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