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 |
71c811bf | 27 | #define _LGPL_SOURCE |
82d50e1a | 28 | #define _DEFAULT_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 | |
999991c6 | 39 | #include "urcu/arch.h" |
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 | ||
999991c6 MD |
66 | /* If the headers do not support membarrier system call, fall back on RCU_MB */ |
67 | #ifdef __NR_membarrier | |
68 | # define membarrier(...) syscall(__NR_membarrier, __VA_ARGS__) | |
553b7eb9 MD |
69 | #else |
70 | # define membarrier(...) -ENOSYS | |
71 | #endif | |
72 | ||
64f469e6 MD |
73 | enum membarrier_cmd { |
74 | MEMBARRIER_CMD_QUERY = 0, | |
75 | MEMBARRIER_CMD_SHARED = (1 << 0), | |
76 | }; | |
553b7eb9 | 77 | |
fdf01eed | 78 | #ifdef RCU_MEMBARRIER |
834a45ba | 79 | static int init_done; |
1de4df4b | 80 | int rcu_has_sys_membarrier; |
834a45ba | 81 | |
02be5561 | 82 | void __attribute__((constructor)) rcu_init(void); |
fdf01eed MD |
83 | #endif |
84 | ||
85 | #ifdef RCU_MB | |
02be5561 | 86 | void rcu_init(void) |
e90a6e9c MD |
87 | { |
88 | } | |
89 | #endif | |
8a5fb4c9 | 90 | |
fdf01eed MD |
91 | #ifdef RCU_SIGNAL |
92 | static int init_done; | |
93 | ||
94 | void __attribute__((constructor)) rcu_init(void); | |
95 | void __attribute__((destructor)) rcu_exit(void); | |
96 | #endif | |
97 | ||
731ccb96 MD |
98 | /* |
99 | * rcu_gp_lock ensures mutual exclusion between threads calling | |
100 | * synchronize_rcu(). | |
101 | */ | |
6abb4bd5 | 102 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
731ccb96 MD |
103 | /* |
104 | * rcu_registry_lock ensures mutual exclusion between threads | |
105 | * registering and unregistering themselves to/from the registry, and | |
106 | * with threads reading that registry from synchronize_rcu(). However, | |
107 | * this lock is not held all the way through the completion of awaiting | |
108 | * for the grace period. It is sporadically released between iterations | |
109 | * on the registry. | |
110 | * rcu_registry_lock may nest inside rcu_gp_lock. | |
111 | */ | |
112 | static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER; | |
4de0cd31 | 113 | struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT }; |
27b012e2 | 114 | |
b0d5e790 MD |
115 | /* |
116 | * Written to only by each individual reader. Read by both the reader and the | |
117 | * writers. | |
118 | */ | |
bd252a04 | 119 | DEFINE_URCU_TLS(struct rcu_reader, rcu_reader); |
27b012e2 | 120 | |
16aa9ee8 | 121 | static CDS_LIST_HEAD(registry); |
27b012e2 | 122 | |
5bffdd5d MD |
123 | /* |
124 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
125 | * struct gp_waiters_thread objects. | |
126 | */ | |
127 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
128 | ||
6abb4bd5 | 129 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
130 | { |
131 | int ret; | |
09a9f986 PM |
132 | |
133 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 134 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
135 | if (ret) |
136 | urcu_die(ret); | |
09a9f986 | 137 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 138 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
139 | if (ret != EBUSY && ret != EINTR) |
140 | urcu_die(ret); | |
bd252a04 | 141 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 142 | cmm_smp_mb(); |
bd252a04 | 143 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 144 | cmm_smp_mb(); |
09a9f986 | 145 | } |
8999a9ee | 146 | (void) poll(NULL, 0, 10); |
09a9f986 PM |
147 | } |
148 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
149 | } |
150 | ||
6abb4bd5 | 151 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
152 | { |
153 | int ret; | |
154 | ||
6abb4bd5 | 155 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
156 | if (ret) |
157 | urcu_die(ret); | |
41718ff9 MD |
158 | } |
159 | ||
fdf01eed | 160 | #ifdef RCU_MEMBARRIER |
a4922ed9 | 161 | static void smp_mb_master(void) |
fdf01eed | 162 | { |
1de4df4b | 163 | if (caa_likely(rcu_has_sys_membarrier)) |
64f469e6 | 164 | (void) membarrier(MEMBARRIER_CMD_SHARED, 0); |
fdf01eed | 165 | else |
5481ddb3 | 166 | cmm_smp_mb(); |
fdf01eed MD |
167 | } |
168 | #endif | |
169 | ||
02be5561 | 170 | #ifdef RCU_MB |
a4922ed9 | 171 | static void smp_mb_master(void) |
40e140c9 | 172 | { |
5481ddb3 | 173 | cmm_smp_mb(); |
40e140c9 | 174 | } |
fdf01eed MD |
175 | #endif |
176 | ||
177 | #ifdef RCU_SIGNAL | |
78ff9419 | 178 | static void force_mb_all_readers(void) |
27b012e2 | 179 | { |
02be5561 | 180 | struct rcu_reader *index; |
e3b0cef0 | 181 | |
27b012e2 | 182 | /* |
5481ddb3 | 183 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
184 | * compiler barriers around rcu read lock as real memory barriers. |
185 | */ | |
16aa9ee8 | 186 | if (cds_list_empty(®istry)) |
27b012e2 | 187 | return; |
3a86deba | 188 | /* |
5481ddb3 | 189 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 190 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 191 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 192 | * cache flush is enforced. |
3a86deba | 193 | */ |
16aa9ee8 | 194 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 195 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 196 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 197 | } |
27b012e2 MD |
198 | /* |
199 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
200 | * |
201 | * Note that the pthread_kill() will never be executed on systems | |
202 | * that correctly deliver signals in a timely manner. However, it | |
203 | * is not uncommon for kernels to have bugs that can result in | |
204 | * lost or unduly delayed signals. | |
205 | * | |
206 | * If you are seeing the below pthread_kill() executing much at | |
207 | * all, we suggest testing the underlying kernel and filing the | |
208 | * relevant bug report. For Linux kernels, we recommend getting | |
209 | * the Linux Test Project (LTP). | |
27b012e2 | 210 | */ |
16aa9ee8 | 211 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 212 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 213 | pthread_kill(index->tid, SIGRCU); |
8999a9ee | 214 | (void) poll(NULL, 0, 1); |
09a9f986 PM |
215 | } |
216 | } | |
5481ddb3 | 217 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 218 | } |
9d7e3f89 | 219 | |
a4922ed9 | 220 | static void smp_mb_master(void) |
9d7e3f89 MD |
221 | { |
222 | force_mb_all_readers(); | |
223 | } | |
fdf01eed | 224 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 225 | |
bc6c15bb MD |
226 | /* |
227 | * synchronize_rcu() waiting. Single thread. | |
fca9fb96 MD |
228 | * Always called with rcu_registry lock held. Releases this lock and |
229 | * grabs it again. Holds the lock when it returns. | |
bc6c15bb | 230 | */ |
cfe78e25 | 231 | static void wait_gp(void) |
bc6c15bb | 232 | { |
fca9fb96 MD |
233 | /* |
234 | * Read reader_gp before read futex. smp_mb_master() needs to | |
235 | * be called with the rcu registry lock held in RCU_SIGNAL | |
236 | * flavor. | |
237 | */ | |
a4922ed9 | 238 | smp_mb_master(); |
fca9fb96 MD |
239 | /* Temporarily unlock the registry lock. */ |
240 | mutex_unlock(&rcu_registry_lock); | |
b0a841b4 | 241 | if (uatomic_read(&rcu_gp.futex) != -1) |
fca9fb96 | 242 | goto end; |
b0a841b4 MD |
243 | while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, |
244 | NULL, NULL, 0)) { | |
245 | switch (errno) { | |
246 | case EWOULDBLOCK: | |
247 | /* Value already changed. */ | |
fca9fb96 | 248 | goto end; |
b0a841b4 MD |
249 | case EINTR: |
250 | /* Retry if interrupted by signal. */ | |
251 | break; /* Get out of switch. */ | |
252 | default: | |
253 | /* Unexpected error. */ | |
254 | urcu_die(errno); | |
255 | } | |
256 | } | |
fca9fb96 MD |
257 | end: |
258 | /* | |
259 | * Re-lock the registry lock before the next loop. | |
260 | */ | |
261 | mutex_lock(&rcu_registry_lock); | |
bc6c15bb MD |
262 | } |
263 | ||
731ccb96 MD |
264 | /* |
265 | * Always called with rcu_registry lock held. Releases this lock between | |
266 | * iterations and grabs it again. Holds the lock when it returns. | |
267 | */ | |
fd189fa5 MD |
268 | static void wait_for_readers(struct cds_list_head *input_readers, |
269 | struct cds_list_head *cur_snap_readers, | |
270 | struct cds_list_head *qsreaders) | |
27b012e2 | 271 | { |
9340c38d | 272 | unsigned int wait_loops = 0; |
02be5561 | 273 | struct rcu_reader *index, *tmp; |
9340c38d MD |
274 | #ifdef HAS_INCOHERENT_CACHES |
275 | unsigned int wait_gp_loops = 0; | |
276 | #endif /* HAS_INCOHERENT_CACHES */ | |
27b012e2 | 277 | |
40e140c9 | 278 | /* |
c9488684 MD |
279 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
280 | * indicate quiescence (not nested), or observe the current | |
ed1b099e | 281 | * rcu_gp.ctr value. |
27b012e2 | 282 | */ |
cfe78e25 | 283 | for (;;) { |
5e81fed7 MD |
284 | if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) |
285 | wait_loops++; | |
9340c38d | 286 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
ed1b099e | 287 | uatomic_dec(&rcu_gp.futex); |
cfe78e25 | 288 | /* Write futex before read reader_gp */ |
a4922ed9 | 289 | smp_mb_master(); |
cfe78e25 MD |
290 | } |
291 | ||
fd189fa5 MD |
292 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
293 | switch (rcu_reader_state(&index->ctr)) { | |
294 | case RCU_READER_ACTIVE_CURRENT: | |
295 | if (cur_snap_readers) { | |
296 | cds_list_move(&index->node, | |
297 | cur_snap_readers); | |
298 | break; | |
299 | } | |
300 | /* Fall-through */ | |
301 | case RCU_READER_INACTIVE: | |
302 | cds_list_move(&index->node, qsreaders); | |
303 | break; | |
304 | case RCU_READER_ACTIVE_OLD: | |
305 | /* | |
306 | * Old snapshot. Leaving node in | |
307 | * input_readers will make us busy-loop | |
308 | * until the snapshot becomes current or | |
309 | * the reader becomes inactive. | |
310 | */ | |
311 | break; | |
312 | } | |
cfe78e25 MD |
313 | } |
314 | ||
e8043c1b | 315 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 316 | if (cds_list_empty(input_readers)) { |
9340c38d | 317 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 318 | /* Read reader_gp before write futex */ |
a4922ed9 | 319 | smp_mb_master(); |
ed1b099e | 320 | uatomic_set(&rcu_gp.futex, 0); |
bc6c15bb | 321 | } |
cfe78e25 MD |
322 | break; |
323 | } else { | |
fca9fb96 MD |
324 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
325 | /* wait_gp unlocks/locks registry lock. */ | |
cfe78e25 | 326 | wait_gp(); |
fca9fb96 MD |
327 | } else { |
328 | /* Temporarily unlock the registry lock. */ | |
329 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 330 | caa_cpu_relax(); |
fca9fb96 MD |
331 | /* |
332 | * Re-lock the registry lock before the | |
333 | * next loop. | |
334 | */ | |
335 | mutex_lock(&rcu_registry_lock); | |
336 | } | |
bc6c15bb | 337 | } |
e8043c1b | 338 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 339 | /* |
40e140c9 | 340 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
341 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
342 | * for too long. | |
27b012e2 | 343 | */ |
fd189fa5 | 344 | if (cds_list_empty(input_readers)) { |
9340c38d | 345 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 346 | /* Read reader_gp before write futex */ |
a4922ed9 | 347 | smp_mb_master(); |
ed1b099e | 348 | uatomic_set(&rcu_gp.futex, 0); |
cfe78e25 MD |
349 | } |
350 | break; | |
351 | } else { | |
9340c38d | 352 | if (wait_gp_loops == KICK_READER_LOOPS) { |
a4922ed9 | 353 | smp_mb_master(); |
9340c38d MD |
354 | wait_gp_loops = 0; |
355 | } | |
356 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { | |
fca9fb96 | 357 | /* wait_gp unlocks/locks registry lock. */ |
9340c38d MD |
358 | wait_gp(); |
359 | wait_gp_loops++; | |
360 | } else { | |
fca9fb96 MD |
361 | /* Temporarily unlock the registry lock. */ |
362 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 363 | caa_cpu_relax(); |
fca9fb96 MD |
364 | /* |
365 | * Re-lock the registry lock before the | |
366 | * next loop. | |
367 | */ | |
368 | mutex_lock(&rcu_registry_lock); | |
40e140c9 MD |
369 | } |
370 | } | |
e8043c1b | 371 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 372 | } |
27b012e2 MD |
373 | } |
374 | ||
9598a481 | 375 | void synchronize_rcu(void) |
2bc59bd7 | 376 | { |
fd189fa5 MD |
377 | CDS_LIST_HEAD(cur_snap_readers); |
378 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
379 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
380 | struct urcu_waiters waiters; | |
381 | ||
382 | /* | |
383 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
384 | * for a grace period. Proceed to perform the grace period only | |
385 | * if we are the first thread added into the queue. | |
386 | * The implicit memory barrier before urcu_wait_add() | |
387 | * orders prior memory accesses of threads put into the wait | |
388 | * queue before their insertion into the wait queue. | |
389 | */ | |
390 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
391 | /* Not first in queue: will be awakened by another thread. */ | |
392 | urcu_adaptative_busy_wait(&wait); | |
393 | /* Order following memory accesses after grace period. */ | |
394 | cmm_smp_mb(); | |
395 | return; | |
396 | } | |
397 | /* We won't need to wake ourself up */ | |
398 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 399 | |
6abb4bd5 | 400 | mutex_lock(&rcu_gp_lock); |
135530fd | 401 | |
5bffdd5d MD |
402 | /* |
403 | * Move all waiters into our local queue. | |
404 | */ | |
405 | urcu_move_waiters(&waiters, &gp_waiters); | |
406 | ||
731ccb96 MD |
407 | mutex_lock(&rcu_registry_lock); |
408 | ||
16aa9ee8 | 409 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
410 | goto out; |
411 | ||
731ccb96 MD |
412 | /* |
413 | * All threads should read qparity before accessing data structure | |
414 | * where new ptr points to. Must be done within rcu_registry_lock | |
415 | * because it iterates on reader threads. | |
416 | */ | |
9598a481 | 417 | /* Write new ptr before changing the qparity */ |
a4922ed9 | 418 | smp_mb_master(); |
9598a481 | 419 | |
9598a481 | 420 | /* |
c9488684 | 421 | * Wait for readers to observe original parity or be quiescent. |
731ccb96 MD |
422 | * wait_for_readers() can release and grab again rcu_registry_lock |
423 | * interally. | |
9598a481 | 424 | */ |
fd189fa5 | 425 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
426 | |
427 | /* | |
c9488684 | 428 | * Must finish waiting for quiescent state for original parity before |
ed1b099e | 429 | * committing next rcu_gp.ctr update to memory. Failure to do so could |
d40fde2c MD |
430 | * result in the writer waiting forever while new readers are always |
431 | * accessing data (no progress). Enforce compiler-order of load | |
ed1b099e | 432 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr. |
9598a481 | 433 | */ |
5481ddb3 | 434 | cmm_barrier(); |
9598a481 | 435 | |
5dba80f9 | 436 | /* |
5481ddb3 | 437 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
438 | * model easier to understand. It does not have a big performance impact |
439 | * anyway, given this is the write-side. | |
440 | */ | |
5481ddb3 | 441 | cmm_smp_mb(); |
67c2d80b | 442 | |
c9488684 | 443 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
ed1b099e | 444 | CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE); |
c9488684 MD |
445 | |
446 | /* | |
ed1b099e | 447 | * Must commit rcu_gp.ctr update to memory before waiting for quiescent |
c9488684 MD |
448 | * state. Failure to do so could result in the writer waiting forever |
449 | * while new readers are always accessing data (no progress). Enforce | |
ed1b099e | 450 | * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr. |
c9488684 MD |
451 | */ |
452 | cmm_barrier(); | |
453 | ||
454 | /* | |
455 | * | |
456 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
457 | * model easier to understand. It does not have a big performance impact | |
458 | * anyway, given this is the write-side. | |
459 | */ | |
460 | cmm_smp_mb(); | |
461 | ||
9598a481 | 462 | /* |
c9488684 | 463 | * Wait for readers to observe new parity or be quiescent. |
731ccb96 MD |
464 | * wait_for_readers() can release and grab again rcu_registry_lock |
465 | * interally. | |
9598a481 | 466 | */ |
fd189fa5 MD |
467 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
468 | ||
469 | /* | |
470 | * Put quiescent reader list back into registry. | |
471 | */ | |
472 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 473 | |
731ccb96 MD |
474 | /* |
475 | * Finish waiting for reader threads before letting the old ptr | |
476 | * being freed. Must be done within rcu_registry_lock because it | |
477 | * iterates on reader threads. | |
478 | */ | |
a4922ed9 | 479 | smp_mb_master(); |
2dfb8b5e | 480 | out: |
731ccb96 | 481 | mutex_unlock(&rcu_registry_lock); |
6abb4bd5 | 482 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
483 | |
484 | /* | |
485 | * Wakeup waiters only after we have completed the grace period | |
486 | * and have ensured the memory barriers at the end of the grace | |
487 | * period have been issued. | |
488 | */ | |
489 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 PM |
490 | } |
491 | ||
121a5d44 MD |
492 | /* |
493 | * library wrappers to be used by non-LGPL compatible source code. | |
494 | */ | |
495 | ||
496 | void rcu_read_lock(void) | |
497 | { | |
498 | _rcu_read_lock(); | |
499 | } | |
500 | ||
501 | void rcu_read_unlock(void) | |
502 | { | |
503 | _rcu_read_unlock(); | |
504 | } | |
505 | ||
882f3357 MD |
506 | int rcu_read_ongoing(void) |
507 | { | |
508 | return _rcu_read_ongoing(); | |
509 | } | |
510 | ||
121a5d44 | 511 | void rcu_register_thread(void) |
27b012e2 | 512 | { |
bd252a04 MD |
513 | URCU_TLS(rcu_reader).tid = pthread_self(); |
514 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
515 | assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); | |
02be5561 | 516 | |
731ccb96 | 517 | mutex_lock(&rcu_registry_lock); |
a77f7d82 MD |
518 | assert(!URCU_TLS(rcu_reader).registered); |
519 | URCU_TLS(rcu_reader).registered = 1; | |
02be5561 | 520 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 521 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
731ccb96 | 522 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
523 | } |
524 | ||
121a5d44 | 525 | void rcu_unregister_thread(void) |
27b012e2 | 526 | { |
731ccb96 | 527 | mutex_lock(&rcu_registry_lock); |
a77f7d82 MD |
528 | assert(URCU_TLS(rcu_reader).registered); |
529 | URCU_TLS(rcu_reader).registered = 0; | |
bd252a04 | 530 | cds_list_del(&URCU_TLS(rcu_reader).node); |
731ccb96 | 531 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
532 | } |
533 | ||
fdf01eed MD |
534 | #ifdef RCU_MEMBARRIER |
535 | void rcu_init(void) | |
536 | { | |
64f469e6 MD |
537 | int ret; |
538 | ||
fdf01eed MD |
539 | if (init_done) |
540 | return; | |
541 | init_done = 1; | |
64f469e6 MD |
542 | ret = membarrier(MEMBARRIER_CMD_QUERY, 0); |
543 | if (ret >= 0 && (ret & MEMBARRIER_CMD_SHARED)) { | |
1de4df4b | 544 | rcu_has_sys_membarrier = 1; |
64f469e6 | 545 | } |
fdf01eed MD |
546 | } |
547 | #endif | |
548 | ||
549 | #ifdef RCU_SIGNAL | |
02be5561 | 550 | static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) |
27b012e2 | 551 | { |
40e140c9 | 552 | /* |
5481ddb3 DG |
553 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
554 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
555 | * executed on. |
556 | */ | |
5481ddb3 | 557 | cmm_smp_mb(); |
bd252a04 | 558 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 559 | cmm_smp_mb(); |
27b012e2 MD |
560 | } |
561 | ||
8a5fb4c9 | 562 | /* |
02be5561 | 563 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
564 | * reader threads are calling rcu_register_thread(). |
565 | * Should only be called by a single thread at a given time. This is ensured by | |
731ccb96 MD |
566 | * holing the rcu_registry_lock from rcu_register_thread() or by running |
567 | * at library load time, which should not be executed by multiple | |
568 | * threads nor concurrently with rcu_register_thread() anyway. | |
8a5fb4c9 | 569 | */ |
02be5561 | 570 | void rcu_init(void) |
27b012e2 MD |
571 | { |
572 | struct sigaction act; | |
573 | int ret; | |
574 | ||
8a5fb4c9 MD |
575 | if (init_done) |
576 | return; | |
577 | init_done = 1; | |
578 | ||
02be5561 | 579 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 580 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 581 | sigemptyset(&act.sa_mask); |
02be5561 | 582 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
583 | if (ret) |
584 | urcu_die(errno); | |
27b012e2 MD |
585 | } |
586 | ||
02be5561 | 587 | void rcu_exit(void) |
27b012e2 | 588 | { |
71210954 MD |
589 | /* |
590 | * Don't unregister the SIGRCU signal handler anymore, because | |
591 | * call_rcu threads could still be using it shortly before the | |
592 | * application exits. | |
593 | * Assertion disabled because call_rcu threads are now rcu | |
594 | * readers, and left running at exit. | |
595 | * assert(cds_list_empty(®istry)); | |
596 | */ | |
27b012e2 | 597 | } |
5e77fc1f | 598 | |
fdf01eed | 599 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 600 | |
5e6b23a6 | 601 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 602 | |
5e77fc1f | 603 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 604 | #include "urcu-defer-impl.h" |