Fix: call_rcu: teardown default call_rcu worker on application exit
[urcu.git] / src / workqueue.c
1 /*
2 * workqueue.c
3 *
4 * Userspace RCU library - Userspace workqeues
5 *
6 * Copyright (c) 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com>
7 * Copyright (c) 2017 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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
24 #define _LGPL_SOURCE
25 #include <stdio.h>
26 #include <pthread.h>
27 #include <signal.h>
28 #include <stdlib.h>
29 #include <stdint.h>
30 #include <string.h>
31 #include <errno.h>
32 #include <poll.h>
33 #include <sys/time.h>
34 #include <unistd.h>
35 #include <sched.h>
36
37 #include "compat-getcpu.h"
38 #include <urcu/assert.h>
39 #include <urcu/wfcqueue.h>
40 #include <urcu/pointer.h>
41 #include <urcu/list.h>
42 #include <urcu/futex.h>
43 #include <urcu/tls-compat.h>
44 #include <urcu/ref.h>
45 #include "urcu-die.h"
46
47 #include "workqueue.h"
48
49 #define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */
50 #define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1)
51
52 /* Data structure that identifies a workqueue. */
53
54 struct urcu_workqueue {
55 /*
56 * We do not align head on a different cache-line than tail
57 * mainly because workqueue threads use batching ("splice") to
58 * get an entire list of callbacks, which effectively empties
59 * the queue, and requires to touch the tail anyway.
60 */
61 struct cds_wfcq_tail cbs_tail;
62 struct cds_wfcq_head cbs_head;
63 unsigned long flags;
64 int32_t futex;
65 unsigned long qlen; /* maintained for debugging. */
66 pthread_t tid;
67 int cpu_affinity;
68 unsigned long loop_count;
69 void *priv;
70 void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv);
71 void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv);
72 void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv);
73 void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv);
74 void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv);
75 void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv);
76 void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv);
77 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
78
79 struct urcu_workqueue_completion {
80 int barrier_count;
81 int32_t futex;
82 struct urcu_ref ref;
83 };
84
85 struct urcu_workqueue_completion_work {
86 struct urcu_work work;
87 struct urcu_workqueue_completion *completion;
88 };
89
90 /*
91 * Periodically retry setting CPU affinity if we migrate.
92 * Losing affinity can be caused by CPU hotunplug/hotplug, or by
93 * cpuset(7).
94 */
95 #ifdef HAVE_SCHED_SETAFFINITY
96 static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue)
97 {
98 cpu_set_t mask;
99 int ret;
100
101 if (workqueue->cpu_affinity < 0)
102 return 0;
103 if (++workqueue->loop_count & SET_AFFINITY_CHECK_PERIOD_MASK)
104 return 0;
105 if (urcu_sched_getcpu() == workqueue->cpu_affinity)
106 return 0;
107
108 CPU_ZERO(&mask);
109 CPU_SET(workqueue->cpu_affinity, &mask);
110 ret = sched_setaffinity(0, sizeof(mask), &mask);
111
112 /*
113 * EINVAL is fine: can be caused by hotunplugged CPUs, or by
114 * cpuset(7). This is why we should always retry if we detect
115 * migration.
116 */
117 if (ret && errno == EINVAL) {
118 ret = 0;
119 errno = 0;
120 }
121 return ret;
122 }
123 #else
124 static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue __attribute__((unused)))
125 {
126 return 0;
127 }
128 #endif
129
130 static void futex_wait(int32_t *futex)
131 {
132 /* Read condition before read futex */
133 cmm_smp_mb();
134 while (uatomic_read(futex) == -1) {
135 if (!futex_async(futex, FUTEX_WAIT, -1, NULL, NULL, 0)) {
136 /*
137 * Prior queued wakeups queued by unrelated code
138 * using the same address can cause futex wait to
139 * return 0 even through the futex value is still
140 * -1 (spurious wakeups). Check the value again
141 * in user-space to validate whether it really
142 * differs from -1.
143 */
144 continue;
145 }
146 switch (errno) {
147 case EAGAIN:
148 /* Value already changed. */
149 return;
150 case EINTR:
151 /* Retry if interrupted by signal. */
152 break; /* Get out of switch. Check again. */
153 default:
154 /* Unexpected error. */
155 urcu_die(errno);
156 }
157 }
158 }
159
160 static void futex_wake_up(int32_t *futex)
161 {
162 /* Write to condition before reading/writing futex */
163 cmm_smp_mb();
164 if (caa_unlikely(uatomic_read(futex) == -1)) {
165 uatomic_set(futex, 0);
166 if (futex_async(futex, FUTEX_WAKE, 1,
167 NULL, NULL, 0) < 0)
168 urcu_die(errno);
169 }
170 }
171
172 /* This is the code run by each worker thread. */
173
174 static void *workqueue_thread(void *arg)
175 {
176 unsigned long cbcount;
177 struct urcu_workqueue *workqueue = (struct urcu_workqueue *) arg;
178 int rt = !!(uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_RT);
179
180 if (set_thread_cpu_affinity(workqueue))
181 urcu_die(errno);
182
183 if (workqueue->initialize_worker_fct)
184 workqueue->initialize_worker_fct(workqueue, workqueue->priv);
185
186 if (!rt) {
187 uatomic_dec(&workqueue->futex);
188 /* Decrement futex before reading workqueue */
189 cmm_smp_mb();
190 }
191 for (;;) {
192 struct cds_wfcq_head cbs_tmp_head;
193 struct cds_wfcq_tail cbs_tmp_tail;
194 struct cds_wfcq_node *cbs, *cbs_tmp_n;
195 enum cds_wfcq_ret splice_ret;
196
197 if (set_thread_cpu_affinity(workqueue))
198 urcu_die(errno);
199
200 if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) {
201 /*
202 * Pause requested. Become quiescent: remove
203 * ourself from all global lists, and don't
204 * process any callback. The callback lists may
205 * still be non-empty though.
206 */
207 if (workqueue->worker_before_pause_fct)
208 workqueue->worker_before_pause_fct(workqueue, workqueue->priv);
209 cmm_smp_mb__before_uatomic_or();
210 uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSED);
211 while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) != 0)
212 (void) poll(NULL, 0, 1);
213 uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSED);
214 cmm_smp_mb__after_uatomic_and();
215 if (workqueue->worker_after_resume_fct)
216 workqueue->worker_after_resume_fct(workqueue, workqueue->priv);
217 }
218
219 cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
220 splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head,
221 &cbs_tmp_tail, &workqueue->cbs_head, &workqueue->cbs_tail);
222 urcu_posix_assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK);
223 urcu_posix_assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY);
224 if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) {
225 if (workqueue->grace_period_fct)
226 workqueue->grace_period_fct(workqueue, workqueue->priv);
227 cbcount = 0;
228 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head,
229 &cbs_tmp_tail, cbs, cbs_tmp_n) {
230 struct urcu_work *uwp;
231
232 uwp = caa_container_of(cbs,
233 struct urcu_work, next);
234 uwp->func(uwp);
235 cbcount++;
236 }
237 uatomic_sub(&workqueue->qlen, cbcount);
238 }
239 if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_STOP)
240 break;
241 if (workqueue->worker_before_wait_fct)
242 workqueue->worker_before_wait_fct(workqueue, workqueue->priv);
243 if (!rt) {
244 if (cds_wfcq_empty(&workqueue->cbs_head,
245 &workqueue->cbs_tail)) {
246 futex_wait(&workqueue->futex);
247 uatomic_dec(&workqueue->futex);
248 /*
249 * Decrement futex before reading
250 * urcu_work list.
251 */
252 cmm_smp_mb();
253 }
254 } else {
255 if (cds_wfcq_empty(&workqueue->cbs_head,
256 &workqueue->cbs_tail)) {
257 (void) poll(NULL, 0, 10);
258 }
259 }
260 if (workqueue->worker_after_wake_up_fct)
261 workqueue->worker_after_wake_up_fct(workqueue, workqueue->priv);
262 }
263 if (!rt) {
264 /*
265 * Read urcu_work list before write futex.
266 */
267 cmm_smp_mb();
268 uatomic_set(&workqueue->futex, 0);
269 }
270 if (workqueue->finalize_worker_fct)
271 workqueue->finalize_worker_fct(workqueue, workqueue->priv);
272 return NULL;
273 }
274
275 struct urcu_workqueue *urcu_workqueue_create(unsigned long flags,
276 int cpu_affinity, void *priv,
277 void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv),
278 void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv),
279 void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv),
280 void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv),
281 void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv),
282 void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv),
283 void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv))
284 {
285 struct urcu_workqueue *workqueue;
286 int ret;
287 sigset_t newmask, oldmask;
288
289 workqueue = malloc(sizeof(*workqueue));
290 if (workqueue == NULL)
291 urcu_die(errno);
292 memset(workqueue, '\0', sizeof(*workqueue));
293 cds_wfcq_init(&workqueue->cbs_head, &workqueue->cbs_tail);
294 workqueue->qlen = 0;
295 workqueue->futex = 0;
296 workqueue->flags = flags;
297 workqueue->priv = priv;
298 workqueue->grace_period_fct = grace_period_fct;
299 workqueue->initialize_worker_fct = initialize_worker_fct;
300 workqueue->finalize_worker_fct = finalize_worker_fct;
301 workqueue->worker_before_wait_fct = worker_before_wait_fct;
302 workqueue->worker_after_wake_up_fct = worker_after_wake_up_fct;
303 workqueue->worker_before_pause_fct = worker_before_pause_fct;
304 workqueue->worker_after_resume_fct = worker_after_resume_fct;
305 workqueue->cpu_affinity = cpu_affinity;
306 workqueue->loop_count = 0;
307 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
308
309 ret = sigfillset(&newmask);
310 urcu_posix_assert(!ret);
311 ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
312 urcu_posix_assert(!ret);
313
314 ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
315 if (ret) {
316 urcu_die(ret);
317 }
318
319 ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
320 urcu_posix_assert(!ret);
321
322 return workqueue;
323 }
324
325 static void wake_worker_thread(struct urcu_workqueue *workqueue)
326 {
327 if (!(_CMM_LOAD_SHARED(workqueue->flags) & URCU_WORKQUEUE_RT))
328 futex_wake_up(&workqueue->futex);
329 }
330
331 static int urcu_workqueue_destroy_worker(struct urcu_workqueue *workqueue)
332 {
333 int ret;
334 void *retval;
335
336 uatomic_or(&workqueue->flags, URCU_WORKQUEUE_STOP);
337 wake_worker_thread(workqueue);
338
339 ret = pthread_join(workqueue->tid, &retval);
340 if (ret) {
341 urcu_die(ret);
342 }
343 if (retval != NULL) {
344 urcu_die(EINVAL);
345 }
346 workqueue->flags &= ~URCU_WORKQUEUE_STOP;
347 workqueue->tid = 0;
348 return 0;
349 }
350
351 void urcu_workqueue_destroy(struct urcu_workqueue *workqueue)
352 {
353 if (workqueue == NULL) {
354 return;
355 }
356 if (urcu_workqueue_destroy_worker(workqueue)) {
357 urcu_die(errno);
358 }
359 urcu_posix_assert(cds_wfcq_empty(&workqueue->cbs_head, &workqueue->cbs_tail));
360 free(workqueue);
361 }
362
363 void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue,
364 struct urcu_work *work,
365 void (*func)(struct urcu_work *work))
366 {
367 cds_wfcq_node_init(&work->next);
368 work->func = func;
369 cds_wfcq_enqueue(&workqueue->cbs_head, &workqueue->cbs_tail, &work->next);
370 uatomic_inc(&workqueue->qlen);
371 wake_worker_thread(workqueue);
372 }
373
374 static
375 void free_completion(struct urcu_ref *ref)
376 {
377 struct urcu_workqueue_completion *completion;
378
379 completion = caa_container_of(ref, struct urcu_workqueue_completion, ref);
380 free(completion);
381 }
382
383 static
384 void _urcu_workqueue_wait_complete(struct urcu_work *work)
385 {
386 struct urcu_workqueue_completion_work *completion_work;
387 struct urcu_workqueue_completion *completion;
388
389 completion_work = caa_container_of(work, struct urcu_workqueue_completion_work, work);
390 completion = completion_work->completion;
391 if (!uatomic_sub_return(&completion->barrier_count, 1))
392 futex_wake_up(&completion->futex);
393 urcu_ref_put(&completion->ref, free_completion);
394 free(completion_work);
395 }
396
397 struct urcu_workqueue_completion *urcu_workqueue_create_completion(void)
398 {
399 struct urcu_workqueue_completion *completion;
400
401 completion = calloc(sizeof(*completion), 1);
402 if (!completion)
403 urcu_die(errno);
404 urcu_ref_set(&completion->ref, 1);
405 completion->barrier_count = 0;
406 return completion;
407 }
408
409 void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion)
410 {
411 urcu_ref_put(&completion->ref, free_completion);
412 }
413
414 void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion)
415 {
416 /* Wait for them */
417 for (;;) {
418 uatomic_dec(&completion->futex);
419 /* Decrement futex before reading barrier_count */
420 cmm_smp_mb();
421 if (!uatomic_read(&completion->barrier_count))
422 break;
423 futex_wait(&completion->futex);
424 }
425 }
426
427 void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue,
428 struct urcu_workqueue_completion *completion)
429 {
430 struct urcu_workqueue_completion_work *work;
431
432 work = calloc(sizeof(*work), 1);
433 if (!work)
434 urcu_die(errno);
435 work->completion = completion;
436 urcu_ref_get(&completion->ref);
437 uatomic_inc(&completion->barrier_count);
438 urcu_workqueue_queue_work(workqueue, &work->work, _urcu_workqueue_wait_complete);
439 }
440
441 /*
442 * Wait for all in-flight work to complete execution.
443 */
444 void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue)
445 {
446 struct urcu_workqueue_completion *completion;
447
448 completion = urcu_workqueue_create_completion();
449 if (!completion)
450 urcu_die(ENOMEM);
451 urcu_workqueue_queue_completion(workqueue, completion);
452 urcu_workqueue_wait_completion(completion);
453 urcu_workqueue_destroy_completion(completion);
454 }
455
456 /* To be used in before fork handler. */
457 void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue)
458 {
459 uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSE);
460 cmm_smp_mb__after_uatomic_or();
461 wake_worker_thread(workqueue);
462
463 while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) == 0)
464 (void) poll(NULL, 0, 1);
465 }
466
467 /* To be used in after fork parent handler. */
468 void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue)
469 {
470 uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSE);
471 while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) != 0)
472 (void) poll(NULL, 0, 1);
473 }
474
475 void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue)
476 {
477 int ret;
478 sigset_t newmask, oldmask;
479
480 /* Clear workqueue state from parent. */
481 workqueue->flags &= ~URCU_WORKQUEUE_PAUSED;
482 workqueue->flags &= ~URCU_WORKQUEUE_PAUSE;
483 workqueue->tid = 0;
484
485 ret = sigfillset(&newmask);
486 urcu_posix_assert(!ret);
487 ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
488 urcu_posix_assert(!ret);
489
490 ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
491 if (ret) {
492 urcu_die(ret);
493 }
494
495 ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
496 urcu_posix_assert(!ret);
497 }
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