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