Fix: tests: invoke destroy APIs for queues/stacks
[urcu.git] / urcu-qsbr.c
1 /*
2 * urcu-qsbr.c
3 *
4 * Userspace RCU QSBR library
5 *
6 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
7 * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
8 *
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
22 *
23 * IBM's contributions to this file may be relicensed under LGPLv2 or later.
24 */
25
26 #define _GNU_SOURCE
27 #define _LGPL_SOURCE
28 #include <stdio.h>
29 #include <pthread.h>
30 #include <signal.h>
31 #include <assert.h>
32 #include <stdlib.h>
33 #include <stdint.h>
34 #include <string.h>
35 #include <errno.h>
36 #include <poll.h>
37
38 #include "urcu/wfcqueue.h"
39 #include "urcu/map/urcu-qsbr.h"
40 #define BUILD_QSBR_LIB
41 #include "urcu/static/urcu-qsbr.h"
42 #include "urcu-pointer.h"
43 #include "urcu/tls-compat.h"
44
45 #include "urcu-die.h"
46 #include "urcu-wait.h"
47
48 /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
49 #undef _LGPL_SOURCE
50 #include "urcu-qsbr.h"
51 #define _LGPL_SOURCE
52
53 void __attribute__((destructor)) rcu_exit(void);
54
55 /*
56 * rcu_gp_lock ensures mutual exclusion between threads calling
57 * synchronize_rcu().
58 */
59 static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
60 /*
61 * rcu_registry_lock ensures mutual exclusion between threads
62 * registering and unregistering themselves to/from the registry, and
63 * with threads reading that registry from synchronize_rcu(). However,
64 * this lock is not held all the way through the completion of awaiting
65 * for the grace period. It is sporadically released between iterations
66 * on the registry.
67 * rcu_registry_lock may nest inside rcu_gp_lock.
68 */
69 static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER;
70 struct rcu_gp rcu_gp = { .ctr = RCU_GP_ONLINE };
71
72 /*
73 * Active attempts to check for reader Q.S. before calling futex().
74 */
75 #define RCU_QS_ACTIVE_ATTEMPTS 100
76
77 /*
78 * Written to only by each individual reader. Read by both the reader and the
79 * writers.
80 */
81 DEFINE_URCU_TLS(struct rcu_reader, rcu_reader);
82
83 static CDS_LIST_HEAD(registry);
84
85 /*
86 * Queue keeping threads awaiting to wait for a grace period. Contains
87 * struct gp_waiters_thread objects.
88 */
89 static DEFINE_URCU_WAIT_QUEUE(gp_waiters);
90
91 static void mutex_lock(pthread_mutex_t *mutex)
92 {
93 int ret;
94
95 #ifndef DISTRUST_SIGNALS_EXTREME
96 ret = pthread_mutex_lock(mutex);
97 if (ret)
98 urcu_die(ret);
99 #else /* #ifndef DISTRUST_SIGNALS_EXTREME */
100 while ((ret = pthread_mutex_trylock(mutex)) != 0) {
101 if (ret != EBUSY && ret != EINTR)
102 urcu_die(ret);
103 poll(NULL,0,10);
104 }
105 #endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
106 }
107
108 static void mutex_unlock(pthread_mutex_t *mutex)
109 {
110 int ret;
111
112 ret = pthread_mutex_unlock(mutex);
113 if (ret)
114 urcu_die(ret);
115 }
116
117 /*
118 * synchronize_rcu() waiting. Single thread.
119 */
120 static void wait_gp(void)
121 {
122 /* Read reader_gp before read futex */
123 cmm_smp_rmb();
124 if (uatomic_read(&rcu_gp.futex) != -1)
125 return;
126 while (futex_noasync(&rcu_gp.futex, FUTEX_WAIT, -1,
127 NULL, NULL, 0)) {
128 switch (errno) {
129 case EWOULDBLOCK:
130 /* Value already changed. */
131 return;
132 case EINTR:
133 /* Retry if interrupted by signal. */
134 break; /* Get out of switch. */
135 default:
136 /* Unexpected error. */
137 urcu_die(errno);
138 }
139 }
140 }
141
142 /*
143 * Always called with rcu_registry lock held. Releases this lock between
144 * iterations and grabs it again. Holds the lock when it returns.
145 */
146 static void wait_for_readers(struct cds_list_head *input_readers,
147 struct cds_list_head *cur_snap_readers,
148 struct cds_list_head *qsreaders)
149 {
150 unsigned int wait_loops = 0;
151 struct rcu_reader *index, *tmp;
152
153 /*
154 * Wait for each thread URCU_TLS(rcu_reader).ctr to either
155 * indicate quiescence (offline), or for them to observe the
156 * current rcu_gp.ctr value.
157 */
158 for (;;) {
159 if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS)
160 wait_loops++;
161 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
162 uatomic_set(&rcu_gp.futex, -1);
163 /*
164 * Write futex before write waiting (the other side
165 * reads them in the opposite order).
166 */
167 cmm_smp_wmb();
168 cds_list_for_each_entry(index, input_readers, node) {
169 _CMM_STORE_SHARED(index->waiting, 1);
170 }
171 /* Write futex before read reader_gp */
172 cmm_smp_mb();
173 }
174 cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
175 switch (rcu_reader_state(&index->ctr)) {
176 case RCU_READER_ACTIVE_CURRENT:
177 if (cur_snap_readers) {
178 cds_list_move(&index->node,
179 cur_snap_readers);
180 break;
181 }
182 /* Fall-through */
183 case RCU_READER_INACTIVE:
184 cds_list_move(&index->node, qsreaders);
185 break;
186 case RCU_READER_ACTIVE_OLD:
187 /*
188 * Old snapshot. Leaving node in
189 * input_readers will make us busy-loop
190 * until the snapshot becomes current or
191 * the reader becomes inactive.
192 */
193 break;
194 }
195 }
196
197 if (cds_list_empty(input_readers)) {
198 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
199 /* Read reader_gp before write futex */
200 cmm_smp_mb();
201 uatomic_set(&rcu_gp.futex, 0);
202 }
203 break;
204 } else {
205 /* Temporarily unlock the registry lock. */
206 mutex_unlock(&rcu_registry_lock);
207 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
208 wait_gp();
209 } else {
210 #ifndef HAS_INCOHERENT_CACHES
211 caa_cpu_relax();
212 #else /* #ifndef HAS_INCOHERENT_CACHES */
213 cmm_smp_mb();
214 #endif /* #else #ifndef HAS_INCOHERENT_CACHES */
215 }
216 /* Re-lock the registry lock before the next loop. */
217 mutex_lock(&rcu_registry_lock);
218 }
219 }
220 }
221
222 /*
223 * Using a two-subphases algorithm for architectures with smaller than 64-bit
224 * long-size to ensure we do not encounter an overflow bug.
225 */
226
227 #if (CAA_BITS_PER_LONG < 64)
228 void synchronize_rcu(void)
229 {
230 CDS_LIST_HEAD(cur_snap_readers);
231 CDS_LIST_HEAD(qsreaders);
232 unsigned long was_online;
233 DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING);
234 struct urcu_waiters waiters;
235
236 was_online = rcu_read_ongoing();
237
238 /* All threads should read qparity before accessing data structure
239 * where new ptr points to. In the "then" case, rcu_thread_offline
240 * includes a memory barrier.
241 *
242 * Mark the writer thread offline to make sure we don't wait for
243 * our own quiescent state. This allows using synchronize_rcu()
244 * in threads registered as readers.
245 */
246 if (was_online)
247 rcu_thread_offline();
248 else
249 cmm_smp_mb();
250
251 /*
252 * Add ourself to gp_waiters queue of threads awaiting to wait
253 * for a grace period. Proceed to perform the grace period only
254 * if we are the first thread added into the queue.
255 */
256 if (urcu_wait_add(&gp_waiters, &wait) != 0) {
257 /* Not first in queue: will be awakened by another thread. */
258 urcu_adaptative_busy_wait(&wait);
259 goto gp_end;
260 }
261 /* We won't need to wake ourself up */
262 urcu_wait_set_state(&wait, URCU_WAIT_RUNNING);
263
264 mutex_lock(&rcu_gp_lock);
265
266 /*
267 * Move all waiters into our local queue.
268 */
269 urcu_move_waiters(&waiters, &gp_waiters);
270
271 mutex_lock(&rcu_registry_lock);
272
273 if (cds_list_empty(&registry))
274 goto out;
275
276 /*
277 * Wait for readers to observe original parity or be quiescent.
278 * wait_for_readers() can release and grab again rcu_registry_lock
279 * interally.
280 */
281 wait_for_readers(&registry, &cur_snap_readers, &qsreaders);
282
283 /*
284 * Must finish waiting for quiescent state for original parity
285 * before committing next rcu_gp.ctr update to memory. Failure
286 * to do so could result in the writer waiting forever while new
287 * readers are always accessing data (no progress). Enforce
288 * compiler-order of load URCU_TLS(rcu_reader).ctr before store
289 * to rcu_gp.ctr.
290 */
291 cmm_barrier();
292
293 /*
294 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
295 * model easier to understand. It does not have a big performance impact
296 * anyway, given this is the write-side.
297 */
298 cmm_smp_mb();
299
300 /* Switch parity: 0 -> 1, 1 -> 0 */
301 CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr ^ RCU_GP_CTR);
302
303 /*
304 * Must commit rcu_gp.ctr update to memory before waiting for
305 * quiescent state. Failure to do so could result in the writer
306 * waiting forever while new readers are always accessing data
307 * (no progress). Enforce compiler-order of store to rcu_gp.ctr
308 * before load URCU_TLS(rcu_reader).ctr.
309 */
310 cmm_barrier();
311
312 /*
313 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
314 * model easier to understand. It does not have a big performance impact
315 * anyway, given this is the write-side.
316 */
317 cmm_smp_mb();
318
319 /*
320 * Wait for readers to observe new parity or be quiescent.
321 * wait_for_readers() can release and grab again rcu_registry_lock
322 * interally.
323 */
324 wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
325
326 /*
327 * Put quiescent reader list back into registry.
328 */
329 cds_list_splice(&qsreaders, &registry);
330 out:
331 mutex_unlock(&rcu_registry_lock);
332 mutex_unlock(&rcu_gp_lock);
333 urcu_wake_all_waiters(&waiters);
334 gp_end:
335 /*
336 * Finish waiting for reader threads before letting the old ptr being
337 * freed.
338 */
339 if (was_online)
340 rcu_thread_online();
341 else
342 cmm_smp_mb();
343 }
344 #else /* !(CAA_BITS_PER_LONG < 64) */
345 void synchronize_rcu(void)
346 {
347 CDS_LIST_HEAD(qsreaders);
348 unsigned long was_online;
349 DEFINE_URCU_WAIT_NODE(wait, URCU_WAIT_WAITING);
350 struct urcu_waiters waiters;
351
352 was_online = rcu_read_ongoing();
353
354 /*
355 * Mark the writer thread offline to make sure we don't wait for
356 * our own quiescent state. This allows using synchronize_rcu()
357 * in threads registered as readers.
358 */
359 if (was_online)
360 rcu_thread_offline();
361 else
362 cmm_smp_mb();
363
364 /*
365 * Add ourself to gp_waiters queue of threads awaiting to wait
366 * for a grace period. Proceed to perform the grace period only
367 * if we are the first thread added into the queue.
368 */
369 if (urcu_wait_add(&gp_waiters, &wait) != 0) {
370 /* Not first in queue: will be awakened by another thread. */
371 urcu_adaptative_busy_wait(&wait);
372 goto gp_end;
373 }
374 /* We won't need to wake ourself up */
375 urcu_wait_set_state(&wait, URCU_WAIT_RUNNING);
376
377 mutex_lock(&rcu_gp_lock);
378
379 /*
380 * Move all waiters into our local queue.
381 */
382 urcu_move_waiters(&waiters, &gp_waiters);
383
384 mutex_lock(&rcu_registry_lock);
385
386 if (cds_list_empty(&registry))
387 goto out;
388
389 /* Increment current G.P. */
390 CMM_STORE_SHARED(rcu_gp.ctr, rcu_gp.ctr + RCU_GP_CTR);
391
392 /*
393 * Must commit rcu_gp.ctr update to memory before waiting for
394 * quiescent state. Failure to do so could result in the writer
395 * waiting forever while new readers are always accessing data
396 * (no progress). Enforce compiler-order of store to rcu_gp.ctr
397 * before load URCU_TLS(rcu_reader).ctr.
398 */
399 cmm_barrier();
400
401 /*
402 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
403 * model easier to understand. It does not have a big performance impact
404 * anyway, given this is the write-side.
405 */
406 cmm_smp_mb();
407
408 /*
409 * Wait for readers to observe new count of be quiescent.
410 * wait_for_readers() can release and grab again rcu_registry_lock
411 * interally.
412 */
413 wait_for_readers(&registry, NULL, &qsreaders);
414
415 /*
416 * Put quiescent reader list back into registry.
417 */
418 cds_list_splice(&qsreaders, &registry);
419 out:
420 mutex_unlock(&rcu_registry_lock);
421 mutex_unlock(&rcu_gp_lock);
422 urcu_wake_all_waiters(&waiters);
423 gp_end:
424 if (was_online)
425 rcu_thread_online();
426 else
427 cmm_smp_mb();
428 }
429 #endif /* !(CAA_BITS_PER_LONG < 64) */
430
431 /*
432 * library wrappers to be used by non-LGPL compatible source code.
433 */
434
435 void rcu_read_lock(void)
436 {
437 _rcu_read_lock();
438 }
439
440 void rcu_read_unlock(void)
441 {
442 _rcu_read_unlock();
443 }
444
445 int rcu_read_ongoing(void)
446 {
447 return _rcu_read_ongoing();
448 }
449
450 void rcu_quiescent_state(void)
451 {
452 _rcu_quiescent_state();
453 }
454
455 void rcu_thread_offline(void)
456 {
457 _rcu_thread_offline();
458 }
459
460 void rcu_thread_online(void)
461 {
462 _rcu_thread_online();
463 }
464
465 void rcu_register_thread(void)
466 {
467 URCU_TLS(rcu_reader).tid = pthread_self();
468 assert(URCU_TLS(rcu_reader).ctr == 0);
469
470 mutex_lock(&rcu_registry_lock);
471 assert(!URCU_TLS(rcu_reader).registered);
472 URCU_TLS(rcu_reader).registered = 1;
473 cds_list_add(&URCU_TLS(rcu_reader).node, &registry);
474 mutex_unlock(&rcu_registry_lock);
475 _rcu_thread_online();
476 }
477
478 void rcu_unregister_thread(void)
479 {
480 /*
481 * We have to make the thread offline otherwise we end up dealocking
482 * with a waiting writer.
483 */
484 _rcu_thread_offline();
485 assert(URCU_TLS(rcu_reader).registered);
486 URCU_TLS(rcu_reader).registered = 0;
487 mutex_lock(&rcu_registry_lock);
488 cds_list_del(&URCU_TLS(rcu_reader).node);
489 mutex_unlock(&rcu_registry_lock);
490 }
491
492 void rcu_exit(void)
493 {
494 /*
495 * Assertion disabled because call_rcu threads are now rcu
496 * readers, and left running at exit.
497 * assert(cds_list_empty(&registry));
498 */
499 }
500
501 DEFINE_RCU_FLAVOR(rcu_flavor);
502
503 #include "urcu-call-rcu-impl.h"
504 #include "urcu-defer-impl.h"
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