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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" |
bd252a04 | 43 | #include "urcu/tls-compat.h" |
4a6d7378 | 44 | #include "urcu-die.h" |
b57aee66 PM |
45 | |
46 | /* Data structure that identifies a call_rcu thread. */ | |
47 | ||
48 | struct call_rcu_data { | |
49 | struct cds_wfq_queue cbs; | |
50 | unsigned long flags; | |
6d841bc2 | 51 | int32_t futex; |
73987721 | 52 | unsigned long qlen; /* maintained for debugging. */ |
b57aee66 | 53 | pthread_t tid; |
c1d2c60b | 54 | int cpu_affinity; |
3c24913f | 55 | struct cds_list_head list; |
b57aee66 PM |
56 | } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
57 | ||
3c24913f PM |
58 | /* |
59 | * List of all call_rcu_data structures to keep valgrind happy. | |
60 | * Protected by call_rcu_mutex. | |
61 | */ | |
62 | ||
63 | CDS_LIST_HEAD(call_rcu_data_list); | |
64 | ||
b57aee66 PM |
65 | /* Link a thread using call_rcu() to its call_rcu thread. */ |
66 | ||
bd252a04 | 67 | static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data); |
b57aee66 PM |
68 | |
69 | /* Guard call_rcu thread creation. */ | |
70 | ||
71 | static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER; | |
72 | ||
73 | /* If a given thread does not have its own call_rcu thread, this is default. */ | |
74 | ||
75 | static struct call_rcu_data *default_call_rcu_data; | |
76 | ||
b57aee66 PM |
77 | /* |
78 | * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are | |
79 | * available, then we can have call_rcu threads assigned to individual | |
80 | * CPUs rather than only to specific threads. | |
81 | */ | |
82 | ||
83 | #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) | |
84 | ||
85 | /* | |
86 | * Pointer to array of pointers to per-CPU call_rcu_data structures | |
618b2595 MD |
87 | * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an |
88 | * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a | |
89 | * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer | |
90 | * without mutex. The call_rcu_mutex protects updates. | |
b57aee66 PM |
91 | */ |
92 | ||
93 | static struct call_rcu_data **per_cpu_call_rcu_data; | |
94 | static long maxcpus; | |
95 | ||
60af049d LJ |
96 | static void maxcpus_reset(void) |
97 | { | |
98 | maxcpus = 0; | |
99 | } | |
100 | ||
b57aee66 PM |
101 | /* Allocate the array if it has not already been allocated. */ |
102 | ||
103 | static void alloc_cpu_call_rcu_data(void) | |
104 | { | |
105 | struct call_rcu_data **p; | |
106 | static int warned = 0; | |
107 | ||
108 | if (maxcpus != 0) | |
109 | return; | |
110 | maxcpus = sysconf(_SC_NPROCESSORS_CONF); | |
111 | if (maxcpus <= 0) { | |
112 | return; | |
113 | } | |
114 | p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data)); | |
115 | if (p != NULL) { | |
116 | memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data)); | |
618b2595 | 117 | rcu_set_pointer(&per_cpu_call_rcu_data, p); |
b57aee66 PM |
118 | } else { |
119 | if (!warned) { | |
120 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); | |
121 | } | |
122 | warned = 1; | |
123 | } | |
124 | } | |
125 | ||
126 | #else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ | |
127 | ||
f9437098 MD |
128 | /* |
129 | * per_cpu_call_rcu_data should be constant, but some functions below, used both | |
130 | * for cases where cpu number is available and not available, assume it it not | |
131 | * constant. | |
132 | */ | |
133 | static struct call_rcu_data **per_cpu_call_rcu_data = NULL; | |
b57aee66 PM |
134 | static const long maxcpus = -1; |
135 | ||
60af049d LJ |
136 | static void maxcpus_reset(void) |
137 | { | |
138 | } | |
139 | ||
b57aee66 PM |
140 | static void alloc_cpu_call_rcu_data(void) |
141 | { | |
142 | } | |
143 | ||
144 | static int sched_getcpu(void) | |
145 | { | |
146 | return -1; | |
147 | } | |
148 | ||
149 | #endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */ | |
150 | ||
151 | /* Acquire the specified pthread mutex. */ | |
152 | ||
153 | static void call_rcu_lock(pthread_mutex_t *pmp) | |
154 | { | |
4a6d7378 MD |
155 | int ret; |
156 | ||
157 | ret = pthread_mutex_lock(pmp); | |
158 | if (ret) | |
159 | urcu_die(ret); | |
b57aee66 PM |
160 | } |
161 | ||
162 | /* Release the specified pthread mutex. */ | |
163 | ||
164 | static void call_rcu_unlock(pthread_mutex_t *pmp) | |
165 | { | |
4a6d7378 MD |
166 | int ret; |
167 | ||
168 | ret = pthread_mutex_unlock(pmp); | |
169 | if (ret) | |
170 | urcu_die(ret); | |
b57aee66 PM |
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 | ||
03fe58b3 MD |
198 | static void call_rcu_wait(struct call_rcu_data *crdp) |
199 | { | |
200 | /* Read call_rcu list before read futex */ | |
201 | cmm_smp_mb(); | |
202 | if (uatomic_read(&crdp->futex) == -1) | |
203 | futex_async(&crdp->futex, FUTEX_WAIT, -1, | |
204 | NULL, NULL, 0); | |
205 | } | |
206 | ||
207 | static void call_rcu_wake_up(struct call_rcu_data *crdp) | |
208 | { | |
209 | /* Write to call_rcu list before reading/writing futex */ | |
210 | cmm_smp_mb(); | |
a0b7f7ea | 211 | if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) { |
03fe58b3 MD |
212 | uatomic_set(&crdp->futex, 0); |
213 | futex_async(&crdp->futex, FUTEX_WAKE, 1, | |
214 | NULL, NULL, 0); | |
215 | } | |
216 | } | |
217 | ||
b57aee66 PM |
218 | /* This is the code run by each call_rcu thread. */ |
219 | ||
220 | static void *call_rcu_thread(void *arg) | |
221 | { | |
222 | unsigned long cbcount; | |
223 | struct cds_wfq_node *cbs; | |
224 | struct cds_wfq_node **cbs_tail; | |
225 | struct call_rcu_data *crdp = (struct call_rcu_data *)arg; | |
226 | struct rcu_head *rhp; | |
2870aa1e | 227 | int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT); |
4a6d7378 | 228 | int ret; |
b57aee66 | 229 | |
4a6d7378 MD |
230 | ret = set_thread_cpu_affinity(crdp); |
231 | if (ret) | |
232 | urcu_die(errno); | |
c1d2c60b | 233 | |
765f3ead MD |
234 | /* |
235 | * If callbacks take a read-side lock, we need to be registered. | |
236 | */ | |
237 | rcu_register_thread(); | |
238 | ||
bd252a04 | 239 | URCU_TLS(thread_call_rcu_data) = crdp; |
bc94ca9b MD |
240 | if (!rt) { |
241 | uatomic_dec(&crdp->futex); | |
242 | /* Decrement futex before reading call_rcu list */ | |
243 | cmm_smp_mb(); | |
244 | } | |
b57aee66 PM |
245 | for (;;) { |
246 | if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) { | |
247 | while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL) | |
248 | poll(NULL, 0, 1); | |
249 | _CMM_STORE_SHARED(crdp->cbs.head, NULL); | |
250 | cbs_tail = (struct cds_wfq_node **) | |
251 | uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head); | |
252 | synchronize_rcu(); | |
253 | cbcount = 0; | |
254 | do { | |
255 | while (cbs->next == NULL && | |
256 | &cbs->next != cbs_tail) | |
257 | poll(NULL, 0, 1); | |
258 | if (cbs == &crdp->cbs.dummy) { | |
259 | cbs = cbs->next; | |
260 | continue; | |
261 | } | |
262 | rhp = (struct rcu_head *)cbs; | |
263 | cbs = cbs->next; | |
264 | rhp->func(rhp); | |
265 | cbcount++; | |
266 | } while (cbs != NULL); | |
267 | uatomic_sub(&crdp->qlen, cbcount); | |
268 | } | |
bc94ca9b MD |
269 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP) |
270 | break; | |
765f3ead | 271 | rcu_thread_offline(); |
bc94ca9b MD |
272 | if (!rt) { |
273 | if (&crdp->cbs.head | |
274 | == _CMM_LOAD_SHARED(crdp->cbs.tail)) { | |
275 | call_rcu_wait(crdp); | |
276 | poll(NULL, 0, 10); | |
277 | uatomic_dec(&crdp->futex); | |
c768e45e | 278 | /* |
bc94ca9b MD |
279 | * Decrement futex before reading |
280 | * call_rcu list. | |
c768e45e MD |
281 | */ |
282 | cmm_smp_mb(); | |
ccbac24d MD |
283 | } else { |
284 | poll(NULL, 0, 10); | |
c768e45e | 285 | } |
bc94ca9b MD |
286 | } else { |
287 | poll(NULL, 0, 10); | |
b57aee66 | 288 | } |
765f3ead | 289 | rcu_thread_online(); |
bc94ca9b MD |
290 | } |
291 | if (!rt) { | |
292 | /* | |
293 | * Read call_rcu list before write futex. | |
294 | */ | |
295 | cmm_smp_mb(); | |
296 | uatomic_set(&crdp->futex, 0); | |
b57aee66 | 297 | } |
2870aa1e | 298 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED); |
765f3ead | 299 | rcu_unregister_thread(); |
7106ddf8 | 300 | return NULL; |
b57aee66 PM |
301 | } |
302 | ||
303 | /* | |
304 | * Create both a call_rcu thread and the corresponding call_rcu_data | |
3c24913f PM |
305 | * structure, linking the structure in as specified. Caller must hold |
306 | * call_rcu_mutex. | |
b57aee66 PM |
307 | */ |
308 | ||
3c24913f | 309 | static void call_rcu_data_init(struct call_rcu_data **crdpp, |
c1d2c60b MD |
310 | unsigned long flags, |
311 | int cpu_affinity) | |
b57aee66 PM |
312 | { |
313 | struct call_rcu_data *crdp; | |
4a6d7378 | 314 | int ret; |
b57aee66 PM |
315 | |
316 | crdp = malloc(sizeof(*crdp)); | |
4a6d7378 MD |
317 | if (crdp == NULL) |
318 | urcu_die(errno); | |
b57aee66 PM |
319 | memset(crdp, '\0', sizeof(*crdp)); |
320 | cds_wfq_init(&crdp->cbs); | |
321 | crdp->qlen = 0; | |
263e3cf9 MD |
322 | crdp->futex = 0; |
323 | crdp->flags = flags; | |
3c24913f | 324 | cds_list_add(&crdp->list, &call_rcu_data_list); |
c1d2c60b | 325 | crdp->cpu_affinity = cpu_affinity; |
b57aee66 PM |
326 | cmm_smp_mb(); /* Structure initialized before pointer is planted. */ |
327 | *crdpp = crdp; | |
4a6d7378 MD |
328 | ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp); |
329 | if (ret) | |
330 | urcu_die(ret); | |
b57aee66 PM |
331 | } |
332 | ||
333 | /* | |
334 | * Return a pointer to the call_rcu_data structure for the specified | |
335 | * CPU, returning NULL if there is none. We cannot automatically | |
336 | * created it because the platform we are running on might not define | |
337 | * sched_getcpu(). | |
618b2595 MD |
338 | * |
339 | * The call to this function and use of the returned call_rcu_data | |
340 | * should be protected by RCU read-side lock. | |
b57aee66 PM |
341 | */ |
342 | ||
343 | struct call_rcu_data *get_cpu_call_rcu_data(int cpu) | |
344 | { | |
345 | static int warned = 0; | |
618b2595 | 346 | struct call_rcu_data **pcpu_crdp; |
b57aee66 | 347 | |
618b2595 MD |
348 | pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data); |
349 | if (pcpu_crdp == NULL) | |
b57aee66 PM |
350 | return NULL; |
351 | if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) { | |
352 | fprintf(stderr, "[error] liburcu: get CPU # out of range\n"); | |
353 | warned = 1; | |
354 | } | |
355 | if (cpu < 0 || maxcpus <= cpu) | |
356 | return NULL; | |
618b2595 | 357 | return rcu_dereference(pcpu_crdp[cpu]); |
b57aee66 PM |
358 | } |
359 | ||
360 | /* | |
361 | * Return the tid corresponding to the call_rcu thread whose | |
362 | * call_rcu_data structure is specified. | |
363 | */ | |
364 | ||
365 | pthread_t get_call_rcu_thread(struct call_rcu_data *crdp) | |
366 | { | |
367 | return crdp->tid; | |
368 | } | |
369 | ||
370 | /* | |
371 | * Create a call_rcu_data structure (with thread) and return a pointer. | |
372 | */ | |
373 | ||
c1d2c60b MD |
374 | static struct call_rcu_data *__create_call_rcu_data(unsigned long flags, |
375 | int cpu_affinity) | |
b57aee66 PM |
376 | { |
377 | struct call_rcu_data *crdp; | |
378 | ||
c1d2c60b | 379 | call_rcu_data_init(&crdp, flags, cpu_affinity); |
b57aee66 PM |
380 | return crdp; |
381 | } | |
382 | ||
c1d2c60b MD |
383 | struct call_rcu_data *create_call_rcu_data(unsigned long flags, |
384 | int cpu_affinity) | |
3c24913f PM |
385 | { |
386 | struct call_rcu_data *crdp; | |
387 | ||
388 | call_rcu_lock(&call_rcu_mutex); | |
c1d2c60b | 389 | crdp = __create_call_rcu_data(flags, cpu_affinity); |
3c24913f PM |
390 | call_rcu_unlock(&call_rcu_mutex); |
391 | return crdp; | |
392 | } | |
393 | ||
b57aee66 PM |
394 | /* |
395 | * Set the specified CPU to use the specified call_rcu_data structure. | |
7106ddf8 PM |
396 | * |
397 | * Use NULL to remove a CPU's call_rcu_data structure, but it is | |
398 | * the caller's responsibility to dispose of the removed structure. | |
399 | * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure | |
400 | * (prior to NULLing it out, of course). | |
f9da0936 MD |
401 | * |
402 | * The caller must wait for a grace-period to pass between return from | |
403 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the | |
404 | * previous call rcu data as argument. | |
b57aee66 PM |
405 | */ |
406 | ||
407 | int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp) | |
408 | { | |
dcfc8165 | 409 | static int warned = 0; |
b57aee66 PM |
410 | |
411 | call_rcu_lock(&call_rcu_mutex); | |
f3776786 | 412 | alloc_cpu_call_rcu_data(); |
b57aee66 PM |
413 | if (cpu < 0 || maxcpus <= cpu) { |
414 | if (!warned) { | |
415 | fprintf(stderr, "[error] liburcu: set CPU # out of range\n"); | |
416 | warned = 1; | |
417 | } | |
418 | call_rcu_unlock(&call_rcu_mutex); | |
419 | errno = EINVAL; | |
420 | return -EINVAL; | |
421 | } | |
53a55535 | 422 | |
b57aee66 | 423 | if (per_cpu_call_rcu_data == NULL) { |
3670fef2 | 424 | call_rcu_unlock(&call_rcu_mutex); |
b57aee66 PM |
425 | errno = ENOMEM; |
426 | return -ENOMEM; | |
427 | } | |
53a55535 LJ |
428 | |
429 | if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) { | |
430 | call_rcu_unlock(&call_rcu_mutex); | |
431 | errno = EEXIST; | |
432 | return -EEXIST; | |
433 | } | |
434 | ||
618b2595 | 435 | rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp); |
3670fef2 | 436 | call_rcu_unlock(&call_rcu_mutex); |
b57aee66 PM |
437 | return 0; |
438 | } | |
439 | ||
440 | /* | |
441 | * Return a pointer to the default call_rcu_data structure, creating | |
442 | * one if need be. Because we never free call_rcu_data structures, | |
443 | * we don't need to be in an RCU read-side critical section. | |
444 | */ | |
445 | ||
446 | struct call_rcu_data *get_default_call_rcu_data(void) | |
447 | { | |
448 | if (default_call_rcu_data != NULL) | |
449 | return rcu_dereference(default_call_rcu_data); | |
450 | call_rcu_lock(&call_rcu_mutex); | |
451 | if (default_call_rcu_data != NULL) { | |
452 | call_rcu_unlock(&call_rcu_mutex); | |
453 | return default_call_rcu_data; | |
454 | } | |
c1d2c60b | 455 | call_rcu_data_init(&default_call_rcu_data, 0, -1); |
b57aee66 PM |
456 | call_rcu_unlock(&call_rcu_mutex); |
457 | return default_call_rcu_data; | |
458 | } | |
459 | ||
460 | /* | |
461 | * Return the call_rcu_data structure that applies to the currently | |
462 | * running thread. Any call_rcu_data structure assigned specifically | |
463 | * to this thread has first priority, followed by any call_rcu_data | |
464 | * structure assigned to the CPU on which the thread is running, | |
465 | * followed by the default call_rcu_data structure. If there is not | |
466 | * yet a default call_rcu_data structure, one will be created. | |
618b2595 MD |
467 | * |
468 | * Calls to this function and use of the returned call_rcu_data should | |
469 | * be protected by RCU read-side lock. | |
b57aee66 PM |
470 | */ |
471 | struct call_rcu_data *get_call_rcu_data(void) | |
472 | { | |
9744f3bb | 473 | struct call_rcu_data *crd; |
b57aee66 | 474 | |
bd252a04 MD |
475 | if (URCU_TLS(thread_call_rcu_data) != NULL) |
476 | return URCU_TLS(thread_call_rcu_data); | |
9744f3bb LJ |
477 | |
478 | if (maxcpus > 0) { | |
479 | crd = get_cpu_call_rcu_data(sched_getcpu()); | |
480 | if (crd) | |
481 | return crd; | |
b57aee66 | 482 | } |
9744f3bb | 483 | |
b57aee66 PM |
484 | return get_default_call_rcu_data(); |
485 | } | |
486 | ||
487 | /* | |
488 | * Return a pointer to this task's call_rcu_data if there is one. | |
489 | */ | |
490 | ||
491 | struct call_rcu_data *get_thread_call_rcu_data(void) | |
492 | { | |
bd252a04 | 493 | return URCU_TLS(thread_call_rcu_data); |
b57aee66 PM |
494 | } |
495 | ||
496 | /* | |
497 | * Set this task's call_rcu_data structure as specified, regardless | |
498 | * of whether or not this task already had one. (This allows switching | |
499 | * to and from real-time call_rcu threads, for example.) | |
7106ddf8 PM |
500 | * |
501 | * Use NULL to remove a thread's call_rcu_data structure, but it is | |
502 | * the caller's responsibility to dispose of the removed structure. | |
503 | * Use get_thread_call_rcu_data() to obtain a pointer to the old structure | |
504 | * (prior to NULLing it out, of course). | |
b57aee66 PM |
505 | */ |
506 | ||
507 | void set_thread_call_rcu_data(struct call_rcu_data *crdp) | |
508 | { | |
bd252a04 | 509 | URCU_TLS(thread_call_rcu_data) = crdp; |
b57aee66 PM |
510 | } |
511 | ||
512 | /* | |
513 | * Create a separate call_rcu thread for each CPU. This does not | |
514 | * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data() | |
0938c541 MD |
515 | * function if you want that behavior. Should be paired with |
516 | * free_all_cpu_call_rcu_data() to teardown these call_rcu worker | |
517 | * threads. | |
b57aee66 PM |
518 | */ |
519 | ||
520 | int create_all_cpu_call_rcu_data(unsigned long flags) | |
521 | { | |
522 | int i; | |
523 | struct call_rcu_data *crdp; | |
524 | int ret; | |
525 | ||
526 | call_rcu_lock(&call_rcu_mutex); | |
527 | alloc_cpu_call_rcu_data(); | |
528 | call_rcu_unlock(&call_rcu_mutex); | |
529 | if (maxcpus <= 0) { | |
530 | errno = EINVAL; | |
531 | return -EINVAL; | |
532 | } | |
533 | if (per_cpu_call_rcu_data == NULL) { | |
534 | errno = ENOMEM; | |
535 | return -ENOMEM; | |
536 | } | |
537 | for (i = 0; i < maxcpus; i++) { | |
538 | call_rcu_lock(&call_rcu_mutex); | |
539 | if (get_cpu_call_rcu_data(i)) { | |
540 | call_rcu_unlock(&call_rcu_mutex); | |
541 | continue; | |
542 | } | |
c1d2c60b | 543 | crdp = __create_call_rcu_data(flags, i); |
b57aee66 PM |
544 | if (crdp == NULL) { |
545 | call_rcu_unlock(&call_rcu_mutex); | |
546 | errno = ENOMEM; | |
547 | return -ENOMEM; | |
548 | } | |
549 | call_rcu_unlock(&call_rcu_mutex); | |
550 | if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) { | |
356c8794 LJ |
551 | call_rcu_data_free(crdp); |
552 | ||
553 | /* it has been created by other thread */ | |
554 | if (ret == -EEXIST) | |
555 | continue; | |
556 | ||
557 | return ret; | |
b57aee66 PM |
558 | } |
559 | } | |
560 | return 0; | |
561 | } | |
562 | ||
7106ddf8 PM |
563 | /* |
564 | * Wake up the call_rcu thread corresponding to the specified | |
565 | * call_rcu_data structure. | |
566 | */ | |
567 | static void wake_call_rcu_thread(struct call_rcu_data *crdp) | |
568 | { | |
263e3cf9 MD |
569 | if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) |
570 | call_rcu_wake_up(crdp); | |
7106ddf8 PM |
571 | } |
572 | ||
b57aee66 PM |
573 | /* |
574 | * Schedule a function to be invoked after a following grace period. | |
575 | * This is the only function that must be called -- the others are | |
576 | * only present to allow applications to tune their use of RCU for | |
577 | * maximum performance. | |
578 | * | |
579 | * Note that unless a call_rcu thread has not already been created, | |
580 | * the first invocation of call_rcu() will create one. So, if you | |
581 | * need the first invocation of call_rcu() to be fast, make sure | |
582 | * to create a call_rcu thread first. One way to accomplish this is | |
583 | * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data(). | |
618b2595 MD |
584 | * |
585 | * call_rcu must be called by registered RCU read-side threads. | |
b57aee66 PM |
586 | */ |
587 | ||
588 | void call_rcu(struct rcu_head *head, | |
589 | void (*func)(struct rcu_head *head)) | |
590 | { | |
591 | struct call_rcu_data *crdp; | |
592 | ||
593 | cds_wfq_node_init(&head->next); | |
594 | head->func = func; | |
618b2595 MD |
595 | /* Holding rcu read-side lock across use of per-cpu crdp */ |
596 | rcu_read_lock(); | |
b57aee66 PM |
597 | crdp = get_call_rcu_data(); |
598 | cds_wfq_enqueue(&crdp->cbs, &head->next); | |
599 | uatomic_inc(&crdp->qlen); | |
7106ddf8 | 600 | wake_call_rcu_thread(crdp); |
618b2595 | 601 | rcu_read_unlock(); |
7106ddf8 PM |
602 | } |
603 | ||
604 | /* | |
605 | * Free up the specified call_rcu_data structure, terminating the | |
606 | * associated call_rcu thread. The caller must have previously | |
607 | * removed the call_rcu_data structure from per-thread or per-CPU | |
608 | * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU | |
609 | * call_rcu_data structures or set_thread_call_rcu_data(NULL) for | |
610 | * per-thread call_rcu_data structures. | |
611 | * | |
612 | * We silently refuse to free up the default call_rcu_data structure | |
613 | * because that is where we put any leftover callbacks. Note that | |
614 | * the possibility of self-spawning callbacks makes it impossible | |
615 | * to execute all the callbacks in finite time without putting any | |
616 | * newly spawned callbacks somewhere else. The "somewhere else" of | |
617 | * last resort is the default call_rcu_data structure. | |
618 | * | |
619 | * We also silently refuse to free NULL pointers. This simplifies | |
620 | * the calling code. | |
f9da0936 MD |
621 | * |
622 | * The caller must wait for a grace-period to pass between return from | |
623 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the | |
624 | * previous call rcu data as argument. | |
7106ddf8 PM |
625 | */ |
626 | void call_rcu_data_free(struct call_rcu_data *crdp) | |
627 | { | |
628 | struct cds_wfq_node *cbs; | |
629 | struct cds_wfq_node **cbs_tail; | |
630 | struct cds_wfq_node **cbs_endprev; | |
631 | ||
632 | if (crdp == NULL || crdp == default_call_rcu_data) { | |
633 | return; | |
634 | } | |
2870aa1e PB |
635 | if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) { |
636 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP); | |
7106ddf8 | 637 | wake_call_rcu_thread(crdp); |
2870aa1e | 638 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) |
7106ddf8 PM |
639 | poll(NULL, 0, 1); |
640 | } | |
641 | if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) { | |
642 | while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL) | |
643 | poll(NULL, 0, 1); | |
644 | _CMM_STORE_SHARED(crdp->cbs.head, NULL); | |
645 | cbs_tail = (struct cds_wfq_node **) | |
646 | uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head); | |
698d0778 MD |
647 | /* Create default call rcu data if need be */ |
648 | (void) get_default_call_rcu_data(); | |
7106ddf8 | 649 | cbs_endprev = (struct cds_wfq_node **) |
19cf3ae1 MD |
650 | uatomic_xchg(&default_call_rcu_data->cbs.tail, |
651 | cbs_tail); | |
652 | _CMM_STORE_SHARED(*cbs_endprev, cbs); | |
7106ddf8 PM |
653 | uatomic_add(&default_call_rcu_data->qlen, |
654 | uatomic_read(&crdp->qlen)); | |
1e92aa15 | 655 | wake_call_rcu_thread(default_call_rcu_data); |
7106ddf8 | 656 | } |
59dc9e9d | 657 | |
b75dffe6 | 658 | call_rcu_lock(&call_rcu_mutex); |
59dc9e9d | 659 | cds_list_del(&crdp->list); |
b75dffe6 LJ |
660 | call_rcu_unlock(&call_rcu_mutex); |
661 | ||
59dc9e9d | 662 | free(crdp); |
7106ddf8 PM |
663 | } |
664 | ||
665 | /* | |
666 | * Clean up all the per-CPU call_rcu threads. | |
667 | */ | |
668 | void free_all_cpu_call_rcu_data(void) | |
669 | { | |
670 | int cpu; | |
618b2595 MD |
671 | struct call_rcu_data **crdp; |
672 | static int warned = 0; | |
7106ddf8 PM |
673 | |
674 | if (maxcpus <= 0) | |
675 | return; | |
618b2595 MD |
676 | |
677 | crdp = malloc(sizeof(*crdp) * maxcpus); | |
678 | if (!crdp) { | |
679 | if (!warned) { | |
680 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); | |
681 | } | |
682 | warned = 1; | |
d31150b4 | 683 | return; |
618b2595 MD |
684 | } |
685 | ||
7106ddf8 | 686 | for (cpu = 0; cpu < maxcpus; cpu++) { |
618b2595 MD |
687 | crdp[cpu] = get_cpu_call_rcu_data(cpu); |
688 | if (crdp[cpu] == NULL) | |
7106ddf8 PM |
689 | continue; |
690 | set_cpu_call_rcu_data(cpu, NULL); | |
7106ddf8 | 691 | } |
618b2595 MD |
692 | /* |
693 | * Wait for call_rcu sites acting as RCU readers of the | |
694 | * call_rcu_data to become quiescent. | |
695 | */ | |
696 | synchronize_rcu(); | |
697 | for (cpu = 0; cpu < maxcpus; cpu++) { | |
698 | if (crdp[cpu] == NULL) | |
699 | continue; | |
700 | call_rcu_data_free(crdp[cpu]); | |
701 | } | |
702 | free(crdp); | |
7106ddf8 PM |
703 | } |
704 | ||
81ad2e19 PM |
705 | /* |
706 | * Acquire the call_rcu_mutex in order to ensure that the child sees | |
707 | * all of the call_rcu() data structures in a consistent state. | |
708 | * Suitable for pthread_atfork() and friends. | |
709 | */ | |
710 | void call_rcu_before_fork(void) | |
711 | { | |
712 | call_rcu_lock(&call_rcu_mutex); | |
713 | } | |
714 | ||
715 | /* | |
716 | * Clean up call_rcu data structures in the parent of a successful fork() | |
717 | * that is not followed by exec() in the child. Suitable for | |
718 | * pthread_atfork() and friends. | |
719 | */ | |
720 | void call_rcu_after_fork_parent(void) | |
721 | { | |
722 | call_rcu_unlock(&call_rcu_mutex); | |
723 | } | |
724 | ||
7106ddf8 PM |
725 | /* |
726 | * Clean up call_rcu data structures in the child of a successful fork() | |
81ad2e19 PM |
727 | * that is not followed by exec(). Suitable for pthread_atfork() and |
728 | * friends. | |
7106ddf8 PM |
729 | */ |
730 | void call_rcu_after_fork_child(void) | |
731 | { | |
077ff173 | 732 | struct call_rcu_data *crdp, *next; |
7106ddf8 | 733 | |
81ad2e19 PM |
734 | /* Release the mutex. */ |
735 | call_rcu_unlock(&call_rcu_mutex); | |
736 | ||
ad1b9909 LJ |
737 | /* Do nothing when call_rcu() has not been used */ |
738 | if (cds_list_empty(&call_rcu_data_list)) | |
739 | return; | |
740 | ||
7106ddf8 PM |
741 | /* |
742 | * Allocate a new default call_rcu_data structure in order | |
743 | * to get a working call_rcu thread to go with it. | |
744 | */ | |
745 | default_call_rcu_data = NULL; | |
746 | (void)get_default_call_rcu_data(); | |
747 | ||
60af049d LJ |
748 | /* Cleanup call_rcu_data pointers before use */ |
749 | maxcpus_reset(); | |
750 | free(per_cpu_call_rcu_data); | |
618b2595 | 751 | rcu_set_pointer(&per_cpu_call_rcu_data, NULL); |
bd252a04 | 752 | URCU_TLS(thread_call_rcu_data) = NULL; |
60af049d | 753 | |
7106ddf8 | 754 | /* Dispose of all of the rest of the call_rcu_data structures. */ |
077ff173 | 755 | cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) { |
7106ddf8 | 756 | if (crdp == default_call_rcu_data) |
077ff173 | 757 | continue; |
2870aa1e | 758 | uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED); |
7106ddf8 | 759 | call_rcu_data_free(crdp); |
b57aee66 PM |
760 | } |
761 | } |