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 | |
9340c38d | 56 | * per-se), kick it after 10 loops waiting for it. |
3a71751e | 57 | */ |
9340c38d | 58 | #define KICK_READER_LOOPS 10 |
3a71751e PB |
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 | |
16aa9ee8 | 112 | static CDS_LIST_HEAD(registry); |
27b012e2 | 113 | |
5bffdd5d MD |
114 | /* |
115 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
116 | * struct gp_waiters_thread objects. | |
117 | */ | |
118 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
119 | ||
6abb4bd5 | 120 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
121 | { |
122 | int ret; | |
09a9f986 PM |
123 | |
124 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 125 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
126 | if (ret) |
127 | urcu_die(ret); | |
09a9f986 | 128 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 129 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
130 | if (ret != EBUSY && ret != EINTR) |
131 | urcu_die(ret); | |
bd252a04 | 132 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 133 | cmm_smp_mb(); |
bd252a04 | 134 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 135 | cmm_smp_mb(); |
09a9f986 PM |
136 | } |
137 | poll(NULL,0,10); | |
138 | } | |
139 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
140 | } |
141 | ||
6abb4bd5 | 142 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
143 | { |
144 | int ret; | |
145 | ||
6abb4bd5 | 146 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
147 | if (ret) |
148 | urcu_die(ret); | |
41718ff9 MD |
149 | } |
150 | ||
fdf01eed | 151 | #ifdef RCU_MEMBARRIER |
25cc6d18 | 152 | static void smp_mb_master(int group) |
fdf01eed | 153 | { |
1de4df4b | 154 | if (caa_likely(rcu_has_sys_membarrier)) |
553b7eb9 | 155 | (void) membarrier(MEMBARRIER_EXPEDITED); |
fdf01eed | 156 | else |
5481ddb3 | 157 | cmm_smp_mb(); |
fdf01eed MD |
158 | } |
159 | #endif | |
160 | ||
02be5561 | 161 | #ifdef RCU_MB |
25cc6d18 | 162 | static void smp_mb_master(int group) |
40e140c9 | 163 | { |
5481ddb3 | 164 | cmm_smp_mb(); |
40e140c9 | 165 | } |
fdf01eed MD |
166 | #endif |
167 | ||
168 | #ifdef RCU_SIGNAL | |
78ff9419 | 169 | static void force_mb_all_readers(void) |
27b012e2 | 170 | { |
02be5561 | 171 | struct rcu_reader *index; |
e3b0cef0 | 172 | |
27b012e2 | 173 | /* |
5481ddb3 | 174 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
175 | * compiler barriers around rcu read lock as real memory barriers. |
176 | */ | |
16aa9ee8 | 177 | if (cds_list_empty(®istry)) |
27b012e2 | 178 | return; |
3a86deba | 179 | /* |
5481ddb3 | 180 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 181 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 182 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 183 | * cache flush is enforced. |
3a86deba | 184 | */ |
16aa9ee8 | 185 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 186 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 187 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 188 | } |
27b012e2 MD |
189 | /* |
190 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
191 | * |
192 | * Note that the pthread_kill() will never be executed on systems | |
193 | * that correctly deliver signals in a timely manner. However, it | |
194 | * is not uncommon for kernels to have bugs that can result in | |
195 | * lost or unduly delayed signals. | |
196 | * | |
197 | * If you are seeing the below pthread_kill() executing much at | |
198 | * all, we suggest testing the underlying kernel and filing the | |
199 | * relevant bug report. For Linux kernels, we recommend getting | |
200 | * the Linux Test Project (LTP). | |
27b012e2 | 201 | */ |
16aa9ee8 | 202 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 203 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 204 | pthread_kill(index->tid, SIGRCU); |
09a9f986 PM |
205 | poll(NULL, 0, 1); |
206 | } | |
207 | } | |
5481ddb3 | 208 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 209 | } |
9d7e3f89 | 210 | |
25cc6d18 | 211 | static void smp_mb_master(int group) |
9d7e3f89 MD |
212 | { |
213 | force_mb_all_readers(); | |
214 | } | |
fdf01eed | 215 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 216 | |
bc6c15bb MD |
217 | /* |
218 | * synchronize_rcu() waiting. Single thread. | |
219 | */ | |
cfe78e25 | 220 | static void wait_gp(void) |
bc6c15bb | 221 | { |
cfe78e25 | 222 | /* Read reader_gp before read futex */ |
25cc6d18 | 223 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e LJ |
224 | if (uatomic_read(&rcu_gp.futex) == -1) |
225 | futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, | |
cfe78e25 | 226 | NULL, NULL, 0); |
bc6c15bb MD |
227 | } |
228 | ||
fd189fa5 MD |
229 | static void wait_for_readers(struct cds_list_head *input_readers, |
230 | struct cds_list_head *cur_snap_readers, | |
231 | struct cds_list_head *qsreaders) | |
27b012e2 | 232 | { |
9340c38d | 233 | unsigned int wait_loops = 0; |
02be5561 | 234 | struct rcu_reader *index, *tmp; |
9340c38d MD |
235 | #ifdef HAS_INCOHERENT_CACHES |
236 | unsigned int wait_gp_loops = 0; | |
237 | #endif /* HAS_INCOHERENT_CACHES */ | |
27b012e2 | 238 | |
40e140c9 | 239 | /* |
c9488684 MD |
240 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
241 | * indicate quiescence (not nested), or observe the current | |
ed1b099e | 242 | * rcu_gp.ctr value. |
27b012e2 | 243 | */ |
cfe78e25 | 244 | for (;;) { |
5e81fed7 MD |
245 | if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) |
246 | wait_loops++; | |
9340c38d | 247 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
ed1b099e | 248 | uatomic_dec(&rcu_gp.futex); |
cfe78e25 | 249 | /* Write futex before read reader_gp */ |
25cc6d18 | 250 | smp_mb_master(RCU_MB_GROUP); |
cfe78e25 MD |
251 | } |
252 | ||
fd189fa5 MD |
253 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
254 | switch (rcu_reader_state(&index->ctr)) { | |
255 | case RCU_READER_ACTIVE_CURRENT: | |
256 | if (cur_snap_readers) { | |
257 | cds_list_move(&index->node, | |
258 | cur_snap_readers); | |
259 | break; | |
260 | } | |
261 | /* Fall-through */ | |
262 | case RCU_READER_INACTIVE: | |
263 | cds_list_move(&index->node, qsreaders); | |
264 | break; | |
265 | case RCU_READER_ACTIVE_OLD: | |
266 | /* | |
267 | * Old snapshot. Leaving node in | |
268 | * input_readers will make us busy-loop | |
269 | * until the snapshot becomes current or | |
270 | * the reader becomes inactive. | |
271 | */ | |
272 | break; | |
273 | } | |
cfe78e25 MD |
274 | } |
275 | ||
e8043c1b | 276 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 277 | if (cds_list_empty(input_readers)) { |
9340c38d | 278 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 279 | /* Read reader_gp before write futex */ |
25cc6d18 | 280 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e | 281 | uatomic_set(&rcu_gp.futex, 0); |
bc6c15bb | 282 | } |
cfe78e25 MD |
283 | break; |
284 | } else { | |
9340c38d | 285 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) |
cfe78e25 MD |
286 | wait_gp(); |
287 | else | |
06f22bdb | 288 | caa_cpu_relax(); |
bc6c15bb | 289 | } |
e8043c1b | 290 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 291 | /* |
40e140c9 | 292 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
293 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
294 | * for too long. | |
27b012e2 | 295 | */ |
fd189fa5 | 296 | if (cds_list_empty(input_readers)) { |
9340c38d | 297 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 298 | /* Read reader_gp before write futex */ |
25cc6d18 | 299 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e | 300 | uatomic_set(&rcu_gp.futex, 0); |
cfe78e25 MD |
301 | } |
302 | break; | |
303 | } else { | |
9340c38d | 304 | if (wait_gp_loops == KICK_READER_LOOPS) { |
25cc6d18 | 305 | smp_mb_master(RCU_MB_GROUP); |
9340c38d MD |
306 | wait_gp_loops = 0; |
307 | } | |
308 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { | |
309 | wait_gp(); | |
310 | wait_gp_loops++; | |
311 | } else { | |
06f22bdb | 312 | caa_cpu_relax(); |
40e140c9 MD |
313 | } |
314 | } | |
e8043c1b | 315 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 316 | } |
27b012e2 MD |
317 | } |
318 | ||
9598a481 | 319 | void synchronize_rcu(void) |
2bc59bd7 | 320 | { |
fd189fa5 MD |
321 | CDS_LIST_HEAD(cur_snap_readers); |
322 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
323 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
324 | struct urcu_waiters waiters; | |
325 | ||
326 | /* | |
327 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
328 | * for a grace period. Proceed to perform the grace period only | |
329 | * if we are the first thread added into the queue. | |
330 | * The implicit memory barrier before urcu_wait_add() | |
331 | * orders prior memory accesses of threads put into the wait | |
332 | * queue before their insertion into the wait queue. | |
333 | */ | |
334 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
335 | /* Not first in queue: will be awakened by another thread. */ | |
336 | urcu_adaptative_busy_wait(&wait); | |
337 | /* Order following memory accesses after grace period. */ | |
338 | cmm_smp_mb(); | |
339 | return; | |
340 | } | |
341 | /* We won't need to wake ourself up */ | |
342 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 343 | |
6abb4bd5 | 344 | mutex_lock(&rcu_gp_lock); |
135530fd | 345 | |
5bffdd5d MD |
346 | /* |
347 | * Move all waiters into our local queue. | |
348 | */ | |
349 | urcu_move_waiters(&waiters, &gp_waiters); | |
350 | ||
16aa9ee8 | 351 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
352 | goto out; |
353 | ||
9598a481 | 354 | /* All threads should read qparity before accessing data structure |
6abb4bd5 MD |
355 | * where new ptr points to. Must be done within rcu_gp_lock because it |
356 | * iterates on reader threads.*/ | |
9598a481 | 357 | /* Write new ptr before changing the qparity */ |
25cc6d18 | 358 | smp_mb_master(RCU_MB_GROUP); |
9598a481 | 359 | |
9598a481 | 360 | /* |
c9488684 | 361 | * Wait for readers to observe original parity or be quiescent. |
9598a481 | 362 | */ |
fd189fa5 | 363 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
364 | |
365 | /* | |
c9488684 | 366 | * Must finish waiting for quiescent state for original parity before |
ed1b099e | 367 | * committing next rcu_gp.ctr update to memory. Failure to do so could |
d40fde2c MD |
368 | * result in the writer waiting forever while new readers are always |
369 | * accessing data (no progress). Enforce compiler-order of load | |
ed1b099e | 370 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr. |
9598a481 | 371 | */ |
5481ddb3 | 372 | cmm_barrier(); |
9598a481 | 373 | |
5dba80f9 | 374 | /* |
5481ddb3 | 375 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
376 | * model easier to understand. It does not have a big performance impact |
377 | * anyway, given this is the write-side. | |
378 | */ | |
5481ddb3 | 379 | cmm_smp_mb(); |
67c2d80b | 380 | |
c9488684 | 381 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
ed1b099e | 382 | CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE); |
c9488684 MD |
383 | |
384 | /* | |
ed1b099e | 385 | * Must commit rcu_gp.ctr update to memory before waiting for quiescent |
c9488684 MD |
386 | * state. Failure to do so could result in the writer waiting forever |
387 | * while new readers are always accessing data (no progress). Enforce | |
ed1b099e | 388 | * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr. |
c9488684 MD |
389 | */ |
390 | cmm_barrier(); | |
391 | ||
392 | /* | |
393 | * | |
394 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
395 | * model easier to understand. It does not have a big performance impact | |
396 | * anyway, given this is the write-side. | |
397 | */ | |
398 | cmm_smp_mb(); | |
399 | ||
9598a481 | 400 | /* |
c9488684 | 401 | * Wait for readers to observe new parity or be quiescent. |
9598a481 | 402 | */ |
fd189fa5 MD |
403 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
404 | ||
405 | /* | |
406 | * Put quiescent reader list back into registry. | |
407 | */ | |
408 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 409 | |
9598a481 | 410 | /* Finish waiting for reader threads before letting the old ptr being |
6abb4bd5 MD |
411 | * freed. Must be done within rcu_gp_lock because it iterates on reader |
412 | * threads. */ | |
25cc6d18 | 413 | smp_mb_master(RCU_MB_GROUP); |
2dfb8b5e | 414 | out: |
6abb4bd5 | 415 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
416 | |
417 | /* | |
418 | * Wakeup waiters only after we have completed the grace period | |
419 | * and have ensured the memory barriers at the end of the grace | |
420 | * period have been issued. | |
421 | */ | |
422 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 PM |
423 | } |
424 | ||
121a5d44 MD |
425 | /* |
426 | * library wrappers to be used by non-LGPL compatible source code. | |
427 | */ | |
428 | ||
429 | void rcu_read_lock(void) | |
430 | { | |
431 | _rcu_read_lock(); | |
432 | } | |
433 | ||
434 | void rcu_read_unlock(void) | |
435 | { | |
436 | _rcu_read_unlock(); | |
437 | } | |
438 | ||
882f3357 MD |
439 | int rcu_read_ongoing(void) |
440 | { | |
441 | return _rcu_read_ongoing(); | |
442 | } | |
443 | ||
121a5d44 | 444 | void rcu_register_thread(void) |
27b012e2 | 445 | { |
bd252a04 MD |
446 | URCU_TLS(rcu_reader).tid = pthread_self(); |
447 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
448 | assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); | |
02be5561 | 449 | |
6abb4bd5 | 450 | mutex_lock(&rcu_gp_lock); |
02be5561 | 451 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 452 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
6abb4bd5 | 453 | mutex_unlock(&rcu_gp_lock); |
27b012e2 MD |
454 | } |
455 | ||
121a5d44 | 456 | void rcu_unregister_thread(void) |
27b012e2 | 457 | { |
6abb4bd5 | 458 | mutex_lock(&rcu_gp_lock); |
bd252a04 | 459 | cds_list_del(&URCU_TLS(rcu_reader).node); |
6abb4bd5 | 460 | mutex_unlock(&rcu_gp_lock); |
27b012e2 MD |
461 | } |
462 | ||
fdf01eed MD |
463 | #ifdef RCU_MEMBARRIER |
464 | void rcu_init(void) | |
465 | { | |
466 | if (init_done) | |
467 | return; | |
468 | init_done = 1; | |
cf5271ee | 469 | if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY)) |
1de4df4b | 470 | rcu_has_sys_membarrier = 1; |
fdf01eed MD |
471 | } |
472 | #endif | |
473 | ||
474 | #ifdef RCU_SIGNAL | |
02be5561 | 475 | static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) |
27b012e2 | 476 | { |
40e140c9 | 477 | /* |
5481ddb3 DG |
478 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
479 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
480 | * executed on. |
481 | */ | |
5481ddb3 | 482 | cmm_smp_mb(); |
bd252a04 | 483 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 484 | cmm_smp_mb(); |
27b012e2 MD |
485 | } |
486 | ||
8a5fb4c9 | 487 | /* |
02be5561 | 488 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
489 | * reader threads are calling rcu_register_thread(). |
490 | * Should only be called by a single thread at a given time. This is ensured by | |
6abb4bd5 MD |
491 | * holing the rcu_gp_lock from rcu_register_thread() or by running at library |
492 | * load time, which should not be executed by multiple threads nor concurrently | |
493 | * with rcu_register_thread() anyway. | |
8a5fb4c9 | 494 | */ |
02be5561 | 495 | void rcu_init(void) |
27b012e2 MD |
496 | { |
497 | struct sigaction act; | |
498 | int ret; | |
499 | ||
8a5fb4c9 MD |
500 | if (init_done) |
501 | return; | |
502 | init_done = 1; | |
503 | ||
02be5561 | 504 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 505 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 506 | sigemptyset(&act.sa_mask); |
02be5561 | 507 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
508 | if (ret) |
509 | urcu_die(errno); | |
27b012e2 MD |
510 | } |
511 | ||
02be5561 | 512 | void rcu_exit(void) |
27b012e2 | 513 | { |
71210954 MD |
514 | /* |
515 | * Don't unregister the SIGRCU signal handler anymore, because | |
516 | * call_rcu threads could still be using it shortly before the | |
517 | * application exits. | |
518 | * Assertion disabled because call_rcu threads are now rcu | |
519 | * readers, and left running at exit. | |
520 | * assert(cds_list_empty(®istry)); | |
521 | */ | |
27b012e2 | 522 | } |
5e77fc1f | 523 | |
fdf01eed | 524 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 525 | |
5e6b23a6 | 526 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 527 | |
5e77fc1f | 528 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 529 | #include "urcu-defer-impl.h" |