tests: use standard malloc/free for synchronize_rcu()
[urcu.git] / urcu-qsbr.c
CommitLineData
9f1621ca 1/*
7ac06cef 2 * urcu-qsbr.c
9f1621ca 3 *
7ac06cef 4 * Userspace RCU QSBR library
9f1621ca 5 *
6982d6d7 6 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
9f1621ca
MD
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
c1d2c60b 26#define _GNU_SOURCE
71c811bf 27#define _LGPL_SOURCE
9f1621ca
MD
28#include <stdio.h>
29#include <pthread.h>
30#include <signal.h>
31#include <assert.h>
32#include <stdlib.h>
6d841bc2 33#include <stdint.h>
9f1621ca
MD
34#include <string.h>
35#include <errno.h>
36#include <poll.h>
37
d73fb81f 38#include "urcu/wfcqueue.h"
57760d44 39#include "urcu/map/urcu-qsbr.h"
727f819d 40#define BUILD_QSBR_LIB
af7c2dbe 41#include "urcu/static/urcu-qsbr.h"
618b2595 42#include "urcu-pointer.h"
bd252a04 43#include "urcu/tls-compat.h"
71c811bf 44
4a6d7378
MD
45#include "urcu-die.h"
46
9f1621ca 47/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
71c811bf 48#undef _LGPL_SOURCE
7ac06cef 49#include "urcu-qsbr.h"
71c811bf 50#define _LGPL_SOURCE
9f1621ca 51
f6d18c64
MD
52void __attribute__((destructor)) rcu_exit(void);
53
6abb4bd5 54static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
9f1621ca 55
1de4df4b 56int32_t rcu_gp_futex;
bc6c15bb 57
9f1621ca
MD
58/*
59 * Global grace period counter.
60 */
02be5561 61unsigned long rcu_gp_ctr = RCU_GP_ONLINE;
9f1621ca 62
408f6d92
PB
63/*
64 * Active attempts to check for reader Q.S. before calling futex().
65 */
66#define RCU_QS_ACTIVE_ATTEMPTS 100
67
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MD
68/*
69 * Written to only by each individual reader. Read by both the reader and the
70 * writers.
71 */
bd252a04 72DEFINE_URCU_TLS(struct rcu_reader, rcu_reader);
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MD
73
74#ifdef DEBUG_YIELD
1de4df4b
MD
75unsigned int rcu_yield_active;
76DEFINE_URCU_TLS(unsigned int, rcu_rand_yield);
9f1621ca
MD
77#endif
78
16aa9ee8 79static CDS_LIST_HEAD(registry);
9f1621ca 80
6abb4bd5 81static void mutex_lock(pthread_mutex_t *mutex)
9f1621ca
MD
82{
83 int ret;
84
85#ifndef DISTRUST_SIGNALS_EXTREME
6abb4bd5 86 ret = pthread_mutex_lock(mutex);
4a6d7378
MD
87 if (ret)
88 urcu_die(ret);
9f1621ca 89#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
6abb4bd5 90 while ((ret = pthread_mutex_trylock(mutex)) != 0) {
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MD
91 if (ret != EBUSY && ret != EINTR)
92 urcu_die(ret);
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MD
93 poll(NULL,0,10);
94 }
95#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
96}
97
6abb4bd5 98static void mutex_unlock(pthread_mutex_t *mutex)
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MD
99{
100 int ret;
101
6abb4bd5 102 ret = pthread_mutex_unlock(mutex);
4a6d7378
MD
103 if (ret)
104 urcu_die(ret);
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MD
105}
106
bc6c15bb
MD
107/*
108 * synchronize_rcu() waiting. Single thread.
109 */
4d703340 110static void wait_gp(void)
bc6c15bb 111{
4d703340 112 /* Read reader_gp before read futex */
5481ddb3 113 cmm_smp_rmb();
1de4df4b
MD
114 if (uatomic_read(&rcu_gp_futex) == -1)
115 futex_noasync(&rcu_gp_futex, FUTEX_WAIT, -1,
4d703340 116 NULL, NULL, 0);
bc6c15bb
MD
117}
118
708d89f0
MD
119static void wait_for_readers(struct cds_list_head *input_readers,
120 struct cds_list_head *cur_snap_readers,
121 struct cds_list_head *qsreaders)
9f1621ca 122{
4d703340 123 int wait_loops = 0;
02be5561 124 struct rcu_reader *index, *tmp;
9f1621ca 125
9f1621ca 126 /*
f6b42f9c
MD
127 * Wait for each thread URCU_TLS(rcu_reader).ctr to either
128 * indicate quiescence (offline), or for them to observe the
129 * current rcu_gp_ctr value.
9f1621ca 130 */
4d703340
MD
131 for (;;) {
132 wait_loops++;
83a2c421 133 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
1de4df4b 134 uatomic_set(&rcu_gp_futex, -1);
83a2c421
PB
135 /*
136 * Write futex before write waiting (the other side
137 * reads them in the opposite order).
138 */
139 cmm_smp_wmb();
708d89f0 140 cds_list_for_each_entry(index, input_readers, node) {
83a2c421
PB
141 _CMM_STORE_SHARED(index->waiting, 1);
142 }
4d703340 143 /* Write futex before read reader_gp */
5481ddb3 144 cmm_smp_mb();
4d703340 145 }
708d89f0
MD
146 cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
147 switch (rcu_reader_state(&index->ctr)) {
148 case RCU_READER_ACTIVE_CURRENT:
149 if (cur_snap_readers) {
150 cds_list_move(&index->node,
151 cur_snap_readers);
152 break;
153 }
154 /* Fall-through */
155 case RCU_READER_INACTIVE:
156 cds_list_move(&index->node, qsreaders);
157 break;
158 case RCU_READER_ACTIVE_OLD:
159 /*
160 * Old snapshot. Leaving node in
161 * input_readers will make us busy-loop
162 * until the snapshot becomes current or
163 * the reader becomes inactive.
164 */
165 break;
166 }
4d703340 167 }
bc6c15bb 168
708d89f0 169 if (cds_list_empty(input_readers)) {
83a2c421 170 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
4d703340 171 /* Read reader_gp before write futex */
5481ddb3 172 cmm_smp_mb();
1de4df4b 173 uatomic_set(&rcu_gp_futex, 0);
4d703340
MD
174 }
175 break;
176 } else {
83a2c421 177 if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
4d703340 178 wait_gp();
bc6c15bb 179 } else {
9f1621ca 180#ifndef HAS_INCOHERENT_CACHES
06f22bdb 181 caa_cpu_relax();
9f1621ca 182#else /* #ifndef HAS_INCOHERENT_CACHES */
5481ddb3 183 cmm_smp_mb();
9f1621ca 184#endif /* #else #ifndef HAS_INCOHERENT_CACHES */
bc6c15bb
MD
185 }
186 }
9f1621ca
MD
187 }
188}
189
47d2f29e
MD
190/*
191 * Using a two-subphases algorithm for architectures with smaller than 64-bit
192 * long-size to ensure we do not encounter an overflow bug.
193 */
194
b39e1761 195#if (CAA_BITS_PER_LONG < 64)
47d2f29e
MD
196void synchronize_rcu(void)
197{
708d89f0
MD
198 CDS_LIST_HEAD(cur_snap_readers);
199 CDS_LIST_HEAD(qsreaders);
bc49c323
MD
200 unsigned long was_online;
201
bd252a04 202 was_online = URCU_TLS(rcu_reader).ctr;
bc49c323 203
47d2f29e 204 /* All threads should read qparity before accessing data structure
27b940e7
PB
205 * where new ptr points to. In the "then" case, rcu_thread_offline
206 * includes a memory barrier.
207 *
bc49c323 208 * Mark the writer thread offline to make sure we don't wait for
5e77fc1f
PM
209 * our own quiescent state. This allows using synchronize_rcu()
210 * in threads registered as readers.
bc49c323 211 */
27b940e7
PB
212 if (was_online)
213 rcu_thread_offline();
214 else
215 cmm_smp_mb();
bc49c323 216
6abb4bd5 217 mutex_lock(&rcu_gp_lock);
47d2f29e 218
16aa9ee8 219 if (cds_list_empty(&registry))
2dfb8b5e 220 goto out;
47d2f29e
MD
221
222 /*
f6b42f9c 223 * Wait for readers to observe original parity or be quiescent.
47d2f29e 224 */
708d89f0 225 wait_for_readers(&registry, &cur_snap_readers, &qsreaders);
47d2f29e
MD
226
227 /*
f6b42f9c
MD
228 * Must finish waiting for quiescent state for original parity
229 * before committing next rcu_gp_ctr update to memory. Failure
230 * to do so could result in the writer waiting forever while new
5e77fc1f 231 * readers are always accessing data (no progress). Enforce
f6b42f9c
MD
232 * compiler-order of load URCU_TLS(rcu_reader).ctr before store
233 * to rcu_gp_ctr.
47d2f29e 234 */
5481ddb3 235 cmm_barrier();
47d2f29e 236
47d2f29e 237 /*
5481ddb3 238 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
2dfb8b5e
MD
239 * model easier to understand. It does not have a big performance impact
240 * anyway, given this is the write-side.
47d2f29e 241 */
5481ddb3 242 cmm_smp_mb();
47d2f29e 243
f6b42f9c
MD
244 /* Switch parity: 0 -> 1, 1 -> 0 */
245 CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR);
246
47d2f29e 247 /*
f6b42f9c
MD
248 * Must commit rcu_gp_ctr update to memory before waiting for
249 * quiescent state. Failure to do so could result in the writer
250 * waiting forever while new readers are always accessing data
251 * (no progress). Enforce compiler-order of store to rcu_gp_ctr
252 * before load URCU_TLS(rcu_reader).ctr.
47d2f29e 253 */
f6b42f9c
MD
254 cmm_barrier();
255
256 /*
257 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
258 * model easier to understand. It does not have a big performance impact
259 * anyway, given this is the write-side.
260 */
261 cmm_smp_mb();
262
263 /*
264 * Wait for readers to observe new parity or be quiescent.
265 */
708d89f0
MD
266 wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
267
268 /*
269 * Put quiescent reader list back into registry.
270 */
271 cds_list_splice(&qsreaders, &registry);
2dfb8b5e 272out:
6abb4bd5 273 mutex_unlock(&rcu_gp_lock);
47d2f29e 274
bc49c323
MD
275 /*
276 * Finish waiting for reader threads before letting the old ptr being
47d2f29e
MD
277 * freed.
278 */
bc49c323 279 if (was_online)
27b940e7
PB
280 rcu_thread_online();
281 else
282 cmm_smp_mb();
47d2f29e 283}
b39e1761 284#else /* !(CAA_BITS_PER_LONG < 64) */
9f1621ca
MD
285void synchronize_rcu(void)
286{
708d89f0 287 CDS_LIST_HEAD(qsreaders);
f0f7dbdd 288 unsigned long was_online;
ff2f67a0 289
bd252a04 290 was_online = URCU_TLS(rcu_reader).ctr;
ff2f67a0
MD
291
292 /*
293 * Mark the writer thread offline to make sure we don't wait for
5e77fc1f
PM
294 * our own quiescent state. This allows using synchronize_rcu()
295 * in threads registered as readers.
ff2f67a0 296 */
27b940e7
PB
297 if (was_online)
298 rcu_thread_offline();
299 else
300 cmm_smp_mb();
ff2f67a0 301
6abb4bd5 302 mutex_lock(&rcu_gp_lock);
16aa9ee8 303 if (cds_list_empty(&registry))
2dfb8b5e 304 goto out;
f6b42f9c
MD
305
306 /* Increment current G.P. */
307 CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr + RCU_GP_CTR);
308
309 /*
310 * Must commit rcu_gp_ctr update to memory before waiting for
311 * quiescent state. Failure to do so could result in the writer
312 * waiting forever while new readers are always accessing data
313 * (no progress). Enforce compiler-order of store to rcu_gp_ctr
314 * before load URCU_TLS(rcu_reader).ctr.
315 */
316 cmm_barrier();
317
318 /*
319 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
320 * model easier to understand. It does not have a big performance impact
321 * anyway, given this is the write-side.
322 */
323 cmm_smp_mb();
324
325 /*
326 * Wait for readers to observe new count of be quiescent.
327 */
708d89f0
MD
328 wait_for_readers(&registry, NULL, &qsreaders);
329
330 /*
331 * Put quiescent reader list back into registry.
332 */
333 cds_list_splice(&qsreaders, &registry);
2dfb8b5e 334out:
6abb4bd5 335 mutex_unlock(&rcu_gp_lock);
ff2f67a0
MD
336
337 if (was_online)
27b940e7
PB
338 rcu_thread_online();
339 else
340 cmm_smp_mb();
9f1621ca 341}
b39e1761 342#endif /* !(CAA_BITS_PER_LONG < 64) */
9f1621ca
MD
343
344/*
345 * library wrappers to be used by non-LGPL compatible source code.
346 */
347
348void rcu_read_lock(void)
349{
350 _rcu_read_lock();
351}
352
353void rcu_read_unlock(void)
354{
355 _rcu_read_unlock();
356}
357
7ac06cef
MD
358void rcu_quiescent_state(void)
359{
360 _rcu_quiescent_state();
361}
362
363void rcu_thread_offline(void)
364{
365 _rcu_thread_offline();
366}
367
368void rcu_thread_online(void)
369{
370 _rcu_thread_online();
371}
372
9f1621ca
MD
373void rcu_register_thread(void)
374{
bd252a04
MD
375 URCU_TLS(rcu_reader).tid = pthread_self();
376 assert(URCU_TLS(rcu_reader).ctr == 0);
4f8e3380 377
6abb4bd5 378 mutex_lock(&rcu_gp_lock);
bd252a04 379 cds_list_add(&URCU_TLS(rcu_reader).node, &registry);
6abb4bd5 380 mutex_unlock(&rcu_gp_lock);
5f373c84 381 _rcu_thread_online();
9f1621ca
MD
382}
383
384void rcu_unregister_thread(void)
385{
76f3022f
MD
386 /*
387 * We have to make the thread offline otherwise we end up dealocking
388 * with a waiting writer.
389 */
390 _rcu_thread_offline();
6abb4bd5 391 mutex_lock(&rcu_gp_lock);
bd252a04 392 cds_list_del(&URCU_TLS(rcu_reader).node);
6abb4bd5 393 mutex_unlock(&rcu_gp_lock);
9f1621ca 394}
f6d18c64
MD
395
396void rcu_exit(void)
397{
01cadde4
MD
398 /*
399 * Assertion disabled because call_rcu threads are now rcu
400 * readers, and left running at exit.
401 * assert(cds_list_empty(&registry));
402 */
f6d18c64 403}
5e77fc1f 404
5e6b23a6 405DEFINE_RCU_FLAVOR(rcu_flavor);
541d828d 406
5e77fc1f 407#include "urcu-call-rcu-impl.h"
0376e7b2 408#include "urcu-defer-impl.h"
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