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) == 0x3b8,
 100     "struct proc KBI p_filemon");
 101 _Static_assert(offsetof(struct proc, p_comm) == 0x3d0,
 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) == 0x268,
 120     "struct proc KBI p_filemon");
 121 _Static_assert(offsetof(struct proc, p_comm) == 0x27c,
 122     "struct proc KBI p_comm");
 123 _Static_assert(offsetof(struct proc, p_emuldata) == 0x308,
 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_SET_STATE(td, 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_GET_STATE(td)) {
 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,
 545             thread_reap_callout_cb, NULL);
 546 }
 547
 548 /*
 549  * Place an unused thread on the zombie list.
 550  */
 551 void
 552 thread_zombie(struct thread *td)
 553 {
 554         struct thread_domain_data *tdd;
 555         struct thread *ztd;
 556
 557         tdd = &thread_domain_data[td->td_allocdomain];
 558         ztd = atomic_load_ptr(&tdd->tdd_zombies);
 559         for (;;) {
 560                 td->td_zombie = ztd;
 561                 if (atomic_fcmpset_rel_ptr((uintptr_t *)&tdd->tdd_zombies,
 562                     (uintptr_t *)&ztd, (uintptr_t)td))
 563                         break;
 564                 continue;
 565         }
 566 }
 567
 568 /*
 569  * Release a thread that has exited after cpu_throw().
 570  */
 571 void
 572 thread_stash(struct thread *td)
 573 {
 574         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
 575         thread_zombie(td);
 576 }
 577
 578 /*
 579  * Reap zombies from passed domain.
 580  */
 581 static void
 582 thread_reap_domain(struct thread_domain_data *tdd)
 583 {
 584         struct thread *itd, *ntd;
 585         struct tidbatch tidbatch;
 586         struct credbatch credbatch;
 587         int tdcount;
 588         struct plimit *lim;
 589         int limcount;
 590
 591         /*
 592          * Reading upfront is pessimal if followed by concurrent atomic_swap,
 593          * but most of the time the list is empty.
 594          */
 595         if (tdd->tdd_zombies == NULL)
 596                 return;
 597
 598         itd = (struct thread *)atomic_swap_ptr((uintptr_t *)&tdd->tdd_zombies,
 599             (uintptr_t)NULL);
 600         if (itd == NULL)
 601                 return;
 602
 603         /*
 604          * Multiple CPUs can get here, the race is fine as ticks is only
 605          * advisory.
 606          */
 607         tdd->tdd_reapticks = ticks;
 608
 609         tidbatch_prep(&tidbatch);
 610         credbatch_prep(&credbatch);
 611         tdcount = 0;
 612         lim = NULL;
 613         limcount = 0;
 614
 615         while (itd != NULL) {
 616                 ntd = itd->td_zombie;
 617                 EVENTHANDLER_DIRECT_INVOKE(thread_dtor, itd);
 618                 tidbatch_add(&tidbatch, itd);
 619                 credbatch_add(&credbatch, itd);
 620                 MPASS(itd->td_limit != NULL);
 621                 if (lim != itd->td_limit) {
 622                         if (limcount != 0) {
 623                                 lim_freen(lim, limcount);
 624                                 limcount = 0;
 625                         }
 626                 }
 627                 lim = itd->td_limit;
 628                 limcount++;
 629                 thread_free_batched(itd);
 630                 tidbatch_process(&tidbatch);
 631                 credbatch_process(&credbatch);
 632                 tdcount++;
 633                 if (tdcount == 32) {
 634                         thread_count_sub(tdcount);
 635                         tdcount = 0;
 636                 }
 637                 itd = ntd;
 638         }
 639
 640         tidbatch_final(&tidbatch);
 641         credbatch_final(&credbatch);
 642         if (tdcount != 0) {
 643                 thread_count_sub(tdcount);
 644         }
 645         MPASS(limcount != 0);
 646         lim_freen(lim, limcount);
 647 }
 648
 649 /*
 650  * Reap zombies from all domains.
 651  */
 652 static void
 653 thread_reap_all(void)
 654 {
 655         struct thread_domain_data *tdd;
 656         int i, domain;
 657
 658         domain = PCPU_GET(domain);
 659         for (i = 0; i < vm_ndomains; i++) {
 660                 tdd = &thread_domain_data[(i + domain) % vm_ndomains];
 661                 thread_reap_domain(tdd);
 662         }
 663 }
 664
 665 /*
 666  * Reap zombies from local domain.
 667  */
 668 static void
 669 thread_reap(void)
 670 {
 671         struct thread_domain_data *tdd;
 672         int domain;
 673
 674         domain = PCPU_GET(domain);
 675         tdd = &thread_domain_data[domain];
 676
 677         thread_reap_domain(tdd);
 678 }
 679
 680 static void
 681 thread_reap_task_cb(void *arg __unused, int pending __unused)
 682 {
 683
 684         thread_reap_all();
 685 }
 686
 687 static void
 688 thread_reap_callout_cb(void *arg __unused)
 689 {
 690         struct thread_domain_data *tdd;
 691         int i, cticks, lticks;
 692         bool wantreap;
 693
 694         wantreap = false;
 695         cticks = atomic_load_int(&ticks);
 696         for (i = 0; i < vm_ndomains; i++) {
 697                 tdd = &thread_domain_data[i];
 698                 lticks = tdd->tdd_reapticks;
 699                 if (tdd->tdd_zombies != NULL &&
 700                     (u_int)(cticks - lticks) > 5 * hz) {
 701                         wantreap = true;
 702                         break;
 703                 }
 704         }
 705
 706         if (wantreap)
 707                 taskqueue_enqueue(taskqueue_thread, &thread_reap_task);
 708         callout_reset(&thread_reap_callout, 5 * hz,
 709             thread_reap_callout_cb, NULL);
 710 }
 711
 712 /*
 713  * Calling this function guarantees that any thread that exited before
 714  * the call is reaped when the function returns.  By 'exited' we mean
 715  * a thread removed from the process linkage with thread_unlink().
 716  * Practically this means that caller must lock/unlock corresponding
 717  * process lock before the call, to synchronize with thread_exit().
 718  */
 719 void
 720 thread_reap_barrier(void)
 721 {
 722         struct task *t;
 723
 724         /*
 725          * First do context switches to each CPU to ensure that all
 726          * PCPU pc_deadthreads are moved to zombie list.
 727          */
 728         quiesce_all_cpus("", PDROP);
 729
 730         /*
 731          * Second, fire the task in the same thread as normal
 732          * thread_reap() is done, to serialize reaping.
 733          */
 734         t = malloc(sizeof(*t), M_TEMP, M_WAITOK);
 735         TASK_INIT(t, 0, thread_reap_task_cb, t);
 736         taskqueue_enqueue(taskqueue_thread, t);
 737         taskqueue_drain(taskqueue_thread, t);
 738         free(t, M_TEMP);
 739 }
 740
 741 /*
 742  * Allocate a thread.
 743  */
 744 struct thread *
 745 thread_alloc(int pages)
 746 {
 747         struct thread *td;
 748         lwpid_t tid;
 749
 750         if (!thread_count_inc()) {
 751                 return (NULL);
 752         }
 753
 754         tid = tid_alloc();
 755         td = uma_zalloc(thread_zone, M_WAITOK);
 756         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
 757         if (!vm_thread_new(td, pages)) {
 758                 uma_zfree(thread_zone, td);
 759                 tid_free(tid);
 760                 thread_count_dec();
 761                 return (NULL);
 762         }
 763         td->td_tid = tid;
 764         cpu_thread_alloc(td);
 765         EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td);
 766         return (td);
 767 }
 768
 769 int
 770 thread_alloc_stack(struct thread *td, int pages)
 771 {
 772
 773         KASSERT(td->td_kstack == 0,
 774             ("thread_alloc_stack called on a thread with kstack"));
 775         if (!vm_thread_new(td, pages))
 776                 return (0);
 777         cpu_thread_alloc(td);
 778         return (1);
 779 }
 780
 781 /*
 782  * Deallocate a thread.
 783  */
 784 static void
 785 thread_free_batched(struct thread *td)
 786 {
 787
 788         lock_profile_thread_exit(td);
 789         if (td->td_cpuset)
 790                 cpuset_rel(td->td_cpuset);
 791         td->td_cpuset = NULL;
 792         cpu_thread_free(td);
 793         if (td->td_kstack != 0)
 794                 vm_thread_dispose(td);
 795         callout_drain(&td->td_slpcallout);
 796         /*
 797          * Freeing handled by the caller.
 798          */
 799         td->td_tid = -1;
 800         uma_zfree(thread_zone, td);
 801 }
 802
 803 void
 804 thread_free(struct thread *td)
 805 {
 806         lwpid_t tid;
 807
 808         EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td);
 809         tid = td->td_tid;
 810         thread_free_batched(td);
 811         tid_free(tid);
 812         thread_count_dec();
 813 }
 814
 815 void
 816 thread_cow_get_proc(struct thread *newtd, struct proc *p)
 817 {
 818
 819         PROC_LOCK_ASSERT(p, MA_OWNED);
 820         newtd->td_realucred = crcowget(p->p_ucred);
 821         newtd->td_ucred = newtd->td_realucred;
 822         newtd->td_limit = lim_hold(p->p_limit);
 823         newtd->td_cowgen = p->p_cowgen;
 824 }
 825
 826 void
 827 thread_cow_get(struct thread *newtd, struct thread *td)
 828 {
 829
 830         MPASS(td->td_realucred == td->td_ucred);
 831         newtd->td_realucred = crcowget(td->td_realucred);
 832         newtd->td_ucred = newtd->td_realucred;
 833         newtd->td_limit = lim_hold(td->td_limit);
 834         newtd->td_cowgen = td->td_cowgen;
 835 }
 836
 837 void
 838 thread_cow_free(struct thread *td)
 839 {
 840
 841         if (td->td_realucred != NULL)
 842                 crcowfree(td);
 843         if (td->td_limit != NULL)
 844                 lim_free(td->td_limit);
 845 }
 846
 847 void
 848 thread_cow_update(struct thread *td)
 849 {
 850         struct proc *p;
 851         struct ucred *oldcred;
 852         struct plimit *oldlimit;
 853
 854         p = td->td_proc;
 855         oldlimit = NULL;
 856         PROC_LOCK(p);
 857         oldcred = crcowsync();
 858         if (td->td_limit != p->p_limit) {
 859                 oldlimit = td->td_limit;
 860                 td->td_limit = lim_hold(p->p_limit);
 861         }
 862         td->td_cowgen = p->p_cowgen;
 863         PROC_UNLOCK(p);
 864         if (oldcred != NULL)
 865                 crfree(oldcred);
 866         if (oldlimit != NULL)
 867                 lim_free(oldlimit);
 868 }
 869
 870 /*
 871  * Discard the current thread and exit from its context.
 872  * Always called with scheduler locked.
 873  *
 874  * Because we can't free a thread while we're operating under its context,
 875  * push the current thread into our CPU's deadthread holder. This means
 876  * we needn't worry about someone else grabbing our context before we
 877  * do a cpu_throw().
 878  */
 879 void
 880 thread_exit(void)
 881 {
 882         uint64_t runtime, new_switchtime;
 883         struct thread *td;
 884         struct thread *td2;
 885         struct proc *p;
 886         int wakeup_swapper;
 887
 888         td = curthread;
 889         p = td->td_proc;
 890
 891         PROC_SLOCK_ASSERT(p, MA_OWNED);
 892         mtx_assert(&Giant, MA_NOTOWNED);
 893
 894         PROC_LOCK_ASSERT(p, MA_OWNED);
 895         KASSERT(p != NULL, ("thread exiting without a process"));
 896         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
 897             (long)p->p_pid, td->td_name);
 898         SDT_PROBE0(proc, , , lwp__exit);
 899         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
 900         MPASS(td->td_realucred == td->td_ucred);
 901
 902         /*
 903          * drop FPU & debug register state storage, or any other
 904          * architecture specific resources that
 905          * would not be on a new untouched process.
 906          */
 907         cpu_thread_exit(td);
 908
 909         /*
 910          * The last thread is left attached to the process
 911          * So that the whole bundle gets recycled. Skip
 912          * all this stuff if we never had threads.
 913          * EXIT clears all sign of other threads when
 914          * it goes to single threading, so the last thread always
 915          * takes the short path.
 916          */
 917         if (p->p_flag & P_HADTHREADS) {
 918                 if (p->p_numthreads > 1) {
 919                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
 920                         thread_unlink(td);
 921                         td2 = FIRST_THREAD_IN_PROC(p);
 922                         sched_exit_thread(td2, td);
 923
 924                         /*
 925                          * The test below is NOT true if we are the
 926                          * sole exiting thread. P_STOPPED_SINGLE is unset
 927                          * in exit1() after it is the only survivor.
 928                          */
 929                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 930                                 if (p->p_numthreads == p->p_suspcount) {
 931                                         thread_lock(p->p_singlethread);
 932                                         wakeup_swapper = thread_unsuspend_one(
 933                                                 p->p_singlethread, p, false);
 934                                         if (wakeup_swapper)
 935                                                 kick_proc0();
 936                                 }
 937                         }
 938
 939                         PCPU_SET(deadthread, td);
 940                 } else {
 941                         /*
 942                          * The last thread is exiting.. but not through exit()
 943                          */
 944                         panic ("thread_exit: Last thread exiting on its own");
 945                 }
 946         }
 947 #ifdef  HWPMC_HOOKS
 948         /*
 949          * If this thread is part of a process that is being tracked by hwpmc(4),
 950          * inform the module of the thread's impending exit.
 951          */
 952         if (PMC_PROC_IS_USING_PMCS(td->td_proc)) {
 953                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 954                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL);
 955         } else if (PMC_SYSTEM_SAMPLING_ACTIVE())
 956                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT_LOG, NULL);
 957 #endif
 958         PROC_UNLOCK(p);
 959         PROC_STATLOCK(p);
 960         thread_lock(td);
 961         PROC_SUNLOCK(p);
 962
 963         /* Do the same timestamp bookkeeping that mi_switch() would do. */
 964         new_switchtime = cpu_ticks();
 965         runtime = new_switchtime - PCPU_GET(switchtime);
 966         td->td_runtime += runtime;
 967         td->td_incruntime += runtime;
 968         PCPU_SET(switchtime, new_switchtime);
 969         PCPU_SET(switchticks, ticks);
 970         VM_CNT_INC(v_swtch);
 971
 972         /* Save our resource usage in our process. */
 973         td->td_ru.ru_nvcsw++;
 974         ruxagg_locked(p, td);
 975         rucollect(&p->p_ru, &td->td_ru);
 976         PROC_STATUNLOCK(p);
 977
 978         TD_SET_STATE(td, TDS_INACTIVE);
 979 #ifdef WITNESS
 980         witness_thread_exit(td);
 981 #endif
 982         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
 983         sched_throw(td);
 984         panic("I'm a teapot!");
 985         /* NOTREACHED */
 986 }
 987
 988 /*
 989  * Do any thread specific cleanups that may be needed in wait()
 990  * called with Giant, proc and schedlock not held.
 991  */
 992 void
 993 thread_wait(struct proc *p)
 994 {
 995         struct thread *td;
 996
 997         mtx_assert(&Giant, MA_NOTOWNED);
 998         KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()"));
 999         KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking"));
1000         td = FIRST_THREAD_IN_PROC(p);
1001         /* Lock the last thread so we spin until it exits cpu_throw(). */
1002         thread_lock(td);
1003         thread_unlock(td);
1004         lock_profile_thread_exit(td);
1005         cpuset_rel(td->td_cpuset);
1006         td->td_cpuset = NULL;
1007         cpu_thread_clean(td);
1008         thread_cow_free(td);
1009         callout_drain(&td->td_slpcallout);
1010         thread_reap();  /* check for zombie threads etc. */
1011 }
1012
1013 /*
1014  * Link a thread to a process.
1015  * set up anything that needs to be initialized for it to
1016  * be used by the process.
1017  */
1018 void
1019 thread_link(struct thread *td, struct proc *p)
1020 {
1021
1022         /*
1023          * XXX This can't be enabled because it's called for proc0 before
1024          * its lock has been created.
1025          * PROC_LOCK_ASSERT(p, MA_OWNED);
1026          */
1027         TD_SET_STATE(td, TDS_INACTIVE);
1028         td->td_proc     = p;
1029         td->td_flags    = TDF_INMEM;
1030
1031         LIST_INIT(&td->td_contested);
1032         LIST_INIT(&td->td_lprof[0]);
1033         LIST_INIT(&td->td_lprof[1]);
1034 #ifdef EPOCH_TRACE
1035         SLIST_INIT(&td->td_epochs);
1036 #endif
1037         sigqueue_init(&td->td_sigqueue, p);
1038         callout_init(&td->td_slpcallout, 1);
1039         TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist);
1040         p->p_numthreads++;
1041 }
1042
1043 /*
1044  * Called from:
1045  *  thread_exit()
1046  */
1047 void
1048 thread_unlink(struct thread *td)
1049 {
1050         struct proc *p = td->td_proc;
1051
1052         PROC_LOCK_ASSERT(p, MA_OWNED);
1053 #ifdef EPOCH_TRACE
1054         MPASS(SLIST_EMPTY(&td->td_epochs));
1055 #endif
1056
1057         TAILQ_REMOVE(&p->p_threads, td, td_plist);
1058         p->p_numthreads--;
1059         /* could clear a few other things here */
1060         /* Must  NOT clear links to proc! */
1061 }
1062
1063 static int
1064 calc_remaining(struct proc *p, int mode)
1065 {
1066         int remaining;
1067
1068         PROC_LOCK_ASSERT(p, MA_OWNED);
1069         PROC_SLOCK_ASSERT(p, MA_OWNED);
1070         if (mode == SINGLE_EXIT)
1071                 remaining = p->p_numthreads;
1072         else if (mode == SINGLE_BOUNDARY)
1073                 remaining = p->p_numthreads - p->p_boundary_count;
1074         else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC)
1075                 remaining = p->p_numthreads - p->p_suspcount;
1076         else
1077                 panic("calc_remaining: wrong mode %d", mode);
1078         return (remaining);
1079 }
1080
1081 static int
1082 remain_for_mode(int mode)
1083 {
1084
1085         return (mode == SINGLE_ALLPROC ? 0 : 1);
1086 }
1087
1088 static int
1089 weed_inhib(int mode, struct thread *td2, struct proc *p)
1090 {
1091         int wakeup_swapper;
1092
1093         PROC_LOCK_ASSERT(p, MA_OWNED);
1094         PROC_SLOCK_ASSERT(p, MA_OWNED);
1095         THREAD_LOCK_ASSERT(td2, MA_OWNED);
1096
1097         wakeup_swapper = 0;
1098
1099         /*
1100          * Since the thread lock is dropped by the scheduler we have
1101          * to retry to check for races.
1102          */
1103 restart:
1104         switch (mode) {
1105         case SINGLE_EXIT:
1106                 if (TD_IS_SUSPENDED(td2)) {
1107                         wakeup_swapper |= thread_unsuspend_one(td2, p, true);
1108                         thread_lock(td2);
1109                         goto restart;
1110                 }
1111                 if (TD_CAN_ABORT(td2)) {
1112                         wakeup_swapper |= sleepq_abort(td2, EINTR);
1113                         return (wakeup_swapper);
1114                 }
1115                 break;
1116         case SINGLE_BOUNDARY:
1117         case SINGLE_NO_EXIT:
1118                 if (TD_IS_SUSPENDED(td2) &&
1119                     (td2->td_flags & TDF_BOUNDARY) == 0) {
1120                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
1121                         thread_lock(td2);
1122                         goto restart;
1123                 }
1124                 if (TD_CAN_ABORT(td2)) {
1125                         wakeup_swapper |= sleepq_abort(td2, ERESTART);
1126                         return (wakeup_swapper);
1127                 }
1128                 break;
1129         case SINGLE_ALLPROC:
1130                 /*
1131                  * ALLPROC suspend tries to avoid spurious EINTR for
1132                  * threads sleeping interruptable, by suspending the
1133                  * thread directly, similarly to sig_suspend_threads().
1134                  * Since such sleep is not performed at the user
1135                  * boundary, TDF_BOUNDARY flag is not set, and TDF_ALLPROCSUSP
1136                  * is used to avoid immediate un-suspend.
1137                  */
1138                 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & (TDF_BOUNDARY |
1139                     TDF_ALLPROCSUSP)) == 0) {
1140                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
1141                         thread_lock(td2);
1142                         goto restart;
1143                 }
1144                 if (TD_CAN_ABORT(td2)) {
1145                         if ((td2->td_flags & TDF_SBDRY) == 0) {
1146                                 thread_suspend_one(td2);
1147                                 td2->td_flags |= TDF_ALLPROCSUSP;
1148                         } else {
1149                                 wakeup_swapper |= sleepq_abort(td2, ERESTART);
1150                                 return (wakeup_swapper);
1151                         }
1152                 }
1153                 break;
1154         default:
1155                 break;
1156         }
1157         thread_unlock(td2);
1158         return (wakeup_swapper);
1159 }
1160
1161 /*
1162  * Enforce single-threading.
1163  *
1164  * Returns 1 if the caller must abort (another thread is waiting to
1165  * exit the process or similar). Process is locked!
1166  * Returns 0 when you are successfully the only thread running.
1167  * A process has successfully single threaded in the suspend mode when
1168  * There are no threads in user mode. Threads in the kernel must be
1169  * allowed to continue until they get to the user boundary. They may even
1170  * copy out their return values and data before suspending. They may however be
1171  * accelerated in reaching the user boundary as we will wake up
1172  * any sleeping threads that are interruptable. (PCATCH).
1173  */
1174 int
1175 thread_single(struct proc *p, int mode)
1176 {
1177         struct thread *td;
1178         struct thread *td2;
1179         int remaining, wakeup_swapper;
1180
1181         td = curthread;
1182         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1183             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1184             ("invalid mode %d", mode));
1185         /*
1186          * If allowing non-ALLPROC singlethreading for non-curproc
1187          * callers, calc_remaining() and remain_for_mode() should be
1188          * adjusted to also account for td->td_proc != p.  For now
1189          * this is not implemented because it is not used.
1190          */
1191         KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) ||
1192             (mode != SINGLE_ALLPROC && td->td_proc == p),
1193             ("mode %d proc %p curproc %p", mode, p, td->td_proc));
1194         mtx_assert(&Giant, MA_NOTOWNED);
1195         PROC_LOCK_ASSERT(p, MA_OWNED);
1196
1197         if ((p->p_flag & P_HADTHREADS) == 0 && mode != SINGLE_ALLPROC)
1198                 return (0);
1199
1200         /* Is someone already single threading? */
1201         if (p->p_singlethread != NULL && p->p_singlethread != td)
1202                 return (1);
1203
1204         if (mode == SINGLE_EXIT) {
1205                 p->p_flag |= P_SINGLE_EXIT;
1206                 p->p_flag &= ~P_SINGLE_BOUNDARY;
1207         } else {
1208                 p->p_flag &= ~P_SINGLE_EXIT;
1209                 if (mode == SINGLE_BOUNDARY)
1210                         p->p_flag |= P_SINGLE_BOUNDARY;
1211                 else
1212                         p->p_flag &= ~P_SINGLE_BOUNDARY;
1213         }
1214         if (mode == SINGLE_ALLPROC)
1215                 p->p_flag |= P_TOTAL_STOP;
1216         p->p_flag |= P_STOPPED_SINGLE;
1217         PROC_SLOCK(p);
1218         p->p_singlethread = td;
1219         remaining = calc_remaining(p, mode);
1220         while (remaining != remain_for_mode(mode)) {
1221                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
1222                         goto stopme;
1223                 wakeup_swapper = 0;
1224                 FOREACH_THREAD_IN_PROC(p, td2) {
1225                         if (td2 == td)
1226                                 continue;
1227                         thread_lock(td2);
1228                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
1229                         if (TD_IS_INHIBITED(td2)) {
1230                                 wakeup_swapper |= weed_inhib(mode, td2, p);
1231 #ifdef SMP
1232                         } else if (TD_IS_RUNNING(td2) && td != td2) {
1233                                 forward_signal(td2);
1234                                 thread_unlock(td2);
1235 #endif
1236                         } else
1237                                 thread_unlock(td2);
1238                 }
1239                 if (wakeup_swapper)
1240                         kick_proc0();
1241                 remaining = calc_remaining(p, mode);
1242
1243                 /*
1244                  * Maybe we suspended some threads.. was it enough?
1245                  */
1246                 if (remaining == remain_for_mode(mode))
1247                         break;
1248
1249 stopme:
1250                 /*
1251                  * Wake us up when everyone else has suspended.
1252                  * In the mean time we suspend as well.
1253                  */
1254                 thread_suspend_switch(td, p);
1255                 remaining = calc_remaining(p, mode);
1256         }
1257         if (mode == SINGLE_EXIT) {
1258                 /*
1259                  * Convert the process to an unthreaded process.  The
1260                  * SINGLE_EXIT is called by exit1() or execve(), in
1261                  * both cases other threads must be retired.
1262                  */
1263                 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads"));
1264                 p->p_singlethread = NULL;
1265                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS);
1266
1267                 /*
1268                  * Wait for any remaining threads to exit cpu_throw().
1269                  */
1270                 while (p->p_exitthreads != 0) {
1271                         PROC_SUNLOCK(p);
1272                         PROC_UNLOCK(p);
1273                         sched_relinquish(td);
1274                         PROC_LOCK(p);
1275                         PROC_SLOCK(p);
1276                 }
1277         } else if (mode == SINGLE_BOUNDARY) {
1278                 /*
1279                  * Wait until all suspended threads are removed from
1280                  * the processors.  The thread_suspend_check()
1281                  * increments p_boundary_count while it is still
1282                  * running, which makes it possible for the execve()
1283                  * to destroy vmspace while our other threads are
1284                  * still using the address space.
1285                  *
1286                  * We lock the thread, which is only allowed to
1287                  * succeed after context switch code finished using
1288                  * the address space.
1289                  */
1290                 FOREACH_THREAD_IN_PROC(p, td2) {
1291                         if (td2 == td)
1292                                 continue;
1293                         thread_lock(td2);
1294                         KASSERT((td2->td_flags & TDF_BOUNDARY) != 0,
1295                             ("td %p not on boundary", td2));
1296                         KASSERT(TD_IS_SUSPENDED(td2),
1297                             ("td %p is not suspended", td2));
1298                         thread_unlock(td2);
1299                 }
1300         }
1301         PROC_SUNLOCK(p);
1302         return (0);
1303 }
1304
1305 bool
1306 thread_suspend_check_needed(void)
1307 {
1308         struct proc *p;
1309         struct thread *td;
1310
1311         td = curthread;
1312         p = td->td_proc;
1313         PROC_LOCK_ASSERT(p, MA_OWNED);
1314         return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 &&
1315             (td->td_dbgflags & TDB_SUSPEND) != 0));
1316 }
1317
1318 /*
1319  * Called in from locations that can safely check to see
1320  * whether we have to suspend or at least throttle for a
1321  * single-thread event (e.g. fork).
1322  *
1323  * Such locations include userret().
1324  * If the "return_instead" argument is non zero, the thread must be able to
1325  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
1326  *
1327  * The 'return_instead' argument tells the function if it may do a
1328  * thread_exit() or suspend, or whether the caller must abort and back
1329  * out instead.
1330  *
1331  * If the thread that set the single_threading request has set the
1332  * P_SINGLE_EXIT bit in the process flags then this call will never return
1333  * if 'return_instead' is false, but will exit.
1334  *
1335  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
1336  *---------------+--------------------+---------------------
1337  *       0       | returns 0          |   returns 0 or 1
1338  *               | when ST ends       |   immediately
1339  *---------------+--------------------+---------------------
1340  *       1       | thread exits       |   returns 1
1341  *               |                    |  immediately
1342  * 0 = thread_exit() or suspension ok,
1343  * other = return error instead of stopping the thread.
1344  *
1345  * While a full suspension is under effect, even a single threading
1346  * thread would be suspended if it made this call (but it shouldn't).
1347  * This call should only be made from places where
1348  * thread_exit() would be safe as that may be the outcome unless
1349  * return_instead is set.
1350  */
1351 int
1352 thread_suspend_check(int return_instead)
1353 {
1354         struct thread *td;
1355         struct proc *p;
1356         int wakeup_swapper;
1357
1358         td = curthread;
1359         p = td->td_proc;
1360         mtx_assert(&Giant, MA_NOTOWNED);
1361         PROC_LOCK_ASSERT(p, MA_OWNED);
1362         while (thread_suspend_check_needed()) {
1363                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1364                         KASSERT(p->p_singlethread != NULL,
1365                             ("singlethread not set"));
1366                         /*
1367                          * The only suspension in action is a
1368                          * single-threading. Single threader need not stop.
1369                          * It is safe to access p->p_singlethread unlocked
1370                          * because it can only be set to our address by us.
1371                          */
1372                         if (p->p_singlethread == td)
1373                                 return (0);     /* Exempt from stopping. */
1374                 }
1375                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
1376                         return (EINTR);
1377
1378                 /* Should we goto user boundary if we didn't come from there? */
1379                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1380                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
1381                         return (ERESTART);
1382
1383                 /*
1384                  * Ignore suspend requests if they are deferred.
1385                  */
1386                 if ((td->td_flags & TDF_SBDRY) != 0) {
1387                         KASSERT(return_instead,
1388                             ("TDF_SBDRY set for unsafe thread_suspend_check"));
1389                         KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) !=
1390                             (TDF_SEINTR | TDF_SERESTART),
1391                             ("both TDF_SEINTR and TDF_SERESTART"));
1392                         return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0);
1393                 }
1394
1395                 /*
1396                  * If the process is waiting for us to exit,
1397                  * this thread should just suicide.
1398                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
1399                  */
1400                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
1401                         PROC_UNLOCK(p);
1402
1403                         /*
1404                          * Allow Linux emulation layer to do some work
1405                          * before thread suicide.
1406                          */
1407                         if (__predict_false(p->p_sysent->sv_thread_detach != NULL))
1408                                 (p->p_sysent->sv_thread_detach)(td);
1409                         umtx_thread_exit(td);
1410                         kern_thr_exit(td);
1411                         panic("stopped thread did not exit");
1412                 }
1413
1414                 PROC_SLOCK(p);
1415                 thread_stopped(p);
1416                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1417                         if (p->p_numthreads == p->p_suspcount + 1) {
1418                                 thread_lock(p->p_singlethread);
1419                                 wakeup_swapper = thread_unsuspend_one(
1420                                     p->p_singlethread, p, false);
1421                                 if (wakeup_swapper)
1422                                         kick_proc0();
1423                         }
1424                 }
1425                 PROC_UNLOCK(p);
1426                 thread_lock(td);
1427                 /*
1428                  * When a thread suspends, it just
1429                  * gets taken off all queues.
1430                  */
1431                 thread_suspend_one(td);
1432                 if (return_instead == 0) {
1433                         p->p_boundary_count++;
1434                         td->td_flags |= TDF_BOUNDARY;
1435                 }
1436                 PROC_SUNLOCK(p);
1437                 mi_switch(SW_INVOL | SWT_SUSPEND);
1438                 PROC_LOCK(p);
1439         }
1440         return (0);
1441 }
1442
1443 /*
1444  * Check for possible stops and suspensions while executing a
1445  * casueword or similar transiently failing operation.
1446  *
1447  * The sleep argument controls whether the function can handle a stop
1448  * request itself or it should return ERESTART and the request is
1449  * proceed at the kernel/user boundary in ast.
1450  *
1451  * Typically, when retrying due to casueword(9) failure (rv == 1), we
1452  * should handle the stop requests there, with exception of cases when
1453  * the thread owns a kernel resource, for instance busied the umtx
1454  * key, or when functions return immediately if thread_check_susp()
1455  * returned non-zero.  On the other hand, retrying the whole lock
1456  * operation, we better not stop there but delegate the handling to
1457  * ast.
1458  *
1459  * If the request is for thread termination P_SINGLE_EXIT, we cannot
1460  * handle it at all, and simply return EINTR.
1461  */
1462 int
1463 thread_check_susp(struct thread *td, bool sleep)
1464 {
1465         struct proc *p;
1466         int error;
1467
1468         /*
1469          * The check for TDF_NEEDSUSPCHK is racy, but it is enough to
1470          * eventually break the lockstep loop.
1471          */
1472         if ((td->td_flags & TDF_NEEDSUSPCHK) == 0)
1473                 return (0);
1474         error = 0;
1475         p = td->td_proc;
1476         PROC_LOCK(p);
1477         if (p->p_flag & P_SINGLE_EXIT)
1478                 error = EINTR;
1479         else if (P_SHOULDSTOP(p) ||
1480             ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND)))
1481                 error = sleep ? thread_suspend_check(0) : ERESTART;
1482         PROC_UNLOCK(p);
1483         return (error);
1484 }
1485
1486 void
1487 thread_suspend_switch(struct thread *td, struct proc *p)
1488 {
1489
1490         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1491         PROC_LOCK_ASSERT(p, MA_OWNED);
1492         PROC_SLOCK_ASSERT(p, MA_OWNED);
1493         /*
1494          * We implement thread_suspend_one in stages here to avoid
1495          * dropping the proc lock while the thread lock is owned.
1496          */
1497         if (p == td->td_proc) {
1498                 thread_stopped(p);
1499                 p->p_suspcount++;
1500         }
1501         PROC_UNLOCK(p);
1502         thread_lock(td);
1503         td->td_flags &= ~TDF_NEEDSUSPCHK;
1504         TD_SET_SUSPENDED(td);
1505         sched_sleep(td, 0);
1506         PROC_SUNLOCK(p);
1507         DROP_GIANT();
1508         mi_switch(SW_VOL | SWT_SUSPEND);
1509         PICKUP_GIANT();
1510         PROC_LOCK(p);
1511         PROC_SLOCK(p);
1512 }
1513
1514 void
1515 thread_suspend_one(struct thread *td)
1516 {
1517         struct proc *p;
1518
1519         p = td->td_proc;
1520         PROC_SLOCK_ASSERT(p, MA_OWNED);
1521         THREAD_LOCK_ASSERT(td, MA_OWNED);
1522         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1523         p->p_suspcount++;
1524         td->td_flags &= ~TDF_NEEDSUSPCHK;
1525         TD_SET_SUSPENDED(td);
1526         sched_sleep(td, 0);
1527 }
1528
1529 static int
1530 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary)
1531 {
1532
1533         THREAD_LOCK_ASSERT(td, MA_OWNED);
1534         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
1535         TD_CLR_SUSPENDED(td);
1536         td->td_flags &= ~TDF_ALLPROCSUSP;
1537         if (td->td_proc == p) {
1538                 PROC_SLOCK_ASSERT(p, MA_OWNED);
1539                 p->p_suspcount--;
1540                 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) {
1541                         td->td_flags &= ~TDF_BOUNDARY;
1542                         p->p_boundary_count--;
1543                 }
1544         }
1545         return (setrunnable(td, 0));
1546 }
1547
1548 void
1549 thread_run_flash(struct thread *td)
1550 {
1551         struct proc *p;
1552
1553         p = td->td_proc;
1554         PROC_LOCK_ASSERT(p, MA_OWNED);
1555
1556         if (TD_ON_SLEEPQ(td))
1557                 sleepq_remove_nested(td);
1558         else
1559                 thread_lock(td);
1560
1561         THREAD_LOCK_ASSERT(td, MA_OWNED);
1562         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
1563
1564         TD_CLR_SUSPENDED(td);
1565         PROC_SLOCK(p);
1566         MPASS(p->p_suspcount > 0);
1567         p->p_suspcount--;
1568         PROC_SUNLOCK(p);
1569         if (setrunnable(td, 0))
1570                 kick_proc0();
1571 }
1572
1573 /*
1574  * Allow all threads blocked by single threading to continue running.
1575  */
1576 void
1577 thread_unsuspend(struct proc *p)
1578 {
1579         struct thread *td;
1580         int wakeup_swapper;
1581
1582         PROC_LOCK_ASSERT(p, MA_OWNED);
1583         PROC_SLOCK_ASSERT(p, MA_OWNED);
1584         wakeup_swapper = 0;
1585         if (!P_SHOULDSTOP(p)) {
1586                 FOREACH_THREAD_IN_PROC(p, td) {
1587                         thread_lock(td);
1588                         if (TD_IS_SUSPENDED(td)) {
1589                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1590                                     true);
1591                         } else
1592                                 thread_unlock(td);
1593                 }
1594         } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1595             p->p_numthreads == p->p_suspcount) {
1596                 /*
1597                  * Stopping everything also did the job for the single
1598                  * threading request. Now we've downgraded to single-threaded,
1599                  * let it continue.
1600                  */
1601                 if (p->p_singlethread->td_proc == p) {
1602                         thread_lock(p->p_singlethread);
1603                         wakeup_swapper = thread_unsuspend_one(
1604                             p->p_singlethread, p, false);
1605                 }
1606         }
1607         if (wakeup_swapper)
1608                 kick_proc0();
1609 }
1610
1611 /*
1612  * End the single threading mode..
1613  */
1614 void
1615 thread_single_end(struct proc *p, int mode)
1616 {
1617         struct thread *td;
1618         int wakeup_swapper;
1619
1620         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1621             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1622             ("invalid mode %d", mode));
1623         PROC_LOCK_ASSERT(p, MA_OWNED);
1624         KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) ||
1625             (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0),
1626             ("mode %d does not match P_TOTAL_STOP", mode));
1627         KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread,
1628             ("thread_single_end from other thread %p %p",
1629             curthread, p->p_singlethread));
1630         KASSERT(mode != SINGLE_BOUNDARY ||
1631             (p->p_flag & P_SINGLE_BOUNDARY) != 0,
1632             ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag));
1633         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY |
1634             P_TOTAL_STOP);
1635         PROC_SLOCK(p);
1636         p->p_singlethread = NULL;
1637         wakeup_swapper = 0;
1638         /*
1639          * If there are other threads they may now run,
1640          * unless of course there is a blanket 'stop order'
1641          * on the process. The single threader must be allowed
1642          * to continue however as this is a bad place to stop.
1643          */
1644         if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) {
1645                 FOREACH_THREAD_IN_PROC(p, td) {
1646                         thread_lock(td);
1647                         if (TD_IS_SUSPENDED(td)) {
1648                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1649                                     mode == SINGLE_BOUNDARY);
1650                         } else
1651                                 thread_unlock(td);
1652                 }
1653         }
1654         KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0,
1655             ("inconsistent boundary count %d", p->p_boundary_count));
1656         PROC_SUNLOCK(p);
1657         if (wakeup_swapper)
1658                 kick_proc0();
1659 }
1660
1661 /*
1662  * Locate a thread by number and return with proc lock held.
1663  *
1664  * thread exit establishes proc -> tidhash lock ordering, but lookup
1665  * takes tidhash first and needs to return locked proc.
1666  *
1667  * The problem is worked around by relying on type-safety of both
1668  * structures and doing the work in 2 steps:
1669  * - tidhash-locked lookup which saves both thread and proc pointers
1670  * - proc-locked verification that the found thread still matches
1671  */
1672 static bool
1673 tdfind_hash(lwpid_t tid, pid_t pid, struct proc **pp, struct thread **tdp)
1674 {
1675 #define RUN_THRESH      16
1676         struct proc *p;
1677         struct thread *td;
1678         int run;
1679         bool locked;
1680
1681         run = 0;
1682         rw_rlock(TIDHASHLOCK(tid));
1683         locked = true;
1684         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
1685                 if (td->td_tid != tid) {
1686                         run++;
1687                         continue;
1688                 }
1689                 p = td->td_proc;
1690                 if (pid != -1 && p->p_pid != pid) {
1691                         td = NULL;
1692                         break;
1693                 }
1694                 if (run > RUN_THRESH) {
1695                         if (rw_try_upgrade(TIDHASHLOCK(tid))) {
1696                                 LIST_REMOVE(td, td_hash);
1697                                 LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1698                                         td, td_hash);
1699                                 rw_wunlock(TIDHASHLOCK(tid));
1700                                 locked = false;
1701                                 break;
1702                         }
1703                 }
1704                 break;
1705         }
1706         if (locked)
1707                 rw_runlock(TIDHASHLOCK(tid));
1708         if (td == NULL)
1709                 return (false);
1710         *pp = p;
1711         *tdp = td;
1712         return (true);
1713 }
1714
1715 struct thread *
1716 tdfind(lwpid_t tid, pid_t pid)
1717 {
1718         struct proc *p;
1719         struct thread *td;
1720
1721         td = curthread;
1722         if (td->td_tid == tid) {
1723                 if (pid != -1 && td->td_proc->p_pid != pid)
1724                         return (NULL);
1725                 PROC_LOCK(td->td_proc);
1726                 return (td);
1727         }
1728
1729         for (;;) {
1730                 if (!tdfind_hash(tid, pid, &p, &td))
1731                         return (NULL);
1732                 PROC_LOCK(p);
1733                 if (td->td_tid != tid) {
1734                         PROC_UNLOCK(p);
1735                         continue;
1736                 }
1737                 if (td->td_proc != p) {
1738                         PROC_UNLOCK(p);
1739                         continue;
1740                 }
1741                 if (p->p_state == PRS_NEW) {
1742                         PROC_UNLOCK(p);
1743                         return (NULL);
1744                 }
1745                 return (td);
1746         }
1747 }
1748
1749 void
1750 tidhash_add(struct thread *td)
1751 {
1752         rw_wlock(TIDHASHLOCK(td->td_tid));
1753         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1754         rw_wunlock(TIDHASHLOCK(td->td_tid));
1755 }
1756
1757 void
1758 tidhash_remove(struct thread *td)
1759 {
1760
1761         rw_wlock(TIDHASHLOCK(td->td_tid));
1762         LIST_REMOVE(td, td_hash);
1763         rw_wunlock(TIDHASHLOCK(td->td_tid));
1764 }