Commit | Line | Data |
---|---|---|
b257a10b MD |
1 | /* |
2 | * urcu.c | |
3 | * | |
4 | * Userspace RCU library | |
5 | * | |
6982d6d7 | 6 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
af02d47e | 7 | * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. |
b257a10b | 8 | * |
af02d47e MD |
9 | * This library is free software; you can redistribute it and/or |
10 | * modify it under the terms of the GNU Lesser General Public | |
11 | * License as published by the Free Software Foundation; either | |
12 | * version 2.1 of the License, or (at your option) any later version. | |
13 | * | |
14 | * This library is distributed in the hope that it will be useful, | |
15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | * Lesser General Public License for more details. | |
18 | * | |
19 | * You should have received a copy of the GNU Lesser General Public | |
20 | * License along with this library; if not, write to the Free Software | |
21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
54843abc PM |
22 | * |
23 | * IBM's contributions to this file may be relicensed under LGPLv2 or later. | |
b257a10b MD |
24 | */ |
25 | ||
fdf01eed | 26 | #define _BSD_SOURCE |
c1d2c60b | 27 | #define _GNU_SOURCE |
71c811bf | 28 | #define _LGPL_SOURCE |
27b012e2 MD |
29 | #include <stdio.h> |
30 | #include <pthread.h> | |
31 | #include <signal.h> | |
32 | #include <assert.h> | |
f69f195a | 33 | #include <stdlib.h> |
6d841bc2 | 34 | #include <stdint.h> |
f69f195a | 35 | #include <string.h> |
09a9f986 | 36 | #include <errno.h> |
e8043c1b | 37 | #include <poll.h> |
27b012e2 | 38 | |
d73fb81f | 39 | #include "urcu/wfcqueue.h" |
57760d44 | 40 | #include "urcu/map/urcu.h" |
af7c2dbe | 41 | #include "urcu/static/urcu.h" |
618b2595 | 42 | #include "urcu-pointer.h" |
bd252a04 | 43 | #include "urcu/tls-compat.h" |
71c811bf | 44 | |
4a6d7378 | 45 | #include "urcu-die.h" |
5bffdd5d | 46 | #include "urcu-wait.h" |
4a6d7378 | 47 | |
121a5d44 | 48 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
71c811bf | 49 | #undef _LGPL_SOURCE |
27b012e2 | 50 | #include "urcu.h" |
71c811bf | 51 | #define _LGPL_SOURCE |
27b012e2 | 52 | |
3a71751e PB |
53 | /* |
54 | * If a reader is really non-cooperative and refuses to commit its | |
55 | * rcu_active_readers count to memory (there is no barrier in the reader | |
56 | * per-se), kick it after a few loops waiting for it. | |
57 | */ | |
58 | #define KICK_READER_LOOPS 10000 | |
59 | ||
60 | /* | |
61 | * Active attempts to check for reader Q.S. before calling futex(). | |
62 | */ | |
63 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
64 | ||
553b7eb9 MD |
65 | /* |
66 | * RCU_MEMBARRIER is only possibly available on Linux. | |
67 | */ | |
68 | #if defined(RCU_MEMBARRIER) && defined(__linux__) | |
9ba261bd | 69 | #include <urcu/syscall-compat.h> |
553b7eb9 MD |
70 | #endif |
71 | ||
72 | /* If the headers do not support SYS_membarrier, fall back on RCU_MB */ | |
73 | #ifdef SYS_membarrier | |
74 | # define membarrier(...) syscall(SYS_membarrier, __VA_ARGS__) | |
75 | #else | |
76 | # define membarrier(...) -ENOSYS | |
77 | #endif | |
78 | ||
79 | #define MEMBARRIER_EXPEDITED (1 << 0) | |
80 | #define MEMBARRIER_DELAYED (1 << 1) | |
81 | #define MEMBARRIER_QUERY (1 << 16) | |
82 | ||
fdf01eed | 83 | #ifdef RCU_MEMBARRIER |
834a45ba | 84 | static int init_done; |
1de4df4b | 85 | int rcu_has_sys_membarrier; |
834a45ba | 86 | |
02be5561 | 87 | void __attribute__((constructor)) rcu_init(void); |
fdf01eed MD |
88 | #endif |
89 | ||
90 | #ifdef RCU_MB | |
02be5561 | 91 | void rcu_init(void) |
e90a6e9c MD |
92 | { |
93 | } | |
94 | #endif | |
8a5fb4c9 | 95 | |
fdf01eed MD |
96 | #ifdef RCU_SIGNAL |
97 | static int init_done; | |
98 | ||
99 | void __attribute__((constructor)) rcu_init(void); | |
100 | void __attribute__((destructor)) rcu_exit(void); | |
101 | #endif | |
102 | ||
6abb4bd5 | 103 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
4de0cd31 | 104 | struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT }; |
27b012e2 | 105 | |
b0d5e790 MD |
106 | /* |
107 | * Written to only by each individual reader. Read by both the reader and the | |
108 | * writers. | |
109 | */ | |
bd252a04 | 110 | DEFINE_URCU_TLS(struct rcu_reader, rcu_reader); |
27b012e2 | 111 | |
cf380c2f | 112 | #ifdef DEBUG_YIELD |
1de4df4b MD |
113 | unsigned int rcu_yield_active; |
114 | DEFINE_URCU_TLS(unsigned int, rcu_rand_yield); | |
cf380c2f MD |
115 | #endif |
116 | ||
16aa9ee8 | 117 | static CDS_LIST_HEAD(registry); |
27b012e2 | 118 | |
5bffdd5d MD |
119 | /* |
120 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
121 | * struct gp_waiters_thread objects. | |
122 | */ | |
123 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
124 | ||
6abb4bd5 | 125 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
126 | { |
127 | int ret; | |
09a9f986 PM |
128 | |
129 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 130 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
131 | if (ret) |
132 | urcu_die(ret); | |
09a9f986 | 133 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 134 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
135 | if (ret != EBUSY && ret != EINTR) |
136 | urcu_die(ret); | |
bd252a04 | 137 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 138 | cmm_smp_mb(); |
bd252a04 | 139 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 140 | cmm_smp_mb(); |
09a9f986 PM |
141 | } |
142 | poll(NULL,0,10); | |
143 | } | |
144 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
145 | } |
146 | ||
6abb4bd5 | 147 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
148 | { |
149 | int ret; | |
150 | ||
6abb4bd5 | 151 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
152 | if (ret) |
153 | urcu_die(ret); | |
41718ff9 MD |
154 | } |
155 | ||
fdf01eed | 156 | #ifdef RCU_MEMBARRIER |
25cc6d18 | 157 | static void smp_mb_master(int group) |
fdf01eed | 158 | { |
1de4df4b | 159 | if (caa_likely(rcu_has_sys_membarrier)) |
553b7eb9 | 160 | (void) membarrier(MEMBARRIER_EXPEDITED); |
fdf01eed | 161 | else |
5481ddb3 | 162 | cmm_smp_mb(); |
fdf01eed MD |
163 | } |
164 | #endif | |
165 | ||
02be5561 | 166 | #ifdef RCU_MB |
25cc6d18 | 167 | static void smp_mb_master(int group) |
40e140c9 | 168 | { |
5481ddb3 | 169 | cmm_smp_mb(); |
40e140c9 | 170 | } |
fdf01eed MD |
171 | #endif |
172 | ||
173 | #ifdef RCU_SIGNAL | |
78ff9419 | 174 | static void force_mb_all_readers(void) |
27b012e2 | 175 | { |
02be5561 | 176 | struct rcu_reader *index; |
e3b0cef0 | 177 | |
27b012e2 | 178 | /* |
5481ddb3 | 179 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
180 | * compiler barriers around rcu read lock as real memory barriers. |
181 | */ | |
16aa9ee8 | 182 | if (cds_list_empty(®istry)) |
27b012e2 | 183 | return; |
3a86deba | 184 | /* |
5481ddb3 | 185 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 186 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 187 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 188 | * cache flush is enforced. |
3a86deba | 189 | */ |
16aa9ee8 | 190 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 191 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 192 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 193 | } |
27b012e2 MD |
194 | /* |
195 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
196 | * |
197 | * Note that the pthread_kill() will never be executed on systems | |
198 | * that correctly deliver signals in a timely manner. However, it | |
199 | * is not uncommon for kernels to have bugs that can result in | |
200 | * lost or unduly delayed signals. | |
201 | * | |
202 | * If you are seeing the below pthread_kill() executing much at | |
203 | * all, we suggest testing the underlying kernel and filing the | |
204 | * relevant bug report. For Linux kernels, we recommend getting | |
205 | * the Linux Test Project (LTP). | |
27b012e2 | 206 | */ |
16aa9ee8 | 207 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 208 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 209 | pthread_kill(index->tid, SIGRCU); |
09a9f986 PM |
210 | poll(NULL, 0, 1); |
211 | } | |
212 | } | |
5481ddb3 | 213 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 214 | } |
9d7e3f89 | 215 | |
25cc6d18 | 216 | static void smp_mb_master(int group) |
9d7e3f89 MD |
217 | { |
218 | force_mb_all_readers(); | |
219 | } | |
fdf01eed | 220 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 221 | |
bc6c15bb MD |
222 | /* |
223 | * synchronize_rcu() waiting. Single thread. | |
224 | */ | |
cfe78e25 | 225 | static void wait_gp(void) |
bc6c15bb | 226 | { |
cfe78e25 | 227 | /* Read reader_gp before read futex */ |
25cc6d18 | 228 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e LJ |
229 | if (uatomic_read(&rcu_gp.futex) == -1) |
230 | futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, | |
cfe78e25 | 231 | NULL, NULL, 0); |
bc6c15bb MD |
232 | } |
233 | ||
fd189fa5 MD |
234 | static void wait_for_readers(struct cds_list_head *input_readers, |
235 | struct cds_list_head *cur_snap_readers, | |
236 | struct cds_list_head *qsreaders) | |
27b012e2 | 237 | { |
cfe78e25 | 238 | int wait_loops = 0; |
02be5561 | 239 | struct rcu_reader *index, *tmp; |
27b012e2 | 240 | |
40e140c9 | 241 | /* |
c9488684 MD |
242 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
243 | * indicate quiescence (not nested), or observe the current | |
ed1b099e | 244 | * rcu_gp.ctr value. |
27b012e2 | 245 | */ |
cfe78e25 MD |
246 | for (;;) { |
247 | wait_loops++; | |
248 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { | |
ed1b099e | 249 | uatomic_dec(&rcu_gp.futex); |
cfe78e25 | 250 | /* Write futex before read reader_gp */ |
25cc6d18 | 251 | smp_mb_master(RCU_MB_GROUP); |
cfe78e25 MD |
252 | } |
253 | ||
fd189fa5 MD |
254 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
255 | switch (rcu_reader_state(&index->ctr)) { | |
256 | case RCU_READER_ACTIVE_CURRENT: | |
257 | if (cur_snap_readers) { | |
258 | cds_list_move(&index->node, | |
259 | cur_snap_readers); | |
260 | break; | |
261 | } | |
262 | /* Fall-through */ | |
263 | case RCU_READER_INACTIVE: | |
264 | cds_list_move(&index->node, qsreaders); | |
265 | break; | |
266 | case RCU_READER_ACTIVE_OLD: | |
267 | /* | |
268 | * Old snapshot. Leaving node in | |
269 | * input_readers will make us busy-loop | |
270 | * until the snapshot becomes current or | |
271 | * the reader becomes inactive. | |
272 | */ | |
273 | break; | |
274 | } | |
cfe78e25 MD |
275 | } |
276 | ||
e8043c1b | 277 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 278 | if (cds_list_empty(input_readers)) { |
cfe78e25 MD |
279 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { |
280 | /* Read reader_gp before write futex */ | |
25cc6d18 | 281 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e | 282 | uatomic_set(&rcu_gp.futex, 0); |
bc6c15bb | 283 | } |
cfe78e25 MD |
284 | break; |
285 | } else { | |
286 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) | |
287 | wait_gp(); | |
288 | else | |
06f22bdb | 289 | caa_cpu_relax(); |
bc6c15bb | 290 | } |
e8043c1b | 291 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 292 | /* |
40e140c9 | 293 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
294 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
295 | * for too long. | |
27b012e2 | 296 | */ |
fd189fa5 | 297 | if (cds_list_empty(input_readers)) { |
cfe78e25 MD |
298 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { |
299 | /* Read reader_gp before write futex */ | |
25cc6d18 | 300 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e | 301 | uatomic_set(&rcu_gp.futex, 0); |
cfe78e25 MD |
302 | } |
303 | break; | |
304 | } else { | |
305 | switch (wait_loops) { | |
bc6c15bb | 306 | case RCU_QS_ACTIVE_ATTEMPTS: |
cfe78e25 MD |
307 | wait_gp(); |
308 | break; /* only escape switch */ | |
bc6c15bb | 309 | case KICK_READER_LOOPS: |
25cc6d18 | 310 | smp_mb_master(RCU_MB_GROUP); |
40e140c9 | 311 | wait_loops = 0; |
cfe78e25 | 312 | break; /* only escape switch */ |
bc6c15bb | 313 | default: |
06f22bdb | 314 | caa_cpu_relax(); |
40e140c9 MD |
315 | } |
316 | } | |
e8043c1b | 317 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 318 | } |
27b012e2 MD |
319 | } |
320 | ||
9598a481 | 321 | void synchronize_rcu(void) |
2bc59bd7 | 322 | { |
fd189fa5 MD |
323 | CDS_LIST_HEAD(cur_snap_readers); |
324 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
325 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
326 | struct urcu_waiters waiters; | |
327 | ||
328 | /* | |
329 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
330 | * for a grace period. Proceed to perform the grace period only | |
331 | * if we are the first thread added into the queue. | |
332 | * The implicit memory barrier before urcu_wait_add() | |
333 | * orders prior memory accesses of threads put into the wait | |
334 | * queue before their insertion into the wait queue. | |
335 | */ | |
336 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
337 | /* Not first in queue: will be awakened by another thread. */ | |
338 | urcu_adaptative_busy_wait(&wait); | |
339 | /* Order following memory accesses after grace period. */ | |
340 | cmm_smp_mb(); | |
341 | return; | |
342 | } | |
343 | /* We won't need to wake ourself up */ | |
344 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 345 | |
6abb4bd5 | 346 | mutex_lock(&rcu_gp_lock); |
135530fd | 347 | |
5bffdd5d MD |
348 | /* |
349 | * Move all waiters into our local queue. | |
350 | */ | |
351 | urcu_move_waiters(&waiters, &gp_waiters); | |
352 | ||
16aa9ee8 | 353 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
354 | goto out; |
355 | ||
9598a481 | 356 | /* All threads should read qparity before accessing data structure |
6abb4bd5 MD |
357 | * where new ptr points to. Must be done within rcu_gp_lock because it |
358 | * iterates on reader threads.*/ | |
9598a481 | 359 | /* Write new ptr before changing the qparity */ |
25cc6d18 | 360 | smp_mb_master(RCU_MB_GROUP); |
9598a481 | 361 | |
9598a481 | 362 | /* |
c9488684 | 363 | * Wait for readers to observe original parity or be quiescent. |
9598a481 | 364 | */ |
fd189fa5 | 365 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
366 | |
367 | /* | |
c9488684 | 368 | * Must finish waiting for quiescent state for original parity before |
ed1b099e | 369 | * committing next rcu_gp.ctr update to memory. Failure to do so could |
d40fde2c MD |
370 | * result in the writer waiting forever while new readers are always |
371 | * accessing data (no progress). Enforce compiler-order of load | |
ed1b099e | 372 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr. |
9598a481 | 373 | */ |
5481ddb3 | 374 | cmm_barrier(); |
9598a481 | 375 | |
5dba80f9 | 376 | /* |
5481ddb3 | 377 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
378 | * model easier to understand. It does not have a big performance impact |
379 | * anyway, given this is the write-side. | |
380 | */ | |
5481ddb3 | 381 | cmm_smp_mb(); |
67c2d80b | 382 | |
c9488684 | 383 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
ed1b099e | 384 | CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE); |
c9488684 MD |
385 | |
386 | /* | |
ed1b099e | 387 | * Must commit rcu_gp.ctr update to memory before waiting for quiescent |
c9488684 MD |
388 | * state. Failure to do so could result in the writer waiting forever |
389 | * while new readers are always accessing data (no progress). Enforce | |
ed1b099e | 390 | * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr. |
c9488684 MD |
391 | */ |
392 | cmm_barrier(); | |
393 | ||
394 | /* | |
395 | * | |
396 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
397 | * model easier to understand. It does not have a big performance impact | |
398 | * anyway, given this is the write-side. | |
399 | */ | |
400 | cmm_smp_mb(); | |
401 | ||
9598a481 | 402 | /* |
c9488684 | 403 | * Wait for readers to observe new parity or be quiescent. |
9598a481 | 404 | */ |
fd189fa5 MD |
405 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
406 | ||
407 | /* | |
408 | * Put quiescent reader list back into registry. | |
409 | */ | |
410 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 411 | |
9598a481 | 412 | /* Finish waiting for reader threads before letting the old ptr being |
6abb4bd5 MD |
413 | * freed. Must be done within rcu_gp_lock because it iterates on reader |
414 | * threads. */ | |
25cc6d18 | 415 | smp_mb_master(RCU_MB_GROUP); |
2dfb8b5e | 416 | out: |
6abb4bd5 | 417 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
418 | |
419 | /* | |
420 | * Wakeup waiters only after we have completed the grace period | |
421 | * and have ensured the memory barriers at the end of the grace | |
422 | * period have been issued. | |
423 | */ | |
424 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 PM |
425 | } |
426 | ||
121a5d44 MD |
427 | /* |
428 | * library wrappers to be used by non-LGPL compatible source code. | |
429 | */ | |
430 | ||
431 | void rcu_read_lock(void) | |
432 | { | |
433 | _rcu_read_lock(); | |
434 | } | |
435 | ||
436 | void rcu_read_unlock(void) | |
437 | { | |
438 | _rcu_read_unlock(); | |
439 | } | |
440 | ||
882f3357 MD |
441 | int rcu_read_ongoing(void) |
442 | { | |
443 | return _rcu_read_ongoing(); | |
444 | } | |
445 | ||
121a5d44 | 446 | void rcu_register_thread(void) |
27b012e2 | 447 | { |
bd252a04 MD |
448 | URCU_TLS(rcu_reader).tid = pthread_self(); |
449 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
450 | assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); | |
02be5561 | 451 | |
6abb4bd5 | 452 | mutex_lock(&rcu_gp_lock); |
02be5561 | 453 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 454 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
6abb4bd5 | 455 | mutex_unlock(&rcu_gp_lock); |
27b012e2 MD |
456 | } |
457 | ||
121a5d44 | 458 | void rcu_unregister_thread(void) |
27b012e2 | 459 | { |
6abb4bd5 | 460 | mutex_lock(&rcu_gp_lock); |
bd252a04 | 461 | cds_list_del(&URCU_TLS(rcu_reader).node); |
6abb4bd5 | 462 | mutex_unlock(&rcu_gp_lock); |
27b012e2 MD |
463 | } |
464 | ||
fdf01eed MD |
465 | #ifdef RCU_MEMBARRIER |
466 | void rcu_init(void) | |
467 | { | |
468 | if (init_done) | |
469 | return; | |
470 | init_done = 1; | |
cf5271ee | 471 | if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY)) |
1de4df4b | 472 | rcu_has_sys_membarrier = 1; |
fdf01eed MD |
473 | } |
474 | #endif | |
475 | ||
476 | #ifdef RCU_SIGNAL | |
02be5561 | 477 | static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) |
27b012e2 | 478 | { |
40e140c9 | 479 | /* |
5481ddb3 DG |
480 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
481 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
482 | * executed on. |
483 | */ | |
5481ddb3 | 484 | cmm_smp_mb(); |
bd252a04 | 485 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 486 | cmm_smp_mb(); |
27b012e2 MD |
487 | } |
488 | ||
8a5fb4c9 | 489 | /* |
02be5561 | 490 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
491 | * reader threads are calling rcu_register_thread(). |
492 | * Should only be called by a single thread at a given time. This is ensured by | |
6abb4bd5 MD |
493 | * holing the rcu_gp_lock from rcu_register_thread() or by running at library |
494 | * load time, which should not be executed by multiple threads nor concurrently | |
495 | * with rcu_register_thread() anyway. | |
8a5fb4c9 | 496 | */ |
02be5561 | 497 | void rcu_init(void) |
27b012e2 MD |
498 | { |
499 | struct sigaction act; | |
500 | int ret; | |
501 | ||
8a5fb4c9 MD |
502 | if (init_done) |
503 | return; | |
504 | init_done = 1; | |
505 | ||
02be5561 | 506 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 507 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 508 | sigemptyset(&act.sa_mask); |
02be5561 | 509 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
510 | if (ret) |
511 | urcu_die(errno); | |
27b012e2 MD |
512 | } |
513 | ||
02be5561 | 514 | void rcu_exit(void) |
27b012e2 | 515 | { |
71210954 MD |
516 | /* |
517 | * Don't unregister the SIGRCU signal handler anymore, because | |
518 | * call_rcu threads could still be using it shortly before the | |
519 | * application exits. | |
520 | * Assertion disabled because call_rcu threads are now rcu | |
521 | * readers, and left running at exit. | |
522 | * assert(cds_list_empty(®istry)); | |
523 | */ | |
27b012e2 | 524 | } |
5e77fc1f | 525 | |
fdf01eed | 526 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 527 | |
5e6b23a6 | 528 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 529 | |
5e77fc1f | 530 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 531 | #include "urcu-defer-impl.h" |