sys/kern/kern_thread.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   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/mutex.h>
  42 #include <sys/proc.h>
  43 #include <sys/bitstring.h>
  44 #include <sys/epoch.h>
  45 #include <sys/rangelock.h>
  46 #include <sys/resourcevar.h>
  47 #include <sys/sdt.h>
  48 #include <sys/smp.h>
  49 #include <sys/sched.h>
  50 #include <sys/sleepqueue.h>
  51 #include <sys/selinfo.h>
  52 #include <sys/syscallsubr.h>
  53 #include <sys/dtrace_bsd.h>
  54 #include <sys/sysent.h>
  55 #include <sys/turnstile.h>
  56 #include <sys/taskqueue.h>
  57 #include <sys/ktr.h>
  58 #include <sys/rwlock.h>
  59 #include <sys/umtx.h>
  60 #include <sys/vmmeter.h>
  61 #include <sys/cpuset.h>
  62 #ifdef  HWPMC_HOOKS
  63 #include <sys/pmckern.h>
  64 #endif
  65 #include <sys/priv.h>
  66
  67 #include <security/audit/audit.h>
  68
  69 #include <vm/pmap.h>
  70 #include <vm/vm.h>
  71 #include <vm/vm_extern.h>
  72 #include <vm/uma.h>
  73 #include <vm/vm_phys.h>
  74 #include <sys/eventhandler.h>
  75
  76 /*
  77  * Asserts below verify the stability of struct thread and struct proc
  78  * layout, as exposed by KBI to modules.  On head, the KBI is allowed
  79  * to drift, change to the structures must be accompanied by the
  80  * assert update.
  81  *
  82  * On the stable branches after KBI freeze, conditions must not be
  83  * violated.  Typically new fields are moved to the end of the
  84  * structures.
  85  */
  86 #ifdef __amd64__
  87 _Static_assert(offsetof(struct thread, td_flags) == 0xfc,
  88     "struct thread KBI td_flags");
  89 _Static_assert(offsetof(struct thread, td_pflags) == 0x104,
  90     "struct thread KBI td_pflags");
  91 _Static_assert(offsetof(struct thread, td_frame) == 0x4a0,
  92     "struct thread KBI td_frame");
  93 _Static_assert(offsetof(struct thread, td_emuldata) == 0x6b0,
  94     "struct thread KBI td_emuldata");
  95 _Static_assert(offsetof(struct proc, p_flag) == 0xb8,
  96     "struct proc KBI p_flag");
  97 _Static_assert(offsetof(struct proc, p_pid) == 0xc4,
  98     "struct proc KBI p_pid");
  99 _Static_assert(offsetof(struct proc, p_filemon) == 0x3c0,
 100     "struct proc KBI p_filemon");
 101 _Static_assert(offsetof(struct proc, p_comm) == 0x3d8,
 102     "struct proc KBI p_comm");
 103 _Static_assert(offsetof(struct proc, p_emuldata) == 0x4b8,
 104     "struct proc KBI p_emuldata");
 105 #endif
 106 #ifdef __i386__
 107 _Static_assert(offsetof(struct thread, td_flags) == 0x98,
 108     "struct thread KBI td_flags");
 109 _Static_assert(offsetof(struct thread, td_pflags) == 0xa0,
 110     "struct thread KBI td_pflags");
 111 _Static_assert(offsetof(struct thread, td_frame) == 0x300,
 112     "struct thread KBI td_frame");
 113 _Static_assert(offsetof(struct thread, td_emuldata) == 0x344,
 114     "struct thread KBI td_emuldata");
 115 _Static_assert(offsetof(struct proc, p_flag) == 0x6c,
 116     "struct proc KBI p_flag");
 117 _Static_assert(offsetof(struct proc, p_pid) == 0x78,
 118     "struct proc KBI p_pid");
 119 _Static_assert(offsetof(struct proc, p_filemon) == 0x26c,
 120     "struct proc KBI p_filemon");
 121 _Static_assert(offsetof(struct proc, p_comm) == 0x280,
 122     "struct proc KBI p_comm");
 123 _Static_assert(offsetof(struct proc, p_emuldata) == 0x30c,
 124     "struct proc KBI p_emuldata");
 125 #endif
 126
 127 SDT_PROVIDER_DECLARE(proc);
 128 SDT_PROBE_DEFINE(proc, , , lwp__exit);
 129
 130 /*
 131  * thread related storage.
 132  */
 133 static uma_zone_t thread_zone;
 134
 135 struct thread_domain_data {
 136         struct thread   *tdd_zombies;
 137         int             tdd_reapticks;
 138 } __aligned(CACHE_LINE_SIZE);
 139
 140 static struct thread_domain_data thread_domain_data[MAXMEMDOM];
 141
 142 static struct task      thread_reap_task;
 143 static struct callout   thread_reap_callout;
 144
 145 static void thread_zombie(struct thread *);
 146 static void thread_reap(void);
 147 static void thread_reap_all(void);
 148 static void thread_reap_task_cb(void *, int);
 149 static void thread_reap_callout_cb(void *);
 150 static int thread_unsuspend_one(struct thread *td, struct proc *p,
 151     bool boundary);
 152 static void thread_free_batched(struct thread *td);
 153
 154 static __exclusive_cache_line struct mtx tid_lock;
 155 static bitstr_t *tid_bitmap;
 156
 157 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
 158
 159 static int maxthread;
 160 SYSCTL_INT(_kern, OID_AUTO, maxthread, CTLFLAG_RDTUN,
 161     &maxthread, 0, "Maximum number of threads");
 162
 163 static __exclusive_cache_line int nthreads;
 164
 165 static LIST_HEAD(tidhashhead, thread) *tidhashtbl;
 166 static u_long   tidhash;
 167 static u_long   tidhashlock;
 168 static struct   rwlock *tidhashtbl_lock;
 169 #define TIDHASH(tid)            (&tidhashtbl[(tid) & tidhash])
 170 #define TIDHASHLOCK(tid)        (&tidhashtbl_lock[(tid) & tidhashlock])
 171
 172 EVENTHANDLER_LIST_DEFINE(thread_ctor);
 173 EVENTHANDLER_LIST_DEFINE(thread_dtor);
 174 EVENTHANDLER_LIST_DEFINE(thread_init);
 175 EVENTHANDLER_LIST_DEFINE(thread_fini);
 176
 177 static bool
 178 thread_count_inc_try(void)
 179 {
 180         int nthreads_new;
 181
 182         nthreads_new = atomic_fetchadd_int(&nthreads, 1) + 1;
 183         if (nthreads_new >= maxthread - 100) {
 184                 if (priv_check_cred(curthread->td_ucred, PRIV_MAXPROC) != 0 ||
 185                     nthreads_new >= maxthread) {
 186                         atomic_subtract_int(&nthreads, 1);
 187                         return (false);
 188                 }
 189         }
 190         return (true);
 191 }
 192
 193 static bool
 194 thread_count_inc(void)
 195 {
 196         static struct timeval lastfail;
 197         static int curfail;
 198
 199         thread_reap();
 200         if (thread_count_inc_try()) {
 201                 return (true);
 202         }
 203
 204         thread_reap_all();
 205         if (thread_count_inc_try()) {
 206                 return (true);
 207         }
 208
 209         if (ppsratecheck(&lastfail, &curfail, 1)) {
 210                 printf("maxthread limit exceeded by uid %u "
 211                     "(pid %d); consider increasing kern.maxthread\n",
 212                     curthread->td_ucred->cr_ruid, curproc->p_pid);
 213         }
 214         return (false);
 215 }
 216
 217 static void
 218 thread_count_sub(int n)
 219 {
 220
 221         atomic_subtract_int(&nthreads, n);
 222 }
 223
 224 static void
 225 thread_count_dec(void)
 226 {
 227
 228         thread_count_sub(1);
 229 }
 230
 231 static lwpid_t
 232 tid_alloc(void)
 233 {
 234         static lwpid_t trytid;
 235         lwpid_t tid;
 236
 237         mtx_lock(&tid_lock);
 238         /*
 239          * It is an invariant that the bitmap is big enough to hold maxthread
 240          * IDs. If we got to this point there has to be at least one free.
 241          */
 242         if (trytid >= maxthread)
 243                 trytid = 0;
 244         bit_ffc_at(tid_bitmap, trytid, maxthread, &tid);
 245         if (tid == -1) {
 246                 KASSERT(trytid != 0, ("unexpectedly ran out of IDs"));
 247                 trytid = 0;
 248                 bit_ffc_at(tid_bitmap, trytid, maxthread, &tid);
 249                 KASSERT(tid != -1, ("unexpectedly ran out of IDs"));
 250         }
 251         bit_set(tid_bitmap, tid);
 252         trytid = tid + 1;
 253         mtx_unlock(&tid_lock);
 254         return (tid + NO_PID);
 255 }
 256
 257 static void
 258 tid_free_locked(lwpid_t rtid)
 259 {
 260         lwpid_t tid;
 261
 262         mtx_assert(&tid_lock, MA_OWNED);
 263         KASSERT(rtid >= NO_PID,
 264             ("%s: invalid tid %d\n", __func__, rtid));
 265         tid = rtid - NO_PID;
 266         KASSERT(bit_test(tid_bitmap, tid) != 0,
 267             ("thread ID %d not allocated\n", rtid));
 268         bit_clear(tid_bitmap, tid);
 269 }
 270
 271 static void
 272 tid_free(lwpid_t rtid)
 273 {
 274
 275         mtx_lock(&tid_lock);
 276         tid_free_locked(rtid);
 277         mtx_unlock(&tid_lock);
 278 }
 279
 280 static void
 281 tid_free_batch(lwpid_t *batch, int n)
 282 {
 283         int i;
 284
 285         mtx_lock(&tid_lock);
 286         for (i = 0; i < n; i++) {
 287                 tid_free_locked(batch[i]);
 288         }
 289         mtx_unlock(&tid_lock);
 290 }
 291
 292 /*
 293  * Batching for thread reapping.
 294  */
 295 struct tidbatch {
 296         lwpid_t tab[16];
 297         int n;
 298 };
 299
 300 static void
 301 tidbatch_prep(struct tidbatch *tb)
 302 {
 303
 304         tb->n = 0;
 305 }
 306
 307 static void
 308 tidbatch_add(struct tidbatch *tb, struct thread *td)
 309 {
 310
 311         KASSERT(tb->n < nitems(tb->tab),
 312             ("%s: count too high %d", __func__, tb->n));
 313         tb->tab[tb->n] = td->td_tid;
 314         tb->n++;
 315 }
 316
 317 static void
 318 tidbatch_process(struct tidbatch *tb)
 319 {
 320
 321         KASSERT(tb->n <= nitems(tb->tab),
 322             ("%s: count too high %d", __func__, tb->n));
 323         if (tb->n == nitems(tb->tab)) {
 324                 tid_free_batch(tb->tab, tb->n);
 325                 tb->n = 0;
 326         }
 327 }
 328
 329 static void
 330 tidbatch_final(struct tidbatch *tb)
 331 {
 332
 333         KASSERT(tb->n <= nitems(tb->tab),
 334             ("%s: count too high %d", __func__, tb->n));
 335         if (tb->n != 0) {
 336                 tid_free_batch(tb->tab, tb->n);
 337         }
 338 }
 339
 340 /*
 341  * Prepare a thread for use.
 342  */
 343 static int
 344 thread_ctor(void *mem, int size, void *arg, int flags)
 345 {
 346         struct thread   *td;
 347
 348         td = (struct thread *)mem;
 349         td->td_state = TDS_INACTIVE;
 350         td->td_lastcpu = td->td_oncpu = NOCPU;
 351
 352         /*
 353          * Note that td_critnest begins life as 1 because the thread is not
 354          * running and is thereby implicitly waiting to be on the receiving
 355          * end of a context switch.
 356          */
 357         td->td_critnest = 1;
 358         td->td_lend_user_pri = PRI_MAX;
 359 #ifdef AUDIT
 360         audit_thread_alloc(td);
 361 #endif
 362 #ifdef KDTRACE_HOOKS
 363         kdtrace_thread_ctor(td);
 364 #endif
 365         umtx_thread_alloc(td);
 366         MPASS(td->td_sel == NULL);
 367         return (0);
 368 }
 369
 370 /*
 371  * Reclaim a thread after use.
 372  */
 373 static void
 374 thread_dtor(void *mem, int size, void *arg)
 375 {
 376         struct thread *td;
 377
 378         td = (struct thread *)mem;
 379
 380 #ifdef INVARIANTS
 381         /* Verify that this thread is in a safe state to free. */
 382         switch (td->td_state) {
 383         case TDS_INHIBITED:
 384         case TDS_RUNNING:
 385         case TDS_CAN_RUN:
 386         case TDS_RUNQ:
 387                 /*
 388                  * We must never unlink a thread that is in one of
 389                  * these states, because it is currently active.
 390                  */
 391                 panic("bad state for thread unlinking");
 392                 /* NOTREACHED */
 393         case TDS_INACTIVE:
 394                 break;
 395         default:
 396                 panic("bad thread state");
 397                 /* NOTREACHED */
 398         }
 399 #endif
 400 #ifdef AUDIT
 401         audit_thread_free(td);
 402 #endif
 403 #ifdef KDTRACE_HOOKS
 404         kdtrace_thread_dtor(td);
 405 #endif
 406         /* Free all OSD associated to this thread. */
 407         osd_thread_exit(td);
 408         td_softdep_cleanup(td);
 409         MPASS(td->td_su == NULL);
 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(1);
 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 extern int max_threads_per_proc;
 482
 483 /*
 484  * Initialize global thread allocation resources.
 485  */
 486 void
 487 threadinit(void)
 488 {
 489         u_long i;
 490         lwpid_t tid0;
 491         uint32_t flags;
 492
 493         /*
 494          * Place an upper limit on threads which can be allocated.
 495          *
 496          * Note that other factors may make the de facto limit much lower.
 497          *
 498          * Platform limits are somewhat arbitrary but deemed "more than good
 499          * enough" for the foreseable future.
 500          */
 501         if (maxthread == 0) {
 502 #ifdef _LP64
 503                 maxthread = MIN(maxproc * max_threads_per_proc, 1000000);
 504 #else
 505                 maxthread = MIN(maxproc * max_threads_per_proc, 100000);
 506 #endif
 507         }
 508
 509         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
 510         tid_bitmap = bit_alloc(maxthread, M_TIDHASH, M_WAITOK);
 511         /*
 512          * Handle thread0.
 513          */
 514         thread_count_inc();
 515         tid0 = tid_alloc();
 516         if (tid0 != THREAD0_TID)
 517                 panic("tid0 %d != %d\n", tid0, THREAD0_TID);
 518
 519         flags = UMA_ZONE_NOFREE;
 520 #ifdef __aarch64__
 521         /*
 522          * Force thread structures to be allocated from the direct map.
 523          * Otherwise, superpage promotions and demotions may temporarily
 524          * invalidate thread structure mappings.  For most dynamically allocated
 525          * structures this is not a problem, but translation faults cannot be
 526          * handled without accessing curthread.
 527          */
 528         flags |= UMA_ZONE_CONTIG;
 529 #endif
 530         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
 531             thread_ctor, thread_dtor, thread_init, thread_fini,
 532             32 - 1, flags);
 533         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
 534         tidhashlock = (tidhash + 1) / 64;
 535         if (tidhashlock > 0)
 536                 tidhashlock--;
 537         tidhashtbl_lock = malloc(sizeof(*tidhashtbl_lock) * (tidhashlock + 1),
 538             M_TIDHASH, M_WAITOK | M_ZERO);
 539         for (i = 0; i < tidhashlock + 1; i++)
 540                 rw_init(&tidhashtbl_lock[i], "tidhash");
 541
 542         TASK_INIT(&thread_reap_task, 0, thread_reap_task_cb, NULL);
 543         callout_init(&thread_reap_callout, 1);
 544         callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL);
 545 }
 546
 547 /*
 548  * Place an unused thread on the zombie list.
 549  */
 550 void
 551 thread_zombie(struct thread *td)
 552 {
 553         struct thread_domain_data *tdd;
 554         struct thread *ztd;
 555
 556         tdd = &thread_domain_data[td->td_allocdomain];
 557         ztd = atomic_load_ptr(&tdd->tdd_zombies);
 558         for (;;) {
 559                 td->td_zombie = ztd;
 560                 if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies,
 561                     (uintptr_t *)&ztd, (uintptr_t)td))
 562                         break;
 563                 continue;
 564         }
 565 }
 566
 567 /*
 568  * Release a thread that has exited after cpu_throw().
 569  */
 570 void
 571 thread_stash(struct thread *td)
 572 {
 573         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
 574         thread_zombie(td);
 575 }
 576
 577 /*
 578  * Reap zombies from passed domain.
 579  */
 580 static void
 581 thread_reap_domain(struct thread_domain_data *tdd)
 582 {
 583         struct thread *itd, *ntd;
 584         struct tidbatch tidbatch;
 585         struct credbatch credbatch;
 586         int tdcount;
 587         struct plimit *lim;
 588         int limcount;
 589
 590         /*
 591          * Reading upfront is pessimal if followed by concurrent atomic_swap,
 592          * but most of the time the list is empty.
 593          */
 594         if (tdd->tdd_zombies == NULL)
 595                 return;
 596
 597         itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies,
 598             (uintptr_t)NULL);
 599         if (itd == NULL)
 600                 return;
 601
 602         /*
 603          * Multiple CPUs can get here, the race is fine as ticks is only
 604          * advisory.
 605          */
 606         tdd->tdd_reapticks = ticks;
 607
 608         tidbatch_prep(&tidbatch);
 609         credbatch_prep(&credbatch);
 610         tdcount = 0;
 611         lim = NULL;
 612         limcount = 0;
 613
 614         while (itd != NULL) {
 615                 ntd = itd->td_zombie;
 616                 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd);
 617                 tidbatch_add(&tidbatch, itd);
 618                 credbatch_add(&credbatch, itd);
 619                 MPASS(itd->td_limit != NULL);
 620                 if (lim != itd->td_limit) {
 621                         if (limcount != 0) {
 622                                 lim_freen(lim, limcount);
 623                                 limcount = 0;
 624                         }
 625                 }
 626                 lim = itd->td_limit;
 627                 limcount++;
 628                 thread_free_batched(itd);
 629                 tidbatch_process(&tidbatch);
 630                 credbatch_process(&credbatch);
 631                 tdcount++;
 632                 if (tdcount == 32) {
 633                         thread_count_sub(tdcount);
 634                         tdcount = 0;
 635                 }
 636                 itd = ntd;
 637         }
 638
 639         tidbatch_final(&tidbatch);
 640         credbatch_final(&credbatch);
 641         if (tdcount != 0) {
 642                 thread_count_sub(tdcount);
 643         }
 644         MPASS(limcount != 0);
 645         lim_freen(lim, limcount);
 646 }
 647
 648 /*
 649  * Reap zombies from all domains.
 650  */
 651 static void
 652 thread_reap_all(void)
 653 {
 654         struct thread_domain_data *tdd;
 655         int i, domain;
 656
 657         domain = PCPU_GET(domain);
 658         for (i = 0; i < vm_ndomains; i++) {
 659                 tdd = &thread_domain_data[(i + domain) % vm_ndomains];
 660                 thread_reap_domain(tdd);
 661         }
 662 }
 663
 664 /*
 665  * Reap zombies from local domain.
 666  */
 667 static void
 668 thread_reap(void)
 669 {
 670         struct thread_domain_data *tdd;
 671         int domain;
 672
 673         domain = PCPU_GET(domain);
 674         tdd = &thread_domain_data[domain];
 675
 676         thread_reap_domain(tdd);
 677 }
 678
 679 static void
 680 thread_reap_task_cb(void *arg __unused, int pending __unused)
 681 {
 682
 683         thread_reap_all();
 684 }
 685
 686 static void
 687 thread_reap_callout_cb(void *arg __unused)
 688 {
 689         struct thread_domain_data *tdd;
 690         int i, cticks, lticks;
 691         bool wantreap;
 692
 693         wantreap = false;
 694         cticks = atomic_load_int(&ticks);
 695         for (i = 0; i < vm_ndomains; i++) {
 696                 tdd = &thread_domain_data[i];
 697                 lticks = tdd->tdd_reapticks;
 698                 if (tdd->tdd_zombies != NULL &&
 699                     (u_int)(cticks - lticks) > 5 * hz) {
 700                         wantreap = true;
 701                         break;
 702                 }
 703         }
 704
 705         if (wantreap)
 706                 taskqueue_enqueue(taskqueue_thread, &thread_reap_task);
 707         callout_reset(&thread_reap_callout, 5 * hz, thread_reap_callout_cb, NULL);
 708 }
 709
 710 /*
 711  * Allocate a thread.
 712  */
 713 struct thread *
 714 thread_alloc(int pages)
 715 {
 716         struct thread *td;
 717         lwpid_t tid;
 718
 719         if (!thread_count_inc()) {
 720                 return (NULL);
 721         }
 722
 723         tid = tid_alloc();
 724         td = uma_zalloc(thread_zone, M_WAITOK);
 725         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
 726         if (!vm_thread_new(td, pages)) {
 727                 uma_zfree(thread_zone, td);
 728                 tid_free(tid);
 729                 thread_count_dec();
 730                 return (NULL);
 731         }
 732         td->td_tid = tid;
 733         cpu_thread_alloc(td);
 734         EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td);
 735         return (td);
 736 }
 737
 738 int
 739 thread_alloc_stack(struct thread *td, int pages)
 740 {
 741
 742         KASSERT(td->td_kstack == 0,
 743             ("thread_alloc_stack called on a thread with kstack"));
 744         if (!vm_thread_new(td, pages))
 745                 return (0);
 746         cpu_thread_alloc(td);
 747         return (1);
 748 }
 749
 750 /*
 751  * Deallocate a thread.
 752  */
 753 static void
 754 thread_free_batched(struct thread *td)
 755 {
 756
 757         lock_profile_thread_exit(td);
 758         if (td->td_cpuset)
 759                 cpuset_rel(td->td_cpuset);
 760         td->td_cpuset = NULL;
 761         cpu_thread_free(td);
 762         if (td->td_kstack != 0)
 763                 vm_thread_dispose(td);
 764         callout_drain(&td->td_slpcallout);
 765         /*
 766          * Freeing handled by the caller.
 767          */
 768         td->td_tid = -1;
 769         uma_zfree(thread_zone, td);
 770 }
 771
 772 void
 773 thread_free(struct thread *td)
 774 {
 775         lwpid_t tid;
 776
 777         EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td);
 778         tid = td->td_tid;
 779         thread_free_batched(td);
 780         tid_free(tid);
 781         thread_count_dec();
 782 }
 783
 784 void
 785 thread_cow_get_proc(struct thread *newtd, struct proc *p)
 786 {
 787
 788         PROC_LOCK_ASSERT(p, MA_OWNED);
 789         newtd->td_realucred = crcowget(p->p_ucred);
 790         newtd->td_ucred = newtd->td_realucred;
 791         newtd->td_limit = lim_hold(p->p_limit);
 792         newtd->td_cowgen = p->p_cowgen;
 793 }
 794
 795 void
 796 thread_cow_get(struct thread *newtd, struct thread *td)
 797 {
 798
 799         MPASS(td->td_realucred == td->td_ucred);
 800         newtd->td_realucred = crcowget(td->td_realucred);
 801         newtd->td_ucred = newtd->td_realucred;
 802         newtd->td_limit = lim_hold(td->td_limit);
 803         newtd->td_cowgen = td->td_cowgen;
 804 }
 805
 806 void
 807 thread_cow_free(struct thread *td)
 808 {
 809
 810         if (td->td_realucred != NULL)
 811                 crcowfree(td);
 812         if (td->td_limit != NULL)
 813                 lim_free(td->td_limit);
 814 }
 815
 816 void
 817 thread_cow_update(struct thread *td)
 818 {
 819         struct proc *p;
 820         struct ucred *oldcred;
 821         struct plimit *oldlimit;
 822
 823         p = td->td_proc;
 824         oldlimit = NULL;
 825         PROC_LOCK(p);
 826         oldcred = crcowsync();
 827         if (td->td_limit != p->p_limit) {
 828                 oldlimit = td->td_limit;
 829                 td->td_limit = lim_hold(p->p_limit);
 830         }
 831         td->td_cowgen = p->p_cowgen;
 832         PROC_UNLOCK(p);
 833         if (oldcred != NULL)
 834                 crfree(oldcred);
 835         if (oldlimit != NULL)
 836                 lim_free(oldlimit);
 837 }
 838
 839 /*
 840  * Discard the current thread and exit from its context.
 841  * Always called with scheduler locked.
 842  *
 843  * Because we can't free a thread while we're operating under its context,
 844  * push the current thread into our CPU's deadthread holder. This means
 845  * we needn't worry about someone else grabbing our context before we
 846  * do a cpu_throw().
 847  */
 848 void
 849 thread_exit(void)
 850 {
 851         uint64_t runtime, new_switchtime;
 852         struct thread *td;
 853         struct thread *td2;
 854         struct proc *p;
 855         int wakeup_swapper;
 856
 857         td = curthread;
 858         p = td->td_proc;
 859
 860         PROC_SLOCK_ASSERT(p, MA_OWNED);
 861         mtx_assert(&Giant, MA_NOTOWNED);
 862
 863         PROC_LOCK_ASSERT(p, MA_OWNED);
 864         KASSERT(p != NULL, ("thread exiting without a process"));
 865         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
 866             (long)p->p_pid, td->td_name);
 867         SDT_PROBE0(proc, , , lwp__exit);
 868         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
 869         MPASS(td->td_realucred == td->td_ucred);
 870
 871         /*
 872          * drop FPU & debug register state storage, or any other
 873          * architecture specific resources that
 874          * would not be on a new untouched process.
 875          */
 876         cpu_thread_exit(td);
 877
 878         /*
 879          * The last thread is left attached to the process
 880          * So that the whole bundle gets recycled. Skip
 881          * all this stuff if we never had threads.
 882          * EXIT clears all sign of other threads when
 883          * it goes to single threading, so the last thread always
 884          * takes the short path.
 885          */
 886         if (p->p_flag & P_HADTHREADS) {
 887                 if (p->p_numthreads > 1) {
 888                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
 889                         thread_unlink(td);
 890                         td2 = FIRST_THREAD_IN_PROC(p);
 891                         sched_exit_thread(td2, td);
 892
 893                         /*
 894                          * The test below is NOT true if we are the
 895                          * sole exiting thread. P_STOPPED_SINGLE is unset
 896                          * in exit1() after it is the only survivor.
 897                          */
 898                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 899                                 if (p->p_numthreads == p->p_suspcount) {
 900                                         thread_lock(p->p_singlethread);
 901                                         wakeup_swapper = thread_unsuspend_one(
 902                                                 p->p_singlethread, p, false);
 903                                         if (wakeup_swapper)
 904                                                 kick_proc0();
 905                                 }
 906                         }
 907
 908                         PCPU_SET(deadthread, td);
 909                 } else {
 910                         /*
 911                          * The last thread is exiting.. but not through exit()
 912                          */
 913                         panic ("thread_exit: Last thread exiting on its own");
 914                 }
 915         }
 916 #ifdef  HWPMC_HOOKS
 917         /*
 918          * If this thread is part of a process that is being tracked by hwpmc(4),
 919          * inform the module of the thread's impending exit.
 920          */
 921         if (PMC_PROC_IS_USING_PMCS(td->td_proc)) {
 922                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 923                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL);
 924         } else if (PMC_SYSTEM_SAMPLING_ACTIVE())
 925                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL);
 926 #endif
 927         PROC_UNLOCK(p);
 928         PROC_STATLOCK(p);
 929         thread_lock(td);
 930         PROC_SUNLOCK(p);
 931
 932         /* Do the same timestamp bookkeeping that mi_switch() would do. */
 933         new_switchtime = cpu_ticks();
 934         runtime = new_switchtime - PCPU_GET(switchtime);
 935         td->td_runtime += runtime;
 936         td->td_incruntime += runtime;
 937         PCPU_SET(switchtime, new_switchtime);
 938         PCPU_SET(switchticks, ticks);
 939         VM_CNT_INC(v_swtch);
 940
 941         /* Save our resource usage in our process. */
 942         td->td_ru.ru_nvcsw++;
 943         ruxagg_locked(p, td);
 944         rucollect(&p->p_ru, &td->td_ru);
 945         PROC_STATUNLOCK(p);
 946
 947         td->td_state = TDS_INACTIVE;
 948 #ifdef WITNESS
 949         witness_thread_exit(td);
 950 #endif
 951         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
 952         sched_throw(td);
 953         panic("I'm a teapot!");
 954         /* NOTREACHED */
 955 }
 956
 957 /*
 958  * Do any thread specific cleanups that may be needed in wait()
 959  * called with Giant, proc and schedlock not held.
 960  */
 961 void
 962 thread_wait(struct proc *p)
 963 {
 964         struct thread *td;
 965
 966         mtx_assert(&Giant, MA_NOTOWNED);
 967         KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()"));
 968         KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking"));
 969         td = FIRST_THREAD_IN_PROC(p);
 970         /* Lock the last thread so we spin until it exits cpu_throw(). */
 971         thread_lock(td);
 972         thread_unlock(td);
 973         lock_profile_thread_exit(td);
 974         cpuset_rel(td->td_cpuset);
 975         td->td_cpuset = NULL;
 976         cpu_thread_clean(td);
 977         thread_cow_free(td);
 978         callout_drain(&td->td_slpcallout);
 979         thread_reap();  /* check for zombie threads etc. */
 980 }
 981
 982 /*
 983  * Link a thread to a process.
 984  * set up anything that needs to be initialized for it to
 985  * be used by the process.
 986  */
 987 void
 988 thread_link(struct thread *td, struct proc *p)
 989 {
 990
 991         /*
 992          * XXX This can't be enabled because it's called for proc0 before
 993          * its lock has been created.
 994          * PROC_LOCK_ASSERT(p, MA_OWNED);
 995          */
 996         td->td_state    = TDS_INACTIVE;
 997         td->td_proc     = p;
 998         td->td_flags    = TDF_INMEM;
 999
1000         LIST_INIT(&td->td_contested);
1001         LIST_INIT(&td->td_lprof[0]);
1002         LIST_INIT(&td->td_lprof[1]);
1003 #ifdef EPOCH_TRACE
1004         SLIST_INIT(&td->td_epochs);
1005 #endif
1006         sigqueue_init(&td->td_sigqueue, p);
1007         callout_init(&td->td_slpcallout, 1);
1008         TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist);
1009         p->p_numthreads++;
1010 }
1011
1012 /*
1013  * Called from:
1014  *  thread_exit()
1015  */
1016 void
1017 thread_unlink(struct thread *td)
1018 {
1019         struct proc *p = td->td_proc;
1020
1021         PROC_LOCK_ASSERT(p, MA_OWNED);
1022 #ifdef EPOCH_TRACE
1023         MPASS(SLIST_EMPTY(&td->td_epochs));
1024 #endif
1025
1026         TAILQ_REMOVE(&p->p_threads, td, td_plist);
1027         p->p_numthreads--;
1028         /* could clear a few other things here */
1029         /* Must  NOT clear links to proc! */
1030 }
1031
1032 static int
1033 calc_remaining(struct proc *p, int mode)
1034 {
1035         int remaining;
1036
1037         PROC_LOCK_ASSERT(p, MA_OWNED);
1038         PROC_SLOCK_ASSERT(p, MA_OWNED);
1039         if (mode == SINGLE_EXIT)
1040                 remaining = p->p_numthreads;
1041         else if (mode == SINGLE_BOUNDARY)
1042                 remaining = p->p_numthreads - p->p_boundary_count;
1043         else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC)
1044                 remaining = p->p_numthreads - p->p_suspcount;
1045         else
1046                 panic("calc_remaining: wrong mode %d", mode);
1047         return (remaining);
1048 }
1049
1050 static int
1051 remain_for_mode(int mode)
1052 {
1053
1054         return (mode == SINGLE_ALLPROC ? 0 : 1);
1055 }
1056
1057 static int
1058 weed_inhib(int mode, struct thread *td2, struct proc *p)
1059 {
1060         int wakeup_swapper;
1061
1062         PROC_LOCK_ASSERT(p, MA_OWNED);
1063         PROC_SLOCK_ASSERT(p, MA_OWNED);
1064         THREAD_LOCK_ASSERT(td2, MA_OWNED);
1065
1066         wakeup_swapper = 0;
1067
1068         /*
1069          * Since the thread lock is dropped by the scheduler we have
1070          * to retry to check for races.
1071          */
1072 restart:
1073         switch (mode) {
1074         case SINGLE_EXIT:
1075                 if (TD_IS_SUSPENDED(td2)) {
1076                         wakeup_swapper |= thread_unsuspend_one(td2, p, true);
1077                         thread_lock(td2);
1078                         goto restart;
1079                 }
1080                 if (TD_CAN_ABORT(td2)) {
1081                         wakeup_swapper |= sleepq_abort(td2, EINTR);
1082                         return (wakeup_swapper);
1083                 }
1084                 break;
1085         case SINGLE_BOUNDARY:
1086         case SINGLE_NO_EXIT:
1087                 if (TD_IS_SUSPENDED(td2) &&
1088                     (td2->td_flags & TDF_BOUNDARY) == 0) {
1089                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
1090                         thread_lock(td2);
1091                         goto restart;
1092                 }
1093                 if (TD_CAN_ABORT(td2)) {
1094                         wakeup_swapper |= sleepq_abort(td2, ERESTART);
1095                         return (wakeup_swapper);
1096                 }
1097                 break;
1098         case SINGLE_ALLPROC:
1099                 /*
1100                  * ALLPROC suspend tries to avoid spurious EINTR for
1101                  * threads sleeping interruptable, by suspending the
1102                  * thread directly, similarly to sig_suspend_threads().
1103                  * Since such sleep is not performed at the user
1104                  * boundary, TDF_BOUNDARY flag is not set, and TDF_ALLPROCSUSP
1105                  * is used to avoid immediate un-suspend.
1106                  */
1107                 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & (TDF_BOUNDARY |
1108                     TDF_ALLPROCSUSP)) == 0) {
1109                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
1110                         thread_lock(td2);
1111                         goto restart;
1112                 }
1113                 if (TD_CAN_ABORT(td2)) {
1114                         if ((td2->td_flags & TDF_SBDRY) == 0) {
1115                                 thread_suspend_one(td2);
1116                                 td2->td_flags |= TDF_ALLPROCSUSP;
1117                         } else {
1118                                 wakeup_swapper |= sleepq_abort(td2, ERESTART);
1119                                 return (wakeup_swapper);
1120                         }
1121                 }
1122                 break;
1123         default:
1124                 break;
1125         }
1126         thread_unlock(td2);
1127         return (wakeup_swapper);
1128 }
1129
1130 /*
1131  * Enforce single-threading.
1132  *
1133  * Returns 1 if the caller must abort (another thread is waiting to
1134  * exit the process or similar). Process is locked!
1135  * Returns 0 when you are successfully the only thread running.
1136  * A process has successfully single threaded in the suspend mode when
1137  * There are no threads in user mode. Threads in the kernel must be
1138  * allowed to continue until they get to the user boundary. They may even
1139  * copy out their return values and data before suspending. They may however be
1140  * accelerated in reaching the user boundary as we will wake up
1141  * any sleeping threads that are interruptable. (PCATCH).
1142  */
1143 int
1144 thread_single(struct proc *p, int mode)
1145 {
1146         struct thread *td;
1147         struct thread *td2;
1148         int remaining, wakeup_swapper;
1149
1150         td = curthread;
1151         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1152             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1153             ("invalid mode %d", mode));
1154         /*
1155          * If allowing non-ALLPROC singlethreading for non-curproc
1156          * callers, calc_remaining() and remain_for_mode() should be
1157          * adjusted to also account for td->td_proc != p.  For now
1158          * this is not implemented because it is not used.
1159          */
1160         KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) ||
1161             (mode != SINGLE_ALLPROC && td->td_proc == p),
1162             ("mode %d proc %p curproc %p", mode, p, td->td_proc));
1163         mtx_assert(&Giant, MA_NOTOWNED);
1164         PROC_LOCK_ASSERT(p, MA_OWNED);
1165
1166         if ((p->p_flag & P_HADTHREADS) == 0 && mode != SINGLE_ALLPROC)
1167                 return (0);
1168
1169         /* Is someone already single threading? */
1170         if (p->p_singlethread != NULL && p->p_singlethread != td)
1171                 return (1);
1172
1173         if (mode == SINGLE_EXIT) {
1174                 p->p_flag |= P_SINGLE_EXIT;
1175                 p->p_flag &= ~P_SINGLE_BOUNDARY;
1176         } else {
1177                 p->p_flag &= ~P_SINGLE_EXIT;
1178                 if (mode == SINGLE_BOUNDARY)
1179                         p->p_flag |= P_SINGLE_BOUNDARY;
1180                 else
1181                         p->p_flag &= ~P_SINGLE_BOUNDARY;
1182         }
1183         if (mode == SINGLE_ALLPROC)
1184                 p->p_flag |= P_TOTAL_STOP;
1185         p->p_flag |= P_STOPPED_SINGLE;
1186         PROC_SLOCK(p);
1187         p->p_singlethread = td;
1188         remaining = calc_remaining(p, mode);
1189         while (remaining != remain_for_mode(mode)) {
1190                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
1191                         goto stopme;
1192                 wakeup_swapper = 0;
1193                 FOREACH_THREAD_IN_PROC(p, td2) {
1194                         if (td2 == td)
1195                                 continue;
1196                         thread_lock(td2);
1197                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
1198                         if (TD_IS_INHIBITED(td2)) {
1199                                 wakeup_swapper |= weed_inhib(mode, td2, p);
1200 #ifdef SMP
1201                         } else if (TD_IS_RUNNING(td2) && td != td2) {
1202                                 forward_signal(td2);
1203                                 thread_unlock(td2);
1204 #endif
1205                         } else
1206                                 thread_unlock(td2);
1207                 }
1208                 if (wakeup_swapper)
1209                         kick_proc0();
1210                 remaining = calc_remaining(p, mode);
1211
1212                 /*
1213                  * Maybe we suspended some threads.. was it enough?
1214                  */
1215                 if (remaining == remain_for_mode(mode))
1216                         break;
1217
1218 stopme:
1219                 /*
1220                  * Wake us up when everyone else has suspended.
1221                  * In the mean time we suspend as well.
1222                  */
1223                 thread_suspend_switch(td, p);
1224                 remaining = calc_remaining(p, mode);
1225         }
1226         if (mode == SINGLE_EXIT) {
1227                 /*
1228                  * Convert the process to an unthreaded process.  The
1229                  * SINGLE_EXIT is called by exit1() or execve(), in
1230                  * both cases other threads must be retired.
1231                  */
1232                 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads"));
1233                 p->p_singlethread = NULL;
1234                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS);
1235
1236                 /*
1237                  * Wait for any remaining threads to exit cpu_throw().
1238                  */
1239                 while (p->p_exitthreads != 0) {
1240                         PROC_SUNLOCK(p);
1241                         PROC_UNLOCK(p);
1242                         sched_relinquish(td);
1243                         PROC_LOCK(p);
1244                         PROC_SLOCK(p);
1245                 }
1246         } else if (mode == SINGLE_BOUNDARY) {
1247                 /*
1248                  * Wait until all suspended threads are removed from
1249                  * the processors.  The thread_suspend_check()
1250                  * increments p_boundary_count while it is still
1251                  * running, which makes it possible for the execve()
1252                  * to destroy vmspace while our other threads are
1253                  * still using the address space.
1254                  *
1255                  * We lock the thread, which is only allowed to
1256                  * succeed after context switch code finished using
1257                  * the address space.
1258                  */
1259                 FOREACH_THREAD_IN_PROC(p, td2) {
1260                         if (td2 == td)
1261                                 continue;
1262                         thread_lock(td2);
1263                         KASSERT((td2->td_flags & TDF_BOUNDARY) != 0,
1264                             ("td %p not on boundary", td2));
1265                         KASSERT(TD_IS_SUSPENDED(td2),
1266                             ("td %p is not suspended", td2));
1267                         thread_unlock(td2);
1268                 }
1269         }
1270         PROC_SUNLOCK(p);
1271         return (0);
1272 }
1273
1274 bool
1275 thread_suspend_check_needed(void)
1276 {
1277         struct proc *p;
1278         struct thread *td;
1279
1280         td = curthread;
1281         p = td->td_proc;
1282         PROC_LOCK_ASSERT(p, MA_OWNED);
1283         return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 &&
1284             (td->td_dbgflags & TDB_SUSPEND) != 0));
1285 }
1286
1287 /*
1288  * Called in from locations that can safely check to see
1289  * whether we have to suspend or at least throttle for a
1290  * single-thread event (e.g. fork).
1291  *
1292  * Such locations include userret().
1293  * If the "return_instead" argument is non zero, the thread must be able to
1294  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
1295  *
1296  * The 'return_instead' argument tells the function if it may do a
1297  * thread_exit() or suspend, or whether the caller must abort and back
1298  * out instead.
1299  *
1300  * If the thread that set the single_threading request has set the
1301  * P_SINGLE_EXIT bit in the process flags then this call will never return
1302  * if 'return_instead' is false, but will exit.
1303  *
1304  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
1305  *---------------+--------------------+---------------------
1306  *       0       | returns 0          |   returns 0 or 1
1307  *               | when ST ends       |   immediately
1308  *---------------+--------------------+---------------------
1309  *       1       | thread exits       |   returns 1
1310  *               |                    |  immediately
1311  * 0 = thread_exit() or suspension ok,
1312  * other = return error instead of stopping the thread.
1313  *
1314  * While a full suspension is under effect, even a single threading
1315  * thread would be suspended if it made this call (but it shouldn't).
1316  * This call should only be made from places where
1317  * thread_exit() would be safe as that may be the outcome unless
1318  * return_instead is set.
1319  */
1320 int
1321 thread_suspend_check(int return_instead)
1322 {
1323         struct thread *td;
1324         struct proc *p;
1325         int wakeup_swapper;
1326
1327         td = curthread;
1328         p = td->td_proc;
1329         mtx_assert(&Giant, MA_NOTOWNED);
1330         PROC_LOCK_ASSERT(p, MA_OWNED);
1331         while (thread_suspend_check_needed()) {
1332                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1333                         KASSERT(p->p_singlethread != NULL,
1334                             ("singlethread not set"));
1335                         /*
1336                          * The only suspension in action is a
1337                          * single-threading. Single threader need not stop.
1338                          * It is safe to access p->p_singlethread unlocked
1339                          * because it can only be set to our address by us.
1340                          */
1341                         if (p->p_singlethread == td)
1342                                 return (0);     /* Exempt from stopping. */
1343                 }
1344                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
1345                         return (EINTR);
1346
1347                 /* Should we goto user boundary if we didn't come from there? */
1348                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1349                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
1350                         return (ERESTART);
1351
1352                 /*
1353                  * Ignore suspend requests if they are deferred.
1354                  */
1355                 if ((td->td_flags & TDF_SBDRY) != 0) {
1356                         KASSERT(return_instead,
1357                             ("TDF_SBDRY set for unsafe thread_suspend_check"));
1358                         KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) !=
1359                             (TDF_SEINTR | TDF_SERESTART),
1360                             ("both TDF_SEINTR and TDF_SERESTART"));
1361                         return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0);
1362                 }
1363
1364                 /*
1365                  * If the process is waiting for us to exit,
1366                  * this thread should just suicide.
1367                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
1368                  */
1369                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
1370                         PROC_UNLOCK(p);
1371
1372                         /*
1373                          * Allow Linux emulation layer to do some work
1374                          * before thread suicide.
1375                          */
1376                         if (__predict_false(p->p_sysent->sv_thread_detach != NULL))
1377                                 (p->p_sysent->sv_thread_detach)(td);
1378                         umtx_thread_exit(td);
1379                         kern_thr_exit(td);
1380                         panic("stopped thread did not exit");
1381                 }
1382
1383                 PROC_SLOCK(p);
1384                 thread_stopped(p);
1385                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1386                         if (p->p_numthreads == p->p_suspcount + 1) {
1387                                 thread_lock(p->p_singlethread);
1388                                 wakeup_swapper = thread_unsuspend_one(
1389                                     p->p_singlethread, p, false);
1390                                 if (wakeup_swapper)
1391                                         kick_proc0();
1392                         }
1393                 }
1394                 PROC_UNLOCK(p);
1395                 thread_lock(td);
1396                 /*
1397                  * When a thread suspends, it just
1398                  * gets taken off all queues.
1399                  */
1400                 thread_suspend_one(td);
1401                 if (return_instead == 0) {
1402                         p->p_boundary_count++;
1403                         td->td_flags |= TDF_BOUNDARY;
1404                 }
1405                 PROC_SUNLOCK(p);
1406                 mi_switch(SW_INVOL | SWT_SUSPEND);
1407                 PROC_LOCK(p);
1408         }
1409         return (0);
1410 }
1411
1412 /*
1413  * Check for possible stops and suspensions while executing a
1414  * casueword or similar transiently failing operation.
1415  *
1416  * The sleep argument controls whether the function can handle a stop
1417  * request itself or it should return ERESTART and the request is
1418  * proceed at the kernel/user boundary in ast.
1419  *
1420  * Typically, when retrying due to casueword(9) failure (rv == 1), we
1421  * should handle the stop requests there, with exception of cases when
1422  * the thread owns a kernel resource, for instance busied the umtx
1423  * key, or when functions return immediately if thread_check_susp()
1424  * returned non-zero.  On the other hand, retrying the whole lock
1425  * operation, we better not stop there but delegate the handling to
1426  * ast.
1427  *
1428  * If the request is for thread termination P_SINGLE_EXIT, we cannot
1429  * handle it at all, and simply return EINTR.
1430  */
1431 int
1432 thread_check_susp(struct thread *td, bool sleep)
1433 {
1434         struct proc *p;
1435         int error;
1436
1437         /*
1438          * The check for TDF_NEEDSUSPCHK is racy, but it is enough to
1439          * eventually break the lockstep loop.
1440          */
1441         if ((td->td_flags & TDF_NEEDSUSPCHK) == 0)
1442                 return (0);
1443         error = 0;
1444         p = td->td_proc;
1445         PROC_LOCK(p);
1446         if (p->p_flag & P_SINGLE_EXIT)
1447                 error = EINTR;
1448         else if (P_SHOULDSTOP(p) ||
1449             ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND)))
1450                 error = sleep ? thread_suspend_check(0) : ERESTART;
1451         PROC_UNLOCK(p);
1452         return (error);
1453 }
1454
1455 void
1456 thread_suspend_switch(struct thread *td, struct proc *p)
1457 {
1458
1459         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1460         PROC_LOCK_ASSERT(p, MA_OWNED);
1461         PROC_SLOCK_ASSERT(p, MA_OWNED);
1462         /*
1463          * We implement thread_suspend_one in stages here to avoid
1464          * dropping the proc lock while the thread lock is owned.
1465          */
1466         if (p == td->td_proc) {
1467                 thread_stopped(p);
1468                 p->p_suspcount++;
1469         }
1470         PROC_UNLOCK(p);
1471         thread_lock(td);
1472         td->td_flags &= ~TDF_NEEDSUSPCHK;
1473         TD_SET_SUSPENDED(td);
1474         sched_sleep(td, 0);
1475         PROC_SUNLOCK(p);
1476         DROP_GIANT();
1477         mi_switch(SW_VOL | SWT_SUSPEND);
1478         PICKUP_GIANT();
1479         PROC_LOCK(p);
1480         PROC_SLOCK(p);
1481 }
1482
1483 void
1484 thread_suspend_one(struct thread *td)
1485 {
1486         struct proc *p;
1487
1488         p = td->td_proc;
1489         PROC_SLOCK_ASSERT(p, MA_OWNED);
1490         THREAD_LOCK_ASSERT(td, MA_OWNED);
1491         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1492         p->p_suspcount++;
1493         td->td_flags &= ~TDF_NEEDSUSPCHK;
1494         TD_SET_SUSPENDED(td);
1495         sched_sleep(td, 0);
1496 }
1497
1498 static int
1499 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary)
1500 {
1501
1502         THREAD_LOCK_ASSERT(td, MA_OWNED);
1503         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
1504         TD_CLR_SUSPENDED(td);
1505         td->td_flags &= ~TDF_ALLPROCSUSP;
1506         if (td->td_proc == p) {
1507                 PROC_SLOCK_ASSERT(p, MA_OWNED);
1508                 p->p_suspcount--;
1509                 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) {
1510                         td->td_flags &= ~TDF_BOUNDARY;
1511                         p->p_boundary_count--;
1512                 }
1513         }
1514         return (setrunnable(td, 0));
1515 }
1516
1517 /*
1518  * Allow all threads blocked by single threading to continue running.
1519  */
1520 void
1521 thread_unsuspend(struct proc *p)
1522 {
1523         struct thread *td;
1524         int wakeup_swapper;
1525
1526         PROC_LOCK_ASSERT(p, MA_OWNED);
1527         PROC_SLOCK_ASSERT(p, MA_OWNED);
1528         wakeup_swapper = 0;
1529         if (!P_SHOULDSTOP(p)) {
1530                 FOREACH_THREAD_IN_PROC(p, td) {
1531                         thread_lock(td);
1532                         if (TD_IS_SUSPENDED(td)) {
1533                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1534                                     true);
1535                         } else
1536                                 thread_unlock(td);
1537                 }
1538         } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1539             p->p_numthreads == p->p_suspcount) {
1540                 /*
1541                  * Stopping everything also did the job for the single
1542                  * threading request. Now we've downgraded to single-threaded,
1543                  * let it continue.
1544                  */
1545                 if (p->p_singlethread->td_proc == p) {
1546                         thread_lock(p->p_singlethread);
1547                         wakeup_swapper = thread_unsuspend_one(
1548                             p->p_singlethread, p, false);
1549                 }
1550         }
1551         if (wakeup_swapper)
1552                 kick_proc0();
1553 }
1554
1555 /*
1556  * End the single threading mode..
1557  */
1558 void
1559 thread_single_end(struct proc *p, int mode)
1560 {
1561         struct thread *td;
1562         int wakeup_swapper;
1563
1564         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1565             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1566             ("invalid mode %d", mode));
1567         PROC_LOCK_ASSERT(p, MA_OWNED);
1568         KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) ||
1569             (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0),
1570             ("mode %d does not match P_TOTAL_STOP", mode));
1571         KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread,
1572             ("thread_single_end from other thread %p %p",
1573             curthread, p->p_singlethread));
1574         KASSERT(mode != SINGLE_BOUNDARY ||
1575             (p->p_flag & P_SINGLE_BOUNDARY) != 0,
1576             ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag));
1577         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY |
1578             P_TOTAL_STOP);
1579         PROC_SLOCK(p);
1580         p->p_singlethread = NULL;
1581         wakeup_swapper = 0;
1582         /*
1583          * If there are other threads they may now run,
1584          * unless of course there is a blanket 'stop order'
1585          * on the process. The single threader must be allowed
1586          * to continue however as this is a bad place to stop.
1587          */
1588         if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) {
1589                 FOREACH_THREAD_IN_PROC(p, td) {
1590                         thread_lock(td);
1591                         if (TD_IS_SUSPENDED(td)) {
1592                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1593                                     mode == SINGLE_BOUNDARY);
1594                         } else
1595                                 thread_unlock(td);
1596                 }
1597         }
1598         KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0,
1599             ("inconsistent boundary count %d", p->p_boundary_count));
1600         PROC_SUNLOCK(p);
1601         if (wakeup_swapper)
1602                 kick_proc0();
1603 }
1604
1605 /*
1606  * Locate a thread by number and return with proc lock held.
1607  *
1608  * thread exit establishes proc -> tidhash lock ordering, but lookup
1609  * takes tidhash first and needs to return locked proc.
1610  *
1611  * The problem is worked around by relying on type-safety of both
1612  * structures and doing the work in 2 steps:
1613  * - tidhash-locked lookup which saves both thread and proc pointers
1614  * - proc-locked verification that the found thread still matches
1615  */
1616 static bool
1617 tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp)
1618 {
1619 #define RUN_THRESH      16
1620         struct proc *p;
1621         struct thread *td;
1622         int run;
1623         bool locked;
1624
1625         run = 0;
1626         rw_rlock(TIDHASHLOCK(tid));
1627         locked = true;
1628         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
1629                 if (td->td_tid != tid) {
1630                         run++;
1631                         continue;
1632                 }
1633                 p = td->td_proc;
1634                 if (pid != -1 && p->p_pid != pid) {
1635                         td = NULL;
1636                         break;
1637                 }
1638                 if (run > RUN_THRESH) {
1639                         if (rw_try_upgrade(TIDHASHLOCK(tid))) {
1640                                 LIST_REMOVE(td, td_hash);
1641                                 LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1642                                         td, td_hash);
1643                                 rw_wunlock(TIDHASHLOCK(tid));
1644                                 locked = false;
1645                                 break;
1646                         }
1647                 }
1648                 break;
1649         }
1650         if (locked)
1651                 rw_runlock(TIDHASHLOCK(tid));
1652         if (td == NULL)
1653                 return (false);
1654         *pp = p;
1655         *tdp = td;
1656         return (true);
1657 }
1658
1659 struct thread *
1660 tdfind(lwpid_t tid, pid_t pid)
1661 {
1662         struct proc *p;
1663         struct thread *td;
1664
1665         td = curthread;
1666         if (td->td_tid == tid) {
1667                 if (pid != -1 && td->td_proc->p_pid != pid)
1668                         return (NULL);
1669                 PROC_LOCK(td->td_proc);
1670                 return (td);
1671         }
1672
1673         for (;;) {
1674                 if (!tdfind_hash(tid, pid, &p, &td))
1675                         return (NULL);
1676                 PROC_LOCK(p);
1677                 if (td->td_tid != tid) {
1678                         PROC_UNLOCK(p);
1679                         continue;
1680                 }
1681                 if (td->td_proc != p) {
1682                         PROC_UNLOCK(p);
1683                         continue;
1684                 }
1685                 if (p->p_state == PRS_NEW) {
1686                         PROC_UNLOCK(p);
1687                         return (NULL);
1688                 }
1689                 return (td);
1690         }
1691 }
1692
1693 void
1694 tidhash_add(struct thread *td)
1695 {
1696         rw_wlock(TIDHASHLOCK(td->td_tid));
1697         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1698         rw_wunlock(TIDHASHLOCK(td->td_tid));
1699 }
1700
1701 void
1702 tidhash_remove(struct thread *td)
1703 {
1704
1705         rw_wlock(TIDHASHLOCK(td->td_tid));
1706         LIST_REMOVE(td, td_hash);
1707         rw_wunlock(TIDHASHLOCK(td->td_tid));
1708 }