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 |
82d50e1a | 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 | |
d73fb81f | 40 | #include "urcu/wfcqueue.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 | 46 | #include "urcu-die.h" |
5bffdd5d | 47 | #include "urcu-wait.h" |
4a6d7378 | 48 | |
121a5d44 | 49 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
71c811bf | 50 | #undef _LGPL_SOURCE |
27b012e2 | 51 | #include "urcu.h" |
71c811bf | 52 | #define _LGPL_SOURCE |
27b012e2 | 53 | |
3a71751e PB |
54 | /* |
55 | * If a reader is really non-cooperative and refuses to commit its | |
56 | * rcu_active_readers count to memory (there is no barrier in the reader | |
9340c38d | 57 | * per-se), kick it after 10 loops waiting for it. |
3a71751e | 58 | */ |
9340c38d | 59 | #define KICK_READER_LOOPS 10 |
3a71751e PB |
60 | |
61 | /* | |
62 | * Active attempts to check for reader Q.S. before calling futex(). | |
63 | */ | |
64 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
65 | ||
553b7eb9 MD |
66 | /* |
67 | * RCU_MEMBARRIER is only possibly available on Linux. | |
68 | */ | |
69 | #if defined(RCU_MEMBARRIER) && defined(__linux__) | |
9ba261bd | 70 | #include <urcu/syscall-compat.h> |
553b7eb9 MD |
71 | #endif |
72 | ||
73 | /* If the headers do not support SYS_membarrier, fall back on RCU_MB */ | |
74 | #ifdef SYS_membarrier | |
75 | # define membarrier(...) syscall(SYS_membarrier, __VA_ARGS__) | |
76 | #else | |
77 | # define membarrier(...) -ENOSYS | |
78 | #endif | |
79 | ||
80 | #define MEMBARRIER_EXPEDITED (1 << 0) | |
81 | #define MEMBARRIER_DELAYED (1 << 1) | |
82 | #define MEMBARRIER_QUERY (1 << 16) | |
83 | ||
fdf01eed | 84 | #ifdef RCU_MEMBARRIER |
834a45ba | 85 | static int init_done; |
1de4df4b | 86 | int rcu_has_sys_membarrier; |
834a45ba | 87 | |
02be5561 | 88 | void __attribute__((constructor)) rcu_init(void); |
fdf01eed MD |
89 | #endif |
90 | ||
91 | #ifdef RCU_MB | |
02be5561 | 92 | void rcu_init(void) |
e90a6e9c MD |
93 | { |
94 | } | |
95 | #endif | |
8a5fb4c9 | 96 | |
fdf01eed MD |
97 | #ifdef RCU_SIGNAL |
98 | static int init_done; | |
99 | ||
100 | void __attribute__((constructor)) rcu_init(void); | |
101 | void __attribute__((destructor)) rcu_exit(void); | |
102 | #endif | |
103 | ||
731ccb96 MD |
104 | /* |
105 | * rcu_gp_lock ensures mutual exclusion between threads calling | |
106 | * synchronize_rcu(). | |
107 | */ | |
6abb4bd5 | 108 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
731ccb96 MD |
109 | /* |
110 | * rcu_registry_lock ensures mutual exclusion between threads | |
111 | * registering and unregistering themselves to/from the registry, and | |
112 | * with threads reading that registry from synchronize_rcu(). However, | |
113 | * this lock is not held all the way through the completion of awaiting | |
114 | * for the grace period. It is sporadically released between iterations | |
115 | * on the registry. | |
116 | * rcu_registry_lock may nest inside rcu_gp_lock. | |
117 | */ | |
118 | static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER; | |
4de0cd31 | 119 | struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT }; |
27b012e2 | 120 | |
b0d5e790 MD |
121 | /* |
122 | * Written to only by each individual reader. Read by both the reader and the | |
123 | * writers. | |
124 | */ | |
bd252a04 | 125 | DEFINE_URCU_TLS(struct rcu_reader, rcu_reader); |
27b012e2 | 126 | |
16aa9ee8 | 127 | static CDS_LIST_HEAD(registry); |
27b012e2 | 128 | |
5bffdd5d MD |
129 | /* |
130 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
131 | * struct gp_waiters_thread objects. | |
132 | */ | |
133 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
134 | ||
6abb4bd5 | 135 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
136 | { |
137 | int ret; | |
09a9f986 PM |
138 | |
139 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 140 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
141 | if (ret) |
142 | urcu_die(ret); | |
09a9f986 | 143 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 144 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
145 | if (ret != EBUSY && ret != EINTR) |
146 | urcu_die(ret); | |
bd252a04 | 147 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 148 | cmm_smp_mb(); |
bd252a04 | 149 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 150 | cmm_smp_mb(); |
09a9f986 | 151 | } |
8999a9ee | 152 | (void) poll(NULL, 0, 10); |
09a9f986 PM |
153 | } |
154 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
155 | } |
156 | ||
6abb4bd5 | 157 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
158 | { |
159 | int ret; | |
160 | ||
6abb4bd5 | 161 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
162 | if (ret) |
163 | urcu_die(ret); | |
41718ff9 MD |
164 | } |
165 | ||
fdf01eed | 166 | #ifdef RCU_MEMBARRIER |
25cc6d18 | 167 | static void smp_mb_master(int group) |
fdf01eed | 168 | { |
1de4df4b | 169 | if (caa_likely(rcu_has_sys_membarrier)) |
553b7eb9 | 170 | (void) membarrier(MEMBARRIER_EXPEDITED); |
fdf01eed | 171 | else |
5481ddb3 | 172 | cmm_smp_mb(); |
fdf01eed MD |
173 | } |
174 | #endif | |
175 | ||
02be5561 | 176 | #ifdef RCU_MB |
25cc6d18 | 177 | static void smp_mb_master(int group) |
40e140c9 | 178 | { |
5481ddb3 | 179 | cmm_smp_mb(); |
40e140c9 | 180 | } |
fdf01eed MD |
181 | #endif |
182 | ||
183 | #ifdef RCU_SIGNAL | |
78ff9419 | 184 | static void force_mb_all_readers(void) |
27b012e2 | 185 | { |
02be5561 | 186 | struct rcu_reader *index; |
e3b0cef0 | 187 | |
27b012e2 | 188 | /* |
5481ddb3 | 189 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
190 | * compiler barriers around rcu read lock as real memory barriers. |
191 | */ | |
16aa9ee8 | 192 | if (cds_list_empty(®istry)) |
27b012e2 | 193 | return; |
3a86deba | 194 | /* |
5481ddb3 | 195 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 196 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 197 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 198 | * cache flush is enforced. |
3a86deba | 199 | */ |
16aa9ee8 | 200 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 201 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 202 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 203 | } |
27b012e2 MD |
204 | /* |
205 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
206 | * |
207 | * Note that the pthread_kill() will never be executed on systems | |
208 | * that correctly deliver signals in a timely manner. However, it | |
209 | * is not uncommon for kernels to have bugs that can result in | |
210 | * lost or unduly delayed signals. | |
211 | * | |
212 | * If you are seeing the below pthread_kill() executing much at | |
213 | * all, we suggest testing the underlying kernel and filing the | |
214 | * relevant bug report. For Linux kernels, we recommend getting | |
215 | * the Linux Test Project (LTP). | |
27b012e2 | 216 | */ |
16aa9ee8 | 217 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 218 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 219 | pthread_kill(index->tid, SIGRCU); |
8999a9ee | 220 | (void) poll(NULL, 0, 1); |
09a9f986 PM |
221 | } |
222 | } | |
5481ddb3 | 223 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 224 | } |
9d7e3f89 | 225 | |
25cc6d18 | 226 | static void smp_mb_master(int group) |
9d7e3f89 MD |
227 | { |
228 | force_mb_all_readers(); | |
229 | } | |
fdf01eed | 230 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 231 | |
bc6c15bb MD |
232 | /* |
233 | * synchronize_rcu() waiting. Single thread. | |
234 | */ | |
cfe78e25 | 235 | static void wait_gp(void) |
bc6c15bb | 236 | { |
cfe78e25 | 237 | /* Read reader_gp before read futex */ |
25cc6d18 | 238 | smp_mb_master(RCU_MB_GROUP); |
b0a841b4 MD |
239 | if (uatomic_read(&rcu_gp.futex) != -1) |
240 | return; | |
241 | while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, | |
242 | NULL, NULL, 0)) { | |
243 | switch (errno) { | |
244 | case EWOULDBLOCK: | |
245 | /* Value already changed. */ | |
246 | return; | |
247 | case EINTR: | |
248 | /* Retry if interrupted by signal. */ | |
249 | break; /* Get out of switch. */ | |
250 | default: | |
251 | /* Unexpected error. */ | |
252 | urcu_die(errno); | |
253 | } | |
254 | } | |
bc6c15bb MD |
255 | } |
256 | ||
731ccb96 MD |
257 | /* |
258 | * Always called with rcu_registry lock held. Releases this lock between | |
259 | * iterations and grabs it again. Holds the lock when it returns. | |
260 | */ | |
fd189fa5 MD |
261 | static void wait_for_readers(struct cds_list_head *input_readers, |
262 | struct cds_list_head *cur_snap_readers, | |
263 | struct cds_list_head *qsreaders) | |
27b012e2 | 264 | { |
9340c38d | 265 | unsigned int wait_loops = 0; |
02be5561 | 266 | struct rcu_reader *index, *tmp; |
9340c38d MD |
267 | #ifdef HAS_INCOHERENT_CACHES |
268 | unsigned int wait_gp_loops = 0; | |
269 | #endif /* HAS_INCOHERENT_CACHES */ | |
27b012e2 | 270 | |
40e140c9 | 271 | /* |
c9488684 MD |
272 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
273 | * indicate quiescence (not nested), or observe the current | |
ed1b099e | 274 | * rcu_gp.ctr value. |
27b012e2 | 275 | */ |
cfe78e25 | 276 | for (;;) { |
5e81fed7 MD |
277 | if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) |
278 | wait_loops++; | |
9340c38d | 279 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
ed1b099e | 280 | uatomic_dec(&rcu_gp.futex); |
cfe78e25 | 281 | /* Write futex before read reader_gp */ |
25cc6d18 | 282 | smp_mb_master(RCU_MB_GROUP); |
cfe78e25 MD |
283 | } |
284 | ||
fd189fa5 MD |
285 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
286 | switch (rcu_reader_state(&index->ctr)) { | |
287 | case RCU_READER_ACTIVE_CURRENT: | |
288 | if (cur_snap_readers) { | |
289 | cds_list_move(&index->node, | |
290 | cur_snap_readers); | |
291 | break; | |
292 | } | |
293 | /* Fall-through */ | |
294 | case RCU_READER_INACTIVE: | |
295 | cds_list_move(&index->node, qsreaders); | |
296 | break; | |
297 | case RCU_READER_ACTIVE_OLD: | |
298 | /* | |
299 | * Old snapshot. Leaving node in | |
300 | * input_readers will make us busy-loop | |
301 | * until the snapshot becomes current or | |
302 | * the reader becomes inactive. | |
303 | */ | |
304 | break; | |
305 | } | |
cfe78e25 MD |
306 | } |
307 | ||
e8043c1b | 308 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 309 | if (cds_list_empty(input_readers)) { |
9340c38d | 310 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 311 | /* Read reader_gp before write futex */ |
25cc6d18 | 312 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e | 313 | uatomic_set(&rcu_gp.futex, 0); |
bc6c15bb | 314 | } |
cfe78e25 MD |
315 | break; |
316 | } else { | |
731ccb96 MD |
317 | /* Temporarily unlock the registry lock. */ |
318 | mutex_unlock(&rcu_registry_lock); | |
9340c38d | 319 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) |
cfe78e25 MD |
320 | wait_gp(); |
321 | else | |
06f22bdb | 322 | caa_cpu_relax(); |
731ccb96 MD |
323 | /* Re-lock the registry lock before the next loop. */ |
324 | mutex_lock(&rcu_registry_lock); | |
bc6c15bb | 325 | } |
e8043c1b | 326 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 327 | /* |
40e140c9 | 328 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
329 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
330 | * for too long. | |
27b012e2 | 331 | */ |
fd189fa5 | 332 | if (cds_list_empty(input_readers)) { |
9340c38d | 333 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 334 | /* Read reader_gp before write futex */ |
25cc6d18 | 335 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e | 336 | uatomic_set(&rcu_gp.futex, 0); |
cfe78e25 MD |
337 | } |
338 | break; | |
339 | } else { | |
9340c38d | 340 | if (wait_gp_loops == KICK_READER_LOOPS) { |
25cc6d18 | 341 | smp_mb_master(RCU_MB_GROUP); |
9340c38d MD |
342 | wait_gp_loops = 0; |
343 | } | |
731ccb96 MD |
344 | /* Temporarily unlock the registry lock. */ |
345 | mutex_unlock(&rcu_registry_lock); | |
9340c38d MD |
346 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
347 | wait_gp(); | |
348 | wait_gp_loops++; | |
349 | } else { | |
06f22bdb | 350 | caa_cpu_relax(); |
40e140c9 | 351 | } |
731ccb96 MD |
352 | /* Re-lock the registry lock before the next loop. */ |
353 | mutex_lock(&rcu_registry_lock); | |
40e140c9 | 354 | } |
e8043c1b | 355 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 356 | } |
27b012e2 MD |
357 | } |
358 | ||
9598a481 | 359 | void synchronize_rcu(void) |
2bc59bd7 | 360 | { |
fd189fa5 MD |
361 | CDS_LIST_HEAD(cur_snap_readers); |
362 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
363 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
364 | struct urcu_waiters waiters; | |
365 | ||
366 | /* | |
367 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
368 | * for a grace period. Proceed to perform the grace period only | |
369 | * if we are the first thread added into the queue. | |
370 | * The implicit memory barrier before urcu_wait_add() | |
371 | * orders prior memory accesses of threads put into the wait | |
372 | * queue before their insertion into the wait queue. | |
373 | */ | |
374 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
375 | /* Not first in queue: will be awakened by another thread. */ | |
376 | urcu_adaptative_busy_wait(&wait); | |
377 | /* Order following memory accesses after grace period. */ | |
378 | cmm_smp_mb(); | |
379 | return; | |
380 | } | |
381 | /* We won't need to wake ourself up */ | |
382 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 383 | |
6abb4bd5 | 384 | mutex_lock(&rcu_gp_lock); |
135530fd | 385 | |
5bffdd5d MD |
386 | /* |
387 | * Move all waiters into our local queue. | |
388 | */ | |
389 | urcu_move_waiters(&waiters, &gp_waiters); | |
390 | ||
731ccb96 MD |
391 | mutex_lock(&rcu_registry_lock); |
392 | ||
16aa9ee8 | 393 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
394 | goto out; |
395 | ||
731ccb96 MD |
396 | /* |
397 | * All threads should read qparity before accessing data structure | |
398 | * where new ptr points to. Must be done within rcu_registry_lock | |
399 | * because it iterates on reader threads. | |
400 | */ | |
9598a481 | 401 | /* Write new ptr before changing the qparity */ |
25cc6d18 | 402 | smp_mb_master(RCU_MB_GROUP); |
9598a481 | 403 | |
9598a481 | 404 | /* |
c9488684 | 405 | * Wait for readers to observe original parity or be quiescent. |
731ccb96 MD |
406 | * wait_for_readers() can release and grab again rcu_registry_lock |
407 | * interally. | |
9598a481 | 408 | */ |
fd189fa5 | 409 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
410 | |
411 | /* | |
c9488684 | 412 | * Must finish waiting for quiescent state for original parity before |
ed1b099e | 413 | * committing next rcu_gp.ctr update to memory. Failure to do so could |
d40fde2c MD |
414 | * result in the writer waiting forever while new readers are always |
415 | * accessing data (no progress). Enforce compiler-order of load | |
ed1b099e | 416 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr. |
9598a481 | 417 | */ |
5481ddb3 | 418 | cmm_barrier(); |
9598a481 | 419 | |
5dba80f9 | 420 | /* |
5481ddb3 | 421 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
422 | * model easier to understand. It does not have a big performance impact |
423 | * anyway, given this is the write-side. | |
424 | */ | |
5481ddb3 | 425 | cmm_smp_mb(); |
67c2d80b | 426 | |
c9488684 | 427 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
ed1b099e | 428 | CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE); |
c9488684 MD |
429 | |
430 | /* | |
ed1b099e | 431 | * Must commit rcu_gp.ctr update to memory before waiting for quiescent |
c9488684 MD |
432 | * state. Failure to do so could result in the writer waiting forever |
433 | * while new readers are always accessing data (no progress). Enforce | |
ed1b099e | 434 | * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr. |
c9488684 MD |
435 | */ |
436 | cmm_barrier(); | |
437 | ||
438 | /* | |
439 | * | |
440 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
441 | * model easier to understand. It does not have a big performance impact | |
442 | * anyway, given this is the write-side. | |
443 | */ | |
444 | cmm_smp_mb(); | |
445 | ||
9598a481 | 446 | /* |
c9488684 | 447 | * Wait for readers to observe new parity or be quiescent. |
731ccb96 MD |
448 | * wait_for_readers() can release and grab again rcu_registry_lock |
449 | * interally. | |
9598a481 | 450 | */ |
fd189fa5 MD |
451 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
452 | ||
453 | /* | |
454 | * Put quiescent reader list back into registry. | |
455 | */ | |
456 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 457 | |
731ccb96 MD |
458 | /* |
459 | * Finish waiting for reader threads before letting the old ptr | |
460 | * being freed. Must be done within rcu_registry_lock because it | |
461 | * iterates on reader threads. | |
462 | */ | |
25cc6d18 | 463 | smp_mb_master(RCU_MB_GROUP); |
2dfb8b5e | 464 | out: |
731ccb96 | 465 | mutex_unlock(&rcu_registry_lock); |
6abb4bd5 | 466 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
467 | |
468 | /* | |
469 | * Wakeup waiters only after we have completed the grace period | |
470 | * and have ensured the memory barriers at the end of the grace | |
471 | * period have been issued. | |
472 | */ | |
473 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 PM |
474 | } |
475 | ||
121a5d44 MD |
476 | /* |
477 | * library wrappers to be used by non-LGPL compatible source code. | |
478 | */ | |
479 | ||
480 | void rcu_read_lock(void) | |
481 | { | |
482 | _rcu_read_lock(); | |
483 | } | |
484 | ||
485 | void rcu_read_unlock(void) | |
486 | { | |
487 | _rcu_read_unlock(); | |
488 | } | |
489 | ||
882f3357 MD |
490 | int rcu_read_ongoing(void) |
491 | { | |
492 | return _rcu_read_ongoing(); | |
493 | } | |
494 | ||
121a5d44 | 495 | void rcu_register_thread(void) |
27b012e2 | 496 | { |
bd252a04 MD |
497 | URCU_TLS(rcu_reader).tid = pthread_self(); |
498 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
499 | assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); | |
02be5561 | 500 | |
731ccb96 | 501 | mutex_lock(&rcu_registry_lock); |
02be5561 | 502 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 503 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
731ccb96 | 504 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
505 | } |
506 | ||
121a5d44 | 507 | void rcu_unregister_thread(void) |
27b012e2 | 508 | { |
731ccb96 | 509 | mutex_lock(&rcu_registry_lock); |
bd252a04 | 510 | cds_list_del(&URCU_TLS(rcu_reader).node); |
731ccb96 | 511 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
512 | } |
513 | ||
fdf01eed MD |
514 | #ifdef RCU_MEMBARRIER |
515 | void rcu_init(void) | |
516 | { | |
517 | if (init_done) | |
518 | return; | |
519 | init_done = 1; | |
cf5271ee | 520 | if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY)) |
1de4df4b | 521 | rcu_has_sys_membarrier = 1; |
fdf01eed MD |
522 | } |
523 | #endif | |
524 | ||
525 | #ifdef RCU_SIGNAL | |
02be5561 | 526 | static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) |
27b012e2 | 527 | { |
40e140c9 | 528 | /* |
5481ddb3 DG |
529 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
530 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
531 | * executed on. |
532 | */ | |
5481ddb3 | 533 | cmm_smp_mb(); |
bd252a04 | 534 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 535 | cmm_smp_mb(); |
27b012e2 MD |
536 | } |
537 | ||
8a5fb4c9 | 538 | /* |
02be5561 | 539 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
540 | * reader threads are calling rcu_register_thread(). |
541 | * Should only be called by a single thread at a given time. This is ensured by | |
731ccb96 MD |
542 | * holing the rcu_registry_lock from rcu_register_thread() or by running |
543 | * at library load time, which should not be executed by multiple | |
544 | * threads nor concurrently with rcu_register_thread() anyway. | |
8a5fb4c9 | 545 | */ |
02be5561 | 546 | void rcu_init(void) |
27b012e2 MD |
547 | { |
548 | struct sigaction act; | |
549 | int ret; | |
550 | ||
8a5fb4c9 MD |
551 | if (init_done) |
552 | return; | |
553 | init_done = 1; | |
554 | ||
02be5561 | 555 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 556 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 557 | sigemptyset(&act.sa_mask); |
02be5561 | 558 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
559 | if (ret) |
560 | urcu_die(errno); | |
27b012e2 MD |
561 | } |
562 | ||
02be5561 | 563 | void rcu_exit(void) |
27b012e2 | 564 | { |
71210954 MD |
565 | /* |
566 | * Don't unregister the SIGRCU signal handler anymore, because | |
567 | * call_rcu threads could still be using it shortly before the | |
568 | * application exits. | |
569 | * Assertion disabled because call_rcu threads are now rcu | |
570 | * readers, and left running at exit. | |
571 | * assert(cds_list_empty(®istry)); | |
572 | */ | |
27b012e2 | 573 | } |
5e77fc1f | 574 | |
fdf01eed | 575 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 576 | |
5e6b23a6 | 577 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 578 | |
5e77fc1f | 579 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 580 | #include "urcu-defer-impl.h" |