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 | ||
fdf01eed | 65 | #ifdef RCU_MEMBARRIER |
834a45ba | 66 | static int init_done; |
1de4df4b | 67 | int rcu_has_sys_membarrier; |
834a45ba | 68 | |
02be5561 | 69 | void __attribute__((constructor)) rcu_init(void); |
fdf01eed MD |
70 | #endif |
71 | ||
72 | #ifdef RCU_MB | |
02be5561 | 73 | void rcu_init(void) |
e90a6e9c MD |
74 | { |
75 | } | |
76 | #endif | |
8a5fb4c9 | 77 | |
fdf01eed MD |
78 | #ifdef RCU_SIGNAL |
79 | static int init_done; | |
80 | ||
81 | void __attribute__((constructor)) rcu_init(void); | |
82 | void __attribute__((destructor)) rcu_exit(void); | |
83 | #endif | |
84 | ||
6abb4bd5 | 85 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
27b012e2 | 86 | |
1de4df4b | 87 | int32_t rcu_gp_futex; |
bc6c15bb | 88 | |
128166c9 MD |
89 | /* |
90 | * Global grace period counter. | |
02be5561 | 91 | * Contains the current RCU_GP_CTR_PHASE. |
afb8f2c9 | 92 | * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. |
b0d5e790 | 93 | * Written to only by writer with mutex taken. Read by both writer and readers. |
128166c9 | 94 | */ |
27d65bc5 | 95 | unsigned long rcu_gp_ctr = RCU_GP_COUNT; |
27b012e2 | 96 | |
b0d5e790 MD |
97 | /* |
98 | * Written to only by each individual reader. Read by both the reader and the | |
99 | * writers. | |
100 | */ | |
bd252a04 | 101 | DEFINE_URCU_TLS(struct rcu_reader, rcu_reader); |
27b012e2 | 102 | |
cf380c2f | 103 | #ifdef DEBUG_YIELD |
1de4df4b MD |
104 | unsigned int rcu_yield_active; |
105 | DEFINE_URCU_TLS(unsigned int, rcu_rand_yield); | |
cf380c2f MD |
106 | #endif |
107 | ||
16aa9ee8 | 108 | static CDS_LIST_HEAD(registry); |
27b012e2 | 109 | |
5bffdd5d MD |
110 | /* |
111 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
112 | * struct gp_waiters_thread objects. | |
113 | */ | |
114 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
115 | ||
6abb4bd5 | 116 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
117 | { |
118 | int ret; | |
09a9f986 PM |
119 | |
120 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 121 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
122 | if (ret) |
123 | urcu_die(ret); | |
09a9f986 | 124 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 125 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
126 | if (ret != EBUSY && ret != EINTR) |
127 | urcu_die(ret); | |
bd252a04 | 128 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 129 | cmm_smp_mb(); |
bd252a04 | 130 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 131 | cmm_smp_mb(); |
09a9f986 PM |
132 | } |
133 | poll(NULL,0,10); | |
134 | } | |
135 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
136 | } |
137 | ||
6abb4bd5 | 138 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
139 | { |
140 | int ret; | |
141 | ||
6abb4bd5 | 142 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
143 | if (ret) |
144 | urcu_die(ret); | |
41718ff9 MD |
145 | } |
146 | ||
fdf01eed | 147 | #ifdef RCU_MEMBARRIER |
25cc6d18 | 148 | static void smp_mb_master(int group) |
fdf01eed | 149 | { |
1de4df4b | 150 | if (caa_likely(rcu_has_sys_membarrier)) |
f0708810 | 151 | membarrier(MEMBARRIER_EXPEDITED); |
fdf01eed | 152 | else |
5481ddb3 | 153 | cmm_smp_mb(); |
fdf01eed MD |
154 | } |
155 | #endif | |
156 | ||
02be5561 | 157 | #ifdef RCU_MB |
25cc6d18 | 158 | static void smp_mb_master(int group) |
40e140c9 | 159 | { |
5481ddb3 | 160 | cmm_smp_mb(); |
40e140c9 | 161 | } |
fdf01eed MD |
162 | #endif |
163 | ||
164 | #ifdef RCU_SIGNAL | |
78ff9419 | 165 | static void force_mb_all_readers(void) |
27b012e2 | 166 | { |
02be5561 | 167 | struct rcu_reader *index; |
e3b0cef0 | 168 | |
27b012e2 | 169 | /* |
5481ddb3 | 170 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
171 | * compiler barriers around rcu read lock as real memory barriers. |
172 | */ | |
16aa9ee8 | 173 | if (cds_list_empty(®istry)) |
27b012e2 | 174 | return; |
3a86deba | 175 | /* |
5481ddb3 | 176 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 177 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 178 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 179 | * cache flush is enforced. |
3a86deba | 180 | */ |
16aa9ee8 | 181 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 182 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 183 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 184 | } |
27b012e2 MD |
185 | /* |
186 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
187 | * |
188 | * Note that the pthread_kill() will never be executed on systems | |
189 | * that correctly deliver signals in a timely manner. However, it | |
190 | * is not uncommon for kernels to have bugs that can result in | |
191 | * lost or unduly delayed signals. | |
192 | * | |
193 | * If you are seeing the below pthread_kill() executing much at | |
194 | * all, we suggest testing the underlying kernel and filing the | |
195 | * relevant bug report. For Linux kernels, we recommend getting | |
196 | * the Linux Test Project (LTP). | |
27b012e2 | 197 | */ |
16aa9ee8 | 198 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 199 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 200 | pthread_kill(index->tid, SIGRCU); |
09a9f986 PM |
201 | poll(NULL, 0, 1); |
202 | } | |
203 | } | |
5481ddb3 | 204 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 205 | } |
9d7e3f89 | 206 | |
25cc6d18 | 207 | static void smp_mb_master(int group) |
9d7e3f89 MD |
208 | { |
209 | force_mb_all_readers(); | |
210 | } | |
fdf01eed | 211 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 212 | |
bc6c15bb MD |
213 | /* |
214 | * synchronize_rcu() waiting. Single thread. | |
215 | */ | |
cfe78e25 | 216 | static void wait_gp(void) |
bc6c15bb | 217 | { |
cfe78e25 | 218 | /* Read reader_gp before read futex */ |
25cc6d18 | 219 | smp_mb_master(RCU_MB_GROUP); |
1de4df4b MD |
220 | if (uatomic_read(&rcu_gp_futex) == -1) |
221 | futex_async(&rcu_gp_futex, FUTEX_WAIT, -1, | |
cfe78e25 | 222 | NULL, NULL, 0); |
bc6c15bb MD |
223 | } |
224 | ||
fd189fa5 MD |
225 | static void wait_for_readers(struct cds_list_head *input_readers, |
226 | struct cds_list_head *cur_snap_readers, | |
227 | struct cds_list_head *qsreaders) | |
27b012e2 | 228 | { |
cfe78e25 | 229 | int wait_loops = 0; |
02be5561 | 230 | struct rcu_reader *index, *tmp; |
27b012e2 | 231 | |
40e140c9 | 232 | /* |
c9488684 MD |
233 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
234 | * indicate quiescence (not nested), or observe the current | |
235 | * rcu_gp_ctr value. | |
27b012e2 | 236 | */ |
cfe78e25 MD |
237 | for (;;) { |
238 | wait_loops++; | |
239 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { | |
1de4df4b | 240 | uatomic_dec(&rcu_gp_futex); |
cfe78e25 | 241 | /* Write futex before read reader_gp */ |
25cc6d18 | 242 | smp_mb_master(RCU_MB_GROUP); |
cfe78e25 MD |
243 | } |
244 | ||
fd189fa5 MD |
245 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
246 | switch (rcu_reader_state(&index->ctr)) { | |
247 | case RCU_READER_ACTIVE_CURRENT: | |
248 | if (cur_snap_readers) { | |
249 | cds_list_move(&index->node, | |
250 | cur_snap_readers); | |
251 | break; | |
252 | } | |
253 | /* Fall-through */ | |
254 | case RCU_READER_INACTIVE: | |
255 | cds_list_move(&index->node, qsreaders); | |
256 | break; | |
257 | case RCU_READER_ACTIVE_OLD: | |
258 | /* | |
259 | * Old snapshot. Leaving node in | |
260 | * input_readers will make us busy-loop | |
261 | * until the snapshot becomes current or | |
262 | * the reader becomes inactive. | |
263 | */ | |
264 | break; | |
265 | } | |
cfe78e25 MD |
266 | } |
267 | ||
e8043c1b | 268 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 269 | if (cds_list_empty(input_readers)) { |
cfe78e25 MD |
270 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { |
271 | /* Read reader_gp before write futex */ | |
25cc6d18 | 272 | smp_mb_master(RCU_MB_GROUP); |
1de4df4b | 273 | uatomic_set(&rcu_gp_futex, 0); |
bc6c15bb | 274 | } |
cfe78e25 MD |
275 | break; |
276 | } else { | |
277 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) | |
278 | wait_gp(); | |
279 | else | |
06f22bdb | 280 | caa_cpu_relax(); |
bc6c15bb | 281 | } |
e8043c1b | 282 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 283 | /* |
40e140c9 | 284 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
285 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
286 | * for too long. | |
27b012e2 | 287 | */ |
fd189fa5 | 288 | if (cds_list_empty(input_readers)) { |
cfe78e25 MD |
289 | if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { |
290 | /* Read reader_gp before write futex */ | |
25cc6d18 | 291 | smp_mb_master(RCU_MB_GROUP); |
1de4df4b | 292 | uatomic_set(&rcu_gp_futex, 0); |
cfe78e25 MD |
293 | } |
294 | break; | |
295 | } else { | |
296 | switch (wait_loops) { | |
bc6c15bb | 297 | case RCU_QS_ACTIVE_ATTEMPTS: |
cfe78e25 MD |
298 | wait_gp(); |
299 | break; /* only escape switch */ | |
bc6c15bb | 300 | case KICK_READER_LOOPS: |
25cc6d18 | 301 | smp_mb_master(RCU_MB_GROUP); |
40e140c9 | 302 | wait_loops = 0; |
cfe78e25 | 303 | break; /* only escape switch */ |
bc6c15bb | 304 | default: |
06f22bdb | 305 | caa_cpu_relax(); |
40e140c9 MD |
306 | } |
307 | } | |
e8043c1b | 308 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 309 | } |
27b012e2 MD |
310 | } |
311 | ||
9598a481 | 312 | void synchronize_rcu(void) |
2bc59bd7 | 313 | { |
fd189fa5 MD |
314 | CDS_LIST_HEAD(cur_snap_readers); |
315 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
316 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
317 | struct urcu_waiters waiters; | |
318 | ||
319 | /* | |
320 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
321 | * for a grace period. Proceed to perform the grace period only | |
322 | * if we are the first thread added into the queue. | |
323 | * The implicit memory barrier before urcu_wait_add() | |
324 | * orders prior memory accesses of threads put into the wait | |
325 | * queue before their insertion into the wait queue. | |
326 | */ | |
327 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
328 | /* Not first in queue: will be awakened by another thread. */ | |
329 | urcu_adaptative_busy_wait(&wait); | |
330 | /* Order following memory accesses after grace period. */ | |
331 | cmm_smp_mb(); | |
332 | return; | |
333 | } | |
334 | /* We won't need to wake ourself up */ | |
335 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 336 | |
6abb4bd5 | 337 | mutex_lock(&rcu_gp_lock); |
135530fd | 338 | |
5bffdd5d MD |
339 | /* |
340 | * Move all waiters into our local queue. | |
341 | */ | |
342 | urcu_move_waiters(&waiters, &gp_waiters); | |
343 | ||
16aa9ee8 | 344 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
345 | goto out; |
346 | ||
9598a481 | 347 | /* All threads should read qparity before accessing data structure |
6abb4bd5 MD |
348 | * where new ptr points to. Must be done within rcu_gp_lock because it |
349 | * iterates on reader threads.*/ | |
9598a481 | 350 | /* Write new ptr before changing the qparity */ |
25cc6d18 | 351 | smp_mb_master(RCU_MB_GROUP); |
9598a481 | 352 | |
9598a481 | 353 | /* |
c9488684 | 354 | * Wait for readers to observe original parity or be quiescent. |
9598a481 | 355 | */ |
fd189fa5 | 356 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
357 | |
358 | /* | |
c9488684 | 359 | * Must finish waiting for quiescent state for original parity before |
d40fde2c MD |
360 | * committing next rcu_gp_ctr update to memory. Failure to do so could |
361 | * result in the writer waiting forever while new readers are always | |
362 | * accessing data (no progress). Enforce compiler-order of load | |
bd252a04 | 363 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp_ctr. |
9598a481 | 364 | */ |
5481ddb3 | 365 | cmm_barrier(); |
9598a481 | 366 | |
5dba80f9 | 367 | /* |
5481ddb3 | 368 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
369 | * model easier to understand. It does not have a big performance impact |
370 | * anyway, given this is the write-side. | |
371 | */ | |
5481ddb3 | 372 | cmm_smp_mb(); |
67c2d80b | 373 | |
c9488684 MD |
374 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
375 | CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); | |
376 | ||
377 | /* | |
378 | * Must commit rcu_gp_ctr update to memory before waiting for quiescent | |
379 | * state. Failure to do so could result in the writer waiting forever | |
380 | * while new readers are always accessing data (no progress). Enforce | |
381 | * compiler-order of store to rcu_gp_ctr before load rcu_reader ctr. | |
382 | */ | |
383 | cmm_barrier(); | |
384 | ||
385 | /* | |
386 | * | |
387 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
388 | * model easier to understand. It does not have a big performance impact | |
389 | * anyway, given this is the write-side. | |
390 | */ | |
391 | cmm_smp_mb(); | |
392 | ||
9598a481 | 393 | /* |
c9488684 | 394 | * Wait for readers to observe new parity or be quiescent. |
9598a481 | 395 | */ |
fd189fa5 MD |
396 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
397 | ||
398 | /* | |
399 | * Put quiescent reader list back into registry. | |
400 | */ | |
401 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 402 | |
9598a481 | 403 | /* Finish waiting for reader threads before letting the old ptr being |
6abb4bd5 MD |
404 | * freed. Must be done within rcu_gp_lock because it iterates on reader |
405 | * threads. */ | |
25cc6d18 | 406 | smp_mb_master(RCU_MB_GROUP); |
2dfb8b5e | 407 | out: |
6abb4bd5 | 408 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
409 | |
410 | /* | |
411 | * Wakeup waiters only after we have completed the grace period | |
412 | * and have ensured the memory barriers at the end of the grace | |
413 | * period have been issued. | |
414 | */ | |
415 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 PM |
416 | } |
417 | ||
121a5d44 MD |
418 | /* |
419 | * library wrappers to be used by non-LGPL compatible source code. | |
420 | */ | |
421 | ||
422 | void rcu_read_lock(void) | |
423 | { | |
424 | _rcu_read_lock(); | |
425 | } | |
426 | ||
427 | void rcu_read_unlock(void) | |
428 | { | |
429 | _rcu_read_unlock(); | |
430 | } | |
431 | ||
121a5d44 | 432 | void rcu_register_thread(void) |
27b012e2 | 433 | { |
bd252a04 MD |
434 | URCU_TLS(rcu_reader).tid = pthread_self(); |
435 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
436 | assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); | |
02be5561 | 437 | |
6abb4bd5 | 438 | mutex_lock(&rcu_gp_lock); |
02be5561 | 439 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 440 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
6abb4bd5 | 441 | mutex_unlock(&rcu_gp_lock); |
27b012e2 MD |
442 | } |
443 | ||
121a5d44 | 444 | void rcu_unregister_thread(void) |
27b012e2 | 445 | { |
6abb4bd5 | 446 | mutex_lock(&rcu_gp_lock); |
bd252a04 | 447 | cds_list_del(&URCU_TLS(rcu_reader).node); |
6abb4bd5 | 448 | mutex_unlock(&rcu_gp_lock); |
27b012e2 MD |
449 | } |
450 | ||
fdf01eed MD |
451 | #ifdef RCU_MEMBARRIER |
452 | void rcu_init(void) | |
453 | { | |
454 | if (init_done) | |
455 | return; | |
456 | init_done = 1; | |
cf5271ee | 457 | if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY)) |
1de4df4b | 458 | rcu_has_sys_membarrier = 1; |
fdf01eed MD |
459 | } |
460 | #endif | |
461 | ||
462 | #ifdef RCU_SIGNAL | |
02be5561 | 463 | static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) |
27b012e2 | 464 | { |
40e140c9 | 465 | /* |
5481ddb3 DG |
466 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
467 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
468 | * executed on. |
469 | */ | |
5481ddb3 | 470 | cmm_smp_mb(); |
bd252a04 | 471 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 472 | cmm_smp_mb(); |
27b012e2 MD |
473 | } |
474 | ||
8a5fb4c9 | 475 | /* |
02be5561 | 476 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
477 | * reader threads are calling rcu_register_thread(). |
478 | * Should only be called by a single thread at a given time. This is ensured by | |
6abb4bd5 MD |
479 | * holing the rcu_gp_lock from rcu_register_thread() or by running at library |
480 | * load time, which should not be executed by multiple threads nor concurrently | |
481 | * with rcu_register_thread() anyway. | |
8a5fb4c9 | 482 | */ |
02be5561 | 483 | void rcu_init(void) |
27b012e2 MD |
484 | { |
485 | struct sigaction act; | |
486 | int ret; | |
487 | ||
8a5fb4c9 MD |
488 | if (init_done) |
489 | return; | |
490 | init_done = 1; | |
491 | ||
02be5561 | 492 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 493 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 494 | sigemptyset(&act.sa_mask); |
02be5561 | 495 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
496 | if (ret) |
497 | urcu_die(errno); | |
27b012e2 MD |
498 | } |
499 | ||
02be5561 | 500 | void rcu_exit(void) |
27b012e2 MD |
501 | { |
502 | struct sigaction act; | |
503 | int ret; | |
504 | ||
02be5561 | 505 | ret = sigaction(SIGRCU, NULL, &act); |
4a6d7378 MD |
506 | if (ret) |
507 | urcu_die(errno); | |
02be5561 | 508 | assert(act.sa_sigaction == sigrcu_handler); |
16aa9ee8 | 509 | assert(cds_list_empty(®istry)); |
27b012e2 | 510 | } |
5e77fc1f | 511 | |
fdf01eed | 512 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 513 | |
5e6b23a6 | 514 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 515 | |
5e77fc1f | 516 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 517 | #include "urcu-defer-impl.h" |