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> |
c0bb9f69 | 37 | #include <stdbool.h> |
e8043c1b | 38 | #include <poll.h> |
27b012e2 | 39 | |
4477a870 MD |
40 | #include <urcu/arch.h> |
41 | #include <urcu/wfcqueue.h> | |
42 | #include <urcu/map/urcu.h> | |
43 | #include <urcu/static/urcu.h> | |
44 | #include <urcu/pointer.h> | |
45 | #include <urcu/tls-compat.h> | |
71c811bf | 46 | |
4a6d7378 | 47 | #include "urcu-die.h" |
5bffdd5d | 48 | #include "urcu-wait.h" |
4477a870 | 49 | #include "urcu-utils.h" |
4a6d7378 | 50 | |
4477a870 | 51 | #define URCU_API_MAP |
121a5d44 | 52 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
71c811bf | 53 | #undef _LGPL_SOURCE |
4477a870 | 54 | #include <urcu/urcu.h> |
71c811bf | 55 | #define _LGPL_SOURCE |
27b012e2 | 56 | |
3a71751e PB |
57 | /* |
58 | * If a reader is really non-cooperative and refuses to commit its | |
59 | * rcu_active_readers count to memory (there is no barrier in the reader | |
9340c38d | 60 | * per-se), kick it after 10 loops waiting for it. |
3a71751e | 61 | */ |
9340c38d | 62 | #define KICK_READER_LOOPS 10 |
3a71751e PB |
63 | |
64 | /* | |
65 | * Active attempts to check for reader Q.S. before calling futex(). | |
66 | */ | |
67 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
68 | ||
999991c6 MD |
69 | /* If the headers do not support membarrier system call, fall back on RCU_MB */ |
70 | #ifdef __NR_membarrier | |
71 | # define membarrier(...) syscall(__NR_membarrier, __VA_ARGS__) | |
553b7eb9 MD |
72 | #else |
73 | # define membarrier(...) -ENOSYS | |
74 | #endif | |
75 | ||
64f469e6 | 76 | enum membarrier_cmd { |
c0bb9f69 MD |
77 | MEMBARRIER_CMD_QUERY = 0, |
78 | MEMBARRIER_CMD_SHARED = (1 << 0), | |
79 | /* reserved for MEMBARRIER_CMD_SHARED_EXPEDITED (1 << 1) */ | |
80 | /* reserved for MEMBARRIER_CMD_PRIVATE (1 << 2) */ | |
81 | MEMBARRIER_CMD_PRIVATE_EXPEDITED = (1 << 3), | |
82 | MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = (1 << 4), | |
64f469e6 | 83 | }; |
553b7eb9 | 84 | |
fdf01eed | 85 | #ifdef RCU_MEMBARRIER |
834a45ba | 86 | static int init_done; |
4477a870 | 87 | static int urcu_memb_has_sys_membarrier_private_expedited; |
c0bb9f69 | 88 | |
d8d9a340 | 89 | #ifndef CONFIG_RCU_FORCE_SYS_MEMBARRIER |
4477a870 MD |
90 | /* |
91 | * Explicitly initialize to zero because we can't alias a non-static | |
92 | * uninitialized variable. | |
93 | */ | |
94 | int urcu_memb_has_sys_membarrier = 0; | |
ce28e67a | 95 | URCU_ATTR_ALIAS("urcu_memb_has_sys_membarrier") |
4477a870 | 96 | extern int rcu_has_sys_membarrier_memb; |
d8d9a340 | 97 | #endif |
834a45ba | 98 | |
02be5561 | 99 | void __attribute__((constructor)) rcu_init(void); |
fdf01eed MD |
100 | #endif |
101 | ||
102 | #ifdef RCU_MB | |
02be5561 | 103 | void rcu_init(void) |
e90a6e9c MD |
104 | { |
105 | } | |
ce28e67a | 106 | URCU_ATTR_ALIAS(urcu_stringify(rcu_init)) |
4477a870 | 107 | void alias_rcu_init(void); |
e90a6e9c | 108 | #endif |
8a5fb4c9 | 109 | |
fdf01eed MD |
110 | #ifdef RCU_SIGNAL |
111 | static int init_done; | |
112 | ||
113 | void __attribute__((constructor)) rcu_init(void); | |
114 | void __attribute__((destructor)) rcu_exit(void); | |
115 | #endif | |
116 | ||
731ccb96 MD |
117 | /* |
118 | * rcu_gp_lock ensures mutual exclusion between threads calling | |
119 | * synchronize_rcu(). | |
120 | */ | |
6abb4bd5 | 121 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
731ccb96 MD |
122 | /* |
123 | * rcu_registry_lock ensures mutual exclusion between threads | |
124 | * registering and unregistering themselves to/from the registry, and | |
125 | * with threads reading that registry from synchronize_rcu(). However, | |
126 | * this lock is not held all the way through the completion of awaiting | |
127 | * for the grace period. It is sporadically released between iterations | |
128 | * on the registry. | |
129 | * rcu_registry_lock may nest inside rcu_gp_lock. | |
130 | */ | |
131 | static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER; | |
4477a870 | 132 | struct urcu_gp rcu_gp = { .ctr = URCU_GP_COUNT }; |
ce28e67a | 133 | URCU_ATTR_ALIAS(urcu_stringify(rcu_gp)) |
4477a870 | 134 | extern struct urcu_gp alias_rcu_gp; |
27b012e2 | 135 | |
b0d5e790 MD |
136 | /* |
137 | * Written to only by each individual reader. Read by both the reader and the | |
138 | * writers. | |
139 | */ | |
4477a870 | 140 | DEFINE_URCU_TLS(struct urcu_reader, rcu_reader); |
99bfa9e9 | 141 | DEFINE_URCU_TLS_ALIAS(struct urcu_reader, rcu_reader, alias_rcu_reader); |
27b012e2 | 142 | |
16aa9ee8 | 143 | static CDS_LIST_HEAD(registry); |
27b012e2 | 144 | |
5bffdd5d MD |
145 | /* |
146 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
147 | * struct gp_waiters_thread objects. | |
148 | */ | |
149 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
150 | ||
6abb4bd5 | 151 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
152 | { |
153 | int ret; | |
09a9f986 PM |
154 | |
155 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 156 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
157 | if (ret) |
158 | urcu_die(ret); | |
09a9f986 | 159 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 160 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
161 | if (ret != EBUSY && ret != EINTR) |
162 | urcu_die(ret); | |
bd252a04 | 163 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 164 | cmm_smp_mb(); |
bd252a04 | 165 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 166 | cmm_smp_mb(); |
09a9f986 | 167 | } |
8999a9ee | 168 | (void) poll(NULL, 0, 10); |
09a9f986 PM |
169 | } |
170 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
171 | } |
172 | ||
6abb4bd5 | 173 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
174 | { |
175 | int ret; | |
176 | ||
6abb4bd5 | 177 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
178 | if (ret) |
179 | urcu_die(ret); | |
41718ff9 MD |
180 | } |
181 | ||
fdf01eed | 182 | #ifdef RCU_MEMBARRIER |
a4922ed9 | 183 | static void smp_mb_master(void) |
fdf01eed | 184 | { |
4477a870 MD |
185 | if (caa_likely(urcu_memb_has_sys_membarrier)) { |
186 | if (membarrier(urcu_memb_has_sys_membarrier_private_expedited ? | |
c0bb9f69 MD |
187 | MEMBARRIER_CMD_PRIVATE_EXPEDITED : |
188 | MEMBARRIER_CMD_SHARED, 0)) | |
189 | urcu_die(errno); | |
190 | } else { | |
5481ddb3 | 191 | cmm_smp_mb(); |
c0bb9f69 | 192 | } |
fdf01eed MD |
193 | } |
194 | #endif | |
195 | ||
02be5561 | 196 | #ifdef RCU_MB |
a4922ed9 | 197 | static void smp_mb_master(void) |
40e140c9 | 198 | { |
5481ddb3 | 199 | cmm_smp_mb(); |
40e140c9 | 200 | } |
fdf01eed MD |
201 | #endif |
202 | ||
203 | #ifdef RCU_SIGNAL | |
78ff9419 | 204 | static void force_mb_all_readers(void) |
27b012e2 | 205 | { |
4477a870 | 206 | struct urcu_reader *index; |
e3b0cef0 | 207 | |
27b012e2 | 208 | /* |
5481ddb3 | 209 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
210 | * compiler barriers around rcu read lock as real memory barriers. |
211 | */ | |
16aa9ee8 | 212 | if (cds_list_empty(®istry)) |
27b012e2 | 213 | return; |
3a86deba | 214 | /* |
5481ddb3 | 215 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 216 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 217 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 218 | * cache flush is enforced. |
3a86deba | 219 | */ |
16aa9ee8 | 220 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 221 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 222 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 223 | } |
27b012e2 MD |
224 | /* |
225 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
226 | * |
227 | * Note that the pthread_kill() will never be executed on systems | |
228 | * that correctly deliver signals in a timely manner. However, it | |
229 | * is not uncommon for kernels to have bugs that can result in | |
230 | * lost or unduly delayed signals. | |
231 | * | |
232 | * If you are seeing the below pthread_kill() executing much at | |
233 | * all, we suggest testing the underlying kernel and filing the | |
234 | * relevant bug report. For Linux kernels, we recommend getting | |
235 | * the Linux Test Project (LTP). | |
27b012e2 | 236 | */ |
16aa9ee8 | 237 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 238 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 239 | pthread_kill(index->tid, SIGRCU); |
8999a9ee | 240 | (void) poll(NULL, 0, 1); |
09a9f986 PM |
241 | } |
242 | } | |
5481ddb3 | 243 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 244 | } |
9d7e3f89 | 245 | |
a4922ed9 | 246 | static void smp_mb_master(void) |
9d7e3f89 MD |
247 | { |
248 | force_mb_all_readers(); | |
249 | } | |
fdf01eed | 250 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 251 | |
bc6c15bb MD |
252 | /* |
253 | * synchronize_rcu() waiting. Single thread. | |
fca9fb96 MD |
254 | * Always called with rcu_registry lock held. Releases this lock and |
255 | * grabs it again. Holds the lock when it returns. | |
bc6c15bb | 256 | */ |
cfe78e25 | 257 | static void wait_gp(void) |
bc6c15bb | 258 | { |
fca9fb96 MD |
259 | /* |
260 | * Read reader_gp before read futex. smp_mb_master() needs to | |
261 | * be called with the rcu registry lock held in RCU_SIGNAL | |
262 | * flavor. | |
263 | */ | |
a4922ed9 | 264 | smp_mb_master(); |
fca9fb96 MD |
265 | /* Temporarily unlock the registry lock. */ |
266 | mutex_unlock(&rcu_registry_lock); | |
b0a841b4 | 267 | if (uatomic_read(&rcu_gp.futex) != -1) |
fca9fb96 | 268 | goto end; |
b0a841b4 MD |
269 | while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, |
270 | NULL, NULL, 0)) { | |
271 | switch (errno) { | |
272 | case EWOULDBLOCK: | |
273 | /* Value already changed. */ | |
fca9fb96 | 274 | goto end; |
b0a841b4 MD |
275 | case EINTR: |
276 | /* Retry if interrupted by signal. */ | |
277 | break; /* Get out of switch. */ | |
278 | default: | |
279 | /* Unexpected error. */ | |
280 | urcu_die(errno); | |
281 | } | |
282 | } | |
fca9fb96 MD |
283 | end: |
284 | /* | |
285 | * Re-lock the registry lock before the next loop. | |
286 | */ | |
287 | mutex_lock(&rcu_registry_lock); | |
bc6c15bb MD |
288 | } |
289 | ||
731ccb96 MD |
290 | /* |
291 | * Always called with rcu_registry lock held. Releases this lock between | |
292 | * iterations and grabs it again. Holds the lock when it returns. | |
293 | */ | |
fd189fa5 MD |
294 | static void wait_for_readers(struct cds_list_head *input_readers, |
295 | struct cds_list_head *cur_snap_readers, | |
296 | struct cds_list_head *qsreaders) | |
27b012e2 | 297 | { |
9340c38d | 298 | unsigned int wait_loops = 0; |
4477a870 | 299 | struct urcu_reader *index, *tmp; |
9340c38d MD |
300 | #ifdef HAS_INCOHERENT_CACHES |
301 | unsigned int wait_gp_loops = 0; | |
302 | #endif /* HAS_INCOHERENT_CACHES */ | |
27b012e2 | 303 | |
40e140c9 | 304 | /* |
c9488684 MD |
305 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
306 | * indicate quiescence (not nested), or observe the current | |
ed1b099e | 307 | * rcu_gp.ctr value. |
27b012e2 | 308 | */ |
cfe78e25 | 309 | for (;;) { |
5e81fed7 MD |
310 | if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) |
311 | wait_loops++; | |
9340c38d | 312 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
ed1b099e | 313 | uatomic_dec(&rcu_gp.futex); |
cfe78e25 | 314 | /* Write futex before read reader_gp */ |
a4922ed9 | 315 | smp_mb_master(); |
cfe78e25 MD |
316 | } |
317 | ||
fd189fa5 | 318 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
4477a870 MD |
319 | switch (urcu_common_reader_state(&rcu_gp, &index->ctr)) { |
320 | case URCU_READER_ACTIVE_CURRENT: | |
fd189fa5 MD |
321 | if (cur_snap_readers) { |
322 | cds_list_move(&index->node, | |
323 | cur_snap_readers); | |
324 | break; | |
325 | } | |
326 | /* Fall-through */ | |
4477a870 | 327 | case URCU_READER_INACTIVE: |
fd189fa5 MD |
328 | cds_list_move(&index->node, qsreaders); |
329 | break; | |
4477a870 | 330 | case URCU_READER_ACTIVE_OLD: |
fd189fa5 MD |
331 | /* |
332 | * Old snapshot. Leaving node in | |
333 | * input_readers will make us busy-loop | |
334 | * until the snapshot becomes current or | |
335 | * the reader becomes inactive. | |
336 | */ | |
337 | break; | |
338 | } | |
cfe78e25 MD |
339 | } |
340 | ||
e8043c1b | 341 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 342 | if (cds_list_empty(input_readers)) { |
9340c38d | 343 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 344 | /* Read reader_gp before write futex */ |
a4922ed9 | 345 | smp_mb_master(); |
ed1b099e | 346 | uatomic_set(&rcu_gp.futex, 0); |
bc6c15bb | 347 | } |
cfe78e25 MD |
348 | break; |
349 | } else { | |
fca9fb96 MD |
350 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
351 | /* wait_gp unlocks/locks registry lock. */ | |
cfe78e25 | 352 | wait_gp(); |
fca9fb96 MD |
353 | } else { |
354 | /* Temporarily unlock the registry lock. */ | |
355 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 356 | caa_cpu_relax(); |
fca9fb96 MD |
357 | /* |
358 | * Re-lock the registry lock before the | |
359 | * next loop. | |
360 | */ | |
361 | mutex_lock(&rcu_registry_lock); | |
362 | } | |
bc6c15bb | 363 | } |
e8043c1b | 364 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 365 | /* |
40e140c9 | 366 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
367 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
368 | * for too long. | |
27b012e2 | 369 | */ |
fd189fa5 | 370 | if (cds_list_empty(input_readers)) { |
9340c38d | 371 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 372 | /* Read reader_gp before write futex */ |
a4922ed9 | 373 | smp_mb_master(); |
ed1b099e | 374 | uatomic_set(&rcu_gp.futex, 0); |
cfe78e25 MD |
375 | } |
376 | break; | |
377 | } else { | |
9340c38d | 378 | if (wait_gp_loops == KICK_READER_LOOPS) { |
a4922ed9 | 379 | smp_mb_master(); |
9340c38d MD |
380 | wait_gp_loops = 0; |
381 | } | |
382 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { | |
fca9fb96 | 383 | /* wait_gp unlocks/locks registry lock. */ |
9340c38d MD |
384 | wait_gp(); |
385 | wait_gp_loops++; | |
386 | } else { | |
fca9fb96 MD |
387 | /* Temporarily unlock the registry lock. */ |
388 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 389 | caa_cpu_relax(); |
fca9fb96 MD |
390 | /* |
391 | * Re-lock the registry lock before the | |
392 | * next loop. | |
393 | */ | |
394 | mutex_lock(&rcu_registry_lock); | |
40e140c9 MD |
395 | } |
396 | } | |
e8043c1b | 397 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 398 | } |
27b012e2 MD |
399 | } |
400 | ||
9598a481 | 401 | void synchronize_rcu(void) |
2bc59bd7 | 402 | { |
fd189fa5 MD |
403 | CDS_LIST_HEAD(cur_snap_readers); |
404 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
405 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
406 | struct urcu_waiters waiters; | |
407 | ||
408 | /* | |
409 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
410 | * for a grace period. Proceed to perform the grace period only | |
411 | * if we are the first thread added into the queue. | |
412 | * The implicit memory barrier before urcu_wait_add() | |
413 | * orders prior memory accesses of threads put into the wait | |
414 | * queue before their insertion into the wait queue. | |
415 | */ | |
416 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
417 | /* Not first in queue: will be awakened by another thread. */ | |
418 | urcu_adaptative_busy_wait(&wait); | |
419 | /* Order following memory accesses after grace period. */ | |
420 | cmm_smp_mb(); | |
421 | return; | |
422 | } | |
423 | /* We won't need to wake ourself up */ | |
424 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 425 | |
6abb4bd5 | 426 | mutex_lock(&rcu_gp_lock); |
135530fd | 427 | |
5bffdd5d MD |
428 | /* |
429 | * Move all waiters into our local queue. | |
430 | */ | |
431 | urcu_move_waiters(&waiters, &gp_waiters); | |
432 | ||
731ccb96 MD |
433 | mutex_lock(&rcu_registry_lock); |
434 | ||
16aa9ee8 | 435 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
436 | goto out; |
437 | ||
731ccb96 MD |
438 | /* |
439 | * All threads should read qparity before accessing data structure | |
440 | * where new ptr points to. Must be done within rcu_registry_lock | |
441 | * because it iterates on reader threads. | |
442 | */ | |
9598a481 | 443 | /* Write new ptr before changing the qparity */ |
a4922ed9 | 444 | smp_mb_master(); |
9598a481 | 445 | |
9598a481 | 446 | /* |
c9488684 | 447 | * Wait for readers to observe original parity or be quiescent. |
731ccb96 MD |
448 | * wait_for_readers() can release and grab again rcu_registry_lock |
449 | * interally. | |
9598a481 | 450 | */ |
fd189fa5 | 451 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
452 | |
453 | /* | |
c9488684 | 454 | * Must finish waiting for quiescent state for original parity before |
ed1b099e | 455 | * committing next rcu_gp.ctr update to memory. Failure to do so could |
d40fde2c MD |
456 | * result in the writer waiting forever while new readers are always |
457 | * accessing data (no progress). Enforce compiler-order of load | |
ed1b099e | 458 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr. |
9598a481 | 459 | */ |
5481ddb3 | 460 | cmm_barrier(); |
9598a481 | 461 | |
5dba80f9 | 462 | /* |
5481ddb3 | 463 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
464 | * model easier to understand. It does not have a big performance impact |
465 | * anyway, given this is the write-side. | |
466 | */ | |
5481ddb3 | 467 | cmm_smp_mb(); |
67c2d80b | 468 | |
c9488684 | 469 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
4477a870 | 470 | CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ URCU_GP_CTR_PHASE); |
c9488684 MD |
471 | |
472 | /* | |
ed1b099e | 473 | * Must commit rcu_gp.ctr update to memory before waiting for quiescent |
c9488684 MD |
474 | * state. Failure to do so could result in the writer waiting forever |
475 | * while new readers are always accessing data (no progress). Enforce | |
ed1b099e | 476 | * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr. |
c9488684 MD |
477 | */ |
478 | cmm_barrier(); | |
479 | ||
480 | /* | |
481 | * | |
482 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
483 | * model easier to understand. It does not have a big performance impact | |
484 | * anyway, given this is the write-side. | |
485 | */ | |
486 | cmm_smp_mb(); | |
487 | ||
9598a481 | 488 | /* |
c9488684 | 489 | * Wait for readers to observe new parity or be quiescent. |
731ccb96 MD |
490 | * wait_for_readers() can release and grab again rcu_registry_lock |
491 | * interally. | |
9598a481 | 492 | */ |
fd189fa5 MD |
493 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
494 | ||
495 | /* | |
496 | * Put quiescent reader list back into registry. | |
497 | */ | |
498 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 499 | |
731ccb96 MD |
500 | /* |
501 | * Finish waiting for reader threads before letting the old ptr | |
502 | * being freed. Must be done within rcu_registry_lock because it | |
503 | * iterates on reader threads. | |
504 | */ | |
a4922ed9 | 505 | smp_mb_master(); |
2dfb8b5e | 506 | out: |
731ccb96 | 507 | mutex_unlock(&rcu_registry_lock); |
6abb4bd5 | 508 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
509 | |
510 | /* | |
511 | * Wakeup waiters only after we have completed the grace period | |
512 | * and have ensured the memory barriers at the end of the grace | |
513 | * period have been issued. | |
514 | */ | |
515 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 | 516 | } |
ce28e67a | 517 | URCU_ATTR_ALIAS(urcu_stringify(synchronize_rcu)) |
4477a870 | 518 | void alias_synchronize_rcu(); |
2bc59bd7 | 519 | |
121a5d44 MD |
520 | /* |
521 | * library wrappers to be used by non-LGPL compatible source code. | |
522 | */ | |
523 | ||
524 | void rcu_read_lock(void) | |
525 | { | |
526 | _rcu_read_lock(); | |
527 | } | |
ce28e67a | 528 | URCU_ATTR_ALIAS(urcu_stringify(rcu_read_lock)) |
4477a870 | 529 | void alias_rcu_read_lock(); |
121a5d44 MD |
530 | |
531 | void rcu_read_unlock(void) | |
532 | { | |
533 | _rcu_read_unlock(); | |
534 | } | |
ce28e67a | 535 | URCU_ATTR_ALIAS(urcu_stringify(rcu_read_unlock)) |
4477a870 | 536 | void alias_rcu_read_unlock(); |
121a5d44 | 537 | |
882f3357 MD |
538 | int rcu_read_ongoing(void) |
539 | { | |
540 | return _rcu_read_ongoing(); | |
541 | } | |
ce28e67a | 542 | URCU_ATTR_ALIAS(urcu_stringify(rcu_read_ongoing)) |
4477a870 | 543 | void alias_rcu_read_ongoing(); |
882f3357 | 544 | |
121a5d44 | 545 | void rcu_register_thread(void) |
27b012e2 | 546 | { |
bd252a04 MD |
547 | URCU_TLS(rcu_reader).tid = pthread_self(); |
548 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
4477a870 | 549 | assert(!(URCU_TLS(rcu_reader).ctr & URCU_GP_CTR_NEST_MASK)); |
02be5561 | 550 | |
731ccb96 | 551 | mutex_lock(&rcu_registry_lock); |
a77f7d82 MD |
552 | assert(!URCU_TLS(rcu_reader).registered); |
553 | URCU_TLS(rcu_reader).registered = 1; | |
02be5561 | 554 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 555 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
731ccb96 | 556 | mutex_unlock(&rcu_registry_lock); |
27b012e2 | 557 | } |
ce28e67a | 558 | URCU_ATTR_ALIAS(urcu_stringify(rcu_register_thread)) |
4477a870 | 559 | void alias_rcu_register_thread(); |
27b012e2 | 560 | |
121a5d44 | 561 | void rcu_unregister_thread(void) |
27b012e2 | 562 | { |
731ccb96 | 563 | mutex_lock(&rcu_registry_lock); |
a77f7d82 MD |
564 | assert(URCU_TLS(rcu_reader).registered); |
565 | URCU_TLS(rcu_reader).registered = 0; | |
bd252a04 | 566 | cds_list_del(&URCU_TLS(rcu_reader).node); |
731ccb96 | 567 | mutex_unlock(&rcu_registry_lock); |
27b012e2 | 568 | } |
ce28e67a | 569 | URCU_ATTR_ALIAS(urcu_stringify(rcu_unregister_thread)) |
4477a870 | 570 | void alias_rcu_unregister_thread(); |
27b012e2 | 571 | |
fdf01eed | 572 | #ifdef RCU_MEMBARRIER |
d8d9a340 MD |
573 | |
574 | #ifdef CONFIG_RCU_FORCE_SYS_MEMBARRIER | |
575 | static | |
c0bb9f69 | 576 | void rcu_sys_membarrier_status(bool available) |
d8d9a340 MD |
577 | { |
578 | if (!available) | |
579 | abort(); | |
580 | } | |
581 | #else | |
582 | static | |
c0bb9f69 | 583 | void rcu_sys_membarrier_status(bool available) |
d8d9a340 | 584 | { |
c0bb9f69 MD |
585 | if (!available) |
586 | return; | |
4477a870 | 587 | urcu_memb_has_sys_membarrier = 1; |
d8d9a340 MD |
588 | } |
589 | #endif | |
590 | ||
c0bb9f69 MD |
591 | static |
592 | void rcu_sys_membarrier_init(void) | |
fdf01eed | 593 | { |
c0bb9f69 MD |
594 | bool available = false; |
595 | int mask; | |
596 | ||
597 | mask = membarrier(MEMBARRIER_CMD_QUERY, 0); | |
598 | if (mask >= 0) { | |
599 | if (mask & MEMBARRIER_CMD_PRIVATE_EXPEDITED) { | |
600 | if (membarrier(MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, 0)) | |
601 | urcu_die(errno); | |
4477a870 | 602 | urcu_memb_has_sys_membarrier_private_expedited = 1; |
c0bb9f69 MD |
603 | available = true; |
604 | } else if (mask & MEMBARRIER_CMD_SHARED) { | |
605 | available = true; | |
606 | } | |
607 | } | |
608 | rcu_sys_membarrier_status(available); | |
609 | } | |
64f469e6 | 610 | |
c0bb9f69 MD |
611 | void rcu_init(void) |
612 | { | |
fdf01eed MD |
613 | if (init_done) |
614 | return; | |
615 | init_done = 1; | |
c0bb9f69 | 616 | rcu_sys_membarrier_init(); |
fdf01eed | 617 | } |
ce28e67a | 618 | URCU_ATTR_ALIAS(urcu_stringify(rcu_init)) |
4477a870 | 619 | void alias_rcu_init(void); |
fdf01eed MD |
620 | #endif |
621 | ||
622 | #ifdef RCU_SIGNAL | |
02be5561 | 623 | static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) |
27b012e2 | 624 | { |
40e140c9 | 625 | /* |
5481ddb3 DG |
626 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
627 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
628 | * executed on. |
629 | */ | |
5481ddb3 | 630 | cmm_smp_mb(); |
bd252a04 | 631 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 632 | cmm_smp_mb(); |
27b012e2 MD |
633 | } |
634 | ||
8a5fb4c9 | 635 | /* |
02be5561 | 636 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
637 | * reader threads are calling rcu_register_thread(). |
638 | * Should only be called by a single thread at a given time. This is ensured by | |
731ccb96 MD |
639 | * holing the rcu_registry_lock from rcu_register_thread() or by running |
640 | * at library load time, which should not be executed by multiple | |
641 | * threads nor concurrently with rcu_register_thread() anyway. | |
8a5fb4c9 | 642 | */ |
02be5561 | 643 | void rcu_init(void) |
27b012e2 MD |
644 | { |
645 | struct sigaction act; | |
646 | int ret; | |
647 | ||
8a5fb4c9 MD |
648 | if (init_done) |
649 | return; | |
650 | init_done = 1; | |
651 | ||
02be5561 | 652 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 653 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 654 | sigemptyset(&act.sa_mask); |
02be5561 | 655 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
656 | if (ret) |
657 | urcu_die(errno); | |
27b012e2 | 658 | } |
ce28e67a | 659 | URCU_ATTR_ALIAS(urcu_stringify(rcu_init)) |
4477a870 | 660 | void alias_rcu_init(void); |
27b012e2 | 661 | |
02be5561 | 662 | void rcu_exit(void) |
27b012e2 | 663 | { |
71210954 MD |
664 | /* |
665 | * Don't unregister the SIGRCU signal handler anymore, because | |
666 | * call_rcu threads could still be using it shortly before the | |
667 | * application exits. | |
668 | * Assertion disabled because call_rcu threads are now rcu | |
669 | * readers, and left running at exit. | |
670 | * assert(cds_list_empty(®istry)); | |
671 | */ | |
27b012e2 | 672 | } |
ce28e67a | 673 | URCU_ATTR_ALIAS(urcu_stringify(rcu_exit)) |
4477a870 | 674 | void alias_rcu_exit(void); |
5e77fc1f | 675 | |
fdf01eed | 676 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 677 | |
5e6b23a6 | 678 | DEFINE_RCU_FLAVOR(rcu_flavor); |
4477a870 | 679 | DEFINE_RCU_FLAVOR_ALIAS(rcu_flavor, alias_rcu_flavor); |
541d828d | 680 | |
5e77fc1f | 681 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 682 | #include "urcu-defer-impl.h" |