sys/kern/subr_epoch.c

   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 static MALLOC_DEFINE(M_EPOCH, "epoch", "epoch based reclamation");
  58
  59 #ifdef __amd64__
  60 #define EPOCH_ALIGN CACHE_LINE_SIZE*2
  61 #else
  62 #define EPOCH_ALIGN CACHE_LINE_SIZE
  63 #endif
  64
  65 TAILQ_HEAD (epoch_tdlist, epoch_tracker);
  66 typedef struct epoch_record {
  67         ck_epoch_record_t er_record;
  68         volatile struct epoch_tdlist er_tdlist;
  69         volatile uint32_t er_gen;
  70         uint32_t er_cpuid;
  71         /* fields above are part of KBI and cannot be modified */
  72         struct epoch_context er_drain_ctx;
  73         struct epoch *er_parent;
  74 } __aligned(EPOCH_ALIGN)     *epoch_record_t;
  75
  76 struct epoch {
  77         struct ck_epoch e_epoch __aligned(EPOCH_ALIGN);
  78         epoch_record_t e_pcpu_record;
  79         int     e_idx;
  80         int     e_flags;
  81         /* fields above are part of KBI and cannot be modified */
  82         struct sx e_drain_sx;
  83         struct mtx e_drain_mtx;
  84         volatile int e_drain_count;
  85 };
  86
  87 /* arbitrary --- needs benchmarking */
  88 #define MAX_ADAPTIVE_SPIN 100
  89 #define MAX_EPOCHS 64
  90
  91 CTASSERT(sizeof(ck_epoch_entry_t) == sizeof(struct epoch_context));
  92 SYSCTL_NODE(_kern, OID_AUTO, epoch, CTLFLAG_RW, 0, "epoch information");
  93 SYSCTL_NODE(_kern_epoch, OID_AUTO, stats, CTLFLAG_RW, 0, "epoch stats");
  94
  95 /* Stats. */
  96 static counter_u64_t block_count;
  97
  98 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, nblocked, CTLFLAG_RW,
  99     &block_count, "# of times a thread was in an epoch when epoch_wait was called");
 100 static counter_u64_t migrate_count;
 101
 102 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, migrations, CTLFLAG_RW,
 103     &migrate_count, "# of times thread was migrated to another CPU in epoch_wait");
 104 static counter_u64_t turnstile_count;
 105
 106 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, ncontended, CTLFLAG_RW,
 107     &turnstile_count, "# of times a thread was blocked on a lock in an epoch during an epoch_wait");
 108 static counter_u64_t switch_count;
 109
 110 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, switches, CTLFLAG_RW,
 111     &switch_count, "# of times a thread voluntarily context switched in epoch_wait");
 112 static counter_u64_t epoch_call_count;
 113
 114 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_calls, CTLFLAG_RW,
 115     &epoch_call_count, "# of times a callback was deferred");
 116 static counter_u64_t epoch_call_task_count;
 117
 118 SYSCTL_COUNTER_U64(_kern_epoch_stats, OID_AUTO, epoch_call_tasks, CTLFLAG_RW,
 119     &epoch_call_task_count, "# of times a callback task was run");
 120
 121 TAILQ_HEAD (threadlist, thread);
 122
 123 CK_STACK_CONTAINER(struct ck_epoch_entry, stack_entry,
 124     ck_epoch_entry_container)
 125
 126 epoch_t allepochs[MAX_EPOCHS];
 127
 128 DPCPU_DEFINE(struct grouptask, epoch_cb_task);
 129 DPCPU_DEFINE(int, epoch_cb_count);
 130
 131 static __read_mostly int inited;
 132 static __read_mostly int epoch_count;
 133 __read_mostly epoch_t global_epoch;
 134 __read_mostly epoch_t global_epoch_preempt;
 135
 136 static void epoch_call_task(void *context __unused);
 137 static  uma_zone_t pcpu_zone_record;
 138
 139 static void
 140 epoch_init(void *arg __unused)
 141 {
 142         int cpu;
 143
 144         block_count = counter_u64_alloc(M_WAITOK);
 145         migrate_count = counter_u64_alloc(M_WAITOK);
 146         turnstile_count = counter_u64_alloc(M_WAITOK);
 147         switch_count = counter_u64_alloc(M_WAITOK);
 148         epoch_call_count = counter_u64_alloc(M_WAITOK);
 149         epoch_call_task_count = counter_u64_alloc(M_WAITOK);
 150
 151         pcpu_zone_record = uma_zcreate("epoch_record pcpu",
 152             sizeof(struct epoch_record), NULL, NULL, NULL, NULL,
 153             UMA_ALIGN_PTR, UMA_ZONE_PCPU);
 154         CPU_FOREACH(cpu) {
 155                 GROUPTASK_INIT(DPCPU_ID_PTR(cpu, epoch_cb_task), 0,
 156                     epoch_call_task, NULL);
 157                 taskqgroup_attach_cpu(qgroup_softirq,
 158                     DPCPU_ID_PTR(cpu, epoch_cb_task), NULL, cpu, -1,
 159                     "epoch call task");
 160         }
 161         inited = 1;
 162         global_epoch = epoch_alloc(0);
 163         global_epoch_preempt = epoch_alloc(EPOCH_PREEMPT);
 164 }
 165 SYSINIT(epoch, SI_SUB_TASKQ + 1, SI_ORDER_FIRST, epoch_init, NULL);
 166
 167 #if !defined(EARLY_AP_STARTUP)
 168 static void
 169 epoch_init_smp(void *dummy __unused)
 170 {
 171         inited = 2;
 172 }
 173 SYSINIT(epoch_smp, SI_SUB_SMP + 1, SI_ORDER_FIRST, epoch_init_smp, NULL);
 174 #endif
 175
 176 static void
 177 epoch_ctor(epoch_t epoch)
 178 {
 179         epoch_record_t er;
 180         int cpu;
 181
 182         epoch->e_pcpu_record = uma_zalloc_pcpu(pcpu_zone_record, M_WAITOK);
 183         CPU_FOREACH(cpu) {
 184                 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
 185                 bzero(er, sizeof(*er));
 186                 ck_epoch_register(&epoch->e_epoch, &er->er_record, NULL);
 187                 TAILQ_INIT((struct threadlist *)(uintptr_t)&er->er_tdlist);
 188                 er->er_cpuid = cpu;
 189                 er->er_parent = epoch;
 190         }
 191 }
 192
 193 static void
 194 epoch_adjust_prio(struct thread *td, u_char prio)
 195 {
 196
 197         thread_lock(td);
 198         sched_prio(td, prio);
 199         thread_unlock(td);
 200 }
 201
 202 epoch_t
 203 epoch_alloc(int flags)
 204 {
 205         epoch_t epoch;
 206
 207         if (__predict_false(!inited))
 208                 panic("%s called too early in boot", __func__);
 209         epoch = malloc(sizeof(struct epoch), M_EPOCH, M_ZERO | M_WAITOK);
 210         ck_epoch_init(&epoch->e_epoch);
 211         epoch_ctor(epoch);
 212         MPASS(epoch_count < MAX_EPOCHS - 2);
 213         epoch->e_flags = flags;
 214         epoch->e_idx = epoch_count;
 215         sx_init(&epoch->e_drain_sx, "epoch-drain-sx");
 216         mtx_init(&epoch->e_drain_mtx, "epoch-drain-mtx", NULL, MTX_DEF);
 217         allepochs[epoch_count++] = epoch;
 218         return (epoch);
 219 }
 220
 221 void
 222 epoch_free(epoch_t epoch)
 223 {
 224
 225         epoch_drain_callbacks(epoch);
 226         allepochs[epoch->e_idx] = NULL;
 227         epoch_wait(global_epoch);
 228         uma_zfree_pcpu(pcpu_zone_record, epoch->e_pcpu_record);
 229         mtx_destroy(&epoch->e_drain_mtx);
 230         sx_destroy(&epoch->e_drain_sx);
 231         free(epoch, M_EPOCH);
 232 }
 233
 234 static epoch_record_t
 235 epoch_currecord(epoch_t epoch)
 236 {
 237
 238         return (zpcpu_get_cpu(epoch->e_pcpu_record, curcpu));
 239 }
 240
 241 #define INIT_CHECK(epoch)                                       \
 242         do {                                                    \
 243                 if (__predict_false((epoch) == NULL))           \
 244                         return;                                 \
 245         } while (0)
 246
 247 void
 248 epoch_enter_preempt(epoch_t epoch, epoch_tracker_t et)
 249 {
 250         struct epoch_record *er;
 251         struct thread *td;
 252
 253         MPASS(cold || epoch != NULL);
 254         INIT_CHECK(epoch);
 255         MPASS(epoch->e_flags & EPOCH_PREEMPT);
 256 #ifdef EPOCH_TRACKER_DEBUG
 257         et->et_magic_pre = EPOCH_MAGIC0;
 258         et->et_magic_post = EPOCH_MAGIC1;
 259 #endif
 260         td = curthread;
 261         et->et_td = td;
 262         td->td_epochnest++;
 263         critical_enter();
 264         sched_pin();
 265
 266         td->td_pre_epoch_prio = td->td_priority;
 267         er = epoch_currecord(epoch);
 268         TAILQ_INSERT_TAIL(&er->er_tdlist, et, et_link);
 269         ck_epoch_begin(&er->er_record, &et->et_section);
 270         critical_exit();
 271 }
 272
 273 void
 274 epoch_enter(epoch_t epoch)
 275 {
 276         struct thread *td;
 277         epoch_record_t er;
 278
 279         MPASS(cold || epoch != NULL);
 280         INIT_CHECK(epoch);
 281         td = curthread;
 282
 283         td->td_epochnest++;
 284         critical_enter();
 285         er = epoch_currecord(epoch);
 286         ck_epoch_begin(&er->er_record, NULL);
 287 }
 288
 289 void
 290 epoch_exit_preempt(epoch_t epoch, epoch_tracker_t et)
 291 {
 292         struct epoch_record *er;
 293         struct thread *td;
 294
 295         INIT_CHECK(epoch);
 296         td = curthread;
 297         critical_enter();
 298         sched_unpin();
 299         MPASS(td->td_epochnest);
 300         td->td_epochnest--;
 301         er = epoch_currecord(epoch);
 302         MPASS(epoch->e_flags & EPOCH_PREEMPT);
 303         MPASS(et != NULL);
 304         MPASS(et->et_td == td);
 305 #ifdef EPOCH_TRACKER_DEBUG
 306         MPASS(et->et_magic_pre == EPOCH_MAGIC0);
 307         MPASS(et->et_magic_post == EPOCH_MAGIC1);
 308         et->et_magic_pre = 0;
 309         et->et_magic_post = 0;
 310 #endif
 311 #ifdef INVARIANTS
 312         et->et_td = (void*)0xDEADBEEF;
 313 #endif
 314         ck_epoch_end(&er->er_record, &et->et_section);
 315         TAILQ_REMOVE(&er->er_tdlist, et, et_link);
 316         er->er_gen++;
 317         if (__predict_false(td->td_pre_epoch_prio != td->td_priority))
 318                 epoch_adjust_prio(td, td->td_pre_epoch_prio);
 319         critical_exit();
 320 }
 321
 322 void
 323 epoch_exit(epoch_t epoch)
 324 {
 325         struct thread *td;
 326         epoch_record_t er;
 327
 328         INIT_CHECK(epoch);
 329         td = curthread;
 330         MPASS(td->td_epochnest);
 331         td->td_epochnest--;
 332         er = epoch_currecord(epoch);
 333         ck_epoch_end(&er->er_record, NULL);
 334         critical_exit();
 335 }
 336
 337 /*
 338  * epoch_block_handler_preempt() is a callback from the CK code when another
 339  * thread is currently in an epoch section.
 340  */
 341 static void
 342 epoch_block_handler_preempt(struct ck_epoch *global __unused,
 343     ck_epoch_record_t *cr, void *arg __unused)
 344 {
 345         epoch_record_t record;
 346         struct thread *td, *owner, *curwaittd;
 347         struct epoch_tracker *tdwait;
 348         struct turnstile *ts;
 349         struct lock_object *lock;
 350         int spincount, gen;
 351         int locksheld __unused;
 352
 353         record = __containerof(cr, struct epoch_record, er_record);
 354         td = curthread;
 355         locksheld = td->td_locks;
 356         spincount = 0;
 357         counter_u64_add(block_count, 1);
 358         /*
 359          * We lost a race and there's no longer any threads
 360          * on the CPU in an epoch section.
 361          */
 362         if (TAILQ_EMPTY(&record->er_tdlist))
 363                 return;
 364
 365         if (record->er_cpuid != curcpu) {
 366                 /*
 367                  * If the head of the list is running, we can wait for it
 368                  * to remove itself from the list and thus save us the
 369                  * overhead of a migration
 370                  */
 371                 gen = record->er_gen;
 372                 thread_unlock(td);
 373                 /*
 374                  * We can't actually check if the waiting thread is running
 375                  * so we simply poll for it to exit before giving up and
 376                  * migrating.
 377                  */
 378                 do {
 379                         cpu_spinwait();
 380                 } while (!TAILQ_EMPTY(&record->er_tdlist) &&
 381                                  gen == record->er_gen &&
 382                                  spincount++ < MAX_ADAPTIVE_SPIN);
 383                 thread_lock(td);
 384                 /*
 385                  * If the generation has changed we can poll again
 386                  * otherwise we need to migrate.
 387                  */
 388                 if (gen != record->er_gen)
 389                         return;
 390                 /*
 391                  * Being on the same CPU as that of the record on which
 392                  * we need to wait allows us access to the thread
 393                  * list associated with that CPU. We can then examine the
 394                  * oldest thread in the queue and wait on its turnstile
 395                  * until it resumes and so on until a grace period
 396                  * elapses.
 397                  *
 398                  */
 399                 counter_u64_add(migrate_count, 1);
 400                 sched_bind(td, record->er_cpuid);
 401                 /*
 402                  * At this point we need to return to the ck code
 403                  * to scan to see if a grace period has elapsed.
 404                  * We can't move on to check the thread list, because
 405                  * in the meantime new threads may have arrived that
 406                  * in fact belong to a different epoch.
 407                  */
 408                 return;
 409         }
 410         /*
 411          * Try to find a thread in an epoch section on this CPU
 412          * waiting on a turnstile. Otherwise find the lowest
 413          * priority thread (highest prio value) and drop our priority
 414          * to match to allow it to run.
 415          */
 416         TAILQ_FOREACH(tdwait, &record->er_tdlist, et_link) {
 417                 /*
 418                  * Propagate our priority to any other waiters to prevent us
 419                  * from starving them. They will have their original priority
 420                  * restore on exit from epoch_wait().
 421                  */
 422                 curwaittd = tdwait->et_td;
 423                 if (!TD_IS_INHIBITED(curwaittd) && curwaittd->td_priority > td->td_priority) {
 424                         critical_enter();
 425                         thread_unlock(td);
 426                         thread_lock(curwaittd);
 427                         sched_prio(curwaittd, td->td_priority);
 428                         thread_unlock(curwaittd);
 429                         thread_lock(td);
 430                         critical_exit();
 431                 }
 432                 if (TD_IS_INHIBITED(curwaittd) && TD_ON_LOCK(curwaittd) &&
 433                     ((ts = curwaittd->td_blocked) != NULL)) {
 434                         /*
 435                          * We unlock td to allow turnstile_wait to reacquire
 436                          * the thread lock. Before unlocking it we enter a
 437                          * critical section to prevent preemption after we
 438                          * reenable interrupts by dropping the thread lock in
 439                          * order to prevent curwaittd from getting to run.
 440                          */
 441                         critical_enter();
 442                         thread_unlock(td);
 443
 444                         if (turnstile_lock(ts, &lock, &owner)) {
 445                                 if (ts == curwaittd->td_blocked) {
 446                                         MPASS(TD_IS_INHIBITED(curwaittd) &&
 447                                             TD_ON_LOCK(curwaittd));
 448                                         critical_exit();
 449                                         turnstile_wait(ts, owner,
 450                                             curwaittd->td_tsqueue);
 451                                         counter_u64_add(turnstile_count, 1);
 452                                         thread_lock(td);
 453                                         return;
 454                                 }
 455                                 turnstile_unlock(ts, lock);
 456                         }
 457                         thread_lock(td);
 458                         critical_exit();
 459                         KASSERT(td->td_locks == locksheld,
 460                             ("%d extra locks held", td->td_locks - locksheld));
 461                 }
 462         }
 463         /*
 464          * We didn't find any threads actually blocked on a lock
 465          * so we have nothing to do except context switch away.
 466          */
 467         counter_u64_add(switch_count, 1);
 468         mi_switch(SW_VOL | SWT_RELINQUISH, NULL);
 469
 470         /*
 471          * Release the thread lock while yielding to
 472          * allow other threads to acquire the lock
 473          * pointed to by TDQ_LOCKPTR(td). Else a
 474          * deadlock like situation might happen. (HPS)
 475          */
 476         thread_unlock(td);
 477         thread_lock(td);
 478 }
 479
 480 void
 481 epoch_wait_preempt(epoch_t epoch)
 482 {
 483         struct thread *td;
 484         int was_bound;
 485         int old_cpu;
 486         int old_pinned;
 487         u_char old_prio;
 488         int locks __unused;
 489
 490         MPASS(cold || epoch != NULL);
 491         INIT_CHECK(epoch);
 492         td = curthread;
 493 #ifdef INVARIANTS
 494         locks = curthread->td_locks;
 495         MPASS(epoch->e_flags & EPOCH_PREEMPT);
 496         if ((epoch->e_flags & EPOCH_LOCKED) == 0)
 497                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
 498                     "epoch_wait() can be long running");
 499         KASSERT(!in_epoch(epoch), ("epoch_wait_preempt() called in the middle "
 500             "of an epoch section of the same epoch"));
 501 #endif
 502         thread_lock(td);
 503         DROP_GIANT();
 504
 505         old_cpu = PCPU_GET(cpuid);
 506         old_pinned = td->td_pinned;
 507         old_prio = td->td_priority;
 508         was_bound = sched_is_bound(td);
 509         sched_unbind(td);
 510         td->td_pinned = 0;
 511         sched_bind(td, old_cpu);
 512
 513         ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler_preempt,
 514             NULL);
 515
 516         /* restore CPU binding, if any */
 517         if (was_bound != 0) {
 518                 sched_bind(td, old_cpu);
 519         } else {
 520                 /* get thread back to initial CPU, if any */
 521                 if (old_pinned != 0)
 522                         sched_bind(td, old_cpu);
 523                 sched_unbind(td);
 524         }
 525         /* restore pinned after bind */
 526         td->td_pinned = old_pinned;
 527
 528         /* restore thread priority */
 529         sched_prio(td, old_prio);
 530         thread_unlock(td);
 531         PICKUP_GIANT();
 532         KASSERT(td->td_locks == locks,
 533             ("%d residual locks held", td->td_locks - locks));
 534 }
 535
 536 static void
 537 epoch_block_handler(struct ck_epoch *g __unused, ck_epoch_record_t *c __unused,
 538     void *arg __unused)
 539 {
 540         cpu_spinwait();
 541 }
 542
 543 void
 544 epoch_wait(epoch_t epoch)
 545 {
 546
 547         MPASS(cold || epoch != NULL);
 548         INIT_CHECK(epoch);
 549         MPASS(epoch->e_flags == 0);
 550         critical_enter();
 551         ck_epoch_synchronize_wait(&epoch->e_epoch, epoch_block_handler, NULL);
 552         critical_exit();
 553 }
 554
 555 void
 556 epoch_call(epoch_t epoch, epoch_context_t ctx, void (*callback) (epoch_context_t))
 557 {
 558         epoch_record_t er;
 559         ck_epoch_entry_t *cb;
 560
 561         cb = (void *)ctx;
 562
 563         MPASS(callback);
 564         /* too early in boot to have epoch set up */
 565         if (__predict_false(epoch == NULL))
 566                 goto boottime;
 567 #if !defined(EARLY_AP_STARTUP)
 568         if (__predict_false(inited < 2))
 569                 goto boottime;
 570 #endif
 571
 572         critical_enter();
 573         *DPCPU_PTR(epoch_cb_count) += 1;
 574         er = epoch_currecord(epoch);
 575         ck_epoch_call(&er->er_record, cb, (ck_epoch_cb_t *)callback);
 576         critical_exit();
 577         return;
 578 boottime:
 579         callback(ctx);
 580 }
 581
 582 static void
 583 epoch_call_task(void *arg __unused)
 584 {
 585         ck_stack_entry_t *cursor, *head, *next;
 586         ck_epoch_record_t *record;
 587         epoch_record_t er;
 588         epoch_t epoch;
 589         ck_stack_t cb_stack;
 590         int i, npending, total;
 591
 592         ck_stack_init(&cb_stack);
 593         critical_enter();
 594         epoch_enter(global_epoch);
 595         for (total = i = 0; i < epoch_count; i++) {
 596                 if (__predict_false((epoch = allepochs[i]) == NULL))
 597                         continue;
 598                 er = epoch_currecord(epoch);
 599                 record = &er->er_record;
 600                 if ((npending = record->n_pending) == 0)
 601                         continue;
 602                 ck_epoch_poll_deferred(record, &cb_stack);
 603                 total += npending - record->n_pending;
 604         }
 605         epoch_exit(global_epoch);
 606         *DPCPU_PTR(epoch_cb_count) -= total;
 607         critical_exit();
 608
 609         counter_u64_add(epoch_call_count, total);
 610         counter_u64_add(epoch_call_task_count, 1);
 611
 612         head = ck_stack_batch_pop_npsc(&cb_stack);
 613         for (cursor = head; cursor != NULL; cursor = next) {
 614                 struct ck_epoch_entry *entry =
 615                     ck_epoch_entry_container(cursor);
 616
 617                 next = CK_STACK_NEXT(cursor);
 618                 entry->function(entry);
 619         }
 620 }
 621
 622 int
 623 in_epoch_verbose(epoch_t epoch, int dump_onfail)
 624 {
 625         struct epoch_tracker *tdwait;
 626         struct thread *td;
 627         epoch_record_t er;
 628
 629         td = curthread;
 630         if (td->td_epochnest == 0)
 631                 return (0);
 632         if (__predict_false((epoch) == NULL))
 633                 return (0);
 634         critical_enter();
 635         er = epoch_currecord(epoch);
 636         TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link)
 637                 if (tdwait->et_td == td) {
 638                         critical_exit();
 639                         return (1);
 640                 }
 641 #ifdef INVARIANTS
 642         if (dump_onfail) {
 643                 MPASS(td->td_pinned);
 644                 printf("cpu: %d id: %d\n", curcpu, td->td_tid);
 645                 TAILQ_FOREACH(tdwait, &er->er_tdlist, et_link)
 646                         printf("td_tid: %d ", tdwait->et_td->td_tid);
 647                 printf("\n");
 648         }
 649 #endif
 650         critical_exit();
 651         return (0);
 652 }
 653
 654 int
 655 in_epoch(epoch_t epoch)
 656 {
 657         return (in_epoch_verbose(epoch, 0));
 658 }
 659
 660 static void
 661 epoch_drain_cb(struct epoch_context *ctx)
 662 {
 663         struct epoch *epoch =
 664             __containerof(ctx, struct epoch_record, er_drain_ctx)->er_parent;
 665
 666         if (atomic_fetchadd_int(&epoch->e_drain_count, -1) == 1) {
 667                 mtx_lock(&epoch->e_drain_mtx);
 668                 wakeup(epoch);
 669                 mtx_unlock(&epoch->e_drain_mtx);
 670         }
 671 }
 672
 673 void
 674 epoch_drain_callbacks(epoch_t epoch)
 675 {
 676         epoch_record_t er;
 677         struct thread *td;
 678         int was_bound;
 679         int old_pinned;
 680         int old_cpu;
 681         int cpu;
 682
 683         WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
 684             "epoch_drain_callbacks() may sleep!");
 685
 686         /* too early in boot to have epoch set up */
 687         if (__predict_false(epoch == NULL))
 688                 return;
 689 #if !defined(EARLY_AP_STARTUP)
 690         if (__predict_false(inited < 2))
 691                 return;
 692 #endif
 693         DROP_GIANT();
 694
 695         sx_xlock(&epoch->e_drain_sx);
 696         mtx_lock(&epoch->e_drain_mtx);
 697
 698         td = curthread;
 699         thread_lock(td);
 700         old_cpu = PCPU_GET(cpuid);
 701         old_pinned = td->td_pinned;
 702         was_bound = sched_is_bound(td);
 703         sched_unbind(td);
 704         td->td_pinned = 0;
 705
 706         CPU_FOREACH(cpu)
 707                 epoch->e_drain_count++;
 708         CPU_FOREACH(cpu) {
 709                 er = zpcpu_get_cpu(epoch->e_pcpu_record, cpu);
 710                 sched_bind(td, cpu);
 711                 epoch_call(epoch, &er->er_drain_ctx, &epoch_drain_cb);
 712         }
 713
 714         /* restore CPU binding, if any */
 715         if (was_bound != 0) {
 716                 sched_bind(td, old_cpu);
 717         } else {
 718                 /* get thread back to initial CPU, if any */
 719                 if (old_pinned != 0)
 720                         sched_bind(td, old_cpu);
 721                 sched_unbind(td);
 722         }
 723         /* restore pinned after bind */
 724         td->td_pinned = old_pinned;
 725
 726         thread_unlock(td);
 727
 728         while (epoch->e_drain_count != 0)
 729                 msleep(epoch, &epoch->e_drain_mtx, PZERO, "EDRAIN", 0);
 730
 731         mtx_unlock(&epoch->e_drain_mtx);
 732         sx_xunlock(&epoch->e_drain_sx);
 733
 734         PICKUP_GIANT();
 735 }
 736
 737 /* for binary compatibility */
 738
 739 struct epoch_tracker_KBI {
 740         void *datap[3];
 741 #ifdef EPOCH_TRACKER_DEBUG
 742         int datai[5];
 743 #else
 744         int datai[1];
 745 #endif
 746 } __aligned(sizeof(void *));
 747
 748 CTASSERT(sizeof(struct epoch_tracker_KBI) >= sizeof(struct epoch_tracker));
 749
 750 void
 751 epoch_enter_preempt_KBI(epoch_t epoch, epoch_tracker_t et)
 752 {
 753         epoch_enter_preempt(epoch, et);
 754 }
 755
 756 void
 757 epoch_exit_preempt_KBI(epoch_t epoch, epoch_tracker_t et)
 758 {
 759         epoch_exit_preempt(epoch, et);
 760 }
 761
 762 void
 763 epoch_enter_KBI(epoch_t epoch)
 764 {
 765         epoch_enter(epoch);
 766 }
 767
 768 void
 769 epoch_exit_KBI(epoch_t epoch)
 770 {
 771         epoch_exit(epoch);
 772 }