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> | |
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 | |
375db287 | 40 | #include <urcu/config.h> |
01477510 | 41 | #include <urcu/assert.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; | |
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 | } | |
106 | #endif | |
8a5fb4c9 | 107 | |
fdf01eed MD |
108 | #ifdef RCU_SIGNAL |
109 | static int init_done; | |
110 | ||
111 | void __attribute__((constructor)) rcu_init(void); | |
112 | void __attribute__((destructor)) rcu_exit(void); | |
113 | #endif | |
114 | ||
731ccb96 MD |
115 | /* |
116 | * rcu_gp_lock ensures mutual exclusion between threads calling | |
117 | * synchronize_rcu(). | |
118 | */ | |
6abb4bd5 | 119 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
731ccb96 MD |
120 | /* |
121 | * rcu_registry_lock ensures mutual exclusion between threads | |
122 | * registering and unregistering themselves to/from the registry, and | |
123 | * with threads reading that registry from synchronize_rcu(). However, | |
124 | * this lock is not held all the way through the completion of awaiting | |
125 | * for the grace period. It is sporadically released between iterations | |
126 | * on the registry. | |
127 | * rcu_registry_lock may nest inside rcu_gp_lock. | |
128 | */ | |
129 | static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER; | |
4477a870 | 130 | struct urcu_gp rcu_gp = { .ctr = URCU_GP_COUNT }; |
27b012e2 | 131 | |
b0d5e790 MD |
132 | /* |
133 | * Written to only by each individual reader. Read by both the reader and the | |
134 | * writers. | |
135 | */ | |
4477a870 | 136 | DEFINE_URCU_TLS(struct urcu_reader, rcu_reader); |
27b012e2 | 137 | |
16aa9ee8 | 138 | static CDS_LIST_HEAD(registry); |
27b012e2 | 139 | |
5bffdd5d MD |
140 | /* |
141 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
142 | * struct gp_waiters_thread objects. | |
143 | */ | |
144 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
145 | ||
6abb4bd5 | 146 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
147 | { |
148 | int ret; | |
09a9f986 PM |
149 | |
150 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 151 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
152 | if (ret) |
153 | urcu_die(ret); | |
09a9f986 | 154 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 155 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
156 | if (ret != EBUSY && ret != EINTR) |
157 | urcu_die(ret); | |
bd252a04 | 158 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 159 | cmm_smp_mb(); |
bd252a04 | 160 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 161 | cmm_smp_mb(); |
09a9f986 | 162 | } |
8999a9ee | 163 | (void) poll(NULL, 0, 10); |
09a9f986 PM |
164 | } |
165 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
166 | } |
167 | ||
6abb4bd5 | 168 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
169 | { |
170 | int ret; | |
171 | ||
6abb4bd5 | 172 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
173 | if (ret) |
174 | urcu_die(ret); | |
41718ff9 MD |
175 | } |
176 | ||
fdf01eed | 177 | #ifdef RCU_MEMBARRIER |
a4922ed9 | 178 | static void smp_mb_master(void) |
fdf01eed | 179 | { |
4477a870 MD |
180 | if (caa_likely(urcu_memb_has_sys_membarrier)) { |
181 | if (membarrier(urcu_memb_has_sys_membarrier_private_expedited ? | |
c0bb9f69 MD |
182 | MEMBARRIER_CMD_PRIVATE_EXPEDITED : |
183 | MEMBARRIER_CMD_SHARED, 0)) | |
184 | urcu_die(errno); | |
185 | } else { | |
5481ddb3 | 186 | cmm_smp_mb(); |
c0bb9f69 | 187 | } |
fdf01eed MD |
188 | } |
189 | #endif | |
190 | ||
02be5561 | 191 | #ifdef RCU_MB |
a4922ed9 | 192 | static void smp_mb_master(void) |
40e140c9 | 193 | { |
5481ddb3 | 194 | cmm_smp_mb(); |
40e140c9 | 195 | } |
fdf01eed MD |
196 | #endif |
197 | ||
198 | #ifdef RCU_SIGNAL | |
78ff9419 | 199 | static void force_mb_all_readers(void) |
27b012e2 | 200 | { |
4477a870 | 201 | struct urcu_reader *index; |
e3b0cef0 | 202 | |
27b012e2 | 203 | /* |
5481ddb3 | 204 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
205 | * compiler barriers around rcu read lock as real memory barriers. |
206 | */ | |
16aa9ee8 | 207 | if (cds_list_empty(®istry)) |
27b012e2 | 208 | return; |
3a86deba | 209 | /* |
5481ddb3 | 210 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 211 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 212 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 213 | * cache flush is enforced. |
3a86deba | 214 | */ |
16aa9ee8 | 215 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 216 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 217 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 218 | } |
27b012e2 MD |
219 | /* |
220 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
221 | * |
222 | * Note that the pthread_kill() will never be executed on systems | |
223 | * that correctly deliver signals in a timely manner. However, it | |
224 | * is not uncommon for kernels to have bugs that can result in | |
225 | * lost or unduly delayed signals. | |
226 | * | |
227 | * If you are seeing the below pthread_kill() executing much at | |
228 | * all, we suggest testing the underlying kernel and filing the | |
229 | * relevant bug report. For Linux kernels, we recommend getting | |
230 | * the Linux Test Project (LTP). | |
27b012e2 | 231 | */ |
16aa9ee8 | 232 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 233 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 234 | pthread_kill(index->tid, SIGRCU); |
8999a9ee | 235 | (void) poll(NULL, 0, 1); |
09a9f986 PM |
236 | } |
237 | } | |
5481ddb3 | 238 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 239 | } |
9d7e3f89 | 240 | |
a4922ed9 | 241 | static void smp_mb_master(void) |
9d7e3f89 MD |
242 | { |
243 | force_mb_all_readers(); | |
244 | } | |
fdf01eed | 245 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 246 | |
bc6c15bb MD |
247 | /* |
248 | * synchronize_rcu() waiting. Single thread. | |
fca9fb96 MD |
249 | * Always called with rcu_registry lock held. Releases this lock and |
250 | * grabs it again. Holds the lock when it returns. | |
bc6c15bb | 251 | */ |
cfe78e25 | 252 | static void wait_gp(void) |
bc6c15bb | 253 | { |
fca9fb96 MD |
254 | /* |
255 | * Read reader_gp before read futex. smp_mb_master() needs to | |
256 | * be called with the rcu registry lock held in RCU_SIGNAL | |
257 | * flavor. | |
258 | */ | |
a4922ed9 | 259 | smp_mb_master(); |
fca9fb96 MD |
260 | /* Temporarily unlock the registry lock. */ |
261 | mutex_unlock(&rcu_registry_lock); | |
b0a841b4 | 262 | if (uatomic_read(&rcu_gp.futex) != -1) |
fca9fb96 | 263 | goto end; |
b0a841b4 MD |
264 | while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, |
265 | NULL, NULL, 0)) { | |
266 | switch (errno) { | |
267 | case EWOULDBLOCK: | |
268 | /* Value already changed. */ | |
fca9fb96 | 269 | goto end; |
b0a841b4 MD |
270 | case EINTR: |
271 | /* Retry if interrupted by signal. */ | |
272 | break; /* Get out of switch. */ | |
273 | default: | |
274 | /* Unexpected error. */ | |
275 | urcu_die(errno); | |
276 | } | |
277 | } | |
fca9fb96 MD |
278 | end: |
279 | /* | |
280 | * Re-lock the registry lock before the next loop. | |
281 | */ | |
282 | mutex_lock(&rcu_registry_lock); | |
bc6c15bb MD |
283 | } |
284 | ||
731ccb96 MD |
285 | /* |
286 | * Always called with rcu_registry lock held. Releases this lock between | |
287 | * iterations and grabs it again. Holds the lock when it returns. | |
288 | */ | |
fd189fa5 MD |
289 | static void wait_for_readers(struct cds_list_head *input_readers, |
290 | struct cds_list_head *cur_snap_readers, | |
291 | struct cds_list_head *qsreaders) | |
27b012e2 | 292 | { |
9340c38d | 293 | unsigned int wait_loops = 0; |
4477a870 | 294 | struct urcu_reader *index, *tmp; |
9340c38d MD |
295 | #ifdef HAS_INCOHERENT_CACHES |
296 | unsigned int wait_gp_loops = 0; | |
297 | #endif /* HAS_INCOHERENT_CACHES */ | |
27b012e2 | 298 | |
40e140c9 | 299 | /* |
c9488684 MD |
300 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
301 | * indicate quiescence (not nested), or observe the current | |
ed1b099e | 302 | * rcu_gp.ctr value. |
27b012e2 | 303 | */ |
cfe78e25 | 304 | for (;;) { |
5e81fed7 MD |
305 | if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) |
306 | wait_loops++; | |
9340c38d | 307 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
ed1b099e | 308 | uatomic_dec(&rcu_gp.futex); |
cfe78e25 | 309 | /* Write futex before read reader_gp */ |
a4922ed9 | 310 | smp_mb_master(); |
cfe78e25 MD |
311 | } |
312 | ||
fd189fa5 | 313 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
4477a870 MD |
314 | switch (urcu_common_reader_state(&rcu_gp, &index->ctr)) { |
315 | case URCU_READER_ACTIVE_CURRENT: | |
fd189fa5 MD |
316 | if (cur_snap_readers) { |
317 | cds_list_move(&index->node, | |
318 | cur_snap_readers); | |
319 | break; | |
320 | } | |
321 | /* Fall-through */ | |
4477a870 | 322 | case URCU_READER_INACTIVE: |
fd189fa5 MD |
323 | cds_list_move(&index->node, qsreaders); |
324 | break; | |
4477a870 | 325 | case URCU_READER_ACTIVE_OLD: |
fd189fa5 MD |
326 | /* |
327 | * Old snapshot. Leaving node in | |
328 | * input_readers will make us busy-loop | |
329 | * until the snapshot becomes current or | |
330 | * the reader becomes inactive. | |
331 | */ | |
332 | break; | |
333 | } | |
cfe78e25 MD |
334 | } |
335 | ||
e8043c1b | 336 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 337 | if (cds_list_empty(input_readers)) { |
9340c38d | 338 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 339 | /* Read reader_gp before write futex */ |
a4922ed9 | 340 | smp_mb_master(); |
ed1b099e | 341 | uatomic_set(&rcu_gp.futex, 0); |
bc6c15bb | 342 | } |
cfe78e25 MD |
343 | break; |
344 | } else { | |
fca9fb96 MD |
345 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
346 | /* wait_gp unlocks/locks registry lock. */ | |
cfe78e25 | 347 | wait_gp(); |
fca9fb96 MD |
348 | } else { |
349 | /* Temporarily unlock the registry lock. */ | |
350 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 351 | caa_cpu_relax(); |
fca9fb96 MD |
352 | /* |
353 | * Re-lock the registry lock before the | |
354 | * next loop. | |
355 | */ | |
356 | mutex_lock(&rcu_registry_lock); | |
357 | } | |
bc6c15bb | 358 | } |
e8043c1b | 359 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 360 | /* |
40e140c9 | 361 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
362 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
363 | * for too long. | |
27b012e2 | 364 | */ |
fd189fa5 | 365 | if (cds_list_empty(input_readers)) { |
9340c38d | 366 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 367 | /* Read reader_gp before write futex */ |
a4922ed9 | 368 | smp_mb_master(); |
ed1b099e | 369 | uatomic_set(&rcu_gp.futex, 0); |
cfe78e25 MD |
370 | } |
371 | break; | |
372 | } else { | |
9340c38d | 373 | if (wait_gp_loops == KICK_READER_LOOPS) { |
a4922ed9 | 374 | smp_mb_master(); |
9340c38d MD |
375 | wait_gp_loops = 0; |
376 | } | |
377 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { | |
fca9fb96 | 378 | /* wait_gp unlocks/locks registry lock. */ |
9340c38d MD |
379 | wait_gp(); |
380 | wait_gp_loops++; | |
381 | } else { | |
fca9fb96 MD |
382 | /* Temporarily unlock the registry lock. */ |
383 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 384 | caa_cpu_relax(); |
fca9fb96 MD |
385 | /* |
386 | * Re-lock the registry lock before the | |
387 | * next loop. | |
388 | */ | |
389 | mutex_lock(&rcu_registry_lock); | |
40e140c9 MD |
390 | } |
391 | } | |
e8043c1b | 392 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 393 | } |
27b012e2 MD |
394 | } |
395 | ||
9598a481 | 396 | void synchronize_rcu(void) |
2bc59bd7 | 397 | { |
fd189fa5 MD |
398 | CDS_LIST_HEAD(cur_snap_readers); |
399 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
400 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
401 | struct urcu_waiters waiters; | |
402 | ||
403 | /* | |
404 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
405 | * for a grace period. Proceed to perform the grace period only | |
406 | * if we are the first thread added into the queue. | |
407 | * The implicit memory barrier before urcu_wait_add() | |
408 | * orders prior memory accesses of threads put into the wait | |
409 | * queue before their insertion into the wait queue. | |
410 | */ | |
411 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
412 | /* Not first in queue: will be awakened by another thread. */ | |
413 | urcu_adaptative_busy_wait(&wait); | |
414 | /* Order following memory accesses after grace period. */ | |
415 | cmm_smp_mb(); | |
416 | return; | |
417 | } | |
418 | /* We won't need to wake ourself up */ | |
419 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 420 | |
6abb4bd5 | 421 | mutex_lock(&rcu_gp_lock); |
135530fd | 422 | |
5bffdd5d MD |
423 | /* |
424 | * Move all waiters into our local queue. | |
425 | */ | |
426 | urcu_move_waiters(&waiters, &gp_waiters); | |
427 | ||
731ccb96 MD |
428 | mutex_lock(&rcu_registry_lock); |
429 | ||
16aa9ee8 | 430 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
431 | goto out; |
432 | ||
731ccb96 MD |
433 | /* |
434 | * All threads should read qparity before accessing data structure | |
435 | * where new ptr points to. Must be done within rcu_registry_lock | |
436 | * because it iterates on reader threads. | |
437 | */ | |
9598a481 | 438 | /* Write new ptr before changing the qparity */ |
a4922ed9 | 439 | smp_mb_master(); |
9598a481 | 440 | |
9598a481 | 441 | /* |
c9488684 | 442 | * Wait for readers to observe original parity or be quiescent. |
731ccb96 | 443 | * wait_for_readers() can release and grab again rcu_registry_lock |
f99c6e92 | 444 | * internally. |
9598a481 | 445 | */ |
fd189fa5 | 446 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
447 | |
448 | /* | |
c9488684 | 449 | * Must finish waiting for quiescent state for original parity before |
ed1b099e | 450 | * committing next rcu_gp.ctr update to memory. Failure to do so could |
d40fde2c MD |
451 | * result in the writer waiting forever while new readers are always |
452 | * accessing data (no progress). Enforce compiler-order of load | |
ed1b099e | 453 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr. |
9598a481 | 454 | */ |
5481ddb3 | 455 | cmm_barrier(); |
9598a481 | 456 | |
5dba80f9 | 457 | /* |
5481ddb3 | 458 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
459 | * model easier to understand. It does not have a big performance impact |
460 | * anyway, given this is the write-side. | |
461 | */ | |
5481ddb3 | 462 | cmm_smp_mb(); |
67c2d80b | 463 | |
c9488684 | 464 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
4477a870 | 465 | CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ URCU_GP_CTR_PHASE); |
c9488684 MD |
466 | |
467 | /* | |
ed1b099e | 468 | * Must commit rcu_gp.ctr update to memory before waiting for quiescent |
c9488684 MD |
469 | * state. Failure to do so could result in the writer waiting forever |
470 | * while new readers are always accessing data (no progress). Enforce | |
ed1b099e | 471 | * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr. |
c9488684 MD |
472 | */ |
473 | cmm_barrier(); | |
474 | ||
475 | /* | |
476 | * | |
477 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
478 | * model easier to understand. It does not have a big performance impact | |
479 | * anyway, given this is the write-side. | |
480 | */ | |
481 | cmm_smp_mb(); | |
482 | ||
9598a481 | 483 | /* |
c9488684 | 484 | * Wait for readers to observe new parity or be quiescent. |
731ccb96 | 485 | * wait_for_readers() can release and grab again rcu_registry_lock |
f99c6e92 | 486 | * internally. |
9598a481 | 487 | */ |
fd189fa5 MD |
488 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
489 | ||
490 | /* | |
491 | * Put quiescent reader list back into registry. | |
492 | */ | |
493 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 494 | |
731ccb96 MD |
495 | /* |
496 | * Finish waiting for reader threads before letting the old ptr | |
497 | * being freed. Must be done within rcu_registry_lock because it | |
498 | * iterates on reader threads. | |
499 | */ | |
a4922ed9 | 500 | smp_mb_master(); |
2dfb8b5e | 501 | out: |
731ccb96 | 502 | mutex_unlock(&rcu_registry_lock); |
6abb4bd5 | 503 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
504 | |
505 | /* | |
506 | * Wakeup waiters only after we have completed the grace period | |
507 | * and have ensured the memory barriers at the end of the grace | |
508 | * period have been issued. | |
509 | */ | |
510 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 PM |
511 | } |
512 | ||
121a5d44 MD |
513 | /* |
514 | * library wrappers to be used by non-LGPL compatible source code. | |
515 | */ | |
516 | ||
517 | void rcu_read_lock(void) | |
518 | { | |
519 | _rcu_read_lock(); | |
520 | } | |
521 | ||
522 | void rcu_read_unlock(void) | |
523 | { | |
524 | _rcu_read_unlock(); | |
525 | } | |
526 | ||
882f3357 MD |
527 | int rcu_read_ongoing(void) |
528 | { | |
529 | return _rcu_read_ongoing(); | |
530 | } | |
531 | ||
121a5d44 | 532 | void rcu_register_thread(void) |
27b012e2 | 533 | { |
bd252a04 | 534 | URCU_TLS(rcu_reader).tid = pthread_self(); |
01477510 FD |
535 | urcu_posix_assert(URCU_TLS(rcu_reader).need_mb == 0); |
536 | urcu_posix_assert(!(URCU_TLS(rcu_reader).ctr & URCU_GP_CTR_NEST_MASK)); | |
02be5561 | 537 | |
731ccb96 | 538 | mutex_lock(&rcu_registry_lock); |
01477510 | 539 | urcu_posix_assert(!URCU_TLS(rcu_reader).registered); |
a77f7d82 | 540 | URCU_TLS(rcu_reader).registered = 1; |
02be5561 | 541 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 542 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
731ccb96 | 543 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
544 | } |
545 | ||
121a5d44 | 546 | void rcu_unregister_thread(void) |
27b012e2 | 547 | { |
731ccb96 | 548 | mutex_lock(&rcu_registry_lock); |
01477510 | 549 | urcu_posix_assert(URCU_TLS(rcu_reader).registered); |
a77f7d82 | 550 | URCU_TLS(rcu_reader).registered = 0; |
bd252a04 | 551 | cds_list_del(&URCU_TLS(rcu_reader).node); |
731ccb96 | 552 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
553 | } |
554 | ||
fdf01eed | 555 | #ifdef RCU_MEMBARRIER |
d8d9a340 MD |
556 | |
557 | #ifdef CONFIG_RCU_FORCE_SYS_MEMBARRIER | |
558 | static | |
c0bb9f69 | 559 | void rcu_sys_membarrier_status(bool available) |
d8d9a340 MD |
560 | { |
561 | if (!available) | |
562 | abort(); | |
563 | } | |
564 | #else | |
565 | static | |
c0bb9f69 | 566 | void rcu_sys_membarrier_status(bool available) |
d8d9a340 | 567 | { |
c0bb9f69 MD |
568 | if (!available) |
569 | return; | |
4477a870 | 570 | urcu_memb_has_sys_membarrier = 1; |
d8d9a340 MD |
571 | } |
572 | #endif | |
573 | ||
c0bb9f69 MD |
574 | static |
575 | void rcu_sys_membarrier_init(void) | |
fdf01eed | 576 | { |
c0bb9f69 MD |
577 | bool available = false; |
578 | int mask; | |
579 | ||
580 | mask = membarrier(MEMBARRIER_CMD_QUERY, 0); | |
581 | if (mask >= 0) { | |
582 | if (mask & MEMBARRIER_CMD_PRIVATE_EXPEDITED) { | |
583 | if (membarrier(MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED, 0)) | |
584 | urcu_die(errno); | |
4477a870 | 585 | urcu_memb_has_sys_membarrier_private_expedited = 1; |
c0bb9f69 MD |
586 | available = true; |
587 | } else if (mask & MEMBARRIER_CMD_SHARED) { | |
588 | available = true; | |
589 | } | |
590 | } | |
591 | rcu_sys_membarrier_status(available); | |
592 | } | |
64f469e6 | 593 | |
c0bb9f69 MD |
594 | void rcu_init(void) |
595 | { | |
fdf01eed MD |
596 | if (init_done) |
597 | return; | |
598 | init_done = 1; | |
c0bb9f69 | 599 | rcu_sys_membarrier_init(); |
fdf01eed MD |
600 | } |
601 | #endif | |
602 | ||
603 | #ifdef RCU_SIGNAL | |
70469b43 MJ |
604 | static void sigrcu_handler(int signo __attribute__((unused)), |
605 | siginfo_t *siginfo __attribute__((unused)), | |
606 | void *context __attribute__((unused))) | |
27b012e2 | 607 | { |
40e140c9 | 608 | /* |
5481ddb3 DG |
609 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
610 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
611 | * executed on. |
612 | */ | |
5481ddb3 | 613 | cmm_smp_mb(); |
bd252a04 | 614 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 615 | cmm_smp_mb(); |
27b012e2 MD |
616 | } |
617 | ||
8a5fb4c9 | 618 | /* |
02be5561 | 619 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
620 | * reader threads are calling rcu_register_thread(). |
621 | * Should only be called by a single thread at a given time. This is ensured by | |
731ccb96 MD |
622 | * holing the rcu_registry_lock from rcu_register_thread() or by running |
623 | * at library load time, which should not be executed by multiple | |
624 | * threads nor concurrently with rcu_register_thread() anyway. | |
8a5fb4c9 | 625 | */ |
02be5561 | 626 | void rcu_init(void) |
27b012e2 MD |
627 | { |
628 | struct sigaction act; | |
629 | int ret; | |
630 | ||
8a5fb4c9 MD |
631 | if (init_done) |
632 | return; | |
633 | init_done = 1; | |
634 | ||
02be5561 | 635 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 636 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 637 | sigemptyset(&act.sa_mask); |
02be5561 | 638 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
639 | if (ret) |
640 | urcu_die(errno); | |
27b012e2 MD |
641 | } |
642 | ||
02be5561 | 643 | void rcu_exit(void) |
27b012e2 | 644 | { |
71210954 MD |
645 | /* |
646 | * Don't unregister the SIGRCU signal handler anymore, because | |
647 | * call_rcu threads could still be using it shortly before the | |
648 | * application exits. | |
649 | * Assertion disabled because call_rcu threads are now rcu | |
650 | * readers, and left running at exit. | |
01477510 | 651 | * urcu_posix_assert(cds_list_empty(®istry)); |
71210954 | 652 | */ |
27b012e2 | 653 | } |
5e77fc1f | 654 | |
fdf01eed | 655 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 656 | |
5e6b23a6 | 657 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 658 | |
5e77fc1f | 659 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 660 | #include "urcu-defer-impl.h" |