1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 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/param.h> 30 #include <sys/systm.h> 31 #include <sys/counter.h> 32 #include <sys/epoch.h> 33 #include <sys/gtaskqueue.h> 34 #include <sys/kernel.h> 35 #include <sys/limits.h> 36 #include <sys/lock.h> 37 #include <sys/malloc.h> 38 #include <sys/mutex.h> 39 #include <sys/pcpu.h> 40 #include <sys/proc.h> 41 #include <sys/sched.h> 42 #include <sys/sx.h> 43 #include <sys/smp.h> 44 #include <sys/sysctl.h> 45 #include <sys/turnstile.h> 46 #ifdef EPOCH_TRACE 47 #include <machine/stdarg.h> 48 #include <sys/stack.h> 49 #include <sys/tree.h> 50 #endif 51 #include <vm/vm.h> 52 #include <vm/vm_extern.h> 53 #include <vm/vm_kern.h> 54 #include <vm/uma.h> 55 56 #include <machine/stack.h> 57 58 #include <ck_epoch.h> 59 60 #ifdef __amd64__ 61 #define EPOCH_ALIGN CACHE_LINE_SIZE*2 62 #else 63 #define EPOCH_ALIGN CACHE_LINE_SIZE 64 #endif 65 66 TAILQ_HEAD (epoch_tdlist, epoch_tracker); 67 typedef struct epoch_record { 68 ck_epoch_record_t er_record; 69 struct epoch_context er_drain_ctx; 70 struct epoch *er_parent; 71 volatile struct epoch_tdlist er_tdlist; 72 volatile uint32_t er_gen; 73 uint32_t er_cpuid; 74 #ifdef INVARIANTS 75 /* Used to verify record ownership for non-preemptible epochs. */ 76 struct thread *er_td; 77 #endif 78 } __aligned(EPOCH_ALIGN) *epoch_record_t; 79 80 struct epoch { 81 struct ck_epoch e_epoch __aligned(EPOCH_ALIGN); 82 epoch_record_t e_pcpu_record; 83 int e_in_use; 84 int e_flags; 85 struct sx e_drain_sx; 86 struct mtx e_drain_mtx; 87 volatile int e_drain_count; 88 const char *e_name; 89 }; 90 91 /* arbitrary --- needs benchmarking */ 92 #define MAX_ADAPTIVE_SPIN 100 93 #define MAX_EPOCHS 64 94 95 CTASSERT(sizeof(ck_epoch_entry_t) == sizeof(struct epoch_context)); 96 SYSCTL_NODE(_kern, OID_AUTO, epoch, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 97 "epoch information"); 98 SYSCTL_NODE(_kern_epoch, OID_AUTO, stats, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 99 "epoch stats"); 100 101 /* Stats. */ 102 static counter_u64_t block_count; 103 104 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, nblocked, CTLFLAG_RW, 105 &block_count, "# of times a thread was in an epoch when epoch_wait was called"); 106 static counter_u64_t migrate_count; 107 108 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, migrations, CTLFLAG_RW, 109 &migrate_count, "# of times thread was migrated to another CPU in epoch_wait"); 110 static counter_u64_t turnstile_count; 111 112 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, ncontended, CTLFLAG_RW, 113 &turnstile_count, "# of times a thread was blocked on a lock in an epoch during an epoch_wait"); 114 static counter_u64_t switch_count; 115 116 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, switches, CTLFLAG_RW, 117 &switch_count, "# of times a thread voluntarily context switched in epoch_wait"); 118 static counter_u64_t epoch_call_count; 119 120 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_calls, CTLFLAG_RW, 121 &epoch_call_count, "# of times a callback was deferred"); 122 static counter_u64_t epoch_call_task_count; 123 124 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_call_tasks, CTLFLAG_RW, 125 &epoch_call_task_count, "# of times a callback task was run"); 126 127 TAILQ_HEAD (threadlist, thread); 128 129 CK_STACK_CONTAINER(struct ck_epoch_entry, stack_entry, 130 ck_epoch_entry_container) 131 132 static struct epoch epoch_array[MAX_EPOCHS]; 133 134 DPCPU_DEFINE(struct grouptask, epoch_cb_task); 135 DPCPU_DEFINE(int, epoch_cb_count); 136 137 static __read_mostly int inited; 138 __read_mostly epoch_t global_epoch; 139 __read_mostly epoch_t global_epoch_preempt; 140 141 static void epoch_call_task(void *context __unused); 142 static uma_zone_t pcpu_zone_record; 143 144 static struct sx epoch_sx; 145 146 #define EPOCH_LOCK() sx_xlock(&epoch_sx) 147 #define EPOCH_UNLOCK() sx_xunlock(&epoch_sx) 148 149 static epoch_record_t 150 epoch_currecord(epoch_t epoch) 151 { 152 153 return (zpcpu_get(epoch->e_pcpu_record)); 154 } 155 156 #ifdef EPOCH_TRACE 157 struct stackentry { 158 RB_ENTRY(stackentry) se_node; 159 struct stack se_stack; 160 }; 161 162 static int 163 stackentry_compare(struct stackentry *a, struct stackentry *b) 164 { 165 166 if (a->se_stack.depth > b->se_stack.depth) 167 return (1); 168 if (a->se_stack.depth < b->se_stack.depth) 169 return (-1); 170 for (int i = 0; i < a->se_stack.depth; i++) { 171 if (a->se_stack.pcs[i] > b->se_stack.pcs[i]) 172 return (1); 173 if (a->se_stack.pcs[i] < b->se_stack.pcs[i]) 174 return (-1); 175 } 176 177 return (0); 178 } 179 180 RB_HEAD(stacktree, stackentry) epoch_stacks = RB_INITIALIZER(&epoch_stacks); 181 RB_GENERATE_STATIC(stacktree, stackentry, se_node, stackentry_compare); 182 183 static struct mtx epoch_stacks_lock; 184 MTX_SYSINIT(epochstacks, &epoch_stacks_lock, "epoch_stacks", MTX_DEF); 185 186 static bool epoch_trace_stack_print = true; 187 SYSCTL_BOOL(_kern_epoch, OID_AUTO, trace_stack_print, CTLFLAG_RWTUN, 188 &epoch_trace_stack_print, 0, "Print stack traces on epoch reports"); 189 190 static void epoch_trace_report(const char *fmt, ...) __printflike(1, 2); 191 static inline void 192 epoch_trace_report(const char *fmt, ...) 193 { 194 va_list ap; 195 struct stackentry se, *new; 196 197 stack_save(&se.se_stack); 198 199 /* Tree is never reduced - go lockless. */ 200 if (RB_FIND(stacktree, &epoch_stacks, &se) != NULL) 201 return; 202 203 new = malloc(sizeof(*new), M_STACK, M_NOWAIT); 204 if (new != NULL) { 205 bcopy(&se.se_stack, &new->se_stack, sizeof(struct stack)); 206 207 mtx_lock(&epoch_stacks_lock); 208 new = RB_INSERT(stacktree, &epoch_stacks, new); 209 mtx_unlock(&epoch_stacks_lock); 210 if (new != NULL) 211 free(new, M_STACK); 212 } 213 214 va_start(ap, fmt); 215 (void)vprintf(fmt, ap); 216 va_end(ap); 217 if (epoch_trace_stack_print) 218 stack_print_ddb(&se.se_stack); 219 } 220 221 static inline void 222 epoch_trace_enter(struct thread *td, epoch_t epoch, epoch_tracker_t et, 223 const char *file, int line) 224 { 225 epoch_tracker_t iet; 226 227 SLIST_FOREACH(iet, &td->td_epochs, et_tlink) { 228 if (iet->et_epoch != epoch) 229 continue; 230 epoch_trace_report("Recursively entering epoch %s " 231 "at %s:%d, previously entered at %s:%d\n", 232 epoch->e_name, file, line, 233 iet->et_file, iet->et_line); 234 } 235 et->et_epoch = epoch; 236 et->et_file = file; 237 et->et_line = line; 238 et->et_flags = 0; 239 SLIST_INSERT_HEAD(&td->td_epochs, et, et_tlink); 240 } 241 242 static inline void 243 epoch_trace_exit(struct thread *td, epoch_t epoch, epoch_tracker_t et, 244 const char *file, int line) 245 { 246 247 if (SLIST_FIRST(&td->td_epochs) != et) { 248 epoch_trace_report("Exiting epoch %s in a not nested order " 249 "at %s:%d. Most recently entered %s at %s:%d\n", 250 epoch->e_name, 251 file, line, 252 SLIST_FIRST(&td->td_epochs)->et_epoch->e_name, 253 SLIST_FIRST(&td->td_epochs)->et_file, 254 SLIST_FIRST(&td->td_epochs)->et_line); 255 /* This will panic if et is not anywhere on td_epochs. */ 256 SLIST_REMOVE(&td->td_epochs, et, epoch_tracker, et_tlink); 257 } else 258 SLIST_REMOVE_HEAD(&td->td_epochs, et_tlink); 259 if (et->et_flags & ET_REPORT_EXIT) 260 printf("Td %p exiting epoch %s at %s:%d\n", td, epoch->e_name, 261 file, line); 262 } 263 264 /* Used by assertions that check thread state before going to sleep. */ 265 void 266 epoch_trace_list(struct thread *td) 267 { 268 epoch_tracker_t iet; 269 270 SLIST_FOREACH(iet, &td->td_epochs, et_tlink) 271 printf("Epoch %s entered at %s:%d\n", iet->et_epoch->e_name, 272 iet->et_file, iet->et_line); 273 } 274 275 void 276 epoch_where_report(epoch_t epoch) 277 { 278 epoch_record_t er; 279 struct epoch_tracker *tdwait; 280 281 MPASS(epoch != NULL); 282 MPASS((epoch->e_flags & EPOCH_PREEMPT) != 0); 283 MPASS(!THREAD_CAN_SLEEP()); 284 critical_enter(); 285 er = epoch_currecord(epoch); 286 TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link) 287 if (tdwait->et_td == curthread) 288 break; 289 critical_exit(); 290 if (tdwait != NULL) { 291 tdwait->et_flags |= ET_REPORT_EXIT; 292 printf("Td %p entered epoch %s at %s:%d\n", curthread, 293 epoch->e_name, tdwait->et_file, tdwait->et_line); 294 } 295 } 296 #endif /* EPOCH_TRACE */ 297 298 static void 299 epoch_init(void *arg __unused) 300 { 301 int cpu; 302 303 block_count = counter_u64_alloc(M_WAITOK); 304 migrate_count = counter_u64_alloc(M_WAITOK); 305 turnstile_count = counter_u64_alloc(M_WAITOK); 306 switch_count = counter_u64_alloc(M_WAITOK); 307 epoch_call_count = counter_u64_alloc(M_WAITOK); 308 epoch_call_task_count = counter_u64_alloc(M_WAITOK); 309 310 pcpu_zone_record = uma_zcreate("epoch_record pcpu", 311 sizeof(struct epoch_record), NULL, NULL, NULL, NULL, 312 UMA_ALIGN_PTR, UMA_ZONE_PCPU); 313 CPU_FOREACH(cpu) { 314 GROUPTASK_INIT(DPCPU_ID_PTR(cpu, epoch_cb_task), 0, 315 epoch_call_task, NULL); 316 taskqgroup_attach_cpu(qgroup_softirq, 317 DPCPU_ID_PTR(cpu, epoch_cb_task), NULL, cpu, NULL, NULL, 318 "epoch call task"); 319 } 320 #ifdef EPOCH_TRACE 321 SLIST_INIT(&thread0.td_epochs); 322 #endif 323 sx_init(&epoch_sx, "epoch-sx"); 324 inited = 1; 325 global_epoch = epoch_alloc("Global", 0); 326 global_epoch_preempt = epoch_alloc("Global preemptible", EPOCH_PREEMPT); 327 } 328 SYSINIT(epoch, SI_SUB_EPOCH, SI_ORDER_FIRST, epoch_init, NULL); 329 330 #if !defined(EARLY_AP_STARTUP) 331 static void 332 epoch_init_smp(void *dummy __unused) 333 { 334 inited = 2; 335 } 336 SYSINIT(epoch_smp, SI_SUB_SMP + 1, SI_ORDER_FIRST, epoch_init_smp, NULL); 337 #endif 338 339 static void 340 epoch_ctor(epoch_t epoch) 341 { 342 epoch_record_t er; 343 int cpu; 344 345 epoch->e_pcpu_record = uma_zalloc_pcpu(pcpu_zone_record, M_WAITOK); 346 CPU_FOREACH(cpu) { 347 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu); 348 bzero(er, sizeof(*er)); 349 ck_epoch_register(&epoch->e_epoch, &er->er_record, NULL); 350 TAILQ_INIT((struct threadlist *)(uintptr_t)&er->er_tdlist); 351 er->er_cpuid = cpu; 352 er->er_parent = epoch; 353 } 354 } 355 356 static void 357 epoch_adjust_prio(struct thread *td, u_char prio) 358 { 359 360 thread_lock(td); 361 sched_prio(td, prio); 362 thread_unlock(td); 363 } 364 365 epoch_t 366 epoch_alloc(const char *name, int flags) 367 { 368 epoch_t epoch; 369 int i; 370 371 MPASS(name != NULL); 372 373 if (__predict_false(!inited)) 374 panic("%s called too early in boot", __func__); 375 376 EPOCH_LOCK(); 377 378 /* 379 * Find a free index in the epoch array. If no free index is 380 * found, try to use the index after the last one. 381 */ 382 for (i = 0;; i++) { 383 /* 384 * If too many epochs are currently allocated, 385 * return NULL. 386 */ 387 if (i == MAX_EPOCHS) { 388 epoch = NULL; 389 goto done; 390 } 391 if (epoch_array[i].e_in_use == 0) 392 break; 393 } 394 395 epoch = epoch_array + i; 396 ck_epoch_init(&epoch->e_epoch); 397 epoch_ctor(epoch); 398 epoch->e_flags = flags; 399 epoch->e_name = name; 400 sx_init(&epoch->e_drain_sx, "epoch-drain-sx"); 401 mtx_init(&epoch->e_drain_mtx, "epoch-drain-mtx", NULL, MTX_DEF); 402 403 /* 404 * Set e_in_use last, because when this field is set the 405 * epoch_call_task() function will start scanning this epoch 406 * structure. 407 */ 408 atomic_store_rel_int(&epoch->e_in_use, 1); 409 done: 410 EPOCH_UNLOCK(); 411 return (epoch); 412 } 413 414 void 415 epoch_free(epoch_t epoch) 416 { 417 #ifdef INVARIANTS 418 int cpu; 419 #endif 420 421 EPOCH_LOCK(); 422 423 MPASS(epoch->e_in_use != 0); 424 425 epoch_drain_callbacks(epoch); 426 427 atomic_store_rel_int(&epoch->e_in_use, 0); 428 /* 429 * Make sure the epoch_call_task() function see e_in_use equal 430 * to zero, by calling epoch_wait() on the global_epoch: 431 */ 432 epoch_wait(global_epoch); 433 #ifdef INVARIANTS 434 CPU_FOREACH(cpu) { 435 epoch_record_t er; 436 437 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu); 438 439 /* 440 * Sanity check: none of the records should be in use anymore. 441 * We drained callbacks above and freeing the pcpu records is 442 * imminent. 443 */ 444 MPASS(er->er_td == NULL); 445 MPASS(TAILQ_EMPTY(&er->er_tdlist)); 446 } 447 #endif 448 uma_zfree_pcpu(pcpu_zone_record, epoch->e_pcpu_record); 449 mtx_destroy(&epoch->e_drain_mtx); 450 sx_destroy(&epoch->e_drain_sx); 451 memset(epoch, 0, sizeof(*epoch)); 452 453 EPOCH_UNLOCK(); 454 } 455 456 #define INIT_CHECK(epoch) \ 457 do { \ 458 if (__predict_false((epoch) == NULL)) \ 459 return; \ 460 } while (0) 461 462 void 463 _epoch_enter_preempt(epoch_t epoch, epoch_tracker_t et EPOCH_FILE_LINE) 464 { 465 struct epoch_record *er; 466 struct thread *td; 467 468 MPASS(cold || epoch != NULL); 469 td = curthread; 470 MPASS(kstack_contains(td, (vm_offset_t)et, sizeof(*et))); 471 472 INIT_CHECK(epoch); 473 MPASS(epoch->e_flags & EPOCH_PREEMPT); 474 475 #ifdef EPOCH_TRACE 476 epoch_trace_enter(td, epoch, et, file, line); 477 #endif 478 et->et_td = td; 479 THREAD_NO_SLEEPING(); 480 critical_enter(); 481 sched_pin(); 482 et->et_old_priority = td->td_priority; 483 er = epoch_currecord(epoch); 484 /* Record-level tracking is reserved for non-preemptible epochs. */ 485 MPASS(er->er_td == NULL); 486 TAILQ_INSERT_TAIL(&er->er_tdlist, et, et_link); 487 ck_epoch_begin(&er->er_record, &et->et_section); 488 critical_exit(); 489 } 490 491 void 492 epoch_enter(epoch_t epoch) 493 { 494 epoch_record_t er; 495 496 MPASS(cold || epoch != NULL); 497 INIT_CHECK(epoch); 498 critical_enter(); 499 er = epoch_currecord(epoch); 500 #ifdef INVARIANTS 501 if (er->er_record.active == 0) { 502 MPASS(er->er_td == NULL); 503 er->er_td = curthread; 504 } else { 505 /* We've recursed, just make sure our accounting isn't wrong. */ 506 MPASS(er->er_td == curthread); 507 } 508 #endif 509 ck_epoch_begin(&er->er_record, NULL); 510 } 511 512 void 513 _epoch_exit_preempt(epoch_t epoch, epoch_tracker_t et EPOCH_FILE_LINE) 514 { 515 struct epoch_record *er; 516 struct thread *td; 517 518 INIT_CHECK(epoch); 519 td = curthread; 520 critical_enter(); 521 sched_unpin(); 522 THREAD_SLEEPING_OK(); 523 er = epoch_currecord(epoch); 524 MPASS(epoch->e_flags & EPOCH_PREEMPT); 525 MPASS(et != NULL); 526 MPASS(et->et_td == td); 527 #ifdef INVARIANTS 528 et->et_td = (void*)0xDEADBEEF; 529 /* Record-level tracking is reserved for non-preemptible epochs. */ 530 MPASS(er->er_td == NULL); 531 #endif 532 ck_epoch_end(&er->er_record, &et->et_section); 533 TAILQ_REMOVE(&er->er_tdlist, et, et_link); 534 er->er_gen++; 535 if (__predict_false(et->et_old_priority != td->td_priority)) 536 epoch_adjust_prio(td, et->et_old_priority); 537 critical_exit(); 538 #ifdef EPOCH_TRACE 539 epoch_trace_exit(td, epoch, et, file, line); 540 #endif 541 } 542 543 void 544 epoch_exit(epoch_t epoch) 545 { 546 epoch_record_t er; 547 548 INIT_CHECK(epoch); 549 er = epoch_currecord(epoch); 550 ck_epoch_end(&er->er_record, NULL); 551 #ifdef INVARIANTS 552 MPASS(er->er_td == curthread); 553 if (er->er_record.active == 0) 554 er->er_td = NULL; 555 #endif 556 critical_exit(); 557 } 558 559 /* 560 * epoch_block_handler_preempt() is a callback from the CK code when another 561 * thread is currently in an epoch section. 562 */ 563 static void 564 epoch_block_handler_preempt(struct ck_epoch *global __unused, 565 ck_epoch_record_t *cr, void *arg __unused) 566 { 567 epoch_record_t record; 568 struct thread *td, *owner, *curwaittd; 569 struct epoch_tracker *tdwait; 570 struct turnstile *ts; 571 struct lock_object *lock; 572 int spincount, gen; 573 int locksheld __unused; 574 575 record = __containerof(cr, struct epoch_record, er_record); 576 td = curthread; 577 locksheld = td->td_locks; 578 spincount = 0; 579 counter_u64_add(block_count, 1); 580 /* 581 * We lost a race and there's no longer any threads 582 * on the CPU in an epoch section. 583 */ 584 if (TAILQ_EMPTY(&record->er_tdlist)) 585 return; 586 587 if (record->er_cpuid != curcpu) { 588 /* 589 * If the head of the list is running, we can wait for it 590 * to remove itself from the list and thus save us the 591 * overhead of a migration 592 */ 593 gen = record->er_gen; 594 thread_unlock(td); 595 /* 596 * We can't actually check if the waiting thread is running 597 * so we simply poll for it to exit before giving up and 598 * migrating. 599 */ 600 do { 601 cpu_spinwait(); 602 } while (!TAILQ_EMPTY(&record->er_tdlist) && 603 gen == record->er_gen && 604 spincount++ < MAX_ADAPTIVE_SPIN); 605 thread_lock(td); 606 /* 607 * If the generation has changed we can poll again 608 * otherwise we need to migrate. 609 */ 610 if (gen != record->er_gen) 611 return; 612 /* 613 * Being on the same CPU as that of the record on which 614 * we need to wait allows us access to the thread 615 * list associated with that CPU. We can then examine the 616 * oldest thread in the queue and wait on its turnstile 617 * until it resumes and so on until a grace period 618 * elapses. 619 * 620 */ 621 counter_u64_add(migrate_count, 1); 622 sched_bind(td, record->er_cpuid); 623 /* 624 * At this point we need to return to the ck code 625 * to scan to see if a grace period has elapsed. 626 * We can't move on to check the thread list, because 627 * in the meantime new threads may have arrived that 628 * in fact belong to a different epoch. 629 */ 630 return; 631 } 632 /* 633 * Try to find a thread in an epoch section on this CPU 634 * waiting on a turnstile. Otherwise find the lowest 635 * priority thread (highest prio value) and drop our priority 636 * to match to allow it to run. 637 */ 638 TAILQ_FOREACH(tdwait, &record->er_tdlist, et_link) { 639 /* 640 * Propagate our priority to any other waiters to prevent us 641 * from starving them. They will have their original priority 642 * restore on exit from epoch_wait(). 643 */ 644 curwaittd = tdwait->et_td; 645 if (!TD_IS_INHIBITED(curwaittd) && curwaittd->td_priority > td->td_priority) { 646 critical_enter(); 647 thread_unlock(td); 648 thread_lock(curwaittd); 649 sched_prio(curwaittd, td->td_priority); 650 thread_unlock(curwaittd); 651 thread_lock(td); 652 critical_exit(); 653 } 654 if (TD_IS_INHIBITED(curwaittd) && TD_ON_LOCK(curwaittd) && 655 ((ts = curwaittd->td_blocked) != NULL)) { 656 /* 657 * We unlock td to allow turnstile_wait to reacquire 658 * the thread lock. Before unlocking it we enter a 659 * critical section to prevent preemption after we 660 * reenable interrupts by dropping the thread lock in 661 * order to prevent curwaittd from getting to run. 662 */ 663 critical_enter(); 664 thread_unlock(td); 665 666 if (turnstile_lock(ts, &lock, &owner)) { 667 if (ts == curwaittd->td_blocked) { 668 MPASS(TD_IS_INHIBITED(curwaittd) && 669 TD_ON_LOCK(curwaittd)); 670 critical_exit(); 671 turnstile_wait(ts, owner, 672 curwaittd->td_tsqueue); 673 counter_u64_add(turnstile_count, 1); 674 thread_lock(td); 675 return; 676 } 677 turnstile_unlock(ts, lock); 678 } 679 thread_lock(td); 680 critical_exit(); 681 KASSERT(td->td_locks == locksheld, 682 ("%d extra locks held", td->td_locks - locksheld)); 683 } 684 } 685 /* 686 * We didn't find any threads actually blocked on a lock 687 * so we have nothing to do except context switch away. 688 */ 689 counter_u64_add(switch_count, 1); 690 mi_switch(SW_VOL | SWT_RELINQUISH); 691 /* 692 * It is important the thread lock is dropped while yielding 693 * to allow other threads to acquire the lock pointed to by 694 * TDQ_LOCKPTR(td). Currently mi_switch() will unlock the 695 * thread lock before returning. Else a deadlock like 696 * situation might happen. 697 */ 698 thread_lock(td); 699 } 700 701 void 702 epoch_wait_preempt(epoch_t epoch) 703 { 704 struct thread *td; 705 int was_bound; 706 int old_cpu; 707 int old_pinned; 708 u_char old_prio; 709 int locks __unused; 710 711 MPASS(cold || epoch != NULL); 712 INIT_CHECK(epoch); 713 td = curthread; 714 #ifdef INVARIANTS 715 locks = curthread->td_locks; 716 MPASS(epoch->e_flags & EPOCH_PREEMPT); 717 if ((epoch->e_flags & EPOCH_LOCKED) == 0) 718 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, 719 "epoch_wait() can be long running"); 720 KASSERT(!in_epoch(epoch), ("epoch_wait_preempt() called in the middle " 721 "of an epoch section of the same epoch")); 722 #endif 723 DROP_GIANT(); 724 thread_lock(td); 725 726 old_cpu = PCPU_GET(cpuid); 727 old_pinned = td->td_pinned; 728 old_prio = td->td_priority; 729 was_bound = sched_is_bound(td); 730 sched_unbind(td); 731 td->td_pinned = 0; 732 sched_bind(td, old_cpu); 733 734 ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler_preempt, 735 NULL); 736 737 /* restore CPU binding, if any */ 738 if (was_bound != 0) { 739 sched_bind(td, old_cpu); 740 } else { 741 /* get thread back to initial CPU, if any */ 742 if (old_pinned != 0) 743 sched_bind(td, old_cpu); 744 sched_unbind(td); 745 } 746 /* restore pinned after bind */ 747 td->td_pinned = old_pinned; 748 749 /* restore thread priority */ 750 sched_prio(td, old_prio); 751 thread_unlock(td); 752 PICKUP_GIANT(); 753 KASSERT(td->td_locks == locks, 754 ("%d residual locks held", td->td_locks - locks)); 755 } 756 757 static void 758 epoch_block_handler(struct ck_epoch *g __unused, ck_epoch_record_t *c __unused, 759 void *arg __unused) 760 { 761 cpu_spinwait(); 762 } 763 764 void 765 epoch_wait(epoch_t epoch) 766 { 767 768 MPASS(cold || epoch != NULL); 769 INIT_CHECK(epoch); 770 MPASS(epoch->e_flags == 0); 771 critical_enter(); 772 ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler, NULL); 773 critical_exit(); 774 } 775 776 void 777 epoch_call(epoch_t epoch, epoch_callback_t callback, epoch_context_t ctx) 778 { 779 epoch_record_t er; 780 ck_epoch_entry_t *cb; 781 782 cb = (void *)ctx; 783 784 MPASS(callback); 785 /* too early in boot to have epoch set up */ 786 if (__predict_false(epoch == NULL)) 787 goto boottime; 788 #if !defined(EARLY_AP_STARTUP) 789 if (__predict_false(inited < 2)) 790 goto boottime; 791 #endif 792 793 critical_enter(); 794 *DPCPU_PTR(epoch_cb_count) += 1; 795 er = epoch_currecord(epoch); 796 ck_epoch_call(&er->er_record, cb, (ck_epoch_cb_t *)callback); 797 critical_exit(); 798 return; 799 boottime: 800 callback(ctx); 801 } 802 803 static void 804 epoch_call_task(void *arg __unused) 805 { 806 ck_stack_entry_t *cursor, *head, *next; 807 ck_epoch_record_t *record; 808 epoch_record_t er; 809 epoch_t epoch; 810 ck_stack_t cb_stack; 811 int i, npending, total; 812 813 ck_stack_init(&cb_stack); 814 critical_enter(); 815 epoch_enter(global_epoch); 816 for (total = i = 0; i != MAX_EPOCHS; i++) { 817 epoch = epoch_array + i; 818 if (__predict_false( 819 atomic_load_acq_int(&epoch->e_in_use) == 0)) 820 continue; 821 er = epoch_currecord(epoch); 822 record = &er->er_record; 823 if ((npending = record->n_pending) == 0) 824 continue; 825 ck_epoch_poll_deferred(record, &cb_stack); 826 total += npending - record->n_pending; 827 } 828 epoch_exit(global_epoch); 829 *DPCPU_PTR(epoch_cb_count) -= total; 830 critical_exit(); 831 832 counter_u64_add(epoch_call_count, total); 833 counter_u64_add(epoch_call_task_count, 1); 834 835 head = ck_stack_batch_pop_npsc(&cb_stack); 836 for (cursor = head; cursor != NULL; cursor = next) { 837 struct ck_epoch_entry *entry = 838 ck_epoch_entry_container(cursor); 839 840 next = CK_STACK_NEXT(cursor); 841 entry->function(entry); 842 } 843 } 844 845 static int 846 in_epoch_verbose_preempt(epoch_t epoch, int dump_onfail) 847 { 848 epoch_record_t er; 849 struct epoch_tracker *tdwait; 850 struct thread *td; 851 852 MPASS(epoch != NULL); 853 MPASS((epoch->e_flags & EPOCH_PREEMPT) != 0); 854 td = curthread; 855 if (THREAD_CAN_SLEEP()) 856 return (0); 857 critical_enter(); 858 er = epoch_currecord(epoch); 859 TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link) 860 if (tdwait->et_td == td) { 861 critical_exit(); 862 return (1); 863 } 864 #ifdef INVARIANTS 865 if (dump_onfail) { 866 MPASS(td->td_pinned); 867 printf("cpu: %d id: %d\n", curcpu, td->td_tid); 868 TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link) 869 printf("td_tid: %d ", tdwait->et_td->td_tid); 870 printf("\n"); 871 } 872 #endif 873 critical_exit(); 874 return (0); 875 } 876 877 #ifdef INVARIANTS 878 static void 879 epoch_assert_nocpu(epoch_t epoch, struct thread *td) 880 { 881 epoch_record_t er; 882 int cpu; 883 bool crit; 884 885 crit = td->td_critnest > 0; 886 887 /* Check for a critical section mishap. */ 888 CPU_FOREACH(cpu) { 889 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu); 890 KASSERT(er->er_td != td, 891 ("%s critical section in epoch '%s', from cpu %d", 892 (crit ? "exited" : "re-entered"), epoch->e_name, cpu)); 893 } 894 } 895 #else 896 #define epoch_assert_nocpu(e, td) do {} while (0) 897 #endif 898 899 int 900 in_epoch_verbose(epoch_t epoch, int dump_onfail) 901 { 902 epoch_record_t er; 903 struct thread *td; 904 905 if (__predict_false((epoch) == NULL)) 906 return (0); 907 if ((epoch->e_flags & EPOCH_PREEMPT) != 0) 908 return (in_epoch_verbose_preempt(epoch, dump_onfail)); 909 910 /* 911 * The thread being in a critical section is a necessary 912 * condition to be correctly inside a non-preemptible epoch, 913 * so it's definitely not in this epoch. 914 */ 915 td = curthread; 916 if (td->td_critnest == 0) { 917 epoch_assert_nocpu(epoch, td); 918 return (0); 919 } 920 921 /* 922 * The current cpu is in a critical section, so the epoch record will be 923 * stable for the rest of this function. Knowing that the record is not 924 * active is sufficient for knowing whether we're in this epoch or not, 925 * since it's a pcpu record. 926 */ 927 er = epoch_currecord(epoch); 928 if (er->er_record.active == 0) { 929 epoch_assert_nocpu(epoch, td); 930 return (0); 931 } 932 933 MPASS(er->er_td == td); 934 return (1); 935 } 936 937 int 938 in_epoch(epoch_t epoch) 939 { 940 return (in_epoch_verbose(epoch, 0)); 941 } 942 943 static void 944 epoch_drain_cb(struct epoch_context *ctx) 945 { 946 struct epoch *epoch = 947 __containerof(ctx, struct epoch_record, er_drain_ctx)->er_parent; 948 949 if (atomic_fetchadd_int(&epoch->e_drain_count, -1) == 1) { 950 mtx_lock(&epoch->e_drain_mtx); 951 wakeup(epoch); 952 mtx_unlock(&epoch->e_drain_mtx); 953 } 954 } 955 956 void 957 epoch_drain_callbacks(epoch_t epoch) 958 { 959 epoch_record_t er; 960 struct thread *td; 961 int was_bound; 962 int old_pinned; 963 int old_cpu; 964 int cpu; 965 966 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, 967 "epoch_drain_callbacks() may sleep!"); 968 969 /* too early in boot to have epoch set up */ 970 if (__predict_false(epoch == NULL)) 971 return; 972 #if !defined(EARLY_AP_STARTUP) 973 if (__predict_false(inited < 2)) 974 return; 975 #endif 976 DROP_GIANT(); 977 978 sx_xlock(&epoch->e_drain_sx); 979 mtx_lock(&epoch->e_drain_mtx); 980 981 td = curthread; 982 thread_lock(td); 983 old_cpu = PCPU_GET(cpuid); 984 old_pinned = td->td_pinned; 985 was_bound = sched_is_bound(td); 986 sched_unbind(td); 987 td->td_pinned = 0; 988 989 CPU_FOREACH(cpu) 990 epoch->e_drain_count++; 991 CPU_FOREACH(cpu) { 992 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu); 993 sched_bind(td, cpu); 994 epoch_call(epoch, &epoch_drain_cb, &er->er_drain_ctx); 995 } 996 997 /* restore CPU binding, if any */ 998 if (was_bound != 0) { 999 sched_bind(td, old_cpu); 1000 } else { 1001 /* get thread back to initial CPU, if any */ 1002 if (old_pinned != 0) 1003 sched_bind(td, old_cpu); 1004 sched_unbind(td); 1005 } 1006 /* restore pinned after bind */ 1007 td->td_pinned = old_pinned; 1008 1009 thread_unlock(td); 1010 1011 while (epoch->e_drain_count != 0) 1012 msleep(epoch, &epoch->e_drain_mtx, PZERO, "EDRAIN", 0); 1013 1014 mtx_unlock(&epoch->e_drain_mtx); 1015 sx_xunlock(&epoch->e_drain_sx); 1016 1017 PICKUP_GIANT(); 1018 } 1019