Commit | Line | Data |
---|---|---|
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 | { | |
80c34c2d MD |
132 | int ret; |
133 | ||
ccacf27f MD |
134 | /* Read condition before read futex */ |
135 | cmm_smp_mb(); | |
80c34c2d MD |
136 | while (uatomic_read(futex) == -1) { |
137 | if (!futex_async(futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { | |
138 | /* | |
139 | * Prior queued wakeups queued by unrelated code | |
140 | * using the same address can cause futex wait to | |
141 | * return 0 even through the futex value is still | |
142 | * -1 (spurious wakeups). Check the value again | |
143 | * in user-space to validate whether it really | |
144 | * differs from -1. | |
145 | */ | |
146 | continue; | |
147 | } | |
ccacf27f | 148 | switch (errno) { |
80c34c2d | 149 | case EAGAIN: |
ccacf27f MD |
150 | /* Value already changed. */ |
151 | return; | |
152 | case EINTR: | |
153 | /* Retry if interrupted by signal. */ | |
80c34c2d | 154 | break; /* Get out of switch. Check again. */ |
ccacf27f MD |
155 | default: |
156 | /* Unexpected error. */ | |
157 | urcu_die(errno); | |
158 | } | |
159 | } | |
160 | } | |
161 | ||
162 | static void futex_wake_up(int32_t *futex) | |
163 | { | |
164 | /* Write to condition before reading/writing futex */ | |
165 | cmm_smp_mb(); | |
166 | if (caa_unlikely(uatomic_read(futex) == -1)) { | |
167 | uatomic_set(futex, 0); | |
168 | if (futex_async(futex, FUTEX_WAKE, 1, | |
169 | NULL, NULL, 0) < 0) | |
170 | urcu_die(errno); | |
171 | } | |
172 | } | |
173 | ||
174 | /* This is the code run by each worker thread. */ | |
175 | ||
176 | static void *workqueue_thread(void *arg) | |
177 | { | |
178 | unsigned long cbcount; | |
179 | struct urcu_workqueue *workqueue = (struct urcu_workqueue *) arg; | |
180 | int rt = !!(uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_RT); | |
181 | ||
182 | if (set_thread_cpu_affinity(workqueue)) | |
183 | urcu_die(errno); | |
184 | ||
185 | if (workqueue->initialize_worker_fct) | |
186 | workqueue->initialize_worker_fct(workqueue, workqueue->priv); | |
187 | ||
188 | if (!rt) { | |
189 | uatomic_dec(&workqueue->futex); | |
190 | /* Decrement futex before reading workqueue */ | |
191 | cmm_smp_mb(); | |
192 | } | |
193 | for (;;) { | |
194 | struct cds_wfcq_head cbs_tmp_head; | |
195 | struct cds_wfcq_tail cbs_tmp_tail; | |
196 | struct cds_wfcq_node *cbs, *cbs_tmp_n; | |
197 | enum cds_wfcq_ret splice_ret; | |
198 | ||
199 | if (set_thread_cpu_affinity(workqueue)) | |
200 | urcu_die(errno); | |
201 | ||
202 | if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) { | |
203 | /* | |
204 | * Pause requested. Become quiescent: remove | |
205 | * ourself from all global lists, and don't | |
206 | * process any callback. The callback lists may | |
207 | * still be non-empty though. | |
208 | */ | |
209 | if (workqueue->worker_before_pause_fct) | |
210 | workqueue->worker_before_pause_fct(workqueue, workqueue->priv); | |
211 | cmm_smp_mb__before_uatomic_or(); | |
212 | uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSED); | |
213 | while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) != 0) | |
214 | (void) poll(NULL, 0, 1); | |
215 | uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSED); | |
216 | cmm_smp_mb__after_uatomic_and(); | |
217 | if (workqueue->worker_after_resume_fct) | |
218 | workqueue->worker_after_resume_fct(workqueue, workqueue->priv); | |
219 | } | |
220 | ||
221 | cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail); | |
222 | splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head, | |
223 | &cbs_tmp_tail, &workqueue->cbs_head, &workqueue->cbs_tail); | |
01477510 FD |
224 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK); |
225 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY); | |
ccacf27f MD |
226 | if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) { |
227 | if (workqueue->grace_period_fct) | |
228 | workqueue->grace_period_fct(workqueue, workqueue->priv); | |
229 | cbcount = 0; | |
230 | __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head, | |
231 | &cbs_tmp_tail, cbs, cbs_tmp_n) { | |
d25f25df | 232 | struct urcu_work *uwp; |
ccacf27f | 233 | |
d25f25df MD |
234 | uwp = caa_container_of(cbs, |
235 | struct urcu_work, next); | |
236 | uwp->func(uwp); | |
ccacf27f MD |
237 | cbcount++; |
238 | } | |
239 | uatomic_sub(&workqueue->qlen, cbcount); | |
240 | } | |
241 | if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_STOP) | |
242 | break; | |
243 | if (workqueue->worker_before_wait_fct) | |
244 | workqueue->worker_before_wait_fct(workqueue, workqueue->priv); | |
245 | if (!rt) { | |
246 | if (cds_wfcq_empty(&workqueue->cbs_head, | |
247 | &workqueue->cbs_tail)) { | |
248 | futex_wait(&workqueue->futex); | |
ccacf27f MD |
249 | uatomic_dec(&workqueue->futex); |
250 | /* | |
251 | * Decrement futex before reading | |
1b6fc173 | 252 | * urcu_work list. |
ccacf27f MD |
253 | */ |
254 | cmm_smp_mb(); | |
ccacf27f MD |
255 | } |
256 | } else { | |
5bbe95bb JG |
257 | if (cds_wfcq_empty(&workqueue->cbs_head, |
258 | &workqueue->cbs_tail)) { | |
259 | (void) poll(NULL, 0, 10); | |
260 | } | |
ccacf27f MD |
261 | } |
262 | if (workqueue->worker_after_wake_up_fct) | |
263 | workqueue->worker_after_wake_up_fct(workqueue, workqueue->priv); | |
264 | } | |
265 | if (!rt) { | |
266 | /* | |
1b6fc173 | 267 | * Read urcu_work list before write futex. |
ccacf27f MD |
268 | */ |
269 | cmm_smp_mb(); | |
270 | uatomic_set(&workqueue->futex, 0); | |
271 | } | |
272 | if (workqueue->finalize_worker_fct) | |
273 | workqueue->finalize_worker_fct(workqueue, workqueue->priv); | |
274 | return NULL; | |
275 | } | |
276 | ||
277 | struct urcu_workqueue *urcu_workqueue_create(unsigned long flags, | |
278 | int cpu_affinity, void *priv, | |
279 | void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv), | |
280 | void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), | |
281 | void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), | |
282 | void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv), | |
283 | void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv), | |
284 | void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv), | |
285 | void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv)) | |
286 | { | |
287 | struct urcu_workqueue *workqueue; | |
288 | int ret; | |
289 | ||
290 | workqueue = malloc(sizeof(*workqueue)); | |
291 | if (workqueue == NULL) | |
292 | urcu_die(errno); | |
293 | memset(workqueue, '\0', sizeof(*workqueue)); | |
294 | cds_wfcq_init(&workqueue->cbs_head, &workqueue->cbs_tail); | |
295 | workqueue->qlen = 0; | |
296 | workqueue->futex = 0; | |
297 | workqueue->flags = flags; | |
298 | workqueue->priv = priv; | |
299 | workqueue->grace_period_fct = grace_period_fct; | |
300 | workqueue->initialize_worker_fct = initialize_worker_fct; | |
301 | workqueue->finalize_worker_fct = finalize_worker_fct; | |
302 | workqueue->worker_before_wait_fct = worker_before_wait_fct; | |
303 | workqueue->worker_after_wake_up_fct = worker_after_wake_up_fct; | |
304 | workqueue->worker_before_pause_fct = worker_before_pause_fct; | |
305 | workqueue->worker_after_resume_fct = worker_after_resume_fct; | |
306 | workqueue->cpu_affinity = cpu_affinity; | |
307 | workqueue->loop_count = 0; | |
308 | cmm_smp_mb(); /* Structure initialized before pointer is planted. */ | |
309 | ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue); | |
310 | if (ret) { | |
311 | urcu_die(ret); | |
312 | } | |
313 | return workqueue; | |
314 | } | |
315 | ||
316 | static void wake_worker_thread(struct urcu_workqueue *workqueue) | |
317 | { | |
9db9edcc | 318 | if (!(_CMM_LOAD_SHARED(workqueue->flags) & URCU_WORKQUEUE_RT)) |
ccacf27f MD |
319 | futex_wake_up(&workqueue->futex); |
320 | } | |
321 | ||
322 | static int urcu_workqueue_destroy_worker(struct urcu_workqueue *workqueue) | |
323 | { | |
324 | int ret; | |
325 | void *retval; | |
326 | ||
327 | uatomic_or(&workqueue->flags, URCU_WORKQUEUE_STOP); | |
328 | wake_worker_thread(workqueue); | |
329 | ||
330 | ret = pthread_join(workqueue->tid, &retval); | |
331 | if (ret) { | |
332 | urcu_die(ret); | |
333 | } | |
334 | if (retval != NULL) { | |
335 | urcu_die(EINVAL); | |
336 | } | |
337 | workqueue->flags &= ~URCU_WORKQUEUE_STOP; | |
338 | workqueue->tid = 0; | |
339 | return 0; | |
340 | } | |
341 | ||
342 | void urcu_workqueue_destroy(struct urcu_workqueue *workqueue) | |
343 | { | |
344 | if (workqueue == NULL) { | |
345 | return; | |
346 | } | |
347 | if (urcu_workqueue_destroy_worker(workqueue)) { | |
348 | urcu_die(errno); | |
349 | } | |
01477510 | 350 | urcu_posix_assert(cds_wfcq_empty(&workqueue->cbs_head, &workqueue->cbs_tail)); |
ccacf27f MD |
351 | free(workqueue); |
352 | } | |
353 | ||
354 | void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue, | |
355 | struct urcu_work *work, | |
356 | void (*func)(struct urcu_work *work)) | |
357 | { | |
358 | cds_wfcq_node_init(&work->next); | |
359 | work->func = func; | |
360 | cds_wfcq_enqueue(&workqueue->cbs_head, &workqueue->cbs_tail, &work->next); | |
361 | uatomic_inc(&workqueue->qlen); | |
362 | wake_worker_thread(workqueue); | |
363 | } | |
364 | ||
365 | static | |
366 | void free_completion(struct urcu_ref *ref) | |
367 | { | |
368 | struct urcu_workqueue_completion *completion; | |
369 | ||
370 | completion = caa_container_of(ref, struct urcu_workqueue_completion, ref); | |
371 | free(completion); | |
372 | } | |
373 | ||
374 | static | |
375 | void _urcu_workqueue_wait_complete(struct urcu_work *work) | |
376 | { | |
377 | struct urcu_workqueue_completion_work *completion_work; | |
378 | struct urcu_workqueue_completion *completion; | |
379 | ||
380 | completion_work = caa_container_of(work, struct urcu_workqueue_completion_work, work); | |
381 | completion = completion_work->completion; | |
382 | if (!uatomic_sub_return(&completion->barrier_count, 1)) | |
383 | futex_wake_up(&completion->futex); | |
384 | urcu_ref_put(&completion->ref, free_completion); | |
385 | free(completion_work); | |
386 | } | |
387 | ||
388 | struct urcu_workqueue_completion *urcu_workqueue_create_completion(void) | |
389 | { | |
390 | struct urcu_workqueue_completion *completion; | |
391 | ||
392 | completion = calloc(sizeof(*completion), 1); | |
393 | if (!completion) | |
394 | urcu_die(errno); | |
395 | urcu_ref_set(&completion->ref, 1); | |
396 | completion->barrier_count = 0; | |
397 | return completion; | |
398 | } | |
399 | ||
400 | void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion) | |
401 | { | |
402 | urcu_ref_put(&completion->ref, free_completion); | |
403 | } | |
404 | ||
405 | void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion) | |
406 | { | |
407 | /* Wait for them */ | |
408 | for (;;) { | |
409 | uatomic_dec(&completion->futex); | |
410 | /* Decrement futex before reading barrier_count */ | |
411 | cmm_smp_mb(); | |
412 | if (!uatomic_read(&completion->barrier_count)) | |
413 | break; | |
414 | futex_wait(&completion->futex); | |
415 | } | |
416 | } | |
417 | ||
418 | void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue, | |
419 | struct urcu_workqueue_completion *completion) | |
420 | { | |
421 | struct urcu_workqueue_completion_work *work; | |
422 | ||
423 | work = calloc(sizeof(*work), 1); | |
424 | if (!work) | |
425 | urcu_die(errno); | |
426 | work->completion = completion; | |
427 | urcu_ref_get(&completion->ref); | |
428 | uatomic_inc(&completion->barrier_count); | |
429 | urcu_workqueue_queue_work(workqueue, &work->work, _urcu_workqueue_wait_complete); | |
430 | } | |
431 | ||
432 | /* | |
433 | * Wait for all in-flight work to complete execution. | |
434 | */ | |
435 | void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue) | |
436 | { | |
437 | struct urcu_workqueue_completion *completion; | |
438 | ||
439 | completion = urcu_workqueue_create_completion(); | |
440 | if (!completion) | |
441 | urcu_die(ENOMEM); | |
442 | urcu_workqueue_queue_completion(workqueue, completion); | |
443 | urcu_workqueue_wait_completion(completion); | |
444 | urcu_workqueue_destroy_completion(completion); | |
445 | } | |
446 | ||
447 | /* To be used in before fork handler. */ | |
448 | void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue) | |
449 | { | |
450 | uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSE); | |
451 | cmm_smp_mb__after_uatomic_or(); | |
452 | wake_worker_thread(workqueue); | |
453 | ||
454 | while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) == 0) | |
455 | (void) poll(NULL, 0, 1); | |
456 | } | |
457 | ||
458 | /* To be used in after fork parent handler. */ | |
459 | void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue) | |
460 | { | |
461 | uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSE); | |
462 | while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) != 0) | |
463 | (void) poll(NULL, 0, 1); | |
464 | } | |
465 | ||
466 | void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue) | |
467 | { | |
468 | int ret; | |
469 | ||
470 | /* Clear workqueue state from parent. */ | |
471 | workqueue->flags &= ~URCU_WORKQUEUE_PAUSED; | |
472 | workqueue->flags &= ~URCU_WORKQUEUE_PAUSE; | |
473 | workqueue->tid = 0; | |
474 | ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue); | |
475 | if (ret) { | |
476 | urcu_die(ret); | |
477 | } | |
478 | } |