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