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 |
ed42f676 | 29 | #define _DEFAULT_SOURCE |
27b012e2 MD |
30 | #include <stdio.h> |
31 | #include <pthread.h> | |
32 | #include <signal.h> | |
33 | #include <assert.h> | |
f69f195a | 34 | #include <stdlib.h> |
6d841bc2 | 35 | #include <stdint.h> |
f69f195a | 36 | #include <string.h> |
09a9f986 | 37 | #include <errno.h> |
e8043c1b | 38 | #include <poll.h> |
27b012e2 | 39 | |
71c811bf | 40 | #include "urcu/wfqueue.h" |
57760d44 | 41 | #include "urcu/map/urcu.h" |
af7c2dbe | 42 | #include "urcu/static/urcu.h" |
618b2595 | 43 | #include "urcu-pointer.h" |
bd252a04 | 44 | #include "urcu/tls-compat.h" |
71c811bf | 45 | |
4a6d7378 MD |
46 | #include "urcu-die.h" |
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 | |
6b702fa4 | 56 | * per-se), kick it after 10 loops waiting for it. |
3a71751e | 57 | */ |
6b702fa4 | 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 | ||
fdf01eed | 65 | #ifdef RCU_MEMBARRIER |
834a45ba | 66 | static int init_done; |
fdf01eed | 67 | int 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 | ||
66bc4dcd MD |
85 | /* |
86 | * rcu_gp_lock ensures mutual exclusion between threads calling | |
87 | * synchronize_rcu(). | |
88 | */ | |
6abb4bd5 | 89 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
66bc4dcd MD |
90 | /* |
91 | * rcu_registry_lock ensures mutual exclusion between threads | |
92 | * registering and unregistering themselves to/from the registry, and | |
93 | * with threads reading that registry from synchronize_rcu(). However, | |
94 | * this lock is not held all the way through the completion of awaiting | |
95 | * for the grace period. It is sporadically released between iterations | |
96 | * on the registry. | |
97 | * rcu_registry_lock may nest inside rcu_gp_lock. | |
98 | */ | |
99 | static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER; | |
27b012e2 | 100 | |
6d841bc2 | 101 | int32_t gp_futex; |
bc6c15bb | 102 | |
128166c9 MD |
103 | /* |
104 | * Global grace period counter. | |
02be5561 | 105 | * Contains the current RCU_GP_CTR_PHASE. |
afb8f2c9 | 106 | * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path. |
b0d5e790 | 107 | * Written to only by writer with mutex taken. Read by both writer and readers. |
128166c9 | 108 | */ |
27d65bc5 | 109 | unsigned long rcu_gp_ctr = RCU_GP_COUNT; |
b0d5e790 MD |
110 | /* |
111 | * Written to only by each individual reader. Read by both the reader and the | |
112 | * writers. | |
113 | */ | |
1745be1a | 114 | __DEFINE_URCU_TLS_GLOBAL(struct rcu_reader, rcu_reader); |
27b012e2 | 115 | |
cf380c2f | 116 | #ifdef DEBUG_YIELD |
9d335088 | 117 | unsigned int yield_active; |
1745be1a | 118 | __DEFINE_URCU_TLS_GLOBAL(unsigned int, rand_yield); |
cf380c2f MD |
119 | #endif |
120 | ||
16aa9ee8 | 121 | static CDS_LIST_HEAD(registry); |
27b012e2 | 122 | |
6abb4bd5 | 123 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
124 | { |
125 | int ret; | |
09a9f986 PM |
126 | |
127 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 128 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
129 | if (ret) |
130 | urcu_die(ret); | |
09a9f986 | 131 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 132 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
133 | if (ret != EBUSY && ret != EINTR) |
134 | urcu_die(ret); | |
bd252a04 | 135 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 136 | cmm_smp_mb(); |
bd252a04 | 137 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 138 | cmm_smp_mb(); |
09a9f986 PM |
139 | } |
140 | poll(NULL,0,10); | |
141 | } | |
142 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
143 | } |
144 | ||
6abb4bd5 | 145 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
146 | { |
147 | int ret; | |
148 | ||
6abb4bd5 | 149 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
150 | if (ret) |
151 | urcu_die(ret); | |
41718ff9 MD |
152 | } |
153 | ||
fdf01eed | 154 | #ifdef RCU_MEMBARRIER |
25cc6d18 | 155 | static void smp_mb_master(int group) |
fdf01eed | 156 | { |
a0b7f7ea | 157 | if (caa_likely(has_sys_membarrier)) |
f0708810 | 158 | membarrier(MEMBARRIER_EXPEDITED); |
fdf01eed | 159 | else |
5481ddb3 | 160 | cmm_smp_mb(); |
fdf01eed MD |
161 | } |
162 | #endif | |
163 | ||
02be5561 | 164 | #ifdef RCU_MB |
25cc6d18 | 165 | static void smp_mb_master(int group) |
40e140c9 | 166 | { |
5481ddb3 | 167 | cmm_smp_mb(); |
40e140c9 | 168 | } |
fdf01eed MD |
169 | #endif |
170 | ||
171 | #ifdef RCU_SIGNAL | |
78ff9419 | 172 | static void force_mb_all_readers(void) |
27b012e2 | 173 | { |
02be5561 | 174 | struct rcu_reader *index; |
e3b0cef0 | 175 | |
27b012e2 | 176 | /* |
5481ddb3 | 177 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
178 | * compiler barriers around rcu read lock as real memory barriers. |
179 | */ | |
16aa9ee8 | 180 | if (cds_list_empty(®istry)) |
27b012e2 | 181 | return; |
3a86deba | 182 | /* |
5481ddb3 | 183 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 184 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 185 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 186 | * cache flush is enforced. |
3a86deba | 187 | */ |
16aa9ee8 | 188 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 189 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 190 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 191 | } |
27b012e2 MD |
192 | /* |
193 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
194 | * |
195 | * Note that the pthread_kill() will never be executed on systems | |
196 | * that correctly deliver signals in a timely manner. However, it | |
197 | * is not uncommon for kernels to have bugs that can result in | |
198 | * lost or unduly delayed signals. | |
199 | * | |
200 | * If you are seeing the below pthread_kill() executing much at | |
201 | * all, we suggest testing the underlying kernel and filing the | |
202 | * relevant bug report. For Linux kernels, we recommend getting | |
203 | * the Linux Test Project (LTP). | |
27b012e2 | 204 | */ |
16aa9ee8 | 205 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 206 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 207 | pthread_kill(index->tid, SIGRCU); |
09a9f986 PM |
208 | poll(NULL, 0, 1); |
209 | } | |
210 | } | |
5481ddb3 | 211 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 212 | } |
9d7e3f89 | 213 | |
25cc6d18 | 214 | static void smp_mb_master(int group) |
9d7e3f89 MD |
215 | { |
216 | force_mb_all_readers(); | |
217 | } | |
fdf01eed | 218 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 219 | |
bc6c15bb MD |
220 | /* |
221 | * synchronize_rcu() waiting. Single thread. | |
222 | */ | |
cfe78e25 | 223 | static void wait_gp(void) |
bc6c15bb | 224 | { |
cfe78e25 | 225 | /* Read reader_gp before read futex */ |
25cc6d18 | 226 | smp_mb_master(RCU_MB_GROUP); |
11eb040f MD |
227 | if (uatomic_read(&gp_futex) != -1) |
228 | return; | |
229 | while (futex_async(&gp_futex, FUTEX_WAIT, -1, | |
230 | NULL, NULL, 0)) { | |
231 | switch (errno) { | |
232 | case EWOULDBLOCK: | |
233 | /* Value already changed. */ | |
234 | return; | |
235 | case EINTR: | |
236 | /* Retry if interrupted by signal. */ | |
237 | break; /* Get out of switch. */ | |
238 | default: | |
239 | /* Unexpected error. */ | |
240 | urcu_die(errno); | |
241 | } | |
242 | } | |
bc6c15bb MD |
243 | } |
244 | ||
66bc4dcd MD |
245 | /* |
246 | * Always called with rcu_registry lock held. Releases this lock between | |
247 | * iterations and grabs it again. Holds the lock when it returns. | |
248 | */ | |
2dfb8b5e | 249 | void update_counter_and_wait(void) |
27b012e2 | 250 | { |
16aa9ee8 | 251 | CDS_LIST_HEAD(qsreaders); |
6b702fa4 | 252 | unsigned int wait_loops = 0; |
02be5561 | 253 | struct rcu_reader *index, *tmp; |
6b702fa4 MD |
254 | #ifdef HAS_INCOHERENT_CACHES |
255 | unsigned int wait_gp_loops = 0; | |
256 | #endif /* HAS_INCOHERENT_CACHES */ | |
27b012e2 | 257 | |
32c15e4e | 258 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
6cf3827c | 259 | CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE); |
2dfb8b5e MD |
260 | |
261 | /* | |
d40fde2c MD |
262 | * Must commit rcu_gp_ctr update to memory before waiting for quiescent |
263 | * state. Failure to do so could result in the writer waiting forever | |
264 | * while new readers are always accessing data (no progress). Enforce | |
265 | * compiler-order of store to rcu_gp_ctr before load rcu_reader ctr. | |
2dfb8b5e | 266 | */ |
5481ddb3 | 267 | cmm_barrier(); |
2dfb8b5e MD |
268 | |
269 | /* | |
935b11ff | 270 | * |
5481ddb3 | 271 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
2dfb8b5e MD |
272 | * model easier to understand. It does not have a big performance impact |
273 | * anyway, given this is the write-side. | |
274 | */ | |
5481ddb3 | 275 | cmm_smp_mb(); |
2dfb8b5e | 276 | |
40e140c9 | 277 | /* |
bd252a04 | 278 | * Wait for each thread URCU_TLS(rcu_reader).ctr count to become 0. |
27b012e2 | 279 | */ |
cfe78e25 | 280 | for (;;) { |
cca4c8dc MD |
281 | if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) |
282 | wait_loops++; | |
6b702fa4 | 283 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 MD |
284 | uatomic_dec(&gp_futex); |
285 | /* Write futex before read reader_gp */ | |
25cc6d18 | 286 | smp_mb_master(RCU_MB_GROUP); |
cfe78e25 MD |
287 | } |
288 | ||
16aa9ee8 | 289 | cds_list_for_each_entry_safe(index, tmp, ®istry, node) { |
b95a001f | 290 | if (!rcu_gp_ongoing(&index->ctr)) |
16aa9ee8 | 291 | cds_list_move(&index->node, &qsreaders); |
cfe78e25 MD |
292 | } |
293 | ||
e8043c1b | 294 | #ifndef HAS_INCOHERENT_CACHES |
16aa9ee8 | 295 | if (cds_list_empty(®istry)) { |
6b702fa4 | 296 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 297 | /* Read reader_gp before write futex */ |
25cc6d18 | 298 | smp_mb_master(RCU_MB_GROUP); |
cfe78e25 | 299 | uatomic_set(&gp_futex, 0); |
bc6c15bb | 300 | } |
cfe78e25 MD |
301 | break; |
302 | } else { | |
66bc4dcd MD |
303 | /* Temporarily unlock the registry lock. */ |
304 | mutex_unlock(&rcu_registry_lock); | |
6b702fa4 | 305 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) |
cfe78e25 MD |
306 | wait_gp(); |
307 | else | |
06f22bdb | 308 | caa_cpu_relax(); |
66bc4dcd MD |
309 | /* Re-lock the registry lock before the next loop. */ |
310 | mutex_lock(&rcu_registry_lock); | |
bc6c15bb | 311 | } |
e8043c1b | 312 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 313 | /* |
40e140c9 | 314 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
315 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
316 | * for too long. | |
27b012e2 | 317 | */ |
16aa9ee8 | 318 | if (cds_list_empty(®istry)) { |
6b702fa4 | 319 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 320 | /* Read reader_gp before write futex */ |
25cc6d18 | 321 | smp_mb_master(RCU_MB_GROUP); |
cfe78e25 MD |
322 | uatomic_set(&gp_futex, 0); |
323 | } | |
324 | break; | |
325 | } else { | |
6b702fa4 | 326 | if (wait_gp_loops == KICK_READER_LOOPS) { |
25cc6d18 | 327 | smp_mb_master(RCU_MB_GROUP); |
6b702fa4 MD |
328 | wait_gp_loops = 0; |
329 | } | |
66bc4dcd MD |
330 | /* Temporarily unlock the registry lock. */ |
331 | mutex_unlock(&rcu_registry_lock); | |
6b702fa4 MD |
332 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
333 | wait_gp(); | |
334 | wait_gp_loops++; | |
335 | } else { | |
06f22bdb | 336 | caa_cpu_relax(); |
40e140c9 | 337 | } |
66bc4dcd MD |
338 | /* Re-lock the registry lock before the next loop. */ |
339 | mutex_lock(&rcu_registry_lock); | |
40e140c9 | 340 | } |
e8043c1b | 341 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 342 | } |
cfe78e25 | 343 | /* put back the reader list in the registry */ |
16aa9ee8 | 344 | cds_list_splice(&qsreaders, ®istry); |
27b012e2 MD |
345 | } |
346 | ||
9598a481 | 347 | void synchronize_rcu(void) |
2bc59bd7 | 348 | { |
6abb4bd5 | 349 | mutex_lock(&rcu_gp_lock); |
66bc4dcd | 350 | mutex_lock(&rcu_registry_lock); |
135530fd | 351 | |
16aa9ee8 | 352 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
353 | goto out; |
354 | ||
66bc4dcd MD |
355 | /* |
356 | * All threads should read qparity before accessing data structure | |
357 | * where new ptr points to. Must be done within rcu_registry_lock | |
358 | * because it iterates on reader threads. | |
359 | */ | |
9598a481 | 360 | /* Write new ptr before changing the qparity */ |
25cc6d18 | 361 | smp_mb_master(RCU_MB_GROUP); |
9598a481 | 362 | |
9598a481 MD |
363 | /* |
364 | * Wait for previous parity to be empty of readers. | |
66bc4dcd MD |
365 | * update_counter_and_wait() can release and grab again |
366 | * rcu_registry_lock interally. | |
9598a481 | 367 | */ |
2dfb8b5e | 368 | update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */ |
9598a481 MD |
369 | |
370 | /* | |
371 | * Must finish waiting for quiescent state for parity 0 before | |
d40fde2c MD |
372 | * committing next rcu_gp_ctr update to memory. Failure to do so could |
373 | * result in the writer waiting forever while new readers are always | |
374 | * accessing data (no progress). Enforce compiler-order of load | |
bd252a04 | 375 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp_ctr. |
9598a481 | 376 | */ |
5481ddb3 | 377 | cmm_barrier(); |
9598a481 | 378 | |
5dba80f9 | 379 | /* |
5481ddb3 | 380 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
381 | * model easier to understand. It does not have a big performance impact |
382 | * anyway, given this is the write-side. | |
383 | */ | |
5481ddb3 | 384 | cmm_smp_mb(); |
67c2d80b | 385 | |
9598a481 MD |
386 | /* |
387 | * Wait for previous parity to be empty of readers. | |
66bc4dcd MD |
388 | * update_counter_and_wait() can release and grab again |
389 | * rcu_registry_lock interally. | |
9598a481 | 390 | */ |
2dfb8b5e | 391 | update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */ |
9598a481 | 392 | |
66bc4dcd MD |
393 | /* |
394 | * Finish waiting for reader threads before letting the old ptr | |
395 | * being freed. Must be done within rcu_registry_lock because it | |
396 | * iterates on reader threads. | |
397 | */ | |
25cc6d18 | 398 | smp_mb_master(RCU_MB_GROUP); |
2dfb8b5e | 399 | out: |
66bc4dcd | 400 | mutex_unlock(&rcu_registry_lock); |
6abb4bd5 | 401 | mutex_unlock(&rcu_gp_lock); |
2bc59bd7 PM |
402 | } |
403 | ||
121a5d44 MD |
404 | /* |
405 | * library wrappers to be used by non-LGPL compatible source code. | |
406 | */ | |
407 | ||
408 | void rcu_read_lock(void) | |
409 | { | |
410 | _rcu_read_lock(); | |
411 | } | |
412 | ||
413 | void rcu_read_unlock(void) | |
414 | { | |
415 | _rcu_read_unlock(); | |
416 | } | |
417 | ||
121a5d44 | 418 | void rcu_register_thread(void) |
27b012e2 | 419 | { |
bd252a04 MD |
420 | URCU_TLS(rcu_reader).tid = pthread_self(); |
421 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
422 | assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); | |
02be5561 | 423 | |
66bc4dcd | 424 | mutex_lock(&rcu_registry_lock); |
02be5561 | 425 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 426 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
66bc4dcd | 427 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
428 | } |
429 | ||
121a5d44 | 430 | void rcu_unregister_thread(void) |
27b012e2 | 431 | { |
66bc4dcd | 432 | mutex_lock(&rcu_registry_lock); |
bd252a04 | 433 | cds_list_del(&URCU_TLS(rcu_reader).node); |
66bc4dcd | 434 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
435 | } |
436 | ||
fdf01eed MD |
437 | #ifdef RCU_MEMBARRIER |
438 | void rcu_init(void) | |
439 | { | |
440 | if (init_done) | |
441 | return; | |
442 | init_done = 1; | |
cf5271ee | 443 | if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY)) |
fdf01eed MD |
444 | has_sys_membarrier = 1; |
445 | } | |
446 | #endif | |
447 | ||
448 | #ifdef RCU_SIGNAL | |
02be5561 | 449 | static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) |
27b012e2 | 450 | { |
40e140c9 | 451 | /* |
5481ddb3 DG |
452 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
453 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
454 | * executed on. |
455 | */ | |
5481ddb3 | 456 | cmm_smp_mb(); |
bd252a04 | 457 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 458 | cmm_smp_mb(); |
27b012e2 MD |
459 | } |
460 | ||
8a5fb4c9 | 461 | /* |
02be5561 | 462 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
463 | * reader threads are calling rcu_register_thread(). |
464 | * Should only be called by a single thread at a given time. This is ensured by | |
66bc4dcd MD |
465 | * holing the rcu_registry_lock from rcu_register_thread() or by running |
466 | * at library load time, which should not be executed by multiple | |
467 | * threads nor concurrently with rcu_register_thread() anyway. | |
8a5fb4c9 | 468 | */ |
02be5561 | 469 | void rcu_init(void) |
27b012e2 MD |
470 | { |
471 | struct sigaction act; | |
472 | int ret; | |
473 | ||
8a5fb4c9 MD |
474 | if (init_done) |
475 | return; | |
476 | init_done = 1; | |
477 | ||
02be5561 | 478 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 479 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 480 | sigemptyset(&act.sa_mask); |
02be5561 | 481 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
482 | if (ret) |
483 | urcu_die(errno); | |
27b012e2 MD |
484 | } |
485 | ||
02be5561 | 486 | void rcu_exit(void) |
27b012e2 MD |
487 | { |
488 | struct sigaction act; | |
489 | int ret; | |
490 | ||
02be5561 | 491 | ret = sigaction(SIGRCU, NULL, &act); |
4a6d7378 MD |
492 | if (ret) |
493 | urcu_die(errno); | |
02be5561 | 494 | assert(act.sa_sigaction == sigrcu_handler); |
16aa9ee8 | 495 | assert(cds_list_empty(®istry)); |
27b012e2 | 496 | } |
5e77fc1f | 497 | |
fdf01eed | 498 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 499 | |
5e6b23a6 | 500 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 501 | |
5e77fc1f | 502 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 503 | #include "urcu-defer-impl.h" |