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/rangelock.h>
  43 #include <sys/resourcevar.h>
  44 #include <sys/sdt.h>
  45 #include <sys/smp.h>
  46 #include <sys/sched.h>
  47 #include <sys/sleepqueue.h>
  48 #include <sys/selinfo.h>
  49 #include <sys/turnstile.h>
  50 #include <sys/ktr.h>
  51 #include <sys/rwlock.h>
  52 #include <sys/umtx.h>
  53 #include <sys/cpuset.h>
  54 #ifdef  HWPMC_HOOKS
  55 #include <sys/pmckern.h>
  56 #endif
  57
  58 #include <security/audit/audit.h>
  59
  60 #include <vm/vm.h>
  61 #include <vm/vm_extern.h>
  62 #include <vm/uma.h>
  63 #include <sys/eventhandler.h>
  64
  65 SDT_PROVIDER_DECLARE(proc);
  66 SDT_PROBE_DEFINE(proc, , , lwp_exit, lwp-exit);
  67
  68
  69 /*
  70  * thread related storage.
  71  */
  72 static uma_zone_t thread_zone;
  73
  74 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
  75 static struct mtx zombie_lock;
  76 MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN);
  77
  78 static void thread_zombie(struct thread *);
  79
  80 #define TID_BUFFER_SIZE 1024
  81
  82 struct mtx tid_lock;
  83 static struct unrhdr *tid_unrhdr;
  84 static lwpid_t tid_buffer[TID_BUFFER_SIZE];
  85 static int tid_head, tid_tail;
  86 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
  87
  88 struct  tidhashhead *tidhashtbl;
  89 u_long  tidhash;
  90 struct  rwlock tidhash_lock;
  91
  92 static lwpid_t
  93 tid_alloc(void)
  94 {
  95         lwpid_t tid;
  96
  97         tid = alloc_unr(tid_unrhdr);
  98         if (tid != -1)
  99                 return (tid);
 100         mtx_lock(&tid_lock);
 101         if (tid_head == tid_tail) {
 102                 mtx_unlock(&tid_lock);
 103                 return (-1);
 104         }
 105         tid = tid_buffer[tid_head++];
 106         tid_head %= TID_BUFFER_SIZE;
 107         mtx_unlock(&tid_lock);
 108         return (tid);
 109 }
 110
 111 static void
 112 tid_free(lwpid_t tid)
 113 {
 114         lwpid_t tmp_tid = -1;
 115
 116         mtx_lock(&tid_lock);
 117         if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
 118                 tmp_tid = tid_buffer[tid_head++];
 119                 tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
 120         }
 121         tid_buffer[tid_tail++] = tid;
 122         tid_tail %= TID_BUFFER_SIZE;
 123         mtx_unlock(&tid_lock);
 124         if (tmp_tid != -1)
 125                 free_unr(tid_unrhdr, tmp_tid);
 126 }
 127
 128 /*
 129  * Prepare a thread for use.
 130  */
 131 static int
 132 thread_ctor(void *mem, int size, void *arg, int flags)
 133 {
 134         struct thread   *td;
 135
 136         td = (struct thread *)mem;
 137         td->td_state = TDS_INACTIVE;
 138         td->td_oncpu = NOCPU;
 139
 140         td->td_tid = tid_alloc();
 141
 142         /*
 143          * Note that td_critnest begins life as 1 because the thread is not
 144          * running and is thereby implicitly waiting to be on the receiving
 145          * end of a context switch.
 146          */
 147         td->td_critnest = 1;
 148         td->td_lend_user_pri = PRI_MAX;
 149         EVENTHANDLER_INVOKE(thread_ctor, td);
 150 #ifdef AUDIT
 151         audit_thread_alloc(td);
 152 #endif
 153         umtx_thread_alloc(td);
 154         return (0);
 155 }
 156
 157 /*
 158  * Reclaim a thread after use.
 159  */
 160 static void
 161 thread_dtor(void *mem, int size, void *arg)
 162 {
 163         struct thread *td;
 164
 165         td = (struct thread *)mem;
 166
 167 #ifdef INVARIANTS
 168         /* Verify that this thread is in a safe state to free. */
 169         switch (td->td_state) {
 170         case TDS_INHIBITED:
 171         case TDS_RUNNING:
 172         case TDS_CAN_RUN:
 173         case TDS_RUNQ:
 174                 /*
 175                  * We must never unlink a thread that is in one of
 176                  * these states, because it is currently active.
 177                  */
 178                 panic("bad state for thread unlinking");
 179                 /* NOTREACHED */
 180         case TDS_INACTIVE:
 181                 break;
 182         default:
 183                 panic("bad thread state");
 184                 /* NOTREACHED */
 185         }
 186 #endif
 187 #ifdef AUDIT
 188         audit_thread_free(td);
 189 #endif
 190         /* Free all OSD associated to this thread. */
 191         osd_thread_exit(td);
 192
 193         EVENTHANDLER_INVOKE(thread_dtor, td);
 194         tid_free(td->td_tid);
 195 }
 196
 197 /*
 198  * Initialize type-stable parts of a thread (when newly created).
 199  */
 200 static int
 201 thread_init(void *mem, int size, int flags)
 202 {
 203         struct thread *td;
 204
 205         td = (struct thread *)mem;
 206
 207         td->td_sleepqueue = sleepq_alloc();
 208         td->td_turnstile = turnstile_alloc();
 209         td->td_rlqe = NULL;
 210         EVENTHANDLER_INVOKE(thread_init, td);
 211         td->td_sched = (struct td_sched *)&td[1];
 212         umtx_thread_init(td);
 213         td->td_kstack = 0;
 214         return (0);
 215 }
 216
 217 /*
 218  * Tear down type-stable parts of a thread (just before being discarded).
 219  */
 220 static void
 221 thread_fini(void *mem, int size)
 222 {
 223         struct thread *td;
 224
 225         td = (struct thread *)mem;
 226         EVENTHANDLER_INVOKE(thread_fini, td);
 227         rlqentry_free(td->td_rlqe);
 228         turnstile_free(td->td_turnstile);
 229         sleepq_free(td->td_sleepqueue);
 230         umtx_thread_fini(td);
 231         seltdfini(td);
 232 }
 233
 234 /*
 235  * For a newly created process,
 236  * link up all the structures and its initial threads etc.
 237  * called from:
 238  * {arch}/{arch}/machdep.c   ia64_init(), init386() etc.
 239  * proc_dtor() (should go away)
 240  * proc_init()
 241  */
 242 void
 243 proc_linkup0(struct proc *p, struct thread *td)
 244 {
 245         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
 246         proc_linkup(p, td);
 247 }
 248
 249 void
 250 proc_linkup(struct proc *p, struct thread *td)
 251 {
 252
 253         sigqueue_init(&p->p_sigqueue, p);
 254         p->p_ksi = ksiginfo_alloc(1);
 255         if (p->p_ksi != NULL) {
 256                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
 257                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
 258         }
 259         LIST_INIT(&p->p_mqnotifier);
 260         p->p_numthreads = 0;
 261         thread_link(td, p);
 262 }
 263
 264 /*
 265  * Initialize global thread allocation resources.
 266  */
 267 void
 268 threadinit(void)
 269 {
 270
 271         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
 272         /* leave one number for thread0 */
 273         tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
 274
 275         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
 276             thread_ctor, thread_dtor, thread_init, thread_fini,
 277             16 - 1, 0);
 278         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
 279         rw_init(&tidhash_lock, "tidhash");
 280 }
 281
 282 /*
 283  * Place an unused thread on the zombie list.
 284  * Use the slpq as that must be unused by now.
 285  */
 286 void
 287 thread_zombie(struct thread *td)
 288 {
 289         mtx_lock_spin(&zombie_lock);
 290         TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
 291         mtx_unlock_spin(&zombie_lock);
 292 }
 293
 294 /*
 295  * Release a thread that has exited after cpu_throw().
 296  */
 297 void
 298 thread_stash(struct thread *td)
 299 {
 300         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
 301         thread_zombie(td);
 302 }
 303
 304 /*
 305  * Reap zombie resources.
 306  */
 307 void
 308 thread_reap(void)
 309 {
 310         struct thread *td_first, *td_next;
 311
 312         /*
 313          * Don't even bother to lock if none at this instant,
 314          * we really don't care about the next instant..
 315          */
 316         if (!TAILQ_EMPTY(&zombie_threads)) {
 317                 mtx_lock_spin(&zombie_lock);
 318                 td_first = TAILQ_FIRST(&zombie_threads);
 319                 if (td_first)
 320                         TAILQ_INIT(&zombie_threads);
 321                 mtx_unlock_spin(&zombie_lock);
 322                 while (td_first) {
 323                         td_next = TAILQ_NEXT(td_first, td_slpq);
 324                         if (td_first->td_ucred)
 325                                 crfree(td_first->td_ucred);
 326                         thread_free(td_first);
 327                         td_first = td_next;
 328                 }
 329         }
 330 }
 331
 332 /*
 333  * Allocate a thread.
 334  */
 335 struct thread *
 336 thread_alloc(int pages)
 337 {
 338         struct thread *td;
 339
 340         thread_reap(); /* check if any zombies to get */
 341
 342         td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
 343         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
 344         if (!vm_thread_new(td, pages)) {
 345                 uma_zfree(thread_zone, td);
 346                 return (NULL);
 347         }
 348         cpu_thread_alloc(td);
 349         return (td);
 350 }
 351
 352 int
 353 thread_alloc_stack(struct thread *td, int pages)
 354 {
 355
 356         KASSERT(td->td_kstack == 0,
 357             ("thread_alloc_stack called on a thread with kstack"));
 358         if (!vm_thread_new(td, pages))
 359                 return (0);
 360         cpu_thread_alloc(td);
 361         return (1);
 362 }
 363
 364 /*
 365  * Deallocate a thread.
 366  */
 367 void
 368 thread_free(struct thread *td)
 369 {
 370
 371         lock_profile_thread_exit(td);
 372         if (td->td_cpuset)
 373                 cpuset_rel(td->td_cpuset);
 374         td->td_cpuset = NULL;
 375         cpu_thread_free(td);
 376         if (td->td_kstack != 0)
 377                 vm_thread_dispose(td);
 378         uma_zfree(thread_zone, td);
 379 }
 380
 381 /*
 382  * Discard the current thread and exit from its context.
 383  * Always called with scheduler locked.
 384  *
 385  * Because we can't free a thread while we're operating under its context,
 386  * push the current thread into our CPU's deadthread holder. This means
 387  * we needn't worry about someone else grabbing our context before we
 388  * do a cpu_throw().
 389  */
 390 void
 391 thread_exit(void)
 392 {
 393         uint64_t runtime, new_switchtime;
 394         struct thread *td;
 395         struct thread *td2;
 396         struct proc *p;
 397         int wakeup_swapper;
 398
 399         td = curthread;
 400         p = td->td_proc;
 401
 402         PROC_SLOCK_ASSERT(p, MA_OWNED);
 403         mtx_assert(&Giant, MA_NOTOWNED);
 404
 405         PROC_LOCK_ASSERT(p, MA_OWNED);
 406         KASSERT(p != NULL, ("thread exiting without a process"));
 407         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
 408             (long)p->p_pid, td->td_name);
 409         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
 410
 411 #ifdef AUDIT
 412         AUDIT_SYSCALL_EXIT(0, td);
 413 #endif
 414         umtx_thread_exit(td);
 415         /*
 416          * drop FPU & debug register state storage, or any other
 417          * architecture specific resources that
 418          * would not be on a new untouched process.
 419          */
 420         cpu_thread_exit(td);    /* XXXSMP */
 421
 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
 471         /* Do the same timestamp bookkeeping that mi_switch() would do. */
 472         new_switchtime = cpu_ticks();
 473         runtime = new_switchtime - PCPU_GET(switchtime);
 474         td->td_runtime += runtime;
 475         td->td_incruntime += runtime;
 476         PCPU_SET(switchtime, new_switchtime);
 477         PCPU_SET(switchticks, ticks);
 478         PCPU_INC(cnt.v_swtch);
 479
 480         /* Save our resource usage in our process. */
 481         td->td_ru.ru_nvcsw++;
 482         ruxagg(p, td);
 483         rucollect(&p->p_ru, &td->td_ru);
 484
 485         thread_lock(td);
 486         PROC_SUNLOCK(p);
 487         td->td_state = TDS_INACTIVE;
 488 #ifdef WITNESS
 489         witness_thread_exit(td);
 490 #endif
 491         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
 492         sched_throw(td);
 493         panic("I'm a teapot!");
 494         /* NOTREACHED */
 495 }
 496
 497 /*
 498  * Do any thread specific cleanups that may be needed in wait()
 499  * called with Giant, proc and schedlock not held.
 500  */
 501 void
 502 thread_wait(struct proc *p)
 503 {
 504         struct thread *td;
 505
 506         mtx_assert(&Giant, MA_NOTOWNED);
 507         KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
 508         td = FIRST_THREAD_IN_PROC(p);
 509         /* Lock the last thread so we spin until it exits cpu_throw(). */
 510         thread_lock(td);
 511         thread_unlock(td);
 512         /* Wait for any remaining threads to exit cpu_throw(). */
 513         while (p->p_exitthreads)
 514                 sched_relinquish(curthread);
 515         lock_profile_thread_exit(td);
 516         cpuset_rel(td->td_cpuset);
 517         td->td_cpuset = NULL;
 518         cpu_thread_clean(td);
 519         crfree(td->td_ucred);
 520         thread_reap();  /* check for zombie threads etc. */
 521 }
 522
 523 /*
 524  * Link a thread to a process.
 525  * set up anything that needs to be initialized for it to
 526  * be used by the process.
 527  */
 528 void
 529 thread_link(struct thread *td, struct proc *p)
 530 {
 531
 532         /*
 533          * XXX This can't be enabled because it's called for proc0 before
 534          * its lock has been created.
 535          * PROC_LOCK_ASSERT(p, MA_OWNED);
 536          */
 537         td->td_state    = TDS_INACTIVE;
 538         td->td_proc     = p;
 539         td->td_flags    = TDF_INMEM;
 540
 541         LIST_INIT(&td->td_contested);
 542         LIST_INIT(&td->td_lprof[0]);
 543         LIST_INIT(&td->td_lprof[1]);
 544         sigqueue_init(&td->td_sigqueue, p);
 545         callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
 546         TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
 547         p->p_numthreads++;
 548 }
 549
 550 /*
 551  * Convert a process with one thread to an unthreaded process.
 552  */
 553 void
 554 thread_unthread(struct thread *td)
 555 {
 556         struct proc *p = td->td_proc;
 557
 558         KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
 559         p->p_flag &= ~P_HADTHREADS;
 560 }
 561
 562 /*
 563  * Called from:
 564  *  thread_exit()
 565  */
 566 void
 567 thread_unlink(struct thread *td)
 568 {
 569         struct proc *p = td->td_proc;
 570
 571         PROC_LOCK_ASSERT(p, MA_OWNED);
 572         TAILQ_REMOVE(&p->p_threads, td, td_plist);
 573         p->p_numthreads--;
 574         /* could clear a few other things here */
 575         /* Must  NOT clear links to proc! */
 576 }
 577
 578 static int
 579 calc_remaining(struct proc *p, int mode)
 580 {
 581         int remaining;
 582
 583         PROC_LOCK_ASSERT(p, MA_OWNED);
 584         PROC_SLOCK_ASSERT(p, MA_OWNED);
 585         if (mode == SINGLE_EXIT)
 586                 remaining = p->p_numthreads;
 587         else if (mode == SINGLE_BOUNDARY)
 588                 remaining = p->p_numthreads - p->p_boundary_count;
 589         else if (mode == SINGLE_NO_EXIT)
 590                 remaining = p->p_numthreads - p->p_suspcount;
 591         else
 592                 panic("calc_remaining: wrong mode %d", mode);
 593         return (remaining);
 594 }
 595
 596 /*
 597  * Enforce single-threading.
 598  *
 599  * Returns 1 if the caller must abort (another thread is waiting to
 600  * exit the process or similar). Process is locked!
 601  * Returns 0 when you are successfully the only thread running.
 602  * A process has successfully single threaded in the suspend mode when
 603  * There are no threads in user mode. Threads in the kernel must be
 604  * allowed to continue until they get to the user boundary. They may even
 605  * copy out their return values and data before suspending. They may however be
 606  * accelerated in reaching the user boundary as we will wake up
 607  * any sleeping threads that are interruptable. (PCATCH).
 608  */
 609 int
 610 thread_single(int mode)
 611 {
 612         struct thread *td;
 613         struct thread *td2;
 614         struct proc *p;
 615         int remaining, wakeup_swapper;
 616
 617         td = curthread;
 618         p = td->td_proc;
 619         mtx_assert(&Giant, MA_NOTOWNED);
 620         PROC_LOCK_ASSERT(p, MA_OWNED);
 621         KASSERT((td != NULL), ("curthread is NULL"));
 622
 623         if ((p->p_flag & P_HADTHREADS) == 0)
 624                 return (0);
 625
 626         /* Is someone already single threading? */
 627         if (p->p_singlethread != NULL && p->p_singlethread != td)
 628                 return (1);
 629
 630         if (mode == SINGLE_EXIT) {
 631                 p->p_flag |= P_SINGLE_EXIT;
 632                 p->p_flag &= ~P_SINGLE_BOUNDARY;
 633         } else {
 634                 p->p_flag &= ~P_SINGLE_EXIT;
 635                 if (mode == SINGLE_BOUNDARY)
 636                         p->p_flag |= P_SINGLE_BOUNDARY;
 637                 else
 638                         p->p_flag &= ~P_SINGLE_BOUNDARY;
 639         }
 640         p->p_flag |= P_STOPPED_SINGLE;
 641         PROC_SLOCK(p);
 642         p->p_singlethread = td;
 643         remaining = calc_remaining(p, mode);
 644         while (remaining != 1) {
 645                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
 646                         goto stopme;
 647                 wakeup_swapper = 0;
 648                 FOREACH_THREAD_IN_PROC(p, td2) {
 649                         if (td2 == td)
 650                                 continue;
 651                         thread_lock(td2);
 652                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
 653                         if (TD_IS_INHIBITED(td2)) {
 654                                 switch (mode) {
 655                                 case SINGLE_EXIT:
 656                                         if (TD_IS_SUSPENDED(td2))
 657                                                 wakeup_swapper |=
 658                                                     thread_unsuspend_one(td2);
 659                                         if (TD_ON_SLEEPQ(td2) &&
 660                                             (td2->td_flags & TDF_SINTR))
 661                                                 wakeup_swapper |=
 662                                                     sleepq_abort(td2, EINTR);
 663                                         break;
 664                                 case SINGLE_BOUNDARY:
 665                                         if (TD_IS_SUSPENDED(td2) &&
 666                                             !(td2->td_flags & TDF_BOUNDARY))
 667                                                 wakeup_swapper |=
 668                                                     thread_unsuspend_one(td2);
 669                                         if (TD_ON_SLEEPQ(td2) &&
 670                                             (td2->td_flags & TDF_SINTR))
 671                                                 wakeup_swapper |=
 672                                                     sleepq_abort(td2, ERESTART);
 673                                         break;
 674                                 case SINGLE_NO_EXIT:
 675                                         if (TD_IS_SUSPENDED(td2) &&
 676                                             !(td2->td_flags & TDF_BOUNDARY))
 677                                                 wakeup_swapper |=
 678                                                     thread_unsuspend_one(td2);
 679                                         if (TD_ON_SLEEPQ(td2) &&
 680                                             (td2->td_flags & TDF_SINTR))
 681                                                 wakeup_swapper |=
 682                                                     sleepq_abort(td2, ERESTART);
 683                                         break;
 684                                 default:
 685                                         break;
 686                                 }
 687                         }
 688 #ifdef SMP
 689                         else if (TD_IS_RUNNING(td2) && td != td2) {
 690                                 forward_signal(td2);
 691                         }
 692 #endif
 693                         thread_unlock(td2);
 694                 }
 695                 if (wakeup_swapper)
 696                         kick_proc0();
 697                 remaining = calc_remaining(p, mode);
 698
 699                 /*
 700                  * Maybe we suspended some threads.. was it enough?
 701                  */
 702                 if (remaining == 1)
 703                         break;
 704
 705 stopme:
 706                 /*
 707                  * Wake us up when everyone else has suspended.
 708                  * In the mean time we suspend as well.
 709                  */
 710                 thread_suspend_switch(td);
 711                 remaining = calc_remaining(p, mode);
 712         }
 713         if (mode == SINGLE_EXIT) {
 714                 /*
 715                  * We have gotten rid of all the other threads and we
 716                  * are about to either exit or exec. In either case,
 717                  * we try our utmost  to revert to being a non-threaded
 718                  * process.
 719                  */
 720                 p->p_singlethread = NULL;
 721                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
 722                 thread_unthread(td);
 723         }
 724         PROC_SUNLOCK(p);
 725         return (0);
 726 }
 727
 728 /*
 729  * Called in from locations that can safely check to see
 730  * whether we have to suspend or at least throttle for a
 731  * single-thread event (e.g. fork).
 732  *
 733  * Such locations include userret().
 734  * If the "return_instead" argument is non zero, the thread must be able to
 735  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
 736  *
 737  * The 'return_instead' argument tells the function if it may do a
 738  * thread_exit() or suspend, or whether the caller must abort and back
 739  * out instead.
 740  *
 741  * If the thread that set the single_threading request has set the
 742  * P_SINGLE_EXIT bit in the process flags then this call will never return
 743  * if 'return_instead' is false, but will exit.
 744  *
 745  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
 746  *---------------+--------------------+---------------------
 747  *       0       | returns 0          |   returns 0 or 1
 748  *               | when ST ends       |   immediatly
 749  *---------------+--------------------+---------------------
 750  *       1       | thread exits       |   returns 1
 751  *               |                    |  immediatly
 752  * 0 = thread_exit() or suspension ok,
 753  * other = return error instead of stopping the thread.
 754  *
 755  * While a full suspension is under effect, even a single threading
 756  * thread would be suspended if it made this call (but it shouldn't).
 757  * This call should only be made from places where
 758  * thread_exit() would be safe as that may be the outcome unless
 759  * return_instead is set.
 760  */
 761 int
 762 thread_suspend_check(int return_instead)
 763 {
 764         struct thread *td;
 765         struct proc *p;
 766         int wakeup_swapper;
 767
 768         td = curthread;
 769         p = td->td_proc;
 770         mtx_assert(&Giant, MA_NOTOWNED);
 771         PROC_LOCK_ASSERT(p, MA_OWNED);
 772         while (P_SHOULDSTOP(p) ||
 773               ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
 774                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 775                         KASSERT(p->p_singlethread != NULL,
 776                             ("singlethread not set"));
 777                         /*
 778                          * The only suspension in action is a
 779                          * single-threading. Single threader need not stop.
 780                          * XXX Should be safe to access unlocked
 781                          * as it can only be set to be true by us.
 782                          */
 783                         if (p->p_singlethread == td)
 784                                 return (0);     /* Exempt from stopping. */
 785                 }
 786                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
 787                         return (EINTR);
 788
 789                 /* Should we goto user boundary if we didn't come from there? */
 790                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
 791                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
 792                         return (ERESTART);
 793
 794                 /*
 795                  * If the process is waiting for us to exit,
 796                  * this thread should just suicide.
 797                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
 798                  */
 799                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
 800                         PROC_UNLOCK(p);
 801                         tidhash_remove(td);
 802                         PROC_LOCK(p);
 803                         tdsigcleanup(td);
 804                         PROC_SLOCK(p);
 805                         thread_stopped(p);
 806                         thread_exit();
 807                 }
 808
 809                 PROC_SLOCK(p);
 810                 thread_stopped(p);
 811                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 812                         if (p->p_numthreads == p->p_suspcount + 1) {
 813                                 thread_lock(p->p_singlethread);
 814                                 wakeup_swapper =
 815                                     thread_unsuspend_one(p->p_singlethread);
 816                                 thread_unlock(p->p_singlethread);
 817                                 if (wakeup_swapper)
 818                                         kick_proc0();
 819                         }
 820                 }
 821                 PROC_UNLOCK(p);
 822                 thread_lock(td);
 823                 /*
 824                  * When a thread suspends, it just
 825                  * gets taken off all queues.
 826                  */
 827                 thread_suspend_one(td);
 828                 if (return_instead == 0) {
 829                         p->p_boundary_count++;
 830                         td->td_flags |= TDF_BOUNDARY;
 831                 }
 832                 PROC_SUNLOCK(p);
 833                 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
 834                 if (return_instead == 0)
 835                         td->td_flags &= ~TDF_BOUNDARY;
 836                 thread_unlock(td);
 837                 PROC_LOCK(p);
 838                 if (return_instead == 0) {
 839                         PROC_SLOCK(p);
 840                         p->p_boundary_count--;
 841                         PROC_SUNLOCK(p);
 842                 }
 843         }
 844         return (0);
 845 }
 846
 847 void
 848 thread_suspend_switch(struct thread *td)
 849 {
 850         struct proc *p;
 851
 852         p = td->td_proc;
 853         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
 854         PROC_LOCK_ASSERT(p, MA_OWNED);
 855         PROC_SLOCK_ASSERT(p, MA_OWNED);
 856         /*
 857          * We implement thread_suspend_one in stages here to avoid
 858          * dropping the proc lock while the thread lock is owned.
 859          */
 860         thread_stopped(p);
 861         p->p_suspcount++;
 862         PROC_UNLOCK(p);
 863         thread_lock(td);
 864         td->td_flags &= ~TDF_NEEDSUSPCHK;
 865         TD_SET_SUSPENDED(td);
 866         sched_sleep(td, 0);
 867         PROC_SUNLOCK(p);
 868         DROP_GIANT();
 869         mi_switch(SW_VOL | SWT_SUSPEND, NULL);
 870         thread_unlock(td);
 871         PICKUP_GIANT();
 872         PROC_LOCK(p);
 873         PROC_SLOCK(p);
 874 }
 875
 876 void
 877 thread_suspend_one(struct thread *td)
 878 {
 879         struct proc *p = td->td_proc;
 880
 881         PROC_SLOCK_ASSERT(p, MA_OWNED);
 882         THREAD_LOCK_ASSERT(td, MA_OWNED);
 883         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
 884         p->p_suspcount++;
 885         td->td_flags &= ~TDF_NEEDSUSPCHK;
 886         TD_SET_SUSPENDED(td);
 887         sched_sleep(td, 0);
 888 }
 889
 890 int
 891 thread_unsuspend_one(struct thread *td)
 892 {
 893         struct proc *p = td->td_proc;
 894
 895         PROC_SLOCK_ASSERT(p, MA_OWNED);
 896         THREAD_LOCK_ASSERT(td, MA_OWNED);
 897         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
 898         TD_CLR_SUSPENDED(td);
 899         p->p_suspcount--;
 900         return (setrunnable(td));
 901 }
 902
 903 /*
 904  * Allow all threads blocked by single threading to continue running.
 905  */
 906 void
 907 thread_unsuspend(struct proc *p)
 908 {
 909         struct thread *td;
 910         int wakeup_swapper;
 911
 912         PROC_LOCK_ASSERT(p, MA_OWNED);
 913         PROC_SLOCK_ASSERT(p, MA_OWNED);
 914         wakeup_swapper = 0;
 915         if (!P_SHOULDSTOP(p)) {
 916                 FOREACH_THREAD_IN_PROC(p, td) {
 917                         thread_lock(td);
 918                         if (TD_IS_SUSPENDED(td)) {
 919                                 wakeup_swapper |= thread_unsuspend_one(td);
 920                         }
 921                         thread_unlock(td);
 922                 }
 923         } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
 924             (p->p_numthreads == p->p_suspcount)) {
 925                 /*
 926                  * Stopping everything also did the job for the single
 927                  * threading request. Now we've downgraded to single-threaded,
 928                  * let it continue.
 929                  */
 930                 thread_lock(p->p_singlethread);
 931                 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
 932                 thread_unlock(p->p_singlethread);
 933         }
 934         if (wakeup_swapper)
 935                 kick_proc0();
 936 }
 937
 938 /*
 939  * End the single threading mode..
 940  */
 941 void
 942 thread_single_end(void)
 943 {
 944         struct thread *td;
 945         struct proc *p;
 946         int wakeup_swapper;
 947
 948         td = curthread;
 949         p = td->td_proc;
 950         PROC_LOCK_ASSERT(p, MA_OWNED);
 951         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
 952         PROC_SLOCK(p);
 953         p->p_singlethread = NULL;
 954         wakeup_swapper = 0;
 955         /*
 956          * If there are other threads they may now run,
 957          * unless of course there is a blanket 'stop order'
 958          * on the process. The single threader must be allowed
 959          * to continue however as this is a bad place to stop.
 960          */
 961         if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
 962                 FOREACH_THREAD_IN_PROC(p, td) {
 963                         thread_lock(td);
 964                         if (TD_IS_SUSPENDED(td)) {
 965                                 wakeup_swapper |= thread_unsuspend_one(td);
 966                         }
 967                         thread_unlock(td);
 968                 }
 969         }
 970         PROC_SUNLOCK(p);
 971         if (wakeup_swapper)
 972                 kick_proc0();
 973 }
 974
 975 struct thread *
 976 thread_find(struct proc *p, lwpid_t tid)
 977 {
 978         struct thread *td;
 979
 980         PROC_LOCK_ASSERT(p, MA_OWNED);
 981         FOREACH_THREAD_IN_PROC(p, td) {
 982                 if (td->td_tid == tid)
 983                         break;
 984         }
 985         return (td);
 986 }
 987
 988 /* Locate a thread by number; return with proc lock held. */
 989 struct thread *
 990 tdfind(lwpid_t tid, pid_t pid)
 991 {
 992 #define RUN_THRESH      16
 993         struct thread *td;
 994         int run = 0;
 995
 996         rw_rlock(&tidhash_lock);
 997         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
 998                 if (td->td_tid == tid) {
 999                         if (pid != -1 && td->td_proc->p_pid != pid) {
1000                                 td = NULL;
1001                                 break;
1002                         }
1003                         PROC_LOCK(td->td_proc);
1004                         if (td->td_proc->p_state == PRS_NEW) {
1005                                 PROC_UNLOCK(td->td_proc);
1006                                 td = NULL;
1007                                 break;
1008                         }
1009                         if (run > RUN_THRESH) {
1010                                 if (rw_try_upgrade(&tidhash_lock)) {
1011                                         LIST_REMOVE(td, td_hash);
1012                                         LIST_INSERT_HEAD(TIDHASH(td->td_tid),
1013                                                 td, td_hash);
1014                                         rw_wunlock(&tidhash_lock);
1015                                         return (td);
1016                                 }
1017                         }
1018                         break;
1019                 }
1020                 run++;
1021         }
1022         rw_runlock(&tidhash_lock);
1023         return (td);
1024 }
1025
1026 void
1027 tidhash_add(struct thread *td)
1028 {
1029         rw_wlock(&tidhash_lock);
1030         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
1031         rw_wunlock(&tidhash_lock);
1032 }
1033
1034 void
1035 tidhash_remove(struct thread *td)
1036 {
1037         rw_wlock(&tidhash_lock);
1038         LIST_REMOVE(td, td_hash);
1039         rw_wunlock(&tidhash_lock);
1040 }