sys/kern/kern_thread.c

   1 /*-
   2  * Copyright (C) 2001 Julian Elischer <julian@freebsd.org>.
   3  *  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice(s), this list of conditions and the following disclaimer as
  10  *    the first lines of this file unmodified other than the possible
  11  *    addition of one or more copyright notices.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice(s), this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
  17  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  18  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  19  * DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
  20  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  21  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  22  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  23  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  26  * DAMAGE.
  27  */
  28
  29 #include "opt_witness.h"
  30 #include "opt_hwpmc_hooks.h"
  31
  32 #include <sys/cdefs.h>
  33 __FBSDID("$FreeBSD$");
  34
  35 #include <sys/param.h>
  36 #include <sys/systm.h>
  37 #include <sys/kernel.h>
  38 #include <sys/lock.h>
  39 #include <sys/mutex.h>
  40 #include <sys/proc.h>
  41 #include <sys/resourcevar.h>
  42 #include <sys/smp.h>
  43 #include <sys/sched.h>
  44 #include <sys/sleepqueue.h>
  45 #include <sys/selinfo.h>
  46 #include <sys/turnstile.h>
  47 #include <sys/ktr.h>
  48 #include <sys/rwlock.h>
  49 #include <sys/umtx.h>
  50 #include <sys/cpuset.h>
  51 #ifdef  HWPMC_HOOKS
  52 #include <sys/pmckern.h>
  53 #endif
  54
  55 #include <security/audit/audit.h>
  56
  57 #include <vm/vm.h>
  58 #include <vm/vm_extern.h>
  59 #include <vm/uma.h>
  60 #include <sys/eventhandler.h>
  61
  62 /*
  63  * thread related storage.
  64  */
  65 static uma_zone_t thread_zone;
  66
  67 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
  68 static struct mtx zombie_lock;
  69 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN);
  70
  71 static void thread_zombie(struct thread *);
  72
  73 #define TID_BUFFER_SIZE 1024
  74
  75 struct mtx tid_lock;
  76 static struct unrhdr *tid_unrhdr;
  77 static lwpid_t tid_buffer[TID_BUFFER_SIZE];
  78 static int tid_head, tid_tail;
  79 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
  80
  81 struct  tidhashhead *tidhashtbl;
  82 u_long  tidhash;
  83 struct  rwlock tidhash_lock;
  84
  85 static lwpid_t
  86 tid_alloc(void)
  87 {
  88         lwpid_t tid;
  89
  90         tid = alloc_unr(tid_unrhdr);
  91         if (tid != -1)
  92                 return (tid);
  93         mtx_lock(&tid_lock);
  94         if (tid_head == tid_tail) {
  95                 mtx_unlock(&tid_lock);
  96                 return (-1);
  97         }
  98         tid = tid_buffer[tid_head++];
  99         tid_head %= TID_BUFFER_SIZE;
 100         mtx_unlock(&tid_lock);
 101         return (tid);
 102 }
 103
 104 static void
 105 tid_free(lwpid_t tid)
 106 {
 107         lwpid_t tmp_tid = -1;
 108
 109         mtx_lock(&tid_lock);
 110         if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
 111                 tmp_tid = tid_buffer[tid_head++];
 112                 tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
 113         }
 114         tid_buffer[tid_tail++] = tid;
 115         tid_tail %= TID_BUFFER_SIZE;
 116         mtx_unlock(&tid_lock);
 117         if (tmp_tid != -1)
 118                 free_unr(tid_unrhdr, tmp_tid);
 119 }
 120
 121 /*
 122  * Prepare a thread for use.
 123  */
 124 static int
 125 thread_ctor(void *mem, int size, void *arg, int flags)
 126 {
 127         struct thread   *td;
 128
 129         td = (struct thread *)mem;
 130         td->td_state = TDS_INACTIVE;
 131         td->td_oncpu = NOCPU;
 132
 133         td->td_tid = tid_alloc();
 134
 135         /*
 136          * Note that td_critnest begins life as 1 because the thread is not
 137          * running and is thereby implicitly waiting to be on the receiving
 138          * end of a context switch.
 139          */
 140         td->td_critnest = 1;
 141         td->td_lend_user_pri = PRI_MAX;
 142         EVENTHANDLER_INVOKE(thread_ctor, td);
 143 #ifdef AUDIT
 144         audit_thread_alloc(td);
 145 #endif
 146         umtx_thread_alloc(td);
 147         return (0);
 148 }
 149
 150 /*
 151  * Reclaim a thread after use.
 152  */
 153 static void
 154 thread_dtor(void *mem, int size, void *arg)
 155 {
 156         struct thread *td;
 157
 158         td = (struct thread *)mem;
 159
 160 #ifdef INVARIANTS
 161         /* Verify that this thread is in a safe state to free. */
 162         switch (td->td_state) {
 163         case TDS_INHIBITED:
 164         case TDS_RUNNING:
 165         case TDS_CAN_RUN:
 166         case TDS_RUNQ:
 167                 /*
 168                  * We must never unlink a thread that is in one of
 169                  * these states, because it is currently active.
 170                  */
 171                 panic("bad state for thread unlinking");
 172                 /* NOTREACHED */
 173         case TDS_INACTIVE:
 174                 break;
 175         default:
 176                 panic("bad thread state");
 177                 /* NOTREACHED */
 178         }
 179 #endif
 180 #ifdef AUDIT
 181         audit_thread_free(td);
 182 #endif
 183         /* Free all OSD associated to this thread. */
 184         osd_thread_exit(td);
 185
 186         EVENTHANDLER_INVOKE(thread_dtor, td);
 187         tid_free(td->td_tid);
 188 }
 189
 190 /*
 191  * Initialize type-stable parts of a thread (when newly created).
 192  */
 193 static int
 194 thread_init(void *mem, int size, int flags)
 195 {
 196         struct thread *td;
 197
 198         td = (struct thread *)mem;
 199
 200         td->td_sleepqueue = sleepq_alloc();
 201         td->td_turnstile = turnstile_alloc();
 202         EVENTHANDLER_INVOKE(thread_init, td);
 203         td->td_sched = (struct td_sched *)&td[1];
 204         umtx_thread_init(td);
 205         td->td_kstack = 0;
 206         return (0);
 207 }
 208
 209 /*
 210  * Tear down type-stable parts of a thread (just before being discarded).
 211  */
 212 static void
 213 thread_fini(void *mem, int size)
 214 {
 215         struct thread *td;
 216
 217         td = (struct thread *)mem;
 218         EVENTHANDLER_INVOKE(thread_fini, td);
 219         turnstile_free(td->td_turnstile);
 220         sleepq_free(td->td_sleepqueue);
 221         umtx_thread_fini(td);
 222         seltdfini(td);
 223 }
 224
 225 /*
 226  * For a newly created process,
 227  * link up all the structures and its initial threads etc.
 228  * called from:
 229  * {arch}/{arch}/machdep.c   ia64_init(), init386() etc.
 230  * proc_dtor() (should go away)
 231  * proc_init()
 232  */
 233 void
 234 proc_linkup0(struct proc *p, struct thread *td)
 235 {
 236         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
 237         proc_linkup(p, td);
 238 }
 239
 240 void
 241 proc_linkup(struct proc *p, struct thread *td)
 242 {
 243
 244         sigqueue_init(&p->p_sigqueue, p);
 245         p->p_ksi = ksiginfo_alloc(1);
 246         if (p->p_ksi != NULL) {
 247                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
 248                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
 249         }
 250         LIST_INIT(&p->p_mqnotifier);
 251         p->p_numthreads = 0;
 252         thread_link(td, p);
 253 }
 254
 255 /*
 256  * Initialize global thread allocation resources.
 257  */
 258 void
 259 threadinit(void)
 260 {
 261
 262         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
 263         /* leave one number for thread0 */
 264         tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
 265
 266         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
 267             thread_ctor, thread_dtor, thread_init, thread_fini,
 268             16 - 1, 0);
 269         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
 270         rw_init(&tidhash_lock, "tidhash");
 271 }
 272
 273 /*
 274  * Place an unused thread on the zombie list.
 275  * Use the slpq as that must be unused by now.
 276  */
 277 void
 278 thread_zombie(struct thread *td)
 279 {
 280         mtx_lock_spin(&zombie_lock);
 281         TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
 282         mtx_unlock_spin(&zombie_lock);
 283 }
 284
 285 /*
 286  * Release a thread that has exited after cpu_throw().
 287  */
 288 void
 289 thread_stash(struct thread *td)
 290 {
 291         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
 292         thread_zombie(td);
 293 }
 294
 295 /*
 296  * Reap zombie resources.
 297  */
 298 void
 299 thread_reap(void)
 300 {
 301         struct thread *td_first, *td_next;
 302
 303         /*
 304          * Don't even bother to lock if none at this instant,
 305          * we really don't care about the next instant..
 306          */
 307         if (!TAILQ_EMPTY(&zombie_threads)) {
 308                 mtx_lock_spin(&zombie_lock);
 309                 td_first = TAILQ_FIRST(&zombie_threads);
 310                 if (td_first)
 311                         TAILQ_INIT(&zombie_threads);
 312                 mtx_unlock_spin(&zombie_lock);
 313                 while (td_first) {
 314                         td_next = TAILQ_NEXT(td_first, td_slpq);
 315                         if (td_first->td_ucred)
 316                                 crfree(td_first->td_ucred);
 317                         thread_free(td_first);
 318                         td_first = td_next;
 319                 }
 320         }
 321 }
 322
 323 /*
 324  * Allocate a thread.
 325  */
 326 struct thread *
 327 thread_alloc(int pages)
 328 {
 329         struct thread *td;
 330
 331         thread_reap(); /* check if any zombies to get */
 332
 333         td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
 334         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
 335         if (!vm_thread_new(td, pages)) {
 336                 uma_zfree(thread_zone, td);
 337                 return (NULL);
 338         }
 339         cpu_thread_alloc(td);
 340         return (td);
 341 }
 342
 343 int
 344 thread_alloc_stack(struct thread *td, int pages)
 345 {
 346
 347         KASSERT(td->td_kstack == 0,
 348             ("thread_alloc_stack called on a thread with kstack"));
 349         if (!vm_thread_new(td, pages))
 350                 return (0);
 351         cpu_thread_alloc(td);
 352         return (1);
 353 }
 354
 355 /*
 356  * Deallocate a thread.
 357  */
 358 void
 359 thread_free(struct thread *td)
 360 {
 361
 362         lock_profile_thread_exit(td);
 363         if (td->td_cpuset)
 364                 cpuset_rel(td->td_cpuset);
 365         td->td_cpuset = NULL;
 366         cpu_thread_free(td);
 367         if (td->td_kstack != 0)
 368                 vm_thread_dispose(td);
 369         uma_zfree(thread_zone, td);
 370 }
 371
 372 /*
 373  * Discard the current thread and exit from its context.
 374  * Always called with scheduler locked.
 375  *
 376  * Because we can't free a thread while we're operating under its context,
 377  * push the current thread into our CPU's deadthread holder. This means
 378  * we needn't worry about someone else grabbing our context before we
 379  * do a cpu_throw().
 380  */
 381 void
 382 thread_exit(void)
 383 {
 384         uint64_t new_switchtime;
 385         struct thread *td;
 386         struct thread *td2;
 387         struct proc *p;
 388         int wakeup_swapper;
 389
 390         td = curthread;
 391         p = td->td_proc;
 392
 393         PROC_SLOCK_ASSERT(p, MA_OWNED);
 394         mtx_assert(&Giant, MA_NOTOWNED);
 395
 396         PROC_LOCK_ASSERT(p, MA_OWNED);
 397         KASSERT(p != NULL, ("thread exiting without a process"));
 398         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
 399             (long)p->p_pid, td->td_name);
 400         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
 401
 402 #ifdef AUDIT
 403         AUDIT_SYSCALL_EXIT(0, td);
 404 #endif
 405         umtx_thread_exit(td);
 406         /*
 407          * drop FPU & debug register state storage, or any other
 408          * architecture specific resources that
 409          * would not be on a new untouched process.
 410          */
 411         cpu_thread_exit(td);    /* XXXSMP */
 412
 413         /* Do the same timestamp bookkeeping that mi_switch() would do. */
 414         new_switchtime = cpu_ticks();
 415         p->p_rux.rux_runtime += (new_switchtime - PCPU_GET(switchtime));
 416         PCPU_SET(switchtime, new_switchtime);
 417         PCPU_SET(switchticks, ticks);
 418         PCPU_INC(cnt.v_swtch);
 419         /* Save our resource usage in our process. */
 420         td->td_ru.ru_nvcsw++;
 421         rucollect(&p->p_ru, &td->td_ru);
 422         /*
 423          * The last thread is left attached to the process
 424          * So that the whole bundle gets recycled. Skip
 425          * all this stuff if we never had threads.
 426          * EXIT clears all sign of other threads when
 427          * it goes to single threading, so the last thread always
 428          * takes the short path.
 429          */
 430         if (p->p_flag & P_HADTHREADS) {
 431                 if (p->p_numthreads > 1) {
 432                         thread_unlink(td);
 433                         td2 = FIRST_THREAD_IN_PROC(p);
 434                         sched_exit_thread(td2, td);
 435
 436                         /*
 437                          * The test below is NOT true if we are the
 438                          * sole exiting thread. P_STOPPED_SINGLE is unset
 439                          * in exit1() after it is the only survivor.
 440                          */
 441                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 442                                 if (p->p_numthreads == p->p_suspcount) {
 443                                         thread_lock(p->p_singlethread);
 444                                         wakeup_swapper = thread_unsuspend_one(
 445                                                 p->p_singlethread);
 446                                         thread_unlock(p->p_singlethread);
 447                                         if (wakeup_swapper)
 448                                                 kick_proc0();
 449                                 }
 450                         }
 451
 452                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
 453                         PCPU_SET(deadthread, td);
 454                 } else {
 455                         /*
 456                          * The last thread is exiting.. but not through exit()
 457                          */
 458                         panic ("thread_exit: Last thread exiting on its own");
 459                 }
 460         }
 461 #ifdef  HWPMC_HOOKS
 462         /*
 463          * If this thread is part of a process that is being tracked by hwpmc(4),
 464          * inform the module of the thread's impending exit.
 465          */
 466         if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 467                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 468 #endif
 469         PROC_UNLOCK(p);
 470         ruxagg(p, td);
 471         thread_lock(td);
 472         PROC_SUNLOCK(p);
 473         td->td_state = TDS_INACTIVE;
 474 #ifdef WITNESS
 475         witness_thread_exit(td);
 476 #endif
 477         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
 478         sched_throw(td);
 479         panic("I'm a teapot!");
 480         /* NOTREACHED */
 481 }
 482
 483 /*
 484  * Do any thread specific cleanups that may be needed in wait()
 485  * called with Giant, proc and schedlock not held.
 486  */
 487 void
 488 thread_wait(struct proc *p)
 489 {
 490         struct thread *td;
 491
 492         mtx_assert(&Giant, MA_NOTOWNED);
 493         KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
 494         td = FIRST_THREAD_IN_PROC(p);
 495         /* Lock the last thread so we spin until it exits cpu_throw(). */
 496         thread_lock(td);
 497         thread_unlock(td);
 498         /* Wait for any remaining threads to exit cpu_throw(). */
 499         while (p->p_exitthreads)
 500                 sched_relinquish(curthread);
 501         lock_profile_thread_exit(td);
 502         cpuset_rel(td->td_cpuset);
 503         td->td_cpuset = NULL;
 504         cpu_thread_clean(td);
 505         crfree(td->td_ucred);
 506         thread_reap();  /* check for zombie threads etc. */
 507 }
 508
 509 /*
 510  * Link a thread to a process.
 511  * set up anything that needs to be initialized for it to
 512  * be used by the process.
 513  */
 514 void
 515 thread_link(struct thread *td, struct proc *p)
 516 {
 517
 518         /*
 519          * XXX This can't be enabled because it's called for proc0 before
 520          * its lock has been created.
 521          * PROC_LOCK_ASSERT(p, MA_OWNED);
 522          */
 523         td->td_state    = TDS_INACTIVE;
 524         td->td_proc     = p;
 525         td->td_flags    = TDF_INMEM;
 526
 527         LIST_INIT(&td->td_contested);
 528         LIST_INIT(&td->td_lprof[0]);
 529         LIST_INIT(&td->td_lprof[1]);
 530         sigqueue_init(&td->td_sigqueue, p);
 531         callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
 532         TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
 533         p->p_numthreads++;
 534 }
 535
 536 /*
 537  * Convert a process with one thread to an unthreaded process.
 538  */
 539 void
 540 thread_unthread(struct thread *td)
 541 {
 542         struct proc *p = td->td_proc;
 543
 544         KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
 545         p->p_flag &= ~P_HADTHREADS;
 546 }
 547
 548 /*
 549  * Called from:
 550  *  thread_exit()
 551  */
 552 void
 553 thread_unlink(struct thread *td)
 554 {
 555         struct proc *p = td->td_proc;
 556
 557         PROC_LOCK_ASSERT(p, MA_OWNED);
 558         TAILQ_REMOVE(&p->p_threads, td, td_plist);
 559         p->p_numthreads--;
 560         /* could clear a few other things here */
 561         /* Must  NOT clear links to proc! */
 562 }
 563
 564 static int
 565 calc_remaining(struct proc *p, int mode)
 566 {
 567         int remaining;
 568
 569         if (mode == SINGLE_EXIT)
 570                 remaining = p->p_numthreads;
 571         else if (mode == SINGLE_BOUNDARY)
 572                 remaining = p->p_numthreads - p->p_boundary_count;
 573         else if (mode == SINGLE_NO_EXIT)
 574                 remaining = p->p_numthreads - p->p_suspcount;
 575         else
 576                 panic("calc_remaining: wrong mode %d", mode);
 577         return (remaining);
 578 }
 579
 580 /*
 581  * Enforce single-threading.
 582  *
 583  * Returns 1 if the caller must abort (another thread is waiting to
 584  * exit the process or similar). Process is locked!
 585  * Returns 0 when you are successfully the only thread running.
 586  * A process has successfully single threaded in the suspend mode when
 587  * There are no threads in user mode. Threads in the kernel must be
 588  * allowed to continue until they get to the user boundary. They may even
 589  * copy out their return values and data before suspending. They may however be
 590  * accelerated in reaching the user boundary as we will wake up
 591  * any sleeping threads that are interruptable. (PCATCH).
 592  */
 593 int
 594 thread_single(int mode)
 595 {
 596         struct thread *td;
 597         struct thread *td2;
 598         struct proc *p;
 599         int remaining, wakeup_swapper;
 600
 601         td = curthread;
 602         p = td->td_proc;
 603         mtx_assert(&Giant, MA_NOTOWNED);
 604         PROC_LOCK_ASSERT(p, MA_OWNED);
 605         KASSERT((td != NULL), ("curthread is NULL"));
 606
 607         if ((p->p_flag & P_HADTHREADS) == 0)
 608                 return (0);
 609
 610         /* Is someone already single threading? */
 611         if (p->p_singlethread != NULL && p->p_singlethread != td)
 612                 return (1);
 613
 614         if (mode == SINGLE_EXIT) {
 615                 p->p_flag |= P_SINGLE_EXIT;
 616                 p->p_flag &= ~P_SINGLE_BOUNDARY;
 617         } else {
 618                 p->p_flag &= ~P_SINGLE_EXIT;
 619                 if (mode == SINGLE_BOUNDARY)
 620                         p->p_flag |= P_SINGLE_BOUNDARY;
 621                 else
 622                         p->p_flag &= ~P_SINGLE_BOUNDARY;
 623         }
 624         p->p_flag |= P_STOPPED_SINGLE;
 625         PROC_SLOCK(p);
 626         p->p_singlethread = td;
 627         remaining = calc_remaining(p, mode);
 628         while (remaining != 1) {
 629                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
 630                         goto stopme;
 631                 wakeup_swapper = 0;
 632                 FOREACH_THREAD_IN_PROC(p, td2) {
 633                         if (td2 == td)
 634                                 continue;
 635                         thread_lock(td2);
 636                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
 637                         if (TD_IS_INHIBITED(td2)) {
 638                                 switch (mode) {
 639                                 case SINGLE_EXIT:
 640                                         if (TD_IS_SUSPENDED(td2))
 641                                                 wakeup_swapper |=
 642                                                     thread_unsuspend_one(td2);
 643                                         if (TD_ON_SLEEPQ(td2) &&
 644                                             (td2->td_flags & TDF_SINTR))
 645                                                 wakeup_swapper |=
 646                                                     sleepq_abort(td2, EINTR);
 647                                         break;
 648                                 case SINGLE_BOUNDARY:
 649                                         if (TD_IS_SUSPENDED(td2) &&
 650                                             !(td2->td_flags & TDF_BOUNDARY))
 651                                                 wakeup_swapper |=
 652                                                     thread_unsuspend_one(td2);
 653                                         if (TD_ON_SLEEPQ(td2) &&
 654                                             (td2->td_flags & TDF_SINTR))
 655                                                 wakeup_swapper |=
 656                                                     sleepq_abort(td2, ERESTART);
 657                                         break;
 658                                 case SINGLE_NO_EXIT:
 659                                         if (TD_IS_SUSPENDED(td2) &&
 660                                             !(td2->td_flags & TDF_BOUNDARY))
 661                                                 wakeup_swapper |=
 662                                                     thread_unsuspend_one(td2);
 663                                         if (TD_ON_SLEEPQ(td2) &&
 664                                             (td2->td_flags & TDF_SINTR))
 665                                                 wakeup_swapper |=
 666                                                     sleepq_abort(td2, ERESTART);
 667                                         break;
 668                                 default:
 669                                         break;
 670                                 }
 671                         }
 672 #ifdef SMP
 673                         else if (TD_IS_RUNNING(td2) && td != td2) {
 674                                 forward_signal(td2);
 675                         }
 676 #endif
 677                         thread_unlock(td2);
 678                 }
 679                 if (wakeup_swapper)
 680                         kick_proc0();
 681                 remaining = calc_remaining(p, mode);
 682
 683                 /*
 684                  * Maybe we suspended some threads.. was it enough?
 685                  */
 686                 if (remaining == 1)
 687                         break;
 688
 689 stopme:
 690                 /*
 691                  * Wake us up when everyone else has suspended.
 692                  * In the mean time we suspend as well.
 693                  */
 694                 thread_suspend_switch(td);
 695                 remaining = calc_remaining(p, mode);
 696         }
 697         if (mode == SINGLE_EXIT) {
 698                 /*
 699                  * We have gotten rid of all the other threads and we
 700                  * are about to either exit or exec. In either case,
 701                  * we try our utmost  to revert to being a non-threaded
 702                  * process.
 703                  */
 704                 p->p_singlethread = NULL;
 705                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
 706                 thread_unthread(td);
 707         }
 708         PROC_SUNLOCK(p);
 709         return (0);
 710 }
 711
 712 /*
 713  * Called in from locations that can safely check to see
 714  * whether we have to suspend or at least throttle for a
 715  * single-thread event (e.g. fork).
 716  *
 717  * Such locations include userret().
 718  * If the "return_instead" argument is non zero, the thread must be able to
 719  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
 720  *
 721  * The 'return_instead' argument tells the function if it may do a
 722  * thread_exit() or suspend, or whether the caller must abort and back
 723  * out instead.
 724  *
 725  * If the thread that set the single_threading request has set the
 726  * P_SINGLE_EXIT bit in the process flags then this call will never return
 727  * if 'return_instead' is false, but will exit.
 728  *
 729  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
 730  *---------------+--------------------+---------------------
 731  *       0       | returns 0          |   returns 0 or 1
 732  *               | when ST ends       |   immediatly
 733  *---------------+--------------------+---------------------
 734  *       1       | thread exits       |   returns 1
 735  *               |                    |  immediatly
 736  * 0 = thread_exit() or suspension ok,
 737  * other = return error instead of stopping the thread.
 738  *
 739  * While a full suspension is under effect, even a single threading
 740  * thread would be suspended if it made this call (but it shouldn't).
 741  * This call should only be made from places where
 742  * thread_exit() would be safe as that may be the outcome unless
 743  * return_instead is set.
 744  */
 745 int
 746 thread_suspend_check(int return_instead)
 747 {
 748         struct thread *td;
 749         struct proc *p;
 750         int wakeup_swapper;
 751
 752         td = curthread;
 753         p = td->td_proc;
 754         mtx_assert(&Giant, MA_NOTOWNED);
 755         PROC_LOCK_ASSERT(p, MA_OWNED);
 756         while (P_SHOULDSTOP(p) ||
 757               ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
 758                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 759                         KASSERT(p->p_singlethread != NULL,
 760                             ("singlethread not set"));
 761                         /*
 762                          * The only suspension in action is a
 763                          * single-threading. Single threader need not stop.
 764                          * XXX Should be safe to access unlocked
 765                          * as it can only be set to be true by us.
 766                          */
 767                         if (p->p_singlethread == td)
 768                                 return (0);     /* Exempt from stopping. */
 769                 }
 770                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
 771                         return (EINTR);
 772
 773                 /* Should we goto user boundary if we didn't come from there? */
 774                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
 775                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
 776                         return (ERESTART);
 777
 778                 /*
 779                  * If the process is waiting for us to exit,
 780                  * this thread should just suicide.
 781                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
 782                  */
 783                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
 784                         PROC_UNLOCK(p);
 785                         tidhash_remove(td);
 786                         PROC_LOCK(p);
 787                         tdsigcleanup(td);
 788                         PROC_SLOCK(p);
 789                         thread_stopped(p);
 790                         thread_exit();
 791                 }
 792
 793                 PROC_SLOCK(p);
 794                 thread_stopped(p);
 795                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 796                         if (p->p_numthreads == p->p_suspcount + 1) {
 797                                 thread_lock(p->p_singlethread);
 798                                 wakeup_swapper =
 799                                     thread_unsuspend_one(p->p_singlethread);
 800                                 thread_unlock(p->p_singlethread);
 801                                 if (wakeup_swapper)
 802                                         kick_proc0();
 803                         }
 804                 }
 805                 PROC_UNLOCK(p);
 806                 thread_lock(td);
 807                 /*
 808                  * When a thread suspends, it just
 809                  * gets taken off all queues.
 810                  */
 811                 thread_suspend_one(td);
 812                 if (return_instead == 0) {
 813                         p->p_boundary_count++;
 814                         td->td_flags |= TDF_BOUNDARY;
 815                 }
 816                 PROC_SUNLOCK(p);
 817                 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
 818                 if (return_instead == 0)
 819                         td->td_flags &= ~TDF_BOUNDARY;
 820                 thread_unlock(td);
 821                 PROC_LOCK(p);
 822                 if (return_instead == 0)
 823                         p->p_boundary_count--;
 824         }
 825         return (0);
 826 }
 827
 828 void
 829 thread_suspend_switch(struct thread *td)
 830 {
 831         struct proc *p;
 832
 833         p = td->td_proc;
 834         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
 835         PROC_LOCK_ASSERT(p, MA_OWNED);
 836         PROC_SLOCK_ASSERT(p, MA_OWNED);
 837         /*
 838          * We implement thread_suspend_one in stages here to avoid
 839          * dropping the proc lock while the thread lock is owned.
 840          */
 841         thread_stopped(p);
 842         p->p_suspcount++;
 843         PROC_UNLOCK(p);
 844         thread_lock(td);
 845         td->td_flags &= ~TDF_NEEDSUSPCHK;
 846         TD_SET_SUSPENDED(td);
 847         sched_sleep(td, 0);
 848         PROC_SUNLOCK(p);
 849         DROP_GIANT();
 850         mi_switch(SW_VOL | SWT_SUSPEND, NULL);
 851         thread_unlock(td);
 852         PICKUP_GIANT();
 853         PROC_LOCK(p);
 854         PROC_SLOCK(p);
 855 }
 856
 857 void
 858 thread_suspend_one(struct thread *td)
 859 {
 860         struct proc *p = td->td_proc;
 861
 862         PROC_SLOCK_ASSERT(p, MA_OWNED);
 863         THREAD_LOCK_ASSERT(td, MA_OWNED);
 864         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
 865         p->p_suspcount++;
 866         td->td_flags &= ~TDF_NEEDSUSPCHK;
 867         TD_SET_SUSPENDED(td);
 868         sched_sleep(td, 0);
 869 }
 870
 871 int
 872 thread_unsuspend_one(struct thread *td)
 873 {
 874         struct proc *p = td->td_proc;
 875
 876         PROC_SLOCK_ASSERT(p, MA_OWNED);
 877         THREAD_LOCK_ASSERT(td, MA_OWNED);
 878         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
 879         TD_CLR_SUSPENDED(td);
 880         p->p_suspcount--;
 881         return (setrunnable(td));
 882 }
 883
 884 /*
 885  * Allow all threads blocked by single threading to continue running.
 886  */
 887 void
 888 thread_unsuspend(struct proc *p)
 889 {
 890         struct thread *td;
 891         int wakeup_swapper;
 892
 893         PROC_LOCK_ASSERT(p, MA_OWNED);
 894         PROC_SLOCK_ASSERT(p, MA_OWNED);
 895         wakeup_swapper = 0;
 896         if (!P_SHOULDSTOP(p)) {
 897                 FOREACH_THREAD_IN_PROC(p, td) {
 898                         thread_lock(td);
 899                         if (TD_IS_SUSPENDED(td)) {
 900                                 wakeup_swapper |= thread_unsuspend_one(td);
 901                         }
 902                         thread_unlock(td);
 903                 }
 904         } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
 905             (p->p_numthreads == p->p_suspcount)) {
 906                 /*
 907                  * Stopping everything also did the job for the single
 908                  * threading request. Now we've downgraded to single-threaded,
 909                  * let it continue.
 910                  */
 911                 thread_lock(p->p_singlethread);
 912                 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
 913                 thread_unlock(p->p_singlethread);
 914         }
 915         if (wakeup_swapper)
 916                 kick_proc0();
 917 }
 918
 919 /*
 920  * End the single threading mode..
 921  */
 922 void
 923 thread_single_end(void)
 924 {
 925         struct thread *td;
 926         struct proc *p;
 927         int wakeup_swapper;
 928
 929         td = curthread;
 930         p = td->td_proc;
 931         PROC_LOCK_ASSERT(p, MA_OWNED);
 932         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
 933         PROC_SLOCK(p);
 934         p->p_singlethread = NULL;
 935         wakeup_swapper = 0;
 936         /*
 937          * If there are other threads they may now run,
 938          * unless of course there is a blanket 'stop order'
 939          * on the process. The single threader must be allowed
 940          * to continue however as this is a bad place to stop.
 941          */
 942         if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
 943                 FOREACH_THREAD_IN_PROC(p, td) {
 944                         thread_lock(td);
 945                         if (TD_IS_SUSPENDED(td)) {
 946                                 wakeup_swapper |= thread_unsuspend_one(td);
 947                         }
 948                         thread_unlock(td);
 949                 }
 950         }
 951         PROC_SUNLOCK(p);
 952         if (wakeup_swapper)
 953                 kick_proc0();
 954 }
 955
 956 struct thread *
 957 thread_find(struct proc *p, lwpid_t tid)
 958 {
 959         struct thread *td;
 960
 961         PROC_LOCK_ASSERT(p, MA_OWNED);
 962         FOREACH_THREAD_IN_PROC(p, td) {
 963                 if (td->td_tid == tid)
 964                         break;
 965         }
 966         return (td);
 967 }
 968
 969 /* Locate a thread by number; return with proc lock held. */
 970 struct thread *
 971 tdfind(lwpid_t tid, pid_t pid)
 972 {
 973 #define RUN_THRESH      16
 974         struct thread *td;
 975         int run = 0;
 976
 977         rw_rlock(&tidhash_lock);
 978         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
 979                 if (td->td_tid == tid) {
 980                         if (pid != -1 && td->td_proc->p_pid != pid) {
 981                                 td = NULL;
 982                                 break;
 983                         }
 984                         PROC_LOCK(td->td_proc);
 985                         if (td->td_proc->p_state == PRS_NEW) {
 986                                 PROC_UNLOCK(td->td_proc);
 987                                 td = NULL;
 988                                 break;
 989                         }
 990                         if (run > RUN_THRESH) {
 991                                 if (rw_try_upgrade(&tidhash_lock)) {
 992                                         LIST_REMOVE(td, td_hash);
 993                                         LIST_INSERT_HEAD(TIDHASH(td->td_tid),
 994                                                 td, td_hash);
 995                                         rw_wunlock(&tidhash_lock);
 996                                         return (td);
 997                                 }
 998                         }
 999                         break;
1000                 }
1001                 run++;
1002         }
1003         rw_runlock(&tidhash_lock);
1004         return (td);
1005 }
1006
1007 void
1008 tidhash_add(struct thread *td)
1009 {
1010         rw_wlock(&tidhash_lock);
1011         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1012         rw_wunlock(&tidhash_lock);
1013 }
1014
1015 void
1016 tidhash_remove(struct thread *td)
1017 {
1018         rw_wlock(&tidhash_lock);
1019         LIST_REMOVE(td, td_hash);
1020         rw_wunlock(&tidhash_lock);
1021 }