sys/kern/kern_thread.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause
   3  *
   4  * Copyright (C) 2001 Julian Elischer <julian@freebsd.org>.
   5  *  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice(s), this list of conditions and the following disclaimer as
  12  *    the first lines of this file unmodified other than the possible
  13  *    addition of one or more copyright notices.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice(s), this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
  19  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  20  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  21  * DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
  22  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  23  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  24  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  25  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  28  * DAMAGE.
  29  */
  30
  31 #include "opt_witness.h"
  32 #include "opt_hwpmc_hooks.h"
  33
  34 #include <sys/cdefs.h>
  35 __FBSDID("$FreeBSD$");
  36
  37 #include <sys/param.h>
  38 #include <sys/systm.h>
  39 #include <sys/kernel.h>
  40 #include <sys/lock.h>
  41 #include <sys/msan.h>
  42 #include <sys/mutex.h>
  43 #include <sys/proc.h>
  44 #include <sys/bitstring.h>
  45 #include <sys/epoch.h>
  46 #include <sys/rangelock.h>
  47 #include <sys/resourcevar.h>
  48 #include <sys/sdt.h>
  49 #include <sys/smp.h>
  50 #include <sys/sched.h>
  51 #include <sys/sleepqueue.h>
  52 #include <sys/selinfo.h>
  53 #include <sys/syscallsubr.h>
  54 #include <sys/dtrace_bsd.h>
  55 #include <sys/sysent.h>
  56 #include <sys/turnstile.h>
  57 #include <sys/taskqueue.h>
  58 #include <sys/ktr.h>
  59 #include <sys/rwlock.h>
  60 #include <sys/umtxvar.h>
  61 #include <sys/vmmeter.h>
  62 #include <sys/cpuset.h>
  63 #ifdef  HWPMC_HOOKS
  64 #include <sys/pmckern.h>
  65 #endif
  66 #include <sys/priv.h>
  67
  68 #include <security/audit/audit.h>
  69
  70 #include <vm/pmap.h>
  71 #include <vm/vm.h>
  72 #include <vm/vm_extern.h>
  73 #include <vm/uma.h>
  74 #include <vm/vm_phys.h>
  75 #include <sys/eventhandler.h>
  76
  77 /*
  78  * Asserts below verify the stability of struct thread and struct proc
  79  * layout, as exposed by KBI to modules.  On head, the KBI is allowed
  80  * to drift, change to the structures must be accompanied by the
  81  * assert update.
  82  *
  83  * On the stable branches after KBI freeze, conditions must not be
  84  * violated.  Typically new fields are moved to the end of the
  85  * structures.
  86  */
  87 #ifdef __amd64__
  88 _Static_assert(offsetof(struct thread, td_flags) == 0x108,
  89     "struct thread KBI td_flags");
  90 _Static_assert(offsetof(struct thread, td_pflags) == 0x114,
  91     "struct thread KBI td_pflags");
  92 _Static_assert(offsetof(struct thread, td_frame) == 0x4b8,
  93     "struct thread KBI td_frame");
  94 _Static_assert(offsetof(struct thread, td_emuldata) == 0x6c0,
  95     "struct thread KBI td_emuldata");
  96 _Static_assert(offsetof(struct proc, p_flag) == 0xb8,
  97     "struct proc KBI p_flag");
  98 _Static_assert(offsetof(struct proc, p_pid) == 0xc4,
  99     "struct proc KBI p_pid");
 100 _Static_assert(offsetof(struct proc, p_filemon) == 0x3c8,
 101     "struct proc KBI p_filemon");
 102 _Static_assert(offsetof(struct proc, p_comm) == 0x3e0,
 103     "struct proc KBI p_comm");
 104 _Static_assert(offsetof(struct proc, p_emuldata) == 0x4d0,
 105     "struct proc KBI p_emuldata");
 106 #endif
 107 #ifdef __i386__
 108 _Static_assert(offsetof(struct thread, td_flags) == 0x9c,
 109     "struct thread KBI td_flags");
 110 _Static_assert(offsetof(struct thread, td_pflags) == 0xa8,
 111     "struct thread KBI td_pflags");
 112 _Static_assert(offsetof(struct thread, td_frame) == 0x314,
 113     "struct thread KBI td_frame");
 114 _Static_assert(offsetof(struct thread, td_emuldata) == 0x358,
 115     "struct thread KBI td_emuldata");
 116 _Static_assert(offsetof(struct proc, p_flag) == 0x6c,
 117     "struct proc KBI p_flag");
 118 _Static_assert(offsetof(struct proc, p_pid) == 0x78,
 119     "struct proc KBI p_pid");
 120 _Static_assert(offsetof(struct proc, p_filemon) == 0x270,
 121     "struct proc KBI p_filemon");
 122 _Static_assert(offsetof(struct proc, p_comm) == 0x284,
 123     "struct proc KBI p_comm");
 124 _Static_assert(offsetof(struct proc, p_emuldata) == 0x318,
 125     "struct proc KBI p_emuldata");
 126 #endif
 127
 128 SDT_PROVIDER_DECLARE(proc);
 129 SDT_PROBE_DEFINE(proc, , , lwp__exit);
 130
 131 /*
 132  * thread related storage.
 133  */
 134 static uma_zone_t thread_zone;
 135
 136 struct thread_domain_data {
 137         struct thread   *tdd_zombies;
 138         int             tdd_reapticks;
 139 } __aligned(CACHE_LINE_SIZE);
 140
 141 static struct thread_domain_data thread_domain_data[MAXMEMDOM];
 142
 143 static struct task      thread_reap_task;
 144 static struct callout   thread_reap_callout;
 145
 146 static void thread_zombie(struct thread *);
 147 static void thread_reap(void);
 148 static void thread_reap_all(void);
 149 static void thread_reap_task_cb(void *, int);
 150 static void thread_reap_callout_cb(void *);
 151 static int thread_unsuspend_one(struct thread *td, struct proc *p,
 152     bool boundary);
 153 static void thread_free_batched(struct thread *td);
 154
 155 static __exclusive_cache_line struct mtx tid_lock;
 156 static bitstr_t *tid_bitmap;
 157
 158 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
 159
 160 static int maxthread;
 161 SYSCTL_INT(_kern, OID_AUTO, maxthread, CTLFLAG_RDTUN,
 162     &maxthread, 0, "Maximum number of threads");
 163
 164 static __exclusive_cache_line int nthreads;
 165
 166 static LIST_HEAD(tidhashhead, thread) *tidhashtbl;
 167 static u_long   tidhash;
 168 static u_long   tidhashlock;
 169 static struct   rwlock *tidhashtbl_lock;
 170 #define TIDHASH(tid)            (&tidhashtbl[(tid) & tidhash])
 171 #define TIDHASHLOCK(tid)        (&tidhashtbl_lock[(tid) & tidhashlock])
 172
 173 EVENTHANDLER_LIST_DEFINE(thread_ctor);
 174 EVENTHANDLER_LIST_DEFINE(thread_dtor);
 175 EVENTHANDLER_LIST_DEFINE(thread_init);
 176 EVENTHANDLER_LIST_DEFINE(thread_fini);
 177
 178 static bool
 179 thread_count_inc_try(void)
 180 {
 181         int nthreads_new;
 182
 183         nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1;
 184         if (nthreads_new >= maxthread - 100) {
 185                 if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 ||
 186                     nthreads_new >= maxthread) {
 187                         atomic_subtract_int(&nthreads, 1);
 188                         return (false);
 189                 }
 190         }
 191         return (true);
 192 }
 193
 194 static bool
 195 thread_count_inc(void)
 196 {
 197         static struct timeval lastfail;
 198         static int curfail;
 199
 200         thread_reap();
 201         if (thread_count_inc_try()) {
 202                 return (true);
 203         }
 204
 205         thread_reap_all();
 206         if (thread_count_inc_try()) {
 207                 return (true);
 208         }
 209
 210         if (ppsratecheck(&lastfail, &curfail, 1)) {
 211                 printf("maxthread limit exceeded by uid %u "
 212                     "(pid %d); consider increasing kern.maxthread\n",
 213                     curthread->td_ucred->cr_ruid, curproc->p_pid);
 214         }
 215         return (false);
 216 }
 217
 218 static void
 219 thread_count_sub(int n)
 220 {
 221
 222         atomic_subtract_int(&nthreads, n);
 223 }
 224
 225 static void
 226 thread_count_dec(void)
 227 {
 228
 229         thread_count_sub(1);
 230 }
 231
 232 static lwpid_t
 233 tid_alloc(void)
 234 {
 235         static lwpid_t trytid;
 236         lwpid_t tid;
 237
 238         mtx_lock(&tid_lock);
 239         /*
 240          * It is an invariant that the bitmap is big enough to hold maxthread
 241          * IDs. If we got to this point there has to be at least one free.
 242          */
 243         if (trytid >= maxthread)
 244                 trytid = 0;
 245         bit_ffc_at(tid_bitmap, trytid, maxthread, &tid);
 246         if (tid == -1) {
 247                 KASSERT(trytid != 0, ("unexpectedly ran out of IDs"));
 248                 trytid = 0;
 249                 bit_ffc_at(tid_bitmap, trytid, maxthread, &tid);
 250                 KASSERT(tid != -1, ("unexpectedly ran out of IDs"));
 251         }
 252         bit_set(tid_bitmap, tid);
 253         trytid = tid + 1;
 254         mtx_unlock(&tid_lock);
 255         return (tid + NO_PID);
 256 }
 257
 258 static void
 259 tid_free_locked(lwpid_t rtid)
 260 {
 261         lwpid_t tid;
 262
 263         mtx_assert(&tid_lock, MA_OWNED);
 264         KASSERT(rtid >= NO_PID,
 265             ("%s: invalid tid %d\n", __func__, rtid));
 266         tid = rtid - NO_PID;
 267         KASSERT(bit_test(tid_bitmap, tid) != 0,
 268             ("thread ID %d not allocated\n", rtid));
 269         bit_clear(tid_bitmap, tid);
 270 }
 271
 272 static void
 273 tid_free(lwpid_t rtid)
 274 {
 275
 276         mtx_lock(&tid_lock);
 277         tid_free_locked(rtid);
 278         mtx_unlock(&tid_lock);
 279 }
 280
 281 static void
 282 tid_free_batch(lwpid_t *batch, int n)
 283 {
 284         int i;
 285
 286         mtx_lock(&tid_lock);
 287         for (i = 0; i < n; i++) {
 288                 tid_free_locked(batch[i]);
 289         }
 290         mtx_unlock(&tid_lock);
 291 }
 292
 293 /*
 294  * Batching for thread reapping.
 295  */
 296 struct tidbatch {
 297         lwpid_t tab[16];
 298         int n;
 299 };
 300
 301 static void
 302 tidbatch_prep(struct tidbatch *tb)
 303 {
 304
 305         tb->n = 0;
 306 }
 307
 308 static void
 309 tidbatch_add(struct tidbatch *tb, struct thread *td)
 310 {
 311
 312         KASSERT(tb->n < nitems(tb->tab),
 313             ("%s: count too high %d", __func__, tb->n));
 314         tb->tab[tb->n] = td->td_tid;
 315         tb->n++;
 316 }
 317
 318 static void
 319 tidbatch_process(struct tidbatch *tb)
 320 {
 321
 322         KASSERT(tb->n <= nitems(tb->tab),
 323             ("%s: count too high %d", __func__, tb->n));
 324         if (tb->n == nitems(tb->tab)) {
 325                 tid_free_batch(tb->tab, tb->n);
 326                 tb->n = 0;
 327         }
 328 }
 329
 330 static void
 331 tidbatch_final(struct tidbatch *tb)
 332 {
 333
 334         KASSERT(tb->n <= nitems(tb->tab),
 335             ("%s: count too high %d", __func__, tb->n));
 336         if (tb->n != 0) {
 337                 tid_free_batch(tb->tab, tb->n);
 338         }
 339 }
 340
 341 /*
 342  * Batching thread count free, for consistency
 343  */
 344 struct tdcountbatch {
 345         int n;
 346 };
 347
 348 static void
 349 tdcountbatch_prep(struct tdcountbatch *tb)
 350 {
 351
 352         tb->n = 0;
 353 }
 354
 355 static void
 356 tdcountbatch_add(struct tdcountbatch *tb, struct thread *td __unused)
 357 {
 358
 359         tb->n++;
 360 }
 361
 362 static void
 363 tdcountbatch_process(struct tdcountbatch *tb)
 364 {
 365
 366         if (tb->n == 32) {
 367                 thread_count_sub(tb->n);
 368                 tb->n = 0;
 369         }
 370 }
 371
 372 static void
 373 tdcountbatch_final(struct tdcountbatch *tb)
 374 {
 375
 376         if (tb->n != 0) {
 377                 thread_count_sub(tb->n);
 378         }
 379 }
 380
 381 /*
 382  * Prepare a thread for use.
 383  */
 384 static int
 385 thread_ctor(void *mem, int size, void *arg, int flags)
 386 {
 387         struct thread   *td;
 388
 389         td = (struct thread *)mem;
 390         TD_SET_STATE(td, TDS_INACTIVE);
 391         td->td_lastcpu = td->td_oncpu = NOCPU;
 392
 393         /*
 394          * Note that td_critnest begins life as 1 because the thread is not
 395          * running and is thereby implicitly waiting to be on the receiving
 396          * end of a context switch.
 397          */
 398         td->td_critnest = 1;
 399         td->td_lend_user_pri = PRI_MAX;
 400 #ifdef AUDIT
 401         audit_thread_alloc(td);
 402 #endif
 403 #ifdef KDTRACE_HOOKS
 404         kdtrace_thread_ctor(td);
 405 #endif
 406         umtx_thread_alloc(td);
 407         MPASS(td->td_sel == NULL);
 408         return (0);
 409 }
 410
 411 /*
 412  * Reclaim a thread after use.
 413  */
 414 static void
 415 thread_dtor(void *mem, int size, void *arg)
 416 {
 417         struct thread *td;
 418
 419         td = (struct thread *)mem;
 420
 421 #ifdef INVARIANTS
 422         /* Verify that this thread is in a safe state to free. */
 423         switch (TD_GET_STATE(td)) {
 424         case TDS_INHIBITED:
 425         case TDS_RUNNING:
 426         case TDS_CAN_RUN:
 427         case TDS_RUNQ:
 428                 /*
 429                  * We must never unlink a thread that is in one of
 430                  * these states, because it is currently active.
 431                  */
 432                 panic("bad state for thread unlinking");
 433                 /* NOTREACHED */
 434         case TDS_INACTIVE:
 435                 break;
 436         default:
 437                 panic("bad thread state");
 438                 /* NOTREACHED */
 439         }
 440 #endif
 441 #ifdef AUDIT
 442         audit_thread_free(td);
 443 #endif
 444 #ifdef KDTRACE_HOOKS
 445         kdtrace_thread_dtor(td);
 446 #endif
 447         /* Free all OSD associated to this thread. */
 448         osd_thread_exit(td);
 449         ast_kclear(td);
 450         seltdfini(td);
 451 }
 452
 453 /*
 454  * Initialize type-stable parts of a thread (when newly created).
 455  */
 456 static int
 457 thread_init(void *mem, int size, int flags)
 458 {
 459         struct thread *td;
 460
 461         td = (struct thread *)mem;
 462
 463         td->td_allocdomain = vm_phys_domain(vtophys(td));
 464         td->td_sleepqueue = sleepq_alloc();
 465         td->td_turnstile = turnstile_alloc();
 466         td->td_rlqe = NULL;
 467         EVENTHANDLER_DIRECT_INVOKE(thread_init, td);
 468         umtx_thread_init(td);
 469         td->td_kstack = 0;
 470         td->td_sel = NULL;
 471         return (0);
 472 }
 473
 474 /*
 475  * Tear down type-stable parts of a thread (just before being discarded).
 476  */
 477 static void
 478 thread_fini(void *mem, int size)
 479 {
 480         struct thread *td;
 481
 482         td = (struct thread *)mem;
 483         EVENTHANDLER_DIRECT_INVOKE(thread_fini, td);
 484         rlqentry_free(td->td_rlqe);
 485         turnstile_free(td->td_turnstile);
 486         sleepq_free(td->td_sleepqueue);
 487         umtx_thread_fini(td);
 488         MPASS(td->td_sel == NULL);
 489 }
 490
 491 /*
 492  * For a newly created process,
 493  * link up all the structures and its initial threads etc.
 494  * called from:
 495  * {arch}/{arch}/machdep.c   {arch}_init(), init386() etc.
 496  * proc_dtor() (should go away)
 497  * proc_init()
 498  */
 499 void
 500 proc_linkup0(struct proc *p, struct thread *td)
 501 {
 502         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
 503         proc_linkup(p, td);
 504 }
 505
 506 void
 507 proc_linkup(struct proc *p, struct thread *td)
 508 {
 509
 510         sigqueue_init(&p->p_sigqueue, p);
 511         p->p_ksi = ksiginfo_alloc(M_WAITOK);
 512         if (p->p_ksi != NULL) {
 513                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
 514                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
 515         }
 516         LIST_INIT(&p->p_mqnotifier);
 517         p->p_numthreads = 0;
 518         thread_link(td, p);
 519 }
 520
 521 static void
 522 ast_suspend(struct thread *td, int tda __unused)
 523 {
 524         struct proc *p;
 525
 526         p = td->td_proc;
 527         /*
 528          * We need to check to see if we have to exit or wait due to a
 529          * single threading requirement or some other STOP condition.
 530          */
 531         PROC_LOCK(p);
 532         thread_suspend_check(0);
 533         PROC_UNLOCK(p);
 534 }
 535
 536 extern int max_threads_per_proc;
 537
 538 /*
 539  * Initialize global thread allocation resources.
 540  */
 541 void
 542 threadinit(void)
 543 {
 544         u_long i;
 545         lwpid_t tid0;
 546
 547         /*
 548          * Place an upper limit on threads which can be allocated.
 549          *
 550          * Note that other factors may make the de facto limit much lower.
 551          *
 552          * Platform limits are somewhat arbitrary but deemed "more than good
 553          * enough" for the foreseable future.
 554          */
 555         if (maxthread == 0) {
 556 #ifdef _LP64
 557                 maxthread = MIN(maxproc * max_threads_per_proc, 1000000);
 558 #else
 559                 maxthread = MIN(maxproc * max_threads_per_proc, 100000);
 560 #endif
 561         }
 562
 563         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
 564         tid_bitmap = bit_alloc(maxthread, M_TIDHASH, M_WAITOK);
 565         /*
 566          * Handle thread0.
 567          */
 568         thread_count_inc();
 569         tid0 = tid_alloc();
 570         if (tid0 != THREAD0_TID)
 571                 panic("tid0 %d != %d\n", tid0, THREAD0_TID);
 572
 573         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
 574             thread_ctor, thread_dtor, thread_init, thread_fini,
 575             32 - 1, UMA_ZONE_NOFREE);
 576         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
 577         tidhashlock = (tidhash + 1) / 64;
 578         if (tidhashlock > 0)
 579                 tidhashlock--;
 580         tidhashtbl_lock = malloc(sizeof(*tidhashtbl_lock) * (tidhashlock + 1),
 581             M_TIDHASH, M_WAITOK | M_ZERO);
 582         for (i = 0; i < tidhashlock + 1; i++)
 583                 rw_init(&tidhashtbl_lock[i], "tidhash");
 584
 585         TASK_INIT(&thread_reap_task, 0, thread_reap_task_cb, NULL);
 586         callout_init(&thread_reap_callout, 1);
 587         callout_reset(&thread_reap_callout, 5 * hz,
 588             thread_reap_callout_cb, NULL);
 589         ast_register(TDA_SUSPEND, ASTR_ASTF_REQUIRED, 0, ast_suspend);
 590 }
 591
 592 /*
 593  * Place an unused thread on the zombie list.
 594  */
 595 void
 596 thread_zombie(struct thread *td)
 597 {
 598         struct thread_domain_data *tdd;
 599         struct thread *ztd;
 600
 601         tdd = &thread_domain_data[td->td_allocdomain];
 602         ztd = atomic_load_ptr(&tdd->tdd_zombies);
 603         for (;;) {
 604                 td->td_zombie = ztd;
 605                 if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies,
 606                     (uintptr_t *)&ztd, (uintptr_t)td))
 607                         break;
 608                 continue;
 609         }
 610 }
 611
 612 /*
 613  * Release a thread that has exited after cpu_throw().
 614  */
 615 void
 616 thread_stash(struct thread *td)
 617 {
 618         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
 619         thread_zombie(td);
 620 }
 621
 622 /*
 623  * Reap zombies from passed domain.
 624  */
 625 static void
 626 thread_reap_domain(struct thread_domain_data *tdd)
 627 {
 628         struct thread *itd, *ntd;
 629         struct tidbatch tidbatch;
 630         struct credbatch credbatch;
 631         struct limbatch limbatch;
 632         struct tdcountbatch tdcountbatch;
 633
 634         /*
 635          * Reading upfront is pessimal if followed by concurrent atomic_swap,
 636          * but most of the time the list is empty.
 637          */
 638         if (tdd->tdd_zombies == NULL)
 639                 return;
 640
 641         itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies,
 642             (uintptr_t)NULL);
 643         if (itd == NULL)
 644                 return;
 645
 646         /*
 647          * Multiple CPUs can get here, the race is fine as ticks is only
 648          * advisory.
 649          */
 650         tdd->tdd_reapticks = ticks;
 651
 652         tidbatch_prep(&tidbatch);
 653         credbatch_prep(&credbatch);
 654         limbatch_prep(&limbatch);
 655         tdcountbatch_prep(&tdcountbatch);
 656
 657         while (itd != NULL) {
 658                 ntd = itd->td_zombie;
 659                 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd);
 660
 661                 tidbatch_add(&tidbatch, itd);
 662                 credbatch_add(&credbatch, itd);
 663                 limbatch_add(&limbatch, itd);
 664                 tdcountbatch_add(&tdcountbatch, itd);
 665
 666                 thread_free_batched(itd);
 667
 668                 tidbatch_process(&tidbatch);
 669                 credbatch_process(&credbatch);
 670                 limbatch_process(&limbatch);
 671                 tdcountbatch_process(&tdcountbatch);
 672
 673                 itd = ntd;
 674         }
 675
 676         tidbatch_final(&tidbatch);
 677         credbatch_final(&credbatch);
 678         limbatch_final(&limbatch);
 679         tdcountbatch_final(&tdcountbatch);
 680 }
 681
 682 /*
 683  * Reap zombies from all domains.
 684  */
 685 static void
 686 thread_reap_all(void)
 687 {
 688         struct thread_domain_data *tdd;
 689         int i, domain;
 690
 691         domain = PCPU_GET(domain);
 692         for (i = 0; i < vm_ndomains; i++) {
 693                 tdd = &thread_domain_data[(i + domain) % vm_ndomains];
 694                 thread_reap_domain(tdd);
 695         }
 696 }
 697
 698 /*
 699  * Reap zombies from local domain.
 700  */
 701 static void
 702 thread_reap(void)
 703 {
 704         struct thread_domain_data *tdd;
 705         int domain;
 706
 707         domain = PCPU_GET(domain);
 708         tdd = &thread_domain_data[domain];
 709
 710         thread_reap_domain(tdd);
 711 }
 712
 713 static void
 714 thread_reap_task_cb(void *arg __unused, int pending __unused)
 715 {
 716
 717         thread_reap_all();
 718 }
 719
 720 static void
 721 thread_reap_callout_cb(void *arg __unused)
 722 {
 723         struct thread_domain_data *tdd;
 724         int i, cticks, lticks;
 725         bool wantreap;
 726
 727         wantreap = false;
 728         cticks = atomic_load_int(&ticks);
 729         for (i = 0; i < vm_ndomains; i++) {
 730                 tdd = &thread_domain_data[i];
 731                 lticks = tdd->tdd_reapticks;
 732                 if (tdd->tdd_zombies != NULL &&
 733                     (u_int)(cticks - lticks) > 5 * hz) {
 734                         wantreap = true;
 735                         break;
 736                 }
 737         }
 738
 739         if (wantreap)
 740                 taskqueue_enqueue(taskqueue_thread, &thread_reap_task);
 741         callout_reset(&thread_reap_callout, 5 * hz,
 742             thread_reap_callout_cb, NULL);
 743 }
 744
 745 /*
 746  * Calling this function guarantees that any thread that exited before
 747  * the call is reaped when the function returns.  By 'exited' we mean
 748  * a thread removed from the process linkage with thread_unlink().
 749  * Practically this means that caller must lock/unlock corresponding
 750  * process lock before the call, to synchronize with thread_exit().
 751  */
 752 void
 753 thread_reap_barrier(void)
 754 {
 755         struct task *t;
 756
 757         /*
 758          * First do context switches to each CPU to ensure that all
 759          * PCPU pc_deadthreads are moved to zombie list.
 760          */
 761         quiesce_all_cpus("", PDROP);
 762
 763         /*
 764          * Second, fire the task in the same thread as normal
 765          * thread_reap() is done, to serialize reaping.
 766          */
 767         t = malloc(sizeof(*t), M_TEMP, M_WAITOK);
 768         TASK_INIT(t, 0, thread_reap_task_cb, t);
 769         taskqueue_enqueue(taskqueue_thread, t);
 770         taskqueue_drain(taskqueue_thread, t);
 771         free(t, M_TEMP);
 772 }
 773
 774 /*
 775  * Allocate a thread.
 776  */
 777 struct thread *
 778 thread_alloc(int pages)
 779 {
 780         struct thread *td;
 781         lwpid_t tid;
 782
 783         if (!thread_count_inc()) {
 784                 return (NULL);
 785         }
 786
 787         tid = tid_alloc();
 788         td = uma_zalloc(thread_zone, M_WAITOK);
 789         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
 790         if (!vm_thread_new(td, pages)) {
 791                 uma_zfree(thread_zone, td);
 792                 tid_free(tid);
 793                 thread_count_dec();
 794                 return (NULL);
 795         }
 796         td->td_tid = tid;
 797         bzero(&td->td_sa.args, sizeof(td->td_sa.args));
 798         kmsan_thread_alloc(td);
 799         cpu_thread_alloc(td);
 800         EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td);
 801         return (td);
 802 }
 803
 804 int
 805 thread_alloc_stack(struct thread *td, int pages)
 806 {
 807
 808         KASSERT(td->td_kstack == 0,
 809             ("thread_alloc_stack called on a thread with kstack"));
 810         if (!vm_thread_new(td, pages))
 811                 return (0);
 812         cpu_thread_alloc(td);
 813         return (1);
 814 }
 815
 816 /*
 817  * Deallocate a thread.
 818  */
 819 static void
 820 thread_free_batched(struct thread *td)
 821 {
 822
 823         lock_profile_thread_exit(td);
 824         if (td->td_cpuset)
 825                 cpuset_rel(td->td_cpuset);
 826         td->td_cpuset = NULL;
 827         cpu_thread_free(td);
 828         if (td->td_kstack != 0)
 829                 vm_thread_dispose(td);
 830         callout_drain(&td->td_slpcallout);
 831         /*
 832          * Freeing handled by the caller.
 833          */
 834         td->td_tid = -1;
 835         kmsan_thread_free(td);
 836         uma_zfree(thread_zone, td);
 837 }
 838
 839 void
 840 thread_free(struct thread *td)
 841 {
 842         lwpid_t tid;
 843
 844         EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td);
 845         tid = td->td_tid;
 846         thread_free_batched(td);
 847         tid_free(tid);
 848         thread_count_dec();
 849 }
 850
 851 void
 852 thread_cow_get_proc(struct thread *newtd, struct proc *p)
 853 {
 854
 855         PROC_LOCK_ASSERT(p, MA_OWNED);
 856         newtd->td_realucred = crcowget(p->p_ucred);
 857         newtd->td_ucred = newtd->td_realucred;
 858         newtd->td_limit = lim_hold(p->p_limit);
 859         newtd->td_cowgen = p->p_cowgen;
 860 }
 861
 862 void
 863 thread_cow_get(struct thread *newtd, struct thread *td)
 864 {
 865
 866         MPASS(td->td_realucred == td->td_ucred);
 867         newtd->td_realucred = crcowget(td->td_realucred);
 868         newtd->td_ucred = newtd->td_realucred;
 869         newtd->td_limit = lim_hold(td->td_limit);
 870         newtd->td_cowgen = td->td_cowgen;
 871 }
 872
 873 void
 874 thread_cow_free(struct thread *td)
 875 {
 876
 877         if (td->td_realucred != NULL)
 878                 crcowfree(td);
 879         if (td->td_limit != NULL)
 880                 lim_free(td->td_limit);
 881 }
 882
 883 void
 884 thread_cow_update(struct thread *td)
 885 {
 886         struct proc *p;
 887         struct ucred *oldcred;
 888         struct plimit *oldlimit;
 889
 890         p = td->td_proc;
 891         PROC_LOCK(p);
 892         oldcred = crcowsync();
 893         oldlimit = lim_cowsync();
 894         td->td_cowgen = p->p_cowgen;
 895         PROC_UNLOCK(p);
 896         if (oldcred != NULL)
 897                 crfree(oldcred);
 898         if (oldlimit != NULL)
 899                 lim_free(oldlimit);
 900 }
 901
 902 void
 903 thread_cow_synced(struct thread *td)
 904 {
 905         struct proc *p;
 906
 907         p = td->td_proc;
 908         PROC_LOCK_ASSERT(p, MA_OWNED);
 909         MPASS(td->td_cowgen != p->p_cowgen);
 910         MPASS(td->td_ucred == p->p_ucred);
 911         MPASS(td->td_limit == p->p_limit);
 912         td->td_cowgen = p->p_cowgen;
 913 }
 914
 915 /*
 916  * Discard the current thread and exit from its context.
 917  * Always called with scheduler locked.
 918  *
 919  * Because we can't free a thread while we're operating under its context,
 920  * push the current thread into our CPU's deadthread holder. This means
 921  * we needn't worry about someone else grabbing our context before we
 922  * do a cpu_throw().
 923  */
 924 void
 925 thread_exit(void)
 926 {
 927         uint64_t runtime, new_switchtime;
 928         struct thread *td;
 929         struct thread *td2;
 930         struct proc *p;
 931         int wakeup_swapper;
 932
 933         td = curthread;
 934         p = td->td_proc;
 935
 936         PROC_SLOCK_ASSERT(p, MA_OWNED);
 937         mtx_assert(&Giant, MA_NOTOWNED);
 938
 939         PROC_LOCK_ASSERT(p, MA_OWNED);
 940         KASSERT(p != NULL, ("thread exiting without a process"));
 941         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
 942             (long)p->p_pid, td->td_name);
 943         SDT_PROBE0(proc, , , lwp__exit);
 944         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
 945         MPASS(td->td_realucred == td->td_ucred);
 946
 947         /*
 948          * drop FPU & debug register state storage, or any other
 949          * architecture specific resources that
 950          * would not be on a new untouched process.
 951          */
 952         cpu_thread_exit(td);
 953
 954         /*
 955          * The last thread is left attached to the process
 956          * So that the whole bundle gets recycled. Skip
 957          * all this stuff if we never had threads.
 958          * EXIT clears all sign of other threads when
 959          * it goes to single threading, so the last thread always
 960          * takes the short path.
 961          */
 962         if (p->p_flag & P_HADTHREADS) {
 963                 if (p->p_numthreads > 1) {
 964                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
 965                         thread_unlink(td);
 966                         td2 = FIRST_THREAD_IN_PROC(p);
 967                         sched_exit_thread(td2, td);
 968
 969                         /*
 970                          * The test below is NOT true if we are the
 971                          * sole exiting thread. P_STOPPED_SINGLE is unset
 972                          * in exit1() after it is the only survivor.
 973                          */
 974                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 975                                 if (p->p_numthreads == p->p_suspcount) {
 976                                         thread_lock(p->p_singlethread);
 977                                         wakeup_swapper = thread_unsuspend_one(
 978                                                 p->p_singlethread, p, false);
 979                                         if (wakeup_swapper)
 980                                                 kick_proc0();
 981                                 }
 982                         }
 983
 984                         PCPU_SET(deadthread, td);
 985                 } else {
 986                         /*
 987                          * The last thread is exiting.. but not through exit()
 988                          */
 989                         panic ("thread_exit: Last thread exiting on its own");
 990                 }
 991         }
 992 #ifdef  HWPMC_HOOKS
 993         /*
 994          * If this thread is part of a process that is being tracked by hwpmc(4),
 995          * inform the module of the thread's impending exit.
 996          */
 997         if (PMC_PROC_IS_USING_PMCS(td->td_proc)) {
 998                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 999                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL);
1000         } else if (PMC_SYSTEM_SAMPLING_ACTIVE())
1001                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL);
1002 #endif
1003         PROC_UNLOCK(p);
1004         PROC_STATLOCK(p);
1005         thread_lock(td);
1006         PROC_SUNLOCK(p);
1007
1008         /* Do the same timestamp bookkeeping that mi_switch() would do. */
1009         new_switchtime = cpu_ticks();
1010         runtime = new_switchtime - PCPU_GET(switchtime);
1011         td->td_runtime += runtime;
1012         td->td_incruntime += runtime;
1013         PCPU_SET(switchtime, new_switchtime);
1014         PCPU_SET(switchticks, ticks);
1015         VM_CNT_INC(v_swtch);
1016
1017         /* Save our resource usage in our process. */
1018         td->td_ru.ru_nvcsw++;
1019         ruxagg_locked(p, td);
1020         rucollect(&p->p_ru, &td->td_ru);
1021         PROC_STATUNLOCK(p);
1022
1023         TD_SET_STATE(td, TDS_INACTIVE);
1024 #ifdef WITNESS
1025         witness_thread_exit(td);
1026 #endif
1027         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
1028         sched_throw(td);
1029         panic("I'm a teapot!");
1030         /* NOTREACHED */
1031 }
1032
1033 /*
1034  * Do any thread specific cleanups that may be needed in wait()
1035  * called with Giant, proc and schedlock not held.
1036  */
1037 void
1038 thread_wait(struct proc *p)
1039 {
1040         struct thread *td;
1041
1042         mtx_assert(&Giant, MA_NOTOWNED);
1043         KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()"));
1044         KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking"));
1045         td = FIRST_THREAD_IN_PROC(p);
1046         /* Lock the last thread so we spin until it exits cpu_throw(). */
1047         thread_lock(td);
1048         thread_unlock(td);
1049         lock_profile_thread_exit(td);
1050         cpuset_rel(td->td_cpuset);
1051         td->td_cpuset = NULL;
1052         cpu_thread_clean(td);
1053         thread_cow_free(td);
1054         callout_drain(&td->td_slpcallout);
1055         thread_reap();  /* check for zombie threads etc. */
1056 }
1057
1058 /*
1059  * Link a thread to a process.
1060  * set up anything that needs to be initialized for it to
1061  * be used by the process.
1062  */
1063 void
1064 thread_link(struct thread *td, struct proc *p)
1065 {
1066
1067         /*
1068          * XXX This can't be enabled because it's called for proc0 before
1069          * its lock has been created.
1070          * PROC_LOCK_ASSERT(p, MA_OWNED);
1071          */
1072         TD_SET_STATE(td, TDS_INACTIVE);
1073         td->td_proc     = p;
1074         td->td_flags    = TDF_INMEM;
1075
1076         LIST_INIT(&td->td_contested);
1077         LIST_INIT(&td->td_lprof[0]);
1078         LIST_INIT(&td->td_lprof[1]);
1079 #ifdef EPOCH_TRACE
1080         SLIST_INIT(&td->td_epochs);
1081 #endif
1082         sigqueue_init(&td->td_sigqueue, p);
1083         callout_init(&td->td_slpcallout, 1);
1084         TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist);
1085         p->p_numthreads++;
1086 }
1087
1088 /*
1089  * Called from:
1090  *  thread_exit()
1091  */
1092 void
1093 thread_unlink(struct thread *td)
1094 {
1095         struct proc *p = td->td_proc;
1096
1097         PROC_LOCK_ASSERT(p, MA_OWNED);
1098 #ifdef EPOCH_TRACE
1099         MPASS(SLIST_EMPTY(&td->td_epochs));
1100 #endif
1101
1102         TAILQ_REMOVE(&p->p_threads, td, td_plist);
1103         p->p_numthreads--;
1104         /* could clear a few other things here */
1105         /* Must  NOT clear links to proc! */
1106 }
1107
1108 static int
1109 calc_remaining(struct proc *p, int mode)
1110 {
1111         int remaining;
1112
1113         PROC_LOCK_ASSERT(p, MA_OWNED);
1114         PROC_SLOCK_ASSERT(p, MA_OWNED);
1115         if (mode == SINGLE_EXIT)
1116                 remaining = p->p_numthreads;
1117         else if (mode == SINGLE_BOUNDARY)
1118                 remaining = p->p_numthreads - p->p_boundary_count;
1119         else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC)
1120                 remaining = p->p_numthreads - p->p_suspcount;
1121         else
1122                 panic("calc_remaining: wrong mode %d", mode);
1123         return (remaining);
1124 }
1125
1126 static int
1127 remain_for_mode(int mode)
1128 {
1129
1130         return (mode == SINGLE_ALLPROC ? 0 : 1);
1131 }
1132
1133 static int
1134 weed_inhib(int mode, struct thread *td2, struct proc *p)
1135 {
1136         int wakeup_swapper;
1137
1138         PROC_LOCK_ASSERT(p, MA_OWNED);
1139         PROC_SLOCK_ASSERT(p, MA_OWNED);
1140         THREAD_LOCK_ASSERT(td2, MA_OWNED);
1141
1142         wakeup_swapper = 0;
1143
1144         /*
1145          * Since the thread lock is dropped by the scheduler we have
1146          * to retry to check for races.
1147          */
1148 restart:
1149         switch (mode) {
1150         case SINGLE_EXIT:
1151                 if (TD_IS_SUSPENDED(td2)) {
1152                         wakeup_swapper |= thread_unsuspend_one(td2, p, true);
1153                         thread_lock(td2);
1154                         goto restart;
1155                 }
1156                 if (TD_CAN_ABORT(td2)) {
1157                         wakeup_swapper |= sleepq_abort(td2, EINTR);
1158                         return (wakeup_swapper);
1159                 }
1160                 break;
1161         case SINGLE_BOUNDARY:
1162         case SINGLE_NO_EXIT:
1163                 if (TD_IS_SUSPENDED(td2) &&
1164                     (td2->td_flags & TDF_BOUNDARY) == 0) {
1165                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
1166                         thread_lock(td2);
1167                         goto restart;
1168                 }
1169                 if (TD_CAN_ABORT(td2)) {
1170                         wakeup_swapper |= sleepq_abort(td2, ERESTART);
1171                         return (wakeup_swapper);
1172                 }
1173                 break;
1174         case SINGLE_ALLPROC:
1175                 /*
1176                  * ALLPROC suspend tries to avoid spurious EINTR for
1177                  * threads sleeping interruptable, by suspending the
1178                  * thread directly, similarly to sig_suspend_threads().
1179                  * Since such sleep is not neccessary performed at the user
1180                  * boundary, TDF_ALLPROCSUSP is used to avoid immediate
1181                  * un-suspend.
1182                  */
1183                 if (TD_IS_SUSPENDED(td2) &&
1184                     (td2->td_flags & TDF_ALLPROCSUSP) == 0) {
1185                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
1186                         thread_lock(td2);
1187                         goto restart;
1188                 }
1189                 if (TD_CAN_ABORT(td2)) {
1190                         td2->td_flags |= TDF_ALLPROCSUSP;
1191                         wakeup_swapper |= sleepq_abort(td2, ERESTART);
1192                         return (wakeup_swapper);
1193                 }
1194                 break;
1195         default:
1196                 break;
1197         }
1198         thread_unlock(td2);
1199         return (wakeup_swapper);
1200 }
1201
1202 /*
1203  * Enforce single-threading.
1204  *
1205  * Returns 1 if the caller must abort (another thread is waiting to
1206  * exit the process or similar). Process is locked!
1207  * Returns 0 when you are successfully the only thread running.
1208  * A process has successfully single threaded in the suspend mode when
1209  * There are no threads in user mode. Threads in the kernel must be
1210  * allowed to continue until they get to the user boundary. They may even
1211  * copy out their return values and data before suspending. They may however be
1212  * accelerated in reaching the user boundary as we will wake up
1213  * any sleeping threads that are interruptable. (PCATCH).
1214  */
1215 int
1216 thread_single(struct proc *p, int mode)
1217 {
1218         struct thread *td;
1219         struct thread *td2;
1220         int remaining, wakeup_swapper;
1221
1222         td = curthread;
1223         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1224             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1225             ("invalid mode %d", mode));
1226         /*
1227          * If allowing non-ALLPROC singlethreading for non-curproc
1228          * callers, calc_remaining() and remain_for_mode() should be
1229          * adjusted to also account for td->td_proc != p.  For now
1230          * this is not implemented because it is not used.
1231          */
1232         KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) ||
1233             (mode != SINGLE_ALLPROC && td->td_proc == p),
1234             ("mode %d proc %p curproc %p", mode, p, td->td_proc));
1235         mtx_assert(&Giant, MA_NOTOWNED);
1236         PROC_LOCK_ASSERT(p, MA_OWNED);
1237
1238         /*
1239          * Is someone already single threading?
1240          * Or may be singlethreading is not needed at all.
1241          */
1242         if (mode == SINGLE_ALLPROC) {
1243                 while ((p->p_flag & P_STOPPED_SINGLE) != 0) {
1244                         if ((p->p_flag2 & P2_WEXIT) != 0)
1245                                 return (1);
1246                         msleep(&p->p_flag, &p->p_mtx, PCATCH, "thrsgl", 0);
1247                 }
1248         } else if ((p->p_flag & P_HADTHREADS) == 0)
1249                 return (0);
1250         if (p->p_singlethread != NULL && p->p_singlethread != td)
1251                 return (1);
1252
1253         if (mode == SINGLE_EXIT) {
1254                 p->p_flag |= P_SINGLE_EXIT;
1255                 p->p_flag &= ~P_SINGLE_BOUNDARY;
1256         } else {
1257                 p->p_flag &= ~P_SINGLE_EXIT;
1258                 if (mode == SINGLE_BOUNDARY)
1259                         p->p_flag |= P_SINGLE_BOUNDARY;
1260                 else
1261                         p->p_flag &= ~P_SINGLE_BOUNDARY;
1262         }
1263         if (mode == SINGLE_ALLPROC)
1264                 p->p_flag |= P_TOTAL_STOP;
1265         p->p_flag |= P_STOPPED_SINGLE;
1266         PROC_SLOCK(p);
1267         p->p_singlethread = td;
1268         remaining = calc_remaining(p, mode);
1269         while (remaining != remain_for_mode(mode)) {
1270                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
1271                         goto stopme;
1272                 wakeup_swapper = 0;
1273                 FOREACH_THREAD_IN_PROC(p, td2) {
1274                         if (td2 == td)
1275                                 continue;
1276                         thread_lock(td2);
1277                         ast_sched_locked(td2, TDA_SUSPEND);
1278                         if (TD_IS_INHIBITED(td2)) {
1279                                 wakeup_swapper |= weed_inhib(mode, td2, p);
1280 #ifdef SMP
1281                         } else if (TD_IS_RUNNING(td2)) {
1282                                 forward_signal(td2);
1283                                 thread_unlock(td2);
1284 #endif
1285                         } else
1286                                 thread_unlock(td2);
1287                 }
1288                 if (wakeup_swapper)
1289                         kick_proc0();
1290                 remaining = calc_remaining(p, mode);
1291
1292                 /*
1293                  * Maybe we suspended some threads.. was it enough?
1294                  */
1295                 if (remaining == remain_for_mode(mode))
1296                         break;
1297
1298 stopme:
1299                 /*
1300                  * Wake us up when everyone else has suspended.
1301                  * In the mean time we suspend as well.
1302                  */
1303                 thread_suspend_switch(td, p);
1304                 remaining = calc_remaining(p, mode);
1305         }
1306         if (mode == SINGLE_EXIT) {
1307                 /*
1308                  * Convert the process to an unthreaded process.  The
1309                  * SINGLE_EXIT is called by exit1() or execve(), in
1310                  * both cases other threads must be retired.
1311                  */
1312                 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads"));
1313                 p->p_singlethread = NULL;
1314                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS);
1315
1316                 /*
1317                  * Wait for any remaining threads to exit cpu_throw().
1318                  */
1319                 while (p->p_exitthreads != 0) {
1320                         PROC_SUNLOCK(p);
1321                         PROC_UNLOCK(p);
1322                         sched_relinquish(td);
1323                         PROC_LOCK(p);
1324                         PROC_SLOCK(p);
1325                 }
1326         } else if (mode == SINGLE_BOUNDARY) {
1327                 /*
1328                  * Wait until all suspended threads are removed from
1329                  * the processors.  The thread_suspend_check()
1330                  * increments p_boundary_count while it is still
1331                  * running, which makes it possible for the execve()
1332                  * to destroy vmspace while our other threads are
1333                  * still using the address space.
1334                  *
1335                  * We lock the thread, which is only allowed to
1336                  * succeed after context switch code finished using
1337                  * the address space.
1338                  */
1339                 FOREACH_THREAD_IN_PROC(p, td2) {
1340                         if (td2 == td)
1341                                 continue;
1342                         thread_lock(td2);
1343                         KASSERT((td2->td_flags & TDF_BOUNDARY) != 0,
1344                             ("td %p not on boundary", td2));
1345                         KASSERT(TD_IS_SUSPENDED(td2),
1346                             ("td %p is not suspended", td2));
1347                         thread_unlock(td2);
1348                 }
1349         }
1350         PROC_SUNLOCK(p);
1351         return (0);
1352 }
1353
1354 bool
1355 thread_suspend_check_needed(void)
1356 {
1357         struct proc *p;
1358         struct thread *td;
1359
1360         td = curthread;
1361         p = td->td_proc;
1362         PROC_LOCK_ASSERT(p, MA_OWNED);
1363         return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 &&
1364             (td->td_dbgflags & TDB_SUSPEND) != 0));
1365 }
1366
1367 /*
1368  * Called in from locations that can safely check to see
1369  * whether we have to suspend or at least throttle for a
1370  * single-thread event (e.g. fork).
1371  *
1372  * Such locations include userret().
1373  * If the "return_instead" argument is non zero, the thread must be able to
1374  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
1375  *
1376  * The 'return_instead' argument tells the function if it may do a
1377  * thread_exit() or suspend, or whether the caller must abort and back
1378  * out instead.
1379  *
1380  * If the thread that set the single_threading request has set the
1381  * P_SINGLE_EXIT bit in the process flags then this call will never return
1382  * if 'return_instead' is false, but will exit.
1383  *
1384  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
1385  *---------------+--------------------+---------------------
1386  *       0       | returns 0          |   returns 0 or 1
1387  *               | when ST ends       |   immediately
1388  *---------------+--------------------+---------------------
1389  *       1       | thread exits       |   returns 1
1390  *               |                    |  immediately
1391  * 0 = thread_exit() or suspension ok,
1392  * other = return error instead of stopping the thread.
1393  *
1394  * While a full suspension is under effect, even a single threading
1395  * thread would be suspended if it made this call (but it shouldn't).
1396  * This call should only be made from places where
1397  * thread_exit() would be safe as that may be the outcome unless
1398  * return_instead is set.
1399  */
1400 int
1401 thread_suspend_check(int return_instead)
1402 {
1403         struct thread *td;
1404         struct proc *p;
1405         int wakeup_swapper;
1406
1407         td = curthread;
1408         p = td->td_proc;
1409         mtx_assert(&Giant, MA_NOTOWNED);
1410         PROC_LOCK_ASSERT(p, MA_OWNED);
1411         while (thread_suspend_check_needed()) {
1412                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1413                         KASSERT(p->p_singlethread != NULL,
1414                             ("singlethread not set"));
1415                         /*
1416                          * The only suspension in action is a
1417                          * single-threading. Single threader need not stop.
1418                          * It is safe to access p->p_singlethread unlocked
1419                          * because it can only be set to our address by us.
1420                          */
1421                         if (p->p_singlethread == td)
1422                                 return (0);     /* Exempt from stopping. */
1423                 }
1424                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
1425                         return (EINTR);
1426
1427                 /* Should we goto user boundary if we didn't come from there? */
1428                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1429                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
1430                         return (ERESTART);
1431
1432                 /*
1433                  * Ignore suspend requests if they are deferred.
1434                  */
1435                 if ((td->td_flags & TDF_SBDRY) != 0) {
1436                         KASSERT(return_instead,
1437                             ("TDF_SBDRY set for unsafe thread_suspend_check"));
1438                         KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) !=
1439                             (TDF_SEINTR | TDF_SERESTART),
1440                             ("both TDF_SEINTR and TDF_SERESTART"));
1441                         return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0);
1442                 }
1443
1444                 /*
1445                  * If the process is waiting for us to exit,
1446                  * this thread should just suicide.
1447                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
1448                  */
1449                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
1450                         PROC_UNLOCK(p);
1451
1452                         /*
1453                          * Allow Linux emulation layer to do some work
1454                          * before thread suicide.
1455                          */
1456                         if (__predict_false(p->p_sysent->sv_thread_detach != NULL))
1457                                 (p->p_sysent->sv_thread_detach)(td);
1458                         umtx_thread_exit(td);
1459                         kern_thr_exit(td);
1460                         panic("stopped thread did not exit");
1461                 }
1462
1463                 PROC_SLOCK(p);
1464                 thread_stopped(p);
1465                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1466                         if (p->p_numthreads == p->p_suspcount + 1) {
1467                                 thread_lock(p->p_singlethread);
1468                                 wakeup_swapper = thread_unsuspend_one(
1469                                     p->p_singlethread, p, false);
1470                                 if (wakeup_swapper)
1471                                         kick_proc0();
1472                         }
1473                 }
1474                 PROC_UNLOCK(p);
1475                 thread_lock(td);
1476                 /*
1477                  * When a thread suspends, it just
1478                  * gets taken off all queues.
1479                  */
1480                 thread_suspend_one(td);
1481                 if (return_instead == 0) {
1482                         p->p_boundary_count++;
1483                         td->td_flags |= TDF_BOUNDARY;
1484                 }
1485                 PROC_SUNLOCK(p);
1486                 mi_switch(SW_INVOL | SWT_SUSPEND);
1487                 PROC_LOCK(p);
1488         }
1489         return (0);
1490 }
1491
1492 /*
1493  * Check for possible stops and suspensions while executing a
1494  * casueword or similar transiently failing operation.
1495  *
1496  * The sleep argument controls whether the function can handle a stop
1497  * request itself or it should return ERESTART and the request is
1498  * proceed at the kernel/user boundary in ast.
1499  *
1500  * Typically, when retrying due to casueword(9) failure (rv == 1), we
1501  * should handle the stop requests there, with exception of cases when
1502  * the thread owns a kernel resource, for instance busied the umtx
1503  * key, or when functions return immediately if thread_check_susp()
1504  * returned non-zero.  On the other hand, retrying the whole lock
1505  * operation, we better not stop there but delegate the handling to
1506  * ast.
1507  *
1508  * If the request is for thread termination P_SINGLE_EXIT, we cannot
1509  * handle it at all, and simply return EINTR.
1510  */
1511 int
1512 thread_check_susp(struct thread *td, bool sleep)
1513 {
1514         struct proc *p;
1515         int error;
1516
1517         /*
1518          * The check for TDA_SUSPEND is racy, but it is enough to
1519          * eventually break the lockstep loop.
1520          */
1521         if (!td_ast_pending(td, TDA_SUSPEND))
1522                 return (0);
1523         error = 0;
1524         p = td->td_proc;
1525         PROC_LOCK(p);
1526         if (p->p_flag & P_SINGLE_EXIT)
1527                 error = EINTR;
1528         else if (P_SHOULDSTOP(p) ||
1529             ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND)))
1530                 error = sleep ? thread_suspend_check(0) : ERESTART;
1531         PROC_UNLOCK(p);
1532         return (error);
1533 }
1534
1535 void
1536 thread_suspend_switch(struct thread *td, struct proc *p)
1537 {
1538
1539         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1540         PROC_LOCK_ASSERT(p, MA_OWNED);
1541         PROC_SLOCK_ASSERT(p, MA_OWNED);
1542         /*
1543          * We implement thread_suspend_one in stages here to avoid
1544          * dropping the proc lock while the thread lock is owned.
1545          */
1546         if (p == td->td_proc) {
1547                 thread_stopped(p);
1548                 p->p_suspcount++;
1549         }
1550         PROC_UNLOCK(p);
1551         thread_lock(td);
1552         ast_unsched_locked(td, TDA_SUSPEND);
1553         TD_SET_SUSPENDED(td);
1554         sched_sleep(td, 0);
1555         PROC_SUNLOCK(p);
1556         DROP_GIANT();
1557         mi_switch(SW_VOL | SWT_SUSPEND);
1558         PICKUP_GIANT();
1559         PROC_LOCK(p);
1560         PROC_SLOCK(p);
1561 }
1562
1563 void
1564 thread_suspend_one(struct thread *td)
1565 {
1566         struct proc *p;
1567
1568         p = td->td_proc;
1569         PROC_SLOCK_ASSERT(p, MA_OWNED);
1570         THREAD_LOCK_ASSERT(td, MA_OWNED);
1571         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1572         p->p_suspcount++;
1573         ast_unsched_locked(td, TDA_SUSPEND);
1574         TD_SET_SUSPENDED(td);
1575         sched_sleep(td, 0);
1576 }
1577
1578 static int
1579 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary)
1580 {
1581
1582         THREAD_LOCK_ASSERT(td, MA_OWNED);
1583         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
1584         TD_CLR_SUSPENDED(td);
1585         td->td_flags &= ~TDF_ALLPROCSUSP;
1586         if (td->td_proc == p) {
1587                 PROC_SLOCK_ASSERT(p, MA_OWNED);
1588                 p->p_suspcount--;
1589                 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) {
1590                         td->td_flags &= ~TDF_BOUNDARY;
1591                         p->p_boundary_count--;
1592                 }
1593         }
1594         return (setrunnable(td, 0));
1595 }
1596
1597 void
1598 thread_run_flash(struct thread *td)
1599 {
1600         struct proc *p;
1601
1602         p = td->td_proc;
1603         PROC_LOCK_ASSERT(p, MA_OWNED);
1604
1605         if (TD_ON_SLEEPQ(td))
1606                 sleepq_remove_nested(td);
1607         else
1608                 thread_lock(td);
1609
1610         THREAD_LOCK_ASSERT(td, MA_OWNED);
1611         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
1612
1613         TD_CLR_SUSPENDED(td);
1614         PROC_SLOCK(p);
1615         MPASS(p->p_suspcount > 0);
1616         p->p_suspcount--;
1617         PROC_SUNLOCK(p);
1618         if (setrunnable(td, 0))
1619                 kick_proc0();
1620 }
1621
1622 /*
1623  * Allow all threads blocked by single threading to continue running.
1624  */
1625 void
1626 thread_unsuspend(struct proc *p)
1627 {
1628         struct thread *td;
1629         int wakeup_swapper;
1630
1631         PROC_LOCK_ASSERT(p, MA_OWNED);
1632         PROC_SLOCK_ASSERT(p, MA_OWNED);
1633         wakeup_swapper = 0;
1634         if (!P_SHOULDSTOP(p)) {
1635                 FOREACH_THREAD_IN_PROC(p, td) {
1636                         thread_lock(td);
1637                         if (TD_IS_SUSPENDED(td))
1638                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1639                                     true);
1640                         else
1641                                 thread_unlock(td);
1642                 }
1643         } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1644             p->p_numthreads == p->p_suspcount) {
1645                 /*
1646                  * Stopping everything also did the job for the single
1647                  * threading request. Now we've downgraded to single-threaded,
1648                  * let it continue.
1649                  */
1650                 if (p->p_singlethread->td_proc == p) {
1651                         thread_lock(p->p_singlethread);
1652                         wakeup_swapper = thread_unsuspend_one(
1653                             p->p_singlethread, p, false);
1654                 }
1655         }
1656         if (wakeup_swapper)
1657                 kick_proc0();
1658 }
1659
1660 /*
1661  * End the single threading mode..
1662  */
1663 void
1664 thread_single_end(struct proc *p, int mode)
1665 {
1666         struct thread *td;
1667         int wakeup_swapper;
1668
1669         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1670             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1671             ("invalid mode %d", mode));
1672         PROC_LOCK_ASSERT(p, MA_OWNED);
1673         KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) ||
1674             (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0),
1675             ("mode %d does not match P_TOTAL_STOP", mode));
1676         KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread,
1677             ("thread_single_end from other thread %p %p",
1678             curthread, p->p_singlethread));
1679         KASSERT(mode != SINGLE_BOUNDARY ||
1680             (p->p_flag & P_SINGLE_BOUNDARY) != 0,
1681             ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag));
1682         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY |
1683             P_TOTAL_STOP);
1684         PROC_SLOCK(p);
1685         p->p_singlethread = NULL;
1686         wakeup_swapper = 0;
1687         /*
1688          * If there are other threads they may now run,
1689          * unless of course there is a blanket 'stop order'
1690          * on the process. The single threader must be allowed
1691          * to continue however as this is a bad place to stop.
1692          */
1693         if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) {
1694                 FOREACH_THREAD_IN_PROC(p, td) {
1695                         thread_lock(td);
1696                         if (TD_IS_SUSPENDED(td)) {
1697                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1698                                     true);
1699                         } else
1700                                 thread_unlock(td);
1701                 }
1702         }
1703         KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0,
1704             ("inconsistent boundary count %d", p->p_boundary_count));
1705         PROC_SUNLOCK(p);
1706         if (wakeup_swapper)
1707                 kick_proc0();
1708         wakeup(&p->p_flag);
1709 }
1710
1711 /*
1712  * Locate a thread by number and return with proc lock held.
1713  *
1714  * thread exit establishes proc -> tidhash lock ordering, but lookup
1715  * takes tidhash first and needs to return locked proc.
1716  *
1717  * The problem is worked around by relying on type-safety of both
1718  * structures and doing the work in 2 steps:
1719  * - tidhash-locked lookup which saves both thread and proc pointers
1720  * - proc-locked verification that the found thread still matches
1721  */
1722 static bool
1723 tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp)
1724 {
1725 #define RUN_THRESH      16
1726         struct proc *p;
1727         struct thread *td;
1728         int run;
1729         bool locked;
1730
1731         run = 0;
1732         rw_rlock(TIDHASHLOCK(tid));
1733         locked = true;
1734         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
1735                 if (td->td_tid != tid) {
1736                         run++;
1737                         continue;
1738                 }
1739                 p = td->td_proc;
1740                 if (pid != -1 && p->p_pid != pid) {
1741                         td = NULL;
1742                         break;
1743                 }
1744                 if (run > RUN_THRESH) {
1745                         if (rw_try_upgrade(TIDHASHLOCK(tid))) {
1746                                 LIST_REMOVE(td, td_hash);
1747                                 LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1748                                         td, td_hash);
1749                                 rw_wunlock(TIDHASHLOCK(tid));
1750                                 locked = false;
1751                                 break;
1752                         }
1753                 }
1754                 break;
1755         }
1756         if (locked)
1757                 rw_runlock(TIDHASHLOCK(tid));
1758         if (td == NULL)
1759                 return (false);
1760         *pp = p;
1761         *tdp = td;
1762         return (true);
1763 }
1764
1765 struct thread *
1766 tdfind(lwpid_t tid, pid_t pid)
1767 {
1768         struct proc *p;
1769         struct thread *td;
1770
1771         td = curthread;
1772         if (td->td_tid == tid) {
1773                 if (pid != -1 && td->td_proc->p_pid != pid)
1774                         return (NULL);
1775                 PROC_LOCK(td->td_proc);
1776                 return (td);
1777         }
1778
1779         for (;;) {
1780                 if (!tdfind_hash(tid, pid, &p, &td))
1781                         return (NULL);
1782                 PROC_LOCK(p);
1783                 if (td->td_tid != tid) {
1784                         PROC_UNLOCK(p);
1785                         continue;
1786                 }
1787                 if (td->td_proc != p) {
1788                         PROC_UNLOCK(p);
1789                         continue;
1790                 }
1791                 if (p->p_state == PRS_NEW) {
1792                         PROC_UNLOCK(p);
1793                         return (NULL);
1794                 }
1795                 return (td);
1796         }
1797 }
1798
1799 void
1800 tidhash_add(struct thread *td)
1801 {
1802         rw_wlock(TIDHASHLOCK(td->td_tid));
1803         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1804         rw_wunlock(TIDHASHLOCK(td->td_tid));
1805 }
1806
1807 void
1808 tidhash_remove(struct thread *td)
1809 {
1810
1811         rw_wlock(TIDHASHLOCK(td->td_tid));
1812         LIST_REMOVE(td, td_hash);
1813         rw_wunlock(TIDHASHLOCK(td->td_tid));
1814 }