kern_thread.c

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    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 
   31 #include <sys/cdefs.h>
   32 __FBSDID("$FreeBSD: releng/8.0/sys/kern/kern_thread.c 196977 2009-09-08 15:31:23Z kib $");
   33 
   34 #include <sys/param.h>
   35 #include <sys/systm.h>
   36 #include <sys/kernel.h>
   37 #include <sys/lock.h>
   38 #include <sys/mutex.h>
   39 #include <sys/proc.h>
   40 #include <sys/resourcevar.h>
   41 #include <sys/smp.h>
   42 #include <sys/sysctl.h>
   43 #include <sys/sched.h>
   44 #include <sys/sleepqueue.h>
   45 #include <sys/selinfo.h>
   46 #include <sys/turnstile.h>
   47 #include <sys/ktr.h>
   48 #include <sys/umtx.h>
   49 #include <sys/cpuset.h>
   50 
   51 #include <security/audit/audit.h>
   52 
   53 #include <vm/vm.h>
   54 #include <vm/vm_extern.h>
   55 #include <vm/uma.h>
   56 #include <sys/eventhandler.h>
   57 
   58 /*
   59  * thread related storage.
   60  */
   61 static uma_zone_t thread_zone;
   62 
   63 SYSCTL_NODE(_kern, OID_AUTO, threads, CTLFLAG_RW, 0, "thread allocation");
   64 
   65 int max_threads_per_proc = 1500;
   66 SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_per_proc, CTLFLAG_RW,
   67         &max_threads_per_proc, 0, "Limit on threads per proc");
   68 
   69 int max_threads_hits;
   70 SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_hits, CTLFLAG_RD,
   71         &max_threads_hits, 0, "");
   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 struct mtx tid_lock;
   80 static struct unrhdr *tid_unrhdr;
   81 
   82 /*
   83  * Prepare a thread for use.
   84  */
   85 static int
   86 thread_ctor(void *mem, int size, void *arg, int flags)
   87 {
   88         struct thread   *td;
   89 
   90         td = (struct thread *)mem;
   91         td->td_state = TDS_INACTIVE;
   92         td->td_oncpu = NOCPU;
   93 
   94         td->td_tid = alloc_unr(tid_unrhdr);
   95         td->td_syscalls = 0;
   96 
   97         /*
   98          * Note that td_critnest begins life as 1 because the thread is not
   99          * running and is thereby implicitly waiting to be on the receiving
  100          * end of a context switch.
  101          */
  102         td->td_critnest = 1;
  103         EVENTHANDLER_INVOKE(thread_ctor, td);
  104 #ifdef AUDIT
  105         audit_thread_alloc(td);
  106 #endif
  107         umtx_thread_alloc(td);
  108         return (0);
  109 }
  110 
  111 /*
  112  * Reclaim a thread after use.
  113  */
  114 static void
  115 thread_dtor(void *mem, int size, void *arg)
  116 {
  117         struct thread *td;
  118 
  119         td = (struct thread *)mem;
  120 
  121 #ifdef INVARIANTS
  122         /* Verify that this thread is in a safe state to free. */
  123         switch (td->td_state) {
  124         case TDS_INHIBITED:
  125         case TDS_RUNNING:
  126         case TDS_CAN_RUN:
  127         case TDS_RUNQ:
  128                 /*
  129                  * We must never unlink a thread that is in one of
  130                  * these states, because it is currently active.
  131                  */
  132                 panic("bad state for thread unlinking");
  133                 /* NOTREACHED */
  134         case TDS_INACTIVE:
  135                 break;
  136         default:
  137                 panic("bad thread state");
  138                 /* NOTREACHED */
  139         }
  140 #endif
  141 #ifdef AUDIT
  142         audit_thread_free(td);
  143 #endif
  144         /* Free all OSD associated to this thread. */
  145         osd_thread_exit(td);
  146 
  147         EVENTHANDLER_INVOKE(thread_dtor, td);
  148         free_unr(tid_unrhdr, td->td_tid);
  149 }
  150 
  151 /*
  152  * Initialize type-stable parts of a thread (when newly created).
  153  */
  154 static int
  155 thread_init(void *mem, int size, int flags)
  156 {
  157         struct thread *td;
  158 
  159         td = (struct thread *)mem;
  160 
  161         td->td_sleepqueue = sleepq_alloc();
  162         td->td_turnstile = turnstile_alloc();
  163         EVENTHANDLER_INVOKE(thread_init, td);
  164         td->td_sched = (struct td_sched *)&td[1];
  165         umtx_thread_init(td);
  166         td->td_kstack = 0;
  167         return (0);
  168 }
  169 
  170 /*
  171  * Tear down type-stable parts of a thread (just before being discarded).
  172  */
  173 static void
  174 thread_fini(void *mem, int size)
  175 {
  176         struct thread *td;
  177 
  178         td = (struct thread *)mem;
  179         EVENTHANDLER_INVOKE(thread_fini, td);
  180         turnstile_free(td->td_turnstile);
  181         sleepq_free(td->td_sleepqueue);
  182         umtx_thread_fini(td);
  183         seltdfini(td);
  184 }
  185 
  186 /*
  187  * For a newly created process,
  188  * link up all the structures and its initial threads etc.
  189  * called from:
  190  * {arch}/{arch}/machdep.c   ia64_init(), init386() etc.
  191  * proc_dtor() (should go away)
  192  * proc_init()
  193  */
  194 void
  195 proc_linkup0(struct proc *p, struct thread *td)
  196 {
  197         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
  198         proc_linkup(p, td);
  199 }
  200 
  201 void
  202 proc_linkup(struct proc *p, struct thread *td)
  203 {
  204 
  205         sigqueue_init(&p->p_sigqueue, p);
  206         p->p_ksi = ksiginfo_alloc(1);
  207         if (p->p_ksi != NULL) {
  208                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
  209                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
  210         }
  211         LIST_INIT(&p->p_mqnotifier);
  212         p->p_numthreads = 0;
  213         thread_link(td, p);
  214 }
  215 
  216 /*
  217  * Initialize global thread allocation resources.
  218  */
  219 void
  220 threadinit(void)
  221 {
  222 
  223         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
  224         /* leave one number for thread0 */
  225         tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
  226 
  227         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
  228             thread_ctor, thread_dtor, thread_init, thread_fini,
  229             16 - 1, 0);
  230 }
  231 
  232 /*
  233  * Place an unused thread on the zombie list.
  234  * Use the slpq as that must be unused by now.
  235  */
  236 void
  237 thread_zombie(struct thread *td)
  238 {
  239         mtx_lock_spin(&zombie_lock);
  240         TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
  241         mtx_unlock_spin(&zombie_lock);
  242 }
  243 
  244 /*
  245  * Release a thread that has exited after cpu_throw().
  246  */
  247 void
  248 thread_stash(struct thread *td)
  249 {
  250         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
  251         thread_zombie(td);
  252 }
  253 
  254 /*
  255  * Reap zombie resources.
  256  */
  257 void
  258 thread_reap(void)
  259 {
  260         struct thread *td_first, *td_next;
  261 
  262         /*
  263          * Don't even bother to lock if none at this instant,
  264          * we really don't care about the next instant..
  265          */
  266         if (!TAILQ_EMPTY(&zombie_threads)) {
  267                 mtx_lock_spin(&zombie_lock);
  268                 td_first = TAILQ_FIRST(&zombie_threads);
  269                 if (td_first)
  270                         TAILQ_INIT(&zombie_threads);
  271                 mtx_unlock_spin(&zombie_lock);
  272                 while (td_first) {
  273                         td_next = TAILQ_NEXT(td_first, td_slpq);
  274                         if (td_first->td_ucred)
  275                                 crfree(td_first->td_ucred);
  276                         thread_free(td_first);
  277                         td_first = td_next;
  278                 }
  279         }
  280 }
  281 
  282 /*
  283  * Allocate a thread.
  284  */
  285 struct thread *
  286 thread_alloc(int pages)
  287 {
  288         struct thread *td;
  289 
  290         thread_reap(); /* check if any zombies to get */
  291 
  292         td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
  293         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
  294         if (!vm_thread_new(td, pages)) {
  295                 uma_zfree(thread_zone, td);
  296                 return (NULL);
  297         }
  298         cpu_thread_alloc(td);
  299         return (td);
  300 }
  301 
  302 int
  303 thread_alloc_stack(struct thread *td, int pages)
  304 {
  305 
  306         KASSERT(td->td_kstack == 0,
  307             ("thread_alloc_stack called on a thread with kstack"));
  308         if (!vm_thread_new(td, pages))
  309                 return (0);
  310         cpu_thread_alloc(td);
  311         return (1);
  312 }
  313 
  314 /*
  315  * Deallocate a thread.
  316  */
  317 void
  318 thread_free(struct thread *td)
  319 {
  320 
  321         lock_profile_thread_exit(td);
  322         if (td->td_cpuset)
  323                 cpuset_rel(td->td_cpuset);
  324         td->td_cpuset = NULL;
  325         cpu_thread_free(td);
  326         if (td->td_kstack != 0)
  327                 vm_thread_dispose(td);
  328         uma_zfree(thread_zone, td);
  329 }
  330 
  331 /*
  332  * Discard the current thread and exit from its context.
  333  * Always called with scheduler locked.
  334  *
  335  * Because we can't free a thread while we're operating under its context,
  336  * push the current thread into our CPU's deadthread holder. This means
  337  * we needn't worry about someone else grabbing our context before we
  338  * do a cpu_throw().
  339  */
  340 void
  341 thread_exit(void)
  342 {
  343         uint64_t new_switchtime;
  344         struct thread *td;
  345         struct thread *td2;
  346         struct proc *p;
  347         int wakeup_swapper;
  348 
  349         td = curthread;
  350         p = td->td_proc;
  351 
  352         PROC_SLOCK_ASSERT(p, MA_OWNED);
  353         mtx_assert(&Giant, MA_NOTOWNED);
  354 
  355         PROC_LOCK_ASSERT(p, MA_OWNED);
  356         KASSERT(p != NULL, ("thread exiting without a process"));
  357         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
  358             (long)p->p_pid, td->td_name);
  359         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
  360 
  361 #ifdef AUDIT
  362         AUDIT_SYSCALL_EXIT(0, td);
  363 #endif
  364         umtx_thread_exit(td);
  365         /*
  366          * drop FPU & debug register state storage, or any other
  367          * architecture specific resources that
  368          * would not be on a new untouched process.
  369          */
  370         cpu_thread_exit(td);    /* XXXSMP */
  371 
  372         /* Do the same timestamp bookkeeping that mi_switch() would do. */
  373         new_switchtime = cpu_ticks();
  374         p->p_rux.rux_runtime += (new_switchtime - PCPU_GET(switchtime));
  375         PCPU_SET(switchtime, new_switchtime);
  376         PCPU_SET(switchticks, ticks);
  377         PCPU_INC(cnt.v_swtch);
  378         /* Save our resource usage in our process. */
  379         td->td_ru.ru_nvcsw++;
  380         rucollect(&p->p_ru, &td->td_ru);
  381         /*
  382          * The last thread is left attached to the process
  383          * So that the whole bundle gets recycled. Skip
  384          * all this stuff if we never had threads.
  385          * EXIT clears all sign of other threads when
  386          * it goes to single threading, so the last thread always
  387          * takes the short path.
  388          */
  389         if (p->p_flag & P_HADTHREADS) {
  390                 if (p->p_numthreads > 1) {
  391                         thread_unlink(td);
  392                         td2 = FIRST_THREAD_IN_PROC(p);
  393                         sched_exit_thread(td2, td);
  394 
  395                         /*
  396                          * The test below is NOT true if we are the
  397                          * sole exiting thread. P_STOPPED_SNGL is unset
  398                          * in exit1() after it is the only survivor.
  399                          */
  400                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  401                                 if (p->p_numthreads == p->p_suspcount) {
  402                                         thread_lock(p->p_singlethread);
  403                                         wakeup_swapper = thread_unsuspend_one(
  404                                                 p->p_singlethread);
  405                                         thread_unlock(p->p_singlethread);
  406                                         if (wakeup_swapper)
  407                                                 kick_proc0();
  408                                 }
  409                         }
  410 
  411                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
  412                         PCPU_SET(deadthread, td);
  413                 } else {
  414                         /*
  415                          * The last thread is exiting.. but not through exit()
  416                          */
  417                         panic ("thread_exit: Last thread exiting on its own");
  418                 }
  419         } 
  420         PROC_UNLOCK(p);
  421         thread_lock(td);
  422         /* Save our tick information with both the thread and proc locked */
  423         ruxagg(&p->p_rux, td);
  424         PROC_SUNLOCK(p);
  425         td->td_state = TDS_INACTIVE;
  426 #ifdef WITNESS
  427         witness_thread_exit(td);
  428 #endif
  429         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
  430         sched_throw(td);
  431         panic("I'm a teapot!");
  432         /* NOTREACHED */
  433 }
  434 
  435 /*
  436  * Do any thread specific cleanups that may be needed in wait()
  437  * called with Giant, proc and schedlock not held.
  438  */
  439 void
  440 thread_wait(struct proc *p)
  441 {
  442         struct thread *td;
  443 
  444         mtx_assert(&Giant, MA_NOTOWNED);
  445         KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
  446         td = FIRST_THREAD_IN_PROC(p);
  447         /* Lock the last thread so we spin until it exits cpu_throw(). */
  448         thread_lock(td);
  449         thread_unlock(td);
  450         /* Wait for any remaining threads to exit cpu_throw(). */
  451         while (p->p_exitthreads)
  452                 sched_relinquish(curthread);
  453         lock_profile_thread_exit(td);
  454         cpuset_rel(td->td_cpuset);
  455         td->td_cpuset = NULL;
  456         cpu_thread_clean(td);
  457         crfree(td->td_ucred);
  458         thread_reap();  /* check for zombie threads etc. */
  459 }
  460 
  461 /*
  462  * Link a thread to a process.
  463  * set up anything that needs to be initialized for it to
  464  * be used by the process.
  465  */
  466 void
  467 thread_link(struct thread *td, struct proc *p)
  468 {
  469 
  470         /*
  471          * XXX This can't be enabled because it's called for proc0 before
  472          * its lock has been created.
  473          * PROC_LOCK_ASSERT(p, MA_OWNED);
  474          */
  475         td->td_state    = TDS_INACTIVE;
  476         td->td_proc     = p;
  477         td->td_flags    = TDF_INMEM;
  478 
  479         LIST_INIT(&td->td_contested);
  480         LIST_INIT(&td->td_lprof[0]);
  481         LIST_INIT(&td->td_lprof[1]);
  482         sigqueue_init(&td->td_sigqueue, p);
  483         callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
  484         TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
  485         p->p_numthreads++;
  486 }
  487 
  488 /*
  489  * Convert a process with one thread to an unthreaded process.
  490  */
  491 void
  492 thread_unthread(struct thread *td)
  493 {
  494         struct proc *p = td->td_proc;
  495 
  496         KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
  497         p->p_flag &= ~P_HADTHREADS;
  498 }
  499 
  500 /*
  501  * Called from:
  502  *  thread_exit()
  503  */
  504 void
  505 thread_unlink(struct thread *td)
  506 {
  507         struct proc *p = td->td_proc;
  508 
  509         PROC_LOCK_ASSERT(p, MA_OWNED);
  510         TAILQ_REMOVE(&p->p_threads, td, td_plist);
  511         p->p_numthreads--;
  512         /* could clear a few other things here */
  513         /* Must  NOT clear links to proc! */
  514 }
  515 
  516 static int
  517 calc_remaining(struct proc *p, int mode)
  518 {
  519         int remaining;
  520 
  521         if (mode == SINGLE_EXIT)
  522                 remaining = p->p_numthreads;
  523         else if (mode == SINGLE_BOUNDARY)
  524                 remaining = p->p_numthreads - p->p_boundary_count;
  525         else if (mode == SINGLE_NO_EXIT)
  526                 remaining = p->p_numthreads - p->p_suspcount;
  527         else
  528                 panic("calc_remaining: wrong mode %d", mode);
  529         return (remaining);
  530 }
  531 
  532 /*
  533  * Enforce single-threading.
  534  *
  535  * Returns 1 if the caller must abort (another thread is waiting to
  536  * exit the process or similar). Process is locked!
  537  * Returns 0 when you are successfully the only thread running.
  538  * A process has successfully single threaded in the suspend mode when
  539  * There are no threads in user mode. Threads in the kernel must be
  540  * allowed to continue until they get to the user boundary. They may even
  541  * copy out their return values and data before suspending. They may however be
  542  * accelerated in reaching the user boundary as we will wake up
  543  * any sleeping threads that are interruptable. (PCATCH).
  544  */
  545 int
  546 thread_single(int mode)
  547 {
  548         struct thread *td;
  549         struct thread *td2;
  550         struct proc *p;
  551         int remaining, wakeup_swapper;
  552 
  553         td = curthread;
  554         p = td->td_proc;
  555         mtx_assert(&Giant, MA_NOTOWNED);
  556         PROC_LOCK_ASSERT(p, MA_OWNED);
  557         KASSERT((td != NULL), ("curthread is NULL"));
  558 
  559         if ((p->p_flag & P_HADTHREADS) == 0)
  560                 return (0);
  561 
  562         /* Is someone already single threading? */
  563         if (p->p_singlethread != NULL && p->p_singlethread != td)
  564                 return (1);
  565 
  566         if (mode == SINGLE_EXIT) {
  567                 p->p_flag |= P_SINGLE_EXIT;
  568                 p->p_flag &= ~P_SINGLE_BOUNDARY;
  569         } else {
  570                 p->p_flag &= ~P_SINGLE_EXIT;
  571                 if (mode == SINGLE_BOUNDARY)
  572                         p->p_flag |= P_SINGLE_BOUNDARY;
  573                 else
  574                         p->p_flag &= ~P_SINGLE_BOUNDARY;
  575         }
  576         p->p_flag |= P_STOPPED_SINGLE;
  577         PROC_SLOCK(p);
  578         p->p_singlethread = td;
  579         remaining = calc_remaining(p, mode);
  580         while (remaining != 1) {
  581                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
  582                         goto stopme;
  583                 wakeup_swapper = 0;
  584                 FOREACH_THREAD_IN_PROC(p, td2) {
  585                         if (td2 == td)
  586                                 continue;
  587                         thread_lock(td2);
  588                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
  589                         if (TD_IS_INHIBITED(td2)) {
  590                                 switch (mode) {
  591                                 case SINGLE_EXIT:
  592                                         if (TD_IS_SUSPENDED(td2))
  593                                                 wakeup_swapper |=
  594                                                     thread_unsuspend_one(td2);
  595                                         if (TD_ON_SLEEPQ(td2) &&
  596                                             (td2->td_flags & TDF_SINTR))
  597                                                 wakeup_swapper |=
  598                                                     sleepq_abort(td2, EINTR);
  599                                         break;
  600                                 case SINGLE_BOUNDARY:
  601                                         if (TD_IS_SUSPENDED(td2) &&
  602                                             !(td2->td_flags & TDF_BOUNDARY))
  603                                                 wakeup_swapper |=
  604                                                     thread_unsuspend_one(td2);
  605                                         if (TD_ON_SLEEPQ(td2) &&
  606                                             (td2->td_flags & TDF_SINTR))
  607                                                 wakeup_swapper |=
  608                                                     sleepq_abort(td2, ERESTART);
  609                                         break;
  610                                 case SINGLE_NO_EXIT:
  611                                         if (TD_IS_SUSPENDED(td2) &&
  612                                             !(td2->td_flags & TDF_BOUNDARY))
  613                                                 wakeup_swapper |=
  614                                                     thread_unsuspend_one(td2);
  615                                         if (TD_ON_SLEEPQ(td2) &&
  616                                             (td2->td_flags & TDF_SINTR))
  617                                                 wakeup_swapper |=
  618                                                     sleepq_abort(td2, ERESTART);
  619                                         break;
  620                                 default:
  621                                         break;
  622                                 }
  623                         }
  624 #ifdef SMP
  625                         else if (TD_IS_RUNNING(td2) && td != td2) {
  626                                 forward_signal(td2);
  627                         }
  628 #endif
  629                         thread_unlock(td2);
  630                 }
  631                 if (wakeup_swapper)
  632                         kick_proc0();
  633                 remaining = calc_remaining(p, mode);
  634 
  635                 /*
  636                  * Maybe we suspended some threads.. was it enough?
  637                  */
  638                 if (remaining == 1)
  639                         break;
  640 
  641 stopme:
  642                 /*
  643                  * Wake us up when everyone else has suspended.
  644                  * In the mean time we suspend as well.
  645                  */
  646                 thread_suspend_switch(td);
  647                 remaining = calc_remaining(p, mode);
  648         }
  649         if (mode == SINGLE_EXIT) {
  650                 /*
  651                  * We have gotten rid of all the other threads and we
  652                  * are about to either exit or exec. In either case,
  653                  * we try our utmost  to revert to being a non-threaded
  654                  * process.
  655                  */
  656                 p->p_singlethread = NULL;
  657                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
  658                 thread_unthread(td);
  659         }
  660         PROC_SUNLOCK(p);
  661         return (0);
  662 }
  663 
  664 /*
  665  * Called in from locations that can safely check to see
  666  * whether we have to suspend or at least throttle for a
  667  * single-thread event (e.g. fork).
  668  *
  669  * Such locations include userret().
  670  * If the "return_instead" argument is non zero, the thread must be able to
  671  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
  672  *
  673  * The 'return_instead' argument tells the function if it may do a
  674  * thread_exit() or suspend, or whether the caller must abort and back
  675  * out instead.
  676  *
  677  * If the thread that set the single_threading request has set the
  678  * P_SINGLE_EXIT bit in the process flags then this call will never return
  679  * if 'return_instead' is false, but will exit.
  680  *
  681  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
  682  *---------------+--------------------+---------------------
  683  *       0       | returns 0          |   returns 0 or 1
  684  *               | when ST ends       |   immediatly
  685  *---------------+--------------------+---------------------
  686  *       1       | thread exits       |   returns 1
  687  *               |                    |  immediatly
  688  * 0 = thread_exit() or suspension ok,
  689  * other = return error instead of stopping the thread.
  690  *
  691  * While a full suspension is under effect, even a single threading
  692  * thread would be suspended if it made this call (but it shouldn't).
  693  * This call should only be made from places where
  694  * thread_exit() would be safe as that may be the outcome unless
  695  * return_instead is set.
  696  */
  697 int
  698 thread_suspend_check(int return_instead)
  699 {
  700         struct thread *td;
  701         struct proc *p;
  702         int wakeup_swapper;
  703 
  704         td = curthread;
  705         p = td->td_proc;
  706         mtx_assert(&Giant, MA_NOTOWNED);
  707         PROC_LOCK_ASSERT(p, MA_OWNED);
  708         while (P_SHOULDSTOP(p) ||
  709               ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
  710                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  711                         KASSERT(p->p_singlethread != NULL,
  712                             ("singlethread not set"));
  713                         /*
  714                          * The only suspension in action is a
  715                          * single-threading. Single threader need not stop.
  716                          * XXX Should be safe to access unlocked
  717                          * as it can only be set to be true by us.
  718                          */
  719                         if (p->p_singlethread == td)
  720                                 return (0);     /* Exempt from stopping. */
  721                 }
  722                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
  723                         return (EINTR);
  724 
  725                 /* Should we goto user boundary if we didn't come from there? */
  726                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
  727                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
  728                         return (ERESTART);
  729 
  730                 /* If thread will exit, flush its pending signals */
  731                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td))
  732                         sigqueue_flush(&td->td_sigqueue);
  733 
  734                 PROC_SLOCK(p);
  735                 thread_stopped(p);
  736                 /*
  737                  * If the process is waiting for us to exit,
  738                  * this thread should just suicide.
  739                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
  740                  */
  741                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td))
  742                         thread_exit();
  743                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  744                         if (p->p_numthreads == p->p_suspcount + 1) {
  745                                 thread_lock(p->p_singlethread);
  746                                 wakeup_swapper =
  747                                     thread_unsuspend_one(p->p_singlethread);
  748                                 thread_unlock(p->p_singlethread);
  749                                 if (wakeup_swapper)
  750                                         kick_proc0();
  751                         }
  752                 }
  753                 PROC_UNLOCK(p);
  754                 thread_lock(td);
  755                 /*
  756                  * When a thread suspends, it just
  757                  * gets taken off all queues.
  758                  */
  759                 thread_suspend_one(td);
  760                 if (return_instead == 0) {
  761                         p->p_boundary_count++;
  762                         td->td_flags |= TDF_BOUNDARY;
  763                 }
  764                 PROC_SUNLOCK(p);
  765                 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
  766                 if (return_instead == 0)
  767                         td->td_flags &= ~TDF_BOUNDARY;
  768                 thread_unlock(td);
  769                 PROC_LOCK(p);
  770                 if (return_instead == 0)
  771                         p->p_boundary_count--;
  772         }
  773         return (0);
  774 }
  775 
  776 void
  777 thread_suspend_switch(struct thread *td)
  778 {
  779         struct proc *p;
  780 
  781         p = td->td_proc;
  782         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
  783         PROC_LOCK_ASSERT(p, MA_OWNED);
  784         PROC_SLOCK_ASSERT(p, MA_OWNED);
  785         /*
  786          * We implement thread_suspend_one in stages here to avoid
  787          * dropping the proc lock while the thread lock is owned.
  788          */
  789         thread_stopped(p);
  790         p->p_suspcount++;
  791         PROC_UNLOCK(p);
  792         thread_lock(td);
  793         td->td_flags &= ~TDF_NEEDSUSPCHK;
  794         TD_SET_SUSPENDED(td);
  795         sched_sleep(td, 0);
  796         PROC_SUNLOCK(p);
  797         DROP_GIANT();
  798         mi_switch(SW_VOL | SWT_SUSPEND, NULL);
  799         thread_unlock(td);
  800         PICKUP_GIANT();
  801         PROC_LOCK(p);
  802         PROC_SLOCK(p);
  803 }
  804 
  805 void
  806 thread_suspend_one(struct thread *td)
  807 {
  808         struct proc *p = td->td_proc;
  809 
  810         PROC_SLOCK_ASSERT(p, MA_OWNED);
  811         THREAD_LOCK_ASSERT(td, MA_OWNED);
  812         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
  813         p->p_suspcount++;
  814         td->td_flags &= ~TDF_NEEDSUSPCHK;
  815         TD_SET_SUSPENDED(td);
  816         sched_sleep(td, 0);
  817 }
  818 
  819 int
  820 thread_unsuspend_one(struct thread *td)
  821 {
  822         struct proc *p = td->td_proc;
  823 
  824         PROC_SLOCK_ASSERT(p, MA_OWNED);
  825         THREAD_LOCK_ASSERT(td, MA_OWNED);
  826         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
  827         TD_CLR_SUSPENDED(td);
  828         p->p_suspcount--;
  829         return (setrunnable(td));
  830 }
  831 
  832 /*
  833  * Allow all threads blocked by single threading to continue running.
  834  */
  835 void
  836 thread_unsuspend(struct proc *p)
  837 {
  838         struct thread *td;
  839         int wakeup_swapper;
  840 
  841         PROC_LOCK_ASSERT(p, MA_OWNED);
  842         PROC_SLOCK_ASSERT(p, MA_OWNED);
  843         wakeup_swapper = 0;
  844         if (!P_SHOULDSTOP(p)) {
  845                 FOREACH_THREAD_IN_PROC(p, td) {
  846                         thread_lock(td);
  847                         if (TD_IS_SUSPENDED(td)) {
  848                                 wakeup_swapper |= thread_unsuspend_one(td);
  849                         }
  850                         thread_unlock(td);
  851                 }
  852         } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
  853             (p->p_numthreads == p->p_suspcount)) {
  854                 /*
  855                  * Stopping everything also did the job for the single
  856                  * threading request. Now we've downgraded to single-threaded,
  857                  * let it continue.
  858                  */
  859                 thread_lock(p->p_singlethread);
  860                 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
  861                 thread_unlock(p->p_singlethread);
  862         }
  863         if (wakeup_swapper)
  864                 kick_proc0();
  865 }
  866 
  867 /*
  868  * End the single threading mode..
  869  */
  870 void
  871 thread_single_end(void)
  872 {
  873         struct thread *td;
  874         struct proc *p;
  875         int wakeup_swapper;
  876 
  877         td = curthread;
  878         p = td->td_proc;
  879         PROC_LOCK_ASSERT(p, MA_OWNED);
  880         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
  881         PROC_SLOCK(p);
  882         p->p_singlethread = NULL;
  883         wakeup_swapper = 0;
  884         /*
  885          * If there are other threads they may now run,
  886          * unless of course there is a blanket 'stop order'
  887          * on the process. The single threader must be allowed
  888          * to continue however as this is a bad place to stop.
  889          */
  890         if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
  891                 FOREACH_THREAD_IN_PROC(p, td) {
  892                         thread_lock(td);
  893                         if (TD_IS_SUSPENDED(td)) {
  894                                 wakeup_swapper |= thread_unsuspend_one(td);
  895                         }
  896                         thread_unlock(td);
  897                 }
  898         }
  899         PROC_SUNLOCK(p);
  900         if (wakeup_swapper)
  901                 kick_proc0();
  902 }
  903 
  904 struct thread *
  905 thread_find(struct proc *p, lwpid_t tid)
  906 {
  907         struct thread *td;
  908 
  909         PROC_LOCK_ASSERT(p, MA_OWNED);
  910         FOREACH_THREAD_IN_PROC(p, td) {
  911                 if (td->td_tid == tid)
  912                         break;
  913         }
  914         return (td);
  915 }
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_thread.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_thread.c
