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) == 0x4b0,
  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) == 0x30c,
 113     "struct thread KBI td_frame");
 114 _Static_assert(offsetof(struct thread, td_emuldata) == 0x350,
 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  * Prepare a thread for use.
 343  */
 344 static int
 345 thread_ctor(void *mem, int size, void *arg, int flags)
 346 {
 347         struct thread   *td;
 348
 349         td = (struct thread *)mem;
 350         TD_SET_STATE(td, TDS_INACTIVE);
 351         td->td_lastcpu = td->td_oncpu = NOCPU;
 352
 353         /*
 354          * Note that td_critnest begins life as 1 because the thread is not
 355          * running and is thereby implicitly waiting to be on the receiving
 356          * end of a context switch.
 357          */
 358         td->td_critnest = 1;
 359         td->td_lend_user_pri = PRI_MAX;
 360 #ifdef AUDIT
 361         audit_thread_alloc(td);
 362 #endif
 363 #ifdef KDTRACE_HOOKS
 364         kdtrace_thread_ctor(td);
 365 #endif
 366         umtx_thread_alloc(td);
 367         MPASS(td->td_sel == NULL);
 368         return (0);
 369 }
 370
 371 /*
 372  * Reclaim a thread after use.
 373  */
 374 static void
 375 thread_dtor(void *mem, int size, void *arg)
 376 {
 377         struct thread *td;
 378
 379         td = (struct thread *)mem;
 380
 381 #ifdef INVARIANTS
 382         /* Verify that this thread is in a safe state to free. */
 383         switch (TD_GET_STATE(td)) {
 384         case TDS_INHIBITED:
 385         case TDS_RUNNING:
 386         case TDS_CAN_RUN:
 387         case TDS_RUNQ:
 388                 /*
 389                  * We must never unlink a thread that is in one of
 390                  * these states, because it is currently active.
 391                  */
 392                 panic("bad state for thread unlinking");
 393                 /* NOTREACHED */
 394         case TDS_INACTIVE:
 395                 break;
 396         default:
 397                 panic("bad thread state");
 398                 /* NOTREACHED */
 399         }
 400 #endif
 401 #ifdef AUDIT
 402         audit_thread_free(td);
 403 #endif
 404 #ifdef KDTRACE_HOOKS
 405         kdtrace_thread_dtor(td);
 406 #endif
 407         /* Free all OSD associated to this thread. */
 408         osd_thread_exit(td);
 409         ast_kclear(td);
 410         seltdfini(td);
 411 }
 412
 413 /*
 414  * Initialize type-stable parts of a thread (when newly created).
 415  */
 416 static int
 417 thread_init(void *mem, int size, int flags)
 418 {
 419         struct thread *td;
 420
 421         td = (struct thread *)mem;
 422
 423         td->td_allocdomain = vm_phys_domain(vtophys(td));
 424         td->td_sleepqueue = sleepq_alloc();
 425         td->td_turnstile = turnstile_alloc();
 426         td->td_rlqe = NULL;
 427         EVENTHANDLER_DIRECT_INVOKE(thread_init, td);
 428         umtx_thread_init(td);
 429         td->td_kstack = 0;
 430         td->td_sel = NULL;
 431         return (0);
 432 }
 433
 434 /*
 435  * Tear down type-stable parts of a thread (just before being discarded).
 436  */
 437 static void
 438 thread_fini(void *mem, int size)
 439 {
 440         struct thread *td;
 441
 442         td = (struct thread *)mem;
 443         EVENTHANDLER_DIRECT_INVOKE(thread_fini, td);
 444         rlqentry_free(td->td_rlqe);
 445         turnstile_free(td->td_turnstile);
 446         sleepq_free(td->td_sleepqueue);
 447         umtx_thread_fini(td);
 448         MPASS(td->td_sel == NULL);
 449 }
 450
 451 /*
 452  * For a newly created process,
 453  * link up all the structures and its initial threads etc.
 454  * called from:
 455  * {arch}/{arch}/machdep.c   {arch}_init(), init386() etc.
 456  * proc_dtor() (should go away)
 457  * proc_init()
 458  */
 459 void
 460 proc_linkup0(struct proc *p, struct thread *td)
 461 {
 462         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
 463         proc_linkup(p, td);
 464 }
 465
 466 void
 467 proc_linkup(struct proc *p, struct thread *td)
 468 {
 469
 470         sigqueue_init(&p->p_sigqueue, p);
 471         p->p_ksi = ksiginfo_alloc(M_WAITOK);
 472         if (p->p_ksi != NULL) {
 473                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
 474                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
 475         }
 476         LIST_INIT(&p->p_mqnotifier);
 477         p->p_numthreads = 0;
 478         thread_link(td, p);
 479 }
 480
 481 static void
 482 ast_suspend(struct thread *td, int tda __unused)
 483 {
 484         struct proc *p;
 485
 486         p = td->td_proc;
 487         /*
 488          * We need to check to see if we have to exit or wait due to a
 489          * single threading requirement or some other STOP condition.
 490          */
 491         PROC_LOCK(p);
 492         thread_suspend_check(0);
 493         PROC_UNLOCK(p);
 494 }
 495
 496 extern int max_threads_per_proc;
 497
 498 /*
 499  * Initialize global thread allocation resources.
 500  */
 501 void
 502 threadinit(void)
 503 {
 504         u_long i;
 505         lwpid_t tid0;
 506
 507         /*
 508          * Place an upper limit on threads which can be allocated.
 509          *
 510          * Note that other factors may make the de facto limit much lower.
 511          *
 512          * Platform limits are somewhat arbitrary but deemed "more than good
 513          * enough" for the foreseable future.
 514          */
 515         if (maxthread == 0) {
 516 #ifdef _LP64
 517                 maxthread = MIN(maxproc * max_threads_per_proc, 1000000);
 518 #else
 519                 maxthread = MIN(maxproc * max_threads_per_proc, 100000);
 520 #endif
 521         }
 522
 523         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
 524         tid_bitmap = bit_alloc(maxthread, M_TIDHASH, M_WAITOK);
 525         /*
 526          * Handle thread0.
 527          */
 528         thread_count_inc();
 529         tid0 = tid_alloc();
 530         if (tid0 != THREAD0_TID)
 531                 panic("tid0 %d != %d\n", tid0, THREAD0_TID);
 532
 533         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
 534             thread_ctor, thread_dtor, thread_init, thread_fini,
 535             32 - 1, UMA_ZONE_NOFREE);
 536         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
 537         tidhashlock = (tidhash + 1) / 64;
 538         if (tidhashlock > 0)
 539                 tidhashlock--;
 540         tidhashtbl_lock = malloc(sizeof(*tidhashtbl_lock) * (tidhashlock + 1),
 541             M_TIDHASH, M_WAITOK | M_ZERO);
 542         for (i = 0; i < tidhashlock + 1; i++)
 543                 rw_init(&tidhashtbl_lock[i], "tidhash");
 544
 545         TASK_INIT(&thread_reap_task, 0, thread_reap_task_cb, NULL);
 546         callout_init(&thread_reap_callout, 1);
 547         callout_reset(&thread_reap_callout, 5 * hz,
 548             thread_reap_callout_cb, NULL);
 549         ast_register(TDA_SUSPEND, ASTR_ASTF_REQUIRED, 0, ast_suspend);
 550 }
 551
 552 /*
 553  * Place an unused thread on the zombie list.
 554  */
 555 void
 556 thread_zombie(struct thread *td)
 557 {
 558         struct thread_domain_data *tdd;
 559         struct thread *ztd;
 560
 561         tdd = &thread_domain_data[td->td_allocdomain];
 562         ztd = atomic_load_ptr(&tdd->tdd_zombies);
 563         for (;;) {
 564                 td->td_zombie = ztd;
 565                 if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies,
 566                     (uintptr_t *)&ztd, (uintptr_t)td))
 567                         break;
 568                 continue;
 569         }
 570 }
 571
 572 /*
 573  * Release a thread that has exited after cpu_throw().
 574  */
 575 void
 576 thread_stash(struct thread *td)
 577 {
 578         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
 579         thread_zombie(td);
 580 }
 581
 582 /*
 583  * Reap zombies from passed domain.
 584  */
 585 static void
 586 thread_reap_domain(struct thread_domain_data *tdd)
 587 {
 588         struct thread *itd, *ntd;
 589         struct tidbatch tidbatch;
 590         struct credbatch credbatch;
 591         int tdcount;
 592         struct plimit *lim;
 593         int limcount;
 594
 595         /*
 596          * Reading upfront is pessimal if followed by concurrent atomic_swap,
 597          * but most of the time the list is empty.
 598          */
 599         if (tdd->tdd_zombies == NULL)
 600                 return;
 601
 602         itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies,
 603             (uintptr_t)NULL);
 604         if (itd == NULL)
 605                 return;
 606
 607         /*
 608          * Multiple CPUs can get here, the race is fine as ticks is only
 609          * advisory.
 610          */
 611         tdd->tdd_reapticks = ticks;
 612
 613         tidbatch_prep(&tidbatch);
 614         credbatch_prep(&credbatch);
 615         tdcount = 0;
 616         lim = NULL;
 617         limcount = 0;
 618
 619         while (itd != NULL) {
 620                 ntd = itd->td_zombie;
 621                 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd);
 622                 tidbatch_add(&tidbatch, itd);
 623                 credbatch_add(&credbatch, itd);
 624                 MPASS(itd->td_limit != NULL);
 625                 if (lim != itd->td_limit) {
 626                         if (limcount != 0) {
 627                                 lim_freen(lim, limcount);
 628                                 limcount = 0;
 629                         }
 630                 }
 631                 lim = itd->td_limit;
 632                 limcount++;
 633                 thread_free_batched(itd);
 634                 tidbatch_process(&tidbatch);
 635                 credbatch_process(&credbatch);
 636                 tdcount++;
 637                 if (tdcount == 32) {
 638                         thread_count_sub(tdcount);
 639                         tdcount = 0;
 640                 }
 641                 itd = ntd;
 642         }
 643
 644         tidbatch_final(&tidbatch);
 645         credbatch_final(&credbatch);
 646         if (tdcount != 0) {
 647                 thread_count_sub(tdcount);
 648         }
 649         MPASS(limcount != 0);
 650         lim_freen(lim, limcount);
 651 }
 652
 653 /*
 654  * Reap zombies from all domains.
 655  */
 656 static void
 657 thread_reap_all(void)
 658 {
 659         struct thread_domain_data *tdd;
 660         int i, domain;
 661
 662         domain = PCPU_GET(domain);
 663         for (i = 0; i < vm_ndomains; i++) {
 664                 tdd = &thread_domain_data[(i + domain) % vm_ndomains];
 665                 thread_reap_domain(tdd);
 666         }
 667 }
 668
 669 /*
 670  * Reap zombies from local domain.
 671  */
 672 static void
 673 thread_reap(void)
 674 {
 675         struct thread_domain_data *tdd;
 676         int domain;
 677
 678         domain = PCPU_GET(domain);
 679         tdd = &thread_domain_data[domain];
 680
 681         thread_reap_domain(tdd);
 682 }
 683
 684 static void
 685 thread_reap_task_cb(void *arg __unused, int pending __unused)
 686 {
 687
 688         thread_reap_all();
 689 }
 690
 691 static void
 692 thread_reap_callout_cb(void *arg __unused)
 693 {
 694         struct thread_domain_data *tdd;
 695         int i, cticks, lticks;
 696         bool wantreap;
 697
 698         wantreap = false;
 699         cticks = atomic_load_int(&ticks);
 700         for (i = 0; i < vm_ndomains; i++) {
 701                 tdd = &thread_domain_data[i];
 702                 lticks = tdd->tdd_reapticks;
 703                 if (tdd->tdd_zombies != NULL &&
 704                     (u_int)(cticks - lticks) > 5 * hz) {
 705                         wantreap = true;
 706                         break;
 707                 }
 708         }
 709
 710         if (wantreap)
 711                 taskqueue_enqueue(taskqueue_thread, &thread_reap_task);
 712         callout_reset(&thread_reap_callout, 5 * hz,
 713             thread_reap_callout_cb, NULL);
 714 }
 715
 716 /*
 717  * Calling this function guarantees that any thread that exited before
 718  * the call is reaped when the function returns.  By 'exited' we mean
 719  * a thread removed from the process linkage with thread_unlink().
 720  * Practically this means that caller must lock/unlock corresponding
 721  * process lock before the call, to synchronize with thread_exit().
 722  */
 723 void
 724 thread_reap_barrier(void)
 725 {
 726         struct task *t;
 727
 728         /*
 729          * First do context switches to each CPU to ensure that all
 730          * PCPU pc_deadthreads are moved to zombie list.
 731          */
 732         quiesce_all_cpus("", PDROP);
 733
 734         /*
 735          * Second, fire the task in the same thread as normal
 736          * thread_reap() is done, to serialize reaping.
 737          */
 738         t = malloc(sizeof(*t), M_TEMP, M_WAITOK);
 739         TASK_INIT(t, 0, thread_reap_task_cb, t);
 740         taskqueue_enqueue(taskqueue_thread, t);
 741         taskqueue_drain(taskqueue_thread, t);
 742         free(t, M_TEMP);
 743 }
 744
 745 /*
 746  * Allocate a thread.
 747  */
 748 struct thread *
 749 thread_alloc(int pages)
 750 {
 751         struct thread *td;
 752         lwpid_t tid;
 753
 754         if (!thread_count_inc()) {
 755                 return (NULL);
 756         }
 757
 758         tid = tid_alloc();
 759         td = uma_zalloc(thread_zone, M_WAITOK);
 760         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
 761         if (!vm_thread_new(td, pages)) {
 762                 uma_zfree(thread_zone, td);
 763                 tid_free(tid);
 764                 thread_count_dec();
 765                 return (NULL);
 766         }
 767         td->td_tid = tid;
 768         bzero(&td->td_sa.args, sizeof(td->td_sa.args));
 769         kmsan_thread_alloc(td);
 770         cpu_thread_alloc(td);
 771         EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td);
 772         return (td);
 773 }
 774
 775 int
 776 thread_alloc_stack(struct thread *td, int pages)
 777 {
 778
 779         KASSERT(td->td_kstack == 0,
 780             ("thread_alloc_stack called on a thread with kstack"));
 781         if (!vm_thread_new(td, pages))
 782                 return (0);
 783         cpu_thread_alloc(td);
 784         return (1);
 785 }
 786
 787 /*
 788  * Deallocate a thread.
 789  */
 790 static void
 791 thread_free_batched(struct thread *td)
 792 {
 793
 794         lock_profile_thread_exit(td);
 795         if (td->td_cpuset)
 796                 cpuset_rel(td->td_cpuset);
 797         td->td_cpuset = NULL;
 798         cpu_thread_free(td);
 799         if (td->td_kstack != 0)
 800                 vm_thread_dispose(td);
 801         callout_drain(&td->td_slpcallout);
 802         /*
 803          * Freeing handled by the caller.
 804          */
 805         td->td_tid = -1;
 806         kmsan_thread_free(td);
 807         uma_zfree(thread_zone, td);
 808 }
 809
 810 void
 811 thread_free(struct thread *td)
 812 {
 813         lwpid_t tid;
 814
 815         EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td);
 816         tid = td->td_tid;
 817         thread_free_batched(td);
 818         tid_free(tid);
 819         thread_count_dec();
 820 }
 821
 822 void
 823 thread_cow_get_proc(struct thread *newtd, struct proc *p)
 824 {
 825
 826         PROC_LOCK_ASSERT(p, MA_OWNED);
 827         newtd->td_realucred = crcowget(p->p_ucred);
 828         newtd->td_ucred = newtd->td_realucred;
 829         newtd->td_limit = lim_hold(p->p_limit);
 830         newtd->td_cowgen = p->p_cowgen;
 831 }
 832
 833 void
 834 thread_cow_get(struct thread *newtd, struct thread *td)
 835 {
 836
 837         MPASS(td->td_realucred == td->td_ucred);
 838         newtd->td_realucred = crcowget(td->td_realucred);
 839         newtd->td_ucred = newtd->td_realucred;
 840         newtd->td_limit = lim_hold(td->td_limit);
 841         newtd->td_cowgen = td->td_cowgen;
 842 }
 843
 844 void
 845 thread_cow_free(struct thread *td)
 846 {
 847
 848         if (td->td_realucred != NULL)
 849                 crcowfree(td);
 850         if (td->td_limit != NULL)
 851                 lim_free(td->td_limit);
 852 }
 853
 854 void
 855 thread_cow_update(struct thread *td)
 856 {
 857         struct proc *p;
 858         struct ucred *oldcred;
 859         struct plimit *oldlimit;
 860
 861         p = td->td_proc;
 862         PROC_LOCK(p);
 863         oldcred = crcowsync();
 864         oldlimit = lim_cowsync();
 865         td->td_cowgen = p->p_cowgen;
 866         PROC_UNLOCK(p);
 867         if (oldcred != NULL)
 868                 crfree(oldcred);
 869         if (oldlimit != NULL)
 870                 lim_free(oldlimit);
 871 }
 872
 873 void
 874 thread_cow_synced(struct thread *td)
 875 {
 876         struct proc *p;
 877
 878         p = td->td_proc;
 879         PROC_LOCK_ASSERT(p, MA_OWNED);
 880         MPASS(td->td_cowgen != p->p_cowgen);
 881         MPASS(td->td_ucred == p->p_ucred);
 882         MPASS(td->td_limit == p->p_limit);
 883         td->td_cowgen = p->p_cowgen;
 884 }
 885
 886 /*
 887  * Discard the current thread and exit from its context.
 888  * Always called with scheduler locked.
 889  *
 890  * Because we can't free a thread while we're operating under its context,
 891  * push the current thread into our CPU's deadthread holder. This means
 892  * we needn't worry about someone else grabbing our context before we
 893  * do a cpu_throw().
 894  */
 895 void
 896 thread_exit(void)
 897 {
 898         uint64_t runtime, new_switchtime;
 899         struct thread *td;
 900         struct thread *td2;
 901         struct proc *p;
 902         int wakeup_swapper;
 903
 904         td = curthread;
 905         p = td->td_proc;
 906
 907         PROC_SLOCK_ASSERT(p, MA_OWNED);
 908         mtx_assert(&Giant, MA_NOTOWNED);
 909
 910         PROC_LOCK_ASSERT(p, MA_OWNED);
 911         KASSERT(p != NULL, ("thread exiting without a process"));
 912         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
 913             (long)p->p_pid, td->td_name);
 914         SDT_PROBE0(proc, , , lwp__exit);
 915         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
 916         MPASS(td->td_realucred == td->td_ucred);
 917
 918         /*
 919          * drop FPU & debug register state storage, or any other
 920          * architecture specific resources that
 921          * would not be on a new untouched process.
 922          */
 923         cpu_thread_exit(td);
 924
 925         /*
 926          * The last thread is left attached to the process
 927          * So that the whole bundle gets recycled. Skip
 928          * all this stuff if we never had threads.
 929          * EXIT clears all sign of other threads when
 930          * it goes to single threading, so the last thread always
 931          * takes the short path.
 932          */
 933         if (p->p_flag & P_HADTHREADS) {
 934                 if (p->p_numthreads > 1) {
 935                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
 936                         thread_unlink(td);
 937                         td2 = FIRST_THREAD_IN_PROC(p);
 938                         sched_exit_thread(td2, td);
 939
 940                         /*
 941                          * The test below is NOT true if we are the
 942                          * sole exiting thread. P_STOPPED_SINGLE is unset
 943                          * in exit1() after it is the only survivor.
 944                          */
 945                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 946                                 if (p->p_numthreads == p->p_suspcount) {
 947                                         thread_lock(p->p_singlethread);
 948                                         wakeup_swapper = thread_unsuspend_one(
 949                                                 p->p_singlethread, p, false);
 950                                         if (wakeup_swapper)
 951                                                 kick_proc0();
 952                                 }
 953                         }
 954
 955                         PCPU_SET(deadthread, td);
 956                 } else {
 957                         /*
 958                          * The last thread is exiting.. but not through exit()
 959                          */
 960                         panic ("thread_exit: Last thread exiting on its own");
 961                 }
 962         }
 963 #ifdef  HWPMC_HOOKS
 964         /*
 965          * If this thread is part of a process that is being tracked by hwpmc(4),
 966          * inform the module of the thread's impending exit.
 967          */
 968         if (PMC_PROC_IS_USING_PMCS(td->td_proc)) {
 969                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 970                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL);
 971         } else if (PMC_SYSTEM_SAMPLING_ACTIVE())
 972                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL);
 973 #endif
 974         PROC_UNLOCK(p);
 975         PROC_STATLOCK(p);
 976         thread_lock(td);
 977         PROC_SUNLOCK(p);
 978
 979         /* Do the same timestamp bookkeeping that mi_switch() would do. */
 980         new_switchtime = cpu_ticks();
 981         runtime = new_switchtime - PCPU_GET(switchtime);
 982         td->td_runtime += runtime;
 983         td->td_incruntime += runtime;
 984         PCPU_SET(switchtime, new_switchtime);
 985         PCPU_SET(switchticks, ticks);
 986         VM_CNT_INC(v_swtch);
 987
 988         /* Save our resource usage in our process. */
 989         td->td_ru.ru_nvcsw++;
 990         ruxagg_locked(p, td);
 991         rucollect(&p->p_ru, &td->td_ru);
 992         PROC_STATUNLOCK(p);
 993
 994         TD_SET_STATE(td, TDS_INACTIVE);
 995 #ifdef WITNESS
 996         witness_thread_exit(td);
 997 #endif
 998         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
 999         sched_throw(td);
1000         panic("I'm a teapot!");
1001         /* NOTREACHED */
1002 }
1003
1004 /*
1005  * Do any thread specific cleanups that may be needed in wait()
1006  * called with Giant, proc and schedlock not held.
1007  */
1008 void
1009 thread_wait(struct proc *p)
1010 {
1011         struct thread *td;
1012
1013         mtx_assert(&Giant, MA_NOTOWNED);
1014         KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()"));
1015         KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking"));
1016         td = FIRST_THREAD_IN_PROC(p);
1017         /* Lock the last thread so we spin until it exits cpu_throw(). */
1018         thread_lock(td);
1019         thread_unlock(td);
1020         lock_profile_thread_exit(td);
1021         cpuset_rel(td->td_cpuset);
1022         td->td_cpuset = NULL;
1023         cpu_thread_clean(td);
1024         thread_cow_free(td);
1025         callout_drain(&td->td_slpcallout);
1026         thread_reap();  /* check for zombie threads etc. */
1027 }
1028
1029 /*
1030  * Link a thread to a process.
1031  * set up anything that needs to be initialized for it to
1032  * be used by the process.
1033  */
1034 void
1035 thread_link(struct thread *td, struct proc *p)
1036 {
1037
1038         /*
1039          * XXX This can't be enabled because it's called for proc0 before
1040          * its lock has been created.
1041          * PROC_LOCK_ASSERT(p, MA_OWNED);
1042          */
1043         TD_SET_STATE(td, TDS_INACTIVE);
1044         td->td_proc     = p;
1045         td->td_flags    = TDF_INMEM;
1046
1047         LIST_INIT(&td->td_contested);
1048         LIST_INIT(&td->td_lprof[0]);
1049         LIST_INIT(&td->td_lprof[1]);
1050 #ifdef EPOCH_TRACE
1051         SLIST_INIT(&td->td_epochs);
1052 #endif
1053         sigqueue_init(&td->td_sigqueue, p);
1054         callout_init(&td->td_slpcallout, 1);
1055         TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist);
1056         p->p_numthreads++;
1057 }
1058
1059 /*
1060  * Called from:
1061  *  thread_exit()
1062  */
1063 void
1064 thread_unlink(struct thread *td)
1065 {
1066         struct proc *p = td->td_proc;
1067
1068         PROC_LOCK_ASSERT(p, MA_OWNED);
1069 #ifdef EPOCH_TRACE
1070         MPASS(SLIST_EMPTY(&td->td_epochs));
1071 #endif
1072
1073         TAILQ_REMOVE(&p->p_threads, td, td_plist);
1074         p->p_numthreads--;
1075         /* could clear a few other things here */
1076         /* Must  NOT clear links to proc! */
1077 }
1078
1079 static int
1080 calc_remaining(struct proc *p, int mode)
1081 {
1082         int remaining;
1083
1084         PROC_LOCK_ASSERT(p, MA_OWNED);
1085         PROC_SLOCK_ASSERT(p, MA_OWNED);
1086         if (mode == SINGLE_EXIT)
1087                 remaining = p->p_numthreads;
1088         else if (mode == SINGLE_BOUNDARY)
1089                 remaining = p->p_numthreads - p->p_boundary_count;
1090         else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC)
1091                 remaining = p->p_numthreads - p->p_suspcount;
1092         else
1093                 panic("calc_remaining: wrong mode %d", mode);
1094         return (remaining);
1095 }
1096
1097 static int
1098 remain_for_mode(int mode)
1099 {
1100
1101         return (mode == SINGLE_ALLPROC ? 0 : 1);
1102 }
1103
1104 static int
1105 weed_inhib(int mode, struct thread *td2, struct proc *p)
1106 {
1107         int wakeup_swapper;
1108
1109         PROC_LOCK_ASSERT(p, MA_OWNED);
1110         PROC_SLOCK_ASSERT(p, MA_OWNED);
1111         THREAD_LOCK_ASSERT(td2, MA_OWNED);
1112
1113         wakeup_swapper = 0;
1114
1115         /*
1116          * Since the thread lock is dropped by the scheduler we have
1117          * to retry to check for races.
1118          */
1119 restart:
1120         switch (mode) {
1121         case SINGLE_EXIT:
1122                 if (TD_IS_SUSPENDED(td2)) {
1123                         wakeup_swapper |= thread_unsuspend_one(td2, p, true);
1124                         thread_lock(td2);
1125                         goto restart;
1126                 }
1127                 if (TD_CAN_ABORT(td2)) {
1128                         wakeup_swapper |= sleepq_abort(td2, EINTR);
1129                         return (wakeup_swapper);
1130                 }
1131                 break;
1132         case SINGLE_BOUNDARY:
1133         case SINGLE_NO_EXIT:
1134                 if (TD_IS_SUSPENDED(td2) &&
1135                     (td2->td_flags & TDF_BOUNDARY) == 0) {
1136                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
1137                         thread_lock(td2);
1138                         goto restart;
1139                 }
1140                 if (TD_CAN_ABORT(td2)) {
1141                         wakeup_swapper |= sleepq_abort(td2, ERESTART);
1142                         return (wakeup_swapper);
1143                 }
1144                 break;
1145         case SINGLE_ALLPROC:
1146                 /*
1147                  * ALLPROC suspend tries to avoid spurious EINTR for
1148                  * threads sleeping interruptable, by suspending the
1149                  * thread directly, similarly to sig_suspend_threads().
1150                  * Since such sleep is not neccessary performed at the user
1151                  * boundary, TDF_ALLPROCSUSP is used to avoid immediate
1152                  * un-suspend.
1153                  */
1154                 if (TD_IS_SUSPENDED(td2) &&
1155                     (td2->td_flags & TDF_ALLPROCSUSP) == 0) {
1156                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
1157                         thread_lock(td2);
1158                         goto restart;
1159                 }
1160                 if (TD_CAN_ABORT(td2)) {
1161                         td2->td_flags |= TDF_ALLPROCSUSP;
1162                         wakeup_swapper |= sleepq_abort(td2, ERESTART);
1163                         return (wakeup_swapper);
1164                 }
1165                 break;
1166         default:
1167                 break;
1168         }
1169         thread_unlock(td2);
1170         return (wakeup_swapper);
1171 }
1172
1173 /*
1174  * Enforce single-threading.
1175  *
1176  * Returns 1 if the caller must abort (another thread is waiting to
1177  * exit the process or similar). Process is locked!
1178  * Returns 0 when you are successfully the only thread running.
1179  * A process has successfully single threaded in the suspend mode when
1180  * There are no threads in user mode. Threads in the kernel must be
1181  * allowed to continue until they get to the user boundary. They may even
1182  * copy out their return values and data before suspending. They may however be
1183  * accelerated in reaching the user boundary as we will wake up
1184  * any sleeping threads that are interruptable. (PCATCH).
1185  */
1186 int
1187 thread_single(struct proc *p, int mode)
1188 {
1189         struct thread *td;
1190         struct thread *td2;
1191         int remaining, wakeup_swapper;
1192
1193         td = curthread;
1194         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1195             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1196             ("invalid mode %d", mode));
1197         /*
1198          * If allowing non-ALLPROC singlethreading for non-curproc
1199          * callers, calc_remaining() and remain_for_mode() should be
1200          * adjusted to also account for td->td_proc != p.  For now
1201          * this is not implemented because it is not used.
1202          */
1203         KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) ||
1204             (mode != SINGLE_ALLPROC && td->td_proc == p),
1205             ("mode %d proc %p curproc %p", mode, p, td->td_proc));
1206         mtx_assert(&Giant, MA_NOTOWNED);
1207         PROC_LOCK_ASSERT(p, MA_OWNED);
1208
1209         /*
1210          * Is someone already single threading?
1211          * Or may be singlethreading is not needed at all.
1212          */
1213         if (mode == SINGLE_ALLPROC) {
1214                 while ((p->p_flag & P_STOPPED_SINGLE) != 0) {
1215                         if ((p->p_flag2 & P2_WEXIT) != 0)
1216                                 return (1);
1217                         msleep(&p->p_flag, &p->p_mtx, PCATCH, "thrsgl", 0);
1218                 }
1219         } else if ((p->p_flag & P_HADTHREADS) == 0)
1220                 return (0);
1221         if (p->p_singlethread != NULL && p->p_singlethread != td)
1222                 return (1);
1223
1224         if (mode == SINGLE_EXIT) {
1225                 p->p_flag |= P_SINGLE_EXIT;
1226                 p->p_flag &= ~P_SINGLE_BOUNDARY;
1227         } else {
1228                 p->p_flag &= ~P_SINGLE_EXIT;
1229                 if (mode == SINGLE_BOUNDARY)
1230                         p->p_flag |= P_SINGLE_BOUNDARY;
1231                 else
1232                         p->p_flag &= ~P_SINGLE_BOUNDARY;
1233         }
1234         if (mode == SINGLE_ALLPROC)
1235                 p->p_flag |= P_TOTAL_STOP;
1236         p->p_flag |= P_STOPPED_SINGLE;
1237         PROC_SLOCK(p);
1238         p->p_singlethread = td;
1239         remaining = calc_remaining(p, mode);
1240         while (remaining != remain_for_mode(mode)) {
1241                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
1242                         goto stopme;
1243                 wakeup_swapper = 0;
1244                 FOREACH_THREAD_IN_PROC(p, td2) {
1245                         if (td2 == td)
1246                                 continue;
1247                         thread_lock(td2);
1248                         ast_sched_locked(td2, TDA_SUSPEND);
1249                         if (TD_IS_INHIBITED(td2)) {
1250                                 wakeup_swapper |= weed_inhib(mode, td2, p);
1251 #ifdef SMP
1252                         } else if (TD_IS_RUNNING(td2)) {
1253                                 forward_signal(td2);
1254                                 thread_unlock(td2);
1255 #endif
1256                         } else
1257                                 thread_unlock(td2);
1258                 }
1259                 if (wakeup_swapper)
1260                         kick_proc0();
1261                 remaining = calc_remaining(p, mode);
1262
1263                 /*
1264                  * Maybe we suspended some threads.. was it enough?
1265                  */
1266                 if (remaining == remain_for_mode(mode))
1267                         break;
1268
1269 stopme:
1270                 /*
1271                  * Wake us up when everyone else has suspended.
1272                  * In the mean time we suspend as well.
1273                  */
1274                 thread_suspend_switch(td, p);
1275                 remaining = calc_remaining(p, mode);
1276         }
1277         if (mode == SINGLE_EXIT) {
1278                 /*
1279                  * Convert the process to an unthreaded process.  The
1280                  * SINGLE_EXIT is called by exit1() or execve(), in
1281                  * both cases other threads must be retired.
1282                  */
1283                 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads"));
1284                 p->p_singlethread = NULL;
1285                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS);
1286
1287                 /*
1288                  * Wait for any remaining threads to exit cpu_throw().
1289                  */
1290                 while (p->p_exitthreads != 0) {
1291                         PROC_SUNLOCK(p);
1292                         PROC_UNLOCK(p);
1293                         sched_relinquish(td);
1294                         PROC_LOCK(p);
1295                         PROC_SLOCK(p);
1296                 }
1297         } else if (mode == SINGLE_BOUNDARY) {
1298                 /*
1299                  * Wait until all suspended threads are removed from
1300                  * the processors.  The thread_suspend_check()
1301                  * increments p_boundary_count while it is still
1302                  * running, which makes it possible for the execve()
1303                  * to destroy vmspace while our other threads are
1304                  * still using the address space.
1305                  *
1306                  * We lock the thread, which is only allowed to
1307                  * succeed after context switch code finished using
1308                  * the address space.
1309                  */
1310                 FOREACH_THREAD_IN_PROC(p, td2) {
1311                         if (td2 == td)
1312                                 continue;
1313                         thread_lock(td2);
1314                         KASSERT((td2->td_flags & TDF_BOUNDARY) != 0,
1315                             ("td %p not on boundary", td2));
1316                         KASSERT(TD_IS_SUSPENDED(td2),
1317                             ("td %p is not suspended", td2));
1318                         thread_unlock(td2);
1319                 }
1320         }
1321         PROC_SUNLOCK(p);
1322         return (0);
1323 }
1324
1325 bool
1326 thread_suspend_check_needed(void)
1327 {
1328         struct proc *p;
1329         struct thread *td;
1330
1331         td = curthread;
1332         p = td->td_proc;
1333         PROC_LOCK_ASSERT(p, MA_OWNED);
1334         return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 &&
1335             (td->td_dbgflags & TDB_SUSPEND) != 0));
1336 }
1337
1338 /*
1339  * Called in from locations that can safely check to see
1340  * whether we have to suspend or at least throttle for a
1341  * single-thread event (e.g. fork).
1342  *
1343  * Such locations include userret().
1344  * If the "return_instead" argument is non zero, the thread must be able to
1345  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
1346  *
1347  * The 'return_instead' argument tells the function if it may do a
1348  * thread_exit() or suspend, or whether the caller must abort and back
1349  * out instead.
1350  *
1351  * If the thread that set the single_threading request has set the
1352  * P_SINGLE_EXIT bit in the process flags then this call will never return
1353  * if 'return_instead' is false, but will exit.
1354  *
1355  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
1356  *---------------+--------------------+---------------------
1357  *       0       | returns 0          |   returns 0 or 1
1358  *               | when ST ends       |   immediately
1359  *---------------+--------------------+---------------------
1360  *       1       | thread exits       |   returns 1
1361  *               |                    |  immediately
1362  * 0 = thread_exit() or suspension ok,
1363  * other = return error instead of stopping the thread.
1364  *
1365  * While a full suspension is under effect, even a single threading
1366  * thread would be suspended if it made this call (but it shouldn't).
1367  * This call should only be made from places where
1368  * thread_exit() would be safe as that may be the outcome unless
1369  * return_instead is set.
1370  */
1371 int
1372 thread_suspend_check(int return_instead)
1373 {
1374         struct thread *td;
1375         struct proc *p;
1376         int wakeup_swapper;
1377
1378         td = curthread;
1379         p = td->td_proc;
1380         mtx_assert(&Giant, MA_NOTOWNED);
1381         PROC_LOCK_ASSERT(p, MA_OWNED);
1382         while (thread_suspend_check_needed()) {
1383                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1384                         KASSERT(p->p_singlethread != NULL,
1385                             ("singlethread not set"));
1386                         /*
1387                          * The only suspension in action is a
1388                          * single-threading. Single threader need not stop.
1389                          * It is safe to access p->p_singlethread unlocked
1390                          * because it can only be set to our address by us.
1391                          */
1392                         if (p->p_singlethread == td)
1393                                 return (0);     /* Exempt from stopping. */
1394                 }
1395                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
1396                         return (EINTR);
1397
1398                 /* Should we goto user boundary if we didn't come from there? */
1399                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1400                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
1401                         return (ERESTART);
1402
1403                 /*
1404                  * Ignore suspend requests if they are deferred.
1405                  */
1406                 if ((td->td_flags & TDF_SBDRY) != 0) {
1407                         KASSERT(return_instead,
1408                             ("TDF_SBDRY set for unsafe thread_suspend_check"));
1409                         KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) !=
1410                             (TDF_SEINTR | TDF_SERESTART),
1411                             ("both TDF_SEINTR and TDF_SERESTART"));
1412                         return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0);
1413                 }
1414
1415                 /*
1416                  * If the process is waiting for us to exit,
1417                  * this thread should just suicide.
1418                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
1419                  */
1420                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
1421                         PROC_UNLOCK(p);
1422
1423                         /*
1424                          * Allow Linux emulation layer to do some work
1425                          * before thread suicide.
1426                          */
1427                         if (__predict_false(p->p_sysent->sv_thread_detach != NULL))
1428                                 (p->p_sysent->sv_thread_detach)(td);
1429                         umtx_thread_exit(td);
1430                         kern_thr_exit(td);
1431                         panic("stopped thread did not exit");
1432                 }
1433
1434                 PROC_SLOCK(p);
1435                 thread_stopped(p);
1436                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1437                         if (p->p_numthreads == p->p_suspcount + 1) {
1438                                 thread_lock(p->p_singlethread);
1439                                 wakeup_swapper = thread_unsuspend_one(
1440                                     p->p_singlethread, p, false);
1441                                 if (wakeup_swapper)
1442                                         kick_proc0();
1443                         }
1444                 }
1445                 PROC_UNLOCK(p);
1446                 thread_lock(td);
1447                 /*
1448                  * When a thread suspends, it just
1449                  * gets taken off all queues.
1450                  */
1451                 thread_suspend_one(td);
1452                 if (return_instead == 0) {
1453                         p->p_boundary_count++;
1454                         td->td_flags |= TDF_BOUNDARY;
1455                 }
1456                 PROC_SUNLOCK(p);
1457                 mi_switch(SW_INVOL | SWT_SUSPEND);
1458                 PROC_LOCK(p);
1459         }
1460         return (0);
1461 }
1462
1463 /*
1464  * Check for possible stops and suspensions while executing a
1465  * casueword or similar transiently failing operation.
1466  *
1467  * The sleep argument controls whether the function can handle a stop
1468  * request itself or it should return ERESTART and the request is
1469  * proceed at the kernel/user boundary in ast.
1470  *
1471  * Typically, when retrying due to casueword(9) failure (rv == 1), we
1472  * should handle the stop requests there, with exception of cases when
1473  * the thread owns a kernel resource, for instance busied the umtx
1474  * key, or when functions return immediately if thread_check_susp()
1475  * returned non-zero.  On the other hand, retrying the whole lock
1476  * operation, we better not stop there but delegate the handling to
1477  * ast.
1478  *
1479  * If the request is for thread termination P_SINGLE_EXIT, we cannot
1480  * handle it at all, and simply return EINTR.
1481  */
1482 int
1483 thread_check_susp(struct thread *td, bool sleep)
1484 {
1485         struct proc *p;
1486         int error;
1487
1488         /*
1489          * The check for TDA_SUSPEND is racy, but it is enough to
1490          * eventually break the lockstep loop.
1491          */
1492         if (!td_ast_pending(td, TDA_SUSPEND))
1493                 return (0);
1494         error = 0;
1495         p = td->td_proc;
1496         PROC_LOCK(p);
1497         if (p->p_flag & P_SINGLE_EXIT)
1498                 error = EINTR;
1499         else if (P_SHOULDSTOP(p) ||
1500             ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND)))
1501                 error = sleep ? thread_suspend_check(0) : ERESTART;
1502         PROC_UNLOCK(p);
1503         return (error);
1504 }
1505
1506 void
1507 thread_suspend_switch(struct thread *td, struct proc *p)
1508 {
1509
1510         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1511         PROC_LOCK_ASSERT(p, MA_OWNED);
1512         PROC_SLOCK_ASSERT(p, MA_OWNED);
1513         /*
1514          * We implement thread_suspend_one in stages here to avoid
1515          * dropping the proc lock while the thread lock is owned.
1516          */
1517         if (p == td->td_proc) {
1518                 thread_stopped(p);
1519                 p->p_suspcount++;
1520         }
1521         PROC_UNLOCK(p);
1522         thread_lock(td);
1523         ast_unsched_locked(td, TDA_SUSPEND);
1524         TD_SET_SUSPENDED(td);
1525         sched_sleep(td, 0);
1526         PROC_SUNLOCK(p);
1527         DROP_GIANT();
1528         mi_switch(SW_VOL | SWT_SUSPEND);
1529         PICKUP_GIANT();
1530         PROC_LOCK(p);
1531         PROC_SLOCK(p);
1532 }
1533
1534 void
1535 thread_suspend_one(struct thread *td)
1536 {
1537         struct proc *p;
1538
1539         p = td->td_proc;
1540         PROC_SLOCK_ASSERT(p, MA_OWNED);
1541         THREAD_LOCK_ASSERT(td, MA_OWNED);
1542         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1543         p->p_suspcount++;
1544         ast_unsched_locked(td, TDA_SUSPEND);
1545         TD_SET_SUSPENDED(td);
1546         sched_sleep(td, 0);
1547 }
1548
1549 static int
1550 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary)
1551 {
1552
1553         THREAD_LOCK_ASSERT(td, MA_OWNED);
1554         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
1555         TD_CLR_SUSPENDED(td);
1556         td->td_flags &= ~TDF_ALLPROCSUSP;
1557         if (td->td_proc == p) {
1558                 PROC_SLOCK_ASSERT(p, MA_OWNED);
1559                 p->p_suspcount--;
1560                 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) {
1561                         td->td_flags &= ~TDF_BOUNDARY;
1562                         p->p_boundary_count--;
1563                 }
1564         }
1565         return (setrunnable(td, 0));
1566 }
1567
1568 void
1569 thread_run_flash(struct thread *td)
1570 {
1571         struct proc *p;
1572
1573         p = td->td_proc;
1574         PROC_LOCK_ASSERT(p, MA_OWNED);
1575
1576         if (TD_ON_SLEEPQ(td))
1577                 sleepq_remove_nested(td);
1578         else
1579                 thread_lock(td);
1580
1581         THREAD_LOCK_ASSERT(td, MA_OWNED);
1582         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
1583
1584         TD_CLR_SUSPENDED(td);
1585         PROC_SLOCK(p);
1586         MPASS(p->p_suspcount > 0);
1587         p->p_suspcount--;
1588         PROC_SUNLOCK(p);
1589         if (setrunnable(td, 0))
1590                 kick_proc0();
1591 }
1592
1593 /*
1594  * Allow all threads blocked by single threading to continue running.
1595  */
1596 void
1597 thread_unsuspend(struct proc *p)
1598 {
1599         struct thread *td;
1600         int wakeup_swapper;
1601
1602         PROC_LOCK_ASSERT(p, MA_OWNED);
1603         PROC_SLOCK_ASSERT(p, MA_OWNED);
1604         wakeup_swapper = 0;
1605         if (!P_SHOULDSTOP(p)) {
1606                 FOREACH_THREAD_IN_PROC(p, td) {
1607                         thread_lock(td);
1608                         if (TD_IS_SUSPENDED(td))
1609                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1610                                     true);
1611                         else
1612                                 thread_unlock(td);
1613                 }
1614         } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1615             p->p_numthreads == p->p_suspcount) {
1616                 /*
1617                  * Stopping everything also did the job for the single
1618                  * threading request. Now we've downgraded to single-threaded,
1619                  * let it continue.
1620                  */
1621                 if (p->p_singlethread->td_proc == p) {
1622                         thread_lock(p->p_singlethread);
1623                         wakeup_swapper = thread_unsuspend_one(
1624                             p->p_singlethread, p, false);
1625                 }
1626         }
1627         if (wakeup_swapper)
1628                 kick_proc0();
1629 }
1630
1631 /*
1632  * End the single threading mode..
1633  */
1634 void
1635 thread_single_end(struct proc *p, int mode)
1636 {
1637         struct thread *td;
1638         int wakeup_swapper;
1639
1640         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1641             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1642             ("invalid mode %d", mode));
1643         PROC_LOCK_ASSERT(p, MA_OWNED);
1644         KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) ||
1645             (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0),
1646             ("mode %d does not match P_TOTAL_STOP", mode));
1647         KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread,
1648             ("thread_single_end from other thread %p %p",
1649             curthread, p->p_singlethread));
1650         KASSERT(mode != SINGLE_BOUNDARY ||
1651             (p->p_flag & P_SINGLE_BOUNDARY) != 0,
1652             ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag));
1653         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY |
1654             P_TOTAL_STOP);
1655         PROC_SLOCK(p);
1656         p->p_singlethread = NULL;
1657         wakeup_swapper = 0;
1658         /*
1659          * If there are other threads they may now run,
1660          * unless of course there is a blanket 'stop order'
1661          * on the process. The single threader must be allowed
1662          * to continue however as this is a bad place to stop.
1663          */
1664         if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) {
1665                 FOREACH_THREAD_IN_PROC(p, td) {
1666                         thread_lock(td);
1667                         if (TD_IS_SUSPENDED(td)) {
1668                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1669                                     true);
1670                         } else
1671                                 thread_unlock(td);
1672                 }
1673         }
1674         KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0,
1675             ("inconsistent boundary count %d", p->p_boundary_count));
1676         PROC_SUNLOCK(p);
1677         if (wakeup_swapper)
1678                 kick_proc0();
1679         wakeup(&p->p_flag);
1680 }
1681
1682 /*
1683  * Locate a thread by number and return with proc lock held.
1684  *
1685  * thread exit establishes proc -> tidhash lock ordering, but lookup
1686  * takes tidhash first and needs to return locked proc.
1687  *
1688  * The problem is worked around by relying on type-safety of both
1689  * structures and doing the work in 2 steps:
1690  * - tidhash-locked lookup which saves both thread and proc pointers
1691  * - proc-locked verification that the found thread still matches
1692  */
1693 static bool
1694 tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp)
1695 {
1696 #define RUN_THRESH      16
1697         struct proc *p;
1698         struct thread *td;
1699         int run;
1700         bool locked;
1701
1702         run = 0;
1703         rw_rlock(TIDHASHLOCK(tid));
1704         locked = true;
1705         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
1706                 if (td->td_tid != tid) {
1707                         run++;
1708                         continue;
1709                 }
1710                 p = td->td_proc;
1711                 if (pid != -1 && p->p_pid != pid) {
1712                         td = NULL;
1713                         break;
1714                 }
1715                 if (run > RUN_THRESH) {
1716                         if (rw_try_upgrade(TIDHASHLOCK(tid))) {
1717                                 LIST_REMOVE(td, td_hash);
1718                                 LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1719                                         td, td_hash);
1720                                 rw_wunlock(TIDHASHLOCK(tid));
1721                                 locked = false;
1722                                 break;
1723                         }
1724                 }
1725                 break;
1726         }
1727         if (locked)
1728                 rw_runlock(TIDHASHLOCK(tid));
1729         if (td == NULL)
1730                 return (false);
1731         *pp = p;
1732         *tdp = td;
1733         return (true);
1734 }
1735
1736 struct thread *
1737 tdfind(lwpid_t tid, pid_t pid)
1738 {
1739         struct proc *p;
1740         struct thread *td;
1741
1742         td = curthread;
1743         if (td->td_tid == tid) {
1744                 if (pid != -1 && td->td_proc->p_pid != pid)
1745                         return (NULL);
1746                 PROC_LOCK(td->td_proc);
1747                 return (td);
1748         }
1749
1750         for (;;) {
1751                 if (!tdfind_hash(tid, pid, &p, &td))
1752                         return (NULL);
1753                 PROC_LOCK(p);
1754                 if (td->td_tid != tid) {
1755                         PROC_UNLOCK(p);
1756                         continue;
1757                 }
1758                 if (td->td_proc != p) {
1759                         PROC_UNLOCK(p);
1760                         continue;
1761                 }
1762                 if (p->p_state == PRS_NEW) {
1763                         PROC_UNLOCK(p);
1764                         return (NULL);
1765                 }
1766                 return (td);
1767         }
1768 }
1769
1770 void
1771 tidhash_add(struct thread *td)
1772 {
1773         rw_wlock(TIDHASHLOCK(td->td_tid));
1774         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1775         rw_wunlock(TIDHASHLOCK(td->td_tid));
1776 }
1777
1778 void
1779 tidhash_remove(struct thread *td)
1780 {
1781
1782         rw_wlock(TIDHASHLOCK(td->td_tid));
1783         LIST_REMOVE(td, td_hash);
1784         rw_wunlock(TIDHASHLOCK(td->td_tid));
1785 }