Fix: workqueue: struct urcu_work vs rcu_head mixup
[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 <assert.h>
29 #include <stdlib.h>
30 #include <stdint.h>
31 #include <string.h>
32 #include <errno.h>
33 #include <poll.h>
34 #include <sys/time.h>
35 #include <unistd.h>
36 #include <sched.h>
37
38 #include "compat-getcpu.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 #if 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 #if SCHED_SETAFFINITY_ARGS == 2
111 ret = sched_setaffinity(0, &mask);
112 #else
113 ret = sched_setaffinity(0, sizeof(mask), &mask);
114 #endif
115 /*
116 * EINVAL is fine: can be caused by hotunplugged CPUs, or by
117 * cpuset(7). This is why we should always retry if we detect
118 * migration.
119 */
120 if (ret && errno == EINVAL) {
121 ret = 0;
122 errno = 0;
123 }
124 return ret;
125 }
126 #else
127 static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue)
128 {
129 return 0;
130 }
131 #endif
132
133 static void futex_wait(int32_t *futex)
134 {
135 /* Read condition before read futex */
136 cmm_smp_mb();
137 if (uatomic_read(futex) != -1)
138 return;
139 while (futex_async(futex, FUTEX_WAIT, -1, NULL, NULL, 0)) {
140 switch (errno) {
141 case EWOULDBLOCK:
142 /* Value already changed. */
143 return;
144 case EINTR:
145 /* Retry if interrupted by signal. */
146 break; /* Get out of switch. */
147 default:
148 /* Unexpected error. */
149 urcu_die(errno);
150 }
151 }
152 }
153
154 static void futex_wake_up(int32_t *futex)
155 {
156 /* Write to condition before reading/writing futex */
157 cmm_smp_mb();
158 if (caa_unlikely(uatomic_read(futex) == -1)) {
159 uatomic_set(futex, 0);
160 if (futex_async(futex, FUTEX_WAKE, 1,
161 NULL, NULL, 0) < 0)
162 urcu_die(errno);
163 }
164 }
165
166 /* This is the code run by each worker thread. */
167
168 static void *workqueue_thread(void *arg)
169 {
170 unsigned long cbcount;
171 struct urcu_workqueue *workqueue = (struct urcu_workqueue *) arg;
172 int rt = !!(uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_RT);
173
174 if (set_thread_cpu_affinity(workqueue))
175 urcu_die(errno);
176
177 if (workqueue->initialize_worker_fct)
178 workqueue->initialize_worker_fct(workqueue, workqueue->priv);
179
180 if (!rt) {
181 uatomic_dec(&workqueue->futex);
182 /* Decrement futex before reading workqueue */
183 cmm_smp_mb();
184 }
185 for (;;) {
186 struct cds_wfcq_head cbs_tmp_head;
187 struct cds_wfcq_tail cbs_tmp_tail;
188 struct cds_wfcq_node *cbs, *cbs_tmp_n;
189 enum cds_wfcq_ret splice_ret;
190
191 if (set_thread_cpu_affinity(workqueue))
192 urcu_die(errno);
193
194 if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) {
195 /*
196 * Pause requested. Become quiescent: remove
197 * ourself from all global lists, and don't
198 * process any callback. The callback lists may
199 * still be non-empty though.
200 */
201 if (workqueue->worker_before_pause_fct)
202 workqueue->worker_before_pause_fct(workqueue, workqueue->priv);
203 cmm_smp_mb__before_uatomic_or();
204 uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSED);
205 while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) != 0)
206 (void) poll(NULL, 0, 1);
207 uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSED);
208 cmm_smp_mb__after_uatomic_and();
209 if (workqueue->worker_after_resume_fct)
210 workqueue->worker_after_resume_fct(workqueue, workqueue->priv);
211 }
212
213 cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail);
214 splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head,
215 &cbs_tmp_tail, &workqueue->cbs_head, &workqueue->cbs_tail);
216 assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK);
217 assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY);
218 if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) {
219 if (workqueue->grace_period_fct)
220 workqueue->grace_period_fct(workqueue, workqueue->priv);
221 cbcount = 0;
222 __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head,
223 &cbs_tmp_tail, cbs, cbs_tmp_n) {
224 struct urcu_work *uwp;
225
226 uwp = caa_container_of(cbs,
227 struct urcu_work, next);
228 uwp->func(uwp);
229 cbcount++;
230 }
231 uatomic_sub(&workqueue->qlen, cbcount);
232 }
233 if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_STOP)
234 break;
235 if (workqueue->worker_before_wait_fct)
236 workqueue->worker_before_wait_fct(workqueue, workqueue->priv);
237 if (!rt) {
238 if (cds_wfcq_empty(&workqueue->cbs_head,
239 &workqueue->cbs_tail)) {
240 futex_wait(&workqueue->futex);
241 (void) poll(NULL, 0, 10);
242 uatomic_dec(&workqueue->futex);
243 /*
244 * Decrement futex before reading
245 * urcu_work list.
246 */
247 cmm_smp_mb();
248 } else {
249 (void) poll(NULL, 0, 10);
250 }
251 } else {
252 (void) poll(NULL, 0, 10);
253 }
254 if (workqueue->worker_after_wake_up_fct)
255 workqueue->worker_after_wake_up_fct(workqueue, workqueue->priv);
256 }
257 if (!rt) {
258 /*
259 * Read urcu_work list before write futex.
260 */
261 cmm_smp_mb();
262 uatomic_set(&workqueue->futex, 0);
263 }
264 if (workqueue->finalize_worker_fct)
265 workqueue->finalize_worker_fct(workqueue, workqueue->priv);
266 return NULL;
267 }
268
269 struct urcu_workqueue *urcu_workqueue_create(unsigned long flags,
270 int cpu_affinity, void *priv,
271 void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv),
272 void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv),
273 void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv),
274 void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv),
275 void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv),
276 void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv),
277 void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv))
278 {
279 struct urcu_workqueue *workqueue;
280 int ret;
281
282 workqueue = malloc(sizeof(*workqueue));
283 if (workqueue == NULL)
284 urcu_die(errno);
285 memset(workqueue, '\0', sizeof(*workqueue));
286 cds_wfcq_init(&workqueue->cbs_head, &workqueue->cbs_tail);
287 workqueue->qlen = 0;
288 workqueue->futex = 0;
289 workqueue->flags = flags;
290 workqueue->priv = priv;
291 workqueue->grace_period_fct = grace_period_fct;
292 workqueue->initialize_worker_fct = initialize_worker_fct;
293 workqueue->finalize_worker_fct = finalize_worker_fct;
294 workqueue->worker_before_wait_fct = worker_before_wait_fct;
295 workqueue->worker_after_wake_up_fct = worker_after_wake_up_fct;
296 workqueue->worker_before_pause_fct = worker_before_pause_fct;
297 workqueue->worker_after_resume_fct = worker_after_resume_fct;
298 workqueue->cpu_affinity = cpu_affinity;
299 workqueue->loop_count = 0;
300 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
301 ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
302 if (ret) {
303 urcu_die(ret);
304 }
305 return workqueue;
306 }
307
308 static void wake_worker_thread(struct urcu_workqueue *workqueue)
309 {
310 if (!(_CMM_LOAD_SHARED(workqueue->flags) & URCU_WORKQUEUE_RT))
311 futex_wake_up(&workqueue->futex);
312 }
313
314 static int urcu_workqueue_destroy_worker(struct urcu_workqueue *workqueue)
315 {
316 int ret;
317 void *retval;
318
319 uatomic_or(&workqueue->flags, URCU_WORKQUEUE_STOP);
320 wake_worker_thread(workqueue);
321
322 ret = pthread_join(workqueue->tid, &retval);
323 if (ret) {
324 urcu_die(ret);
325 }
326 if (retval != NULL) {
327 urcu_die(EINVAL);
328 }
329 workqueue->flags &= ~URCU_WORKQUEUE_STOP;
330 workqueue->tid = 0;
331 return 0;
332 }
333
334 void urcu_workqueue_destroy(struct urcu_workqueue *workqueue)
335 {
336 if (workqueue == NULL) {
337 return;
338 }
339 if (urcu_workqueue_destroy_worker(workqueue)) {
340 urcu_die(errno);
341 }
342 assert(cds_wfcq_empty(&workqueue->cbs_head, &workqueue->cbs_tail));
343 free(workqueue);
344 }
345
346 void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue,
347 struct urcu_work *work,
348 void (*func)(struct urcu_work *work))
349 {
350 cds_wfcq_node_init(&work->next);
351 work->func = func;
352 cds_wfcq_enqueue(&workqueue->cbs_head, &workqueue->cbs_tail, &work->next);
353 uatomic_inc(&workqueue->qlen);
354 wake_worker_thread(workqueue);
355 }
356
357 static
358 void free_completion(struct urcu_ref *ref)
359 {
360 struct urcu_workqueue_completion *completion;
361
362 completion = caa_container_of(ref, struct urcu_workqueue_completion, ref);
363 free(completion);
364 }
365
366 static
367 void _urcu_workqueue_wait_complete(struct urcu_work *work)
368 {
369 struct urcu_workqueue_completion_work *completion_work;
370 struct urcu_workqueue_completion *completion;
371
372 completion_work = caa_container_of(work, struct urcu_workqueue_completion_work, work);
373 completion = completion_work->completion;
374 if (!uatomic_sub_return(&completion->barrier_count, 1))
375 futex_wake_up(&completion->futex);
376 urcu_ref_put(&completion->ref, free_completion);
377 free(completion_work);
378 }
379
380 struct urcu_workqueue_completion *urcu_workqueue_create_completion(void)
381 {
382 struct urcu_workqueue_completion *completion;
383
384 completion = calloc(sizeof(*completion), 1);
385 if (!completion)
386 urcu_die(errno);
387 urcu_ref_set(&completion->ref, 1);
388 completion->barrier_count = 0;
389 return completion;
390 }
391
392 void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion)
393 {
394 urcu_ref_put(&completion->ref, free_completion);
395 }
396
397 void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion)
398 {
399 /* Wait for them */
400 for (;;) {
401 uatomic_dec(&completion->futex);
402 /* Decrement futex before reading barrier_count */
403 cmm_smp_mb();
404 if (!uatomic_read(&completion->barrier_count))
405 break;
406 futex_wait(&completion->futex);
407 }
408 }
409
410 void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue,
411 struct urcu_workqueue_completion *completion)
412 {
413 struct urcu_workqueue_completion_work *work;
414
415 work = calloc(sizeof(*work), 1);
416 if (!work)
417 urcu_die(errno);
418 work->completion = completion;
419 urcu_ref_get(&completion->ref);
420 uatomic_inc(&completion->barrier_count);
421 urcu_workqueue_queue_work(workqueue, &work->work, _urcu_workqueue_wait_complete);
422 }
423
424 /*
425 * Wait for all in-flight work to complete execution.
426 */
427 void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue)
428 {
429 struct urcu_workqueue_completion *completion;
430
431 completion = urcu_workqueue_create_completion();
432 if (!completion)
433 urcu_die(ENOMEM);
434 urcu_workqueue_queue_completion(workqueue, completion);
435 urcu_workqueue_wait_completion(completion);
436 urcu_workqueue_destroy_completion(completion);
437 }
438
439 /* To be used in before fork handler. */
440 void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue)
441 {
442 uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSE);
443 cmm_smp_mb__after_uatomic_or();
444 wake_worker_thread(workqueue);
445
446 while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) == 0)
447 (void) poll(NULL, 0, 1);
448 }
449
450 /* To be used in after fork parent handler. */
451 void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue)
452 {
453 uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSE);
454 while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) != 0)
455 (void) poll(NULL, 0, 1);
456 }
457
458 void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue)
459 {
460 int ret;
461
462 /* Clear workqueue state from parent. */
463 workqueue->flags &= ~URCU_WORKQUEUE_PAUSED;
464 workqueue->flags &= ~URCU_WORKQUEUE_PAUSE;
465 workqueue->tid = 0;
466 ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
467 if (ret) {
468 urcu_die(ret);
469 }
470 }
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