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/rangelock.h>
  44 #include <sys/resourcevar.h>
  45 #include <sys/sdt.h>
  46 #include <sys/smp.h>
  47 #include <sys/sched.h>
  48 #include <sys/sleepqueue.h>
  49 #include <sys/selinfo.h>
  50 #include <sys/syscallsubr.h>
  51 #include <sys/sysent.h>
  52 #include <sys/turnstile.h>
  53 #include <sys/ktr.h>
  54 #include <sys/rwlock.h>
  55 #include <sys/umtx.h>
  56 #include <sys/vmmeter.h>
  57 #include <sys/cpuset.h>
  58 #ifdef  HWPMC_HOOKS
  59 #include <sys/pmckern.h>
  60 #endif
  61
  62 #include <security/audit/audit.h>
  63
  64 #include <vm/vm.h>
  65 #include <vm/vm_extern.h>
  66 #include <vm/uma.h>
  67 #include <sys/eventhandler.h>
  68
  69 /*
  70  * Asserts below verify the stability of struct thread and struct proc
  71  * layout, as exposed by KBI to modules.  On head, the KBI is allowed
  72  * to drift, change to the structures must be accompanied by the
  73  * assert update.
  74  *
  75  * On the stable branches after KBI freeze, conditions must not be
  76  * violated.  Typically new fields are moved to the end of the
  77  * structures.
  78  */
  79 #ifdef __amd64__
  80 _Static_assert(offsetof(struct thread, td_flags) == 0xfc,
  81     "struct thread KBI td_flags");
  82 _Static_assert(offsetof(struct thread, td_pflags) == 0x104,
  83     "struct thread KBI td_pflags");
  84 _Static_assert(offsetof(struct thread, td_frame) == 0x470,
  85     "struct thread KBI td_frame");
  86 _Static_assert(offsetof(struct thread, td_emuldata) == 0x518,
  87     "struct thread KBI td_emuldata");
  88 _Static_assert(offsetof(struct proc, p_flag) == 0xb0,
  89     "struct proc KBI p_flag");
  90 _Static_assert(offsetof(struct proc, p_pid) == 0xbc,
  91     "struct proc KBI p_pid");
  92 _Static_assert(offsetof(struct proc, p_filemon) == 0x3d0,
  93     "struct proc KBI p_filemon");
  94 _Static_assert(offsetof(struct proc, p_comm) == 0x3e4,
  95     "struct proc KBI p_comm");
  96 _Static_assert(offsetof(struct proc, p_emuldata) == 0x4b8,
  97     "struct proc KBI p_emuldata");
  98 #endif
  99 #ifdef __i386__
 100 _Static_assert(offsetof(struct thread, td_flags) == 0x98,
 101     "struct thread KBI td_flags");
 102 _Static_assert(offsetof(struct thread, td_pflags) == 0xa0,
 103     "struct thread KBI td_pflags");
 104 _Static_assert(offsetof(struct thread, td_frame) == 0x2e8,
 105     "struct thread KBI td_frame");
 106 _Static_assert(offsetof(struct thread, td_emuldata) == 0x334,
 107     "struct thread KBI td_emuldata");
 108 _Static_assert(offsetof(struct proc, p_flag) == 0x68,
 109     "struct proc KBI p_flag");
 110 _Static_assert(offsetof(struct proc, p_pid) == 0x74,
 111     "struct proc KBI p_pid");
 112 _Static_assert(offsetof(struct proc, p_filemon) == 0x27c,
 113     "struct proc KBI p_filemon");
 114 _Static_assert(offsetof(struct proc, p_comm) == 0x28c,
 115     "struct proc KBI p_comm");
 116 _Static_assert(offsetof(struct proc, p_emuldata) == 0x318,
 117     "struct proc KBI p_emuldata");
 118 #endif
 119
 120 SDT_PROVIDER_DECLARE(proc);
 121 SDT_PROBE_DEFINE(proc, , , lwp__exit);
 122
 123 /*
 124  * thread related storage.
 125  */
 126 static uma_zone_t thread_zone;
 127
 128 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
 129 static struct mtx zombie_lock;
 130 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN);
 131
 132 static void thread_zombie(struct thread *);
 133 static int thread_unsuspend_one(struct thread *td, struct proc *p,
 134     bool boundary);
 135
 136 #define TID_BUFFER_SIZE 1024
 137
 138 struct mtx tid_lock;
 139 static struct unrhdr *tid_unrhdr;
 140 static lwpid_t tid_buffer[TID_BUFFER_SIZE];
 141 static int tid_head, tid_tail;
 142 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
 143
 144 struct  tidhashhead *tidhashtbl;
 145 u_long  tidhash;
 146 struct  rwlock tidhash_lock;
 147
 148 EVENTHANDLER_LIST_DEFINE(thread_ctor);
 149 EVENTHANDLER_LIST_DEFINE(thread_dtor);
 150 EVENTHANDLER_LIST_DEFINE(thread_init);
 151 EVENTHANDLER_LIST_DEFINE(thread_fini);
 152
 153 static lwpid_t
 154 tid_alloc(void)
 155 {
 156         lwpid_t tid;
 157
 158         tid = alloc_unr(tid_unrhdr);
 159         if (tid != -1)
 160                 return (tid);
 161         mtx_lock(&tid_lock);
 162         if (tid_head == tid_tail) {
 163                 mtx_unlock(&tid_lock);
 164                 return (-1);
 165         }
 166         tid = tid_buffer[tid_head];
 167         tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
 168         mtx_unlock(&tid_lock);
 169         return (tid);
 170 }
 171
 172 static void
 173 tid_free(lwpid_t tid)
 174 {
 175         lwpid_t tmp_tid = -1;
 176
 177         mtx_lock(&tid_lock);
 178         if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
 179                 tmp_tid = tid_buffer[tid_head];
 180                 tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
 181         }
 182         tid_buffer[tid_tail] = tid;
 183         tid_tail = (tid_tail + 1) % TID_BUFFER_SIZE;
 184         mtx_unlock(&tid_lock);
 185         if (tmp_tid != -1)
 186                 free_unr(tid_unrhdr, tmp_tid);
 187 }
 188
 189 /*
 190  * Prepare a thread for use.
 191  */
 192 static int
 193 thread_ctor(void *mem, int size, void *arg, int flags)
 194 {
 195         struct thread   *td;
 196
 197         td = (struct thread *)mem;
 198         td->td_state = TDS_INACTIVE;
 199         td->td_oncpu = NOCPU;
 200
 201         td->td_tid = tid_alloc();
 202
 203         /*
 204          * Note that td_critnest begins life as 1 because the thread is not
 205          * running and is thereby implicitly waiting to be on the receiving
 206          * end of a context switch.
 207          */
 208         td->td_critnest = 1;
 209         td->td_lend_user_pri = PRI_MAX;
 210         EVENTHANDLER_DIRECT_INVOKE(thread_ctor, td);
 211 #ifdef AUDIT
 212         audit_thread_alloc(td);
 213 #endif
 214         umtx_thread_alloc(td);
 215         return (0);
 216 }
 217
 218 /*
 219  * Reclaim a thread after use.
 220  */
 221 static void
 222 thread_dtor(void *mem, int size, void *arg)
 223 {
 224         struct thread *td;
 225
 226         td = (struct thread *)mem;
 227
 228 #ifdef INVARIANTS
 229         /* Verify that this thread is in a safe state to free. */
 230         switch (td->td_state) {
 231         case TDS_INHIBITED:
 232         case TDS_RUNNING:
 233         case TDS_CAN_RUN:
 234         case TDS_RUNQ:
 235                 /*
 236                  * We must never unlink a thread that is in one of
 237                  * these states, because it is currently active.
 238                  */
 239                 panic("bad state for thread unlinking");
 240                 /* NOTREACHED */
 241         case TDS_INACTIVE:
 242                 break;
 243         default:
 244                 panic("bad thread state");
 245                 /* NOTREACHED */
 246         }
 247 #endif
 248 #ifdef AUDIT
 249         audit_thread_free(td);
 250 #endif
 251         /* Free all OSD associated to this thread. */
 252         osd_thread_exit(td);
 253         td_softdep_cleanup(td);
 254         MPASS(td->td_su == NULL);
 255
 256         EVENTHANDLER_DIRECT_INVOKE(thread_dtor, td);
 257         tid_free(td->td_tid);
 258 }
 259
 260 /*
 261  * Initialize type-stable parts of a thread (when newly created).
 262  */
 263 static int
 264 thread_init(void *mem, int size, int flags)
 265 {
 266         struct thread *td;
 267
 268         td = (struct thread *)mem;
 269
 270         td->td_sleepqueue = sleepq_alloc();
 271         td->td_turnstile = turnstile_alloc();
 272         td->td_rlqe = NULL;
 273         EVENTHANDLER_DIRECT_INVOKE(thread_init, td);
 274         umtx_thread_init(td);
 275         td->td_kstack = 0;
 276         td->td_sel = NULL;
 277         return (0);
 278 }
 279
 280 /*
 281  * Tear down type-stable parts of a thread (just before being discarded).
 282  */
 283 static void
 284 thread_fini(void *mem, int size)
 285 {
 286         struct thread *td;
 287
 288         td = (struct thread *)mem;
 289         EVENTHANDLER_DIRECT_INVOKE(thread_fini, td);
 290         rlqentry_free(td->td_rlqe);
 291         turnstile_free(td->td_turnstile);
 292         sleepq_free(td->td_sleepqueue);
 293         umtx_thread_fini(td);
 294         seltdfini(td);
 295 }
 296
 297 /*
 298  * For a newly created process,
 299  * link up all the structures and its initial threads etc.
 300  * called from:
 301  * {arch}/{arch}/machdep.c   {arch}_init(), init386() etc.
 302  * proc_dtor() (should go away)
 303  * proc_init()
 304  */
 305 void
 306 proc_linkup0(struct proc *p, struct thread *td)
 307 {
 308         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
 309         proc_linkup(p, td);
 310 }
 311
 312 void
 313 proc_linkup(struct proc *p, struct thread *td)
 314 {
 315
 316         sigqueue_init(&p->p_sigqueue, p);
 317         p->p_ksi = ksiginfo_alloc(1);
 318         if (p->p_ksi != NULL) {
 319                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
 320                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
 321         }
 322         LIST_INIT(&p->p_mqnotifier);
 323         p->p_numthreads = 0;
 324         thread_link(td, p);
 325 }
 326
 327 /*
 328  * Initialize global thread allocation resources.
 329  */
 330 void
 331 threadinit(void)
 332 {
 333
 334         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
 335
 336         /*
 337          * pid_max cannot be greater than PID_MAX.
 338          * leave one number for thread0.
 339          */
 340         tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
 341
 342         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
 343             thread_ctor, thread_dtor, thread_init, thread_fini,
 344             32 - 1, UMA_ZONE_NOFREE);
 345         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
 346         rw_init(&tidhash_lock, "tidhash");
 347 }
 348
 349 /*
 350  * Place an unused thread on the zombie list.
 351  * Use the slpq as that must be unused by now.
 352  */
 353 void
 354 thread_zombie(struct thread *td)
 355 {
 356         mtx_lock_spin(&zombie_lock);
 357         TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
 358         mtx_unlock_spin(&zombie_lock);
 359 }
 360
 361 /*
 362  * Release a thread that has exited after cpu_throw().
 363  */
 364 void
 365 thread_stash(struct thread *td)
 366 {
 367         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
 368         thread_zombie(td);
 369 }
 370
 371 /*
 372  * Reap zombie resources.
 373  */
 374 void
 375 thread_reap(void)
 376 {
 377         struct thread *td_first, *td_next;
 378
 379         /*
 380          * Don't even bother to lock if none at this instant,
 381          * we really don't care about the next instant.
 382          */
 383         if (!TAILQ_EMPTY(&zombie_threads)) {
 384                 mtx_lock_spin(&zombie_lock);
 385                 td_first = TAILQ_FIRST(&zombie_threads);
 386                 if (td_first)
 387                         TAILQ_INIT(&zombie_threads);
 388                 mtx_unlock_spin(&zombie_lock);
 389                 while (td_first) {
 390                         td_next = TAILQ_NEXT(td_first, td_slpq);
 391                         thread_cow_free(td_first);
 392                         thread_free(td_first);
 393                         td_first = td_next;
 394                 }
 395         }
 396 }
 397
 398 /*
 399  * Allocate a thread.
 400  */
 401 struct thread *
 402 thread_alloc(int pages)
 403 {
 404         struct thread *td;
 405
 406         thread_reap(); /* check if any zombies to get */
 407
 408         td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
 409         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
 410         if (!vm_thread_new(td, pages)) {
 411                 uma_zfree(thread_zone, td);
 412                 return (NULL);
 413         }
 414         cpu_thread_alloc(td);
 415         return (td);
 416 }
 417
 418 int
 419 thread_alloc_stack(struct thread *td, int pages)
 420 {
 421
 422         KASSERT(td->td_kstack == 0,
 423             ("thread_alloc_stack called on a thread with kstack"));
 424         if (!vm_thread_new(td, pages))
 425                 return (0);
 426         cpu_thread_alloc(td);
 427         return (1);
 428 }
 429
 430 /*
 431  * Deallocate a thread.
 432  */
 433 void
 434 thread_free(struct thread *td)
 435 {
 436
 437         lock_profile_thread_exit(td);
 438         if (td->td_cpuset)
 439                 cpuset_rel(td->td_cpuset);
 440         td->td_cpuset = NULL;
 441         cpu_thread_free(td);
 442         if (td->td_kstack != 0)
 443                 vm_thread_dispose(td);
 444         callout_drain(&td->td_slpcallout);
 445         uma_zfree(thread_zone, td);
 446 }
 447
 448 void
 449 thread_cow_get_proc(struct thread *newtd, struct proc *p)
 450 {
 451
 452         PROC_LOCK_ASSERT(p, MA_OWNED);
 453         newtd->td_ucred = crhold(p->p_ucred);
 454         newtd->td_limit = lim_hold(p->p_limit);
 455         newtd->td_cowgen = p->p_cowgen;
 456 }
 457
 458 void
 459 thread_cow_get(struct thread *newtd, struct thread *td)
 460 {
 461
 462         newtd->td_ucred = crhold(td->td_ucred);
 463         newtd->td_limit = lim_hold(td->td_limit);
 464         newtd->td_cowgen = td->td_cowgen;
 465 }
 466
 467 void
 468 thread_cow_free(struct thread *td)
 469 {
 470
 471         if (td->td_ucred != NULL)
 472                 crfree(td->td_ucred);
 473         if (td->td_limit != NULL)
 474                 lim_free(td->td_limit);
 475 }
 476
 477 void
 478 thread_cow_update(struct thread *td)
 479 {
 480         struct proc *p;
 481         struct ucred *oldcred;
 482         struct plimit *oldlimit;
 483
 484         p = td->td_proc;
 485         oldcred = NULL;
 486         oldlimit = NULL;
 487         PROC_LOCK(p);
 488         if (td->td_ucred != p->p_ucred) {
 489                 oldcred = td->td_ucred;
 490                 td->td_ucred = crhold(p->p_ucred);
 491         }
 492         if (td->td_limit != p->p_limit) {
 493                 oldlimit = td->td_limit;
 494                 td->td_limit = lim_hold(p->p_limit);
 495         }
 496         td->td_cowgen = p->p_cowgen;
 497         PROC_UNLOCK(p);
 498         if (oldcred != NULL)
 499                 crfree(oldcred);
 500         if (oldlimit != NULL)
 501                 lim_free(oldlimit);
 502 }
 503
 504 /*
 505  * Discard the current thread and exit from its context.
 506  * Always called with scheduler locked.
 507  *
 508  * Because we can't free a thread while we're operating under its context,
 509  * push the current thread into our CPU's deadthread holder. This means
 510  * we needn't worry about someone else grabbing our context before we
 511  * do a cpu_throw().
 512  */
 513 void
 514 thread_exit(void)
 515 {
 516         uint64_t runtime, new_switchtime;
 517         struct thread *td;
 518         struct thread *td2;
 519         struct proc *p;
 520         int wakeup_swapper;
 521
 522         td = curthread;
 523         p = td->td_proc;
 524
 525         PROC_SLOCK_ASSERT(p, MA_OWNED);
 526         mtx_assert(&Giant, MA_NOTOWNED);
 527
 528         PROC_LOCK_ASSERT(p, MA_OWNED);
 529         KASSERT(p != NULL, ("thread exiting without a process"));
 530         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
 531             (long)p->p_pid, td->td_name);
 532         SDT_PROBE0(proc, , , lwp__exit);
 533         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
 534
 535 #ifdef AUDIT
 536         AUDIT_SYSCALL_EXIT(0, td);
 537 #endif
 538         /*
 539          * drop FPU & debug register state storage, or any other
 540          * architecture specific resources that
 541          * would not be on a new untouched process.
 542          */
 543         cpu_thread_exit(td);
 544
 545         /*
 546          * The last thread is left attached to the process
 547          * So that the whole bundle gets recycled. Skip
 548          * all this stuff if we never had threads.
 549          * EXIT clears all sign of other threads when
 550          * it goes to single threading, so the last thread always
 551          * takes the short path.
 552          */
 553         if (p->p_flag & P_HADTHREADS) {
 554                 if (p->p_numthreads > 1) {
 555                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
 556                         thread_unlink(td);
 557                         td2 = FIRST_THREAD_IN_PROC(p);
 558                         sched_exit_thread(td2, td);
 559
 560                         /*
 561                          * The test below is NOT true if we are the
 562                          * sole exiting thread. P_STOPPED_SINGLE is unset
 563                          * in exit1() after it is the only survivor.
 564                          */
 565                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 566                                 if (p->p_numthreads == p->p_suspcount) {
 567                                         thread_lock(p->p_singlethread);
 568                                         wakeup_swapper = thread_unsuspend_one(
 569                                                 p->p_singlethread, p, false);
 570                                         thread_unlock(p->p_singlethread);
 571                                         if (wakeup_swapper)
 572                                                 kick_proc0();
 573                                 }
 574                         }
 575
 576                         PCPU_SET(deadthread, td);
 577                 } else {
 578                         /*
 579                          * The last thread is exiting.. but not through exit()
 580                          */
 581                         panic ("thread_exit: Last thread exiting on its own");
 582                 }
 583         }
 584 #ifdef  HWPMC_HOOKS
 585         /*
 586          * If this thread is part of a process that is being tracked by hwpmc(4),
 587          * inform the module of the thread's impending exit.
 588          */
 589         if (PMC_PROC_IS_USING_PMCS(td->td_proc)) {
 590                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 591                 PMC_CALL_HOOK_UNLOCKED(td, PMC_FN_THR_EXIT, NULL);
 592         }
 593 #endif
 594         PROC_UNLOCK(p);
 595         PROC_STATLOCK(p);
 596         thread_lock(td);
 597         PROC_SUNLOCK(p);
 598
 599         /* Do the same timestamp bookkeeping that mi_switch() would do. */
 600         new_switchtime = cpu_ticks();
 601         runtime = new_switchtime - PCPU_GET(switchtime);
 602         td->td_runtime += runtime;
 603         td->td_incruntime += runtime;
 604         PCPU_SET(switchtime, new_switchtime);
 605         PCPU_SET(switchticks, ticks);
 606         VM_CNT_INC(v_swtch);
 607
 608         /* Save our resource usage in our process. */
 609         td->td_ru.ru_nvcsw++;
 610         ruxagg(p, td);
 611         rucollect(&p->p_ru, &td->td_ru);
 612         PROC_STATUNLOCK(p);
 613
 614         td->td_state = TDS_INACTIVE;
 615 #ifdef WITNESS
 616         witness_thread_exit(td);
 617 #endif
 618         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
 619         sched_throw(td);
 620         panic("I'm a teapot!");
 621         /* NOTREACHED */
 622 }
 623
 624 /*
 625  * Do any thread specific cleanups that may be needed in wait()
 626  * called with Giant, proc and schedlock not held.
 627  */
 628 void
 629 thread_wait(struct proc *p)
 630 {
 631         struct thread *td;
 632
 633         mtx_assert(&Giant, MA_NOTOWNED);
 634         KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()"));
 635         KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking"));
 636         td = FIRST_THREAD_IN_PROC(p);
 637         /* Lock the last thread so we spin until it exits cpu_throw(). */
 638         thread_lock(td);
 639         thread_unlock(td);
 640         lock_profile_thread_exit(td);
 641         cpuset_rel(td->td_cpuset);
 642         td->td_cpuset = NULL;
 643         cpu_thread_clean(td);
 644         thread_cow_free(td);
 645         callout_drain(&td->td_slpcallout);
 646         thread_reap();  /* check for zombie threads etc. */
 647 }
 648
 649 /*
 650  * Link a thread to a process.
 651  * set up anything that needs to be initialized for it to
 652  * be used by the process.
 653  */
 654 void
 655 thread_link(struct thread *td, struct proc *p)
 656 {
 657
 658         /*
 659          * XXX This can't be enabled because it's called for proc0 before
 660          * its lock has been created.
 661          * PROC_LOCK_ASSERT(p, MA_OWNED);
 662          */
 663         td->td_state    = TDS_INACTIVE;
 664         td->td_proc     = p;
 665         td->td_flags    = TDF_INMEM;
 666
 667         LIST_INIT(&td->td_contested);
 668         LIST_INIT(&td->td_lprof[0]);
 669         LIST_INIT(&td->td_lprof[1]);
 670         sigqueue_init(&td->td_sigqueue, p);
 671         callout_init(&td->td_slpcallout, 1);
 672         TAILQ_INSERT_TAIL(&p->p_threads, td, td_plist);
 673         p->p_numthreads++;
 674 }
 675
 676 /*
 677  * Called from:
 678  *  thread_exit()
 679  */
 680 void
 681 thread_unlink(struct thread *td)
 682 {
 683         struct proc *p = td->td_proc;
 684
 685         PROC_LOCK_ASSERT(p, MA_OWNED);
 686         TAILQ_REMOVE(&p->p_threads, td, td_plist);
 687         p->p_numthreads--;
 688         /* could clear a few other things here */
 689         /* Must  NOT clear links to proc! */
 690 }
 691
 692 static int
 693 calc_remaining(struct proc *p, int mode)
 694 {
 695         int remaining;
 696
 697         PROC_LOCK_ASSERT(p, MA_OWNED);
 698         PROC_SLOCK_ASSERT(p, MA_OWNED);
 699         if (mode == SINGLE_EXIT)
 700                 remaining = p->p_numthreads;
 701         else if (mode == SINGLE_BOUNDARY)
 702                 remaining = p->p_numthreads - p->p_boundary_count;
 703         else if (mode == SINGLE_NO_EXIT || mode == SINGLE_ALLPROC)
 704                 remaining = p->p_numthreads - p->p_suspcount;
 705         else
 706                 panic("calc_remaining: wrong mode %d", mode);
 707         return (remaining);
 708 }
 709
 710 static int
 711 remain_for_mode(int mode)
 712 {
 713
 714         return (mode == SINGLE_ALLPROC ? 0 : 1);
 715 }
 716
 717 static int
 718 weed_inhib(int mode, struct thread *td2, struct proc *p)
 719 {
 720         int wakeup_swapper;
 721
 722         PROC_LOCK_ASSERT(p, MA_OWNED);
 723         PROC_SLOCK_ASSERT(p, MA_OWNED);
 724         THREAD_LOCK_ASSERT(td2, MA_OWNED);
 725
 726         wakeup_swapper = 0;
 727         switch (mode) {
 728         case SINGLE_EXIT:
 729                 if (TD_IS_SUSPENDED(td2))
 730                         wakeup_swapper |= thread_unsuspend_one(td2, p, true);
 731                 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
 732                         wakeup_swapper |= sleepq_abort(td2, EINTR);
 733                 break;
 734         case SINGLE_BOUNDARY:
 735         case SINGLE_NO_EXIT:
 736                 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & TDF_BOUNDARY) == 0)
 737                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
 738                 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0)
 739                         wakeup_swapper |= sleepq_abort(td2, ERESTART);
 740                 break;
 741         case SINGLE_ALLPROC:
 742                 /*
 743                  * ALLPROC suspend tries to avoid spurious EINTR for
 744                  * threads sleeping interruptable, by suspending the
 745                  * thread directly, similarly to sig_suspend_threads().
 746                  * Since such sleep is not performed at the user
 747                  * boundary, TDF_BOUNDARY flag is not set, and TDF_ALLPROCSUSP
 748                  * is used to avoid immediate un-suspend.
 749                  */
 750                 if (TD_IS_SUSPENDED(td2) && (td2->td_flags & (TDF_BOUNDARY |
 751                     TDF_ALLPROCSUSP)) == 0)
 752                         wakeup_swapper |= thread_unsuspend_one(td2, p, false);
 753                 if (TD_ON_SLEEPQ(td2) && (td2->td_flags & TDF_SINTR) != 0) {
 754                         if ((td2->td_flags & TDF_SBDRY) == 0) {
 755                                 thread_suspend_one(td2);
 756                                 td2->td_flags |= TDF_ALLPROCSUSP;
 757                         } else {
 758                                 wakeup_swapper |= sleepq_abort(td2, ERESTART);
 759                         }
 760                 }
 761                 break;
 762         }
 763         return (wakeup_swapper);
 764 }
 765
 766 /*
 767  * Enforce single-threading.
 768  *
 769  * Returns 1 if the caller must abort (another thread is waiting to
 770  * exit the process or similar). Process is locked!
 771  * Returns 0 when you are successfully the only thread running.
 772  * A process has successfully single threaded in the suspend mode when
 773  * There are no threads in user mode. Threads in the kernel must be
 774  * allowed to continue until they get to the user boundary. They may even
 775  * copy out their return values and data before suspending. They may however be
 776  * accelerated in reaching the user boundary as we will wake up
 777  * any sleeping threads that are interruptable. (PCATCH).
 778  */
 779 int
 780 thread_single(struct proc *p, int mode)
 781 {
 782         struct thread *td;
 783         struct thread *td2;
 784         int remaining, wakeup_swapper;
 785
 786         td = curthread;
 787         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
 788             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
 789             ("invalid mode %d", mode));
 790         /*
 791          * If allowing non-ALLPROC singlethreading for non-curproc
 792          * callers, calc_remaining() and remain_for_mode() should be
 793          * adjusted to also account for td->td_proc != p.  For now
 794          * this is not implemented because it is not used.
 795          */
 796         KASSERT((mode == SINGLE_ALLPROC && td->td_proc != p) ||
 797             (mode != SINGLE_ALLPROC && td->td_proc == p),
 798             ("mode %d proc %p curproc %p", mode, p, td->td_proc));
 799         mtx_assert(&Giant, MA_NOTOWNED);
 800         PROC_LOCK_ASSERT(p, MA_OWNED);
 801
 802         if ((p->p_flag & P_HADTHREADS) == 0 && mode != SINGLE_ALLPROC)
 803                 return (0);
 804
 805         /* Is someone already single threading? */
 806         if (p->p_singlethread != NULL && p->p_singlethread != td)
 807                 return (1);
 808
 809         if (mode == SINGLE_EXIT) {
 810                 p->p_flag |= P_SINGLE_EXIT;
 811                 p->p_flag &= ~P_SINGLE_BOUNDARY;
 812         } else {
 813                 p->p_flag &= ~P_SINGLE_EXIT;
 814                 if (mode == SINGLE_BOUNDARY)
 815                         p->p_flag |= P_SINGLE_BOUNDARY;
 816                 else
 817                         p->p_flag &= ~P_SINGLE_BOUNDARY;
 818         }
 819         if (mode == SINGLE_ALLPROC)
 820                 p->p_flag |= P_TOTAL_STOP;
 821         p->p_flag |= P_STOPPED_SINGLE;
 822         PROC_SLOCK(p);
 823         p->p_singlethread = td;
 824         remaining = calc_remaining(p, mode);
 825         while (remaining != remain_for_mode(mode)) {
 826                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
 827                         goto stopme;
 828                 wakeup_swapper = 0;
 829                 FOREACH_THREAD_IN_PROC(p, td2) {
 830                         if (td2 == td)
 831                                 continue;
 832                         thread_lock(td2);
 833                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
 834                         if (TD_IS_INHIBITED(td2)) {
 835                                 wakeup_swapper |= weed_inhib(mode, td2, p);
 836 #ifdef SMP
 837                         } else if (TD_IS_RUNNING(td2) && td != td2) {
 838                                 forward_signal(td2);
 839 #endif
 840                         }
 841                         thread_unlock(td2);
 842                 }
 843                 if (wakeup_swapper)
 844                         kick_proc0();
 845                 remaining = calc_remaining(p, mode);
 846
 847                 /*
 848                  * Maybe we suspended some threads.. was it enough?
 849                  */
 850                 if (remaining == remain_for_mode(mode))
 851                         break;
 852
 853 stopme:
 854                 /*
 855                  * Wake us up when everyone else has suspended.
 856                  * In the mean time we suspend as well.
 857                  */
 858                 thread_suspend_switch(td, p);
 859                 remaining = calc_remaining(p, mode);
 860         }
 861         if (mode == SINGLE_EXIT) {
 862                 /*
 863                  * Convert the process to an unthreaded process.  The
 864                  * SINGLE_EXIT is called by exit1() or execve(), in
 865                  * both cases other threads must be retired.
 866                  */
 867                 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads"));
 868                 p->p_singlethread = NULL;
 869                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS);
 870
 871                 /*
 872                  * Wait for any remaining threads to exit cpu_throw().
 873                  */
 874                 while (p->p_exitthreads != 0) {
 875                         PROC_SUNLOCK(p);
 876                         PROC_UNLOCK(p);
 877                         sched_relinquish(td);
 878                         PROC_LOCK(p);
 879                         PROC_SLOCK(p);
 880                 }
 881         } else if (mode == SINGLE_BOUNDARY) {
 882                 /*
 883                  * Wait until all suspended threads are removed from
 884                  * the processors.  The thread_suspend_check()
 885                  * increments p_boundary_count while it is still
 886                  * running, which makes it possible for the execve()
 887                  * to destroy vmspace while our other threads are
 888                  * still using the address space.
 889                  *
 890                  * We lock the thread, which is only allowed to
 891                  * succeed after context switch code finished using
 892                  * the address space.
 893                  */
 894                 FOREACH_THREAD_IN_PROC(p, td2) {
 895                         if (td2 == td)
 896                                 continue;
 897                         thread_lock(td2);
 898                         KASSERT((td2->td_flags & TDF_BOUNDARY) != 0,
 899                             ("td %p not on boundary", td2));
 900                         KASSERT(TD_IS_SUSPENDED(td2),
 901                             ("td %p is not suspended", td2));
 902                         thread_unlock(td2);
 903                 }
 904         }
 905         PROC_SUNLOCK(p);
 906         return (0);
 907 }
 908
 909 bool
 910 thread_suspend_check_needed(void)
 911 {
 912         struct proc *p;
 913         struct thread *td;
 914
 915         td = curthread;
 916         p = td->td_proc;
 917         PROC_LOCK_ASSERT(p, MA_OWNED);
 918         return (P_SHOULDSTOP(p) || ((p->p_flag & P_TRACED) != 0 &&
 919             (td->td_dbgflags & TDB_SUSPEND) != 0));
 920 }
 921
 922 /*
 923  * Called in from locations that can safely check to see
 924  * whether we have to suspend or at least throttle for a
 925  * single-thread event (e.g. fork).
 926  *
 927  * Such locations include userret().
 928  * If the "return_instead" argument is non zero, the thread must be able to
 929  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
 930  *
 931  * The 'return_instead' argument tells the function if it may do a
 932  * thread_exit() or suspend, or whether the caller must abort and back
 933  * out instead.
 934  *
 935  * If the thread that set the single_threading request has set the
 936  * P_SINGLE_EXIT bit in the process flags then this call will never return
 937  * if 'return_instead' is false, but will exit.
 938  *
 939  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
 940  *---------------+--------------------+---------------------
 941  *       0       | returns 0          |   returns 0 or 1
 942  *               | when ST ends       |   immediately
 943  *---------------+--------------------+---------------------
 944  *       1       | thread exits       |   returns 1
 945  *               |                    |  immediately
 946  * 0 = thread_exit() or suspension ok,
 947  * other = return error instead of stopping the thread.
 948  *
 949  * While a full suspension is under effect, even a single threading
 950  * thread would be suspended if it made this call (but it shouldn't).
 951  * This call should only be made from places where
 952  * thread_exit() would be safe as that may be the outcome unless
 953  * return_instead is set.
 954  */
 955 int
 956 thread_suspend_check(int return_instead)
 957 {
 958         struct thread *td;
 959         struct proc *p;
 960         int wakeup_swapper;
 961
 962         td = curthread;
 963         p = td->td_proc;
 964         mtx_assert(&Giant, MA_NOTOWNED);
 965         PROC_LOCK_ASSERT(p, MA_OWNED);
 966         while (thread_suspend_check_needed()) {
 967                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 968                         KASSERT(p->p_singlethread != NULL,
 969                             ("singlethread not set"));
 970                         /*
 971                          * The only suspension in action is a
 972                          * single-threading. Single threader need not stop.
 973                          * It is safe to access p->p_singlethread unlocked
 974                          * because it can only be set to our address by us.
 975                          */
 976                         if (p->p_singlethread == td)
 977                                 return (0);     /* Exempt from stopping. */
 978                 }
 979                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
 980                         return (EINTR);
 981
 982                 /* Should we goto user boundary if we didn't come from there? */
 983                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
 984                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
 985                         return (ERESTART);
 986
 987                 /*
 988                  * Ignore suspend requests if they are deferred.
 989                  */
 990                 if ((td->td_flags & TDF_SBDRY) != 0) {
 991                         KASSERT(return_instead,
 992                             ("TDF_SBDRY set for unsafe thread_suspend_check"));
 993                         KASSERT((td->td_flags & (TDF_SEINTR | TDF_SERESTART)) !=
 994                             (TDF_SEINTR | TDF_SERESTART),
 995                             ("both TDF_SEINTR and TDF_SERESTART"));
 996                         return (TD_SBDRY_INTR(td) ? TD_SBDRY_ERRNO(td) : 0);
 997                 }
 998
 999                 /*
1000                  * If the process is waiting for us to exit,
1001                  * this thread should just suicide.
1002                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
1003                  */
1004                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
1005                         PROC_UNLOCK(p);
1006
1007                         /*
1008                          * Allow Linux emulation layer to do some work
1009                          * before thread suicide.
1010                          */
1011                         if (__predict_false(p->p_sysent->sv_thread_detach != NULL))
1012                                 (p->p_sysent->sv_thread_detach)(td);
1013                         umtx_thread_exit(td);
1014                         kern_thr_exit(td);
1015                         panic("stopped thread did not exit");
1016                 }
1017
1018                 PROC_SLOCK(p);
1019                 thread_stopped(p);
1020                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
1021                         if (p->p_numthreads == p->p_suspcount + 1) {
1022                                 thread_lock(p->p_singlethread);
1023                                 wakeup_swapper = thread_unsuspend_one(
1024                                     p->p_singlethread, p, false);
1025                                 thread_unlock(p->p_singlethread);
1026                                 if (wakeup_swapper)
1027                                         kick_proc0();
1028                         }
1029                 }
1030                 PROC_UNLOCK(p);
1031                 thread_lock(td);
1032                 /*
1033                  * When a thread suspends, it just
1034                  * gets taken off all queues.
1035                  */
1036                 thread_suspend_one(td);
1037                 if (return_instead == 0) {
1038                         p->p_boundary_count++;
1039                         td->td_flags |= TDF_BOUNDARY;
1040                 }
1041                 PROC_SUNLOCK(p);
1042                 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
1043                 thread_unlock(td);
1044                 PROC_LOCK(p);
1045         }
1046         return (0);
1047 }
1048
1049 void
1050 thread_suspend_switch(struct thread *td, struct proc *p)
1051 {
1052
1053         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1054         PROC_LOCK_ASSERT(p, MA_OWNED);
1055         PROC_SLOCK_ASSERT(p, MA_OWNED);
1056         /*
1057          * We implement thread_suspend_one in stages here to avoid
1058          * dropping the proc lock while the thread lock is owned.
1059          */
1060         if (p == td->td_proc) {
1061                 thread_stopped(p);
1062                 p->p_suspcount++;
1063         }
1064         PROC_UNLOCK(p);
1065         thread_lock(td);
1066         td->td_flags &= ~TDF_NEEDSUSPCHK;
1067         TD_SET_SUSPENDED(td);
1068         sched_sleep(td, 0);
1069         PROC_SUNLOCK(p);
1070         DROP_GIANT();
1071         mi_switch(SW_VOL | SWT_SUSPEND, NULL);
1072         thread_unlock(td);
1073         PICKUP_GIANT();
1074         PROC_LOCK(p);
1075         PROC_SLOCK(p);
1076 }
1077
1078 void
1079 thread_suspend_one(struct thread *td)
1080 {
1081         struct proc *p;
1082
1083         p = td->td_proc;
1084         PROC_SLOCK_ASSERT(p, MA_OWNED);
1085         THREAD_LOCK_ASSERT(td, MA_OWNED);
1086         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
1087         p->p_suspcount++;
1088         td->td_flags &= ~TDF_NEEDSUSPCHK;
1089         TD_SET_SUSPENDED(td);
1090         sched_sleep(td, 0);
1091 }
1092
1093 static int
1094 thread_unsuspend_one(struct thread *td, struct proc *p, bool boundary)
1095 {
1096
1097         THREAD_LOCK_ASSERT(td, MA_OWNED);
1098         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
1099         TD_CLR_SUSPENDED(td);
1100         td->td_flags &= ~TDF_ALLPROCSUSP;
1101         if (td->td_proc == p) {
1102                 PROC_SLOCK_ASSERT(p, MA_OWNED);
1103                 p->p_suspcount--;
1104                 if (boundary && (td->td_flags & TDF_BOUNDARY) != 0) {
1105                         td->td_flags &= ~TDF_BOUNDARY;
1106                         p->p_boundary_count--;
1107                 }
1108         }
1109         return (setrunnable(td));
1110 }
1111
1112 /*
1113  * Allow all threads blocked by single threading to continue running.
1114  */
1115 void
1116 thread_unsuspend(struct proc *p)
1117 {
1118         struct thread *td;
1119         int wakeup_swapper;
1120
1121         PROC_LOCK_ASSERT(p, MA_OWNED);
1122         PROC_SLOCK_ASSERT(p, MA_OWNED);
1123         wakeup_swapper = 0;
1124         if (!P_SHOULDSTOP(p)) {
1125                 FOREACH_THREAD_IN_PROC(p, td) {
1126                         thread_lock(td);
1127                         if (TD_IS_SUSPENDED(td)) {
1128                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1129                                     true);
1130                         }
1131                         thread_unlock(td);
1132                 }
1133         } else if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
1134             p->p_numthreads == p->p_suspcount) {
1135                 /*
1136                  * Stopping everything also did the job for the single
1137                  * threading request. Now we've downgraded to single-threaded,
1138                  * let it continue.
1139                  */
1140                 if (p->p_singlethread->td_proc == p) {
1141                         thread_lock(p->p_singlethread);
1142                         wakeup_swapper = thread_unsuspend_one(
1143                             p->p_singlethread, p, false);
1144                         thread_unlock(p->p_singlethread);
1145                 }
1146         }
1147         if (wakeup_swapper)
1148                 kick_proc0();
1149 }
1150
1151 /*
1152  * End the single threading mode..
1153  */
1154 void
1155 thread_single_end(struct proc *p, int mode)
1156 {
1157         struct thread *td;
1158         int wakeup_swapper;
1159
1160         KASSERT(mode == SINGLE_EXIT || mode == SINGLE_BOUNDARY ||
1161             mode == SINGLE_ALLPROC || mode == SINGLE_NO_EXIT,
1162             ("invalid mode %d", mode));
1163         PROC_LOCK_ASSERT(p, MA_OWNED);
1164         KASSERT((mode == SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) != 0) ||
1165             (mode != SINGLE_ALLPROC && (p->p_flag & P_TOTAL_STOP) == 0),
1166             ("mode %d does not match P_TOTAL_STOP", mode));
1167         KASSERT(mode == SINGLE_ALLPROC || p->p_singlethread == curthread,
1168             ("thread_single_end from other thread %p %p",
1169             curthread, p->p_singlethread));
1170         KASSERT(mode != SINGLE_BOUNDARY ||
1171             (p->p_flag & P_SINGLE_BOUNDARY) != 0,
1172             ("mis-matched SINGLE_BOUNDARY flags %x", p->p_flag));
1173         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY |
1174             P_TOTAL_STOP);
1175         PROC_SLOCK(p);
1176         p->p_singlethread = NULL;
1177         wakeup_swapper = 0;
1178         /*
1179          * If there are other threads they may now run,
1180          * unless of course there is a blanket 'stop order'
1181          * on the process. The single threader must be allowed
1182          * to continue however as this is a bad place to stop.
1183          */
1184         if (p->p_numthreads != remain_for_mode(mode) && !P_SHOULDSTOP(p)) {
1185                 FOREACH_THREAD_IN_PROC(p, td) {
1186                         thread_lock(td);
1187                         if (TD_IS_SUSPENDED(td)) {
1188                                 wakeup_swapper |= thread_unsuspend_one(td, p,
1189                                     mode == SINGLE_BOUNDARY);
1190                         }
1191                         thread_unlock(td);
1192                 }
1193         }
1194         KASSERT(mode != SINGLE_BOUNDARY || p->p_boundary_count == 0,
1195             ("inconsistent boundary count %d", p->p_boundary_count));
1196         PROC_SUNLOCK(p);
1197         if (wakeup_swapper)
1198                 kick_proc0();
1199 }
1200
1201 struct thread *
1202 thread_find(struct proc *p, lwpid_t tid)
1203 {
1204         struct thread *td;
1205
1206         PROC_LOCK_ASSERT(p, MA_OWNED);
1207         FOREACH_THREAD_IN_PROC(p, td) {
1208                 if (td->td_tid == tid)
1209                         break;
1210         }
1211         return (td);
1212 }
1213
1214 /* Locate a thread by number; return with proc lock held. */
1215 struct thread *
1216 tdfind(lwpid_t tid, pid_t pid)
1217 {
1218 #define RUN_THRESH      16
1219         struct thread *td;
1220         int run = 0;
1221
1222         rw_rlock(&tidhash_lock);
1223         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
1224                 if (td->td_tid == tid) {
1225                         if (pid != -1 && td->td_proc->p_pid != pid) {
1226                                 td = NULL;
1227                                 break;
1228                         }
1229                         PROC_LOCK(td->td_proc);
1230                         if (td->td_proc->p_state == PRS_NEW) {
1231                                 PROC_UNLOCK(td->td_proc);
1232                                 td = NULL;
1233                                 break;
1234                         }
1235                         if (run > RUN_THRESH) {
1236                                 if (rw_try_upgrade(&tidhash_lock)) {
1237                                         LIST_REMOVE(td, td_hash);
1238                                         LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1239                                                 td, td_hash);
1240                                         rw_wunlock(&tidhash_lock);
1241                                         return (td);
1242                                 }
1243                         }
1244                         break;
1245                 }
1246                 run++;
1247         }
1248         rw_runlock(&tidhash_lock);
1249         return (td);
1250 }
1251
1252 void
1253 tidhash_add(struct thread *td)
1254 {
1255         rw_wlock(&tidhash_lock);
1256         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1257         rw_wunlock(&tidhash_lock);
1258 }
1259
1260 void
1261 tidhash_remove(struct thread *td)
1262 {
1263         rw_wlock(&tidhash_lock);
1264         LIST_REMOVE(td, td_hash);
1265         rw_wunlock(&tidhash_lock);
1266 }