Maintain list of struct call_rcu_data to keep valgrind happy.
[urcu.git] / urcu-call-rcu.c
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1/*
2 * urcu-call-rcu.c
3 *
4 * Userspace RCU library - batch memory reclamation with kernel API
5 *
6 * Copyright (c) 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com>
7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23#include <stdio.h>
24#include <pthread.h>
25#include <signal.h>
26#include <assert.h>
27#include <stdlib.h>
28#include <string.h>
29#include <errno.h>
30#include <poll.h>
31#include <sys/time.h>
32#include <syscall.h>
33#include <unistd.h>
34
35#include "config.h"
36#include "urcu/wfqueue.h"
37#include "urcu-call-rcu.h"
38#include "urcu-pointer.h"
3c24913f 39#include "urcu/list.h"
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40
41/* Data structure that identifies a call_rcu thread. */
42
43struct call_rcu_data {
44 struct cds_wfq_queue cbs;
45 unsigned long flags;
46 pthread_mutex_t mtx;
47 pthread_cond_t cond;
48 unsigned long qlen;
49 pthread_t tid;
3c24913f 50 struct cds_list_head list;
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51} __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
52
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53/*
54 * List of all call_rcu_data structures to keep valgrind happy.
55 * Protected by call_rcu_mutex.
56 */
57
58CDS_LIST_HEAD(call_rcu_data_list);
59
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60/* Link a thread using call_rcu() to its call_rcu thread. */
61
62static __thread struct call_rcu_data *thread_call_rcu_data;
63
64/* Guard call_rcu thread creation. */
65
66static pthread_mutex_t call_rcu_mutex = PTHREAD_MUTEX_INITIALIZER;
67
68/* If a given thread does not have its own call_rcu thread, this is default. */
69
70static struct call_rcu_data *default_call_rcu_data;
71
72extern void synchronize_rcu(void);
73
74/*
75 * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
76 * available, then we can have call_rcu threads assigned to individual
77 * CPUs rather than only to specific threads.
78 */
79
80#if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF)
81
82/*
83 * Pointer to array of pointers to per-CPU call_rcu_data structures
84 * and # CPUs.
85 */
86
87static struct call_rcu_data **per_cpu_call_rcu_data;
88static long maxcpus;
89
90/* Allocate the array if it has not already been allocated. */
91
92static void alloc_cpu_call_rcu_data(void)
93{
94 struct call_rcu_data **p;
95 static int warned = 0;
96
97 if (maxcpus != 0)
98 return;
99 maxcpus = sysconf(_SC_NPROCESSORS_CONF);
100 if (maxcpus <= 0) {
101 return;
102 }
103 p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data));
104 if (p != NULL) {
105 memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data));
106 per_cpu_call_rcu_data = p;
107 } else {
108 if (!warned) {
109 fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n");
110 }
111 warned = 1;
112 }
113}
114
115#else /* #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
116
117static const struct call_rcu_data **per_cpu_call_rcu_data = NULL;
118static const long maxcpus = -1;
119
120static void alloc_cpu_call_rcu_data(void)
121{
122}
123
124static int sched_getcpu(void)
125{
126 return -1;
127}
128
129#endif /* #else #if defined(HAVE_SCHED_GETCPU) && defined(HAVE_SYSCONF) */
130
131/* Acquire the specified pthread mutex. */
132
133static void call_rcu_lock(pthread_mutex_t *pmp)
134{
135 if (pthread_mutex_lock(pmp) != 0) {
136 perror("pthread_mutex_lock");
137 exit(-1);
138 }
139}
140
141/* Release the specified pthread mutex. */
142
143static void call_rcu_unlock(pthread_mutex_t *pmp)
144{
145 if (pthread_mutex_unlock(pmp) != 0) {
146 perror("pthread_mutex_unlock");
147 exit(-1);
148 }
149}
150
151/* This is the code run by each call_rcu thread. */
152
153static void *call_rcu_thread(void *arg)
154{
155 unsigned long cbcount;
156 struct cds_wfq_node *cbs;
157 struct cds_wfq_node **cbs_tail;
158 struct call_rcu_data *crdp = (struct call_rcu_data *)arg;
159 struct rcu_head *rhp;
160
161 thread_call_rcu_data = crdp;
162 for (;;) {
163 if (&crdp->cbs.head != _CMM_LOAD_SHARED(crdp->cbs.tail)) {
164 while ((cbs = _CMM_LOAD_SHARED(crdp->cbs.head)) == NULL)
165 poll(NULL, 0, 1);
166 _CMM_STORE_SHARED(crdp->cbs.head, NULL);
167 cbs_tail = (struct cds_wfq_node **)
168 uatomic_xchg(&crdp->cbs.tail, &crdp->cbs.head);
169 synchronize_rcu();
170 cbcount = 0;
171 do {
172 while (cbs->next == NULL &&
173 &cbs->next != cbs_tail)
174 poll(NULL, 0, 1);
175 if (cbs == &crdp->cbs.dummy) {
176 cbs = cbs->next;
177 continue;
178 }
179 rhp = (struct rcu_head *)cbs;
180 cbs = cbs->next;
181 rhp->func(rhp);
182 cbcount++;
183 } while (cbs != NULL);
184 uatomic_sub(&crdp->qlen, cbcount);
185 }
186 if (crdp->flags & URCU_CALL_RCU_RT)
187 poll(NULL, 0, 10);
188 else {
189 call_rcu_lock(&crdp->mtx);
190 _CMM_STORE_SHARED(crdp->flags,
191 crdp->flags & ~URCU_CALL_RCU_RUNNING);
192 if (&crdp->cbs.head ==
193 _CMM_LOAD_SHARED(crdp->cbs.tail) &&
194 pthread_cond_wait(&crdp->cond, &crdp->mtx) != 0) {
195 perror("pthread_cond_wait");
196 exit(-1);
197 }
198 _CMM_STORE_SHARED(crdp->flags,
199 crdp->flags | URCU_CALL_RCU_RUNNING);
200 poll(NULL, 0, 10);
201 call_rcu_unlock(&crdp->mtx);
202 }
203 }
204 return NULL; /* NOTREACHED */
205}
206
207/*
208 * Create both a call_rcu thread and the corresponding call_rcu_data
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209 * structure, linking the structure in as specified. Caller must hold
210 * call_rcu_mutex.
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211 */
212
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213static void call_rcu_data_init(struct call_rcu_data **crdpp,
214 unsigned long flags)
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215{
216 struct call_rcu_data *crdp;
217
218 crdp = malloc(sizeof(*crdp));
219 if (crdp == NULL) {
220 fprintf(stderr, "Out of memory.\n");
221 exit(-1);
222 }
223 memset(crdp, '\0', sizeof(*crdp));
224 cds_wfq_init(&crdp->cbs);
225 crdp->qlen = 0;
226 if (pthread_mutex_init(&crdp->mtx, NULL) != 0) {
227 perror("pthread_mutex_init");
228 exit(-1);
229 }
230 if (pthread_cond_init(&crdp->cond, NULL) != 0) {
231 perror("pthread_cond_init");
232 exit(-1);
233 }
234 crdp->flags = flags | URCU_CALL_RCU_RUNNING;
3c24913f 235 cds_list_add(&crdp->list, &call_rcu_data_list);
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236 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
237 *crdpp = crdp;
238 if (pthread_create(&crdp->tid, NULL, call_rcu_thread, crdp) != 0) {
239 perror("pthread_create");
240 exit(-1);
241 }
242}
243
244/*
245 * Return a pointer to the call_rcu_data structure for the specified
246 * CPU, returning NULL if there is none. We cannot automatically
247 * created it because the platform we are running on might not define
248 * sched_getcpu().
249 */
250
251struct call_rcu_data *get_cpu_call_rcu_data(int cpu)
252{
253 static int warned = 0;
254
255 if (per_cpu_call_rcu_data == NULL)
256 return NULL;
257 if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) {
258 fprintf(stderr, "[error] liburcu: get CPU # out of range\n");
259 warned = 1;
260 }
261 if (cpu < 0 || maxcpus <= cpu)
262 return NULL;
263 return per_cpu_call_rcu_data[cpu];
264}
265
266/*
267 * Return the tid corresponding to the call_rcu thread whose
268 * call_rcu_data structure is specified.
269 */
270
271pthread_t get_call_rcu_thread(struct call_rcu_data *crdp)
272{
273 return crdp->tid;
274}
275
276/*
277 * Create a call_rcu_data structure (with thread) and return a pointer.
278 */
279
3c24913f 280static struct call_rcu_data *__create_call_rcu_data(unsigned long flags)
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281{
282 struct call_rcu_data *crdp;
283
284 call_rcu_data_init(&crdp, flags);
285 return crdp;
286}
287
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288struct call_rcu_data *create_call_rcu_data(unsigned long flags)
289{
290 struct call_rcu_data *crdp;
291
292 call_rcu_lock(&call_rcu_mutex);
293 crdp = __create_call_rcu_data(flags);
294 call_rcu_unlock(&call_rcu_mutex);
295 return crdp;
296}
297
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298/*
299 * Set the specified CPU to use the specified call_rcu_data structure.
300 */
301
302int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp)
303{
304 int warned = 0;
305
306 call_rcu_lock(&call_rcu_mutex);
307 if (cpu < 0 || maxcpus <= cpu) {
308 if (!warned) {
309 fprintf(stderr, "[error] liburcu: set CPU # out of range\n");
310 warned = 1;
311 }
312 call_rcu_unlock(&call_rcu_mutex);
313 errno = EINVAL;
314 return -EINVAL;
315 }
316 alloc_cpu_call_rcu_data();
317 call_rcu_unlock(&call_rcu_mutex);
318 if (per_cpu_call_rcu_data == NULL) {
319 errno = ENOMEM;
320 return -ENOMEM;
321 }
322 per_cpu_call_rcu_data[cpu] = crdp;
323 return 0;
324}
325
326/*
327 * Return a pointer to the default call_rcu_data structure, creating
328 * one if need be. Because we never free call_rcu_data structures,
329 * we don't need to be in an RCU read-side critical section.
330 */
331
332struct call_rcu_data *get_default_call_rcu_data(void)
333{
334 if (default_call_rcu_data != NULL)
335 return rcu_dereference(default_call_rcu_data);
336 call_rcu_lock(&call_rcu_mutex);
337 if (default_call_rcu_data != NULL) {
338 call_rcu_unlock(&call_rcu_mutex);
339 return default_call_rcu_data;
340 }
341 call_rcu_data_init(&default_call_rcu_data, 0);
342 call_rcu_unlock(&call_rcu_mutex);
343 return default_call_rcu_data;
344}
345
346/*
347 * Return the call_rcu_data structure that applies to the currently
348 * running thread. Any call_rcu_data structure assigned specifically
349 * to this thread has first priority, followed by any call_rcu_data
350 * structure assigned to the CPU on which the thread is running,
351 * followed by the default call_rcu_data structure. If there is not
352 * yet a default call_rcu_data structure, one will be created.
353 */
354struct call_rcu_data *get_call_rcu_data(void)
355{
356 int curcpu;
357 static int warned = 0;
358
359 if (thread_call_rcu_data != NULL)
360 return thread_call_rcu_data;
361 if (maxcpus <= 0)
362 return get_default_call_rcu_data();
363 curcpu = sched_getcpu();
364 if (!warned && (curcpu < 0 || maxcpus <= curcpu)) {
365 fprintf(stderr, "[error] liburcu: gcrd CPU # out of range\n");
366 warned = 1;
367 }
368 if (curcpu >= 0 && maxcpus > curcpu &&
369 per_cpu_call_rcu_data != NULL &&
370 per_cpu_call_rcu_data[curcpu] != NULL)
371 return per_cpu_call_rcu_data[curcpu];
372 return get_default_call_rcu_data();
373}
374
375/*
376 * Return a pointer to this task's call_rcu_data if there is one.
377 */
378
379struct call_rcu_data *get_thread_call_rcu_data(void)
380{
381 return thread_call_rcu_data;
382}
383
384/*
385 * Set this task's call_rcu_data structure as specified, regardless
386 * of whether or not this task already had one. (This allows switching
387 * to and from real-time call_rcu threads, for example.)
388 */
389
390void set_thread_call_rcu_data(struct call_rcu_data *crdp)
391{
392 thread_call_rcu_data = crdp;
393}
394
395/*
396 * Create a separate call_rcu thread for each CPU. This does not
397 * replace a pre-existing call_rcu thread -- use the set_cpu_call_rcu_data()
398 * function if you want that behavior.
399 */
400
401int create_all_cpu_call_rcu_data(unsigned long flags)
402{
403 int i;
404 struct call_rcu_data *crdp;
405 int ret;
406
407 call_rcu_lock(&call_rcu_mutex);
408 alloc_cpu_call_rcu_data();
409 call_rcu_unlock(&call_rcu_mutex);
410 if (maxcpus <= 0) {
411 errno = EINVAL;
412 return -EINVAL;
413 }
414 if (per_cpu_call_rcu_data == NULL) {
415 errno = ENOMEM;
416 return -ENOMEM;
417 }
418 for (i = 0; i < maxcpus; i++) {
419 call_rcu_lock(&call_rcu_mutex);
420 if (get_cpu_call_rcu_data(i)) {
421 call_rcu_unlock(&call_rcu_mutex);
422 continue;
423 }
3c24913f 424 crdp = __create_call_rcu_data(flags);
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425 if (crdp == NULL) {
426 call_rcu_unlock(&call_rcu_mutex);
427 errno = ENOMEM;
428 return -ENOMEM;
429 }
430 call_rcu_unlock(&call_rcu_mutex);
431 if ((ret = set_cpu_call_rcu_data(i, crdp)) != 0) {
432 /* FIXME: Leaks crdp for now. */
433 return ret; /* Can happen on race. */
434 }
435 }
436 return 0;
437}
438
439/*
440 * Schedule a function to be invoked after a following grace period.
441 * This is the only function that must be called -- the others are
442 * only present to allow applications to tune their use of RCU for
443 * maximum performance.
444 *
445 * Note that unless a call_rcu thread has not already been created,
446 * the first invocation of call_rcu() will create one. So, if you
447 * need the first invocation of call_rcu() to be fast, make sure
448 * to create a call_rcu thread first. One way to accomplish this is
449 * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data().
450 */
451
452void call_rcu(struct rcu_head *head,
453 void (*func)(struct rcu_head *head))
454{
455 struct call_rcu_data *crdp;
456
457 cds_wfq_node_init(&head->next);
458 head->func = func;
459 crdp = get_call_rcu_data();
460 cds_wfq_enqueue(&crdp->cbs, &head->next);
461 uatomic_inc(&crdp->qlen);
462 if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RT)) {
463 call_rcu_lock(&crdp->mtx);
464 if (!(_CMM_LOAD_SHARED(crdp->flags) & URCU_CALL_RCU_RUNNING)) {
465 if (pthread_cond_signal(&crdp->cond) != 0) {
466 perror("pthread_cond_signal");
467 exit(-1);
468 }
469 }
470 call_rcu_unlock(&crdp->mtx);
471 }
472}
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