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 | ||
e37faee1 | 26 | #define URCU_NO_COMPAT_IDENTIFIERS |
fdf01eed | 27 | #define _BSD_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> |
c0bb9f69 | 38 | #include <stdbool.h> |
e8043c1b | 39 | #include <poll.h> |
27b012e2 | 40 | |
c6bc6503 | 41 | #include <urcu/config.h> |
4477a870 MD |
42 | #include <urcu/arch.h> |
43 | #include <urcu/wfcqueue.h> | |
44 | #include <urcu/map/urcu.h> | |
45 | #include <urcu/static/urcu.h> | |
46 | #include <urcu/pointer.h> | |
47 | #include <urcu/tls-compat.h> | |
71c811bf | 48 | |
4a6d7378 | 49 | #include "urcu-die.h" |
5bffdd5d | 50 | #include "urcu-wait.h" |
4477a870 | 51 | #include "urcu-utils.h" |
4a6d7378 | 52 | |
4477a870 | 53 | #define URCU_API_MAP |
121a5d44 | 54 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
71c811bf | 55 | #undef _LGPL_SOURCE |
4477a870 | 56 | #include <urcu/urcu.h> |
71c811bf | 57 | #define _LGPL_SOURCE |
27b012e2 | 58 | |
3a71751e PB |
59 | /* |
60 | * If a reader is really non-cooperative and refuses to commit its | |
61 | * rcu_active_readers count to memory (there is no barrier in the reader | |
9340c38d | 62 | * per-se), kick it after 10 loops waiting for it. |
3a71751e | 63 | */ |
9340c38d | 64 | #define KICK_READER_LOOPS 10 |
3a71751e PB |
65 | |
66 | /* | |
67 | * Active attempts to check for reader Q.S. before calling futex(). | |
68 | */ | |
69 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
70 | ||
999991c6 MD |
71 | /* If the headers do not support membarrier system call, fall back on RCU_MB */ |
72 | #ifdef __NR_membarrier | |
73 | # define membarrier(...) syscall(__NR_membarrier, __VA_ARGS__) | |
553b7eb9 MD |
74 | #else |
75 | # define membarrier(...) -ENOSYS | |
76 | #endif | |
77 | ||
64f469e6 | 78 | enum membarrier_cmd { |
c0bb9f69 MD |
79 | MEMBARRIER_CMD_QUERY = 0, |
80 | MEMBARRIER_CMD_SHARED = (1 << 0), | |
81 | /* reserved for MEMBARRIER_CMD_SHARED_EXPEDITED (1 << 1) */ | |
82 | /* reserved for MEMBARRIER_CMD_PRIVATE (1 << 2) */ | |
83 | MEMBARRIER_CMD_PRIVATE_EXPEDITED = (1 << 3), | |
84 | MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = (1 << 4), | |
64f469e6 | 85 | }; |
553b7eb9 | 86 | |
fdf01eed | 87 | #ifdef RCU_MEMBARRIER |
834a45ba | 88 | static int init_done; |
4477a870 | 89 | static int urcu_memb_has_sys_membarrier_private_expedited; |
c0bb9f69 | 90 | |
d8d9a340 | 91 | #ifndef CONFIG_RCU_FORCE_SYS_MEMBARRIER |
4477a870 MD |
92 | /* |
93 | * Explicitly initialize to zero because we can't alias a non-static | |
94 | * uninitialized variable. | |
95 | */ | |
96 | int urcu_memb_has_sys_membarrier = 0; | |
ce28e67a | 97 | URCU_ATTR_ALIAS("urcu_memb_has_sys_membarrier") |
4477a870 | 98 | extern int rcu_has_sys_membarrier_memb; |
d8d9a340 | 99 | #endif |
834a45ba | 100 | |
02be5561 | 101 | void __attribute__((constructor)) rcu_init(void); |
fdf01eed MD |
102 | #endif |
103 | ||
104 | #ifdef RCU_MB | |
02be5561 | 105 | void rcu_init(void) |
e90a6e9c MD |
106 | { |
107 | } | |
ce28e67a | 108 | URCU_ATTR_ALIAS(urcu_stringify(rcu_init)) |
4477a870 | 109 | void alias_rcu_init(void); |
e90a6e9c | 110 | #endif |
8a5fb4c9 | 111 | |
fdf01eed MD |
112 | #ifdef RCU_SIGNAL |
113 | static int init_done; | |
114 | ||
115 | void __attribute__((constructor)) rcu_init(void); | |
fdf01eed MD |
116 | #endif |
117 | ||
457eeeee MD |
118 | void __attribute__((destructor)) rcu_exit(void); |
119 | static void urcu_call_rcu_exit(void); | |
120 | ||
731ccb96 MD |
121 | /* |
122 | * rcu_gp_lock ensures mutual exclusion between threads calling | |
123 | * synchronize_rcu(). | |
124 | */ | |
6abb4bd5 | 125 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
731ccb96 MD |
126 | /* |
127 | * rcu_registry_lock ensures mutual exclusion between threads | |
128 | * registering and unregistering themselves to/from the registry, and | |
129 | * with threads reading that registry from synchronize_rcu(). However, | |
130 | * this lock is not held all the way through the completion of awaiting | |
131 | * for the grace period. It is sporadically released between iterations | |
132 | * on the registry. | |
133 | * rcu_registry_lock may nest inside rcu_gp_lock. | |
134 | */ | |
135 | static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER; | |
4477a870 | 136 | struct urcu_gp rcu_gp = { .ctr = URCU_GP_COUNT }; |
ce28e67a | 137 | URCU_ATTR_ALIAS(urcu_stringify(rcu_gp)) |
4477a870 | 138 | extern struct urcu_gp alias_rcu_gp; |
27b012e2 | 139 | |
b0d5e790 MD |
140 | /* |
141 | * Written to only by each individual reader. Read by both the reader and the | |
142 | * writers. | |
143 | */ | |
4477a870 | 144 | DEFINE_URCU_TLS(struct urcu_reader, rcu_reader); |
99bfa9e9 | 145 | DEFINE_URCU_TLS_ALIAS(struct urcu_reader, rcu_reader, alias_rcu_reader); |
27b012e2 | 146 | |
16aa9ee8 | 147 | static CDS_LIST_HEAD(registry); |
27b012e2 | 148 | |
5bffdd5d MD |
149 | /* |
150 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
151 | * struct gp_waiters_thread objects. | |
152 | */ | |
153 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
154 | ||
6abb4bd5 | 155 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
156 | { |
157 | int ret; | |
09a9f986 PM |
158 | |
159 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 160 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
161 | if (ret) |
162 | urcu_die(ret); | |
09a9f986 | 163 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 164 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
165 | if (ret != EBUSY && ret != EINTR) |
166 | urcu_die(ret); | |
bd252a04 | 167 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 168 | cmm_smp_mb(); |
bd252a04 | 169 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 170 | cmm_smp_mb(); |
09a9f986 | 171 | } |
8999a9ee | 172 | (void) poll(NULL, 0, 10); |
09a9f986 PM |
173 | } |
174 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
175 | } |
176 | ||
6abb4bd5 | 177 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
178 | { |
179 | int ret; | |
180 | ||
6abb4bd5 | 181 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
182 | if (ret) |
183 | urcu_die(ret); | |
41718ff9 MD |
184 | } |
185 | ||
fdf01eed | 186 | #ifdef RCU_MEMBARRIER |
a4922ed9 | 187 | static void smp_mb_master(void) |
fdf01eed | 188 | { |
4477a870 MD |
189 | if (caa_likely(urcu_memb_has_sys_membarrier)) { |
190 | if (membarrier(urcu_memb_has_sys_membarrier_private_expedited ? | |
c0bb9f69 MD |
191 | MEMBARRIER_CMD_PRIVATE_EXPEDITED : |
192 | MEMBARRIER_CMD_SHARED, 0)) | |
193 | urcu_die(errno); | |
194 | } else { | |
5481ddb3 | 195 | cmm_smp_mb(); |
c0bb9f69 | 196 | } |
fdf01eed MD |
197 | } |
198 | #endif | |
199 | ||
02be5561 | 200 | #ifdef RCU_MB |
a4922ed9 | 201 | static void smp_mb_master(void) |
40e140c9 | 202 | { |
5481ddb3 | 203 | cmm_smp_mb(); |
40e140c9 | 204 | } |
fdf01eed MD |
205 | #endif |
206 | ||
207 | #ifdef RCU_SIGNAL | |
78ff9419 | 208 | static void force_mb_all_readers(void) |
27b012e2 | 209 | { |
4477a870 | 210 | struct urcu_reader *index; |
e3b0cef0 | 211 | |
27b012e2 | 212 | /* |
5481ddb3 | 213 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
214 | * compiler barriers around rcu read lock as real memory barriers. |
215 | */ | |
16aa9ee8 | 216 | if (cds_list_empty(®istry)) |
27b012e2 | 217 | return; |
3a86deba | 218 | /* |
5481ddb3 | 219 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 220 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 221 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 222 | * cache flush is enforced. |
3a86deba | 223 | */ |
16aa9ee8 | 224 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 225 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 226 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 227 | } |
27b012e2 MD |
228 | /* |
229 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
230 | * |
231 | * Note that the pthread_kill() will never be executed on systems | |
232 | * that correctly deliver signals in a timely manner. However, it | |
233 | * is not uncommon for kernels to have bugs that can result in | |
234 | * lost or unduly delayed signals. | |
235 | * | |
236 | * If you are seeing the below pthread_kill() executing much at | |
237 | * all, we suggest testing the underlying kernel and filing the | |
238 | * relevant bug report. For Linux kernels, we recommend getting | |
239 | * the Linux Test Project (LTP). | |
27b012e2 | 240 | */ |
16aa9ee8 | 241 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 242 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 243 | pthread_kill(index->tid, SIGRCU); |
8999a9ee | 244 | (void) poll(NULL, 0, 1); |
09a9f986 PM |
245 | } |
246 | } | |
5481ddb3 | 247 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 248 | } |
9d7e3f89 | 249 | |
a4922ed9 | 250 | static void smp_mb_master(void) |
9d7e3f89 MD |
251 | { |
252 | force_mb_all_readers(); | |
253 | } | |
fdf01eed | 254 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 255 | |
bc6c15bb MD |
256 | /* |
257 | * synchronize_rcu() waiting. Single thread. | |
fca9fb96 MD |
258 | * Always called with rcu_registry lock held. Releases this lock and |
259 | * grabs it again. Holds the lock when it returns. | |
bc6c15bb | 260 | */ |
cfe78e25 | 261 | static void wait_gp(void) |
bc6c15bb | 262 | { |
fca9fb96 MD |
263 | /* |
264 | * Read reader_gp before read futex. smp_mb_master() needs to | |
265 | * be called with the rcu registry lock held in RCU_SIGNAL | |
266 | * flavor. | |
267 | */ | |
a4922ed9 | 268 | smp_mb_master(); |
fca9fb96 MD |
269 | /* Temporarily unlock the registry lock. */ |
270 | mutex_unlock(&rcu_registry_lock); | |
1c7364b7 MD |
271 | while (uatomic_read(&rcu_gp.futex) == -1) { |
272 | if (!futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { | |
273 | /* | |
274 | * Prior queued wakeups queued by unrelated code | |
275 | * using the same address can cause futex wait to | |
276 | * return 0 even through the futex value is still | |
277 | * -1 (spurious wakeups). Check the value again | |
278 | * in user-space to validate whether it really | |
279 | * differs from -1. | |
280 | */ | |
281 | continue; | |
282 | } | |
b0a841b4 | 283 | switch (errno) { |
1c7364b7 | 284 | case EAGAIN: |
b0a841b4 | 285 | /* Value already changed. */ |
fca9fb96 | 286 | goto end; |
b0a841b4 MD |
287 | case EINTR: |
288 | /* Retry if interrupted by signal. */ | |
1c7364b7 | 289 | break; /* Get out of switch. Check again. */ |
b0a841b4 MD |
290 | default: |
291 | /* Unexpected error. */ | |
292 | urcu_die(errno); | |
293 | } | |
294 | } | |
fca9fb96 MD |
295 | end: |
296 | /* | |
297 | * Re-lock the registry lock before the next loop. | |
298 | */ | |
299 | mutex_lock(&rcu_registry_lock); | |
bc6c15bb MD |
300 | } |
301 | ||
731ccb96 MD |
302 | /* |
303 | * Always called with rcu_registry lock held. Releases this lock between | |
304 | * iterations and grabs it again. Holds the lock when it returns. | |
305 | */ | |
fd189fa5 MD |
306 | static void wait_for_readers(struct cds_list_head *input_readers, |
307 | struct cds_list_head *cur_snap_readers, | |
308 | struct cds_list_head *qsreaders) | |
27b012e2 | 309 | { |
9340c38d | 310 | unsigned int wait_loops = 0; |
4477a870 | 311 | struct urcu_reader *index, *tmp; |
9340c38d MD |
312 | #ifdef HAS_INCOHERENT_CACHES |
313 | unsigned int wait_gp_loops = 0; | |
314 | #endif /* HAS_INCOHERENT_CACHES */ | |
27b012e2 | 315 | |
40e140c9 | 316 | /* |
c9488684 MD |
317 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
318 | * indicate quiescence (not nested), or observe the current | |
ed1b099e | 319 | * rcu_gp.ctr value. |
27b012e2 | 320 | */ |
cfe78e25 | 321 | for (;;) { |
5e81fed7 MD |
322 | if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) |
323 | wait_loops++; | |
9340c38d | 324 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
ed1b099e | 325 | uatomic_dec(&rcu_gp.futex); |
cfe78e25 | 326 | /* Write futex before read reader_gp */ |
a4922ed9 | 327 | smp_mb_master(); |
cfe78e25 MD |
328 | } |
329 | ||
fd189fa5 | 330 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
4477a870 MD |
331 | switch (urcu_common_reader_state(&rcu_gp, &index->ctr)) { |
332 | case URCU_READER_ACTIVE_CURRENT: | |
fd189fa5 MD |
333 | if (cur_snap_readers) { |
334 | cds_list_move(&index->node, | |
335 | cur_snap_readers); | |
336 | break; | |
337 | } | |
338 | /* Fall-through */ | |
4477a870 | 339 | case URCU_READER_INACTIVE: |
fd189fa5 MD |
340 | cds_list_move(&index->node, qsreaders); |
341 | break; | |
4477a870 | 342 | case URCU_READER_ACTIVE_OLD: |
fd189fa5 MD |
343 | /* |
344 | * Old snapshot. Leaving node in | |
345 | * input_readers will make us busy-loop | |
346 | * until the snapshot becomes current or | |
347 | * the reader becomes inactive. | |
348 | */ | |
349 | break; | |
350 | } | |
cfe78e25 MD |
351 | } |
352 | ||
e8043c1b | 353 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 354 | if (cds_list_empty(input_readers)) { |
9340c38d | 355 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 356 | /* Read reader_gp before write futex */ |
a4922ed9 | 357 | smp_mb_master(); |
ed1b099e | 358 | uatomic_set(&rcu_gp.futex, 0); |
bc6c15bb | 359 | } |
cfe78e25 MD |
360 | break; |
361 | } else { | |
fca9fb96 MD |
362 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
363 | /* wait_gp unlocks/locks registry lock. */ | |
cfe78e25 | 364 | wait_gp(); |
fca9fb96 MD |
365 | } else { |
366 | /* Temporarily unlock the registry lock. */ | |
367 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 368 | caa_cpu_relax(); |
fca9fb96 MD |
369 | /* |
370 | * Re-lock the registry lock before the | |
371 | * next loop. | |
372 | */ | |
373 | mutex_lock(&rcu_registry_lock); | |
374 | } | |
bc6c15bb | 375 | } |
e8043c1b | 376 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 377 | /* |
40e140c9 | 378 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
379 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
380 | * for too long. | |
27b012e2 | 381 | */ |
fd189fa5 | 382 | if (cds_list_empty(input_readers)) { |
9340c38d | 383 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 384 | /* Read reader_gp before write futex */ |
a4922ed9 | 385 | smp_mb_master(); |
ed1b099e | 386 | uatomic_set(&rcu_gp.futex, 0); |
cfe78e25 MD |
387 | } |
388 | break; | |
389 | } else { | |
9340c38d | 390 | if (wait_gp_loops == KICK_READER_LOOPS) { |
a4922ed9 | 391 | smp_mb_master(); |
9340c38d MD |
392 | wait_gp_loops = 0; |
393 | } | |
394 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { | |
fca9fb96 | 395 | /* wait_gp unlocks/locks registry lock. */ |
9340c38d MD |
396 | wait_gp(); |
397 | wait_gp_loops++; | |
398 | } else { | |
fca9fb96 MD |
399 | /* Temporarily unlock the registry lock. */ |
400 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 401 | caa_cpu_relax(); |
fca9fb96 MD |
402 | /* |
403 | * Re-lock the registry lock before the | |
404 | * next loop. | |
405 | */ | |
406 | mutex_lock(&rcu_registry_lock); | |
40e140c9 MD |
407 | } |
408 | } | |
e8043c1b | 409 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 410 | } |
27b012e2 MD |
411 | } |
412 | ||
9598a481 | 413 | void synchronize_rcu(void) |
2bc59bd7 | 414 | { |
fd189fa5 MD |
415 | CDS_LIST_HEAD(cur_snap_readers); |
416 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
417 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
418 | struct urcu_waiters waiters; | |
419 | ||
420 | /* | |
421 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
422 | * for a grace period. Proceed to perform the grace period only | |
423 | * if we are the first thread added into the queue. | |
424 | * The implicit memory barrier before urcu_wait_add() | |
425 | * orders prior memory accesses of threads put into the wait | |
426 | * queue before their insertion into the wait queue. | |
427 | */ | |
428 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
429 | /* Not first in queue: will be awakened by another thread. */ | |
430 | urcu_adaptative_busy_wait(&wait); | |
431 | /* Order following memory accesses after grace period. */ | |
432 | cmm_smp_mb(); | |
433 | return; | |
434 | } | |
435 | /* We won't need to wake ourself up */ | |
436 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 437 | |
6abb4bd5 | 438 | mutex_lock(&rcu_gp_lock); |
135530fd | 439 | |
5bffdd5d MD |
440 | /* |
441 | * Move all waiters into our local queue. | |
442 | */ | |
443 | urcu_move_waiters(&waiters, &gp_waiters); | |
444 | ||
731ccb96 MD |
445 | mutex_lock(&rcu_registry_lock); |
446 | ||
16aa9ee8 | 447 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
448 | goto out; |
449 | ||
731ccb96 MD |
450 | /* |
451 | * All threads should read qparity before accessing data structure | |
452 | * where new ptr points to. Must be done within rcu_registry_lock | |
453 | * because it iterates on reader threads. | |
454 | */ | |
9598a481 | 455 | /* Write new ptr before changing the qparity */ |
a4922ed9 | 456 | smp_mb_master(); |
9598a481 | 457 | |
9598a481 | 458 | /* |
c9488684 | 459 | * Wait for readers to observe original parity or be quiescent. |
731ccb96 MD |
460 | * wait_for_readers() can release and grab again rcu_registry_lock |
461 | * interally. | |
9598a481 | 462 | */ |
fd189fa5 | 463 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
464 | |
465 | /* | |
c9488684 | 466 | * Must finish waiting for quiescent state for original parity before |
ed1b099e | 467 | * committing next rcu_gp.ctr update to memory. Failure to do so could |
d40fde2c MD |
468 | * result in the writer waiting forever while new readers are always |
469 | * accessing data (no progress). Enforce compiler-order of load | |
ed1b099e | 470 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr. |
9598a481 | 471 | */ |
5481ddb3 | 472 | cmm_barrier(); |
9598a481 | 473 | |
5dba80f9 | 474 | /* |
5481ddb3 | 475 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
476 | * model easier to understand. It does not have a big performance impact |
477 | * anyway, given this is the write-side. | |
478 | */ | |
5481ddb3 | 479 | cmm_smp_mb(); |
67c2d80b | 480 | |
c9488684 | 481 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
4477a870 | 482 | CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ URCU_GP_CTR_PHASE); |
c9488684 MD |
483 | |
484 | /* | |
ed1b099e | 485 | * Must commit rcu_gp.ctr update to memory before waiting for quiescent |
c9488684 MD |
486 | * state. Failure to do so could result in the writer waiting forever |
487 | * while new readers are always accessing data (no progress). Enforce | |
ed1b099e | 488 | * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr. |
c9488684 MD |
489 | */ |
490 | cmm_barrier(); | |
491 | ||
492 | /* | |
493 | * | |
494 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
495 | * model easier to understand. It does not have a big performance impact | |
496 | * anyway, given this is the write-side. | |
497 | */ | |
498 | cmm_smp_mb(); | |
499 | ||
9598a481 | 500 | /* |
c9488684 | 501 | * Wait for readers to observe new parity or be quiescent. |
731ccb96 MD |
502 | * wait_for_readers() can release and grab again rcu_registry_lock |
503 | * interally. | |
9598a481 | 504 | */ |
fd189fa5 MD |
505 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
506 | ||
507 | /* | |
508 | * Put quiescent reader list back into registry. | |
509 | */ | |
510 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 511 | |
731ccb96 MD |
512 | /* |
513 | * Finish waiting for reader threads before letting the old ptr | |
514 | * being freed. Must be done within rcu_registry_lock because it | |
515 | * iterates on reader threads. | |
516 | */ | |
a4922ed9 | 517 | smp_mb_master(); |
2dfb8b5e | 518 | out: |
731ccb96 | 519 | mutex_unlock(&rcu_registry_lock); |
6abb4bd5 | 520 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
521 | |
522 | /* | |
523 | * Wakeup waiters only after we have completed the grace period | |
524 | * and have ensured the memory barriers at the end of the grace | |
525 | * period have been issued. | |
526 | */ | |
527 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 | 528 | } |
ce28e67a | 529 | URCU_ATTR_ALIAS(urcu_stringify(synchronize_rcu)) |
4477a870 | 530 | void alias_synchronize_rcu(); |
2bc59bd7 | 531 | |
121a5d44 MD |
532 | /* |
533 | * library wrappers to be used by non-LGPL compatible source code. | |
534 | */ | |
535 | ||
536 | void rcu_read_lock(void) | |
537 | { | |
538 | _rcu_read_lock(); | |
539 | } | |
ce28e67a | 540 | URCU_ATTR_ALIAS(urcu_stringify(rcu_read_lock)) |
4477a870 | 541 | void alias_rcu_read_lock(); |
121a5d44 MD |
542 | |
543 | void rcu_read_unlock(void) | |
544 | { | |
545 | _rcu_read_unlock(); | |
546 | } | |
ce28e67a | 547 | URCU_ATTR_ALIAS(urcu_stringify(rcu_read_unlock)) |
4477a870 | 548 | void alias_rcu_read_unlock(); |
121a5d44 | 549 | |
882f3357 MD |
550 | int rcu_read_ongoing(void) |
551 | { | |
552 | return _rcu_read_ongoing(); | |
553 | } | |
ce28e67a | 554 | URCU_ATTR_ALIAS(urcu_stringify(rcu_read_ongoing)) |
4477a870 | 555 | void alias_rcu_read_ongoing(); |
882f3357 | 556 | |
121a5d44 | 557 | void rcu_register_thread(void) |
27b012e2 | 558 | { |
bd252a04 MD |
559 | URCU_TLS(rcu_reader).tid = pthread_self(); |
560 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
4477a870 | 561 | assert(!(URCU_TLS(rcu_reader).ctr & URCU_GP_CTR_NEST_MASK)); |
02be5561 | 562 | |
731ccb96 | 563 | mutex_lock(&rcu_registry_lock); |
a77f7d82 MD |
564 | assert(!URCU_TLS(rcu_reader).registered); |
565 | URCU_TLS(rcu_reader).registered = 1; | |
02be5561 | 566 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 567 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
731ccb96 | 568 | mutex_unlock(&rcu_registry_lock); |
27b012e2 | 569 | } |
ce28e67a | 570 | URCU_ATTR_ALIAS(urcu_stringify(rcu_register_thread)) |
4477a870 | 571 | void alias_rcu_register_thread(); |
27b012e2 | 572 | |
121a5d44 | 573 | void rcu_unregister_thread(void) |
27b012e2 | 574 | { |
731ccb96 | 575 | mutex_lock(&rcu_registry_lock); |
a77f7d82 MD |
576 | assert(URCU_TLS(rcu_reader).registered); |
577 | URCU_TLS(rcu_reader).registered = 0; | |
bd252a04 | 578 | cds_list_del(&URCU_TLS(rcu_reader).node); |
731ccb96 | 579 | mutex_unlock(&rcu_registry_lock); |
27b012e2 | 580 | } |
ce28e67a | 581 | URCU_ATTR_ALIAS(urcu_stringify(rcu_unregister_thread)) |
4477a870 | 582 | void alias_rcu_unregister_thread(); |
27b012e2 | 583 | |
fdf01eed | 584 | #ifdef RCU_MEMBARRIER |
d8d9a340 MD |
585 | |
586 | #ifdef CONFIG_RCU_FORCE_SYS_MEMBARRIER | |
587 | static | |
c0bb9f69 | 588 | void rcu_sys_membarrier_status(bool available) |
d8d9a340 MD |
589 | { |
590 | if (!available) | |
591 | abort(); | |
592 | } | |
593 | #else | |
594 | static | |
c0bb9f69 | 595 | void rcu_sys_membarrier_status(bool available) |
d8d9a340 | 596 | { |
c0bb9f69 MD |
597 | if (!available) |
598 | return; | |
4477a870 | 599 | urcu_memb_has_sys_membarrier = 1; |
d8d9a340 MD |
600 | } |
601 | #endif | |
602 | ||
c0bb9f69 MD |
603 | static |
604 | void rcu_sys_membarrier_init(void) | |
fdf01eed | 605 | { |
c0bb9f69 MD |
606 | bool available = false; |
607 | int mask; | |
608 | ||
609 | mask = membarrier(MEMBARRIER_CMD_QUERY, 0); | |
610 | if (mask >= 0) { | |
611 | if (mask & MEMBARRIER_CMD_PRIVATE_EXPEDITED) { | |
612 | if (membarrier(MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, 0)) | |
613 | urcu_die(errno); | |
4477a870 | 614 | urcu_memb_has_sys_membarrier_private_expedited = 1; |
c0bb9f69 MD |
615 | available = true; |
616 | } else if (mask & MEMBARRIER_CMD_SHARED) { | |
617 | available = true; | |
618 | } | |
619 | } | |
620 | rcu_sys_membarrier_status(available); | |
621 | } | |
64f469e6 | 622 | |
c0bb9f69 MD |
623 | void rcu_init(void) |
624 | { | |
fdf01eed MD |
625 | if (init_done) |
626 | return; | |
627 | init_done = 1; | |
c0bb9f69 | 628 | rcu_sys_membarrier_init(); |
fdf01eed | 629 | } |
ce28e67a | 630 | URCU_ATTR_ALIAS(urcu_stringify(rcu_init)) |
4477a870 | 631 | void alias_rcu_init(void); |
fdf01eed MD |
632 | #endif |
633 | ||
634 | #ifdef RCU_SIGNAL | |
17a8f206 MJ |
635 | static void sigrcu_handler(int signo __attribute__((unused)), |
636 | siginfo_t *siginfo __attribute__((unused)), | |
637 | void *context __attribute__((unused))) | |
27b012e2 | 638 | { |
40e140c9 | 639 | /* |
5481ddb3 DG |
640 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
641 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
642 | * executed on. |
643 | */ | |
5481ddb3 | 644 | cmm_smp_mb(); |
bd252a04 | 645 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 646 | cmm_smp_mb(); |
27b012e2 MD |
647 | } |
648 | ||
8a5fb4c9 | 649 | /* |
02be5561 | 650 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
651 | * reader threads are calling rcu_register_thread(). |
652 | * Should only be called by a single thread at a given time. This is ensured by | |
731ccb96 MD |
653 | * holing the rcu_registry_lock from rcu_register_thread() or by running |
654 | * at library load time, which should not be executed by multiple | |
655 | * threads nor concurrently with rcu_register_thread() anyway. | |
8a5fb4c9 | 656 | */ |
02be5561 | 657 | void rcu_init(void) |
27b012e2 MD |
658 | { |
659 | struct sigaction act; | |
660 | int ret; | |
661 | ||
8a5fb4c9 MD |
662 | if (init_done) |
663 | return; | |
664 | init_done = 1; | |
665 | ||
02be5561 | 666 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 667 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 668 | sigemptyset(&act.sa_mask); |
02be5561 | 669 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
670 | if (ret) |
671 | urcu_die(errno); | |
27b012e2 | 672 | } |
ce28e67a | 673 | URCU_ATTR_ALIAS(urcu_stringify(rcu_init)) |
4477a870 | 674 | void alias_rcu_init(void); |
27b012e2 | 675 | |
457eeeee MD |
676 | /* |
677 | * Don't unregister the SIGRCU signal handler anymore, because | |
678 | * call_rcu threads could still be using it shortly before the | |
679 | * application exits. | |
680 | * Assertion disabled because call_rcu threads are now rcu | |
681 | * readers, and left running at exit. | |
682 | * assert(cds_list_empty(®istry)); | |
683 | */ | |
684 | ||
685 | #endif /* #ifdef RCU_SIGNAL */ | |
686 | ||
02be5561 | 687 | void rcu_exit(void) |
27b012e2 | 688 | { |
457eeeee | 689 | urcu_call_rcu_exit(); |
27b012e2 | 690 | } |
ce28e67a | 691 | URCU_ATTR_ALIAS(urcu_stringify(rcu_exit)) |
4477a870 | 692 | void alias_rcu_exit(void); |
5e77fc1f | 693 | |
5e6b23a6 | 694 | DEFINE_RCU_FLAVOR(rcu_flavor); |
4477a870 | 695 | DEFINE_RCU_FLAVOR_ALIAS(rcu_flavor, alias_rcu_flavor); |
541d828d | 696 | |
5e77fc1f | 697 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 698 | #include "urcu-defer-impl.h" |