1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2018, Matthew Macy <mmacy@freebsd.org>
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 */
28
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD: stable/12/sys/kern/subr_epoch.c 371677 2022-02-22 07:30:50Z git2svn $");
31
32 #include <sys/param.h>
33 #include <sys/types.h>
34 #include <sys/systm.h>
35 #include <sys/counter.h>
36 #include <sys/epoch.h>
37 #include <sys/gtaskqueue.h>
38 #include <sys/kernel.h>
39 #include <sys/limits.h>
40 #include <sys/lock.h>
41 #include <sys/malloc.h>
42 #include <sys/mutex.h>
43 #include <sys/pcpu.h>
44 #include <sys/proc.h>
45 #include <sys/sched.h>
46 #include <sys/sx.h>
47 #include <sys/smp.h>
48 #include <sys/sysctl.h>
49 #include <sys/turnstile.h>
50 #include <vm/vm.h>
51 #include <vm/vm_extern.h>
52 #include <vm/vm_kern.h>
53 #include <vm/uma.h>
54
55 #include <ck_epoch.h>
56
57 #ifdef __amd64__
58 #define EPOCH_ALIGN CACHE_LINE_SIZE*2
59 #else
60 #define EPOCH_ALIGN CACHE_LINE_SIZE
61 #endif
62
63 TAILQ_HEAD (epoch_tdlist, epoch_tracker);
64 typedef struct epoch_record {
65 ck_epoch_record_t er_record;
66 volatile struct epoch_tdlist er_tdlist;
67 volatile uint32_t er_gen;
68 uint32_t er_cpuid;
69 /* fields above are part of KBI and cannot be modified */
70 struct epoch_context er_drain_ctx;
71 struct epoch *er_parent;
72 #ifdef INVARIANTS
73 /* Used to verify record ownership for non-preemptible epochs. */
74 struct thread *er_td;
75 #endif
76 } __aligned(EPOCH_ALIGN) *epoch_record_t;
77
78 struct epoch {
79 struct ck_epoch e_epoch __aligned(EPOCH_ALIGN);
80 epoch_record_t e_pcpu_record;
81 int e_in_use;
82 int e_flags;
83 /* fields above are part of KBI and cannot be modified */
84 struct sx e_drain_sx;
85 struct mtx e_drain_mtx;
86 volatile int e_drain_count;
87 };
88
89 /* arbitrary --- needs benchmarking */
90 #define MAX_ADAPTIVE_SPIN 100
91 #define MAX_EPOCHS 64
92
93 CTASSERT(sizeof(ck_epoch_entry_t) == sizeof(struct epoch_context));
94 SYSCTL_NODE(_kern, OID_AUTO, epoch, CTLFLAG_RW, 0, "epoch information");
95 SYSCTL_NODE(_kern_epoch, OID_AUTO, stats, CTLFLAG_RW, 0, "epoch stats");
96
97 /* Stats. */
98 static counter_u64_t block_count;
99
100 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, nblocked, CTLFLAG_RW,
101 &block_count, "# of times a thread was in an epoch when epoch_wait was called");
102 static counter_u64_t migrate_count;
103
104 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, migrations, CTLFLAG_RW,
105 &migrate_count, "# of times thread was migrated to another CPU in epoch_wait");
106 static counter_u64_t turnstile_count;
107
108 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, ncontended, CTLFLAG_RW,
109 &turnstile_count, "# of times a thread was blocked on a lock in an epoch during an epoch_wait");
110 static counter_u64_t switch_count;
111
112 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, switches, CTLFLAG_RW,
113 &switch_count, "# of times a thread voluntarily context switched in epoch_wait");
114 static counter_u64_t epoch_call_count;
115
116 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_calls, CTLFLAG_RW,
117 &epoch_call_count, "# of times a callback was deferred");
118 static counter_u64_t epoch_call_task_count;
119
120 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_call_tasks, CTLFLAG_RW,
121 &epoch_call_task_count, "# of times a callback task was run");
122
123 TAILQ_HEAD (threadlist, thread);
124
125 CK_STACK_CONTAINER(struct ck_epoch_entry, stack_entry,
126 ck_epoch_entry_container)
127
128 static struct epoch epoch_array[MAX_EPOCHS];
129
130 DPCPU_DEFINE(struct grouptask, epoch_cb_task);
131 DPCPU_DEFINE(int, epoch_cb_count);
132
133 static __read_mostly int inited;
134 __read_mostly epoch_t global_epoch;
135 __read_mostly epoch_t global_epoch_preempt;
136
137 static void epoch_call_task(void *context __unused);
138 static uma_zone_t pcpu_zone_record;
139
140 static struct sx epoch_sx;
141
142 #define EPOCH_LOCK() sx_xlock(&epoch_sx)
143 #define EPOCH_UNLOCK() sx_xunlock(&epoch_sx)
144
145 static void
epoch_init(void * arg __unused)146 epoch_init(void *arg __unused)
147 {
148 int cpu;
149
150 block_count = counter_u64_alloc(M_WAITOK);
151 migrate_count = counter_u64_alloc(M_WAITOK);
152 turnstile_count = counter_u64_alloc(M_WAITOK);
153 switch_count = counter_u64_alloc(M_WAITOK);
154 epoch_call_count = counter_u64_alloc(M_WAITOK);
155 epoch_call_task_count = counter_u64_alloc(M_WAITOK);
156
157 pcpu_zone_record = uma_zcreate("epoch_record pcpu",
158 sizeof(struct epoch_record), NULL, NULL, NULL, NULL,
159 UMA_ALIGN_PTR, UMA_ZONE_PCPU);
160 CPU_FOREACH(cpu) {
161 GROUPTASK_INIT(DPCPU_ID_PTR(cpu, epoch_cb_task), 0,
162 epoch_call_task, NULL);
163 taskqgroup_attach_cpu(qgroup_softirq,
164 DPCPU_ID_PTR(cpu, epoch_cb_task), NULL, cpu, -1,
165 "epoch call task");
166 }
167 sx_init(&epoch_sx, "epoch-sx");
168 inited = 1;
169 global_epoch = epoch_alloc(0);
170 global_epoch_preempt = epoch_alloc(EPOCH_PREEMPT);
171 }
172 SYSINIT(epoch, SI_SUB_EPOCH, SI_ORDER_FIRST, epoch_init, NULL);
173
174 #if !defined(EARLY_AP_STARTUP)
175 static void
epoch_init_smp(void * dummy __unused)176 epoch_init_smp(void *dummy __unused)
177 {
178 inited = 2;
179 }
180 SYSINIT(epoch_smp, SI_SUB_SMP + 1, SI_ORDER_FIRST, epoch_init_smp, NULL);
181 #endif
182
183 static void
epoch_ctor(epoch_t epoch)184 epoch_ctor(epoch_t epoch)
185 {
186 epoch_record_t er;
187 int cpu;
188
189 epoch->e_pcpu_record = uma_zalloc_pcpu(pcpu_zone_record, M_WAITOK);
190 CPU_FOREACH(cpu) {
191 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
192 bzero(er, sizeof(*er));
193 ck_epoch_register(&epoch->e_epoch, &er->er_record, NULL);
194 TAILQ_INIT((struct threadlist *)(uintptr_t)&er->er_tdlist);
195 er->er_cpuid = cpu;
196 er->er_parent = epoch;
197 }
198 }
199
200 static void
epoch_adjust_prio(struct thread * td,u_char prio)201 epoch_adjust_prio(struct thread *td, u_char prio)
202 {
203
204 thread_lock(td);
205 sched_prio(td, prio);
206 thread_unlock(td);
207 }
208
209 epoch_t
epoch_alloc(int flags)210 epoch_alloc(int flags)
211 {
212 epoch_t epoch;
213 int i;
214
215 if (__predict_false(!inited))
216 panic("%s called too early in boot", __func__);
217
218 EPOCH_LOCK();
219
220 /*
221 * Find a free index in the epoch array. If no free index is
222 * found, try to use the index after the last one.
223 */
224 for (i = 0;; i++) {
225 /*
226 * If too many epochs are currently allocated,
227 * return NULL.
228 */
229 if (i == MAX_EPOCHS) {
230 epoch = NULL;
231 goto done;
232 }
233 if (epoch_array[i].e_in_use == 0)
234 break;
235 }
236
237 epoch = epoch_array + i;
238 ck_epoch_init(&epoch->e_epoch);
239 epoch_ctor(epoch);
240 epoch->e_flags = flags;
241 sx_init(&epoch->e_drain_sx, "epoch-drain-sx");
242 mtx_init(&epoch->e_drain_mtx, "epoch-drain-mtx", NULL, MTX_DEF);
243
244 /*
245 * Set e_in_use last, because when this field is set the
246 * epoch_call_task() function will start scanning this epoch
247 * structure.
248 */
249 atomic_store_rel_int(&epoch->e_in_use, 1);
250 done:
251 EPOCH_UNLOCK();
252 return (epoch);
253 }
254
255 void
epoch_free(epoch_t epoch)256 epoch_free(epoch_t epoch)
257 {
258 #ifdef INVARIANTS
259 int cpu;
260 #endif
261
262 EPOCH_LOCK();
263
264 MPASS(epoch->e_in_use != 0);
265
266 epoch_drain_callbacks(epoch);
267
268 atomic_store_rel_int(&epoch->e_in_use, 0);
269 /*
270 * Make sure the epoch_call_task() function see e_in_use equal
271 * to zero, by calling epoch_wait() on the global_epoch:
272 */
273 epoch_wait(global_epoch);
274 #ifdef INVARIANTS
275 CPU_FOREACH(cpu) {
276 epoch_record_t er;
277
278 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
279
280 /*
281 * Sanity check: none of the records should be in use anymore.
282 * We drained callbacks above and freeing the pcpu records is
283 * imminent.
284 */
285 MPASS(er->er_td == NULL);
286 MPASS(TAILQ_EMPTY(&er->er_tdlist));
287 }
288 #endif
289 uma_zfree_pcpu(pcpu_zone_record, epoch->e_pcpu_record);
290 mtx_destroy(&epoch->e_drain_mtx);
291 sx_destroy(&epoch->e_drain_sx);
292 memset(epoch, 0, sizeof(*epoch));
293
294 EPOCH_UNLOCK();
295 }
296
297 static epoch_record_t
epoch_currecord(epoch_t epoch)298 epoch_currecord(epoch_t epoch)
299 {
300
301 return (zpcpu_get_cpu(epoch->e_pcpu_record, curcpu));
302 }
303
304 #define INIT_CHECK(epoch) \
305 do { \
306 if (__predict_false((epoch) == NULL)) \
307 return; \
308 } while (0)
309
310 void
epoch_enter_preempt(epoch_t epoch,epoch_tracker_t et)311 epoch_enter_preempt(epoch_t epoch, epoch_tracker_t et)
312 {
313 struct epoch_record *er;
314 struct thread *td;
315
316 MPASS(cold || epoch != NULL);
317 INIT_CHECK(epoch);
318 MPASS(epoch->e_flags & EPOCH_PREEMPT);
319 #ifdef EPOCH_TRACKER_DEBUG
320 et->et_magic_pre = EPOCH_MAGIC0;
321 et->et_magic_post = EPOCH_MAGIC1;
322 #endif
323 td = curthread;
324 et->et_td = td;
325 td->td_epochnest++;
326 critical_enter();
327 sched_pin();
328
329 td->td_pre_epoch_prio = td->td_priority;
330 er = epoch_currecord(epoch);
331 /* Record-level tracking is reserved for non-preemptible epochs. */
332 MPASS(er->er_td == NULL);
333 TAILQ_INSERT_TAIL(&er->er_tdlist, et, et_link);
334 ck_epoch_begin(&er->er_record, &et->et_section);
335 critical_exit();
336 }
337
338 void
epoch_enter(epoch_t epoch)339 epoch_enter(epoch_t epoch)
340 {
341 struct thread *td;
342 epoch_record_t er;
343
344 MPASS(cold || epoch != NULL);
345 INIT_CHECK(epoch);
346 td = curthread;
347
348 td->td_epochnest++;
349 critical_enter();
350 er = epoch_currecord(epoch);
351 #ifdef INVARIANTS
352 if (er->er_record.active == 0) {
353 MPASS(er->er_td == NULL);
354 er->er_td = curthread;
355 } else {
356 /* We've recursed, just make sure our accounting isn't wrong. */
357 MPASS(er->er_td == curthread);
358 }
359 #endif
360 ck_epoch_begin(&er->er_record, NULL);
361 }
362
363 void
epoch_exit_preempt(epoch_t epoch,epoch_tracker_t et)364 epoch_exit_preempt(epoch_t epoch, epoch_tracker_t et)
365 {
366 struct epoch_record *er;
367 struct thread *td;
368
369 INIT_CHECK(epoch);
370 td = curthread;
371 critical_enter();
372 sched_unpin();
373 MPASS(td->td_epochnest);
374 td->td_epochnest--;
375 er = epoch_currecord(epoch);
376 MPASS(epoch->e_flags & EPOCH_PREEMPT);
377 MPASS(et != NULL);
378 MPASS(et->et_td == td);
379 #ifdef EPOCH_TRACKER_DEBUG
380 MPASS(et->et_magic_pre == EPOCH_MAGIC0);
381 MPASS(et->et_magic_post == EPOCH_MAGIC1);
382 et->et_magic_pre = 0;
383 et->et_magic_post = 0;
384 #endif
385 #ifdef INVARIANTS
386 et->et_td = (void*)0xDEADBEEF;
387 /* Record-level tracking is reserved for non-preemptible epochs. */
388 MPASS(er->er_td == NULL);
389 #endif
390 ck_epoch_end(&er->er_record, &et->et_section);
391 TAILQ_REMOVE(&er->er_tdlist, et, et_link);
392 er->er_gen++;
393 if (__predict_false(td->td_pre_epoch_prio != td->td_priority))
394 epoch_adjust_prio(td, td->td_pre_epoch_prio);
395 critical_exit();
396 }
397
398 void
epoch_exit(epoch_t epoch)399 epoch_exit(epoch_t epoch)
400 {
401 struct thread *td;
402 epoch_record_t er;
403
404 INIT_CHECK(epoch);
405 td = curthread;
406 MPASS(td->td_epochnest);
407 td->td_epochnest--;
408 er = epoch_currecord(epoch);
409 ck_epoch_end(&er->er_record, NULL);
410 #ifdef INVARIANTS
411 MPASS(er->er_td == curthread);
412 if (er->er_record.active == 0)
413 er->er_td = NULL;
414 #endif
415 critical_exit();
416 }
417
418 /*
419 * epoch_block_handler_preempt() is a callback from the CK code when another
420 * thread is currently in an epoch section.
421 */
422 static void
epoch_block_handler_preempt(struct ck_epoch * global __unused,ck_epoch_record_t * cr,void * arg __unused)423 epoch_block_handler_preempt(struct ck_epoch *global __unused,
424 ck_epoch_record_t *cr, void *arg __unused)
425 {
426 epoch_record_t record;
427 struct thread *td, *owner, *curwaittd;
428 struct epoch_tracker *tdwait;
429 struct turnstile *ts;
430 struct lock_object *lock;
431 int spincount, gen;
432 int locksheld __unused;
433
434 record = __containerof(cr, struct epoch_record, er_record);
435 td = curthread;
436 locksheld = td->td_locks;
437 spincount = 0;
438 counter_u64_add(block_count, 1);
439 /*
440 * We lost a race and there's no longer any threads
441 * on the CPU in an epoch section.
442 */
443 if (TAILQ_EMPTY(&record->er_tdlist))
444 return;
445
446 if (record->er_cpuid != curcpu) {
447 /*
448 * If the head of the list is running, we can wait for it
449 * to remove itself from the list and thus save us the
450 * overhead of a migration
451 */
452 gen = record->er_gen;
453 thread_unlock(td);
454 /*
455 * We can't actually check if the waiting thread is running
456 * so we simply poll for it to exit before giving up and
457 * migrating.
458 */
459 do {
460 cpu_spinwait();
461 } while (!TAILQ_EMPTY(&record->er_tdlist) &&
462 gen == record->er_gen &&
463 spincount++ < MAX_ADAPTIVE_SPIN);
464 thread_lock(td);
465 /*
466 * If the generation has changed we can poll again
467 * otherwise we need to migrate.
468 */
469 if (gen != record->er_gen)
470 return;
471 /*
472 * Being on the same CPU as that of the record on which
473 * we need to wait allows us access to the thread
474 * list associated with that CPU. We can then examine the
475 * oldest thread in the queue and wait on its turnstile
476 * until it resumes and so on until a grace period
477 * elapses.
478 *
479 */
480 counter_u64_add(migrate_count, 1);
481 sched_bind(td, record->er_cpuid);
482 /*
483 * At this point we need to return to the ck code
484 * to scan to see if a grace period has elapsed.
485 * We can't move on to check the thread list, because
486 * in the meantime new threads may have arrived that
487 * in fact belong to a different epoch.
488 */
489 return;
490 }
491 /*
492 * Try to find a thread in an epoch section on this CPU
493 * waiting on a turnstile. Otherwise find the lowest
494 * priority thread (highest prio value) and drop our priority
495 * to match to allow it to run.
496 */
497 TAILQ_FOREACH(tdwait, &record->er_tdlist, et_link) {
498 /*
499 * Propagate our priority to any other waiters to prevent us
500 * from starving them. They will have their original priority
501 * restore on exit from epoch_wait().
502 */
503 curwaittd = tdwait->et_td;
504 if (!TD_IS_INHIBITED(curwaittd) && curwaittd->td_priority > td->td_priority) {
505 critical_enter();
506 thread_unlock(td);
507 thread_lock(curwaittd);
508 sched_prio(curwaittd, td->td_priority);
509 thread_unlock(curwaittd);
510 thread_lock(td);
511 critical_exit();
512 }
513 if (TD_IS_INHIBITED(curwaittd) && TD_ON_LOCK(curwaittd) &&
514 ((ts = curwaittd->td_blocked) != NULL)) {
515 /*
516 * We unlock td to allow turnstile_wait to reacquire
517 * the thread lock. Before unlocking it we enter a
518 * critical section to prevent preemption after we
519 * reenable interrupts by dropping the thread lock in
520 * order to prevent curwaittd from getting to run.
521 */
522 critical_enter();
523 thread_unlock(td);
524
525 if (turnstile_lock(ts, &lock, &owner)) {
526 if (ts == curwaittd->td_blocked) {
527 MPASS(TD_IS_INHIBITED(curwaittd) &&
528 TD_ON_LOCK(curwaittd));
529 critical_exit();
530 turnstile_wait(ts, owner,
531 curwaittd->td_tsqueue);
532 counter_u64_add(turnstile_count, 1);
533 thread_lock(td);
534 return;
535 }
536 turnstile_unlock(ts, lock);
537 }
538 thread_lock(td);
539 critical_exit();
540 KASSERT(td->td_locks == locksheld,
541 ("%d extra locks held", td->td_locks - locksheld));
542 }
543 }
544 /*
545 * We didn't find any threads actually blocked on a lock
546 * so we have nothing to do except context switch away.
547 */
548 counter_u64_add(switch_count, 1);
549 mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
550
551 /*
552 * Release the thread lock while yielding to
553 * allow other threads to acquire the lock
554 * pointed to by TDQ_LOCKPTR(td). Else a
555 * deadlock like situation might happen. (HPS)
556 */
557 thread_unlock(td);
558 thread_lock(td);
559 }
560
561 void
epoch_wait_preempt(epoch_t epoch)562 epoch_wait_preempt(epoch_t epoch)
563 {
564 struct thread *td;
565 int was_bound;
566 int old_cpu;
567 int old_pinned;
568 u_char old_prio;
569 int locks __unused;
570
571 MPASS(cold || epoch != NULL);
572 INIT_CHECK(epoch);
573 td = curthread;
574 #ifdef INVARIANTS
575 locks = curthread->td_locks;
576 MPASS(epoch->e_flags & EPOCH_PREEMPT);
577 if ((epoch->e_flags & EPOCH_LOCKED) == 0)
578 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
579 "epoch_wait() can be long running");
580 KASSERT(!in_epoch(epoch), ("epoch_wait_preempt() called in the middle "
581 "of an epoch section of the same epoch"));
582 #endif
583 DROP_GIANT();
584 thread_lock(td);
585
586 old_cpu = PCPU_GET(cpuid);
587 old_pinned = td->td_pinned;
588 old_prio = td->td_priority;
589 was_bound = sched_is_bound(td);
590 sched_unbind(td);
591 td->td_pinned = 0;
592 sched_bind(td, old_cpu);
593
594 ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler_preempt,
595 NULL);
596
597 /* restore CPU binding, if any */
598 if (was_bound != 0) {
599 sched_bind(td, old_cpu);
600 } else {
601 /* get thread back to initial CPU, if any */
602 if (old_pinned != 0)
603 sched_bind(td, old_cpu);
604 sched_unbind(td);
605 }
606 /* restore pinned after bind */
607 td->td_pinned = old_pinned;
608
609 /* restore thread priority */
610 sched_prio(td, old_prio);
611 thread_unlock(td);
612 PICKUP_GIANT();
613 KASSERT(td->td_locks == locks,
614 ("%d residual locks held", td->td_locks - locks));
615 }
616
617 static void
epoch_block_handler(struct ck_epoch * g __unused,ck_epoch_record_t * c __unused,void * arg __unused)618 epoch_block_handler(struct ck_epoch *g __unused, ck_epoch_record_t *c __unused,
619 void *arg __unused)
620 {
621 cpu_spinwait();
622 }
623
624 void
epoch_wait(epoch_t epoch)625 epoch_wait(epoch_t epoch)
626 {
627
628 MPASS(cold || epoch != NULL);
629 INIT_CHECK(epoch);
630 MPASS(epoch->e_flags == 0);
631 critical_enter();
632 ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler, NULL);
633 critical_exit();
634 }
635
636 void
epoch_call(epoch_t epoch,epoch_context_t ctx,void (* callback)(epoch_context_t))637 epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t))
638 {
639 epoch_record_t er;
640 ck_epoch_entry_t *cb;
641
642 cb = (void *)ctx;
643
644 MPASS(callback);
645 /* too early in boot to have epoch set up */
646 if (__predict_false(epoch == NULL))
647 goto boottime;
648 #if !defined(EARLY_AP_STARTUP)
649 if (__predict_false(inited < 2))
650 goto boottime;
651 #endif
652
653 critical_enter();
654 *DPCPU_PTR(epoch_cb_count) += 1;
655 er = epoch_currecord(epoch);
656 ck_epoch_call(&er->er_record, cb, (ck_epoch_cb_t *)callback);
657 critical_exit();
658 return;
659 boottime:
660 callback(ctx);
661 }
662
663 static void
epoch_call_task(void * arg __unused)664 epoch_call_task(void *arg __unused)
665 {
666 ck_stack_entry_t *cursor, *head, *next;
667 ck_epoch_record_t *record;
668 epoch_record_t er;
669 epoch_t epoch;
670 ck_stack_t cb_stack;
671 int i, npending, total;
672
673 ck_stack_init(&cb_stack);
674 critical_enter();
675 epoch_enter(global_epoch);
676 for (total = i = 0; i != MAX_EPOCHS; i++) {
677 epoch = epoch_array + i;
678 if (__predict_false(
679 atomic_load_acq_int(&epoch->e_in_use) == 0))
680 continue;
681 er = epoch_currecord(epoch);
682 record = &er->er_record;
683 if ((npending = record->n_pending) == 0)
684 continue;
685 ck_epoch_poll_deferred(record, &cb_stack);
686 total += npending - record->n_pending;
687 }
688 epoch_exit(global_epoch);
689 *DPCPU_PTR(epoch_cb_count) -= total;
690 critical_exit();
691
692 counter_u64_add(epoch_call_count, total);
693 counter_u64_add(epoch_call_task_count, 1);
694
695 head = ck_stack_batch_pop_npsc(&cb_stack);
696 for (cursor = head; cursor != NULL; cursor = next) {
697 struct ck_epoch_entry *entry =
698 ck_epoch_entry_container(cursor);
699
700 next = CK_STACK_NEXT(cursor);
701 entry->function(entry);
702 }
703 }
704
705 static int
in_epoch_verbose_preempt(epoch_t epoch,int dump_onfail)706 in_epoch_verbose_preempt(epoch_t epoch, int dump_onfail)
707 {
708 epoch_record_t er;
709 struct epoch_tracker *tdwait;
710 struct thread *td;
711
712 MPASS(epoch != NULL);
713 MPASS((epoch->e_flags & EPOCH_PREEMPT) != 0);
714 td = curthread;
715 if (td->td_epochnest == 0)
716 return (0);
717 critical_enter();
718 er = epoch_currecord(epoch);
719 TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link)
720 if (tdwait->et_td == td) {
721 critical_exit();
722 return (1);
723 }
724 #ifdef INVARIANTS
725 if (dump_onfail) {
726 MPASS(td->td_pinned);
727 printf("cpu: %d id: %d\n", curcpu, td->td_tid);
728 TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link)
729 printf("td_tid: %d ", tdwait->et_td->td_tid);
730 printf("\n");
731 }
732 #endif
733 critical_exit();
734 return (0);
735 }
736
737 #ifdef INVARIANTS
738 static void
epoch_assert_nocpu(epoch_t epoch,struct thread * td)739 epoch_assert_nocpu(epoch_t epoch, struct thread *td)
740 {
741 epoch_record_t er;
742 int cpu;
743 bool crit;
744
745 crit = td->td_critnest > 0;
746
747 /* Check for a critical section mishap. */
748 CPU_FOREACH(cpu) {
749 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
750 KASSERT(er->er_td != td,
751 ("%s critical section in epoch from cpu %d",
752 (crit ? "exited" : "re-entered"), cpu));
753 }
754 }
755 #else
756 #define epoch_assert_nocpu(e, td)
757 #endif
758
759 int
in_epoch_verbose(epoch_t epoch,int dump_onfail)760 in_epoch_verbose(epoch_t epoch, int dump_onfail)
761 {
762 epoch_record_t er;
763 struct thread *td;
764
765 if (__predict_false((epoch) == NULL))
766 return (0);
767 if ((epoch->e_flags & EPOCH_PREEMPT) != 0)
768 return (in_epoch_verbose_preempt(epoch, dump_onfail));
769
770 /*
771 * The thread being in a critical section is a necessary
772 * condition to be correctly inside a non-preemptible epoch,
773 * so it's definitely not in this epoch.
774 */
775 td = curthread;
776 if (td->td_critnest == 0) {
777 epoch_assert_nocpu(epoch, td);
778 return (0);
779 }
780
781 /*
782 * The current cpu is in a critical section, so the epoch record will be
783 * stable for the rest of this function. Knowing that the record is not
784 * active is sufficient for knowing whether we're in this epoch or not,
785 * since it's a pcpu record.
786 */
787 er = epoch_currecord(epoch);
788 if (er->er_record.active == 0) {
789 epoch_assert_nocpu(epoch, td);
790 return (0);
791 }
792
793 MPASS(er->er_td == td);
794 return (1);
795 }
796
797 int
in_epoch(epoch_t epoch)798 in_epoch(epoch_t epoch)
799 {
800 return (in_epoch_verbose(epoch, 0));
801 }
802
803 static void
epoch_drain_cb(struct epoch_context * ctx)804 epoch_drain_cb(struct epoch_context *ctx)
805 {
806 struct epoch *epoch =
807 __containerof(ctx, struct epoch_record, er_drain_ctx)->er_parent;
808
809 if (atomic_fetchadd_int(&epoch->e_drain_count, -1) == 1) {
810 mtx_lock(&epoch->e_drain_mtx);
811 wakeup(epoch);
812 mtx_unlock(&epoch->e_drain_mtx);
813 }
814 }
815
816 void
epoch_drain_callbacks(epoch_t epoch)817 epoch_drain_callbacks(epoch_t epoch)
818 {
819 epoch_record_t er;
820 struct thread *td;
821 int was_bound;
822 int old_pinned;
823 int old_cpu;
824 int cpu;
825
826 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
827 "epoch_drain_callbacks() may sleep!");
828
829 /* too early in boot to have epoch set up */
830 if (__predict_false(epoch == NULL))
831 return;
832 #if !defined(EARLY_AP_STARTUP)
833 if (__predict_false(inited < 2))
834 return;
835 #endif
836 DROP_GIANT();
837
838 sx_xlock(&epoch->e_drain_sx);
839 mtx_lock(&epoch->e_drain_mtx);
840
841 td = curthread;
842 thread_lock(td);
843 old_cpu = PCPU_GET(cpuid);
844 old_pinned = td->td_pinned;
845 was_bound = sched_is_bound(td);
846 sched_unbind(td);
847 td->td_pinned = 0;
848
849 CPU_FOREACH(cpu)
850 epoch->e_drain_count++;
851 CPU_FOREACH(cpu) {
852 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
853 sched_bind(td, cpu);
854 epoch_call(epoch, &er->er_drain_ctx, &epoch_drain_cb);
855 }
856
857 /* restore CPU binding, if any */
858 if (was_bound != 0) {
859 sched_bind(td, old_cpu);
860 } else {
861 /* get thread back to initial CPU, if any */
862 if (old_pinned != 0)
863 sched_bind(td, old_cpu);
864 sched_unbind(td);
865 }
866 /* restore pinned after bind */
867 td->td_pinned = old_pinned;
868
869 thread_unlock(td);
870
871 while (epoch->e_drain_count != 0)
872 msleep(epoch, &epoch->e_drain_mtx, PZERO, "EDRAIN", 0);
873
874 mtx_unlock(&epoch->e_drain_mtx);
875 sx_xunlock(&epoch->e_drain_sx);
876
877 PICKUP_GIANT();
878 }
879
880 /* for binary compatibility */
881
882 struct epoch_tracker_KBI {
883 void *datap[3];
884 #ifdef EPOCH_TRACKER_DEBUG
885 int datai[5];
886 #else
887 int datai[1];
888 #endif
889 } __aligned(sizeof(void *));
890
891 CTASSERT(sizeof(struct epoch_tracker_KBI) >= sizeof(struct epoch_tracker));
892
893 void
epoch_enter_preempt_KBI(epoch_t epoch,epoch_tracker_t et)894 epoch_enter_preempt_KBI(epoch_t epoch, epoch_tracker_t et)
895 {
896 epoch_enter_preempt(epoch, et);
897 }
898
899 void
epoch_exit_preempt_KBI(epoch_t epoch,epoch_tracker_t et)900 epoch_exit_preempt_KBI(epoch_t epoch, epoch_tracker_t et)
901 {
902 epoch_exit_preempt(epoch, et);
903 }
904
905 void
epoch_enter_KBI(epoch_t epoch)906 epoch_enter_KBI(epoch_t epoch)
907 {
908 epoch_enter(epoch);
909 }
910
911 void
epoch_exit_KBI(epoch_t epoch)912 epoch_exit_KBI(epoch_t epoch)
913 {
914 epoch_exit(epoch);
915 }
916