Android: do not redefine gettid on Android
[urcu.git] / urcu.c
CommitLineData
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
27b012e2
MD
29#include <stdio.h>
30#include <pthread.h>
31#include <signal.h>
32#include <assert.h>
f69f195a 33#include <stdlib.h>
6d841bc2 34#include <stdint.h>
f69f195a 35#include <string.h>
09a9f986 36#include <errno.h>
e8043c1b 37#include <poll.h>
27b012e2 38
d73fb81f 39#include "urcu/wfcqueue.h"
57760d44 40#include "urcu/map/urcu.h"
af7c2dbe 41#include "urcu/static/urcu.h"
618b2595 42#include "urcu-pointer.h"
bd252a04 43#include "urcu/tls-compat.h"
71c811bf 44
4a6d7378 45#include "urcu-die.h"
5bffdd5d 46#include "urcu-wait.h"
4a6d7378 47
121a5d44 48/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
71c811bf 49#undef _LGPL_SOURCE
27b012e2 50#include "urcu.h"
71c811bf 51#define _LGPL_SOURCE
27b012e2 52
3a71751e
PB
53/*
54 * If a reader is really non-cooperative and refuses to commit its
55 * rcu_active_readers count to memory (there is no barrier in the reader
56 * per-se), kick it after a few loops waiting for it.
57 */
58#define KICK_READER_LOOPS 10000
59
60/*
61 * Active attempts to check for reader Q.S. before calling futex().
62 */
63#define RCU_QS_ACTIVE_ATTEMPTS 100
64
553b7eb9
MD
65/*
66 * RCU_MEMBARRIER is only possibly available on Linux.
67 */
68#if defined(RCU_MEMBARRIER) && defined(__linux__)
9ba261bd 69#include <urcu/syscall-compat.h>
553b7eb9
MD
70#endif
71
72/* If the headers do not support SYS_membarrier, fall back on RCU_MB */
73#ifdef SYS_membarrier
74# define membarrier(...) syscall(SYS_membarrier, __VA_ARGS__)
75#else
76# define membarrier(...) -ENOSYS
77#endif
78
79#define MEMBARRIER_EXPEDITED (1 << 0)
80#define MEMBARRIER_DELAYED (1 << 1)
81#define MEMBARRIER_QUERY (1 << 16)
82
fdf01eed 83#ifdef RCU_MEMBARRIER
834a45ba 84static int init_done;
1de4df4b 85int rcu_has_sys_membarrier;
834a45ba 86
02be5561 87void __attribute__((constructor)) rcu_init(void);
fdf01eed
MD
88#endif
89
90#ifdef RCU_MB
02be5561 91void rcu_init(void)
e90a6e9c
MD
92{
93}
94#endif
8a5fb4c9 95
fdf01eed
MD
96#ifdef RCU_SIGNAL
97static int init_done;
98
99void __attribute__((constructor)) rcu_init(void);
100void __attribute__((destructor)) rcu_exit(void);
101#endif
102
6abb4bd5 103static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
4de0cd31 104struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT };
27b012e2 105
b0d5e790
MD
106/*
107 * Written to only by each individual reader. Read by both the reader and the
108 * writers.
109 */
bd252a04 110DEFINE_URCU_TLS(struct rcu_reader, rcu_reader);
27b012e2 111
cf380c2f 112#ifdef DEBUG_YIELD
1de4df4b
MD
113unsigned int rcu_yield_active;
114DEFINE_URCU_TLS(unsigned int, rcu_rand_yield);
cf380c2f
MD
115#endif
116
16aa9ee8 117static CDS_LIST_HEAD(registry);
27b012e2 118
5bffdd5d
MD
119/*
120 * Queue keeping threads awaiting to wait for a grace period. Contains
121 * struct gp_waiters_thread objects.
122 */
123static DEFINE_URCU_WAIT_QUEUE(gp_waiters);
124
6abb4bd5 125static void mutex_lock(pthread_mutex_t *mutex)
41718ff9
MD
126{
127 int ret;
09a9f986
PM
128
129#ifndef DISTRUST_SIGNALS_EXTREME
6abb4bd5 130 ret = pthread_mutex_lock(mutex);
4a6d7378
MD
131 if (ret)
132 urcu_die(ret);
09a9f986 133#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
6abb4bd5 134 while ((ret = pthread_mutex_trylock(mutex)) != 0) {
4a6d7378
MD
135 if (ret != EBUSY && ret != EINTR)
136 urcu_die(ret);
bd252a04 137 if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) {
5481ddb3 138 cmm_smp_mb();
bd252a04 139 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
5481ddb3 140 cmm_smp_mb();
09a9f986
PM
141 }
142 poll(NULL,0,10);
143 }
144#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
41718ff9
MD
145}
146
6abb4bd5 147static void mutex_unlock(pthread_mutex_t *mutex)
41718ff9
MD
148{
149 int ret;
150
6abb4bd5 151 ret = pthread_mutex_unlock(mutex);
4a6d7378
MD
152 if (ret)
153 urcu_die(ret);
41718ff9
MD
154}
155
fdf01eed 156#ifdef RCU_MEMBARRIER
25cc6d18 157static void smp_mb_master(int group)
fdf01eed 158{
1de4df4b 159 if (caa_likely(rcu_has_sys_membarrier))
553b7eb9 160 (void) membarrier(MEMBARRIER_EXPEDITED);
fdf01eed 161 else
5481ddb3 162 cmm_smp_mb();
fdf01eed
MD
163}
164#endif
165
02be5561 166#ifdef RCU_MB
25cc6d18 167static void smp_mb_master(int group)
40e140c9 168{
5481ddb3 169 cmm_smp_mb();
40e140c9 170}
fdf01eed
MD
171#endif
172
173#ifdef RCU_SIGNAL
78ff9419 174static void force_mb_all_readers(void)
27b012e2 175{
02be5561 176 struct rcu_reader *index;
e3b0cef0 177
27b012e2 178 /*
5481ddb3 179 * Ask for each threads to execute a cmm_smp_mb() so we can consider the
27b012e2
MD
180 * compiler barriers around rcu read lock as real memory barriers.
181 */
16aa9ee8 182 if (cds_list_empty(&registry))
27b012e2 183 return;
3a86deba 184 /*
5481ddb3 185 * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs
157dca95 186 * a cache flush on architectures with non-coherent cache. Let's play
5481ddb3 187 * safe and don't assume anything : we use cmm_smp_mc() to make sure the
157dca95 188 * cache flush is enforced.
3a86deba 189 */
16aa9ee8 190 cds_list_for_each_entry(index, &registry, node) {
6cf3827c 191 CMM_STORE_SHARED(index->need_mb, 1);
02be5561 192 pthread_kill(index->tid, SIGRCU);
09a9f986 193 }
27b012e2
MD
194 /*
195 * Wait for sighandler (and thus mb()) to execute on every thread.
09a9f986
PM
196 *
197 * Note that the pthread_kill() will never be executed on systems
198 * that correctly deliver signals in a timely manner. However, it
199 * is not uncommon for kernels to have bugs that can result in
200 * lost or unduly delayed signals.
201 *
202 * If you are seeing the below pthread_kill() executing much at
203 * all, we suggest testing the underlying kernel and filing the
204 * relevant bug report. For Linux kernels, we recommend getting
205 * the Linux Test Project (LTP).
27b012e2 206 */
16aa9ee8 207 cds_list_for_each_entry(index, &registry, node) {
6cf3827c 208 while (CMM_LOAD_SHARED(index->need_mb)) {
02be5561 209 pthread_kill(index->tid, SIGRCU);
09a9f986
PM
210 poll(NULL, 0, 1);
211 }
212 }
5481ddb3 213 cmm_smp_mb(); /* read ->need_mb before ending the barrier */
27b012e2 214}
9d7e3f89 215
25cc6d18 216static void smp_mb_master(int group)
9d7e3f89
MD
217{
218 force_mb_all_readers();
219}
fdf01eed 220#endif /* #ifdef RCU_SIGNAL */
27b012e2 221
bc6c15bb
MD
222/*
223 * synchronize_rcu() waiting. Single thread.
224 */
cfe78e25 225static void wait_gp(void)
bc6c15bb 226{
cfe78e25 227 /* Read reader_gp before read futex */
25cc6d18 228 smp_mb_master(RCU_MB_GROUP);
ed1b099e
LJ
229 if (uatomic_read(&rcu_gp.futex) == -1)
230 futex_async(&rcu_gp.futex, FUTEX_WAIT, -1,
cfe78e25 231 NULL, NULL, 0);
bc6c15bb
MD
232}
233
fd189fa5
MD
234static void wait_for_readers(struct cds_list_head *input_readers,
235 struct cds_list_head *cur_snap_readers,
236 struct cds_list_head *qsreaders)
27b012e2 237{
cfe78e25 238 int wait_loops = 0;
02be5561 239 struct rcu_reader *index, *tmp;
27b012e2 240
40e140c9 241 /*
c9488684
MD
242 * Wait for each thread URCU_TLS(rcu_reader).ctr to either
243 * indicate quiescence (not nested), or observe the current
ed1b099e 244 * rcu_gp.ctr value.
27b012e2 245 */
cfe78e25
MD
246 for (;;) {
247 wait_loops++;
248 if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
ed1b099e 249 uatomic_dec(&rcu_gp.futex);
cfe78e25 250 /* Write futex before read reader_gp */
25cc6d18 251 smp_mb_master(RCU_MB_GROUP);
cfe78e25
MD
252 }
253
fd189fa5
MD
254 cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
255 switch (rcu_reader_state(&index->ctr)) {
256 case RCU_READER_ACTIVE_CURRENT:
257 if (cur_snap_readers) {
258 cds_list_move(&index->node,
259 cur_snap_readers);
260 break;
261 }
262 /* Fall-through */
263 case RCU_READER_INACTIVE:
264 cds_list_move(&index->node, qsreaders);
265 break;
266 case RCU_READER_ACTIVE_OLD:
267 /*
268 * Old snapshot. Leaving node in
269 * input_readers will make us busy-loop
270 * until the snapshot becomes current or
271 * the reader becomes inactive.
272 */
273 break;
274 }
cfe78e25
MD
275 }
276
e8043c1b 277#ifndef HAS_INCOHERENT_CACHES
fd189fa5 278 if (cds_list_empty(input_readers)) {
cfe78e25
MD
279 if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
280 /* Read reader_gp before write futex */
25cc6d18 281 smp_mb_master(RCU_MB_GROUP);
ed1b099e 282 uatomic_set(&rcu_gp.futex, 0);
bc6c15bb 283 }
cfe78e25
MD
284 break;
285 } else {
286 if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
287 wait_gp();
288 else
06f22bdb 289 caa_cpu_relax();
bc6c15bb 290 }
e8043c1b 291#else /* #ifndef HAS_INCOHERENT_CACHES */
27b012e2 292 /*
40e140c9 293 * BUSY-LOOP. Force the reader thread to commit its
bd252a04
MD
294 * URCU_TLS(rcu_reader).ctr update to memory if we wait
295 * for too long.
27b012e2 296 */
fd189fa5 297 if (cds_list_empty(input_readers)) {
cfe78e25
MD
298 if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
299 /* Read reader_gp before write futex */
25cc6d18 300 smp_mb_master(RCU_MB_GROUP);
ed1b099e 301 uatomic_set(&rcu_gp.futex, 0);
cfe78e25
MD
302 }
303 break;
304 } else {
305 switch (wait_loops) {
bc6c15bb 306 case RCU_QS_ACTIVE_ATTEMPTS:
cfe78e25
MD
307 wait_gp();
308 break; /* only escape switch */
bc6c15bb 309 case KICK_READER_LOOPS:
25cc6d18 310 smp_mb_master(RCU_MB_GROUP);
40e140c9 311 wait_loops = 0;
cfe78e25 312 break; /* only escape switch */
bc6c15bb 313 default:
06f22bdb 314 caa_cpu_relax();
40e140c9
MD
315 }
316 }
e8043c1b 317#endif /* #else #ifndef HAS_INCOHERENT_CACHES */
27b012e2 318 }
27b012e2
MD
319}
320
9598a481 321void synchronize_rcu(void)
2bc59bd7 322{
fd189fa5
MD
323 CDS_LIST_HEAD(cur_snap_readers);
324 CDS_LIST_HEAD(qsreaders);
5bffdd5d
MD
325 DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING);
326 struct urcu_waiters waiters;
327
328 /*
329 * Add ourself to gp_waiters queue of threads awaiting to wait
330 * for a grace period. Proceed to perform the grace period only
331 * if we are the first thread added into the queue.
332 * The implicit memory barrier before urcu_wait_add()
333 * orders prior memory accesses of threads put into the wait
334 * queue before their insertion into the wait queue.
335 */
336 if (urcu_wait_add(&gp_waiters, &wait) != 0) {
337 /* Not first in queue: will be awakened by another thread. */
338 urcu_adaptative_busy_wait(&wait);
339 /* Order following memory accesses after grace period. */
340 cmm_smp_mb();
341 return;
342 }
343 /* We won't need to wake ourself up */
344 urcu_wait_set_state(&wait, URCU_WAIT_RUNNING);
fd189fa5 345
6abb4bd5 346 mutex_lock(&rcu_gp_lock);
135530fd 347
5bffdd5d
MD
348 /*
349 * Move all waiters into our local queue.
350 */
351 urcu_move_waiters(&waiters, &gp_waiters);
352
16aa9ee8 353 if (cds_list_empty(&registry))
2dfb8b5e
MD
354 goto out;
355
9598a481 356 /* All threads should read qparity before accessing data structure
6abb4bd5
MD
357 * where new ptr points to. Must be done within rcu_gp_lock because it
358 * iterates on reader threads.*/
9598a481 359 /* Write new ptr before changing the qparity */
25cc6d18 360 smp_mb_master(RCU_MB_GROUP);
9598a481 361
9598a481 362 /*
c9488684 363 * Wait for readers to observe original parity or be quiescent.
9598a481 364 */
fd189fa5 365 wait_for_readers(&registry, &cur_snap_readers, &qsreaders);
9598a481
MD
366
367 /*
c9488684 368 * Must finish waiting for quiescent state for original parity before
ed1b099e 369 * committing next rcu_gp.ctr update to memory. Failure to do so could
d40fde2c
MD
370 * result in the writer waiting forever while new readers are always
371 * accessing data (no progress). Enforce compiler-order of load
ed1b099e 372 * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr.
9598a481 373 */
5481ddb3 374 cmm_barrier();
9598a481 375
5dba80f9 376 /*
5481ddb3 377 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
5dba80f9
MD
378 * model easier to understand. It does not have a big performance impact
379 * anyway, given this is the write-side.
380 */
5481ddb3 381 cmm_smp_mb();
67c2d80b 382
c9488684 383 /* Switch parity: 0 -> 1, 1 -> 0 */
ed1b099e 384 CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE);
c9488684
MD
385
386 /*
ed1b099e 387 * Must commit rcu_gp.ctr update to memory before waiting for quiescent
c9488684
MD
388 * state. Failure to do so could result in the writer waiting forever
389 * while new readers are always accessing data (no progress). Enforce
ed1b099e 390 * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr.
c9488684
MD
391 */
392 cmm_barrier();
393
394 /*
395 *
396 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
397 * model easier to understand. It does not have a big performance impact
398 * anyway, given this is the write-side.
399 */
400 cmm_smp_mb();
401
9598a481 402 /*
c9488684 403 * Wait for readers to observe new parity or be quiescent.
9598a481 404 */
fd189fa5
MD
405 wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
406
407 /*
408 * Put quiescent reader list back into registry.
409 */
410 cds_list_splice(&qsreaders, &registry);
9598a481 411
9598a481 412 /* Finish waiting for reader threads before letting the old ptr being
6abb4bd5
MD
413 * freed. Must be done within rcu_gp_lock because it iterates on reader
414 * threads. */
25cc6d18 415 smp_mb_master(RCU_MB_GROUP);
2dfb8b5e 416out:
6abb4bd5 417 mutex_unlock(&rcu_gp_lock);
5bffdd5d
MD
418
419 /*
420 * Wakeup waiters only after we have completed the grace period
421 * and have ensured the memory barriers at the end of the grace
422 * period have been issued.
423 */
424 urcu_wake_all_waiters(&waiters);
2bc59bd7
PM
425}
426
121a5d44
MD
427/*
428 * library wrappers to be used by non-LGPL compatible source code.
429 */
430
431void rcu_read_lock(void)
432{
433 _rcu_read_lock();
434}
435
436void rcu_read_unlock(void)
437{
438 _rcu_read_unlock();
439}
440
882f3357
MD
441int rcu_read_ongoing(void)
442{
443 return _rcu_read_ongoing();
444}
445
121a5d44 446void rcu_register_thread(void)
27b012e2 447{
bd252a04
MD
448 URCU_TLS(rcu_reader).tid = pthread_self();
449 assert(URCU_TLS(rcu_reader).need_mb == 0);
450 assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK));
02be5561 451
6abb4bd5 452 mutex_lock(&rcu_gp_lock);
02be5561 453 rcu_init(); /* In case gcc does not support constructor attribute */
bd252a04 454 cds_list_add(&URCU_TLS(rcu_reader).node, &registry);
6abb4bd5 455 mutex_unlock(&rcu_gp_lock);
27b012e2
MD
456}
457
121a5d44 458void rcu_unregister_thread(void)
27b012e2 459{
6abb4bd5 460 mutex_lock(&rcu_gp_lock);
bd252a04 461 cds_list_del(&URCU_TLS(rcu_reader).node);
6abb4bd5 462 mutex_unlock(&rcu_gp_lock);
27b012e2
MD
463}
464
fdf01eed
MD
465#ifdef RCU_MEMBARRIER
466void rcu_init(void)
467{
468 if (init_done)
469 return;
470 init_done = 1;
cf5271ee 471 if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY))
1de4df4b 472 rcu_has_sys_membarrier = 1;
fdf01eed
MD
473}
474#endif
475
476#ifdef RCU_SIGNAL
02be5561 477static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context)
27b012e2 478{
40e140c9 479 /*
5481ddb3
DG
480 * Executing this cmm_smp_mb() is the only purpose of this signal handler.
481 * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is
40e140c9
MD
482 * executed on.
483 */
5481ddb3 484 cmm_smp_mb();
bd252a04 485 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
5481ddb3 486 cmm_smp_mb();
27b012e2
MD
487}
488
8a5fb4c9 489/*
02be5561 490 * rcu_init constructor. Called when the library is linked, but also when
8a5fb4c9
MD
491 * reader threads are calling rcu_register_thread().
492 * Should only be called by a single thread at a given time. This is ensured by
6abb4bd5
MD
493 * holing the rcu_gp_lock from rcu_register_thread() or by running at library
494 * load time, which should not be executed by multiple threads nor concurrently
495 * with rcu_register_thread() anyway.
8a5fb4c9 496 */
02be5561 497void rcu_init(void)
27b012e2
MD
498{
499 struct sigaction act;
500 int ret;
501
8a5fb4c9
MD
502 if (init_done)
503 return;
504 init_done = 1;
505
02be5561 506 act.sa_sigaction = sigrcu_handler;
dd052bd3 507 act.sa_flags = SA_SIGINFO | SA_RESTART;
c297c21c 508 sigemptyset(&act.sa_mask);
02be5561 509 ret = sigaction(SIGRCU, &act, NULL);
4a6d7378
MD
510 if (ret)
511 urcu_die(errno);
27b012e2
MD
512}
513
02be5561 514void rcu_exit(void)
27b012e2 515{
71210954
MD
516 /*
517 * Don't unregister the SIGRCU signal handler anymore, because
518 * call_rcu threads could still be using it shortly before the
519 * application exits.
520 * Assertion disabled because call_rcu threads are now rcu
521 * readers, and left running at exit.
522 * assert(cds_list_empty(&registry));
523 */
27b012e2 524}
5e77fc1f 525
fdf01eed 526#endif /* #ifdef RCU_SIGNAL */
5e77fc1f 527
5e6b23a6 528DEFINE_RCU_FLAVOR(rcu_flavor);
541d828d 529
5e77fc1f 530#include "urcu-call-rcu-impl.h"
0376e7b2 531#include "urcu-defer-impl.h"
This page took 0.062322 seconds and 4 git commands to generate.