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sys/kern/subr_epoch.c
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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("$FreeBSD$"); 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 798 in_epoch(epoch_t epoch) 799 { 800 return (in_epoch_verbose(epoch, 0)); 801 } 802 803 static void 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 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 894 epoch_enter_preempt_KBI(epoch_t epoch, epoch_tracker_t et) 895 { 896 epoch_enter_preempt(epoch, et); 897 } 898 899 void 900 epoch_exit_preempt_KBI(epoch_t epoch, epoch_tracker_t et) 901 { 902 epoch_exit_preempt(epoch, et); 903 } 904 905 void 906 epoch_enter_KBI(epoch_t epoch) 907 { 908 epoch_enter(epoch); 909 } 910 911 void 912 epoch_exit_KBI(epoch_t epoch) 913 { 914 epoch_exit(epoch); 915 }
Cache object: 0102ae5a9b8eb7ead6eb95e31876cffc
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