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/systm.h> 34 #include <sys/counter.h> 35 #include <sys/epoch.h> 36 #include <sys/gtaskqueue.h> 37 #include <sys/kernel.h> 38 #include <sys/limits.h> 39 #include <sys/lock.h> 40 #include <sys/malloc.h> 41 #include <sys/mutex.h> 42 #include <sys/pcpu.h> 43 #include <sys/proc.h> 44 #include <sys/sched.h> 45 #include <sys/sx.h> 46 #include <sys/smp.h> 47 #include <sys/sysctl.h> 48 #include <sys/turnstile.h> 49 #ifdef EPOCH_TRACE 50 #include <machine/stdarg.h> 51 #include <sys/stack.h> 52 #include <sys/tree.h> 53 #endif 54 #include <vm/vm.h> 55 #include <vm/vm_extern.h> 56 #include <vm/vm_kern.h> 57 #include <vm/uma.h> 58 59 #include <ck_epoch.h> 60 61 #ifdef __amd64__ 62 #define EPOCH_ALIGN CACHE_LINE_SIZE*2 63 #else 64 #define EPOCH_ALIGN CACHE_LINE_SIZE 65 #endif 66 67 TAILQ_HEAD (epoch_tdlist, epoch_tracker); 68 typedef struct epoch_record { 69 ck_epoch_record_t er_record; 70 struct epoch_context er_drain_ctx; 71 struct epoch *er_parent; 72 volatile struct epoch_tdlist er_tdlist; 73 volatile uint32_t er_gen; 74 uint32_t er_cpuid; 75 #ifdef INVARIANTS 76 /* Used to verify record ownership for non-preemptible epochs. */ 77 struct thread *er_td; 78 #endif 79 } __aligned(EPOCH_ALIGN) *epoch_record_t; 80 81 struct epoch { 82 struct ck_epoch e_epoch __aligned(EPOCH_ALIGN); 83 epoch_record_t e_pcpu_record; 84 int e_in_use; 85 int e_flags; 86 struct sx e_drain_sx; 87 struct mtx e_drain_mtx; 88 volatile int e_drain_count; 89 const char *e_name; 90 }; 91 92 /* arbitrary --- needs benchmarking */ 93 #define MAX_ADAPTIVE_SPIN 100 94 #define MAX_EPOCHS 64 95 96 CTASSERT(sizeof(ck_epoch_entry_t) == sizeof(struct epoch_context)); 97 SYSCTL_NODE(_kern, OID_AUTO, epoch, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 98 "epoch information"); 99 SYSCTL_NODE(_kern_epoch, OID_AUTO, stats, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 100 "epoch stats"); 101 102 /* Stats. */ 103 static counter_u64_t block_count; 104 105 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, nblocked, CTLFLAG_RW, 106 &block_count, "# of times a thread was in an epoch when epoch_wait was called"); 107 static counter_u64_t migrate_count; 108 109 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, migrations, CTLFLAG_RW, 110 &migrate_count, "# of times thread was migrated to another CPU in epoch_wait"); 111 static counter_u64_t turnstile_count; 112 113 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, ncontended, CTLFLAG_RW, 114 &turnstile_count, "# of times a thread was blocked on a lock in an epoch during an epoch_wait"); 115 static counter_u64_t switch_count; 116 117 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, switches, CTLFLAG_RW, 118 &switch_count, "# of times a thread voluntarily context switched in epoch_wait"); 119 static counter_u64_t epoch_call_count; 120 121 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_calls, CTLFLAG_RW, 122 &epoch_call_count, "# of times a callback was deferred"); 123 static counter_u64_t epoch_call_task_count; 124 125 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_call_tasks, CTLFLAG_RW, 126 &epoch_call_task_count, "# of times a callback task was run"); 127 128 TAILQ_HEAD (threadlist, thread); 129 130 CK_STACK_CONTAINER(struct ck_epoch_entry, stack_entry, 131 ck_epoch_entry_container) 132 133 static struct epoch epoch_array[MAX_EPOCHS]; 134 135 DPCPU_DEFINE(struct grouptask, epoch_cb_task); 136 DPCPU_DEFINE(int, epoch_cb_count); 137 138 static __read_mostly int inited; 139 __read_mostly epoch_t global_epoch; 140 __read_mostly epoch_t global_epoch_preempt; 141 142 static void epoch_call_task(void *context __unused); 143 static uma_zone_t pcpu_zone_record; 144 145 static struct sx epoch_sx; 146 147 #define EPOCH_LOCK() sx_xlock(&epoch_sx) 148 #define EPOCH_UNLOCK() sx_xunlock(&epoch_sx) 149 150 static epoch_record_t 151 epoch_currecord(epoch_t epoch) 152 { 153 154 return (zpcpu_get(epoch->e_pcpu_record)); 155 } 156 157 #ifdef EPOCH_TRACE 158 struct stackentry { 159 RB_ENTRY(stackentry) se_node; 160 struct stack se_stack; 161 }; 162 163 static int 164 stackentry_compare(struct stackentry *a, struct stackentry *b) 165 { 166 167 if (a->se_stack.depth > b->se_stack.depth) 168 return (1); 169 if (a->se_stack.depth < b->se_stack.depth) 170 return (-1); 171 for (int i = 0; i < a->se_stack.depth; i++) { 172 if (a->se_stack.pcs[i] > b->se_stack.pcs[i]) 173 return (1); 174 if (a->se_stack.pcs[i] < b->se_stack.pcs[i]) 175 return (-1); 176 } 177 178 return (0); 179 } 180 181 RB_HEAD(stacktree, stackentry) epoch_stacks = RB_INITIALIZER(&epoch_stacks); 182 RB_GENERATE_STATIC(stacktree, stackentry, se_node, stackentry_compare); 183 184 static struct mtx epoch_stacks_lock; 185 MTX_SYSINIT(epochstacks, &epoch_stacks_lock, "epoch_stacks", MTX_DEF); 186 187 static bool epoch_trace_stack_print = true; 188 SYSCTL_BOOL(_kern_epoch, OID_AUTO, trace_stack_print, CTLFLAG_RWTUN, 189 &epoch_trace_stack_print, 0, "Print stack traces on epoch reports"); 190 191 static void epoch_trace_report(const char *fmt, ...) __printflike(1, 2); 192 static inline void 193 epoch_trace_report(const char *fmt, ...) 194 { 195 va_list ap; 196 struct stackentry se, *new; 197 198 stack_zero(&se.se_stack); /* XXX: is it really needed? */ 199 stack_save(&se.se_stack); 200 201 /* Tree is never reduced - go lockless. */ 202 if (RB_FIND(stacktree, &epoch_stacks, &se) != NULL) 203 return; 204 205 new = malloc(sizeof(*new), M_STACK, M_NOWAIT); 206 if (new != NULL) { 207 bcopy(&se.se_stack, &new->se_stack, sizeof(struct stack)); 208 209 mtx_lock(&epoch_stacks_lock); 210 new = RB_INSERT(stacktree, &epoch_stacks, new); 211 mtx_unlock(&epoch_stacks_lock); 212 if (new != NULL) 213 free(new, M_STACK); 214 } 215 216 va_start(ap, fmt); 217 (void)vprintf(fmt, ap); 218 va_end(ap); 219 if (epoch_trace_stack_print) 220 stack_print_ddb(&se.se_stack); 221 } 222 223 static inline void 224 epoch_trace_enter(struct thread *td, epoch_t epoch, epoch_tracker_t et, 225 const char *file, int line) 226 { 227 epoch_tracker_t iet; 228 229 SLIST_FOREACH(iet, &td->td_epochs, et_tlink) { 230 if (iet->et_epoch != epoch) 231 continue; 232 epoch_trace_report("Recursively entering epoch %s " 233 "at %s:%d, previously entered at %s:%d\n", 234 epoch->e_name, file, line, 235 iet->et_file, iet->et_line); 236 } 237 et->et_epoch = epoch; 238 et->et_file = file; 239 et->et_line = line; 240 et->et_flags = 0; 241 SLIST_INSERT_HEAD(&td->td_epochs, et, et_tlink); 242 } 243 244 static inline void 245 epoch_trace_exit(struct thread *td, epoch_t epoch, epoch_tracker_t et, 246 const char *file, int line) 247 { 248 249 if (SLIST_FIRST(&td->td_epochs) != et) { 250 epoch_trace_report("Exiting epoch %s in a not nested order " 251 "at %s:%d. Most recently entered %s at %s:%d\n", 252 epoch->e_name, 253 file, line, 254 SLIST_FIRST(&td->td_epochs)->et_epoch->e_name, 255 SLIST_FIRST(&td->td_epochs)->et_file, 256 SLIST_FIRST(&td->td_epochs)->et_line); 257 /* This will panic if et is not anywhere on td_epochs. */ 258 SLIST_REMOVE(&td->td_epochs, et, epoch_tracker, et_tlink); 259 } else 260 SLIST_REMOVE_HEAD(&td->td_epochs, et_tlink); 261 if (et->et_flags & ET_REPORT_EXIT) 262 printf("Td %p exiting epoch %s at %s:%d\n", td, epoch->e_name, 263 file, line); 264 } 265 266 /* Used by assertions that check thread state before going to sleep. */ 267 void 268 epoch_trace_list(struct thread *td) 269 { 270 epoch_tracker_t iet; 271 272 SLIST_FOREACH(iet, &td->td_epochs, et_tlink) 273 printf("Epoch %s entered at %s:%d\n", iet->et_epoch->e_name, 274 iet->et_file, iet->et_line); 275 } 276 277 void 278 epoch_where_report(epoch_t epoch) 279 { 280 epoch_record_t er; 281 struct epoch_tracker *tdwait; 282 283 MPASS(epoch != NULL); 284 MPASS((epoch->e_flags & EPOCH_PREEMPT) != 0); 285 MPASS(!THREAD_CAN_SLEEP()); 286 critical_enter(); 287 er = epoch_currecord(epoch); 288 TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link) 289 if (tdwait->et_td == curthread) 290 break; 291 critical_exit(); 292 if (tdwait != NULL) { 293 tdwait->et_flags |= ET_REPORT_EXIT; 294 printf("Td %p entered epoch %s at %s:%d\n", curthread, 295 epoch->e_name, tdwait->et_file, tdwait->et_line); 296 } 297 } 298 #endif /* EPOCH_TRACE */ 299 300 static void 301 epoch_init(void *arg __unused) 302 { 303 int cpu; 304 305 block_count = counter_u64_alloc(M_WAITOK); 306 migrate_count = counter_u64_alloc(M_WAITOK); 307 turnstile_count = counter_u64_alloc(M_WAITOK); 308 switch_count = counter_u64_alloc(M_WAITOK); 309 epoch_call_count = counter_u64_alloc(M_WAITOK); 310 epoch_call_task_count = counter_u64_alloc(M_WAITOK); 311 312 pcpu_zone_record = uma_zcreate("epoch_record pcpu", 313 sizeof(struct epoch_record), NULL, NULL, NULL, NULL, 314 UMA_ALIGN_PTR, UMA_ZONE_PCPU); 315 CPU_FOREACH(cpu) { 316 GROUPTASK_INIT(DPCPU_ID_PTR(cpu, epoch_cb_task), 0, 317 epoch_call_task, NULL); 318 taskqgroup_attach_cpu(qgroup_softirq, 319 DPCPU_ID_PTR(cpu, epoch_cb_task), NULL, cpu, NULL, NULL, 320 "epoch call task"); 321 } 322 #ifdef EPOCH_TRACE 323 SLIST_INIT(&thread0.td_epochs); 324 #endif 325 sx_init(&epoch_sx, "epoch-sx"); 326 inited = 1; 327 global_epoch = epoch_alloc("Global", 0); 328 global_epoch_preempt = epoch_alloc("Global preemptible", EPOCH_PREEMPT); 329 } 330 SYSINIT(epoch, SI_SUB_EPOCH, SI_ORDER_FIRST, epoch_init, NULL); 331 332 #if !defined(EARLY_AP_STARTUP) 333 static void 334 epoch_init_smp(void *dummy __unused) 335 { 336 inited = 2; 337 } 338 SYSINIT(epoch_smp, SI_SUB_SMP + 1, SI_ORDER_FIRST, epoch_init_smp, NULL); 339 #endif 340 341 static void 342 epoch_ctor(epoch_t epoch) 343 { 344 epoch_record_t er; 345 int cpu; 346 347 epoch->e_pcpu_record = uma_zalloc_pcpu(pcpu_zone_record, M_WAITOK); 348 CPU_FOREACH(cpu) { 349 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu); 350 bzero(er, sizeof(*er)); 351 ck_epoch_register(&epoch->e_epoch, &er->er_record, NULL); 352 TAILQ_INIT((struct threadlist *)(uintptr_t)&er->er_tdlist); 353 er->er_cpuid = cpu; 354 er->er_parent = epoch; 355 } 356 } 357 358 static void 359 epoch_adjust_prio(struct thread *td, u_char prio) 360 { 361 362 thread_lock(td); 363 sched_prio(td, prio); 364 thread_unlock(td); 365 } 366 367 epoch_t 368 epoch_alloc(const char *name, int flags) 369 { 370 epoch_t epoch; 371 int i; 372 373 MPASS(name != NULL); 374 375 if (__predict_false(!inited)) 376 panic("%s called too early in boot", __func__); 377 378 EPOCH_LOCK(); 379 380 /* 381 * Find a free index in the epoch array. If no free index is 382 * found, try to use the index after the last one. 383 */ 384 for (i = 0;; i++) { 385 /* 386 * If too many epochs are currently allocated, 387 * return NULL. 388 */ 389 if (i == MAX_EPOCHS) { 390 epoch = NULL; 391 goto done; 392 } 393 if (epoch_array[i].e_in_use == 0) 394 break; 395 } 396 397 epoch = epoch_array + i; 398 ck_epoch_init(&epoch->e_epoch); 399 epoch_ctor(epoch); 400 epoch->e_flags = flags; 401 epoch->e_name = name; 402 sx_init(&epoch->e_drain_sx, "epoch-drain-sx"); 403 mtx_init(&epoch->e_drain_mtx, "epoch-drain-mtx", NULL, MTX_DEF); 404 405 /* 406 * Set e_in_use last, because when this field is set the 407 * epoch_call_task() function will start scanning this epoch 408 * structure. 409 */ 410 atomic_store_rel_int(&epoch->e_in_use, 1); 411 done: 412 EPOCH_UNLOCK(); 413 return (epoch); 414 } 415 416 void 417 epoch_free(epoch_t epoch) 418 { 419 #ifdef INVARIANTS 420 int cpu; 421 #endif 422 423 EPOCH_LOCK(); 424 425 MPASS(epoch->e_in_use != 0); 426 427 epoch_drain_callbacks(epoch); 428 429 atomic_store_rel_int(&epoch->e_in_use, 0); 430 /* 431 * Make sure the epoch_call_task() function see e_in_use equal 432 * to zero, by calling epoch_wait() on the global_epoch: 433 */ 434 epoch_wait(global_epoch); 435 #ifdef INVARIANTS 436 CPU_FOREACH(cpu) { 437 epoch_record_t er; 438 439 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu); 440 441 /* 442 * Sanity check: none of the records should be in use anymore. 443 * We drained callbacks above and freeing the pcpu records is 444 * imminent. 445 */ 446 MPASS(er->er_td == NULL); 447 MPASS(TAILQ_EMPTY(&er->er_tdlist)); 448 } 449 #endif 450 uma_zfree_pcpu(pcpu_zone_record, epoch->e_pcpu_record); 451 mtx_destroy(&epoch->e_drain_mtx); 452 sx_destroy(&epoch->e_drain_sx); 453 memset(epoch, 0, sizeof(*epoch)); 454 455 EPOCH_UNLOCK(); 456 } 457 458 #define INIT_CHECK(epoch) \ 459 do { \ 460 if (__predict_false((epoch) == NULL)) \ 461 return; \ 462 } while (0) 463 464 void 465 _epoch_enter_preempt(epoch_t epoch, epoch_tracker_t et EPOCH_FILE_LINE) 466 { 467 struct epoch_record *er; 468 struct thread *td; 469 470 MPASS(cold || epoch != NULL); 471 td = curthread; 472 MPASS((vm_offset_t)et >= td->td_kstack && 473 (vm_offset_t)et + sizeof(struct epoch_tracker) <= 474 td->td_kstack + td->td_kstack_pages * PAGE_SIZE); 475 476 INIT_CHECK(epoch); 477 MPASS(epoch->e_flags & EPOCH_PREEMPT); 478 479 #ifdef EPOCH_TRACE 480 epoch_trace_enter(td, epoch, et, file, line); 481 #endif 482 et->et_td = td; 483 THREAD_NO_SLEEPING(); 484 critical_enter(); 485 sched_pin(); 486 et->et_old_priority = td->td_priority; 487 er = epoch_currecord(epoch); 488 /* Record-level tracking is reserved for non-preemptible epochs. */ 489 MPASS(er->er_td == NULL); 490 TAILQ_INSERT_TAIL(&er->er_tdlist, et, et_link); 491 ck_epoch_begin(&er->er_record, &et->et_section); 492 critical_exit(); 493 } 494 495 void 496 epoch_enter(epoch_t epoch) 497 { 498 epoch_record_t er; 499 500 MPASS(cold || epoch != NULL); 501 INIT_CHECK(epoch); 502 critical_enter(); 503 er = epoch_currecord(epoch); 504 #ifdef INVARIANTS 505 if (er->er_record.active == 0) { 506 MPASS(er->er_td == NULL); 507 er->er_td = curthread; 508 } else { 509 /* We've recursed, just make sure our accounting isn't wrong. */ 510 MPASS(er->er_td == curthread); 511 } 512 #endif 513 ck_epoch_begin(&er->er_record, NULL); 514 } 515 516 void 517 _epoch_exit_preempt(epoch_t epoch, epoch_tracker_t et EPOCH_FILE_LINE) 518 { 519 struct epoch_record *er; 520 struct thread *td; 521 522 INIT_CHECK(epoch); 523 td = curthread; 524 critical_enter(); 525 sched_unpin(); 526 THREAD_SLEEPING_OK(); 527 er = epoch_currecord(epoch); 528 MPASS(epoch->e_flags & EPOCH_PREEMPT); 529 MPASS(et != NULL); 530 MPASS(et->et_td == td); 531 #ifdef INVARIANTS 532 et->et_td = (void*)0xDEADBEEF; 533 /* Record-level tracking is reserved for non-preemptible epochs. */ 534 MPASS(er->er_td == NULL); 535 #endif 536 ck_epoch_end(&er->er_record, &et->et_section); 537 TAILQ_REMOVE(&er->er_tdlist, et, et_link); 538 er->er_gen++; 539 if (__predict_false(et->et_old_priority != td->td_priority)) 540 epoch_adjust_prio(td, et->et_old_priority); 541 critical_exit(); 542 #ifdef EPOCH_TRACE 543 epoch_trace_exit(td, epoch, et, file, line); 544 #endif 545 } 546 547 void 548 epoch_exit(epoch_t epoch) 549 { 550 epoch_record_t er; 551 552 INIT_CHECK(epoch); 553 er = epoch_currecord(epoch); 554 ck_epoch_end(&er->er_record, NULL); 555 #ifdef INVARIANTS 556 MPASS(er->er_td == curthread); 557 if (er->er_record.active == 0) 558 er->er_td = NULL; 559 #endif 560 critical_exit(); 561 } 562 563 /* 564 * epoch_block_handler_preempt() is a callback from the CK code when another 565 * thread is currently in an epoch section. 566 */ 567 static void 568 epoch_block_handler_preempt(struct ck_epoch *global __unused, 569 ck_epoch_record_t *cr, void *arg __unused) 570 { 571 epoch_record_t record; 572 struct thread *td, *owner, *curwaittd; 573 struct epoch_tracker *tdwait; 574 struct turnstile *ts; 575 struct lock_object *lock; 576 int spincount, gen; 577 int locksheld __unused; 578 579 record = __containerof(cr, struct epoch_record, er_record); 580 td = curthread; 581 locksheld = td->td_locks; 582 spincount = 0; 583 counter_u64_add(block_count, 1); 584 /* 585 * We lost a race and there's no longer any threads 586 * on the CPU in an epoch section. 587 */ 588 if (TAILQ_EMPTY(&record->er_tdlist)) 589 return; 590 591 if (record->er_cpuid != curcpu) { 592 /* 593 * If the head of the list is running, we can wait for it 594 * to remove itself from the list and thus save us the 595 * overhead of a migration 596 */ 597 gen = record->er_gen; 598 thread_unlock(td); 599 /* 600 * We can't actually check if the waiting thread is running 601 * so we simply poll for it to exit before giving up and 602 * migrating. 603 */ 604 do { 605 cpu_spinwait(); 606 } while (!TAILQ_EMPTY(&record->er_tdlist) && 607 gen == record->er_gen && 608 spincount++ < MAX_ADAPTIVE_SPIN); 609 thread_lock(td); 610 /* 611 * If the generation has changed we can poll again 612 * otherwise we need to migrate. 613 */ 614 if (gen != record->er_gen) 615 return; 616 /* 617 * Being on the same CPU as that of the record on which 618 * we need to wait allows us access to the thread 619 * list associated with that CPU. We can then examine the 620 * oldest thread in the queue and wait on its turnstile 621 * until it resumes and so on until a grace period 622 * elapses. 623 * 624 */ 625 counter_u64_add(migrate_count, 1); 626 sched_bind(td, record->er_cpuid); 627 /* 628 * At this point we need to return to the ck code 629 * to scan to see if a grace period has elapsed. 630 * We can't move on to check the thread list, because 631 * in the meantime new threads may have arrived that 632 * in fact belong to a different epoch. 633 */ 634 return; 635 } 636 /* 637 * Try to find a thread in an epoch section on this CPU 638 * waiting on a turnstile. Otherwise find the lowest 639 * priority thread (highest prio value) and drop our priority 640 * to match to allow it to run. 641 */ 642 TAILQ_FOREACH(tdwait, &record->er_tdlist, et_link) { 643 /* 644 * Propagate our priority to any other waiters to prevent us 645 * from starving them. They will have their original priority 646 * restore on exit from epoch_wait(). 647 */ 648 curwaittd = tdwait->et_td; 649 if (!TD_IS_INHIBITED(curwaittd) && curwaittd->td_priority > td->td_priority) { 650 critical_enter(); 651 thread_unlock(td); 652 thread_lock(curwaittd); 653 sched_prio(curwaittd, td->td_priority); 654 thread_unlock(curwaittd); 655 thread_lock(td); 656 critical_exit(); 657 } 658 if (TD_IS_INHIBITED(curwaittd) && TD_ON_LOCK(curwaittd) && 659 ((ts = curwaittd->td_blocked) != NULL)) { 660 /* 661 * We unlock td to allow turnstile_wait to reacquire 662 * the thread lock. Before unlocking it we enter a 663 * critical section to prevent preemption after we 664 * reenable interrupts by dropping the thread lock in 665 * order to prevent curwaittd from getting to run. 666 */ 667 critical_enter(); 668 thread_unlock(td); 669 670 if (turnstile_lock(ts, &lock, &owner)) { 671 if (ts == curwaittd->td_blocked) { 672 MPASS(TD_IS_INHIBITED(curwaittd) && 673 TD_ON_LOCK(curwaittd)); 674 critical_exit(); 675 turnstile_wait(ts, owner, 676 curwaittd->td_tsqueue); 677 counter_u64_add(turnstile_count, 1); 678 thread_lock(td); 679 return; 680 } 681 turnstile_unlock(ts, lock); 682 } 683 thread_lock(td); 684 critical_exit(); 685 KASSERT(td->td_locks == locksheld, 686 ("%d extra locks held", td->td_locks - locksheld)); 687 } 688 } 689 /* 690 * We didn't find any threads actually blocked on a lock 691 * so we have nothing to do except context switch away. 692 */ 693 counter_u64_add(switch_count, 1); 694 mi_switch(SW_VOL | SWT_RELINQUISH); 695 /* 696 * It is important the thread lock is dropped while yielding 697 * to allow other threads to acquire the lock pointed to by 698 * TDQ_LOCKPTR(td). Currently mi_switch() will unlock the 699 * thread lock before returning. Else a deadlock like 700 * situation might happen. 701 */ 702 thread_lock(td); 703 } 704 705 void 706 epoch_wait_preempt(epoch_t epoch) 707 { 708 struct thread *td; 709 int was_bound; 710 int old_cpu; 711 int old_pinned; 712 u_char old_prio; 713 int locks __unused; 714 715 MPASS(cold || epoch != NULL); 716 INIT_CHECK(epoch); 717 td = curthread; 718 #ifdef INVARIANTS 719 locks = curthread->td_locks; 720 MPASS(epoch->e_flags & EPOCH_PREEMPT); 721 if ((epoch->e_flags & EPOCH_LOCKED) == 0) 722 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, 723 "epoch_wait() can be long running"); 724 KASSERT(!in_epoch(epoch), ("epoch_wait_preempt() called in the middle " 725 "of an epoch section of the same epoch")); 726 #endif 727 DROP_GIANT(); 728 thread_lock(td); 729 730 old_cpu = PCPU_GET(cpuid); 731 old_pinned = td->td_pinned; 732 old_prio = td->td_priority; 733 was_bound = sched_is_bound(td); 734 sched_unbind(td); 735 td->td_pinned = 0; 736 sched_bind(td, old_cpu); 737 738 ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler_preempt, 739 NULL); 740 741 /* restore CPU binding, if any */ 742 if (was_bound != 0) { 743 sched_bind(td, old_cpu); 744 } else { 745 /* get thread back to initial CPU, if any */ 746 if (old_pinned != 0) 747 sched_bind(td, old_cpu); 748 sched_unbind(td); 749 } 750 /* restore pinned after bind */ 751 td->td_pinned = old_pinned; 752 753 /* restore thread priority */ 754 sched_prio(td, old_prio); 755 thread_unlock(td); 756 PICKUP_GIANT(); 757 KASSERT(td->td_locks == locks, 758 ("%d residual locks held", td->td_locks - locks)); 759 } 760 761 static void 762 epoch_block_handler(struct ck_epoch *g __unused, ck_epoch_record_t *c __unused, 763 void *arg __unused) 764 { 765 cpu_spinwait(); 766 } 767 768 void 769 epoch_wait(epoch_t epoch) 770 { 771 772 MPASS(cold || epoch != NULL); 773 INIT_CHECK(epoch); 774 MPASS(epoch->e_flags == 0); 775 critical_enter(); 776 ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler, NULL); 777 critical_exit(); 778 } 779 780 void 781 epoch_call(epoch_t epoch, epoch_callback_t callback, epoch_context_t ctx) 782 { 783 epoch_record_t er; 784 ck_epoch_entry_t *cb; 785 786 cb = (void *)ctx; 787 788 MPASS(callback); 789 /* too early in boot to have epoch set up */ 790 if (__predict_false(epoch == NULL)) 791 goto boottime; 792 #if !defined(EARLY_AP_STARTUP) 793 if (__predict_false(inited < 2)) 794 goto boottime; 795 #endif 796 797 critical_enter(); 798 *DPCPU_PTR(epoch_cb_count) += 1; 799 er = epoch_currecord(epoch); 800 ck_epoch_call(&er->er_record, cb, (ck_epoch_cb_t *)callback); 801 critical_exit(); 802 return; 803 boottime: 804 callback(ctx); 805 } 806 807 static void 808 epoch_call_task(void *arg __unused) 809 { 810 ck_stack_entry_t *cursor, *head, *next; 811 ck_epoch_record_t *record; 812 epoch_record_t er; 813 epoch_t epoch; 814 ck_stack_t cb_stack; 815 int i, npending, total; 816 817 ck_stack_init(&cb_stack); 818 critical_enter(); 819 epoch_enter(global_epoch); 820 for (total = i = 0; i != MAX_EPOCHS; i++) { 821 epoch = epoch_array + i; 822 if (__predict_false( 823 atomic_load_acq_int(&epoch->e_in_use) == 0)) 824 continue; 825 er = epoch_currecord(epoch); 826 record = &er->er_record; 827 if ((npending = record->n_pending) == 0) 828 continue; 829 ck_epoch_poll_deferred(record, &cb_stack); 830 total += npending - record->n_pending; 831 } 832 epoch_exit(global_epoch); 833 *DPCPU_PTR(epoch_cb_count) -= total; 834 critical_exit(); 835 836 counter_u64_add(epoch_call_count, total); 837 counter_u64_add(epoch_call_task_count, 1); 838 839 head = ck_stack_batch_pop_npsc(&cb_stack); 840 for (cursor = head; cursor != NULL; cursor = next) { 841 struct ck_epoch_entry *entry = 842 ck_epoch_entry_container(cursor); 843 844 next = CK_STACK_NEXT(cursor); 845 entry->function(entry); 846 } 847 } 848 849 static int 850 in_epoch_verbose_preempt(epoch_t epoch, int dump_onfail) 851 { 852 epoch_record_t er; 853 struct epoch_tracker *tdwait; 854 struct thread *td; 855 856 MPASS(epoch != NULL); 857 MPASS((epoch->e_flags & EPOCH_PREEMPT) != 0); 858 td = curthread; 859 if (THREAD_CAN_SLEEP()) 860 return (0); 861 critical_enter(); 862 er = epoch_currecord(epoch); 863 TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link) 864 if (tdwait->et_td == td) { 865 critical_exit(); 866 return (1); 867 } 868 #ifdef INVARIANTS 869 if (dump_onfail) { 870 MPASS(td->td_pinned); 871 printf("cpu: %d id: %d\n", curcpu, td->td_tid); 872 TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link) 873 printf("td_tid: %d ", tdwait->et_td->td_tid); 874 printf("\n"); 875 } 876 #endif 877 critical_exit(); 878 return (0); 879 } 880 881 #ifdef INVARIANTS 882 static void 883 epoch_assert_nocpu(epoch_t epoch, struct thread *td) 884 { 885 epoch_record_t er; 886 int cpu; 887 bool crit; 888 889 crit = td->td_critnest > 0; 890 891 /* Check for a critical section mishap. */ 892 CPU_FOREACH(cpu) { 893 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu); 894 KASSERT(er->er_td != td, 895 ("%s critical section in epoch '%s', from cpu %d", 896 (crit ? "exited" : "re-entered"), epoch->e_name, cpu)); 897 } 898 } 899 #else 900 #define epoch_assert_nocpu(e, td) do {} while (0) 901 #endif 902 903 int 904 in_epoch_verbose(epoch_t epoch, int dump_onfail) 905 { 906 epoch_record_t er; 907 struct thread *td; 908 909 if (__predict_false((epoch) == NULL)) 910 return (0); 911 if ((epoch->e_flags & EPOCH_PREEMPT) != 0) 912 return (in_epoch_verbose_preempt(epoch, dump_onfail)); 913 914 /* 915 * The thread being in a critical section is a necessary 916 * condition to be correctly inside a non-preemptible epoch, 917 * so it's definitely not in this epoch. 918 */ 919 td = curthread; 920 if (td->td_critnest == 0) { 921 epoch_assert_nocpu(epoch, td); 922 return (0); 923 } 924 925 /* 926 * The current cpu is in a critical section, so the epoch record will be 927 * stable for the rest of this function. Knowing that the record is not 928 * active is sufficient for knowing whether we're in this epoch or not, 929 * since it's a pcpu record. 930 */ 931 er = epoch_currecord(epoch); 932 if (er->er_record.active == 0) { 933 epoch_assert_nocpu(epoch, td); 934 return (0); 935 } 936 937 MPASS(er->er_td == td); 938 return (1); 939 } 940 941 int 942 in_epoch(epoch_t epoch) 943 { 944 return (in_epoch_verbose(epoch, 0)); 945 } 946 947 static void 948 epoch_drain_cb(struct epoch_context *ctx) 949 { 950 struct epoch *epoch = 951 __containerof(ctx, struct epoch_record, er_drain_ctx)->er_parent; 952 953 if (atomic_fetchadd_int(&epoch->e_drain_count, -1) == 1) { 954 mtx_lock(&epoch->e_drain_mtx); 955 wakeup(epoch); 956 mtx_unlock(&epoch->e_drain_mtx); 957 } 958 } 959 960 void 961 epoch_drain_callbacks(epoch_t epoch) 962 { 963 epoch_record_t er; 964 struct thread *td; 965 int was_bound; 966 int old_pinned; 967 int old_cpu; 968 int cpu; 969 970 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, 971 "epoch_drain_callbacks() may sleep!"); 972 973 /* too early in boot to have epoch set up */ 974 if (__predict_false(epoch == NULL)) 975 return; 976 #if !defined(EARLY_AP_STARTUP) 977 if (__predict_false(inited < 2)) 978 return; 979 #endif 980 DROP_GIANT(); 981 982 sx_xlock(&epoch->e_drain_sx); 983 mtx_lock(&epoch->e_drain_mtx); 984 985 td = curthread; 986 thread_lock(td); 987 old_cpu = PCPU_GET(cpuid); 988 old_pinned = td->td_pinned; 989 was_bound = sched_is_bound(td); 990 sched_unbind(td); 991 td->td_pinned = 0; 992 993 CPU_FOREACH(cpu) 994 epoch->e_drain_count++; 995 CPU_FOREACH(cpu) { 996 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu); 997 sched_bind(td, cpu); 998 epoch_call(epoch, &epoch_drain_cb, &er->er_drain_ctx); 999 } 1000 1001 /* restore CPU binding, if any */ 1002 if (was_bound != 0) { 1003 sched_bind(td, old_cpu); 1004 } else { 1005 /* get thread back to initial CPU, if any */ 1006 if (old_pinned != 0) 1007 sched_bind(td, old_cpu); 1008 sched_unbind(td); 1009 } 1010 /* restore pinned after bind */ 1011 td->td_pinned = old_pinned; 1012 1013 thread_unlock(td); 1014 1015 while (epoch->e_drain_count != 0) 1016 msleep(epoch, &epoch->e_drain_mtx, PZERO, "EDRAIN", 0); 1017 1018 mtx_unlock(&epoch->e_drain_mtx); 1019 sx_xunlock(&epoch->e_drain_sx); 1020 1021 PICKUP_GIANT(); 1022 } 1023