Commit | Line | Data |
---|---|---|
acdb82a2 MJ |
1 | // SPDX-FileCopyrightText: 2010 Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
2 | // SPDX-FileCopyrightText: 2017 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
3 | // | |
4 | // SPDX-License-Identifier: LGPL-2.1-or-later | |
5 | ||
ccacf27f | 6 | /* |
ccacf27f | 7 | * Userspace RCU library - Userspace workqeues |
ccacf27f MD |
8 | */ |
9 | ||
10 | #define _LGPL_SOURCE | |
11 | #include <stdio.h> | |
12 | #include <pthread.h> | |
13 | #include <signal.h> | |
ccacf27f MD |
14 | #include <stdlib.h> |
15 | #include <stdint.h> | |
16 | #include <string.h> | |
17 | #include <errno.h> | |
18 | #include <poll.h> | |
19 | #include <sys/time.h> | |
20 | #include <unistd.h> | |
21 | #include <sched.h> | |
22 | ||
23 | #include "compat-getcpu.h" | |
01477510 | 24 | #include <urcu/assert.h> |
6cd23d47 MD |
25 | #include <urcu/wfcqueue.h> |
26 | #include <urcu/pointer.h> | |
27 | #include <urcu/list.h> | |
28 | #include <urcu/futex.h> | |
29 | #include <urcu/tls-compat.h> | |
30 | #include <urcu/ref.h> | |
ccacf27f MD |
31 | #include "urcu-die.h" |
32 | ||
33 | #include "workqueue.h" | |
34 | ||
35 | #define SET_AFFINITY_CHECK_PERIOD (1U << 8) /* 256 */ | |
36 | #define SET_AFFINITY_CHECK_PERIOD_MASK (SET_AFFINITY_CHECK_PERIOD - 1) | |
37 | ||
38 | /* Data structure that identifies a workqueue. */ | |
39 | ||
40 | struct urcu_workqueue { | |
41 | /* | |
42 | * We do not align head on a different cache-line than tail | |
1b6fc173 MD |
43 | * mainly because workqueue threads use batching ("splice") to |
44 | * get an entire list of callbacks, which effectively empties | |
45 | * the queue, and requires to touch the tail anyway. | |
ccacf27f MD |
46 | */ |
47 | struct cds_wfcq_tail cbs_tail; | |
48 | struct cds_wfcq_head cbs_head; | |
49 | unsigned long flags; | |
50 | int32_t futex; | |
51 | unsigned long qlen; /* maintained for debugging. */ | |
52 | pthread_t tid; | |
53 | int cpu_affinity; | |
54 | unsigned long loop_count; | |
55 | void *priv; | |
56 | void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv); | |
57 | void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv); | |
58 | void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv); | |
59 | void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv); | |
60 | void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv); | |
61 | void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv); | |
62 | void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv); | |
63 | } __attribute__((aligned(CAA_CACHE_LINE_SIZE))); | |
64 | ||
65 | struct urcu_workqueue_completion { | |
66 | int barrier_count; | |
67 | int32_t futex; | |
68 | struct urcu_ref ref; | |
69 | }; | |
70 | ||
71 | struct urcu_workqueue_completion_work { | |
72 | struct urcu_work work; | |
73 | struct urcu_workqueue_completion *completion; | |
74 | }; | |
75 | ||
76 | /* | |
77 | * Periodically retry setting CPU affinity if we migrate. | |
78 | * Losing affinity can be caused by CPU hotunplug/hotplug, or by | |
79 | * cpuset(7). | |
80 | */ | |
2388c075 | 81 | #ifdef HAVE_SCHED_SETAFFINITY |
ccacf27f MD |
82 | static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue) |
83 | { | |
84 | cpu_set_t mask; | |
85 | int ret; | |
86 | ||
87 | if (workqueue->cpu_affinity < 0) | |
88 | return 0; | |
89 | if (++workqueue->loop_count & SET_AFFINITY_CHECK_PERIOD_MASK) | |
90 | return 0; | |
91 | if (urcu_sched_getcpu() == workqueue->cpu_affinity) | |
92 | return 0; | |
93 | ||
94 | CPU_ZERO(&mask); | |
95 | CPU_SET(workqueue->cpu_affinity, &mask); | |
ccacf27f | 96 | ret = sched_setaffinity(0, sizeof(mask), &mask); |
0614a2e6 | 97 | |
ccacf27f MD |
98 | /* |
99 | * EINVAL is fine: can be caused by hotunplugged CPUs, or by | |
100 | * cpuset(7). This is why we should always retry if we detect | |
101 | * migration. | |
102 | */ | |
103 | if (ret && errno == EINVAL) { | |
104 | ret = 0; | |
105 | errno = 0; | |
106 | } | |
107 | return ret; | |
108 | } | |
109 | #else | |
a142df4e | 110 | static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue __attribute__((unused))) |
ccacf27f MD |
111 | { |
112 | return 0; | |
113 | } | |
114 | #endif | |
115 | ||
116 | static void futex_wait(int32_t *futex) | |
117 | { | |
118 | /* Read condition before read futex */ | |
119 | cmm_smp_mb(); | |
80c34c2d MD |
120 | while (uatomic_read(futex) == -1) { |
121 | if (!futex_async(futex, FUTEX_WAIT, -1, NULL, NULL, 0)) { | |
122 | /* | |
123 | * Prior queued wakeups queued by unrelated code | |
124 | * using the same address can cause futex wait to | |
125 | * return 0 even through the futex value is still | |
126 | * -1 (spurious wakeups). Check the value again | |
127 | * in user-space to validate whether it really | |
128 | * differs from -1. | |
129 | */ | |
130 | continue; | |
131 | } | |
ccacf27f | 132 | switch (errno) { |
80c34c2d | 133 | case EAGAIN: |
ccacf27f MD |
134 | /* Value already changed. */ |
135 | return; | |
136 | case EINTR: | |
137 | /* Retry if interrupted by signal. */ | |
80c34c2d | 138 | break; /* Get out of switch. Check again. */ |
ccacf27f MD |
139 | default: |
140 | /* Unexpected error. */ | |
141 | urcu_die(errno); | |
142 | } | |
143 | } | |
144 | } | |
145 | ||
146 | static void futex_wake_up(int32_t *futex) | |
147 | { | |
148 | /* Write to condition before reading/writing futex */ | |
149 | cmm_smp_mb(); | |
150 | if (caa_unlikely(uatomic_read(futex) == -1)) { | |
151 | uatomic_set(futex, 0); | |
152 | if (futex_async(futex, FUTEX_WAKE, 1, | |
153 | NULL, NULL, 0) < 0) | |
154 | urcu_die(errno); | |
155 | } | |
156 | } | |
157 | ||
158 | /* This is the code run by each worker thread. */ | |
159 | ||
160 | static void *workqueue_thread(void *arg) | |
161 | { | |
162 | unsigned long cbcount; | |
163 | struct urcu_workqueue *workqueue = (struct urcu_workqueue *) arg; | |
164 | int rt = !!(uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_RT); | |
165 | ||
166 | if (set_thread_cpu_affinity(workqueue)) | |
167 | urcu_die(errno); | |
168 | ||
169 | if (workqueue->initialize_worker_fct) | |
170 | workqueue->initialize_worker_fct(workqueue, workqueue->priv); | |
171 | ||
172 | if (!rt) { | |
173 | uatomic_dec(&workqueue->futex); | |
174 | /* Decrement futex before reading workqueue */ | |
175 | cmm_smp_mb(); | |
176 | } | |
177 | for (;;) { | |
178 | struct cds_wfcq_head cbs_tmp_head; | |
179 | struct cds_wfcq_tail cbs_tmp_tail; | |
180 | struct cds_wfcq_node *cbs, *cbs_tmp_n; | |
181 | enum cds_wfcq_ret splice_ret; | |
182 | ||
183 | if (set_thread_cpu_affinity(workqueue)) | |
184 | urcu_die(errno); | |
185 | ||
186 | if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) { | |
187 | /* | |
188 | * Pause requested. Become quiescent: remove | |
189 | * ourself from all global lists, and don't | |
190 | * process any callback. The callback lists may | |
191 | * still be non-empty though. | |
192 | */ | |
193 | if (workqueue->worker_before_pause_fct) | |
194 | workqueue->worker_before_pause_fct(workqueue, workqueue->priv); | |
195 | cmm_smp_mb__before_uatomic_or(); | |
196 | uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSED); | |
197 | while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSE) != 0) | |
198 | (void) poll(NULL, 0, 1); | |
199 | uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSED); | |
200 | cmm_smp_mb__after_uatomic_and(); | |
201 | if (workqueue->worker_after_resume_fct) | |
202 | workqueue->worker_after_resume_fct(workqueue, workqueue->priv); | |
203 | } | |
204 | ||
205 | cds_wfcq_init(&cbs_tmp_head, &cbs_tmp_tail); | |
206 | splice_ret = __cds_wfcq_splice_blocking(&cbs_tmp_head, | |
207 | &cbs_tmp_tail, &workqueue->cbs_head, &workqueue->cbs_tail); | |
01477510 FD |
208 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK); |
209 | urcu_posix_assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY); | |
ccacf27f MD |
210 | if (splice_ret != CDS_WFCQ_RET_SRC_EMPTY) { |
211 | if (workqueue->grace_period_fct) | |
212 | workqueue->grace_period_fct(workqueue, workqueue->priv); | |
213 | cbcount = 0; | |
214 | __cds_wfcq_for_each_blocking_safe(&cbs_tmp_head, | |
215 | &cbs_tmp_tail, cbs, cbs_tmp_n) { | |
d25f25df | 216 | struct urcu_work *uwp; |
ccacf27f | 217 | |
d25f25df MD |
218 | uwp = caa_container_of(cbs, |
219 | struct urcu_work, next); | |
220 | uwp->func(uwp); | |
ccacf27f MD |
221 | cbcount++; |
222 | } | |
223 | uatomic_sub(&workqueue->qlen, cbcount); | |
224 | } | |
225 | if (uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_STOP) | |
226 | break; | |
227 | if (workqueue->worker_before_wait_fct) | |
228 | workqueue->worker_before_wait_fct(workqueue, workqueue->priv); | |
229 | if (!rt) { | |
230 | if (cds_wfcq_empty(&workqueue->cbs_head, | |
231 | &workqueue->cbs_tail)) { | |
232 | futex_wait(&workqueue->futex); | |
ccacf27f MD |
233 | uatomic_dec(&workqueue->futex); |
234 | /* | |
235 | * Decrement futex before reading | |
1b6fc173 | 236 | * urcu_work list. |
ccacf27f MD |
237 | */ |
238 | cmm_smp_mb(); | |
ccacf27f MD |
239 | } |
240 | } else { | |
5bbe95bb JG |
241 | if (cds_wfcq_empty(&workqueue->cbs_head, |
242 | &workqueue->cbs_tail)) { | |
243 | (void) poll(NULL, 0, 10); | |
244 | } | |
ccacf27f MD |
245 | } |
246 | if (workqueue->worker_after_wake_up_fct) | |
247 | workqueue->worker_after_wake_up_fct(workqueue, workqueue->priv); | |
248 | } | |
249 | if (!rt) { | |
250 | /* | |
1b6fc173 | 251 | * Read urcu_work list before write futex. |
ccacf27f MD |
252 | */ |
253 | cmm_smp_mb(); | |
254 | uatomic_set(&workqueue->futex, 0); | |
255 | } | |
256 | if (workqueue->finalize_worker_fct) | |
257 | workqueue->finalize_worker_fct(workqueue, workqueue->priv); | |
258 | return NULL; | |
259 | } | |
260 | ||
261 | struct urcu_workqueue *urcu_workqueue_create(unsigned long flags, | |
262 | int cpu_affinity, void *priv, | |
263 | void (*grace_period_fct)(struct urcu_workqueue *workqueue, void *priv), | |
264 | void (*initialize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), | |
265 | void (*finalize_worker_fct)(struct urcu_workqueue *workqueue, void *priv), | |
266 | void (*worker_before_wait_fct)(struct urcu_workqueue *workqueue, void *priv), | |
267 | void (*worker_after_wake_up_fct)(struct urcu_workqueue *workqueue, void *priv), | |
268 | void (*worker_before_pause_fct)(struct urcu_workqueue *workqueue, void *priv), | |
269 | void (*worker_after_resume_fct)(struct urcu_workqueue *workqueue, void *priv)) | |
270 | { | |
271 | struct urcu_workqueue *workqueue; | |
272 | int ret; | |
ea3a28a3 | 273 | sigset_t newmask, oldmask; |
ccacf27f MD |
274 | |
275 | workqueue = malloc(sizeof(*workqueue)); | |
276 | if (workqueue == NULL) | |
277 | urcu_die(errno); | |
278 | memset(workqueue, '\0', sizeof(*workqueue)); | |
279 | cds_wfcq_init(&workqueue->cbs_head, &workqueue->cbs_tail); | |
280 | workqueue->qlen = 0; | |
281 | workqueue->futex = 0; | |
282 | workqueue->flags = flags; | |
283 | workqueue->priv = priv; | |
284 | workqueue->grace_period_fct = grace_period_fct; | |
285 | workqueue->initialize_worker_fct = initialize_worker_fct; | |
286 | workqueue->finalize_worker_fct = finalize_worker_fct; | |
287 | workqueue->worker_before_wait_fct = worker_before_wait_fct; | |
288 | workqueue->worker_after_wake_up_fct = worker_after_wake_up_fct; | |
289 | workqueue->worker_before_pause_fct = worker_before_pause_fct; | |
290 | workqueue->worker_after_resume_fct = worker_after_resume_fct; | |
291 | workqueue->cpu_affinity = cpu_affinity; | |
292 | workqueue->loop_count = 0; | |
293 | cmm_smp_mb(); /* Structure initialized before pointer is planted. */ | |
ea3a28a3 MD |
294 | |
295 | ret = sigfillset(&newmask); | |
296 | urcu_posix_assert(!ret); | |
297 | ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask); | |
298 | urcu_posix_assert(!ret); | |
299 | ||
ccacf27f MD |
300 | ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue); |
301 | if (ret) { | |
302 | urcu_die(ret); | |
303 | } | |
ea3a28a3 MD |
304 | |
305 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
306 | urcu_posix_assert(!ret); | |
307 | ||
ccacf27f MD |
308 | return workqueue; |
309 | } | |
310 | ||
311 | static void wake_worker_thread(struct urcu_workqueue *workqueue) | |
312 | { | |
9db9edcc | 313 | if (!(_CMM_LOAD_SHARED(workqueue->flags) & URCU_WORKQUEUE_RT)) |
ccacf27f MD |
314 | futex_wake_up(&workqueue->futex); |
315 | } | |
316 | ||
317 | static int urcu_workqueue_destroy_worker(struct urcu_workqueue *workqueue) | |
318 | { | |
319 | int ret; | |
320 | void *retval; | |
321 | ||
322 | uatomic_or(&workqueue->flags, URCU_WORKQUEUE_STOP); | |
323 | wake_worker_thread(workqueue); | |
324 | ||
325 | ret = pthread_join(workqueue->tid, &retval); | |
326 | if (ret) { | |
327 | urcu_die(ret); | |
328 | } | |
329 | if (retval != NULL) { | |
330 | urcu_die(EINVAL); | |
331 | } | |
332 | workqueue->flags &= ~URCU_WORKQUEUE_STOP; | |
333 | workqueue->tid = 0; | |
334 | return 0; | |
335 | } | |
336 | ||
337 | void urcu_workqueue_destroy(struct urcu_workqueue *workqueue) | |
338 | { | |
339 | if (workqueue == NULL) { | |
340 | return; | |
341 | } | |
342 | if (urcu_workqueue_destroy_worker(workqueue)) { | |
343 | urcu_die(errno); | |
344 | } | |
01477510 | 345 | urcu_posix_assert(cds_wfcq_empty(&workqueue->cbs_head, &workqueue->cbs_tail)); |
ccacf27f MD |
346 | free(workqueue); |
347 | } | |
348 | ||
349 | void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue, | |
350 | struct urcu_work *work, | |
351 | void (*func)(struct urcu_work *work)) | |
352 | { | |
353 | cds_wfcq_node_init(&work->next); | |
354 | work->func = func; | |
355 | cds_wfcq_enqueue(&workqueue->cbs_head, &workqueue->cbs_tail, &work->next); | |
356 | uatomic_inc(&workqueue->qlen); | |
357 | wake_worker_thread(workqueue); | |
358 | } | |
359 | ||
360 | static | |
361 | void free_completion(struct urcu_ref *ref) | |
362 | { | |
363 | struct urcu_workqueue_completion *completion; | |
364 | ||
365 | completion = caa_container_of(ref, struct urcu_workqueue_completion, ref); | |
366 | free(completion); | |
367 | } | |
368 | ||
369 | static | |
370 | void _urcu_workqueue_wait_complete(struct urcu_work *work) | |
371 | { | |
372 | struct urcu_workqueue_completion_work *completion_work; | |
373 | struct urcu_workqueue_completion *completion; | |
374 | ||
375 | completion_work = caa_container_of(work, struct urcu_workqueue_completion_work, work); | |
376 | completion = completion_work->completion; | |
377 | if (!uatomic_sub_return(&completion->barrier_count, 1)) | |
378 | futex_wake_up(&completion->futex); | |
379 | urcu_ref_put(&completion->ref, free_completion); | |
380 | free(completion_work); | |
381 | } | |
382 | ||
383 | struct urcu_workqueue_completion *urcu_workqueue_create_completion(void) | |
384 | { | |
385 | struct urcu_workqueue_completion *completion; | |
386 | ||
81270292 | 387 | completion = calloc(1, sizeof(*completion)); |
ccacf27f MD |
388 | if (!completion) |
389 | urcu_die(errno); | |
390 | urcu_ref_set(&completion->ref, 1); | |
391 | completion->barrier_count = 0; | |
392 | return completion; | |
393 | } | |
394 | ||
395 | void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion) | |
396 | { | |
397 | urcu_ref_put(&completion->ref, free_completion); | |
398 | } | |
399 | ||
400 | void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion) | |
401 | { | |
402 | /* Wait for them */ | |
403 | for (;;) { | |
404 | uatomic_dec(&completion->futex); | |
405 | /* Decrement futex before reading barrier_count */ | |
406 | cmm_smp_mb(); | |
407 | if (!uatomic_read(&completion->barrier_count)) | |
408 | break; | |
409 | futex_wait(&completion->futex); | |
410 | } | |
411 | } | |
412 | ||
413 | void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue, | |
414 | struct urcu_workqueue_completion *completion) | |
415 | { | |
416 | struct urcu_workqueue_completion_work *work; | |
417 | ||
81270292 | 418 | work = calloc(1, sizeof(*work)); |
ccacf27f MD |
419 | if (!work) |
420 | urcu_die(errno); | |
421 | work->completion = completion; | |
422 | urcu_ref_get(&completion->ref); | |
423 | uatomic_inc(&completion->barrier_count); | |
424 | urcu_workqueue_queue_work(workqueue, &work->work, _urcu_workqueue_wait_complete); | |
425 | } | |
426 | ||
427 | /* | |
428 | * Wait for all in-flight work to complete execution. | |
429 | */ | |
430 | void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue) | |
431 | { | |
432 | struct urcu_workqueue_completion *completion; | |
433 | ||
434 | completion = urcu_workqueue_create_completion(); | |
435 | if (!completion) | |
436 | urcu_die(ENOMEM); | |
437 | urcu_workqueue_queue_completion(workqueue, completion); | |
438 | urcu_workqueue_wait_completion(completion); | |
439 | urcu_workqueue_destroy_completion(completion); | |
440 | } | |
441 | ||
442 | /* To be used in before fork handler. */ | |
443 | void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue) | |
444 | { | |
445 | uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSE); | |
446 | cmm_smp_mb__after_uatomic_or(); | |
447 | wake_worker_thread(workqueue); | |
448 | ||
449 | while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) == 0) | |
450 | (void) poll(NULL, 0, 1); | |
451 | } | |
452 | ||
453 | /* To be used in after fork parent handler. */ | |
454 | void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue) | |
455 | { | |
456 | uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSE); | |
457 | while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) != 0) | |
458 | (void) poll(NULL, 0, 1); | |
459 | } | |
460 | ||
461 | void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue) | |
462 | { | |
463 | int ret; | |
ea3a28a3 | 464 | sigset_t newmask, oldmask; |
ccacf27f MD |
465 | |
466 | /* Clear workqueue state from parent. */ | |
467 | workqueue->flags &= ~URCU_WORKQUEUE_PAUSED; | |
468 | workqueue->flags &= ~URCU_WORKQUEUE_PAUSE; | |
469 | workqueue->tid = 0; | |
ea3a28a3 MD |
470 | |
471 | ret = sigfillset(&newmask); | |
472 | urcu_posix_assert(!ret); | |
473 | ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask); | |
474 | urcu_posix_assert(!ret); | |
475 | ||
ccacf27f MD |
476 | ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue); |
477 | if (ret) { | |
478 | urcu_die(ret); | |
479 | } | |
ea3a28a3 MD |
480 | |
481 | ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL); | |
482 | urcu_posix_assert(!ret); | |
ccacf27f | 483 | } |