Commit | Line | Data |
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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 |
5161f31e | 24 | #define _LGPL_SOURCE |
b57aee66 PM |
25 | #include <stdio.h> |
26 | #include <pthread.h> | |
27 | #include <signal.h> | |
28 | #include <assert.h> | |
29 | #include <stdlib.h> | |
6d841bc2 | 30 | #include <stdint.h> |
b57aee66 PM |
31 | #include <string.h> |
32 | #include <errno.h> | |
33 | #include <poll.h> | |
34 | #include <sys/time.h> | |
b57aee66 | 35 | #include <unistd.h> |
c1d2c60b | 36 | #include <sched.h> |
b57aee66 PM |
37 | |
38 | #include "config.h" | |
5161f31e | 39 | #include "urcu/wfcqueue.h" |
b57aee66 PM |
40 | #include "urcu-call-rcu.h" |
41 | #include "urcu-pointer.h" | |
3c24913f | 42 | #include "urcu/list.h" |
41849996 | 43 | #include "urcu/futex.h" |
bd252a04 | 44 | #include "urcu/tls-compat.h" |
81dd9134 | 45 | #include "urcu/ref.h" |
4a6d7378 | 46 | #include "urcu-die.h" |
b57aee66 | 47 | |
8e3690db MD |
48 | #define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */ |
49 | #define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1) | |
50 | ||
b57aee66 PM |
51 | /* Data structure that identifies a call_rcu thread. */ |
52 | ||
53 | struct call_rcu_data { | |
5161f31e | 54 | /* |
0b8ab7df MD |
55 | * We do not align head on a different cache-line than tail |
56 | * mainly because call_rcu callback-invocation threads use | |
57 | * batching ("splice") to get an entire list of callbacks, which | |
58 | * effectively empties the queue, and requires to touch the tail | |
59 | * anyway. | |
5161f31e | 60 | */ |
b9f893b6 | 61 | struct cds_wfcq_tail cbs_tail; |
0b8ab7df | 62 | struct cds_wfcq_head cbs_head; |
b57aee66 | 63 | unsigned long flags; |
6d841bc2 | 64 | int32_t futex; |
73987721 | 65 | unsigned long qlen; /* maintained for debugging. */ |
b57aee66 | 66 | pthread_t tid; |
c1d2c60b | 67 | int cpu_affinity; |
8e3690db | 68 | unsigned long gp_count; |
3c24913f | 69 | struct cds_list_head list; |
b57aee66 PM |
70 | } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); |
71 | ||
b7f721d9 MD |
72 | struct call_rcu_completion { |
73 | int barrier_count; | |
74 | int32_t futex; | |
81dd9134 | 75 | struct urcu_ref ref; |
b7f721d9 MD |
76 | }; |
77 | ||
78 | struct call_rcu_completion_work { | |
79 | struct rcu_head head; | |
80 | struct call_rcu_completion *completion; | |
81 | }; | |
82 | ||
3c24913f PM |
83 | /* |
84 | * List of all call_rcu_data structures to keep valgrind happy. | |
85 | * Protected by call_rcu_mutex. | |
86 | */ | |
87 | ||
bab44e28 | 88 | static CDS_LIST_HEAD(call_rcu_data_list); |
3c24913f | 89 | |
b57aee66 PM |
90 | /* Link a thread using call_rcu() to its call_rcu thread. */ |
91 | ||
bd252a04 | 92 | static DEFINE_URCU_TLS(struct call_rcu_data *, thread_call_rcu_data); |
b57aee66 | 93 | |
e85451a1 MD |
94 | /* |
95 | * Guard call_rcu thread creation and atfork handlers. | |
96 | */ | |
b57aee66 PM |
97 | static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER; |
98 | ||
99 | /* If a given thread does not have its own call_rcu thread, this is default. */ | |
100 | ||
101 | static struct call_rcu_data *default_call_rcu_data; | |
102 | ||
b57aee66 PM |
103 | /* |
104 | * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are | |
105 | * available, then we can have call_rcu threads assigned to individual | |
106 | * CPUs rather than only to specific threads. | |
107 | */ | |
108 | ||
63b495d8 MD |
109 | #ifdef HAVE_SCHED_GETCPU |
110 | ||
111 | static int urcu_sched_getcpu(void) | |
112 | { | |
113 | return sched_getcpu(); | |
114 | } | |
115 | ||
116 | #else /* #ifdef HAVE_SCHED_GETCPU */ | |
117 | ||
118 | static int urcu_sched_getcpu(void) | |
119 | { | |
120 | return -1; | |
121 | } | |
122 | ||
123 | #endif /* #else #ifdef HAVE_SCHED_GETCPU */ | |
124 | ||
125 | #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) | |
b57aee66 PM |
126 | |
127 | /* | |
128 | * Pointer to array of pointers to per-CPU call_rcu_data structures | |
618b2595 MD |
129 | * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an |
130 | * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a | |
131 | * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer | |
132 | * without mutex. The call_rcu_mutex protects updates. | |
b57aee66 PM |
133 | */ |
134 | ||
135 | static struct call_rcu_data **per_cpu_call_rcu_data; | |
136 | static long maxcpus; | |
137 | ||
60af049d LJ |
138 | static void maxcpus_reset(void) |
139 | { | |
140 | maxcpus = 0; | |
141 | } | |
142 | ||
b57aee66 PM |
143 | /* Allocate the array if it has not already been allocated. */ |
144 | ||
145 | static void alloc_cpu_call_rcu_data(void) | |
146 | { | |
147 | struct call_rcu_data **p; | |
148 | static int warned = 0; | |
149 | ||
150 | if (maxcpus != 0) | |
151 | return; | |
152 | maxcpus = sysconf(_SC_NPROCESSORS_CONF); | |
153 | if (maxcpus <= 0) { | |
154 | return; | |
155 | } | |
156 | p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data)); | |
157 | if (p != NULL) { | |
158 | memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data)); | |
618b2595 | 159 | rcu_set_pointer(&per_cpu_call_rcu_data, p); |
b57aee66 PM |
160 | } else { |
161 | if (!warned) { | |
162 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); | |
163 | } | |
164 | warned = 1; | |
165 | } | |
166 | } | |
167 | ||
63b495d8 | 168 | #else /* #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */ |
b57aee66 | 169 | |
f9437098 MD |
170 | /* |
171 | * per_cpu_call_rcu_data should be constant, but some functions below, used both | |
172 | * for cases where cpu number is available and not available, assume it it not | |
173 | * constant. | |
174 | */ | |
175 | static struct call_rcu_data **per_cpu_call_rcu_data = NULL; | |
b57aee66 PM |
176 | static const long maxcpus = -1; |
177 | ||
60af049d LJ |
178 | static void maxcpus_reset(void) |
179 | { | |
180 | } | |
181 | ||
b57aee66 PM |
182 | static void alloc_cpu_call_rcu_data(void) |
183 | { | |
184 | } | |
185 | ||
63b495d8 | 186 | #endif /* #else #if defined(HAVE_SYSCONF) && defined(HAVE_SCHED_GETCPU) */ |
b57aee66 PM |
187 | |
188 | /* Acquire the specified pthread mutex. */ | |
189 | ||
190 | static void call_rcu_lock(pthread_mutex_t *pmp) | |
191 | { | |
4a6d7378 MD |
192 | int ret; |
193 | ||
194 | ret = pthread_mutex_lock(pmp); | |
195 | if (ret) | |
196 | urcu_die(ret); | |
b57aee66 PM |
197 | } |
198 | ||
199 | /* Release the specified pthread mutex. */ | |
200 | ||
201 | static void call_rcu_unlock(pthread_mutex_t *pmp) | |
202 | { | |
4a6d7378 MD |
203 | int ret; |
204 | ||
205 | ret = pthread_mutex_unlock(pmp); | |
206 | if (ret) | |
207 | urcu_die(ret); | |
b57aee66 PM |
208 | } |
209 | ||
8e3690db MD |
210 | /* |
211 | * Periodically retry setting CPU affinity if we migrate. | |
212 | * Losing affinity can be caused by CPU hotunplug/hotplug, or by | |
213 | * cpuset(7). | |
214 | */ | |
c1d2c60b MD |
215 | #if HAVE_SCHED_SETAFFINITY |
216 | static | |
217 | int set_thread_cpu_affinity(struct call_rcu_data *crdp) | |
218 | { | |
219 | cpu_set_t mask; | |
8e3690db | 220 | int ret; |
c1d2c60b MD |
221 | |
222 | if (crdp->cpu_affinity < 0) | |
223 | return 0; | |
8e3690db MD |
224 | if (++crdp->gp_count & SET_AFFINITY_CHECK_PERIOD_MASK) |
225 | return 0; | |
226 | if (urcu_sched_getcpu() == crdp->cpu_affinity) | |
227 | return 0; | |
c1d2c60b MD |
228 | |
229 | CPU_ZERO(&mask); | |
230 | CPU_SET(crdp->cpu_affinity, &mask); | |
231 | #if SCHED_SETAFFINITY_ARGS == 2 | |
8e3690db | 232 | ret = sched_setaffinity(0, &mask); |
c1d2c60b | 233 | #else |
8e3690db | 234 | ret = sched_setaffinity(0, sizeof(mask), &mask); |
c1d2c60b | 235 | #endif |
8e3690db MD |
236 | /* |
237 | * EINVAL is fine: can be caused by hotunplugged CPUs, or by | |
238 | * cpuset(7). This is why we should always retry if we detect | |
239 | * migration. | |
240 | */ | |
241 | if (ret && errno == EINVAL) { | |
242 | ret = 0; | |
243 | errno = 0; | |
244 | } | |
245 | return ret; | |
c1d2c60b MD |
246 | } |
247 | #else | |
248 | static | |
249 | int set_thread_cpu_affinity(struct call_rcu_data *crdp) | |
250 | { | |
251 | return 0; | |
252 | } | |
253 | #endif | |
254 | ||
03fe58b3 MD |
255 | static void call_rcu_wait(struct call_rcu_data *crdp) |
256 | { | |
257 | /* Read call_rcu list before read futex */ | |
258 | cmm_smp_mb(); | |
259 | if (uatomic_read(&crdp->futex) == -1) | |
260 | futex_async(&crdp->futex, FUTEX_WAIT, -1, | |
261 | NULL, NULL, 0); | |
262 | } | |
263 | ||
264 | static void call_rcu_wake_up(struct call_rcu_data *crdp) | |
265 | { | |
266 | /* Write to call_rcu list before reading/writing futex */ | |
267 | cmm_smp_mb(); | |
a0b7f7ea | 268 | if (caa_unlikely(uatomic_read(&crdp->futex) == -1)) { |
03fe58b3 MD |
269 | uatomic_set(&crdp->futex, 0); |
270 | futex_async(&crdp->futex, FUTEX_WAKE, 1, | |
271 | NULL, NULL, 0); | |
272 | } | |
273 | } | |
274 | ||
b7f721d9 MD |
275 | static void call_rcu_completion_wait(struct call_rcu_completion *completion) |
276 | { | |
277 | /* Read completion barrier count before read futex */ | |
278 | cmm_smp_mb(); | |
279 | if (uatomic_read(&completion->futex) == -1) | |
280 | futex_async(&completion->futex, FUTEX_WAIT, -1, | |
281 | NULL, NULL, 0); | |
282 | } | |
283 | ||
284 | static void call_rcu_completion_wake_up(struct call_rcu_completion *completion) | |
285 | { | |
286 | /* Write to completion barrier count before reading/writing futex */ | |
287 | cmm_smp_mb(); | |
288 | if (caa_unlikely(uatomic_read(&completion->futex) == -1)) { | |
289 | uatomic_set(&completion->futex, 0); | |
290 | futex_async(&completion->futex, FUTEX_WAKE, 1, | |
291 | NULL, NULL, 0); | |
292 | } | |
293 | } | |
294 | ||
b57aee66 PM |
295 | /* This is the code run by each call_rcu thread. */ |
296 | ||
297 | static void *call_rcu_thread(void *arg) | |
298 | { | |
299 | unsigned long cbcount; | |
5161f31e | 300 | struct call_rcu_data *crdp = (struct call_rcu_data *) arg; |
2870aa1e | 301 | int rt = !!(uatomic_read(&crdp->flags) & URCU_CALL_RCU_RT); |
b57aee66 | 302 | |
8e3690db | 303 | if (set_thread_cpu_affinity(crdp)) |
4a6d7378 | 304 | urcu_die(errno); |
c1d2c60b | 305 | |
765f3ead MD |
306 | /* |
307 | * If callbacks take a read-side lock, we need to be registered. | |
308 | */ | |
309 | rcu_register_thread(); | |
310 | ||
bd252a04 | 311 | URCU_TLS(thread_call_rcu_data) = crdp; |
bc94ca9b MD |
312 | if (!rt) { |
313 | uatomic_dec(&crdp->futex); | |
314 | /* Decrement futex before reading call_rcu list */ | |
315 | cmm_smp_mb(); | |
316 | } | |
b57aee66 | 317 | for (;;) { |
5161f31e MD |
318 | struct cds_wfcq_head cbs_tmp_head; |
319 | struct cds_wfcq_tail cbs_tmp_tail; | |
320 | struct cds_wfcq_node *cbs, *cbs_tmp_n; | |
ae25b7e2 | 321 | enum cds_wfcq_ret splice_ret; |
5161f31e | 322 | |
8e3690db MD |
323 | if (set_thread_cpu_affinity(crdp)) |
324 | urcu_die(errno); | |
325 | ||
e85451a1 MD |
326 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) { |
327 | /* | |
328 | * Pause requested. Become quiescent: remove | |
329 | * ourself from all global lists, and don't | |
330 | * process any callback. The callback lists may | |
331 | * still be non-empty though. | |
332 | */ | |
333 | rcu_unregister_thread(); | |
334 | cmm_smp_mb__before_uatomic_or(); | |
335 | uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSED); | |
336 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSE) != 0) | |
109105b7 | 337 | (void) poll(NULL, 0, 1); |
fc236e5e KF |
338 | uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSED); |
339 | cmm_smp_mb__after_uatomic_and(); | |
e85451a1 MD |
340 | rcu_register_thread(); |
341 | } | |
342 | ||
5161f31e | 343 | cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail); |
ae25b7e2 MD |
344 | splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head, |
345 | &cbs_tmp_tail, &crdp->cbs_head, &crdp->cbs_tail); | |
346 | assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK); | |
347 | assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY); | |
348 | if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) { | |
b57aee66 PM |
349 | synchronize_rcu(); |
350 | cbcount = 0; | |
5161f31e MD |
351 | __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head, |
352 | &cbs_tmp_tail, cbs, cbs_tmp_n) { | |
353 | struct rcu_head *rhp; | |
354 | ||
355 | rhp = caa_container_of(cbs, | |
356 | struct rcu_head, next); | |
b57aee66 PM |
357 | rhp->func(rhp); |
358 | cbcount++; | |
5161f31e | 359 | } |
b57aee66 PM |
360 | uatomic_sub(&crdp->qlen, cbcount); |
361 | } | |
bc94ca9b MD |
362 | if (uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOP) |
363 | break; | |
765f3ead | 364 | rcu_thread_offline(); |
bc94ca9b | 365 | if (!rt) { |
5161f31e MD |
366 | if (cds_wfcq_empty(&crdp->cbs_head, |
367 | &crdp->cbs_tail)) { | |
bc94ca9b | 368 | call_rcu_wait(crdp); |
109105b7 | 369 | (void) poll(NULL, 0, 10); |
bc94ca9b | 370 | uatomic_dec(&crdp->futex); |
c768e45e | 371 | /* |
bc94ca9b MD |
372 | * Decrement futex before reading |
373 | * call_rcu list. | |
c768e45e MD |
374 | */ |
375 | cmm_smp_mb(); | |
ccbac24d | 376 | } else { |
109105b7 | 377 | (void) poll(NULL, 0, 10); |
c768e45e | 378 | } |
bc94ca9b | 379 | } else { |
109105b7 | 380 | (void) poll(NULL, 0, 10); |
b57aee66 | 381 | } |
765f3ead | 382 | rcu_thread_online(); |
bc94ca9b MD |
383 | } |
384 | if (!rt) { | |
385 | /* | |
386 | * Read call_rcu list before write futex. | |
387 | */ | |
388 | cmm_smp_mb(); | |
389 | uatomic_set(&crdp->futex, 0); | |
b57aee66 | 390 | } |
2870aa1e | 391 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOPPED); |
765f3ead | 392 | rcu_unregister_thread(); |
7106ddf8 | 393 | return NULL; |
b57aee66 PM |
394 | } |
395 | ||
396 | /* | |
397 | * Create both a call_rcu thread and the corresponding call_rcu_data | |
3c24913f PM |
398 | * structure, linking the structure in as specified. Caller must hold |
399 | * call_rcu_mutex. | |
b57aee66 PM |
400 | */ |
401 | ||
3c24913f | 402 | static void call_rcu_data_init(struct call_rcu_data **crdpp, |
c1d2c60b MD |
403 | unsigned long flags, |
404 | int cpu_affinity) | |
b57aee66 PM |
405 | { |
406 | struct call_rcu_data *crdp; | |
4a6d7378 | 407 | int ret; |
b57aee66 PM |
408 | |
409 | crdp = malloc(sizeof(*crdp)); | |
4a6d7378 MD |
410 | if (crdp == NULL) |
411 | urcu_die(errno); | |
b57aee66 | 412 | memset(crdp, '\0', sizeof(*crdp)); |
5161f31e | 413 | cds_wfcq_init(&crdp->cbs_head, &crdp->cbs_tail); |
b57aee66 | 414 | crdp->qlen = 0; |
263e3cf9 MD |
415 | crdp->futex = 0; |
416 | crdp->flags = flags; | |
3c24913f | 417 | cds_list_add(&crdp->list, &call_rcu_data_list); |
c1d2c60b | 418 | crdp->cpu_affinity = cpu_affinity; |
8e3690db | 419 | crdp->gp_count = 0; |
b57aee66 PM |
420 | cmm_smp_mb(); /* Structure initialized before pointer is planted. */ |
421 | *crdpp = crdp; | |
4a6d7378 MD |
422 | ret = pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp); |
423 | if (ret) | |
424 | urcu_die(ret); | |
b57aee66 PM |
425 | } |
426 | ||
427 | /* | |
428 | * Return a pointer to the call_rcu_data structure for the specified | |
429 | * CPU, returning NULL if there is none. We cannot automatically | |
430 | * created it because the platform we are running on might not define | |
63b495d8 | 431 | * urcu_sched_getcpu(). |
618b2595 MD |
432 | * |
433 | * The call to this function and use of the returned call_rcu_data | |
434 | * should be protected by RCU read-side lock. | |
b57aee66 PM |
435 | */ |
436 | ||
437 | struct call_rcu_data *get_cpu_call_rcu_data(int cpu) | |
438 | { | |
439 | static int warned = 0; | |
618b2595 | 440 | struct call_rcu_data **pcpu_crdp; |
b57aee66 | 441 | |
618b2595 MD |
442 | pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data); |
443 | if (pcpu_crdp == NULL) | |
b57aee66 PM |
444 | return NULL; |
445 | if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) { | |
446 | fprintf(stderr, "[error] liburcu: get CPU # out of range\n"); | |
447 | warned = 1; | |
448 | } | |
449 | if (cpu < 0 || maxcpus <= cpu) | |
450 | return NULL; | |
618b2595 | 451 | return rcu_dereference(pcpu_crdp[cpu]); |
b57aee66 PM |
452 | } |
453 | ||
454 | /* | |
455 | * Return the tid corresponding to the call_rcu thread whose | |
456 | * call_rcu_data structure is specified. | |
457 | */ | |
458 | ||
459 | pthread_t get_call_rcu_thread(struct call_rcu_data *crdp) | |
460 | { | |
461 | return crdp->tid; | |
462 | } | |
463 | ||
464 | /* | |
465 | * Create a call_rcu_data structure (with thread) and return a pointer. | |
466 | */ | |
467 | ||
c1d2c60b MD |
468 | static struct call_rcu_data *__create_call_rcu_data(unsigned long flags, |
469 | int cpu_affinity) | |
b57aee66 PM |
470 | { |
471 | struct call_rcu_data *crdp; | |
472 | ||
c1d2c60b | 473 | call_rcu_data_init(&crdp, flags, cpu_affinity); |
b57aee66 PM |
474 | return crdp; |
475 | } | |
476 | ||
c1d2c60b MD |
477 | struct call_rcu_data *create_call_rcu_data(unsigned long flags, |
478 | int cpu_affinity) | |
3c24913f PM |
479 | { |
480 | struct call_rcu_data *crdp; | |
481 | ||
482 | call_rcu_lock(&call_rcu_mutex); | |
c1d2c60b | 483 | crdp = __create_call_rcu_data(flags, cpu_affinity); |
3c24913f PM |
484 | call_rcu_unlock(&call_rcu_mutex); |
485 | return crdp; | |
486 | } | |
487 | ||
b57aee66 PM |
488 | /* |
489 | * Set the specified CPU to use the specified call_rcu_data structure. | |
7106ddf8 PM |
490 | * |
491 | * Use NULL to remove a CPU's call_rcu_data structure, but it is | |
492 | * the caller's responsibility to dispose of the removed structure. | |
493 | * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure | |
494 | * (prior to NULLing it out, of course). | |
f9da0936 MD |
495 | * |
496 | * The caller must wait for a grace-period to pass between return from | |
497 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the | |
498 | * previous call rcu data as argument. | |
b57aee66 PM |
499 | */ |
500 | ||
501 | int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp) | |
502 | { | |
dcfc8165 | 503 | static int warned = 0; |
b57aee66 PM |
504 | |
505 | call_rcu_lock(&call_rcu_mutex); | |
f3776786 | 506 | alloc_cpu_call_rcu_data(); |
b57aee66 PM |
507 | if (cpu < 0 || maxcpus <= cpu) { |
508 | if (!warned) { | |
509 | fprintf(stderr, "[error] liburcu: set CPU # out of range\n"); | |
510 | warned = 1; | |
511 | } | |
512 | call_rcu_unlock(&call_rcu_mutex); | |
513 | errno = EINVAL; | |
514 | return -EINVAL; | |
515 | } | |
53a55535 | 516 | |
b57aee66 | 517 | if (per_cpu_call_rcu_data == NULL) { |
3670fef2 | 518 | call_rcu_unlock(&call_rcu_mutex); |
b57aee66 PM |
519 | errno = ENOMEM; |
520 | return -ENOMEM; | |
521 | } | |
53a55535 LJ |
522 | |
523 | if (per_cpu_call_rcu_data[cpu] != NULL && crdp != NULL) { | |
524 | call_rcu_unlock(&call_rcu_mutex); | |
525 | errno = EEXIST; | |
526 | return -EEXIST; | |
527 | } | |
528 | ||
618b2595 | 529 | rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp); |
3670fef2 | 530 | call_rcu_unlock(&call_rcu_mutex); |
b57aee66 PM |
531 | return 0; |
532 | } | |
533 | ||
534 | /* | |
535 | * Return a pointer to the default call_rcu_data structure, creating | |
536 | * one if need be. Because we never free call_rcu_data structures, | |
537 | * we don't need to be in an RCU read-side critical section. | |
538 | */ | |
539 | ||
540 | struct call_rcu_data *get_default_call_rcu_data(void) | |
541 | { | |
542 | if (default_call_rcu_data != NULL) | |
543 | return rcu_dereference(default_call_rcu_data); | |
544 | call_rcu_lock(&call_rcu_mutex); | |
545 | if (default_call_rcu_data != NULL) { | |
546 | call_rcu_unlock(&call_rcu_mutex); | |
547 | return default_call_rcu_data; | |
548 | } | |
c1d2c60b | 549 | call_rcu_data_init(&default_call_rcu_data, 0, -1); |
b57aee66 PM |
550 | call_rcu_unlock(&call_rcu_mutex); |
551 | return default_call_rcu_data; | |
552 | } | |
553 | ||
554 | /* | |
555 | * Return the call_rcu_data structure that applies to the currently | |
556 | * running thread. Any call_rcu_data structure assigned specifically | |
557 | * to this thread has first priority, followed by any call_rcu_data | |
558 | * structure assigned to the CPU on which the thread is running, | |
559 | * followed by the default call_rcu_data structure. If there is not | |
560 | * yet a default call_rcu_data structure, one will be created. | |
618b2595 MD |
561 | * |
562 | * Calls to this function and use of the returned call_rcu_data should | |
563 | * be protected by RCU read-side lock. | |
b57aee66 PM |
564 | */ |
565 | struct call_rcu_data *get_call_rcu_data(void) | |
566 | { | |
9744f3bb | 567 | struct call_rcu_data *crd; |
b57aee66 | 568 | |
bd252a04 MD |
569 | if (URCU_TLS(thread_call_rcu_data) != NULL) |
570 | return URCU_TLS(thread_call_rcu_data); | |
9744f3bb LJ |
571 | |
572 | if (maxcpus > 0) { | |
63b495d8 | 573 | crd = get_cpu_call_rcu_data(urcu_sched_getcpu()); |
9744f3bb LJ |
574 | if (crd) |
575 | return crd; | |
b57aee66 | 576 | } |
9744f3bb | 577 | |
b57aee66 PM |
578 | return get_default_call_rcu_data(); |
579 | } | |
580 | ||
581 | /* | |
582 | * Return a pointer to this task's call_rcu_data if there is one. | |
583 | */ | |
584 | ||
585 | struct call_rcu_data *get_thread_call_rcu_data(void) | |
586 | { | |
bd252a04 | 587 | return URCU_TLS(thread_call_rcu_data); |
b57aee66 PM |
588 | } |
589 | ||
590 | /* | |
591 | * Set this task's call_rcu_data structure as specified, regardless | |
592 | * of whether or not this task already had one. (This allows switching | |
593 | * to and from real-time call_rcu threads, for example.) | |
7106ddf8 PM |
594 | * |
595 | * Use NULL to remove a thread's call_rcu_data structure, but it is | |
596 | * the caller's responsibility to dispose of the removed structure. | |
597 | * Use get_thread_call_rcu_data() to obtain a pointer to the old structure | |
598 | * (prior to NULLing it out, of course). | |
b57aee66 PM |
599 | */ |
600 | ||
601 | void set_thread_call_rcu_data(struct call_rcu_data *crdp) | |
602 | { | |
bd252a04 | 603 | URCU_TLS(thread_call_rcu_data) = crdp; |
b57aee66 PM |
604 | } |
605 | ||
606 | /* | |
607 | * Create a separate call_rcu thread for each CPU. This does not | |
608 | * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data() | |
0938c541 MD |
609 | * function if you want that behavior. Should be paired with |
610 | * free_all_cpu_call_rcu_data() to teardown these call_rcu worker | |
611 | * threads. | |
b57aee66 PM |
612 | */ |
613 | ||
614 | int create_all_cpu_call_rcu_data(unsigned long flags) | |
615 | { | |
616 | int i; | |
617 | struct call_rcu_data *crdp; | |
618 | int ret; | |
619 | ||
620 | call_rcu_lock(&call_rcu_mutex); | |
621 | alloc_cpu_call_rcu_data(); | |
622 | call_rcu_unlock(&call_rcu_mutex); | |
623 | if (maxcpus <= 0) { | |
624 | errno = EINVAL; | |
625 | return -EINVAL; | |
626 | } | |
627 | if (per_cpu_call_rcu_data == NULL) { | |
628 | errno = ENOMEM; | |
629 | return -ENOMEM; | |
630 | } | |
631 | for (i = 0; i < maxcpus; i++) { | |
632 | call_rcu_lock(&call_rcu_mutex); | |
633 | if (get_cpu_call_rcu_data(i)) { | |
634 | call_rcu_unlock(&call_rcu_mutex); | |
635 | continue; | |
636 | } | |
c1d2c60b | 637 | crdp = __create_call_rcu_data(flags, i); |
b57aee66 PM |
638 | if (crdp == NULL) { |
639 | call_rcu_unlock(&call_rcu_mutex); | |
640 | errno = ENOMEM; | |
641 | return -ENOMEM; | |
642 | } | |
643 | call_rcu_unlock(&call_rcu_mutex); | |
644 | if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) { | |
356c8794 LJ |
645 | call_rcu_data_free(crdp); |
646 | ||
647 | /* it has been created by other thread */ | |
648 | if (ret == -EEXIST) | |
649 | continue; | |
650 | ||
651 | return ret; | |
b57aee66 PM |
652 | } |
653 | } | |
654 | return 0; | |
655 | } | |
656 | ||
7106ddf8 PM |
657 | /* |
658 | * Wake up the call_rcu thread corresponding to the specified | |
659 | * call_rcu_data structure. | |
660 | */ | |
661 | static void wake_call_rcu_thread(struct call_rcu_data *crdp) | |
662 | { | |
263e3cf9 MD |
663 | if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) |
664 | call_rcu_wake_up(crdp); | |
7106ddf8 PM |
665 | } |
666 | ||
b7f721d9 MD |
667 | static void _call_rcu(struct rcu_head *head, |
668 | void (*func)(struct rcu_head *head), | |
669 | struct call_rcu_data *crdp) | |
670 | { | |
671 | cds_wfcq_node_init(&head->next); | |
672 | head->func = func; | |
673 | cds_wfcq_enqueue(&crdp->cbs_head, &crdp->cbs_tail, &head->next); | |
674 | uatomic_inc(&crdp->qlen); | |
675 | wake_call_rcu_thread(crdp); | |
676 | } | |
677 | ||
b57aee66 PM |
678 | /* |
679 | * Schedule a function to be invoked after a following grace period. | |
680 | * This is the only function that must be called -- the others are | |
681 | * only present to allow applications to tune their use of RCU for | |
682 | * maximum performance. | |
683 | * | |
684 | * Note that unless a call_rcu thread has not already been created, | |
685 | * the first invocation of call_rcu() will create one. So, if you | |
686 | * need the first invocation of call_rcu() to be fast, make sure | |
687 | * to create a call_rcu thread first. One way to accomplish this is | |
688 | * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data(). | |
618b2595 MD |
689 | * |
690 | * call_rcu must be called by registered RCU read-side threads. | |
b57aee66 | 691 | */ |
b57aee66 PM |
692 | void call_rcu(struct rcu_head *head, |
693 | void (*func)(struct rcu_head *head)) | |
694 | { | |
695 | struct call_rcu_data *crdp; | |
696 | ||
618b2595 | 697 | /* Holding rcu read-side lock across use of per-cpu crdp */ |
ffb4aaa7 | 698 | _rcu_read_lock(); |
b57aee66 | 699 | crdp = get_call_rcu_data(); |
b7f721d9 | 700 | _call_rcu(head, func, crdp); |
ffb4aaa7 | 701 | _rcu_read_unlock(); |
7106ddf8 PM |
702 | } |
703 | ||
704 | /* | |
705 | * Free up the specified call_rcu_data structure, terminating the | |
706 | * associated call_rcu thread. The caller must have previously | |
707 | * removed the call_rcu_data structure from per-thread or per-CPU | |
708 | * usage. For example, set_cpu_call_rcu_data(cpu, NULL) for per-CPU | |
709 | * call_rcu_data structures or set_thread_call_rcu_data(NULL) for | |
710 | * per-thread call_rcu_data structures. | |
711 | * | |
712 | * We silently refuse to free up the default call_rcu_data structure | |
713 | * because that is where we put any leftover callbacks. Note that | |
714 | * the possibility of self-spawning callbacks makes it impossible | |
715 | * to execute all the callbacks in finite time without putting any | |
716 | * newly spawned callbacks somewhere else. The "somewhere else" of | |
717 | * last resort is the default call_rcu_data structure. | |
718 | * | |
719 | * We also silently refuse to free NULL pointers. This simplifies | |
720 | * the calling code. | |
f9da0936 MD |
721 | * |
722 | * The caller must wait for a grace-period to pass between return from | |
723 | * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the | |
724 | * previous call rcu data as argument. | |
03e5118f MD |
725 | * |
726 | * Note: introducing __cds_wfcq_splice_blocking() in this function fixed | |
727 | * a list corruption bug in the 0.7.x series. The equivalent fix | |
728 | * appeared in 0.6.8 for the stable-0.6 branch. | |
7106ddf8 PM |
729 | */ |
730 | void call_rcu_data_free(struct call_rcu_data *crdp) | |
731 | { | |
7106ddf8 PM |
732 | if (crdp == NULL || crdp == default_call_rcu_data) { |
733 | return; | |
734 | } | |
2870aa1e PB |
735 | if ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) { |
736 | uatomic_or(&crdp->flags, URCU_CALL_RCU_STOP); | |
7106ddf8 | 737 | wake_call_rcu_thread(crdp); |
2870aa1e | 738 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_STOPPED) == 0) |
109105b7 | 739 | (void) poll(NULL, 0, 1); |
7106ddf8 | 740 | } |
5161f31e | 741 | if (!cds_wfcq_empty(&crdp->cbs_head, &crdp->cbs_tail)) { |
698d0778 MD |
742 | /* Create default call rcu data if need be */ |
743 | (void) get_default_call_rcu_data(); | |
5161f31e MD |
744 | __cds_wfcq_splice_blocking(&default_call_rcu_data->cbs_head, |
745 | &default_call_rcu_data->cbs_tail, | |
746 | &crdp->cbs_head, &crdp->cbs_tail); | |
7106ddf8 PM |
747 | uatomic_add(&default_call_rcu_data->qlen, |
748 | uatomic_read(&crdp->qlen)); | |
1e92aa15 | 749 | wake_call_rcu_thread(default_call_rcu_data); |
7106ddf8 | 750 | } |
59dc9e9d | 751 | |
b75dffe6 | 752 | call_rcu_lock(&call_rcu_mutex); |
59dc9e9d | 753 | cds_list_del(&crdp->list); |
b75dffe6 LJ |
754 | call_rcu_unlock(&call_rcu_mutex); |
755 | ||
59dc9e9d | 756 | free(crdp); |
7106ddf8 PM |
757 | } |
758 | ||
759 | /* | |
760 | * Clean up all the per-CPU call_rcu threads. | |
761 | */ | |
762 | void free_all_cpu_call_rcu_data(void) | |
763 | { | |
764 | int cpu; | |
618b2595 MD |
765 | struct call_rcu_data **crdp; |
766 | static int warned = 0; | |
7106ddf8 PM |
767 | |
768 | if (maxcpus <= 0) | |
769 | return; | |
618b2595 MD |
770 | |
771 | crdp = malloc(sizeof(*crdp) * maxcpus); | |
772 | if (!crdp) { | |
773 | if (!warned) { | |
774 | fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); | |
775 | } | |
776 | warned = 1; | |
d31150b4 | 777 | return; |
618b2595 MD |
778 | } |
779 | ||
7106ddf8 | 780 | for (cpu = 0; cpu < maxcpus; cpu++) { |
618b2595 MD |
781 | crdp[cpu] = get_cpu_call_rcu_data(cpu); |
782 | if (crdp[cpu] == NULL) | |
7106ddf8 PM |
783 | continue; |
784 | set_cpu_call_rcu_data(cpu, NULL); | |
7106ddf8 | 785 | } |
618b2595 MD |
786 | /* |
787 | * Wait for call_rcu sites acting as RCU readers of the | |
788 | * call_rcu_data to become quiescent. | |
789 | */ | |
790 | synchronize_rcu(); | |
791 | for (cpu = 0; cpu < maxcpus; cpu++) { | |
792 | if (crdp[cpu] == NULL) | |
793 | continue; | |
794 | call_rcu_data_free(crdp[cpu]); | |
795 | } | |
796 | free(crdp); | |
7106ddf8 PM |
797 | } |
798 | ||
81dd9134 KF |
799 | static |
800 | void free_completion(struct urcu_ref *ref) | |
801 | { | |
802 | struct call_rcu_completion *completion; | |
803 | ||
804 | completion = caa_container_of(ref, struct call_rcu_completion, ref); | |
805 | free(completion); | |
806 | } | |
807 | ||
b7f721d9 MD |
808 | static |
809 | void _rcu_barrier_complete(struct rcu_head *head) | |
810 | { | |
811 | struct call_rcu_completion_work *work; | |
812 | struct call_rcu_completion *completion; | |
813 | ||
814 | work = caa_container_of(head, struct call_rcu_completion_work, head); | |
815 | completion = work->completion; | |
81dd9134 KF |
816 | if (!uatomic_sub_return(&completion->barrier_count, 1)) |
817 | call_rcu_completion_wake_up(completion); | |
818 | urcu_ref_put(&completion->ref, free_completion); | |
b7f721d9 MD |
819 | free(work); |
820 | } | |
821 | ||
822 | /* | |
823 | * Wait for all in-flight call_rcu callbacks to complete execution. | |
824 | */ | |
825 | void rcu_barrier(void) | |
826 | { | |
827 | struct call_rcu_data *crdp; | |
81dd9134 | 828 | struct call_rcu_completion *completion; |
63f0fc6d | 829 | int count = 0; |
b7f721d9 MD |
830 | int was_online; |
831 | ||
832 | /* Put in offline state in QSBR. */ | |
ffb4aaa7 | 833 | was_online = _rcu_read_ongoing(); |
b7f721d9 MD |
834 | if (was_online) |
835 | rcu_thread_offline(); | |
836 | /* | |
837 | * Calling a rcu_barrier() within a RCU read-side critical | |
838 | * section is an error. | |
839 | */ | |
ffb4aaa7 | 840 | if (_rcu_read_ongoing()) { |
b7f721d9 MD |
841 | static int warned = 0; |
842 | ||
843 | if (!warned) { | |
844 | fprintf(stderr, "[error] liburcu: rcu_barrier() called from within RCU read-side critical section.\n"); | |
845 | } | |
846 | warned = 1; | |
847 | goto online; | |
848 | } | |
849 | ||
81dd9134 KF |
850 | completion = calloc(sizeof(*completion), 1); |
851 | if (!completion) | |
852 | urcu_die(errno); | |
853 | ||
b7f721d9 MD |
854 | call_rcu_lock(&call_rcu_mutex); |
855 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) | |
856 | count++; | |
857 | ||
81dd9134 KF |
858 | /* Referenced by rcu_barrier() and each call_rcu thread. */ |
859 | urcu_ref_set(&completion->ref, count + 1); | |
860 | completion->barrier_count = count; | |
b7f721d9 MD |
861 | |
862 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { | |
863 | struct call_rcu_completion_work *work; | |
864 | ||
865 | work = calloc(sizeof(*work), 1); | |
63f0fc6d MD |
866 | if (!work) |
867 | urcu_die(errno); | |
81dd9134 | 868 | work->completion = completion; |
b7f721d9 | 869 | _call_rcu(&work->head, _rcu_barrier_complete, crdp); |
b7f721d9 MD |
870 | } |
871 | call_rcu_unlock(&call_rcu_mutex); | |
872 | ||
b7f721d9 MD |
873 | /* Wait for them */ |
874 | for (;;) { | |
81dd9134 | 875 | uatomic_dec(&completion->futex); |
b7f721d9 MD |
876 | /* Decrement futex before reading barrier_count */ |
877 | cmm_smp_mb(); | |
81dd9134 | 878 | if (!uatomic_read(&completion->barrier_count)) |
b7f721d9 | 879 | break; |
81dd9134 | 880 | call_rcu_completion_wait(completion); |
b7f721d9 | 881 | } |
81dd9134 KF |
882 | |
883 | urcu_ref_put(&completion->ref, free_completion); | |
884 | ||
b7f721d9 MD |
885 | online: |
886 | if (was_online) | |
887 | rcu_thread_online(); | |
888 | } | |
889 | ||
81ad2e19 PM |
890 | /* |
891 | * Acquire the call_rcu_mutex in order to ensure that the child sees | |
e85451a1 MD |
892 | * all of the call_rcu() data structures in a consistent state. Ensure |
893 | * that all call_rcu threads are in a quiescent state across fork. | |
81ad2e19 PM |
894 | * Suitable for pthread_atfork() and friends. |
895 | */ | |
896 | void call_rcu_before_fork(void) | |
897 | { | |
e85451a1 MD |
898 | struct call_rcu_data *crdp; |
899 | ||
81ad2e19 | 900 | call_rcu_lock(&call_rcu_mutex); |
e85451a1 MD |
901 | |
902 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { | |
903 | uatomic_or(&crdp->flags, URCU_CALL_RCU_PAUSE); | |
904 | cmm_smp_mb__after_uatomic_or(); | |
905 | wake_call_rcu_thread(crdp); | |
906 | } | |
907 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { | |
908 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) == 0) | |
109105b7 | 909 | (void) poll(NULL, 0, 1); |
e85451a1 | 910 | } |
81ad2e19 PM |
911 | } |
912 | ||
913 | /* | |
914 | * Clean up call_rcu data structures in the parent of a successful fork() | |
915 | * that is not followed by exec() in the child. Suitable for | |
916 | * pthread_atfork() and friends. | |
917 | */ | |
918 | void call_rcu_after_fork_parent(void) | |
919 | { | |
e85451a1 MD |
920 | struct call_rcu_data *crdp; |
921 | ||
922 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) | |
923 | uatomic_and(&crdp->flags, ~URCU_CALL_RCU_PAUSE); | |
fc236e5e KF |
924 | cds_list_for_each_entry(crdp, &call_rcu_data_list, list) { |
925 | while ((uatomic_read(&crdp->flags) & URCU_CALL_RCU_PAUSED) != 0) | |
109105b7 | 926 | (void) poll(NULL, 0, 1); |
fc236e5e | 927 | } |
81ad2e19 PM |
928 | call_rcu_unlock(&call_rcu_mutex); |
929 | } | |
930 | ||
7106ddf8 PM |
931 | /* |
932 | * Clean up call_rcu data structures in the child of a successful fork() | |
81ad2e19 PM |
933 | * that is not followed by exec(). Suitable for pthread_atfork() and |
934 | * friends. | |
7106ddf8 PM |
935 | */ |
936 | void call_rcu_after_fork_child(void) | |
937 | { | |
077ff173 | 938 | struct call_rcu_data *crdp, *next; |
7106ddf8 | 939 | |
81ad2e19 PM |
940 | /* Release the mutex. */ |
941 | call_rcu_unlock(&call_rcu_mutex); | |
942 | ||
ad1b9909 LJ |
943 | /* Do nothing when call_rcu() has not been used */ |
944 | if (cds_list_empty(&call_rcu_data_list)) | |
945 | return; | |
946 | ||
7106ddf8 PM |
947 | /* |
948 | * Allocate a new default call_rcu_data structure in order | |
949 | * to get a working call_rcu thread to go with it. | |
950 | */ | |
951 | default_call_rcu_data = NULL; | |
952 | (void)get_default_call_rcu_data(); | |
953 | ||
60af049d LJ |
954 | /* Cleanup call_rcu_data pointers before use */ |
955 | maxcpus_reset(); | |
956 | free(per_cpu_call_rcu_data); | |
618b2595 | 957 | rcu_set_pointer(&per_cpu_call_rcu_data, NULL); |
bd252a04 | 958 | URCU_TLS(thread_call_rcu_data) = NULL; |
60af049d | 959 | |
e85451a1 MD |
960 | /* |
961 | * Dispose of all of the rest of the call_rcu_data structures. | |
962 | * Leftover call_rcu callbacks will be merged into the new | |
963 | * default call_rcu thread queue. | |
964 | */ | |
077ff173 | 965 | cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) { |
7106ddf8 | 966 | if (crdp == default_call_rcu_data) |
077ff173 | 967 | continue; |
2870aa1e | 968 | uatomic_set(&crdp->flags, URCU_CALL_RCU_STOPPED); |
7106ddf8 | 969 | call_rcu_data_free(crdp); |
b57aee66 PM |
970 | } |
971 | } |