Commit | Line | Data |
---|---|---|
b257a10b MD |
1 | /* |
2 | * urcu.c | |
3 | * | |
4 | * Userspace RCU library | |
5 | * | |
6982d6d7 | 6 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
af02d47e | 7 | * Copyright (c) 2009 Paul E. McKenney, IBM Corporation. |
b257a10b | 8 | * |
af02d47e MD |
9 | * This library is free software; you can redistribute it and/or |
10 | * modify it under the terms of the GNU Lesser General Public | |
11 | * License as published by the Free Software Foundation; either | |
12 | * version 2.1 of the License, or (at your option) any later version. | |
13 | * | |
14 | * This library is distributed in the hope that it will be useful, | |
15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
17 | * Lesser General Public License for more details. | |
18 | * | |
19 | * You should have received a copy of the GNU Lesser General Public | |
20 | * License along with this library; if not, write to the Free Software | |
21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
54843abc PM |
22 | * |
23 | * IBM's contributions to this file may be relicensed under LGPLv2 or later. | |
b257a10b MD |
24 | */ |
25 | ||
fdf01eed | 26 | #define _BSD_SOURCE |
c1d2c60b | 27 | #define _GNU_SOURCE |
71c811bf | 28 | #define _LGPL_SOURCE |
9d4624e5 | 29 | #define _DEFAULT_SOURCE |
27b012e2 MD |
30 | #include <stdio.h> |
31 | #include <pthread.h> | |
32 | #include <signal.h> | |
33 | #include <assert.h> | |
f69f195a | 34 | #include <stdlib.h> |
6d841bc2 | 35 | #include <stdint.h> |
f69f195a | 36 | #include <string.h> |
09a9f986 | 37 | #include <errno.h> |
e8043c1b | 38 | #include <poll.h> |
27b012e2 | 39 | |
d73fb81f | 40 | #include "urcu/wfcqueue.h" |
57760d44 | 41 | #include "urcu/map/urcu.h" |
af7c2dbe | 42 | #include "urcu/static/urcu.h" |
618b2595 | 43 | #include "urcu-pointer.h" |
bd252a04 | 44 | #include "urcu/tls-compat.h" |
71c811bf | 45 | |
4a6d7378 | 46 | #include "urcu-die.h" |
5bffdd5d | 47 | #include "urcu-wait.h" |
4a6d7378 | 48 | |
121a5d44 | 49 | /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ |
71c811bf | 50 | #undef _LGPL_SOURCE |
27b012e2 | 51 | #include "urcu.h" |
71c811bf | 52 | #define _LGPL_SOURCE |
27b012e2 | 53 | |
3a71751e PB |
54 | /* |
55 | * If a reader is really non-cooperative and refuses to commit its | |
56 | * rcu_active_readers count to memory (there is no barrier in the reader | |
e198fb6a | 57 | * per-se), kick it after 10 loops waiting for it. |
3a71751e | 58 | */ |
e198fb6a | 59 | #define KICK_READER_LOOPS 10 |
3a71751e PB |
60 | |
61 | /* | |
62 | * Active attempts to check for reader Q.S. before calling futex(). | |
63 | */ | |
64 | #define RCU_QS_ACTIVE_ATTEMPTS 100 | |
65 | ||
553b7eb9 | 66 | /* |
eaaff0fe MD |
67 | * The ABI of sys_membarrier changed after its original implementation. |
68 | * Disable it for now. Use RCU_MB flavor instead. | |
553b7eb9 | 69 | */ |
eaaff0fe | 70 | #define membarrier(...) -ENOSYS |
553b7eb9 MD |
71 | |
72 | #define MEMBARRIER_EXPEDITED (1 << 0) | |
73 | #define MEMBARRIER_DELAYED (1 << 1) | |
74 | #define MEMBARRIER_QUERY (1 << 16) | |
75 | ||
fdf01eed | 76 | #ifdef RCU_MEMBARRIER |
834a45ba | 77 | static int init_done; |
1de4df4b | 78 | int rcu_has_sys_membarrier; |
834a45ba | 79 | |
02be5561 | 80 | void __attribute__((constructor)) rcu_init(void); |
fdf01eed MD |
81 | #endif |
82 | ||
83 | #ifdef RCU_MB | |
02be5561 | 84 | void rcu_init(void) |
e90a6e9c MD |
85 | { |
86 | } | |
87 | #endif | |
8a5fb4c9 | 88 | |
fdf01eed MD |
89 | #ifdef RCU_SIGNAL |
90 | static int init_done; | |
91 | ||
92 | void __attribute__((constructor)) rcu_init(void); | |
93 | void __attribute__((destructor)) rcu_exit(void); | |
94 | #endif | |
95 | ||
3c29ca5d MD |
96 | /* |
97 | * rcu_gp_lock ensures mutual exclusion between threads calling | |
98 | * synchronize_rcu(). | |
99 | */ | |
6abb4bd5 | 100 | static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; |
3c29ca5d MD |
101 | /* |
102 | * rcu_registry_lock ensures mutual exclusion between threads | |
103 | * registering and unregistering themselves to/from the registry, and | |
104 | * with threads reading that registry from synchronize_rcu(). However, | |
105 | * this lock is not held all the way through the completion of awaiting | |
106 | * for the grace period. It is sporadically released between iterations | |
107 | * on the registry. | |
108 | * rcu_registry_lock may nest inside rcu_gp_lock. | |
109 | */ | |
110 | static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER; | |
4de0cd31 | 111 | struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT }; |
27b012e2 | 112 | |
b0d5e790 MD |
113 | /* |
114 | * Written to only by each individual reader. Read by both the reader and the | |
115 | * writers. | |
116 | */ | |
1182f6f0 | 117 | __DEFINE_URCU_TLS_GLOBAL(struct rcu_reader, rcu_reader); |
27b012e2 | 118 | |
16aa9ee8 | 119 | static CDS_LIST_HEAD(registry); |
27b012e2 | 120 | |
5bffdd5d MD |
121 | /* |
122 | * Queue keeping threads awaiting to wait for a grace period. Contains | |
123 | * struct gp_waiters_thread objects. | |
124 | */ | |
125 | static DEFINE_URCU_WAIT_QUEUE(gp_waiters); | |
126 | ||
6abb4bd5 | 127 | static void mutex_lock(pthread_mutex_t *mutex) |
41718ff9 MD |
128 | { |
129 | int ret; | |
09a9f986 PM |
130 | |
131 | #ifndef DISTRUST_SIGNALS_EXTREME | |
6abb4bd5 | 132 | ret = pthread_mutex_lock(mutex); |
4a6d7378 MD |
133 | if (ret) |
134 | urcu_die(ret); | |
09a9f986 | 135 | #else /* #ifndef DISTRUST_SIGNALS_EXTREME */ |
6abb4bd5 | 136 | while ((ret = pthread_mutex_trylock(mutex)) != 0) { |
4a6d7378 MD |
137 | if (ret != EBUSY && ret != EINTR) |
138 | urcu_die(ret); | |
bd252a04 | 139 | if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) { |
5481ddb3 | 140 | cmm_smp_mb(); |
bd252a04 | 141 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 142 | cmm_smp_mb(); |
09a9f986 PM |
143 | } |
144 | poll(NULL,0,10); | |
145 | } | |
146 | #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */ | |
41718ff9 MD |
147 | } |
148 | ||
6abb4bd5 | 149 | static void mutex_unlock(pthread_mutex_t *mutex) |
41718ff9 MD |
150 | { |
151 | int ret; | |
152 | ||
6abb4bd5 | 153 | ret = pthread_mutex_unlock(mutex); |
4a6d7378 MD |
154 | if (ret) |
155 | urcu_die(ret); | |
41718ff9 MD |
156 | } |
157 | ||
fdf01eed | 158 | #ifdef RCU_MEMBARRIER |
25cc6d18 | 159 | static void smp_mb_master(int group) |
fdf01eed | 160 | { |
1de4df4b | 161 | if (caa_likely(rcu_has_sys_membarrier)) |
553b7eb9 | 162 | (void) membarrier(MEMBARRIER_EXPEDITED); |
fdf01eed | 163 | else |
5481ddb3 | 164 | cmm_smp_mb(); |
fdf01eed MD |
165 | } |
166 | #endif | |
167 | ||
02be5561 | 168 | #ifdef RCU_MB |
25cc6d18 | 169 | static void smp_mb_master(int group) |
40e140c9 | 170 | { |
5481ddb3 | 171 | cmm_smp_mb(); |
40e140c9 | 172 | } |
fdf01eed MD |
173 | #endif |
174 | ||
175 | #ifdef RCU_SIGNAL | |
78ff9419 | 176 | static void force_mb_all_readers(void) |
27b012e2 | 177 | { |
02be5561 | 178 | struct rcu_reader *index; |
e3b0cef0 | 179 | |
27b012e2 | 180 | /* |
5481ddb3 | 181 | * Ask for each threads to execute a cmm_smp_mb() so we can consider the |
27b012e2 MD |
182 | * compiler barriers around rcu read lock as real memory barriers. |
183 | */ | |
16aa9ee8 | 184 | if (cds_list_empty(®istry)) |
27b012e2 | 185 | return; |
3a86deba | 186 | /* |
5481ddb3 | 187 | * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs |
157dca95 | 188 | * a cache flush on architectures with non-coherent cache. Let's play |
5481ddb3 | 189 | * safe and don't assume anything : we use cmm_smp_mc() to make sure the |
157dca95 | 190 | * cache flush is enforced. |
3a86deba | 191 | */ |
16aa9ee8 | 192 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 193 | CMM_STORE_SHARED(index->need_mb, 1); |
02be5561 | 194 | pthread_kill(index->tid, SIGRCU); |
09a9f986 | 195 | } |
27b012e2 MD |
196 | /* |
197 | * Wait for sighandler (and thus mb()) to execute on every thread. | |
09a9f986 PM |
198 | * |
199 | * Note that the pthread_kill() will never be executed on systems | |
200 | * that correctly deliver signals in a timely manner. However, it | |
201 | * is not uncommon for kernels to have bugs that can result in | |
202 | * lost or unduly delayed signals. | |
203 | * | |
204 | * If you are seeing the below pthread_kill() executing much at | |
205 | * all, we suggest testing the underlying kernel and filing the | |
206 | * relevant bug report. For Linux kernels, we recommend getting | |
207 | * the Linux Test Project (LTP). | |
27b012e2 | 208 | */ |
16aa9ee8 | 209 | cds_list_for_each_entry(index, ®istry, node) { |
6cf3827c | 210 | while (CMM_LOAD_SHARED(index->need_mb)) { |
02be5561 | 211 | pthread_kill(index->tid, SIGRCU); |
09a9f986 PM |
212 | poll(NULL, 0, 1); |
213 | } | |
214 | } | |
5481ddb3 | 215 | cmm_smp_mb(); /* read ->need_mb before ending the barrier */ |
27b012e2 | 216 | } |
9d7e3f89 | 217 | |
25cc6d18 | 218 | static void smp_mb_master(int group) |
9d7e3f89 MD |
219 | { |
220 | force_mb_all_readers(); | |
221 | } | |
fdf01eed | 222 | #endif /* #ifdef RCU_SIGNAL */ |
27b012e2 | 223 | |
bc6c15bb MD |
224 | /* |
225 | * synchronize_rcu() waiting. Single thread. | |
863585dc MD |
226 | * Always called with rcu_registry lock held. Releases this lock and |
227 | * grabs it again. Holds the lock when it returns. | |
bc6c15bb | 228 | */ |
cfe78e25 | 229 | static void wait_gp(void) |
bc6c15bb | 230 | { |
863585dc MD |
231 | /* |
232 | * Read reader_gp before read futex. smp_mb_master() needs to | |
233 | * be called with the rcu registry lock held in RCU_SIGNAL | |
234 | * flavor. | |
235 | */ | |
25cc6d18 | 236 | smp_mb_master(RCU_MB_GROUP); |
863585dc MD |
237 | /* Temporarily unlock the registry lock. */ |
238 | mutex_unlock(&rcu_registry_lock); | |
52c67a3d | 239 | if (uatomic_read(&rcu_gp.futex) != -1) |
863585dc | 240 | goto end; |
52c67a3d MD |
241 | while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1, |
242 | NULL, NULL, 0)) { | |
243 | switch (errno) { | |
244 | case EWOULDBLOCK: | |
245 | /* Value already changed. */ | |
863585dc | 246 | goto end; |
52c67a3d MD |
247 | case EINTR: |
248 | /* Retry if interrupted by signal. */ | |
249 | break; /* Get out of switch. */ | |
250 | default: | |
251 | /* Unexpected error. */ | |
252 | urcu_die(errno); | |
253 | } | |
254 | } | |
863585dc MD |
255 | end: |
256 | /* | |
257 | * Re-lock the registry lock before the next loop. | |
258 | */ | |
259 | mutex_lock(&rcu_registry_lock); | |
bc6c15bb MD |
260 | } |
261 | ||
3c29ca5d MD |
262 | /* |
263 | * Always called with rcu_registry lock held. Releases this lock between | |
264 | * iterations and grabs it again. Holds the lock when it returns. | |
265 | */ | |
fd189fa5 MD |
266 | static void wait_for_readers(struct cds_list_head *input_readers, |
267 | struct cds_list_head *cur_snap_readers, | |
268 | struct cds_list_head *qsreaders) | |
27b012e2 | 269 | { |
e198fb6a | 270 | unsigned int wait_loops = 0; |
02be5561 | 271 | struct rcu_reader *index, *tmp; |
e198fb6a MD |
272 | #ifdef HAS_INCOHERENT_CACHES |
273 | unsigned int wait_gp_loops = 0; | |
274 | #endif /* HAS_INCOHERENT_CACHES */ | |
27b012e2 | 275 | |
40e140c9 | 276 | /* |
c9488684 MD |
277 | * Wait for each thread URCU_TLS(rcu_reader).ctr to either |
278 | * indicate quiescence (not nested), or observe the current | |
ed1b099e | 279 | * rcu_gp.ctr value. |
27b012e2 | 280 | */ |
cfe78e25 | 281 | for (;;) { |
f2aa4905 MD |
282 | if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS) |
283 | wait_loops++; | |
e198fb6a | 284 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
ed1b099e | 285 | uatomic_dec(&rcu_gp.futex); |
cfe78e25 | 286 | /* Write futex before read reader_gp */ |
25cc6d18 | 287 | smp_mb_master(RCU_MB_GROUP); |
cfe78e25 MD |
288 | } |
289 | ||
fd189fa5 MD |
290 | cds_list_for_each_entry_safe(index, tmp, input_readers, node) { |
291 | switch (rcu_reader_state(&index->ctr)) { | |
292 | case RCU_READER_ACTIVE_CURRENT: | |
293 | if (cur_snap_readers) { | |
294 | cds_list_move(&index->node, | |
295 | cur_snap_readers); | |
296 | break; | |
297 | } | |
298 | /* Fall-through */ | |
299 | case RCU_READER_INACTIVE: | |
300 | cds_list_move(&index->node, qsreaders); | |
301 | break; | |
302 | case RCU_READER_ACTIVE_OLD: | |
303 | /* | |
304 | * Old snapshot. Leaving node in | |
305 | * input_readers will make us busy-loop | |
306 | * until the snapshot becomes current or | |
307 | * the reader becomes inactive. | |
308 | */ | |
309 | break; | |
310 | } | |
cfe78e25 MD |
311 | } |
312 | ||
e8043c1b | 313 | #ifndef HAS_INCOHERENT_CACHES |
fd189fa5 | 314 | if (cds_list_empty(input_readers)) { |
e198fb6a | 315 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 316 | /* Read reader_gp before write futex */ |
25cc6d18 | 317 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e | 318 | uatomic_set(&rcu_gp.futex, 0); |
bc6c15bb | 319 | } |
cfe78e25 MD |
320 | break; |
321 | } else { | |
863585dc MD |
322 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
323 | /* wait_gp unlocks/locks registry lock. */ | |
cfe78e25 | 324 | wait_gp(); |
863585dc MD |
325 | } else { |
326 | /* Temporarily unlock the registry lock. */ | |
327 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 328 | caa_cpu_relax(); |
863585dc MD |
329 | /* |
330 | * Re-lock the registry lock before the | |
331 | * next loop. | |
332 | */ | |
333 | mutex_lock(&rcu_registry_lock); | |
334 | } | |
bc6c15bb | 335 | } |
e8043c1b | 336 | #else /* #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 337 | /* |
40e140c9 | 338 | * BUSY-LOOP. Force the reader thread to commit its |
bd252a04 MD |
339 | * URCU_TLS(rcu_reader).ctr update to memory if we wait |
340 | * for too long. | |
27b012e2 | 341 | */ |
fd189fa5 | 342 | if (cds_list_empty(input_readers)) { |
e198fb6a | 343 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { |
cfe78e25 | 344 | /* Read reader_gp before write futex */ |
25cc6d18 | 345 | smp_mb_master(RCU_MB_GROUP); |
ed1b099e | 346 | uatomic_set(&rcu_gp.futex, 0); |
cfe78e25 MD |
347 | } |
348 | break; | |
349 | } else { | |
e198fb6a | 350 | if (wait_gp_loops == KICK_READER_LOOPS) { |
25cc6d18 | 351 | smp_mb_master(RCU_MB_GROUP); |
e198fb6a MD |
352 | wait_gp_loops = 0; |
353 | } | |
354 | if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { | |
863585dc | 355 | /* wait_gp unlocks/locks registry lock. */ |
e198fb6a MD |
356 | wait_gp(); |
357 | wait_gp_loops++; | |
358 | } else { | |
863585dc MD |
359 | /* Temporarily unlock the registry lock. */ |
360 | mutex_unlock(&rcu_registry_lock); | |
06f22bdb | 361 | caa_cpu_relax(); |
863585dc MD |
362 | /* |
363 | * Re-lock the registry lock before the | |
364 | * next loop. | |
365 | */ | |
366 | mutex_lock(&rcu_registry_lock); | |
40e140c9 MD |
367 | } |
368 | } | |
e8043c1b | 369 | #endif /* #else #ifndef HAS_INCOHERENT_CACHES */ |
27b012e2 | 370 | } |
27b012e2 MD |
371 | } |
372 | ||
9598a481 | 373 | void synchronize_rcu(void) |
2bc59bd7 | 374 | { |
fd189fa5 MD |
375 | CDS_LIST_HEAD(cur_snap_readers); |
376 | CDS_LIST_HEAD(qsreaders); | |
5bffdd5d MD |
377 | DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING); |
378 | struct urcu_waiters waiters; | |
379 | ||
380 | /* | |
381 | * Add ourself to gp_waiters queue of threads awaiting to wait | |
382 | * for a grace period. Proceed to perform the grace period only | |
383 | * if we are the first thread added into the queue. | |
384 | * The implicit memory barrier before urcu_wait_add() | |
385 | * orders prior memory accesses of threads put into the wait | |
386 | * queue before their insertion into the wait queue. | |
387 | */ | |
388 | if (urcu_wait_add(&gp_waiters, &wait) != 0) { | |
389 | /* Not first in queue: will be awakened by another thread. */ | |
390 | urcu_adaptative_busy_wait(&wait); | |
391 | /* Order following memory accesses after grace period. */ | |
392 | cmm_smp_mb(); | |
393 | return; | |
394 | } | |
395 | /* We won't need to wake ourself up */ | |
396 | urcu_wait_set_state(&wait, URCU_WAIT_RUNNING); | |
fd189fa5 | 397 | |
6abb4bd5 | 398 | mutex_lock(&rcu_gp_lock); |
135530fd | 399 | |
5bffdd5d MD |
400 | /* |
401 | * Move all waiters into our local queue. | |
402 | */ | |
403 | urcu_move_waiters(&waiters, &gp_waiters); | |
404 | ||
3c29ca5d MD |
405 | mutex_lock(&rcu_registry_lock); |
406 | ||
16aa9ee8 | 407 | if (cds_list_empty(®istry)) |
2dfb8b5e MD |
408 | goto out; |
409 | ||
3c29ca5d MD |
410 | /* |
411 | * All threads should read qparity before accessing data structure | |
412 | * where new ptr points to. Must be done within rcu_registry_lock | |
413 | * because it iterates on reader threads. | |
414 | */ | |
9598a481 | 415 | /* Write new ptr before changing the qparity */ |
25cc6d18 | 416 | smp_mb_master(RCU_MB_GROUP); |
9598a481 | 417 | |
9598a481 | 418 | /* |
c9488684 | 419 | * Wait for readers to observe original parity or be quiescent. |
3c29ca5d MD |
420 | * wait_for_readers() can release and grab again rcu_registry_lock |
421 | * interally. | |
9598a481 | 422 | */ |
fd189fa5 | 423 | wait_for_readers(®istry, &cur_snap_readers, &qsreaders); |
9598a481 MD |
424 | |
425 | /* | |
c9488684 | 426 | * Must finish waiting for quiescent state for original parity before |
ed1b099e | 427 | * committing next rcu_gp.ctr update to memory. Failure to do so could |
d40fde2c MD |
428 | * result in the writer waiting forever while new readers are always |
429 | * accessing data (no progress). Enforce compiler-order of load | |
ed1b099e | 430 | * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr. |
9598a481 | 431 | */ |
5481ddb3 | 432 | cmm_barrier(); |
9598a481 | 433 | |
5dba80f9 | 434 | /* |
5481ddb3 | 435 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the |
5dba80f9 MD |
436 | * model easier to understand. It does not have a big performance impact |
437 | * anyway, given this is the write-side. | |
438 | */ | |
5481ddb3 | 439 | cmm_smp_mb(); |
67c2d80b | 440 | |
c9488684 | 441 | /* Switch parity: 0 -> 1, 1 -> 0 */ |
ed1b099e | 442 | CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE); |
c9488684 MD |
443 | |
444 | /* | |
ed1b099e | 445 | * Must commit rcu_gp.ctr update to memory before waiting for quiescent |
c9488684 MD |
446 | * state. Failure to do so could result in the writer waiting forever |
447 | * while new readers are always accessing data (no progress). Enforce | |
ed1b099e | 448 | * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr. |
c9488684 MD |
449 | */ |
450 | cmm_barrier(); | |
451 | ||
452 | /* | |
453 | * | |
454 | * Adding a cmm_smp_mb() which is _not_ formally required, but makes the | |
455 | * model easier to understand. It does not have a big performance impact | |
456 | * anyway, given this is the write-side. | |
457 | */ | |
458 | cmm_smp_mb(); | |
459 | ||
9598a481 | 460 | /* |
c9488684 | 461 | * Wait for readers to observe new parity or be quiescent. |
3c29ca5d MD |
462 | * wait_for_readers() can release and grab again rcu_registry_lock |
463 | * interally. | |
9598a481 | 464 | */ |
fd189fa5 MD |
465 | wait_for_readers(&cur_snap_readers, NULL, &qsreaders); |
466 | ||
467 | /* | |
468 | * Put quiescent reader list back into registry. | |
469 | */ | |
470 | cds_list_splice(&qsreaders, ®istry); | |
9598a481 | 471 | |
3c29ca5d MD |
472 | /* |
473 | * Finish waiting for reader threads before letting the old ptr | |
474 | * being freed. Must be done within rcu_registry_lock because it | |
475 | * iterates on reader threads. | |
476 | */ | |
25cc6d18 | 477 | smp_mb_master(RCU_MB_GROUP); |
2dfb8b5e | 478 | out: |
3c29ca5d | 479 | mutex_unlock(&rcu_registry_lock); |
6abb4bd5 | 480 | mutex_unlock(&rcu_gp_lock); |
5bffdd5d MD |
481 | |
482 | /* | |
483 | * Wakeup waiters only after we have completed the grace period | |
484 | * and have ensured the memory barriers at the end of the grace | |
485 | * period have been issued. | |
486 | */ | |
487 | urcu_wake_all_waiters(&waiters); | |
2bc59bd7 PM |
488 | } |
489 | ||
121a5d44 MD |
490 | /* |
491 | * library wrappers to be used by non-LGPL compatible source code. | |
492 | */ | |
493 | ||
494 | void rcu_read_lock(void) | |
495 | { | |
496 | _rcu_read_lock(); | |
497 | } | |
498 | ||
499 | void rcu_read_unlock(void) | |
500 | { | |
501 | _rcu_read_unlock(); | |
502 | } | |
503 | ||
882f3357 MD |
504 | int rcu_read_ongoing(void) |
505 | { | |
506 | return _rcu_read_ongoing(); | |
507 | } | |
508 | ||
121a5d44 | 509 | void rcu_register_thread(void) |
27b012e2 | 510 | { |
bd252a04 MD |
511 | URCU_TLS(rcu_reader).tid = pthread_self(); |
512 | assert(URCU_TLS(rcu_reader).need_mb == 0); | |
513 | assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK)); | |
02be5561 | 514 | |
3c29ca5d | 515 | mutex_lock(&rcu_registry_lock); |
02be5561 | 516 | rcu_init(); /* In case gcc does not support constructor attribute */ |
bd252a04 | 517 | cds_list_add(&URCU_TLS(rcu_reader).node, ®istry); |
3c29ca5d | 518 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
519 | } |
520 | ||
121a5d44 | 521 | void rcu_unregister_thread(void) |
27b012e2 | 522 | { |
3c29ca5d | 523 | mutex_lock(&rcu_registry_lock); |
bd252a04 | 524 | cds_list_del(&URCU_TLS(rcu_reader).node); |
3c29ca5d | 525 | mutex_unlock(&rcu_registry_lock); |
27b012e2 MD |
526 | } |
527 | ||
fdf01eed MD |
528 | #ifdef RCU_MEMBARRIER |
529 | void rcu_init(void) | |
530 | { | |
531 | if (init_done) | |
532 | return; | |
533 | init_done = 1; | |
cf5271ee | 534 | if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY)) |
1de4df4b | 535 | rcu_has_sys_membarrier = 1; |
fdf01eed MD |
536 | } |
537 | #endif | |
538 | ||
539 | #ifdef RCU_SIGNAL | |
02be5561 | 540 | static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context) |
27b012e2 | 541 | { |
40e140c9 | 542 | /* |
5481ddb3 DG |
543 | * Executing this cmm_smp_mb() is the only purpose of this signal handler. |
544 | * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is | |
40e140c9 MD |
545 | * executed on. |
546 | */ | |
5481ddb3 | 547 | cmm_smp_mb(); |
bd252a04 | 548 | _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0); |
5481ddb3 | 549 | cmm_smp_mb(); |
27b012e2 MD |
550 | } |
551 | ||
8a5fb4c9 | 552 | /* |
02be5561 | 553 | * rcu_init constructor. Called when the library is linked, but also when |
8a5fb4c9 MD |
554 | * reader threads are calling rcu_register_thread(). |
555 | * Should only be called by a single thread at a given time. This is ensured by | |
3c29ca5d MD |
556 | * holing the rcu_registry_lock from rcu_register_thread() or by running |
557 | * at library load time, which should not be executed by multiple | |
558 | * threads nor concurrently with rcu_register_thread() anyway. | |
8a5fb4c9 | 559 | */ |
02be5561 | 560 | void rcu_init(void) |
27b012e2 MD |
561 | { |
562 | struct sigaction act; | |
563 | int ret; | |
564 | ||
8a5fb4c9 MD |
565 | if (init_done) |
566 | return; | |
567 | init_done = 1; | |
568 | ||
02be5561 | 569 | act.sa_sigaction = sigrcu_handler; |
dd052bd3 | 570 | act.sa_flags = SA_SIGINFO | SA_RESTART; |
c297c21c | 571 | sigemptyset(&act.sa_mask); |
02be5561 | 572 | ret = sigaction(SIGRCU, &act, NULL); |
4a6d7378 MD |
573 | if (ret) |
574 | urcu_die(errno); | |
27b012e2 MD |
575 | } |
576 | ||
02be5561 | 577 | void rcu_exit(void) |
27b012e2 | 578 | { |
71210954 MD |
579 | /* |
580 | * Don't unregister the SIGRCU signal handler anymore, because | |
581 | * call_rcu threads could still be using it shortly before the | |
582 | * application exits. | |
583 | * Assertion disabled because call_rcu threads are now rcu | |
584 | * readers, and left running at exit. | |
585 | * assert(cds_list_empty(®istry)); | |
586 | */ | |
27b012e2 | 587 | } |
5e77fc1f | 588 | |
fdf01eed | 589 | #endif /* #ifdef RCU_SIGNAL */ |
5e77fc1f | 590 | |
5e6b23a6 | 591 | DEFINE_RCU_FLAVOR(rcu_flavor); |
541d828d | 592 | |
5e77fc1f | 593 | #include "urcu-call-rcu-impl.h" |
0376e7b2 | 594 | #include "urcu-defer-impl.h" |