Fix: workqueue: remove unused variable "ret"
[urcu.git] / src / workqueue.c
CommitLineData
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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>
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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>
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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>
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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
54struct urcu_workqueue {
55 /*
56 * We do not align head on a different cache-line than tail
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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.
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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
79struct urcu_workqueue_completion {
80 int barrier_count;
81 int32_t futex;
82 struct urcu_ref ref;
83};
84
85struct 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
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96static 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
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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 124static int set_thread_cpu_affinity(struct urcu_workqueue *workqueue __attribute__((unused)))
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125{
126 return 0;
127}
128#endif
129
130static void futex_wait(int32_t *futex)
131{
132 /* Read condition before read futex */
133 cmm_smp_mb();
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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 }
ccacf27f 146 switch (errno) {
80c34c2d 147 case EAGAIN:
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148 /* Value already changed. */
149 return;
150 case EINTR:
151 /* Retry if interrupted by signal. */
80c34c2d 152 break; /* Get out of switch. Check again. */
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153 default:
154 /* Unexpected error. */
155 urcu_die(errno);
156 }
157 }
158}
159
160static 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
174static 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);
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222 urcu_posix_assert(splice_ret != CDS_WFCQ_RET_WOULDBLOCK);
223 urcu_posix_assert(splice_ret != CDS_WFCQ_RET_DEST_NON_EMPTY);
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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) {
d25f25df 230 struct urcu_work *uwp;
ccacf27f 231
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232 uwp = caa_container_of(cbs,
233 struct urcu_work, next);
234 uwp->func(uwp);
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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);
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247 uatomic_dec(&workqueue->futex);
248 /*
249 * Decrement futex before reading
1b6fc173 250 * urcu_work list.
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251 */
252 cmm_smp_mb();
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253 }
254 } else {
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255 if (cds_wfcq_empty(&workqueue->cbs_head,
256 &workqueue->cbs_tail)) {
257 (void) poll(NULL, 0, 10);
258 }
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259 }
260 if (workqueue->worker_after_wake_up_fct)
261 workqueue->worker_after_wake_up_fct(workqueue, workqueue->priv);
262 }
263 if (!rt) {
264 /*
1b6fc173 265 * Read urcu_work list before write futex.
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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
275struct 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
288 workqueue = malloc(sizeof(*workqueue));
289 if (workqueue == NULL)
290 urcu_die(errno);
291 memset(workqueue, '\0', sizeof(*workqueue));
292 cds_wfcq_init(&workqueue->cbs_head, &workqueue->cbs_tail);
293 workqueue->qlen = 0;
294 workqueue->futex = 0;
295 workqueue->flags = flags;
296 workqueue->priv = priv;
297 workqueue->grace_period_fct = grace_period_fct;
298 workqueue->initialize_worker_fct = initialize_worker_fct;
299 workqueue->finalize_worker_fct = finalize_worker_fct;
300 workqueue->worker_before_wait_fct = worker_before_wait_fct;
301 workqueue->worker_after_wake_up_fct = worker_after_wake_up_fct;
302 workqueue->worker_before_pause_fct = worker_before_pause_fct;
303 workqueue->worker_after_resume_fct = worker_after_resume_fct;
304 workqueue->cpu_affinity = cpu_affinity;
305 workqueue->loop_count = 0;
306 cmm_smp_mb(); /* Structure initialized before pointer is planted. */
307 ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
308 if (ret) {
309 urcu_die(ret);
310 }
311 return workqueue;
312}
313
314static void wake_worker_thread(struct urcu_workqueue *workqueue)
315{
9db9edcc 316 if (!(_CMM_LOAD_SHARED(workqueue->flags) & URCU_WORKQUEUE_RT))
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317 futex_wake_up(&workqueue->futex);
318}
319
320static int urcu_workqueue_destroy_worker(struct urcu_workqueue *workqueue)
321{
322 int ret;
323 void *retval;
324
325 uatomic_or(&workqueue->flags, URCU_WORKQUEUE_STOP);
326 wake_worker_thread(workqueue);
327
328 ret = pthread_join(workqueue->tid, &retval);
329 if (ret) {
330 urcu_die(ret);
331 }
332 if (retval != NULL) {
333 urcu_die(EINVAL);
334 }
335 workqueue->flags &= ~URCU_WORKQUEUE_STOP;
336 workqueue->tid = 0;
337 return 0;
338}
339
340void urcu_workqueue_destroy(struct urcu_workqueue *workqueue)
341{
342 if (workqueue == NULL) {
343 return;
344 }
345 if (urcu_workqueue_destroy_worker(workqueue)) {
346 urcu_die(errno);
347 }
01477510 348 urcu_posix_assert(cds_wfcq_empty(&workqueue->cbs_head, &workqueue->cbs_tail));
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349 free(workqueue);
350}
351
352void urcu_workqueue_queue_work(struct urcu_workqueue *workqueue,
353 struct urcu_work *work,
354 void (*func)(struct urcu_work *work))
355{
356 cds_wfcq_node_init(&work->next);
357 work->func = func;
358 cds_wfcq_enqueue(&workqueue->cbs_head, &workqueue->cbs_tail, &work->next);
359 uatomic_inc(&workqueue->qlen);
360 wake_worker_thread(workqueue);
361}
362
363static
364void free_completion(struct urcu_ref *ref)
365{
366 struct urcu_workqueue_completion *completion;
367
368 completion = caa_container_of(ref, struct urcu_workqueue_completion, ref);
369 free(completion);
370}
371
372static
373void _urcu_workqueue_wait_complete(struct urcu_work *work)
374{
375 struct urcu_workqueue_completion_work *completion_work;
376 struct urcu_workqueue_completion *completion;
377
378 completion_work = caa_container_of(work, struct urcu_workqueue_completion_work, work);
379 completion = completion_work->completion;
380 if (!uatomic_sub_return(&completion->barrier_count, 1))
381 futex_wake_up(&completion->futex);
382 urcu_ref_put(&completion->ref, free_completion);
383 free(completion_work);
384}
385
386struct urcu_workqueue_completion *urcu_workqueue_create_completion(void)
387{
388 struct urcu_workqueue_completion *completion;
389
390 completion = calloc(sizeof(*completion), 1);
391 if (!completion)
392 urcu_die(errno);
393 urcu_ref_set(&completion->ref, 1);
394 completion->barrier_count = 0;
395 return completion;
396}
397
398void urcu_workqueue_destroy_completion(struct urcu_workqueue_completion *completion)
399{
400 urcu_ref_put(&completion->ref, free_completion);
401}
402
403void urcu_workqueue_wait_completion(struct urcu_workqueue_completion *completion)
404{
405 /* Wait for them */
406 for (;;) {
407 uatomic_dec(&completion->futex);
408 /* Decrement futex before reading barrier_count */
409 cmm_smp_mb();
410 if (!uatomic_read(&completion->barrier_count))
411 break;
412 futex_wait(&completion->futex);
413 }
414}
415
416void urcu_workqueue_queue_completion(struct urcu_workqueue *workqueue,
417 struct urcu_workqueue_completion *completion)
418{
419 struct urcu_workqueue_completion_work *work;
420
421 work = calloc(sizeof(*work), 1);
422 if (!work)
423 urcu_die(errno);
424 work->completion = completion;
425 urcu_ref_get(&completion->ref);
426 uatomic_inc(&completion->barrier_count);
427 urcu_workqueue_queue_work(workqueue, &work->work, _urcu_workqueue_wait_complete);
428}
429
430/*
431 * Wait for all in-flight work to complete execution.
432 */
433void urcu_workqueue_flush_queued_work(struct urcu_workqueue *workqueue)
434{
435 struct urcu_workqueue_completion *completion;
436
437 completion = urcu_workqueue_create_completion();
438 if (!completion)
439 urcu_die(ENOMEM);
440 urcu_workqueue_queue_completion(workqueue, completion);
441 urcu_workqueue_wait_completion(completion);
442 urcu_workqueue_destroy_completion(completion);
443}
444
445/* To be used in before fork handler. */
446void urcu_workqueue_pause_worker(struct urcu_workqueue *workqueue)
447{
448 uatomic_or(&workqueue->flags, URCU_WORKQUEUE_PAUSE);
449 cmm_smp_mb__after_uatomic_or();
450 wake_worker_thread(workqueue);
451
452 while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) == 0)
453 (void) poll(NULL, 0, 1);
454}
455
456/* To be used in after fork parent handler. */
457void urcu_workqueue_resume_worker(struct urcu_workqueue *workqueue)
458{
459 uatomic_and(&workqueue->flags, ~URCU_WORKQUEUE_PAUSE);
460 while ((uatomic_read(&workqueue->flags) & URCU_WORKQUEUE_PAUSED) != 0)
461 (void) poll(NULL, 0, 1);
462}
463
464void urcu_workqueue_create_worker(struct urcu_workqueue *workqueue)
465{
466 int ret;
467
468 /* Clear workqueue state from parent. */
469 workqueue->flags &= ~URCU_WORKQUEUE_PAUSED;
470 workqueue->flags &= ~URCU_WORKQUEUE_PAUSE;
471 workqueue->tid = 0;
472 ret = pthread_create(&workqueue->tid, NULL, workqueue_thread, workqueue);
473 if (ret) {
474 urcu_die(ret);
475 }
476}
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