 | if (maxcpus <= 0) | |
426 | return get_default_call_rcu_data(); | |
427 | curcpu = sched_getcpu(); | |
428 | if (!warned && (curcpu < 0 || maxcpus <= curcpu)) { | |
429 | fprintf(stderr, "[error] liburcu: gcrd CPU # out of range\n"); | |
430 | warned = 1; | |
431 | } | |
432 | if (curcpu >= 0 && maxcpus > curcpu && | |
433 | per_cpu_call_rcu_data != NULL && | |
434 | per_cpu_call_rcu_data[curcpu] != NULL) | |
435 | return per_cpu_call_rcu_data[curcpu]; | |
436 | return get_default_call_rcu_data(); | |
437 | } | |
438 | ||
439 | /* | |
440 | * Return a pointer to this task's call_rcu_data if there is one. | |
441 | */ | |
442 | ||
443 | struct call_rcu_data *get_thread_call_rcu_data(void) | |
444 | { | |
445 | return thread_call_rcu_data; | |
446 | } | |
447 | ||
448 | /* | |
449 | * Set this task's call_rcu_data structure as specified, regardless | |
450 | * of whether or not this task already had one. (This allows switching | |
451 | * to and from real-time call_rcu threads, for example.) | |
7106ddf8 PM |
452 | * |
453 | * Use NULL to remove a thread's call_rcu_data structure, but it is | |
454 | * the caller's responsibility to dispose of the removed structure. | |
455 | * Use get_thread_call_rcu_data() to obtain a pointer to the old structure | |
456 | * (prior to NULLing it out, of course). | |
b57aee66 PM |
457 | */ |
458 | ||
459 | void set_thread_call_rcu_data(struct call_rcu_data *crdp) | |
460 | { | |
461 | thread_call_rcu_data = crdp; | |
462 | } | |
463 | ||
464 | /* | |
465 | * Create a separate call_rcu thread for each CPU. This does not | |
466 | * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data() | |
467 | * function if you want that behavior. | |
468 | */ | |
469 | ||
470 | int create_all_cpu_call_rcu_data(unsigned long flags) | |
471 | { | |
472 | int i; | |
473 | struct call_rcu_data *crdp; | |
474 | int ret; | |
475 | ||
476 | call_rcu_lock(&call_rcu_mutex); | |
477 | alloc_cpu_call_rcu_data(); | |
478 | call_rcu_unlock(&call_rcu_mutex); | |
479 | if (maxcpus <= 0) { | |
480 | errno = EINVAL; | |
481 | return -EINVAL; | |
482 | } | |
483 | if (per_cpu_call_rcu_data == NULL) { | |
484 | errno = ENOMEM; | |
485 | return -ENOMEM; | |
486 | } | |
487 | for (i = 0; i < maxcpus; i++) { | |
488 | call_rcu_lock(&call_rcu_mutex); | |
489 | if (get_cpu_call_rcu_data(i)) { | |
490 | call_rcu_unlock(&call_rcu_mutex); | |
491 | continue; | |
492 | } | |
c1d2c60b | 493 | crdp = __create_call_rcu_data(flags, i); |
b57aee66 PM |
494 | if (crdp == NULL) { |
495 | call_rcu_unlock(&call_rcu_mutex); | |
496 | errno = ENOMEM; | |
497 | return -ENOMEM; | |
498 | } | |
499 | call_rcu_unlock(&call_rcu_mutex); | |
500 | if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) { | |
501 | /* FIXME: Leaks crdp for now. */ | |
502 | return ret; /* Can happen on race. */ | |
503 | } | |
504 | } | |
505 | return 0; | |
506 | } | |
507 | ||
7106ddf8 PM |
508 | /* |
509 | * Wake up the call_rcu thread corresponding to the specified | |
510 | * call_rcu_data structure. | |
511 | */ | |
512 | static void wake_call_rcu_thread(struct call_rcu_data *crdp) | |
513 | { | |
263e3cf9 MD |
514 | if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) |
515 | call_rcu_wake_up(crdp); | |
7106ddf8 PM |
516 | } |
517 | ||
b57aee66 PM |
518 | /* |
519 | * Schedule a function to be invoked after a following grace period. | |
520 | * This is the only function that must be called -- the others are | |
521 | * only present to allow applications to tune their use of RCU for | |
522 | * maximum performance. | |
523 | * | |
524 | * Note that unless a call_rcu thread has not already been created, | |
525 | * the first invocation of call_rcu() will create one. So, if you | |
526 | * need the first invocation of call_rcu() to be fast, make sure | |
527 | * to create a call_rcu thread first. One way to accomplish this is | |
528 | * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data(). | |
529 | */ | |
530 | ||
531 | void call_rcu(struct rcu_head *head, | |
532 | void (*func)(struct rcu_head *head)) | |
533 | { | |
534 | struct call_rcu_data *crdp; | |
535 | ||
536 | cds_wfq_node_init(&head->next); | |
537 | head->func = func; | |
538 | crdp = get_call_rcu_data(); | |
539 | cds_wfq_enqueue(&crdp->cbs, &head->next); | |
540 | uatomic_inc(&crdp->qlen); | |
7106ddf8 PM |
541 | wake_call_rcu_thread(crdp); |
542 | } | |
543 | ||
544 | /* | |
545 | * Free up the specified call_rcu_data structure, terminating the | |
546 | * associated call_rcu thread. The caller must have previously | |
547 | * removed the call_rcu_data structure from per-thread or per-CPU | |
548 | * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU | |
549 | * call_rcu_data structures or set_thread_call_rcu_data(NULL) for | |
550 | * per-thread call_rcu_data structures. | |
551 | * | |
552 | * We silently refuse to free up the default call_rcu_data structure | |
553 | * because that is where we put any leftover callbacks. Note that | |
554 | * the possibility of self-spawning callbacks makes it impossible | |
555 | * to execute all the callbacks in finite time without putting any | |
556 | * newly spawned callbacks somewhere else. The "somewhere else" of | |
557 | * last resort is the default call_rcu_data structure. | |
558 | * | |
559 | * We also silently refuse to free NULL pointers. This simplifies | |
560 | * the calling code. | |
561 | */ | |
562 | void call_rcu_data_free(struct call_rcu_data *crdp) | |
563 | { | |
564 | struct cds_wfq_node *cbs; | |
565 | struct cds_wfq_node **cbs_tail; | |
566 | struct cds_wfq_node **cbs_endprev; | |
567 | ||
568 | if (crdp == NULL || crdp == default_call_rcu_data) { | |
569 | return; | |
570 | } | |
571 | if ((crdp->flags & URCU_CALL_RCU_STOPPED) == 0) { | |
b57aee66 | 572 | call_rcu_lock(&crdp->mtx); |
7106ddf8 | 573 | crdp->flags |= URCU_CALL_RCU_STOP; |
b57aee66 | 574 | call_rcu_unlock(&crdp->mtx); |
7106ddf8 PM |
575 | wake_call_rcu_thread(crdp); |
576 | while ((crdp->flags & URCU_CALL_RCU_STOPPED) == 0) | |
577 | poll(NULL, 0, 1); | |
578 | } | |
579 | if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) { | |
580 | while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL) | |
581 | poll(NULL, 0, 1); | |
582 | _CMM_STORE_SHARED(crdp->cbs.head, NULL); | |
583 | cbs_tail = (struct cds_wfq_node **) | |
584 | uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head); | |
585 | cbs_endprev = (struct cds_wfq_node **) | |
586 | uatomic_xchg(&default_call_rcu_data, cbs_tail); | |
587 | *cbs_endprev = cbs; | |
588 | uatomic_add(&default_call_rcu_data->qlen, | |
589 | uatomic_read(&crdp->qlen)); | |
590 | cds_list_del(&crdp->list); | |
591 | free(crdp); | |
592 | } | |
593 | } | |
594 | ||
595 | /* | |
596 | * Clean up all the per-CPU call_rcu threads. | |
597 | */ | |
598 | void free_all_cpu_call_rcu_data(void) | |
599 | { | |
600 | int cpu; | |
601 | struct call_rcu_data *crdp; | |
602 | ||
603 | if (maxcpus <= 0) | |
604 | return; | |
605 | for (cpu = 0; cpu < maxcpus; cpu++) { | |
606 | crdp = get_cpu_call_rcu_data(cpu); | |
607 | if (crdp == NULL) | |
608 | continue; | |
609 | set_cpu_call_rcu_data(cpu, NULL); | |
610 | call_rcu_data_free(crdp); | |
611 | } | |
612 | } | |
613 | ||
81ad2e19 PM |
614 | /* |
615 | * Acquire the call_rcu_mutex in order to ensure that the child sees | |
616 | * all of the call_rcu() data structures in a consistent state. | |
617 | * Suitable for pthread_atfork() and friends. | |
618 | */ | |
619 | void call_rcu_before_fork(void) | |
620 | { | |
621 | call_rcu_lock(&call_rcu_mutex); | |
622 | } | |
623 | ||
624 | /* | |
625 | * Clean up call_rcu data structures in the parent of a successful fork() | |
626 | * that is not followed by exec() in the child. Suitable for | |
627 | * pthread_atfork() and friends. | |
628 | */ | |
629 | void call_rcu_after_fork_parent(void) | |
630 | { | |
631 | call_rcu_unlock(&call_rcu_mutex); | |
632 | } | |
633 | ||
7106ddf8 PM |
634 | /* |
635 | * Clean up call_rcu data structures in the child of a successful fork() | |
81ad2e19 PM |
636 | * that is not followed by exec(). Suitable for pthread_atfork() and |
637 | * friends. | |
7106ddf8 PM |
638 | */ |
639 | void call_rcu_after_fork_child(void) | |
640 | { | |
641 | struct call_rcu_data *crdp; | |
642 | ||
81ad2e19 PM |
643 | /* Release the mutex. */ |
644 | call_rcu_unlock(&call_rcu_mutex); | |
645 | ||
7106ddf8 PM |
646 | /* |
647 | * Allocate a new default call_rcu_data structure in order | |
648 | * to get a working call_rcu thread to go with it. | |
649 | */ | |
650 | default_call_rcu_data = NULL; | |
651 | (void)get_default_call_rcu_data(); | |
652 | ||
653 | /* Dispose of all of the rest of the call_rcu_data structures. */ | |
654 | while (call_rcu_data_list.next != call_rcu_data_list.prev) { | |
655 | crdp = cds_list_entry(call_rcu_data_list.prev, | |
656 | struct call_rcu_data, list); | |
657 | if (crdp == default_call_rcu_data) | |
658 | crdp = cds_list_entry(crdp->list.prev, | |
659 | struct call_rcu_data, list); | |
660 | crdp->flags = URCU_CALL_RCU_STOPPED; | |
661 | call_rcu_data_free(crdp); | |
b57aee66 PM |
662 | } |
663 | } |