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/rwlock.h>
  51 #include <sys/umtx.h>
  52 #include <sys/cpuset.h>
  53 #ifdef  HWPMC_HOOKS
  54 #include <sys/pmckern.h>
  55 #endif
  56
  57 #include <security/audit/audit.h>
  58
  59 #include <vm/vm.h>
  60 #include <vm/vm_extern.h>
  61 #include <vm/uma.h>
  62 #include <sys/eventhandler.h>
  63
  64 SDT_PROVIDER_DECLARE(proc);
  65 SDT_PROBE_DEFINE(proc, , , lwp_exit, lwp-exit);
  66
  67
  68 /*
  69  * thread related storage.
  70  */
  71 static uma_zone_t thread_zone;
  72
  73 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
  74 static struct mtx zombie_lock;
  75 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN);
  76
  77 static void thread_zombie(struct thread *);
  78
  79 #define TID_BUFFER_SIZE 1024
  80
  81 struct mtx tid_lock;
  82 static struct unrhdr *tid_unrhdr;
  83 static lwpid_t tid_buffer[TID_BUFFER_SIZE];
  84 static int tid_head, tid_tail;
  85 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
  86
  87 struct  tidhashhead *tidhashtbl;
  88 u_long  tidhash;
  89 struct  rwlock tidhash_lock;
  90
  91 static lwpid_t
  92 tid_alloc(void)
  93 {
  94         lwpid_t tid;
  95
  96         tid = alloc_unr(tid_unrhdr);
  97         if (tid != -1)
  98                 return (tid);
  99         mtx_lock(&tid_lock);
 100         if (tid_head == tid_tail) {
 101                 mtx_unlock(&tid_lock);
 102                 return (-1);
 103         }
 104         tid = tid_buffer[tid_head++];
 105         tid_head %= TID_BUFFER_SIZE;
 106         mtx_unlock(&tid_lock);
 107         return (tid);
 108 }
 109
 110 static void
 111 tid_free(lwpid_t tid)
 112 {
 113         lwpid_t tmp_tid = -1;
 114
 115         mtx_lock(&tid_lock);
 116         if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
 117                 tmp_tid = tid_buffer[tid_head++];
 118                 tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
 119         }
 120         tid_buffer[tid_tail++] = tid;
 121         tid_tail %= TID_BUFFER_SIZE;
 122         mtx_unlock(&tid_lock);
 123         if (tmp_tid != -1)
 124                 free_unr(tid_unrhdr, tmp_tid);
 125 }
 126
 127 /*
 128  * Prepare a thread for use.
 129  */
 130 static int
 131 thread_ctor(void *mem, int size, void *arg, int flags)
 132 {
 133         struct thread   *td;
 134
 135         td = (struct thread *)mem;
 136         td->td_state = TDS_INACTIVE;
 137         td->td_oncpu = NOCPU;
 138
 139         td->td_tid = tid_alloc();
 140
 141         /*
 142          * Note that td_critnest begins life as 1 because the thread is not
 143          * running and is thereby implicitly waiting to be on the receiving
 144          * end of a context switch.
 145          */
 146         td->td_critnest = 1;
 147         td->td_lend_user_pri = PRI_MAX;
 148         EVENTHANDLER_INVOKE(thread_ctor, td);
 149 #ifdef AUDIT
 150         audit_thread_alloc(td);
 151 #endif
 152         umtx_thread_alloc(td);
 153         return (0);
 154 }
 155
 156 /*
 157  * Reclaim a thread after use.
 158  */
 159 static void
 160 thread_dtor(void *mem, int size, void *arg)
 161 {
 162         struct thread *td;
 163
 164         td = (struct thread *)mem;
 165
 166 #ifdef INVARIANTS
 167         /* Verify that this thread is in a safe state to free. */
 168         switch (td->td_state) {
 169         case TDS_INHIBITED:
 170         case TDS_RUNNING:
 171         case TDS_CAN_RUN:
 172         case TDS_RUNQ:
 173                 /*
 174                  * We must never unlink a thread that is in one of
 175                  * these states, because it is currently active.
 176                  */
 177                 panic("bad state for thread unlinking");
 178                 /* NOTREACHED */
 179         case TDS_INACTIVE:
 180                 break;
 181         default:
 182                 panic("bad thread state");
 183                 /* NOTREACHED */
 184         }
 185 #endif
 186 #ifdef AUDIT
 187         audit_thread_free(td);
 188 #endif
 189         /* Free all OSD associated to this thread. */
 190         osd_thread_exit(td);
 191
 192         EVENTHANDLER_INVOKE(thread_dtor, td);
 193         tid_free(td->td_tid);
 194 }
 195
 196 /*
 197  * Initialize type-stable parts of a thread (when newly created).
 198  */
 199 static int
 200 thread_init(void *mem, int size, int flags)
 201 {
 202         struct thread *td;
 203
 204         td = (struct thread *)mem;
 205
 206         td->td_sleepqueue = sleepq_alloc();
 207         td->td_turnstile = turnstile_alloc();
 208         EVENTHANDLER_INVOKE(thread_init, td);
 209         td->td_sched = (struct td_sched *)&td[1];
 210         umtx_thread_init(td);
 211         td->td_kstack = 0;
 212         return (0);
 213 }
 214
 215 /*
 216  * Tear down type-stable parts of a thread (just before being discarded).
 217  */
 218 static void
 219 thread_fini(void *mem, int size)
 220 {
 221         struct thread *td;
 222
 223         td = (struct thread *)mem;
 224         EVENTHANDLER_INVOKE(thread_fini, td);
 225         turnstile_free(td->td_turnstile);
 226         sleepq_free(td->td_sleepqueue);
 227         umtx_thread_fini(td);
 228         seltdfini(td);
 229 }
 230
 231 /*
 232  * For a newly created process,
 233  * link up all the structures and its initial threads etc.
 234  * called from:
 235  * {arch}/{arch}/machdep.c   ia64_init(), init386() etc.
 236  * proc_dtor() (should go away)
 237  * proc_init()
 238  */
 239 void
 240 proc_linkup0(struct proc *p, struct thread *td)
 241 {
 242         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
 243         proc_linkup(p, td);
 244 }
 245
 246 void
 247 proc_linkup(struct proc *p, struct thread *td)
 248 {
 249
 250         sigqueue_init(&p->p_sigqueue, p);
 251         p->p_ksi = ksiginfo_alloc(1);
 252         if (p->p_ksi != NULL) {
 253                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
 254                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
 255         }
 256         LIST_INIT(&p->p_mqnotifier);
 257         p->p_numthreads = 0;
 258         thread_link(td, p);
 259 }
 260
 261 /*
 262  * Initialize global thread allocation resources.
 263  */
 264 void
 265 threadinit(void)
 266 {
 267
 268         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
 269         /* leave one number for thread0 */
 270         tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
 271
 272         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
 273             thread_ctor, thread_dtor, thread_init, thread_fini,
 274             16 - 1, 0);
 275         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
 276         rw_init(&tidhash_lock, "tidhash");
 277 }
 278
 279 /*
 280  * Place an unused thread on the zombie list.
 281  * Use the slpq as that must be unused by now.
 282  */
 283 void
 284 thread_zombie(struct thread *td)
 285 {
 286         mtx_lock_spin(&zombie_lock);
 287         TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
 288         mtx_unlock_spin(&zombie_lock);
 289 }
 290
 291 /*
 292  * Release a thread that has exited after cpu_throw().
 293  */
 294 void
 295 thread_stash(struct thread *td)
 296 {
 297         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
 298         thread_zombie(td);
 299 }
 300
 301 /*
 302  * Reap zombie resources.
 303  */
 304 void
 305 thread_reap(void)
 306 {
 307         struct thread *td_first, *td_next;
 308
 309         /*
 310          * Don't even bother to lock if none at this instant,
 311          * we really don't care about the next instant..
 312          */
 313         if (!TAILQ_EMPTY(&zombie_threads)) {
 314                 mtx_lock_spin(&zombie_lock);
 315                 td_first = TAILQ_FIRST(&zombie_threads);
 316                 if (td_first)
 317                         TAILQ_INIT(&zombie_threads);
 318                 mtx_unlock_spin(&zombie_lock);
 319                 while (td_first) {
 320                         td_next = TAILQ_NEXT(td_first, td_slpq);
 321                         if (td_first->td_ucred)
 322                                 crfree(td_first->td_ucred);
 323                         thread_free(td_first);
 324                         td_first = td_next;
 325                 }
 326         }
 327 }
 328
 329 /*
 330  * Allocate a thread.
 331  */
 332 struct thread *
 333 thread_alloc(int pages)
 334 {
 335         struct thread *td;
 336
 337         thread_reap(); /* check if any zombies to get */
 338
 339         td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
 340         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
 341         if (!vm_thread_new(td, pages)) {
 342                 uma_zfree(thread_zone, td);
 343                 return (NULL);
 344         }
 345         cpu_thread_alloc(td);
 346         return (td);
 347 }
 348
 349 int
 350 thread_alloc_stack(struct thread *td, int pages)
 351 {
 352
 353         KASSERT(td->td_kstack == 0,
 354             ("thread_alloc_stack called on a thread with kstack"));
 355         if (!vm_thread_new(td, pages))
 356                 return (0);
 357         cpu_thread_alloc(td);
 358         return (1);
 359 }
 360
 361 /*
 362  * Deallocate a thread.
 363  */
 364 void
 365 thread_free(struct thread *td)
 366 {
 367
 368         lock_profile_thread_exit(td);
 369         if (td->td_cpuset)
 370                 cpuset_rel(td->td_cpuset);
 371         td->td_cpuset = NULL;
 372         cpu_thread_free(td);
 373         if (td->td_kstack != 0)
 374                 vm_thread_dispose(td);
 375         uma_zfree(thread_zone, td);
 376 }
 377
 378 /*
 379  * Discard the current thread and exit from its context.
 380  * Always called with scheduler locked.
 381  *
 382  * Because we can't free a thread while we're operating under its context,
 383  * push the current thread into our CPU's deadthread holder. This means
 384  * we needn't worry about someone else grabbing our context before we
 385  * do a cpu_throw().
 386  */
 387 void
 388 thread_exit(void)
 389 {
 390         uint64_t runtime, new_switchtime;
 391         struct thread *td;
 392         struct thread *td2;
 393         struct proc *p;
 394         int wakeup_swapper;
 395
 396         td = curthread;
 397         p = td->td_proc;
 398
 399         PROC_SLOCK_ASSERT(p, MA_OWNED);
 400         mtx_assert(&Giant, MA_NOTOWNED);
 401
 402         PROC_LOCK_ASSERT(p, MA_OWNED);
 403         KASSERT(p != NULL, ("thread exiting without a process"));
 404         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
 405             (long)p->p_pid, td->td_name);
 406         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
 407
 408 #ifdef AUDIT
 409         AUDIT_SYSCALL_EXIT(0, td);
 410 #endif
 411         umtx_thread_exit(td);
 412         /*
 413          * drop FPU & debug register state storage, or any other
 414          * architecture specific resources that
 415          * would not be on a new untouched process.
 416          */
 417         cpu_thread_exit(td);    /* XXXSMP */
 418
 419         /*
 420          * The last thread is left attached to the process
 421          * So that the whole bundle gets recycled. Skip
 422          * all this stuff if we never had threads.
 423          * EXIT clears all sign of other threads when
 424          * it goes to single threading, so the last thread always
 425          * takes the short path.
 426          */
 427         if (p->p_flag & P_HADTHREADS) {
 428                 if (p->p_numthreads > 1) {
 429                         thread_unlink(td);
 430                         td2 = FIRST_THREAD_IN_PROC(p);
 431                         sched_exit_thread(td2, td);
 432
 433                         /*
 434                          * The test below is NOT true if we are the
 435                          * sole exiting thread. P_STOPPED_SINGLE is unset
 436                          * in exit1() after it is the only survivor.
 437                          */
 438                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 439                                 if (p->p_numthreads == p->p_suspcount) {
 440                                         thread_lock(p->p_singlethread);
 441                                         wakeup_swapper = thread_unsuspend_one(
 442                                                 p->p_singlethread);
 443                                         thread_unlock(p->p_singlethread);
 444                                         if (wakeup_swapper)
 445                                                 kick_proc0();
 446                                 }
 447                         }
 448
 449                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
 450                         PCPU_SET(deadthread, td);
 451                 } else {
 452                         /*
 453                          * The last thread is exiting.. but not through exit()
 454                          */
 455                         panic ("thread_exit: Last thread exiting on its own");
 456                 }
 457         }
 458 #ifdef  HWPMC_HOOKS
 459         /*
 460          * If this thread is part of a process that is being tracked by hwpmc(4),
 461          * inform the module of the thread's impending exit.
 462          */
 463         if (PMC_PROC_IS_USING_PMCS(td->td_proc))
 464                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
 465 #endif
 466         PROC_UNLOCK(p);
 467
 468         /* Do the same timestamp bookkeeping that mi_switch() would do. */
 469         new_switchtime = cpu_ticks();
 470         runtime = new_switchtime - PCPU_GET(switchtime);
 471         td->td_runtime += runtime;
 472         td->td_incruntime += runtime;
 473         PCPU_SET(switchtime, new_switchtime);
 474         PCPU_SET(switchticks, ticks);
 475         PCPU_INC(cnt.v_swtch);
 476
 477         /* Save our resource usage in our process. */
 478         td->td_ru.ru_nvcsw++;
 479         ruxagg(p, td);
 480         rucollect(&p->p_ru, &td->td_ru);
 481
 482         thread_lock(td);
 483         PROC_SUNLOCK(p);
 484         td->td_state = TDS_INACTIVE;
 485 #ifdef WITNESS
 486         witness_thread_exit(td);
 487 #endif
 488         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
 489         sched_throw(td);
 490         panic("I'm a teapot!");
 491         /* NOTREACHED */
 492 }
 493
 494 /*
 495  * Do any thread specific cleanups that may be needed in wait()
 496  * called with Giant, proc and schedlock not held.
 497  */
 498 void
 499 thread_wait(struct proc *p)
 500 {
 501         struct thread *td;
 502
 503         mtx_assert(&Giant, MA_NOTOWNED);
 504         KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
 505         td = FIRST_THREAD_IN_PROC(p);
 506         /* Lock the last thread so we spin until it exits cpu_throw(). */
 507         thread_lock(td);
 508         thread_unlock(td);
 509         /* Wait for any remaining threads to exit cpu_throw(). */
 510         while (p->p_exitthreads)
 511                 sched_relinquish(curthread);
 512         lock_profile_thread_exit(td);
 513         cpuset_rel(td->td_cpuset);
 514         td->td_cpuset = NULL;
 515         cpu_thread_clean(td);
 516         crfree(td->td_ucred);
 517         thread_reap();  /* check for zombie threads etc. */
 518 }
 519
 520 /*
 521  * Link a thread to a process.
 522  * set up anything that needs to be initialized for it to
 523  * be used by the process.
 524  */
 525 void
 526 thread_link(struct thread *td, struct proc *p)
 527 {
 528
 529         /*
 530          * XXX This can't be enabled because it's called for proc0 before
 531          * its lock has been created.
 532          * PROC_LOCK_ASSERT(p, MA_OWNED);
 533          */
 534         td->td_state    = TDS_INACTIVE;
 535         td->td_proc     = p;
 536         td->td_flags    = TDF_INMEM;
 537
 538         LIST_INIT(&td->td_contested);
 539         LIST_INIT(&td->td_lprof[0]);
 540         LIST_INIT(&td->td_lprof[1]);
 541         sigqueue_init(&td->td_sigqueue, p);
 542         callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
 543         TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
 544         p->p_numthreads++;
 545 }
 546
 547 /*
 548  * Convert a process with one thread to an unthreaded process.
 549  */
 550 void
 551 thread_unthread(struct thread *td)
 552 {
 553         struct proc *p = td->td_proc;
 554
 555         KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
 556         p->p_flag &= ~P_HADTHREADS;
 557 }
 558
 559 /*
 560  * Called from:
 561  *  thread_exit()
 562  */
 563 void
 564 thread_unlink(struct thread *td)
 565 {
 566         struct proc *p = td->td_proc;
 567
 568         PROC_LOCK_ASSERT(p, MA_OWNED);
 569         TAILQ_REMOVE(&p->p_threads, td, td_plist);
 570         p->p_numthreads--;
 571         /* could clear a few other things here */
 572         /* Must  NOT clear links to proc! */
 573 }
 574
 575 static int
 576 calc_remaining(struct proc *p, int mode)
 577 {
 578         int remaining;
 579
 580         PROC_LOCK_ASSERT(p, MA_OWNED);
 581         PROC_SLOCK_ASSERT(p, MA_OWNED);
 582         if (mode == SINGLE_EXIT)
 583                 remaining = p->p_numthreads;
 584         else if (mode == SINGLE_BOUNDARY)
 585                 remaining = p->p_numthreads - p->p_boundary_count;
 586         else if (mode == SINGLE_NO_EXIT)
 587                 remaining = p->p_numthreads - p->p_suspcount;
 588         else
 589                 panic("calc_remaining: wrong mode %d", mode);
 590         return (remaining);
 591 }
 592
 593 /*
 594  * Enforce single-threading.
 595  *
 596  * Returns 1 if the caller must abort (another thread is waiting to
 597  * exit the process or similar). Process is locked!
 598  * Returns 0 when you are successfully the only thread running.
 599  * A process has successfully single threaded in the suspend mode when
 600  * There are no threads in user mode. Threads in the kernel must be
 601  * allowed to continue until they get to the user boundary. They may even
 602  * copy out their return values and data before suspending. They may however be
 603  * accelerated in reaching the user boundary as we will wake up
 604  * any sleeping threads that are interruptable. (PCATCH).
 605  */
 606 int
 607 thread_single(int mode)
 608 {
 609         struct thread *td;
 610         struct thread *td2;
 611         struct proc *p;
 612         int remaining, wakeup_swapper;
 613
 614         td = curthread;
 615         p = td->td_proc;
 616         mtx_assert(&Giant, MA_NOTOWNED);
 617         PROC_LOCK_ASSERT(p, MA_OWNED);
 618         KASSERT((td != NULL), ("curthread is NULL"));
 619
 620         if ((p->p_flag & P_HADTHREADS) == 0)
 621                 return (0);
 622
 623         /* Is someone already single threading? */
 624         if (p->p_singlethread != NULL && p->p_singlethread != td)
 625                 return (1);
 626
 627         if (mode == SINGLE_EXIT) {
 628                 p->p_flag |= P_SINGLE_EXIT;
 629                 p->p_flag &= ~P_SINGLE_BOUNDARY;
 630         } else {
 631                 p->p_flag &= ~P_SINGLE_EXIT;
 632                 if (mode == SINGLE_BOUNDARY)
 633                         p->p_flag |= P_SINGLE_BOUNDARY;
 634                 else
 635                         p->p_flag &= ~P_SINGLE_BOUNDARY;
 636         }
 637         p->p_flag |= P_STOPPED_SINGLE;
 638         PROC_SLOCK(p);
 639         p->p_singlethread = td;
 640         remaining = calc_remaining(p, mode);
 641         while (remaining != 1) {
 642                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
 643                         goto stopme;
 644                 wakeup_swapper = 0;
 645                 FOREACH_THREAD_IN_PROC(p, td2) {
 646                         if (td2 == td)
 647                                 continue;
 648                         thread_lock(td2);
 649                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
 650                         if (TD_IS_INHIBITED(td2)) {
 651                                 switch (mode) {
 652                                 case SINGLE_EXIT:
 653                                         if (TD_IS_SUSPENDED(td2))
 654                                                 wakeup_swapper |=
 655                                                     thread_unsuspend_one(td2);
 656                                         if (TD_ON_SLEEPQ(td2) &&
 657                                             (td2->td_flags & TDF_SINTR))
 658                                                 wakeup_swapper |=
 659                                                     sleepq_abort(td2, EINTR);
 660                                         break;
 661                                 case SINGLE_BOUNDARY:
 662                                         if (TD_IS_SUSPENDED(td2) &&
 663                                             !(td2->td_flags & TDF_BOUNDARY))
 664                                                 wakeup_swapper |=
 665                                                     thread_unsuspend_one(td2);
 666                                         if (TD_ON_SLEEPQ(td2) &&
 667                                             (td2->td_flags & TDF_SINTR))
 668                                                 wakeup_swapper |=
 669                                                     sleepq_abort(td2, ERESTART);
 670                                         break;
 671                                 case SINGLE_NO_EXIT:
 672                                         if (TD_IS_SUSPENDED(td2) &&
 673                                             !(td2->td_flags & TDF_BOUNDARY))
 674                                                 wakeup_swapper |=
 675                                                     thread_unsuspend_one(td2);
 676                                         if (TD_ON_SLEEPQ(td2) &&
 677                                             (td2->td_flags & TDF_SINTR))
 678                                                 wakeup_swapper |=
 679                                                     sleepq_abort(td2, ERESTART);
 680                                         break;
 681                                 default:
 682                                         break;
 683                                 }
 684                         }
 685 #ifdef SMP
 686                         else if (TD_IS_RUNNING(td2) && td != td2) {
 687                                 forward_signal(td2);
 688                         }
 689 #endif
 690                         thread_unlock(td2);
 691                 }
 692                 if (wakeup_swapper)
 693                         kick_proc0();
 694                 remaining = calc_remaining(p, mode);
 695
 696                 /*
 697                  * Maybe we suspended some threads.. was it enough?
 698                  */
 699                 if (remaining == 1)
 700                         break;
 701
 702 stopme:
 703                 /*
 704                  * Wake us up when everyone else has suspended.
 705                  * In the mean time we suspend as well.
 706                  */
 707                 thread_suspend_switch(td);
 708                 remaining = calc_remaining(p, mode);
 709         }
 710         if (mode == SINGLE_EXIT) {
 711                 /*
 712                  * We have gotten rid of all the other threads and we
 713                  * are about to either exit or exec. In either case,
 714                  * we try our utmost  to revert to being a non-threaded
 715                  * process.
 716                  */
 717                 p->p_singlethread = NULL;
 718                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
 719                 thread_unthread(td);
 720         }
 721         PROC_SUNLOCK(p);
 722         return (0);
 723 }
 724
 725 /*
 726  * Called in from locations that can safely check to see
 727  * whether we have to suspend or at least throttle for a
 728  * single-thread event (e.g. fork).
 729  *
 730  * Such locations include userret().
 731  * If the "return_instead" argument is non zero, the thread must be able to
 732  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
 733  *
 734  * The 'return_instead' argument tells the function if it may do a
 735  * thread_exit() or suspend, or whether the caller must abort and back
 736  * out instead.
 737  *
 738  * If the thread that set the single_threading request has set the
 739  * P_SINGLE_EXIT bit in the process flags then this call will never return
 740  * if 'return_instead' is false, but will exit.
 741  *
 742  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
 743  *---------------+--------------------+---------------------
 744  *       0       | returns 0          |   returns 0 or 1
 745  *               | when ST ends       |   immediatly
 746  *---------------+--------------------+---------------------
 747  *       1       | thread exits       |   returns 1
 748  *               |                    |  immediatly
 749  * 0 = thread_exit() or suspension ok,
 750  * other = return error instead of stopping the thread.
 751  *
 752  * While a full suspension is under effect, even a single threading
 753  * thread would be suspended if it made this call (but it shouldn't).
 754  * This call should only be made from places where
 755  * thread_exit() would be safe as that may be the outcome unless
 756  * return_instead is set.
 757  */
 758 int
 759 thread_suspend_check(int return_instead)
 760 {
 761         struct thread *td;
 762         struct proc *p;
 763         int wakeup_swapper;
 764
 765         td = curthread;
 766         p = td->td_proc;
 767         mtx_assert(&Giant, MA_NOTOWNED);
 768         PROC_LOCK_ASSERT(p, MA_OWNED);
 769         while (P_SHOULDSTOP(p) ||
 770               ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
 771                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 772                         KASSERT(p->p_singlethread != NULL,
 773                             ("singlethread not set"));
 774                         /*
 775                          * The only suspension in action is a
 776                          * single-threading. Single threader need not stop.
 777                          * XXX Should be safe to access unlocked
 778                          * as it can only be set to be true by us.
 779                          */
 780                         if (p->p_singlethread == td)
 781                                 return (0);     /* Exempt from stopping. */
 782                 }
 783                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
 784                         return (EINTR);
 785
 786                 /* Should we goto user boundary if we didn't come from there? */
 787                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
 788                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
 789                         return (ERESTART);
 790
 791                 /*
 792                  * If the process is waiting for us to exit,
 793                  * this thread should just suicide.
 794                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
 795                  */
 796                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
 797                         PROC_UNLOCK(p);
 798                         tidhash_remove(td);
 799                         PROC_LOCK(p);
 800                         tdsigcleanup(td);
 801                         PROC_SLOCK(p);
 802                         thread_stopped(p);
 803                         thread_exit();
 804                 }
 805
 806                 PROC_SLOCK(p);
 807                 thread_stopped(p);
 808                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 809                         if (p->p_numthreads == p->p_suspcount + 1) {
 810                                 thread_lock(p->p_singlethread);
 811                                 wakeup_swapper =
 812                                     thread_unsuspend_one(p->p_singlethread);
 813                                 thread_unlock(p->p_singlethread);
 814                                 if (wakeup_swapper)
 815                                         kick_proc0();
 816                         }
 817                 }
 818                 PROC_UNLOCK(p);
 819                 thread_lock(td);
 820                 /*
 821                  * When a thread suspends, it just
 822                  * gets taken off all queues.
 823                  */
 824                 thread_suspend_one(td);
 825                 if (return_instead == 0) {
 826                         p->p_boundary_count++;
 827                         td->td_flags |= TDF_BOUNDARY;
 828                 }
 829                 PROC_SUNLOCK(p);
 830                 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
 831                 if (return_instead == 0)
 832                         td->td_flags &= ~TDF_BOUNDARY;
 833                 thread_unlock(td);
 834                 PROC_LOCK(p);
 835                 if (return_instead == 0) {
 836                         PROC_SLOCK(p);
 837                         p->p_boundary_count--;
 838                         PROC_SUNLOCK(p);
 839                 }
 840         }
 841         return (0);
 842 }
 843
 844 void
 845 thread_suspend_switch(struct thread *td)
 846 {
 847         struct proc *p;
 848
 849         p = td->td_proc;
 850         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
 851         PROC_LOCK_ASSERT(p, MA_OWNED);
 852         PROC_SLOCK_ASSERT(p, MA_OWNED);
 853         /*
 854          * We implement thread_suspend_one in stages here to avoid
 855          * dropping the proc lock while the thread lock is owned.
 856          */
 857         thread_stopped(p);
 858         p->p_suspcount++;
 859         PROC_UNLOCK(p);
 860         thread_lock(td);
 861         td->td_flags &= ~TDF_NEEDSUSPCHK;
 862         TD_SET_SUSPENDED(td);
 863         sched_sleep(td, 0);
 864         PROC_SUNLOCK(p);
 865         DROP_GIANT();
 866         mi_switch(SW_VOL | SWT_SUSPEND, NULL);
 867         thread_unlock(td);
 868         PICKUP_GIANT();
 869         PROC_LOCK(p);
 870         PROC_SLOCK(p);
 871 }
 872
 873 void
 874 thread_suspend_one(struct thread *td)
 875 {
 876         struct proc *p = td->td_proc;
 877
 878         PROC_SLOCK_ASSERT(p, MA_OWNED);
 879         THREAD_LOCK_ASSERT(td, MA_OWNED);
 880         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
 881         p->p_suspcount++;
 882         td->td_flags &= ~TDF_NEEDSUSPCHK;
 883         TD_SET_SUSPENDED(td);
 884         sched_sleep(td, 0);
 885 }
 886
 887 int
 888 thread_unsuspend_one(struct thread *td)
 889 {
 890         struct proc *p = td->td_proc;
 891
 892         PROC_SLOCK_ASSERT(p, MA_OWNED);
 893         THREAD_LOCK_ASSERT(td, MA_OWNED);
 894         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
 895         TD_CLR_SUSPENDED(td);
 896         p->p_suspcount--;
 897         return (setrunnable(td));
 898 }
 899
 900 /*
 901  * Allow all threads blocked by single threading to continue running.
 902  */
 903 void
 904 thread_unsuspend(struct proc *p)
 905 {
 906         struct thread *td;
 907         int wakeup_swapper;
 908
 909         PROC_LOCK_ASSERT(p, MA_OWNED);
 910         PROC_SLOCK_ASSERT(p, MA_OWNED);
 911         wakeup_swapper = 0;
 912         if (!P_SHOULDSTOP(p)) {
 913                 FOREACH_THREAD_IN_PROC(p, td) {
 914                         thread_lock(td);
 915                         if (TD_IS_SUSPENDED(td)) {
 916                                 wakeup_swapper |= thread_unsuspend_one(td);
 917                         }
 918                         thread_unlock(td);
 919                 }
 920         } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
 921             (p->p_numthreads == p->p_suspcount)) {
 922                 /*
 923                  * Stopping everything also did the job for the single
 924                  * threading request. Now we've downgraded to single-threaded,
 925                  * let it continue.
 926                  */
 927                 thread_lock(p->p_singlethread);
 928                 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
 929                 thread_unlock(p->p_singlethread);
 930         }
 931         if (wakeup_swapper)
 932                 kick_proc0();
 933 }
 934
 935 /*
 936  * End the single threading mode..
 937  */
 938 void
 939 thread_single_end(void)
 940 {
 941         struct thread *td;
 942         struct proc *p;
 943         int wakeup_swapper;
 944
 945         td = curthread;
 946         p = td->td_proc;
 947         PROC_LOCK_ASSERT(p, MA_OWNED);
 948         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
 949         PROC_SLOCK(p);
 950         p->p_singlethread = NULL;
 951         wakeup_swapper = 0;
 952         /*
 953          * If there are other threads they may now run,
 954          * unless of course there is a blanket 'stop order'
 955          * on the process. The single threader must be allowed
 956          * to continue however as this is a bad place to stop.
 957          */
 958         if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
 959                 FOREACH_THREAD_IN_PROC(p, td) {
 960                         thread_lock(td);
 961                         if (TD_IS_SUSPENDED(td)) {
 962                                 wakeup_swapper |= thread_unsuspend_one(td);
 963                         }
 964                         thread_unlock(td);
 965                 }
 966         }
 967         PROC_SUNLOCK(p);
 968         if (wakeup_swapper)
 969                 kick_proc0();
 970 }
 971
 972 struct thread *
 973 thread_find(struct proc *p, lwpid_t tid)
 974 {
 975         struct thread *td;
 976
 977         PROC_LOCK_ASSERT(p, MA_OWNED);
 978         FOREACH_THREAD_IN_PROC(p, td) {
 979                 if (td->td_tid == tid)
 980                         break;
 981         }
 982         return (td);
 983 }
 984
 985 /* Locate a thread by number; return with proc lock held. */
 986 struct thread *
 987 tdfind(lwpid_t tid, pid_t pid)
 988 {
 989 #define RUN_THRESH      16
 990         struct thread *td;
 991         int run = 0;
 992
 993         rw_rlock(&tidhash_lock);
 994         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
 995                 if (td->td_tid == tid) {
 996                         if (pid != -1 && td->td_proc->p_pid != pid) {
 997                                 td = NULL;
 998                                 break;
 999                         }
1000                         PROC_LOCK(td->td_proc);
1001                         if (td->td_proc->p_state == PRS_NEW) {
1002                                 PROC_UNLOCK(td->td_proc);
1003                                 td = NULL;
1004                                 break;
1005                         }
1006                         if (run > RUN_THRESH) {
1007                                 if (rw_try_upgrade(&tidhash_lock)) {
1008                                         LIST_REMOVE(td, td_hash);
1009                                         LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1010                                                 td, td_hash);
1011                                         rw_wunlock(&tidhash_lock);
1012                                         return (td);
1013                                 }
1014                         }
1015                         break;
1016                 }
1017                 run++;
1018         }
1019         rw_runlock(&tidhash_lock);
1020         return (td);
1021 }
1022
1023 void
1024 tidhash_add(struct thread *td)
1025 {
1026         rw_wlock(&tidhash_lock);
1027         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1028         rw_wunlock(&tidhash_lock);
1029 }
1030
1031 void
1032 tidhash_remove(struct thread *td)
1033 {
1034         rw_wlock(&tidhash_lock);
1035         LIST_REMOVE(td, td_hash);
1036         rw_wunlock(&tidhash_lock);
1037 }