Fix: tests: invoke destroy APIs for queues/stacks
[urcu.git] / urcu.c
CommitLineData
b257a10b
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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 *
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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
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22 *
23 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
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24 */
25
fdf01eed 26#define _BSD_SOURCE
c1d2c60b 27#define _GNU_SOURCE
71c811bf 28#define _LGPL_SOURCE
82d50e1a 29#define _DEFAULT_SOURCE
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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
999991c6 40#include "urcu/arch.h"
d73fb81f 41#include "urcu/wfcqueue.h"
57760d44 42#include "urcu/map/urcu.h"
af7c2dbe 43#include "urcu/static/urcu.h"
618b2595 44#include "urcu-pointer.h"
bd252a04 45#include "urcu/tls-compat.h"
71c811bf 46
4a6d7378 47#include "urcu-die.h"
5bffdd5d 48#include "urcu-wait.h"
4a6d7378 49
121a5d44 50/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
71c811bf 51#undef _LGPL_SOURCE
27b012e2 52#include "urcu.h"
71c811bf 53#define _LGPL_SOURCE
27b012e2 54
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55/*
56 * If a reader is really non-cooperative and refuses to commit its
57 * rcu_active_readers count to memory (there is no barrier in the reader
9340c38d 58 * per-se), kick it after 10 loops waiting for it.
3a71751e 59 */
9340c38d 60#define KICK_READER_LOOPS 10
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61
62/*
63 * Active attempts to check for reader Q.S. before calling futex().
64 */
65#define RCU_QS_ACTIVE_ATTEMPTS 100
66
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67/* If the headers do not support membarrier system call, fall back on RCU_MB */
68#ifdef __NR_membarrier
69# define membarrier(...) syscall(__NR_membarrier, __VA_ARGS__)
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70#else
71# define membarrier(...) -ENOSYS
72#endif
73
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74enum membarrier_cmd {
75 MEMBARRIER_CMD_QUERY = 0,
76 MEMBARRIER_CMD_SHARED = (1 << 0),
77};
553b7eb9 78
fdf01eed 79#ifdef RCU_MEMBARRIER
834a45ba 80static int init_done;
1de4df4b 81int rcu_has_sys_membarrier;
834a45ba 82
02be5561 83void __attribute__((constructor)) rcu_init(void);
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84#endif
85
86#ifdef RCU_MB
02be5561 87void rcu_init(void)
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88{
89}
90#endif
8a5fb4c9 91
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92#ifdef RCU_SIGNAL
93static int init_done;
94
95void __attribute__((constructor)) rcu_init(void);
96void __attribute__((destructor)) rcu_exit(void);
97#endif
98
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99/*
100 * rcu_gp_lock ensures mutual exclusion between threads calling
101 * synchronize_rcu().
102 */
6abb4bd5 103static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
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104/*
105 * rcu_registry_lock ensures mutual exclusion between threads
106 * registering and unregistering themselves to/from the registry, and
107 * with threads reading that registry from synchronize_rcu(). However,
108 * this lock is not held all the way through the completion of awaiting
109 * for the grace period. It is sporadically released between iterations
110 * on the registry.
111 * rcu_registry_lock may nest inside rcu_gp_lock.
112 */
113static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER;
4de0cd31 114struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT };
27b012e2 115
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116/*
117 * Written to only by each individual reader. Read by both the reader and the
118 * writers.
119 */
bd252a04 120DEFINE_URCU_TLS(struct rcu_reader, rcu_reader);
27b012e2 121
16aa9ee8 122static CDS_LIST_HEAD(registry);
27b012e2 123
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124/*
125 * Queue keeping threads awaiting to wait for a grace period. Contains
126 * struct gp_waiters_thread objects.
127 */
128static DEFINE_URCU_WAIT_QUEUE(gp_waiters);
129
6abb4bd5 130static void mutex_lock(pthread_mutex_t *mutex)
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131{
132 int ret;
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133
134#ifndef DISTRUST_SIGNALS_EXTREME
6abb4bd5 135 ret = pthread_mutex_lock(mutex);
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136 if (ret)
137 urcu_die(ret);
09a9f986 138#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
6abb4bd5 139 while ((ret = pthread_mutex_trylock(mutex)) != 0) {
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140 if (ret != EBUSY && ret != EINTR)
141 urcu_die(ret);
bd252a04 142 if (CMM_LOAD_SHARED(URCU_TLS(rcu_reader).need_mb)) {
5481ddb3 143 cmm_smp_mb();
bd252a04 144 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
5481ddb3 145 cmm_smp_mb();
09a9f986 146 }
8999a9ee 147 (void) poll(NULL, 0, 10);
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148 }
149#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
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150}
151
6abb4bd5 152static void mutex_unlock(pthread_mutex_t *mutex)
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153{
154 int ret;
155
6abb4bd5 156 ret = pthread_mutex_unlock(mutex);
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157 if (ret)
158 urcu_die(ret);
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159}
160
fdf01eed 161#ifdef RCU_MEMBARRIER
a4922ed9 162static void smp_mb_master(void)
fdf01eed 163{
1de4df4b 164 if (caa_likely(rcu_has_sys_membarrier))
64f469e6 165 (void) membarrier(MEMBARRIER_CMD_SHARED, 0);
fdf01eed 166 else
5481ddb3 167 cmm_smp_mb();
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168}
169#endif
170
02be5561 171#ifdef RCU_MB
a4922ed9 172static void smp_mb_master(void)
40e140c9 173{
5481ddb3 174 cmm_smp_mb();
40e140c9 175}
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176#endif
177
178#ifdef RCU_SIGNAL
78ff9419 179static void force_mb_all_readers(void)
27b012e2 180{
02be5561 181 struct rcu_reader *index;
e3b0cef0 182
27b012e2 183 /*
5481ddb3 184 * Ask for each threads to execute a cmm_smp_mb() so we can consider the
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185 * compiler barriers around rcu read lock as real memory barriers.
186 */
16aa9ee8 187 if (cds_list_empty(&registry))
27b012e2 188 return;
3a86deba 189 /*
5481ddb3 190 * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs
157dca95 191 * a cache flush on architectures with non-coherent cache. Let's play
5481ddb3 192 * safe and don't assume anything : we use cmm_smp_mc() to make sure the
157dca95 193 * cache flush is enforced.
3a86deba 194 */
16aa9ee8 195 cds_list_for_each_entry(index, &registry, node) {
6cf3827c 196 CMM_STORE_SHARED(index->need_mb, 1);
02be5561 197 pthread_kill(index->tid, SIGRCU);
09a9f986 198 }
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199 /*
200 * Wait for sighandler (and thus mb()) to execute on every thread.
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201 *
202 * Note that the pthread_kill() will never be executed on systems
203 * that correctly deliver signals in a timely manner. However, it
204 * is not uncommon for kernels to have bugs that can result in
205 * lost or unduly delayed signals.
206 *
207 * If you are seeing the below pthread_kill() executing much at
208 * all, we suggest testing the underlying kernel and filing the
209 * relevant bug report. For Linux kernels, we recommend getting
210 * the Linux Test Project (LTP).
27b012e2 211 */
16aa9ee8 212 cds_list_for_each_entry(index, &registry, node) {
6cf3827c 213 while (CMM_LOAD_SHARED(index->need_mb)) {
02be5561 214 pthread_kill(index->tid, SIGRCU);
8999a9ee 215 (void) poll(NULL, 0, 1);
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216 }
217 }
5481ddb3 218 cmm_smp_mb(); /* read ->need_mb before ending the barrier */
27b012e2 219}
9d7e3f89 220
a4922ed9 221static void smp_mb_master(void)
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222{
223 force_mb_all_readers();
224}
fdf01eed 225#endif /* #ifdef RCU_SIGNAL */
27b012e2 226
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227/*
228 * synchronize_rcu() waiting. Single thread.
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229 * Always called with rcu_registry lock held. Releases this lock and
230 * grabs it again. Holds the lock when it returns.
bc6c15bb 231 */
cfe78e25 232static void wait_gp(void)
bc6c15bb 233{
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234 /*
235 * Read reader_gp before read futex. smp_mb_master() needs to
236 * be called with the rcu registry lock held in RCU_SIGNAL
237 * flavor.
238 */
a4922ed9 239 smp_mb_master();
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240 /* Temporarily unlock the registry lock. */
241 mutex_unlock(&rcu_registry_lock);
b0a841b4 242 if (uatomic_read(&rcu_gp.futex) != -1)
fca9fb96 243 goto end;
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244 while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1,
245 NULL, NULL, 0)) {
246 switch (errno) {
247 case EWOULDBLOCK:
248 /* Value already changed. */
fca9fb96 249 goto end;
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250 case EINTR:
251 /* Retry if interrupted by signal. */
252 break; /* Get out of switch. */
253 default:
254 /* Unexpected error. */
255 urcu_die(errno);
256 }
257 }
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258end:
259 /*
260 * Re-lock the registry lock before the next loop.
261 */
262 mutex_lock(&rcu_registry_lock);
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263}
264
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265/*
266 * Always called with rcu_registry lock held. Releases this lock between
267 * iterations and grabs it again. Holds the lock when it returns.
268 */
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269static void wait_for_readers(struct cds_list_head *input_readers,
270 struct cds_list_head *cur_snap_readers,
271 struct cds_list_head *qsreaders)
27b012e2 272{
9340c38d 273 unsigned int wait_loops = 0;
02be5561 274 struct rcu_reader *index, *tmp;
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275#ifdef HAS_INCOHERENT_CACHES
276 unsigned int wait_gp_loops = 0;
277#endif /* HAS_INCOHERENT_CACHES */
27b012e2 278
40e140c9 279 /*
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280 * Wait for each thread URCU_TLS(rcu_reader).ctr to either
281 * indicate quiescence (not nested), or observe the current
ed1b099e 282 * rcu_gp.ctr value.
27b012e2 283 */
cfe78e25 284 for (;;) {
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285 if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS)
286 wait_loops++;
9340c38d 287 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
ed1b099e 288 uatomic_dec(&rcu_gp.futex);
cfe78e25 289 /* Write futex before read reader_gp */
a4922ed9 290 smp_mb_master();
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291 }
292
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293 cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
294 switch (rcu_reader_state(&index->ctr)) {
295 case RCU_READER_ACTIVE_CURRENT:
296 if (cur_snap_readers) {
297 cds_list_move(&index->node,
298 cur_snap_readers);
299 break;
300 }
301 /* Fall-through */
302 case RCU_READER_INACTIVE:
303 cds_list_move(&index->node, qsreaders);
304 break;
305 case RCU_READER_ACTIVE_OLD:
306 /*
307 * Old snapshot. Leaving node in
308 * input_readers will make us busy-loop
309 * until the snapshot becomes current or
310 * the reader becomes inactive.
311 */
312 break;
313 }
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314 }
315
e8043c1b 316#ifndef HAS_INCOHERENT_CACHES
fd189fa5 317 if (cds_list_empty(input_readers)) {
9340c38d 318 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
cfe78e25 319 /* Read reader_gp before write futex */
a4922ed9 320 smp_mb_master();
ed1b099e 321 uatomic_set(&rcu_gp.futex, 0);
bc6c15bb 322 }
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323 break;
324 } else {
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325 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
326 /* wait_gp unlocks/locks registry lock. */
cfe78e25 327 wait_gp();
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328 } else {
329 /* Temporarily unlock the registry lock. */
330 mutex_unlock(&rcu_registry_lock);
06f22bdb 331 caa_cpu_relax();
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332 /*
333 * Re-lock the registry lock before the
334 * next loop.
335 */
336 mutex_lock(&rcu_registry_lock);
337 }
bc6c15bb 338 }
e8043c1b 339#else /* #ifndef HAS_INCOHERENT_CACHES */
27b012e2 340 /*
40e140c9 341 * BUSY-LOOP. Force the reader thread to commit its
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342 * URCU_TLS(rcu_reader).ctr update to memory if we wait
343 * for too long.
27b012e2 344 */
fd189fa5 345 if (cds_list_empty(input_readers)) {
9340c38d 346 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
cfe78e25 347 /* Read reader_gp before write futex */
a4922ed9 348 smp_mb_master();
ed1b099e 349 uatomic_set(&rcu_gp.futex, 0);
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350 }
351 break;
352 } else {
9340c38d 353 if (wait_gp_loops == KICK_READER_LOOPS) {
a4922ed9 354 smp_mb_master();
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355 wait_gp_loops = 0;
356 }
357 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
fca9fb96 358 /* wait_gp unlocks/locks registry lock. */
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359 wait_gp();
360 wait_gp_loops++;
361 } else {
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362 /* Temporarily unlock the registry lock. */
363 mutex_unlock(&rcu_registry_lock);
06f22bdb 364 caa_cpu_relax();
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365 /*
366 * Re-lock the registry lock before the
367 * next loop.
368 */
369 mutex_lock(&rcu_registry_lock);
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370 }
371 }
e8043c1b 372#endif /* #else #ifndef HAS_INCOHERENT_CACHES */
27b012e2 373 }
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374}
375
9598a481 376void synchronize_rcu(void)
2bc59bd7 377{
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378 CDS_LIST_HEAD(cur_snap_readers);
379 CDS_LIST_HEAD(qsreaders);
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380 DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING);
381 struct urcu_waiters waiters;
382
383 /*
384 * Add ourself to gp_waiters queue of threads awaiting to wait
385 * for a grace period. Proceed to perform the grace period only
386 * if we are the first thread added into the queue.
387 * The implicit memory barrier before urcu_wait_add()
388 * orders prior memory accesses of threads put into the wait
389 * queue before their insertion into the wait queue.
390 */
391 if (urcu_wait_add(&gp_waiters, &wait) != 0) {
392 /* Not first in queue: will be awakened by another thread. */
393 urcu_adaptative_busy_wait(&wait);
394 /* Order following memory accesses after grace period. */
395 cmm_smp_mb();
396 return;
397 }
398 /* We won't need to wake ourself up */
399 urcu_wait_set_state(&wait, URCU_WAIT_RUNNING);
fd189fa5 400
6abb4bd5 401 mutex_lock(&rcu_gp_lock);
135530fd 402
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403 /*
404 * Move all waiters into our local queue.
405 */
406 urcu_move_waiters(&waiters, &gp_waiters);
407
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408 mutex_lock(&rcu_registry_lock);
409
16aa9ee8 410 if (cds_list_empty(&registry))
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411 goto out;
412
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413 /*
414 * All threads should read qparity before accessing data structure
415 * where new ptr points to. Must be done within rcu_registry_lock
416 * because it iterates on reader threads.
417 */
9598a481 418 /* Write new ptr before changing the qparity */
a4922ed9 419 smp_mb_master();
9598a481 420
9598a481 421 /*
c9488684 422 * Wait for readers to observe original parity or be quiescent.
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423 * wait_for_readers() can release and grab again rcu_registry_lock
424 * interally.
9598a481 425 */
fd189fa5 426 wait_for_readers(&registry, &cur_snap_readers, &qsreaders);
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427
428 /*
c9488684 429 * Must finish waiting for quiescent state for original parity before
ed1b099e 430 * committing next rcu_gp.ctr update to memory. Failure to do so could
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431 * result in the writer waiting forever while new readers are always
432 * accessing data (no progress). Enforce compiler-order of load
ed1b099e 433 * URCU_TLS(rcu_reader).ctr before store to rcu_gp.ctr.
9598a481 434 */
5481ddb3 435 cmm_barrier();
9598a481 436
5dba80f9 437 /*
5481ddb3 438 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
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439 * model easier to understand. It does not have a big performance impact
440 * anyway, given this is the write-side.
441 */
5481ddb3 442 cmm_smp_mb();
67c2d80b 443
c9488684 444 /* Switch parity: 0 -> 1, 1 -> 0 */
ed1b099e 445 CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR_PHASE);
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446
447 /*
ed1b099e 448 * Must commit rcu_gp.ctr update to memory before waiting for quiescent
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449 * state. Failure to do so could result in the writer waiting forever
450 * while new readers are always accessing data (no progress). Enforce
ed1b099e 451 * compiler-order of store to rcu_gp.ctr before load rcu_reader ctr.
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452 */
453 cmm_barrier();
454
455 /*
456 *
457 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
458 * model easier to understand. It does not have a big performance impact
459 * anyway, given this is the write-side.
460 */
461 cmm_smp_mb();
462
9598a481 463 /*
c9488684 464 * Wait for readers to observe new parity or be quiescent.
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465 * wait_for_readers() can release and grab again rcu_registry_lock
466 * interally.
9598a481 467 */
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468 wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
469
470 /*
471 * Put quiescent reader list back into registry.
472 */
473 cds_list_splice(&qsreaders, &registry);
9598a481 474
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475 /*
476 * Finish waiting for reader threads before letting the old ptr
477 * being freed. Must be done within rcu_registry_lock because it
478 * iterates on reader threads.
479 */
a4922ed9 480 smp_mb_master();
2dfb8b5e 481out:
731ccb96 482 mutex_unlock(&rcu_registry_lock);
6abb4bd5 483 mutex_unlock(&rcu_gp_lock);
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484
485 /*
486 * Wakeup waiters only after we have completed the grace period
487 * and have ensured the memory barriers at the end of the grace
488 * period have been issued.
489 */
490 urcu_wake_all_waiters(&waiters);
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491}
492
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493/*
494 * library wrappers to be used by non-LGPL compatible source code.
495 */
496
497void rcu_read_lock(void)
498{
499 _rcu_read_lock();
500}
501
502void rcu_read_unlock(void)
503{
504 _rcu_read_unlock();
505}
506
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507int rcu_read_ongoing(void)
508{
509 return _rcu_read_ongoing();
510}
511
121a5d44 512void rcu_register_thread(void)
27b012e2 513{
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514 URCU_TLS(rcu_reader).tid = pthread_self();
515 assert(URCU_TLS(rcu_reader).need_mb == 0);
516 assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK));
02be5561 517
731ccb96 518 mutex_lock(&rcu_registry_lock);
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519 assert(!URCU_TLS(rcu_reader).registered);
520 URCU_TLS(rcu_reader).registered = 1;
02be5561 521 rcu_init(); /* In case gcc does not support constructor attribute */
bd252a04 522 cds_list_add(&URCU_TLS(rcu_reader).node, &registry);
731ccb96 523 mutex_unlock(&rcu_registry_lock);
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524}
525
121a5d44 526void rcu_unregister_thread(void)
27b012e2 527{
731ccb96 528 mutex_lock(&rcu_registry_lock);
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529 assert(URCU_TLS(rcu_reader).registered);
530 URCU_TLS(rcu_reader).registered = 0;
bd252a04 531 cds_list_del(&URCU_TLS(rcu_reader).node);
731ccb96 532 mutex_unlock(&rcu_registry_lock);
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533}
534
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535#ifdef RCU_MEMBARRIER
536void rcu_init(void)
537{
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538 int ret;
539
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540 if (init_done)
541 return;
542 init_done = 1;
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543 ret = membarrier(MEMBARRIER_CMD_QUERY, 0);
544 if (ret >= 0 && (ret & MEMBARRIER_CMD_SHARED)) {
1de4df4b 545 rcu_has_sys_membarrier = 1;
64f469e6 546 }
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547}
548#endif
549
550#ifdef RCU_SIGNAL
02be5561 551static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context)
27b012e2 552{
40e140c9 553 /*
5481ddb3
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554 * Executing this cmm_smp_mb() is the only purpose of this signal handler.
555 * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is
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556 * executed on.
557 */
5481ddb3 558 cmm_smp_mb();
bd252a04 559 _CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
5481ddb3 560 cmm_smp_mb();
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561}
562
8a5fb4c9 563/*
02be5561 564 * rcu_init constructor. Called when the library is linked, but also when
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565 * reader threads are calling rcu_register_thread().
566 * Should only be called by a single thread at a given time. This is ensured by
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567 * holing the rcu_registry_lock from rcu_register_thread() or by running
568 * at library load time, which should not be executed by multiple
569 * threads nor concurrently with rcu_register_thread() anyway.
8a5fb4c9 570 */
02be5561 571void rcu_init(void)
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572{
573 struct sigaction act;
574 int ret;
575
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576 if (init_done)
577 return;
578 init_done = 1;
579
02be5561 580 act.sa_sigaction = sigrcu_handler;
dd052bd3 581 act.sa_flags = SA_SIGINFO | SA_RESTART;
c297c21c 582 sigemptyset(&act.sa_mask);
02be5561 583 ret = sigaction(SIGRCU, &act, NULL);
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584 if (ret)
585 urcu_die(errno);
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586}
587
02be5561 588void rcu_exit(void)
27b012e2 589{
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590 /*
591 * Don't unregister the SIGRCU signal handler anymore, because
592 * call_rcu threads could still be using it shortly before the
593 * application exits.
594 * Assertion disabled because call_rcu threads are now rcu
595 * readers, and left running at exit.
596 * assert(cds_list_empty(&registry));
597 */
27b012e2 598}
5e77fc1f 599
fdf01eed 600#endif /* #ifdef RCU_SIGNAL */
5e77fc1f 601
5e6b23a6 602DEFINE_RCU_FLAVOR(rcu_flavor);
541d828d 603
5e77fc1f 604#include "urcu-call-rcu-impl.h"
0376e7b2 605#include "urcu-defer-impl.h"
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