urcu-bp: move private definitions to .c file
[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
27b012e2
MD
28#include <stdio.h>
29#include <pthread.h>
30#include <signal.h>
31#include <assert.h>
f69f195a 32#include <stdlib.h>
6d841bc2 33#include <stdint.h>
f69f195a 34#include <string.h>
09a9f986 35#include <errno.h>
e8043c1b 36#include <poll.h>
27b012e2 37
57760d44 38#include "urcu/map/urcu.h"
5e77fc1f 39
af7c2dbe 40#include "urcu/static/urcu.h"
121a5d44 41/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
27b012e2
MD
42#include "urcu.h"
43
fdf01eed 44#ifdef RCU_MEMBARRIER
834a45ba 45static int init_done;
fdf01eed 46int has_sys_membarrier;
834a45ba 47
02be5561 48void __attribute__((constructor)) rcu_init(void);
fdf01eed
MD
49#endif
50
51#ifdef RCU_MB
02be5561 52void rcu_init(void)
e90a6e9c
MD
53{
54}
55#endif
8a5fb4c9 56
fdf01eed
MD
57#ifdef RCU_SIGNAL
58static int init_done;
59
60void __attribute__((constructor)) rcu_init(void);
61void __attribute__((destructor)) rcu_exit(void);
62#endif
63
6abb4bd5 64static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
27b012e2 65
6d841bc2 66int32_t gp_futex;
bc6c15bb 67
128166c9
MD
68/*
69 * Global grace period counter.
02be5561 70 * Contains the current RCU_GP_CTR_PHASE.
afb8f2c9 71 * Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
b0d5e790 72 * Written to only by writer with mutex taken. Read by both writer and readers.
128166c9 73 */
27d65bc5 74unsigned long rcu_gp_ctr = RCU_GP_COUNT;
27b012e2 75
b0d5e790
MD
76/*
77 * Written to only by each individual reader. Read by both the reader and the
78 * writers.
79 */
02be5561 80struct rcu_reader __thread rcu_reader;
27b012e2 81
cf380c2f 82#ifdef DEBUG_YIELD
9d335088
MD
83unsigned int yield_active;
84unsigned int __thread rand_yield;
cf380c2f
MD
85#endif
86
16aa9ee8 87static CDS_LIST_HEAD(registry);
27b012e2 88
6abb4bd5 89static void mutex_lock(pthread_mutex_t *mutex)
41718ff9
MD
90{
91 int ret;
09a9f986
PM
92
93#ifndef DISTRUST_SIGNALS_EXTREME
6abb4bd5 94 ret = pthread_mutex_lock(mutex);
41718ff9
MD
95 if (ret) {
96 perror("Error in pthread mutex lock");
97 exit(-1);
98 }
09a9f986 99#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
6abb4bd5 100 while ((ret = pthread_mutex_trylock(mutex)) != 0) {
09a9f986
PM
101 if (ret != EBUSY && ret != EINTR) {
102 printf("ret = %d, errno = %d\n", ret, errno);
103 perror("Error in pthread mutex lock");
104 exit(-1);
105 }
6cf3827c 106 if (CMM_LOAD_SHARED(rcu_reader.need_mb)) {
5481ddb3 107 cmm_smp_mb();
6cf3827c 108 _CMM_STORE_SHARED(rcu_reader.need_mb, 0);
5481ddb3 109 cmm_smp_mb();
09a9f986
PM
110 }
111 poll(NULL,0,10);
112 }
113#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
41718ff9
MD
114}
115
6abb4bd5 116static void mutex_unlock(pthread_mutex_t *mutex)
41718ff9
MD
117{
118 int ret;
119
6abb4bd5 120 ret = pthread_mutex_unlock(mutex);
41718ff9
MD
121 if (ret) {
122 perror("Error in pthread mutex unlock");
123 exit(-1);
124 }
125}
126
fdf01eed 127#ifdef RCU_MEMBARRIER
25cc6d18 128static void smp_mb_master(int group)
fdf01eed
MD
129{
130 if (likely(has_sys_membarrier))
f0708810 131 membarrier(MEMBARRIER_EXPEDITED);
fdf01eed 132 else
5481ddb3 133 cmm_smp_mb();
fdf01eed
MD
134}
135#endif
136
02be5561 137#ifdef RCU_MB
25cc6d18 138static void smp_mb_master(int group)
40e140c9 139{
5481ddb3 140 cmm_smp_mb();
40e140c9 141}
fdf01eed
MD
142#endif
143
144#ifdef RCU_SIGNAL
78ff9419 145static void force_mb_all_readers(void)
27b012e2 146{
02be5561 147 struct rcu_reader *index;
e3b0cef0 148
27b012e2 149 /*
5481ddb3 150 * Ask for each threads to execute a cmm_smp_mb() so we can consider the
27b012e2
MD
151 * compiler barriers around rcu read lock as real memory barriers.
152 */
16aa9ee8 153 if (cds_list_empty(&registry))
27b012e2 154 return;
3a86deba 155 /*
5481ddb3 156 * pthread_kill has a cmm_smp_mb(). But beware, we assume it performs
157dca95 157 * a cache flush on architectures with non-coherent cache. Let's play
5481ddb3 158 * safe and don't assume anything : we use cmm_smp_mc() to make sure the
157dca95 159 * cache flush is enforced.
3a86deba 160 */
16aa9ee8 161 cds_list_for_each_entry(index, &registry, node) {
6cf3827c 162 CMM_STORE_SHARED(index->need_mb, 1);
02be5561 163 pthread_kill(index->tid, SIGRCU);
09a9f986 164 }
27b012e2
MD
165 /*
166 * Wait for sighandler (and thus mb()) to execute on every thread.
09a9f986
PM
167 *
168 * Note that the pthread_kill() will never be executed on systems
169 * that correctly deliver signals in a timely manner. However, it
170 * is not uncommon for kernels to have bugs that can result in
171 * lost or unduly delayed signals.
172 *
173 * If you are seeing the below pthread_kill() executing much at
174 * all, we suggest testing the underlying kernel and filing the
175 * relevant bug report. For Linux kernels, we recommend getting
176 * the Linux Test Project (LTP).
27b012e2 177 */
16aa9ee8 178 cds_list_for_each_entry(index, &registry, node) {
6cf3827c 179 while (CMM_LOAD_SHARED(index->need_mb)) {
02be5561 180 pthread_kill(index->tid, SIGRCU);
09a9f986
PM
181 poll(NULL, 0, 1);
182 }
183 }
5481ddb3 184 cmm_smp_mb(); /* read ->need_mb before ending the barrier */
27b012e2 185}
9d7e3f89 186
25cc6d18 187static void smp_mb_master(int group)
9d7e3f89
MD
188{
189 force_mb_all_readers();
190}
fdf01eed 191#endif /* #ifdef RCU_SIGNAL */
27b012e2 192
bc6c15bb
MD
193/*
194 * synchronize_rcu() waiting. Single thread.
195 */
cfe78e25 196static void wait_gp(void)
bc6c15bb 197{
cfe78e25 198 /* Read reader_gp before read futex */
25cc6d18 199 smp_mb_master(RCU_MB_GROUP);
cfe78e25 200 if (uatomic_read(&gp_futex) == -1)
0854ccff 201 futex_async(&gp_futex, FUTEX_WAIT, -1,
cfe78e25 202 NULL, NULL, 0);
bc6c15bb
MD
203}
204
2dfb8b5e 205void update_counter_and_wait(void)
27b012e2 206{
16aa9ee8 207 CDS_LIST_HEAD(qsreaders);
cfe78e25 208 int wait_loops = 0;
02be5561 209 struct rcu_reader *index, *tmp;
27b012e2 210
32c15e4e 211 /* Switch parity: 0 -> 1, 1 -> 0 */
6cf3827c 212 CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
2dfb8b5e
MD
213
214 /*
d40fde2c
MD
215 * Must commit rcu_gp_ctr update to memory before waiting for quiescent
216 * state. Failure to do so could result in the writer waiting forever
217 * while new readers are always accessing data (no progress). Enforce
218 * compiler-order of store to rcu_gp_ctr before load rcu_reader ctr.
2dfb8b5e 219 */
5481ddb3 220 cmm_barrier();
2dfb8b5e
MD
221
222 /*
935b11ff 223 *
5481ddb3 224 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
2dfb8b5e
MD
225 * model easier to understand. It does not have a big performance impact
226 * anyway, given this is the write-side.
227 */
5481ddb3 228 cmm_smp_mb();
2dfb8b5e 229
40e140c9 230 /*
02be5561 231 * Wait for each thread rcu_reader.ctr count to become 0.
27b012e2 232 */
cfe78e25
MD
233 for (;;) {
234 wait_loops++;
235 if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
236 uatomic_dec(&gp_futex);
237 /* Write futex before read reader_gp */
25cc6d18 238 smp_mb_master(RCU_MB_GROUP);
cfe78e25
MD
239 }
240
16aa9ee8 241 cds_list_for_each_entry_safe(index, tmp, &registry, node) {
b95a001f 242 if (!rcu_gp_ongoing(&index->ctr))
16aa9ee8 243 cds_list_move(&index->node, &qsreaders);
cfe78e25
MD
244 }
245
e8043c1b 246#ifndef HAS_INCOHERENT_CACHES
16aa9ee8 247 if (cds_list_empty(&registry)) {
cfe78e25
MD
248 if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
249 /* Read reader_gp before write futex */
25cc6d18 250 smp_mb_master(RCU_MB_GROUP);
cfe78e25 251 uatomic_set(&gp_futex, 0);
bc6c15bb 252 }
cfe78e25
MD
253 break;
254 } else {
255 if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
256 wait_gp();
257 else
06f22bdb 258 caa_cpu_relax();
bc6c15bb 259 }
e8043c1b 260#else /* #ifndef HAS_INCOHERENT_CACHES */
27b012e2 261 /*
40e140c9 262 * BUSY-LOOP. Force the reader thread to commit its
02be5561 263 * rcu_reader.ctr update to memory if we wait for too long.
27b012e2 264 */
16aa9ee8 265 if (cds_list_empty(&registry)) {
cfe78e25
MD
266 if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
267 /* Read reader_gp before write futex */
25cc6d18 268 smp_mb_master(RCU_MB_GROUP);
cfe78e25
MD
269 uatomic_set(&gp_futex, 0);
270 }
271 break;
272 } else {
273 switch (wait_loops) {
bc6c15bb 274 case RCU_QS_ACTIVE_ATTEMPTS:
cfe78e25
MD
275 wait_gp();
276 break; /* only escape switch */
bc6c15bb 277 case KICK_READER_LOOPS:
25cc6d18 278 smp_mb_master(RCU_MB_GROUP);
40e140c9 279 wait_loops = 0;
cfe78e25 280 break; /* only escape switch */
bc6c15bb 281 default:
06f22bdb 282 caa_cpu_relax();
40e140c9
MD
283 }
284 }
e8043c1b 285#endif /* #else #ifndef HAS_INCOHERENT_CACHES */
27b012e2 286 }
cfe78e25 287 /* put back the reader list in the registry */
16aa9ee8 288 cds_list_splice(&qsreaders, &registry);
27b012e2
MD
289}
290
9598a481 291void synchronize_rcu(void)
2bc59bd7 292{
6abb4bd5 293 mutex_lock(&rcu_gp_lock);
135530fd 294
16aa9ee8 295 if (cds_list_empty(&registry))
2dfb8b5e
MD
296 goto out;
297
9598a481 298 /* All threads should read qparity before accessing data structure
6abb4bd5
MD
299 * where new ptr points to. Must be done within rcu_gp_lock because it
300 * iterates on reader threads.*/
9598a481 301 /* Write new ptr before changing the qparity */
25cc6d18 302 smp_mb_master(RCU_MB_GROUP);
9598a481 303
9598a481
MD
304 /*
305 * Wait for previous parity to be empty of readers.
306 */
2dfb8b5e 307 update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */
9598a481
MD
308
309 /*
310 * Must finish waiting for quiescent state for parity 0 before
d40fde2c
MD
311 * committing next rcu_gp_ctr update to memory. Failure to do so could
312 * result in the writer waiting forever while new readers are always
313 * accessing data (no progress). Enforce compiler-order of load
314 * rcu_reader ctr before store to rcu_gp_ctr.
9598a481 315 */
5481ddb3 316 cmm_barrier();
9598a481 317
5dba80f9 318 /*
5481ddb3 319 * Adding a cmm_smp_mb() which is _not_ formally required, but makes the
5dba80f9
MD
320 * model easier to understand. It does not have a big performance impact
321 * anyway, given this is the write-side.
322 */
5481ddb3 323 cmm_smp_mb();
67c2d80b 324
9598a481
MD
325 /*
326 * Wait for previous parity to be empty of readers.
327 */
2dfb8b5e 328 update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */
9598a481 329
9598a481 330 /* Finish waiting for reader threads before letting the old ptr being
6abb4bd5
MD
331 * freed. Must be done within rcu_gp_lock because it iterates on reader
332 * threads. */
25cc6d18 333 smp_mb_master(RCU_MB_GROUP);
2dfb8b5e 334out:
6abb4bd5 335 mutex_unlock(&rcu_gp_lock);
2bc59bd7
PM
336}
337
121a5d44
MD
338/*
339 * library wrappers to be used by non-LGPL compatible source code.
340 */
341
342void rcu_read_lock(void)
343{
344 _rcu_read_lock();
345}
346
347void rcu_read_unlock(void)
348{
349 _rcu_read_unlock();
350}
351
121a5d44 352void rcu_register_thread(void)
27b012e2 353{
02be5561
MD
354 rcu_reader.tid = pthread_self();
355 assert(rcu_reader.need_mb == 0);
4b5be3be 356 assert(!(rcu_reader.ctr & RCU_GP_CTR_NEST_MASK));
02be5561 357
6abb4bd5 358 mutex_lock(&rcu_gp_lock);
02be5561 359 rcu_init(); /* In case gcc does not support constructor attribute */
16aa9ee8 360 cds_list_add(&rcu_reader.node, &registry);
6abb4bd5 361 mutex_unlock(&rcu_gp_lock);
27b012e2
MD
362}
363
121a5d44 364void rcu_unregister_thread(void)
27b012e2 365{
6abb4bd5 366 mutex_lock(&rcu_gp_lock);
16aa9ee8 367 cds_list_del(&rcu_reader.node);
6abb4bd5 368 mutex_unlock(&rcu_gp_lock);
27b012e2
MD
369}
370
fdf01eed
MD
371#ifdef RCU_MEMBARRIER
372void rcu_init(void)
373{
374 if (init_done)
375 return;
376 init_done = 1;
cf5271ee 377 if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY))
fdf01eed
MD
378 has_sys_membarrier = 1;
379}
380#endif
381
382#ifdef RCU_SIGNAL
02be5561 383static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context)
27b012e2 384{
40e140c9 385 /*
5481ddb3
DG
386 * Executing this cmm_smp_mb() is the only purpose of this signal handler.
387 * It punctually promotes cmm_barrier() into cmm_smp_mb() on every thread it is
40e140c9
MD
388 * executed on.
389 */
5481ddb3 390 cmm_smp_mb();
6cf3827c 391 _CMM_STORE_SHARED(rcu_reader.need_mb, 0);
5481ddb3 392 cmm_smp_mb();
27b012e2
MD
393}
394
8a5fb4c9 395/*
02be5561 396 * rcu_init constructor. Called when the library is linked, but also when
8a5fb4c9
MD
397 * reader threads are calling rcu_register_thread().
398 * Should only be called by a single thread at a given time. This is ensured by
6abb4bd5
MD
399 * holing the rcu_gp_lock from rcu_register_thread() or by running at library
400 * load time, which should not be executed by multiple threads nor concurrently
401 * with rcu_register_thread() anyway.
8a5fb4c9 402 */
02be5561 403void rcu_init(void)
27b012e2
MD
404{
405 struct sigaction act;
406 int ret;
407
8a5fb4c9
MD
408 if (init_done)
409 return;
410 init_done = 1;
411
02be5561 412 act.sa_sigaction = sigrcu_handler;
dd052bd3 413 act.sa_flags = SA_SIGINFO | SA_RESTART;
c297c21c 414 sigemptyset(&act.sa_mask);
02be5561 415 ret = sigaction(SIGRCU, &act, NULL);
f69f195a
MD
416 if (ret) {
417 perror("Error in sigaction");
27b012e2
MD
418 exit(-1);
419 }
420}
421
02be5561 422void rcu_exit(void)
27b012e2
MD
423{
424 struct sigaction act;
425 int ret;
426
02be5561 427 ret = sigaction(SIGRCU, NULL, &act);
f69f195a
MD
428 if (ret) {
429 perror("Error in sigaction");
27b012e2
MD
430 exit(-1);
431 }
02be5561 432 assert(act.sa_sigaction == sigrcu_handler);
16aa9ee8 433 assert(cds_list_empty(&registry));
27b012e2 434}
5e77fc1f 435
fdf01eed 436#endif /* #ifdef RCU_SIGNAL */
5e77fc1f
PM
437
438#include "urcu-call-rcu-impl.h"
0376e7b2 439#include "urcu-defer-impl.h"
This page took 0.080796 seconds and 4 git commands to generate.