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 <sys/cdefs.h>
  30 __FBSDID("$FreeBSD$");
  31
  32 #include <sys/param.h>
  33 #include <sys/systm.h>
  34 #include <sys/kernel.h>
  35 #include <sys/lock.h>
  36 #include <sys/mutex.h>
  37 #include <sys/proc.h>
  38 #include <sys/resourcevar.h>
  39 #include <sys/smp.h>
  40 #include <sys/sysctl.h>
  41 #include <sys/sched.h>
  42 #include <sys/sleepqueue.h>
  43 #include <sys/turnstile.h>
  44 #include <sys/ktr.h>
  45 #include <sys/umtx.h>
  46
  47 #include <security/audit/audit.h>
  48
  49 #include <vm/vm.h>
  50 #include <vm/vm_extern.h>
  51 #include <vm/uma.h>
  52
  53 /*
  54  * thread related storage.
  55  */
  56 static uma_zone_t thread_zone;
  57
  58 SYSCTL_NODE(_kern, OID_AUTO, threads, CTLFLAG_RW, 0, "thread allocation");
  59
  60 int max_threads_per_proc = 1500;
  61 SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_per_proc, CTLFLAG_RW,
  62         &max_threads_per_proc, 0, "Limit on threads per proc");
  63
  64 int max_threads_hits;
  65 SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_hits, CTLFLAG_RD,
  66         &max_threads_hits, 0, "");
  67
  68 #ifdef KSE
  69 int virtual_cpu;
  70
  71 #endif
  72 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
  73 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 #ifdef KSE
  79 static int
  80 sysctl_kse_virtual_cpu(SYSCTL_HANDLER_ARGS)
  81 {
  82         int error, new_val;
  83         int def_val;
  84
  85         def_val = mp_ncpus;
  86         if (virtual_cpu == 0)
  87                 new_val = def_val;
  88         else
  89                 new_val = virtual_cpu;
  90         error = sysctl_handle_int(oidp, &new_val, 0, req);
  91         if (error != 0 || req->newptr == NULL)
  92                 return (error);
  93         if (new_val < 0)
  94                 return (EINVAL);
  95         virtual_cpu = new_val;
  96         return (0);
  97 }
  98
  99 /* DEBUG ONLY */
 100 SYSCTL_PROC(_kern_threads, OID_AUTO, virtual_cpu, CTLTYPE_INT|CTLFLAG_RW,
 101         0, sizeof(virtual_cpu), sysctl_kse_virtual_cpu, "I",
 102         "debug virtual cpus");
 103 #endif
 104
 105 struct mtx tid_lock;
 106 static struct unrhdr *tid_unrhdr;
 107
 108 /*
 109  * Prepare a thread for use.
 110  */
 111 static int
 112 thread_ctor(void *mem, int size, void *arg, int flags)
 113 {
 114         struct thread   *td;
 115
 116         td = (struct thread *)mem;
 117         td->td_state = TDS_INACTIVE;
 118         td->td_oncpu = NOCPU;
 119
 120         td->td_tid = alloc_unr(tid_unrhdr);
 121         td->td_syscalls = 0;
 122
 123         /*
 124          * Note that td_critnest begins life as 1 because the thread is not
 125          * running and is thereby implicitly waiting to be on the receiving
 126          * end of a context switch.
 127          */
 128         td->td_critnest = 1;
 129
 130 #ifdef AUDIT
 131         audit_thread_alloc(td);
 132 #endif
 133         umtx_thread_alloc(td);
 134         return (0);
 135 }
 136
 137 /*
 138  * Reclaim a thread after use.
 139  */
 140 static void
 141 thread_dtor(void *mem, int size, void *arg)
 142 {
 143         struct thread *td;
 144
 145         td = (struct thread *)mem;
 146
 147 #ifdef INVARIANTS
 148         /* Verify that this thread is in a safe state to free. */
 149         switch (td->td_state) {
 150         case TDS_INHIBITED:
 151         case TDS_RUNNING:
 152         case TDS_CAN_RUN:
 153         case TDS_RUNQ:
 154                 /*
 155                  * We must never unlink a thread that is in one of
 156                  * these states, because it is currently active.
 157                  */
 158                 panic("bad state for thread unlinking");
 159                 /* NOTREACHED */
 160         case TDS_INACTIVE:
 161                 break;
 162         default:
 163                 panic("bad thread state");
 164                 /* NOTREACHED */
 165         }
 166 #endif
 167 #ifdef AUDIT
 168         audit_thread_free(td);
 169 #endif
 170         free_unr(tid_unrhdr, td->td_tid);
 171         sched_newthread(td);
 172 }
 173
 174 /*
 175  * Initialize type-stable parts of a thread (when newly created).
 176  */
 177 static int
 178 thread_init(void *mem, int size, int flags)
 179 {
 180         struct thread *td;
 181
 182         td = (struct thread *)mem;
 183
 184         vm_thread_new(td, 0);
 185         cpu_thread_setup(td);
 186         td->td_sleepqueue = sleepq_alloc();
 187         td->td_turnstile = turnstile_alloc();
 188         td->td_sched = (struct td_sched *)&td[1];
 189         sched_newthread(td);
 190         umtx_thread_init(td);
 191         return (0);
 192 }
 193
 194 /*
 195  * Tear down type-stable parts of a thread (just before being discarded).
 196  */
 197 static void
 198 thread_fini(void *mem, int size)
 199 {
 200         struct thread *td;
 201
 202         td = (struct thread *)mem;
 203         turnstile_free(td->td_turnstile);
 204         sleepq_free(td->td_sleepqueue);
 205         umtx_thread_fini(td);
 206         vm_thread_dispose(td);
 207 }
 208
 209 /*
 210  * For a newly created process,
 211  * link up all the structures and its initial threads etc.
 212  * called from:
 213  * {arch}/{arch}/machdep.c   ia64_init(), init386() etc.
 214  * proc_dtor() (should go away)
 215  * proc_init()
 216  */
 217 void
 218 proc_linkup(struct proc *p, struct thread *td)
 219 {
 220
 221         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
 222 #ifdef KSE
 223         TAILQ_INIT(&p->p_upcalls);           /* upcall list */
 224 #endif
 225         sigqueue_init(&p->p_sigqueue, p);
 226         p->p_ksi = ksiginfo_alloc(1);
 227         if (p->p_ksi != NULL) {
 228                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
 229                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
 230         }
 231         LIST_INIT(&p->p_mqnotifier);
 232         p->p_numthreads = 0;
 233         thread_link(td, p);
 234 }
 235
 236 /*
 237  * Initialize global thread allocation resources.
 238  */
 239 void
 240 threadinit(void)
 241 {
 242
 243         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
 244         tid_unrhdr = new_unrhdr(PID_MAX + 1, INT_MAX, &tid_lock);
 245
 246         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
 247             thread_ctor, thread_dtor, thread_init, thread_fini,
 248             16 - 1, 0);
 249 #ifdef KSE
 250         kseinit();      /* set up kse specific stuff  e.g. upcall zone*/
 251 #endif
 252 }
 253
 254 /*
 255  * Place an unused thread on the zombie list.
 256  * Use the slpq as that must be unused by now.
 257  */
 258 void
 259 thread_zombie(struct thread *td)
 260 {
 261         mtx_lock_spin(&zombie_lock);
 262         TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
 263         mtx_unlock_spin(&zombie_lock);
 264 }
 265
 266 /*
 267  * Release a thread that has exited after cpu_throw().
 268  */
 269 void
 270 thread_stash(struct thread *td)
 271 {
 272         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
 273         thread_zombie(td);
 274 }
 275
 276 /*
 277  * Reap zombie kse resource.
 278  */
 279 void
 280 thread_reap(void)
 281 {
 282         struct thread *td_first, *td_next;
 283
 284         /*
 285          * Don't even bother to lock if none at this instant,
 286          * we really don't care about the next instant..
 287          */
 288         if (!TAILQ_EMPTY(&zombie_threads)) {
 289                 mtx_lock_spin(&zombie_lock);
 290                 td_first = TAILQ_FIRST(&zombie_threads);
 291                 if (td_first)
 292                         TAILQ_INIT(&zombie_threads);
 293                 mtx_unlock_spin(&zombie_lock);
 294                 while (td_first) {
 295                         td_next = TAILQ_NEXT(td_first, td_slpq);
 296                         if (td_first->td_ucred)
 297                                 crfree(td_first->td_ucred);
 298                         thread_free(td_first);
 299                         td_first = td_next;
 300                 }
 301         }
 302 }
 303
 304 /*
 305  * Allocate a thread.
 306  */
 307 struct thread *
 308 thread_alloc(void)
 309 {
 310
 311         thread_reap(); /* check if any zombies to get */
 312         return (uma_zalloc(thread_zone, M_WAITOK));
 313 }
 314
 315
 316 /*
 317  * Deallocate a thread.
 318  */
 319 void
 320 thread_free(struct thread *td)
 321 {
 322
 323         cpu_thread_clean(td);
 324         uma_zfree(thread_zone, td);
 325 }
 326
 327 /*
 328  * Discard the current thread and exit from its context.
 329  * Always called with scheduler locked.
 330  *
 331  * Because we can't free a thread while we're operating under its context,
 332  * push the current thread into our CPU's deadthread holder. This means
 333  * we needn't worry about someone else grabbing our context before we
 334  * do a cpu_throw().  This may not be needed now as we are under schedlock.
 335  * Maybe we can just do a thread_stash() as thr_exit1 does.
 336  */
 337 /*  XXX
 338  * libthr expects its thread exit to return for the last
 339  * thread, meaning that the program is back to non-threaded
 340  * mode I guess. Because we do this (cpu_throw) unconditionally
 341  * here, they have their own version of it. (thr_exit1())
 342  * that doesn't do it all if this was the last thread.
 343  * It is also called from thread_suspend_check().
 344  * Of course in the end, they end up coming here through exit1
 345  * anyhow..  After fixing 'thr' to play by the rules we should be able
 346  * to merge these two functions together.
 347  *
 348  * called from:
 349  * exit1()
 350  * kse_exit()
 351  * thr_exit()
 352  * ifdef KSE
 353  * thread_user_enter()
 354  * thread_userret()
 355  * endif
 356  * thread_suspend_check()
 357  */
 358 void
 359 thread_exit(void)
 360 {
 361         uint64_t new_switchtime;
 362         struct thread *td;
 363         struct thread *td2;
 364         struct proc *p;
 365
 366         td = curthread;
 367         p = td->td_proc;
 368
 369         PROC_SLOCK_ASSERT(p, MA_OWNED);
 370         mtx_assert(&Giant, MA_NOTOWNED);
 371
 372         PROC_LOCK_ASSERT(p, MA_OWNED);
 373         KASSERT(p != NULL, ("thread exiting without a process"));
 374         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
 375             (long)p->p_pid, p->p_comm);
 376         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
 377
 378 #ifdef AUDIT
 379         AUDIT_SYSCALL_EXIT(0, td);
 380 #endif
 381
 382 #ifdef KSE
 383         if (td->td_standin != NULL) {
 384                 /*
 385                  * Note that we don't need to free the cred here as it
 386                  * is done in thread_reap().
 387                  */
 388                 thread_zombie(td->td_standin);
 389                 td->td_standin = NULL;
 390         }
 391 #endif
 392
 393         umtx_thread_exit(td);
 394
 395         /*
 396          * drop FPU & debug register state storage, or any other
 397          * architecture specific resources that
 398          * would not be on a new untouched process.
 399          */
 400         cpu_thread_exit(td);    /* XXXSMP */
 401
 402         /* Do the same timestamp bookkeeping that mi_switch() would do. */
 403         new_switchtime = cpu_ticks();
 404         p->p_rux.rux_runtime += (new_switchtime - PCPU_GET(switchtime));
 405         PCPU_SET(switchtime, new_switchtime);
 406         PCPU_SET(switchticks, ticks);
 407         PCPU_INC(cnt.v_swtch);
 408         /* Save our resource usage in our process. */
 409         td->td_ru.ru_nvcsw++;
 410         rucollect(&p->p_ru, &td->td_ru);
 411         /*
 412          * The last thread is left attached to the process
 413          * So that the whole bundle gets recycled. Skip
 414          * all this stuff if we never had threads.
 415          * EXIT clears all sign of other threads when
 416          * it goes to single threading, so the last thread always
 417          * takes the short path.
 418          */
 419         if (p->p_flag & P_HADTHREADS) {
 420                 if (p->p_numthreads > 1) {
 421                         thread_lock(td);
 422 #ifdef KSE
 423                         kse_unlink(td);
 424 #else
 425                         thread_unlink(td);
 426 #endif
 427                         thread_unlock(td);
 428                         td2 = FIRST_THREAD_IN_PROC(p);
 429                         sched_exit_thread(td2, td);
 430
 431                         /*
 432                          * The test below is NOT true if we are the
 433                          * sole exiting thread. P_STOPPED_SNGL is unset
 434                          * in exit1() after it is the only survivor.
 435                          */
 436                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 437                                 if (p->p_numthreads == p->p_suspcount) {
 438                                         thread_lock(p->p_singlethread);
 439                                         thread_unsuspend_one(p->p_singlethread);
 440                                         thread_unlock(p->p_singlethread);
 441                                 }
 442                         }
 443
 444                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
 445                         PCPU_SET(deadthread, td);
 446                 } else {
 447                         /*
 448                          * The last thread is exiting.. but not through exit()
 449                          * what should we do?
 450                          * Theoretically this can't happen
 451                          * exit1() - clears threading flags before coming here
 452                          * kse_exit() - treats last thread specially
 453                          * thr_exit() - treats last thread specially
 454                          * ifdef KSE
 455                          * thread_user_enter() - only if more exist
 456                          * thread_userret() - only if more exist
 457                          * endif
 458                          * thread_suspend_check() - only if more exist
 459                          */
 460                         panic ("thread_exit: Last thread exiting on its own");
 461                 }
 462         }
 463         PROC_UNLOCK(p);
 464         thread_lock(td);
 465         /* Save our tick information with both the thread and proc locked */
 466         ruxagg(&p->p_rux, td);
 467         PROC_SUNLOCK(p);
 468         td->td_state = TDS_INACTIVE;
 469         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
 470         sched_throw(td);
 471         panic("I'm a teapot!");
 472         /* NOTREACHED */
 473 }
 474
 475 /*
 476  * Do any thread specific cleanups that may be needed in wait()
 477  * called with Giant, proc and schedlock not held.
 478  */
 479 void
 480 thread_wait(struct proc *p)
 481 {
 482         struct thread *td;
 483
 484         mtx_assert(&Giant, MA_NOTOWNED);
 485         KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
 486         td = FIRST_THREAD_IN_PROC(p);
 487 #ifdef KSE
 488         if (td->td_standin != NULL) {
 489                 if (td->td_standin->td_ucred != NULL) {
 490                         crfree(td->td_standin->td_ucred);
 491                         td->td_standin->td_ucred = NULL;
 492                 }
 493                 thread_free(td->td_standin);
 494                 td->td_standin = NULL;
 495         }
 496 #endif
 497         /* Lock the last thread so we spin until it exits cpu_throw(). */
 498         thread_lock(td);
 499         thread_unlock(td);
 500         /* Wait for any remaining threads to exit cpu_throw(). */
 501         while (p->p_exitthreads)
 502                 sched_relinquish(curthread);
 503         cpu_thread_clean(td);
 504         crfree(td->td_ucred);
 505         thread_reap();  /* check for zombie threads etc. */
 506 }
 507
 508 /*
 509  * Link a thread to a process.
 510  * set up anything that needs to be initialized for it to
 511  * be used by the process.
 512  *
 513  * Note that we do not link to the proc's ucred here.
 514  * The thread is linked as if running but no KSE assigned.
 515  * Called from:
 516  *  proc_linkup()
 517  *  thread_schedule_upcall()
 518  *  thr_create()
 519  */
 520 void
 521 thread_link(struct thread *td, struct proc *p)
 522 {
 523
 524         /*
 525          * XXX This can't be enabled because it's called for proc0 before
 526          * it's spinlock has been created.
 527          * PROC_SLOCK_ASSERT(p, MA_OWNED);
 528          */
 529         td->td_state    = TDS_INACTIVE;
 530         td->td_proc     = p;
 531         td->td_flags    = 0;
 532
 533         LIST_INIT(&td->td_contested);
 534         sigqueue_init(&td->td_sigqueue, p);
 535         callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
 536         TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
 537         p->p_numthreads++;
 538 }
 539
 540 /*
 541  * Convert a process with one thread to an unthreaded process.
 542  * Called from:
 543  *  thread_single(exit)  (called from execve and exit)
 544  *  kse_exit()          XXX may need cleaning up wrt KSE stuff
 545  */
 546 void
 547 thread_unthread(struct thread *td)
 548 {
 549         struct proc *p = td->td_proc;
 550
 551         KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
 552 #ifdef KSE
 553         upcall_remove(td);
 554         p->p_flag &= ~(P_SA|P_HADTHREADS);
 555         td->td_mailbox = NULL;
 556         td->td_pflags &= ~(TDP_SA | TDP_CAN_UNBIND);
 557         if (td->td_standin != NULL) {
 558                 thread_zombie(td->td_standin);
 559                 td->td_standin = NULL;
 560         }
 561 #else
 562         p->p_flag &= ~P_HADTHREADS;
 563 #endif
 564 }
 565
 566 /*
 567  * Called from:
 568  *  thread_exit()
 569  */
 570 void
 571 thread_unlink(struct thread *td)
 572 {
 573         struct proc *p = td->td_proc;
 574
 575         PROC_SLOCK_ASSERT(p, MA_OWNED);
 576         TAILQ_REMOVE(&p->p_threads, td, td_plist);
 577         p->p_numthreads--;
 578         /* could clear a few other things here */
 579         /* Must  NOT clear links to proc! */
 580 }
 581
 582 /*
 583  * Enforce single-threading.
 584  *
 585  * Returns 1 if the caller must abort (another thread is waiting to
 586  * exit the process or similar). Process is locked!
 587  * Returns 0 when you are successfully the only thread running.
 588  * A process has successfully single threaded in the suspend mode when
 589  * There are no threads in user mode. Threads in the kernel must be
 590  * allowed to continue until they get to the user boundary. They may even
 591  * copy out their return values and data before suspending. They may however be
 592  * accelerated in reaching the user boundary as we will wake up
 593  * any sleeping threads that are interruptable. (PCATCH).
 594  */
 595 int
 596 thread_single(int mode)
 597 {
 598         struct thread *td;
 599         struct thread *td2;
 600         struct proc *p;
 601         int remaining;
 602
 603         td = curthread;
 604         p = td->td_proc;
 605         mtx_assert(&Giant, MA_NOTOWNED);
 606         PROC_LOCK_ASSERT(p, MA_OWNED);
 607         KASSERT((td != NULL), ("curthread is NULL"));
 608
 609         if ((p->p_flag & P_HADTHREADS) == 0)
 610                 return (0);
 611
 612         /* Is someone already single threading? */
 613         if (p->p_singlethread != NULL && p->p_singlethread != td)
 614                 return (1);
 615
 616         if (mode == SINGLE_EXIT) {
 617                 p->p_flag |= P_SINGLE_EXIT;
 618                 p->p_flag &= ~P_SINGLE_BOUNDARY;
 619         } else {
 620                 p->p_flag &= ~P_SINGLE_EXIT;
 621                 if (mode == SINGLE_BOUNDARY)
 622                         p->p_flag |= P_SINGLE_BOUNDARY;
 623                 else
 624                         p->p_flag &= ~P_SINGLE_BOUNDARY;
 625         }
 626         p->p_flag |= P_STOPPED_SINGLE;
 627         PROC_SLOCK(p);
 628         p->p_singlethread = td;
 629         if (mode == SINGLE_EXIT)
 630                 remaining = p->p_numthreads;
 631         else if (mode == SINGLE_BOUNDARY)
 632                 remaining = p->p_numthreads - p->p_boundary_count;
 633         else
 634                 remaining = p->p_numthreads - p->p_suspcount;
 635         while (remaining != 1) {
 636                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
 637                         goto stopme;
 638                 FOREACH_THREAD_IN_PROC(p, td2) {
 639                         if (td2 == td)
 640                                 continue;
 641                         thread_lock(td2);
 642                         td2->td_flags |= TDF_ASTPENDING;
 643                         if (TD_IS_INHIBITED(td2)) {
 644                                 switch (mode) {
 645                                 case SINGLE_EXIT:
 646                                         if (td->td_flags & TDF_DBSUSPEND)
 647                                                 td->td_flags &= ~TDF_DBSUSPEND;
 648                                         if (TD_IS_SUSPENDED(td2))
 649                                                 thread_unsuspend_one(td2);
 650                                         if (TD_ON_SLEEPQ(td2) &&
 651                                             (td2->td_flags & TDF_SINTR))
 652                                                 sleepq_abort(td2, EINTR);
 653                                         break;
 654                                 case SINGLE_BOUNDARY:
 655                                         if (TD_IS_SUSPENDED(td2) &&
 656                                             !(td2->td_flags & TDF_BOUNDARY))
 657                                                 thread_unsuspend_one(td2);
 658                                         if (TD_ON_SLEEPQ(td2) &&
 659                                             (td2->td_flags & TDF_SINTR))
 660                                                 sleepq_abort(td2, ERESTART);
 661                                         break;
 662                                 default:
 663                                         if (TD_IS_SUSPENDED(td2)) {
 664                                                 thread_unlock(td2);
 665                                                 continue;
 666                                         }
 667                                         /*
 668                                          * maybe other inhibited states too?
 669                                          */
 670                                         if ((td2->td_flags & TDF_SINTR) &&
 671                                             (td2->td_inhibitors &
 672                                             (TDI_SLEEPING | TDI_SWAPPED)))
 673                                                 thread_suspend_one(td2);
 674                                         break;
 675                                 }
 676                         }
 677 #ifdef SMP
 678                         else if (TD_IS_RUNNING(td2) && td != td2) {
 679                                 forward_signal(td2);
 680                         }
 681 #endif
 682                         thread_unlock(td2);
 683                 }
 684                 if (mode == SINGLE_EXIT)
 685                         remaining = p->p_numthreads;
 686                 else if (mode == SINGLE_BOUNDARY)
 687                         remaining = p->p_numthreads - p->p_boundary_count;
 688                 else
 689                         remaining = p->p_numthreads - p->p_suspcount;
 690
 691                 /*
 692                  * Maybe we suspended some threads.. was it enough?
 693                  */
 694                 if (remaining == 1)
 695                         break;
 696
 697 stopme:
 698                 /*
 699                  * Wake us up when everyone else has suspended.
 700                  * In the mean time we suspend as well.
 701                  */
 702                 thread_suspend_switch(td);
 703                 if (mode == SINGLE_EXIT)
 704                         remaining = p->p_numthreads;
 705                 else if (mode == SINGLE_BOUNDARY)
 706                         remaining = p->p_numthreads - p->p_boundary_count;
 707                 else
 708                         remaining = p->p_numthreads - p->p_suspcount;
 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
 764         td = curthread;
 765         p = td->td_proc;
 766         mtx_assert(&Giant, MA_NOTOWNED);
 767         PROC_LOCK_ASSERT(p, MA_OWNED);
 768         while (P_SHOULDSTOP(p) ||
 769               ((p->p_flag & P_TRACED) && (td->td_flags & TDF_DBSUSPEND))) {
 770                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 771                         KASSERT(p->p_singlethread != NULL,
 772                             ("singlethread not set"));
 773                         /*
 774                          * The only suspension in action is a
 775                          * single-threading. Single threader need not stop.
 776                          * XXX Should be safe to access unlocked
 777                          * as it can only be set to be true by us.
 778                          */
 779                         if (p->p_singlethread == td)
 780                                 return (0);     /* Exempt from stopping. */
 781                 }
 782                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
 783                         return (EINTR);
 784
 785                 /* Should we goto user boundary if we didn't come from there? */
 786                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
 787                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
 788                         return (ERESTART);
 789
 790                 /* If thread will exit, flush its pending signals */
 791                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td))
 792                         sigqueue_flush(&td->td_sigqueue);
 793
 794                 PROC_SLOCK(p);
 795                 thread_stopped(p);
 796                 /*
 797                  * If the process is waiting for us to exit,
 798                  * this thread should just suicide.
 799                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
 800                  */
 801                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td))
 802                         thread_exit();
 803                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
 804                         if (p->p_numthreads == p->p_suspcount + 1) {
 805                                 thread_lock(p->p_singlethread);
 806                                 thread_unsuspend_one(p->p_singlethread);
 807                                 thread_unlock(p->p_singlethread);
 808                         }
 809                 }
 810                 PROC_UNLOCK(p);
 811                 thread_lock(td);
 812                 /*
 813                  * When a thread suspends, it just
 814                  * gets taken off all queues.
 815                  */
 816                 thread_suspend_one(td);
 817                 if (return_instead == 0) {
 818                         p->p_boundary_count++;
 819                         td->td_flags |= TDF_BOUNDARY;
 820                 }
 821                 PROC_SUNLOCK(p);
 822                 mi_switch(SW_INVOL, NULL);
 823                 if (return_instead == 0)
 824                         td->td_flags &= ~TDF_BOUNDARY;
 825                 thread_unlock(td);
 826                 PROC_LOCK(p);
 827                 if (return_instead == 0)
 828                         p->p_boundary_count--;
 829         }
 830         return (0);
 831 }
 832
 833 void
 834 thread_suspend_switch(struct thread *td)
 835 {
 836         struct proc *p;
 837
 838         p = td->td_proc;
 839         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
 840         PROC_LOCK_ASSERT(p, MA_OWNED);
 841         PROC_SLOCK_ASSERT(p, MA_OWNED);
 842         /*
 843          * We implement thread_suspend_one in stages here to avoid
 844          * dropping the proc lock while the thread lock is owned.
 845          */
 846         thread_stopped(p);
 847         p->p_suspcount++;
 848         PROC_UNLOCK(p);
 849         thread_lock(td);
 850         TD_SET_SUSPENDED(td);
 851         PROC_SUNLOCK(p);
 852         DROP_GIANT();
 853         mi_switch(SW_VOL, NULL);
 854         thread_unlock(td);
 855         PICKUP_GIANT();
 856         PROC_LOCK(p);
 857         PROC_SLOCK(p);
 858 }
 859
 860 void
 861 thread_suspend_one(struct thread *td)
 862 {
 863         struct proc *p = td->td_proc;
 864
 865         PROC_SLOCK_ASSERT(p, MA_OWNED);
 866         THREAD_LOCK_ASSERT(td, MA_OWNED);
 867         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
 868         p->p_suspcount++;
 869         TD_SET_SUSPENDED(td);
 870 }
 871
 872 void
 873 thread_unsuspend_one(struct thread *td)
 874 {
 875         struct proc *p = td->td_proc;
 876
 877         PROC_SLOCK_ASSERT(p, MA_OWNED);
 878         THREAD_LOCK_ASSERT(td, MA_OWNED);
 879         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
 880         TD_CLR_SUSPENDED(td);
 881         p->p_suspcount--;
 882         setrunnable(td);
 883 }
 884
 885 /*
 886  * Allow all threads blocked by single threading to continue running.
 887  */
 888 void
 889 thread_unsuspend(struct proc *p)
 890 {
 891         struct thread *td;
 892
 893         PROC_LOCK_ASSERT(p, MA_OWNED);
 894         PROC_SLOCK_ASSERT(p, MA_OWNED);
 895         if (!P_SHOULDSTOP(p)) {
 896                 FOREACH_THREAD_IN_PROC(p, td) {
 897                         thread_lock(td);
 898                         if (TD_IS_SUSPENDED(td)) {
 899                                 thread_unsuspend_one(td);
 900                         }
 901                         thread_unlock(td);
 902                 }
 903         } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
 904             (p->p_numthreads == p->p_suspcount)) {
 905                 /*
 906                  * Stopping everything also did the job for the single
 907                  * threading request. Now we've downgraded to single-threaded,
 908                  * let it continue.
 909                  */
 910                 thread_lock(p->p_singlethread);
 911                 thread_unsuspend_one(p->p_singlethread);
 912                 thread_unlock(p->p_singlethread);
 913         }
 914 }
 915
 916 /*
 917  * End the single threading mode..
 918  */
 919 void
 920 thread_single_end(void)
 921 {
 922         struct thread *td;
 923         struct proc *p;
 924
 925         td = curthread;
 926         p = td->td_proc;
 927         PROC_LOCK_ASSERT(p, MA_OWNED);
 928         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
 929         PROC_SLOCK(p);
 930         p->p_singlethread = NULL;
 931         /*
 932          * If there are other threads they mey now run,
 933          * unless of course there is a blanket 'stop order'
 934          * on the process. The single threader must be allowed
 935          * to continue however as this is a bad place to stop.
 936          */
 937         if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
 938                 FOREACH_THREAD_IN_PROC(p, td) {
 939                         thread_lock(td);
 940                         if (TD_IS_SUSPENDED(td)) {
 941                                 thread_unsuspend_one(td);
 942                         }
 943                         thread_unlock(td);
 944                 }
 945         }
 946         PROC_SUNLOCK(p);
 947 }
 948
 949 struct thread *
 950 thread_find(struct proc *p, lwpid_t tid)
 951 {
 952         struct thread *td;
 953
 954         PROC_LOCK_ASSERT(p, MA_OWNED);
 955         PROC_SLOCK(p);
 956         FOREACH_THREAD_IN_PROC(p, td) {
 957                 if (td->td_tid == tid)
 958                         break;
 959         }
 960         PROC_SUNLOCK(p);
 961         return (td);
 962 }