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ccacf27f MD |
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> | |
ccacf27f MD |
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" | |
01477510 | 38 | #include <urcu/assert.h> |
6cd23d47 MD |
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> | |
ccacf27f MD |
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 | |
1b6fc173 MD |
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. | |
ccacf27f MD |
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 | */ | |
2388c075 | 95 | #ifdef HAVE_SCHED_SETAFFINITY |
ccacf27f MD |
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); | |
ccacf27f | 110 | ret = sched_setaffinity(0, sizeof(mask), &mask); |
0614a2e6 | 111 | |
ccacf27f MD |
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 | |
a142df4e | 124 | static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue __attribute__((unused))) |
ccacf27f MD |
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 | if (uatomic_read(futex) != -1) | |
135 | return; | |
136 | while (futex_async(futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { | |
137 | switch (errno) { | |
138 | case EWOULDBLOCK: | |
139 | /* Value already changed. */ | |
140 | return; | |
141 | case EINTR: | |
142 | /* Retry if interrupted by signal. */ | |
143 | break; /* Get out of switch. */ | |
144 | default: | |
145 | /* Unexpected error. */ | |
146 | urcu_die(errno); | |
147 | } | |
148 | } | |
149 | } | |
150 | ||
151 | static void futex_wake_up(int32_t *futex) | |
152 | { | |
153 | /* Write to condition before reading/writing futex */ | |
154 | cmm_smp_mb(); | |
155 | if (caa_unlikely(uatomic_read(futex) == -1)) { | |
156 | uatomic_set(futex, 0); | |
157 | if (futex_async(futex, FUTEX_WAKE, 1, | |
158 | NULL, NULL, 0) < 0) | |
159 | urcu_die(errno); | |
160 | } | |
161 | } | |
162 | ||
163 | /* This is the code run by each worker thread. */ | |
164 | ||
165 | static void *workqueue_thread(void *arg) | |
166 | { | |
167 | unsigned long cbcount; | |
168 | struct urcu_workqueue *workqueue = (struct urcu_workqueue *) arg; | |
169 | int rt = !!(uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_RT); | |
170 | ||
171 | if (set_thread_cpu_affinity(workqueue)) | |
172 | urcu_die(errno); | |
173 | ||
174 | if (workqueue->initialize_worker_fct) | |
175 | workqueue->initialize_worker_fct(workqueue, workqueue->priv); | |
176 | ||
177 | if (!rt) { | |
178 | uatomic_dec(&workqueue->futex); | |
179 | /* Decrement futex before reading workqueue */ | |
180 | cmm_smp_mb(); | |
181 | } | |
182 | for (;;) { | |
183 | struct cds_wfcq_head cbs_tmp_head; | |
184 | struct cds_wfcq_tail cbs_tmp_tail; | |
185 | struct cds_wfcq_node *cbs, *cbs_tmp_n; | |
186 | enum cds_wfcq_ret splice_ret; | |
187 | ||
188 | if (set_thread_cpu_affinity(workqueue)) | |
189 | urcu_die(errno); | |
190 | ||
191 | if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) { | |
192 | /* | |
193 | * Pause requested. Become quiescent: remove | |
194 | * ourself from all global lists, and don't | |
195 | * process any callback. The callback lists may | |
196 | * still be non-empty though. | |
197 | */ | |
198 | if (workqueue->worker_before_pause_fct) | |
199 | workqueue->worker_before_pause_fct(workqueue, workqueue->priv); | |
200 | cmm_smp_mb__before_uatomic_or(); | |
201 | uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSED); | |
202 | while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) != 0) | |
203 | (void) poll(NULL, 0, 1); | |
204 | uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSED); | |
205 | cmm_smp_mb__after_uatomic_and(); | |
206 | if (workqueue->worker_after_resume_fct) | |
207 | workqueue->worker_after_resume_fct(workqueue, workqueue->priv); | |
208 | } | |
209 | ||
210 | cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail); | |
211 | splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head, | |
212 | &cbs_tmp_tail, &workqueue->cbs_head, &workqueue->cbs_tail); | |
01477510 FD |
213 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK); |
214 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY); | |
ccacf27f MD |
215 | if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) { |
216 | if (workqueue->grace_period_fct) | |
217 | workqueue->grace_period_fct(workqueue, workqueue->priv); | |
218 | cbcount = 0; | |
219 | __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head, | |
220 | &cbs_tmp_tail, cbs, cbs_tmp_n) { | |
d25f25df | 221 | struct urcu_work *uwp; |
ccacf27f | 222 | |
d25f25df MD |
223 | uwp = caa_container_of(cbs, |
224 | struct urcu_work, next); | |
225 | uwp->func(uwp); | |
ccacf27f MD |
226 | cbcount++; |
227 | } | |
228 | uatomic_sub(&workqueue->qlen, cbcount); | |
229 | } | |
230 | if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_STOP) | |
231 | break; | |
232 | if (workqueue->worker_before_wait_fct) | |
233 | workqueue->worker_before_wait_fct(workqueue, workqueue->priv); | |
234 | if (!rt) { | |
235 | if (cds_wfcq_empty(&workqueue->cbs_head, | |
236 | &workqueue->cbs_tail)) { | |
237 | futex_wait(&workqueue->futex); | |
ccacf27f MD |
238 | uatomic_dec(&workqueue->futex); |
239 | /* | |
240 | * Decrement futex before reading | |
1b6fc173 | 241 | * urcu_work list. |
ccacf27f MD |
242 | */ |
243 | cmm_smp_mb(); | |
ccacf27f MD |
244 | } |
245 | } else { | |
5bbe95bb JG |
246 | if (cds_wfcq_empty(&workqueue->cbs_head, |
247 | &workqueue->cbs_tail)) { | |
248 | (void) poll(NULL, 0, 10); | |
249 | } | |
ccacf27f MD |
250 | } |
251 | if (workqueue->worker_after_wake_up_fct) | |
252 | workqueue->worker_after_wake_up_fct(workqueue, workqueue->priv); | |
253 | } | |
254 | if (!rt) { | |
255 | /* | |
1b6fc173 | 256 | * Read urcu_work list before write futex. |
ccacf27f MD |
257 | */ |
258 | cmm_smp_mb(); | |
259 | uatomic_set(&workqueue->futex, 0); | |
260 | } | |
261 | if (workqueue->finalize_worker_fct) | |
262 | workqueue->finalize_worker_fct(workqueue, workqueue->priv); | |
263 | return NULL; | |
264 | } | |
265 | ||
266 | struct urcu_workqueue *urcu_workqueue_create(unsigned long flags, | |
267 | int cpu_affinity, void *priv, | |
268 | void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv), | |
269 | void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), | |
270 | void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), | |
271 | void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv), | |
272 | void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv), | |
273 | void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv), | |
274 | void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv)) | |
275 | { | |
276 | struct urcu_workqueue *workqueue; | |
277 | int ret; | |
278 | ||
279 | workqueue = malloc(sizeof(*workqueue)); | |
280 | if (workqueue == NULL) | |
281 | urcu_die(errno); | |
282 | memset(workqueue, '\0', sizeof(*workqueue)); | |
283 | cds_wfcq_init(&workqueue->cbs_head, &workqueue->cbs_tail); | |
284 | workqueue->qlen = 0; | |
285 | workqueue->futex = 0; | |
286 | workqueue->flags = flags; | |
287 | workqueue->priv = priv; | |
288 | workqueue->grace_period_fct = grace_period_fct; | |
289 | workqueue->initialize_worker_fct = initialize_worker_fct; | |
290 | workqueue->finalize_worker_fct = finalize_worker_fct; | |
291 | workqueue->worker_before_wait_fct = worker_before_wait_fct; | |
292 | workqueue->worker_after_wake_up_fct = worker_after_wake_up_fct; | |
293 | workqueue->worker_before_pause_fct = worker_before_pause_fct; | |
294 | workqueue->worker_after_resume_fct = worker_after_resume_fct; | |
295 | workqueue->cpu_affinity = cpu_affinity; | |
296 | workqueue->loop_count = 0; | |
297 | cmm_smp_mb(); /* Structure initialized before pointer is planted. */ | |
298 | ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue); | |
299 | if (ret) { | |
300 | urcu_die(ret); | |
301 | } | |
302 | return workqueue; | |
303 | } | |
304 | ||
305 | static void wake_worker_thread(struct urcu_workqueue *workqueue) | |
306 | { | |
9db9edcc | 307 | if (!(_CMM_LOAD_SHARED(workqueue->flags) & URCU_WORKQUEUE_RT)) |
ccacf27f MD |
308 | futex_wake_up(&workqueue->futex); |
309 | } | |
310 | ||
311 | static int urcu_workqueue_destroy_worker(struct urcu_workqueue *workqueue) | |
312 | { | |
313 | int ret; | |
314 | void *retval; | |
315 | ||
316 | uatomic_or(&workqueue->flags, URCU_WORKQUEUE_STOP); | |
317 | wake_worker_thread(workqueue); | |
318 | ||
319 | ret = pthread_join(workqueue->tid, &retval); | |
320 | if (ret) { | |
321 | urcu_die(ret); | |
322 | } | |
323 | if (retval != NULL) { | |
324 | urcu_die(EINVAL); | |
325 | } | |
326 | workqueue->flags &= ~URCU_WORKQUEUE_STOP; | |
327 | workqueue->tid = 0; | |
328 | return 0; | |
329 | } | |
330 | ||
331 | void urcu_workqueue_destroy(struct urcu_workqueue *workqueue) | |
332 | { | |
333 | if (workqueue == NULL) { | |
334 | return; | |
335 | } | |
336 | if (urcu_workqueue_destroy_worker(workqueue)) { | |
337 | urcu_die(errno); | |
338 | } | |
01477510 | 339 | urcu_posix_assert(cds_wfcq_empty(&workqueue->cbs_head, &workqueue->cbs_tail)); |
ccacf27f MD |
340 | free(workqueue); |
341 | } | |
342 | ||
343 | void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue, | |
344 | struct urcu_work *work, | |
345 | void (*func)(struct urcu_work *work)) | |
346 | { | |
347 | cds_wfcq_node_init(&work->next); | |
348 | work->func = func; | |
349 | cds_wfcq_enqueue(&workqueue->cbs_head, &workqueue->cbs_tail, &work->next); | |
350 | uatomic_inc(&workqueue->qlen); | |
351 | wake_worker_thread(workqueue); | |
352 | } | |
353 | ||
354 | static | |
355 | void free_completion(struct urcu_ref *ref) | |
356 | { | |
357 | struct urcu_workqueue_completion *completion; | |
358 | ||
359 | completion = caa_container_of(ref, struct urcu_workqueue_completion, ref); | |
360 | free(completion); | |
361 | } | |
362 | ||
363 | static | |
364 | void _urcu_workqueue_wait_complete(struct urcu_work *work) | |
365 | { | |
366 | struct urcu_workqueue_completion_work *completion_work; | |
367 | struct urcu_workqueue_completion *completion; | |
368 | ||
369 | completion_work = caa_container_of(work, struct urcu_workqueue_completion_work, work); | |
370 | completion = completion_work->completion; | |
371 | if (!uatomic_sub_return(&completion->barrier_count, 1)) | |
372 | futex_wake_up(&completion->futex); | |
373 | urcu_ref_put(&completion->ref, free_completion); | |
374 | free(completion_work); | |
375 | } | |
376 | ||
377 | struct urcu_workqueue_completion *urcu_workqueue_create_completion(void) | |
378 | { | |
379 | struct urcu_workqueue_completion *completion; | |
380 | ||
381 | completion = calloc(sizeof(*completion), 1); | |
382 | if (!completion) | |
383 | urcu_die(errno); | |
384 | urcu_ref_set(&completion->ref, 1); | |
385 | completion->barrier_count = 0; | |
386 | return completion; | |
387 | } | |
388 | ||
389 | void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion) | |
390 | { | |
391 | urcu_ref_put(&completion->ref, free_completion); | |
392 | } | |
393 | ||
394 | void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion) | |
395 | { | |
396 | /* Wait for them */ | |
397 | for (;;) { | |
398 | uatomic_dec(&completion->futex); | |
399 | /* Decrement futex before reading barrier_count */ | |
400 | cmm_smp_mb(); | |
401 | if (!uatomic_read(&completion->barrier_count)) | |
402 | break; | |
403 | futex_wait(&completion->futex); | |
404 | } | |
405 | } | |
406 | ||
407 | void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue, | |
408 | struct urcu_workqueue_completion *completion) | |
409 | { | |
410 | struct urcu_workqueue_completion_work *work; | |
411 | ||
412 | work = calloc(sizeof(*work), 1); | |
413 | if (!work) | |
414 | urcu_die(errno); | |
415 | work->completion = completion; | |
416 | urcu_ref_get(&completion->ref); | |
417 | uatomic_inc(&completion->barrier_count); | |
418 | urcu_workqueue_queue_work(workqueue, &work->work, _urcu_workqueue_wait_complete); | |
419 | } | |
420 | ||
421 | /* | |
422 | * Wait for all in-flight work to complete execution. | |
423 | */ | |
424 | void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue) | |
425 | { | |
426 | struct urcu_workqueue_completion *completion; | |
427 | ||
428 | completion = urcu_workqueue_create_completion(); | |
429 | if (!completion) | |
430 | urcu_die(ENOMEM); | |
431 | urcu_workqueue_queue_completion(workqueue, completion); | |
432 | urcu_workqueue_wait_completion(completion); | |
433 | urcu_workqueue_destroy_completion(completion); | |
434 | } | |
435 | ||
436 | /* To be used in before fork handler. */ | |
437 | void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue) | |
438 | { | |
439 | uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSE); | |
440 | cmm_smp_mb__after_uatomic_or(); | |
441 | wake_worker_thread(workqueue); | |
442 | ||
443 | while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) == 0) | |
444 | (void) poll(NULL, 0, 1); | |
445 | } | |
446 | ||
447 | /* To be used in after fork parent handler. */ | |
448 | void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue) | |
449 | { | |
450 | uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSE); | |
451 | while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) != 0) | |
452 | (void) poll(NULL, 0, 1); | |
453 | } | |
454 | ||
455 | void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue) | |
456 | { | |
457 | int ret; | |
458 | ||
459 | /* Clear workqueue state from parent. */ | |
460 | workqueue->flags &= ~URCU_WORKQUEUE_PAUSED; | |
461 | workqueue->flags &= ~URCU_WORKQUEUE_PAUSE; | |
462 | workqueue->tid = 0; | |
463 | ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue); | |
464 | if (ret) { | |
465 | urcu_die(ret); | |
466 | } | |
467 | } |