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 #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);
   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_head + 1) % 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_tail + 1) % 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         td->td_vp_reserv = 0;
  211         EVENTHANDLER_INVOKE(thread_init, td);
  212         td->td_sched = (struct td_sched *)&td[1];
  213         umtx_thread_init(td);
  214         td->td_kstack = 0;
  215         td->td_sel = NULL;
  216         return (0);
  217 }
  218 
  219 /*
  220  * Tear down type-stable parts of a thread (just before being discarded).
  221  */
  222 static void
  223 thread_fini(void *mem, int size)
  224 {
  225         struct thread *td;
  226 
  227         td = (struct thread *)mem;
  228         EVENTHANDLER_INVOKE(thread_fini, td);
  229         rlqentry_free(td->td_rlqe);
  230         turnstile_free(td->td_turnstile);
  231         sleepq_free(td->td_sleepqueue);
  232         umtx_thread_fini(td);
  233         seltdfini(td);
  234 }
  235 
  236 /*
  237  * For a newly created process,
  238  * link up all the structures and its initial threads etc.
  239  * called from:
  240  * {arch}/{arch}/machdep.c   ia64_init(), init386() etc.
  241  * proc_dtor() (should go away)
  242  * proc_init()
  243  */
  244 void
  245 proc_linkup0(struct proc *p, struct thread *td)
  246 {
  247         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
  248         proc_linkup(p, td);
  249 }
  250 
  251 void
  252 proc_linkup(struct proc *p, struct thread *td)
  253 {
  254 
  255         sigqueue_init(&p->p_sigqueue, p);
  256         p->p_ksi = ksiginfo_alloc(1);
  257         if (p->p_ksi != NULL) {
  258                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
  259                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
  260         }
  261         LIST_INIT(&p->p_mqnotifier);
  262         p->p_numthreads = 0;
  263         thread_link(td, p);
  264 }
  265 
  266 /*
  267  * Initialize global thread allocation resources.
  268  */
  269 void
  270 threadinit(void)
  271 {
  272 
  273         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
  274 
  275         /*
  276          * pid_max cannot be greater than PID_MAX.
  277          * leave one number for thread0.
  278          */
  279         tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
  280 
  281         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
  282             thread_ctor, thread_dtor, thread_init, thread_fini,
  283             16 - 1, 0);
  284         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
  285         rw_init(&tidhash_lock, "tidhash");
  286 }
  287 
  288 /*
  289  * Place an unused thread on the zombie list.
  290  * Use the slpq as that must be unused by now.
  291  */
  292 void
  293 thread_zombie(struct thread *td)
  294 {
  295         mtx_lock_spin(&zombie_lock);
  296         TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
  297         mtx_unlock_spin(&zombie_lock);
  298 }
  299 
  300 /*
  301  * Release a thread that has exited after cpu_throw().
  302  */
  303 void
  304 thread_stash(struct thread *td)
  305 {
  306         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
  307         thread_zombie(td);
  308 }
  309 
  310 /*
  311  * Reap zombie resources.
  312  */
  313 void
  314 thread_reap(void)
  315 {
  316         struct thread *td_first, *td_next;
  317 
  318         /*
  319          * Don't even bother to lock if none at this instant,
  320          * we really don't care about the next instant..
  321          */
  322         if (!TAILQ_EMPTY(&zombie_threads)) {
  323                 mtx_lock_spin(&zombie_lock);
  324                 td_first = TAILQ_FIRST(&zombie_threads);
  325                 if (td_first)
  326                         TAILQ_INIT(&zombie_threads);
  327                 mtx_unlock_spin(&zombie_lock);
  328                 while (td_first) {
  329                         td_next = TAILQ_NEXT(td_first, td_slpq);
  330                         if (td_first->td_ucred)
  331                                 crfree(td_first->td_ucred);
  332                         thread_free(td_first);
  333                         td_first = td_next;
  334                 }
  335         }
  336 }
  337 
  338 /*
  339  * Allocate a thread.
  340  */
  341 struct thread *
  342 thread_alloc(int pages)
  343 {
  344         struct thread *td;
  345 
  346         thread_reap(); /* check if any zombies to get */
  347 
  348         td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
  349         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
  350         if (!vm_thread_new(td, pages)) {
  351                 uma_zfree(thread_zone, td);
  352                 return (NULL);
  353         }
  354         cpu_thread_alloc(td);
  355         return (td);
  356 }
  357 
  358 int
  359 thread_alloc_stack(struct thread *td, int pages)
  360 {
  361 
  362         KASSERT(td->td_kstack == 0,
  363             ("thread_alloc_stack called on a thread with kstack"));
  364         if (!vm_thread_new(td, pages))
  365                 return (0);
  366         cpu_thread_alloc(td);
  367         return (1);
  368 }
  369 
  370 /*
  371  * Deallocate a thread.
  372  */
  373 void
  374 thread_free(struct thread *td)
  375 {
  376 
  377         lock_profile_thread_exit(td);
  378         if (td->td_cpuset)
  379                 cpuset_rel(td->td_cpuset);
  380         td->td_cpuset = NULL;
  381         cpu_thread_free(td);
  382         if (td->td_kstack != 0)
  383                 vm_thread_dispose(td);
  384         uma_zfree(thread_zone, td);
  385 }
  386 
  387 /*
  388  * Discard the current thread and exit from its context.
  389  * Always called with scheduler locked.
  390  *
  391  * Because we can't free a thread while we're operating under its context,
  392  * push the current thread into our CPU's deadthread holder. This means
  393  * we needn't worry about someone else grabbing our context before we
  394  * do a cpu_throw().
  395  */
  396 void
  397 thread_exit(void)
  398 {
  399         uint64_t runtime, new_switchtime;
  400         struct thread *td;
  401         struct thread *td2;
  402         struct proc *p;
  403         int wakeup_swapper;
  404 
  405         td = curthread;
  406         p = td->td_proc;
  407 
  408         PROC_SLOCK_ASSERT(p, MA_OWNED);
  409         mtx_assert(&Giant, MA_NOTOWNED);
  410 
  411         PROC_LOCK_ASSERT(p, MA_OWNED);
  412         KASSERT(p != NULL, ("thread exiting without a process"));
  413         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
  414             (long)p->p_pid, td->td_name);
  415         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
  416 
  417 #ifdef AUDIT
  418         AUDIT_SYSCALL_EXIT(0, td);
  419 #endif
  420         umtx_thread_exit(td);
  421         /*
  422          * drop FPU & debug register state storage, or any other
  423          * architecture specific resources that
  424          * would not be on a new untouched process.
  425          */
  426         cpu_thread_exit(td);    /* XXXSMP */
  427 
  428         /*
  429          * The last thread is left attached to the process
  430          * So that the whole bundle gets recycled. Skip
  431          * all this stuff if we never had threads.
  432          * EXIT clears all sign of other threads when
  433          * it goes to single threading, so the last thread always
  434          * takes the short path.
  435          */
  436         if (p->p_flag & P_HADTHREADS) {
  437                 if (p->p_numthreads > 1) {
  438                         thread_unlink(td);
  439                         td2 = FIRST_THREAD_IN_PROC(p);
  440                         sched_exit_thread(td2, td);
  441 
  442                         /*
  443                          * The test below is NOT true if we are the
  444                          * sole exiting thread. P_STOPPED_SINGLE is unset
  445                          * in exit1() after it is the only survivor.
  446                          */
  447                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  448                                 if (p->p_numthreads == p->p_suspcount) {
  449                                         thread_lock(p->p_singlethread);
  450                                         wakeup_swapper = thread_unsuspend_one(
  451                                                 p->p_singlethread);
  452                                         thread_unlock(p->p_singlethread);
  453                                         if (wakeup_swapper)
  454                                                 kick_proc0();
  455                                 }
  456                         }
  457 
  458                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
  459                         PCPU_SET(deadthread, td);
  460                 } else {
  461                         /*
  462                          * The last thread is exiting.. but not through exit()
  463                          */
  464                         panic ("thread_exit: Last thread exiting on its own");
  465                 }
  466         } 
  467 #ifdef  HWPMC_HOOKS
  468         /*
  469          * If this thread is part of a process that is being tracked by hwpmc(4),
  470          * inform the module of the thread's impending exit.
  471          */
  472         if (PMC_PROC_IS_USING_PMCS(td->td_proc))
  473                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
  474 #endif
  475         PROC_UNLOCK(p);
  476 
  477         /* Do the same timestamp bookkeeping that mi_switch() would do. */
  478         new_switchtime = cpu_ticks();
  479         runtime = new_switchtime - PCPU_GET(switchtime);
  480         td->td_runtime += runtime;
  481         td->td_incruntime += runtime;
  482         PCPU_SET(switchtime, new_switchtime);
  483         PCPU_SET(switchticks, ticks);
  484         PCPU_INC(cnt.v_swtch);
  485 
  486         /* Save our resource usage in our process. */
  487         td->td_ru.ru_nvcsw++;
  488         ruxagg(p, td);
  489         rucollect(&p->p_ru, &td->td_ru);
  490 
  491         thread_lock(td);
  492         PROC_SUNLOCK(p);
  493         td->td_state = TDS_INACTIVE;
  494 #ifdef WITNESS
  495         witness_thread_exit(td);
  496 #endif
  497         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
  498         sched_throw(td);
  499         panic("I'm a teapot!");
  500         /* NOTREACHED */
  501 }
  502 
  503 /*
  504  * Do any thread specific cleanups that may be needed in wait()
  505  * called with Giant, proc and schedlock not held.
  506  */
  507 void
  508 thread_wait(struct proc *p)
  509 {
  510         struct thread *td;
  511 
  512         mtx_assert(&Giant, MA_NOTOWNED);
  513         KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
  514         td = FIRST_THREAD_IN_PROC(p);
  515         /* Lock the last thread so we spin until it exits cpu_throw(). */
  516         thread_lock(td);
  517         thread_unlock(td);
  518         /* Wait for any remaining threads to exit cpu_throw(). */
  519         while (p->p_exitthreads)
  520                 sched_relinquish(curthread);
  521         lock_profile_thread_exit(td);
  522         cpuset_rel(td->td_cpuset);
  523         td->td_cpuset = NULL;
  524         cpu_thread_clean(td);
  525         crfree(td->td_ucred);
  526         thread_reap();  /* check for zombie threads etc. */
  527 }
  528 
  529 /*
  530  * Link a thread to a process.
  531  * set up anything that needs to be initialized for it to
  532  * be used by the process.
  533  */
  534 void
  535 thread_link(struct thread *td, struct proc *p)
  536 {
  537 
  538         /*
  539          * XXX This can't be enabled because it's called for proc0 before
  540          * its lock has been created.
  541          * PROC_LOCK_ASSERT(p, MA_OWNED);
  542          */
  543         td->td_state    = TDS_INACTIVE;
  544         td->td_proc     = p;
  545         td->td_flags    = TDF_INMEM;
  546 
  547         LIST_INIT(&td->td_contested);
  548         LIST_INIT(&td->td_lprof[0]);
  549         LIST_INIT(&td->td_lprof[1]);
  550         sigqueue_init(&td->td_sigqueue, p);
  551         callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
  552         TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
  553         p->p_numthreads++;
  554 }
  555 
  556 /*
  557  * Convert a process with one thread to an unthreaded process.
  558  */
  559 void
  560 thread_unthread(struct thread *td)
  561 {
  562         struct proc *p = td->td_proc;
  563 
  564         KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
  565         p->p_flag &= ~P_HADTHREADS;
  566 }
  567 
  568 /*
  569  * Called from:
  570  *  thread_exit()
  571  */
  572 void
  573 thread_unlink(struct thread *td)
  574 {
  575         struct proc *p = td->td_proc;
  576 
  577         PROC_LOCK_ASSERT(p, MA_OWNED);
  578         TAILQ_REMOVE(&p->p_threads, td, td_plist);
  579         p->p_numthreads--;
  580         /* could clear a few other things here */
  581         /* Must  NOT clear links to proc! */
  582 }
  583 
  584 static int
  585 calc_remaining(struct proc *p, int mode)
  586 {
  587         int remaining;
  588 
  589         PROC_LOCK_ASSERT(p, MA_OWNED);
  590         PROC_SLOCK_ASSERT(p, MA_OWNED);
  591         if (mode == SINGLE_EXIT)
  592                 remaining = p->p_numthreads;
  593         else if (mode == SINGLE_BOUNDARY)
  594                 remaining = p->p_numthreads - p->p_boundary_count;
  595         else if (mode == SINGLE_NO_EXIT)
  596                 remaining = p->p_numthreads - p->p_suspcount;
  597         else
  598                 panic("calc_remaining: wrong mode %d", mode);
  599         return (remaining);
  600 }
  601 
  602 /*
  603  * Enforce single-threading.
  604  *
  605  * Returns 1 if the caller must abort (another thread is waiting to
  606  * exit the process or similar). Process is locked!
  607  * Returns 0 when you are successfully the only thread running.
  608  * A process has successfully single threaded in the suspend mode when
  609  * There are no threads in user mode. Threads in the kernel must be
  610  * allowed to continue until they get to the user boundary. They may even
  611  * copy out their return values and data before suspending. They may however be
  612  * accelerated in reaching the user boundary as we will wake up
  613  * any sleeping threads that are interruptable. (PCATCH).
  614  */
  615 int
  616 thread_single(int mode)
  617 {
  618         struct thread *td;
  619         struct thread *td2;
  620         struct proc *p;
  621         int remaining, wakeup_swapper;
  622 
  623         td = curthread;
  624         p = td->td_proc;
  625         mtx_assert(&Giant, MA_NOTOWNED);
  626         PROC_LOCK_ASSERT(p, MA_OWNED);
  627 
  628         if ((p->p_flag & P_HADTHREADS) == 0)
  629                 return (0);
  630 
  631         /* Is someone already single threading? */
  632         if (p->p_singlethread != NULL && p->p_singlethread != td)
  633                 return (1);
  634 
  635         if (mode == SINGLE_EXIT) {
  636                 p->p_flag |= P_SINGLE_EXIT;
  637                 p->p_flag &= ~P_SINGLE_BOUNDARY;
  638         } else {
  639                 p->p_flag &= ~P_SINGLE_EXIT;
  640                 if (mode == SINGLE_BOUNDARY)
  641                         p->p_flag |= P_SINGLE_BOUNDARY;
  642                 else
  643                         p->p_flag &= ~P_SINGLE_BOUNDARY;
  644         }
  645         p->p_flag |= P_STOPPED_SINGLE;
  646         PROC_SLOCK(p);
  647         p->p_singlethread = td;
  648         remaining = calc_remaining(p, mode);
  649         while (remaining != 1) {
  650                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
  651                         goto stopme;
  652                 wakeup_swapper = 0;
  653                 FOREACH_THREAD_IN_PROC(p, td2) {
  654                         if (td2 == td)
  655                                 continue;
  656                         thread_lock(td2);
  657                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
  658                         if (TD_IS_INHIBITED(td2)) {
  659                                 switch (mode) {
  660                                 case SINGLE_EXIT:
  661                                         if (TD_IS_SUSPENDED(td2))
  662                                                 wakeup_swapper |=
  663                                                     thread_unsuspend_one(td2);
  664                                         if (TD_ON_SLEEPQ(td2) &&
  665                                             (td2->td_flags & TDF_SINTR))
  666                                                 wakeup_swapper |=
  667                                                     sleepq_abort(td2, EINTR);
  668                                         break;
  669                                 case SINGLE_BOUNDARY:
  670                                         if (TD_IS_SUSPENDED(td2) &&
  671                                             !(td2->td_flags & TDF_BOUNDARY))
  672                                                 wakeup_swapper |=
  673                                                     thread_unsuspend_one(td2);
  674                                         if (TD_ON_SLEEPQ(td2) &&
  675                                             (td2->td_flags & TDF_SINTR))
  676                                                 wakeup_swapper |=
  677                                                     sleepq_abort(td2, ERESTART);
  678                                         break;
  679                                 case SINGLE_NO_EXIT:
  680                                         if (TD_IS_SUSPENDED(td2) &&
  681                                             !(td2->td_flags & TDF_BOUNDARY))
  682                                                 wakeup_swapper |=
  683                                                     thread_unsuspend_one(td2);
  684                                         if (TD_ON_SLEEPQ(td2) &&
  685                                             (td2->td_flags & TDF_SINTR))
  686                                                 wakeup_swapper |=
  687                                                     sleepq_abort(td2, ERESTART);
  688                                         break;
  689                                 default:
  690                                         break;
  691                                 }
  692                         }
  693 #ifdef SMP
  694                         else if (TD_IS_RUNNING(td2) && td != td2) {
  695                                 forward_signal(td2);
  696                         }
  697 #endif
  698                         thread_unlock(td2);
  699                 }
  700                 if (wakeup_swapper)
  701                         kick_proc0();
  702                 remaining = calc_remaining(p, mode);
  703 
  704                 /*
  705                  * Maybe we suspended some threads.. was it enough?
  706                  */
  707                 if (remaining == 1)
  708                         break;
  709 
  710 stopme:
  711                 /*
  712                  * Wake us up when everyone else has suspended.
  713                  * In the mean time we suspend as well.
  714                  */
  715                 thread_suspend_switch(td);
  716                 remaining = calc_remaining(p, mode);
  717         }
  718         if (mode == SINGLE_EXIT) {
  719                 /*
  720                  * We have gotten rid of all the other threads and we
  721                  * are about to either exit or exec. In either case,
  722                  * we try our utmost  to revert to being a non-threaded
  723                  * process.
  724                  */
  725                 p->p_singlethread = NULL;
  726                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
  727                 thread_unthread(td);
  728         }
  729         PROC_SUNLOCK(p);
  730         return (0);
  731 }
  732 
  733 /*
  734  * Called in from locations that can safely check to see
  735  * whether we have to suspend or at least throttle for a
  736  * single-thread event (e.g. fork).
  737  *
  738  * Such locations include userret().
  739  * If the "return_instead" argument is non zero, the thread must be able to
  740  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
  741  *
  742  * The 'return_instead' argument tells the function if it may do a
  743  * thread_exit() or suspend, or whether the caller must abort and back
  744  * out instead.
  745  *
  746  * If the thread that set the single_threading request has set the
  747  * P_SINGLE_EXIT bit in the process flags then this call will never return
  748  * if 'return_instead' is false, but will exit.
  749  *
  750  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
  751  *---------------+--------------------+---------------------
  752  *       0       | returns 0          |   returns 0 or 1
  753  *               | when ST ends       |   immediatly
  754  *---------------+--------------------+---------------------
  755  *       1       | thread exits       |   returns 1
  756  *               |                    |  immediatly
  757  * 0 = thread_exit() or suspension ok,
  758  * other = return error instead of stopping the thread.
  759  *
  760  * While a full suspension is under effect, even a single threading
  761  * thread would be suspended if it made this call (but it shouldn't).
  762  * This call should only be made from places where
  763  * thread_exit() would be safe as that may be the outcome unless
  764  * return_instead is set.
  765  */
  766 int
  767 thread_suspend_check(int return_instead)
  768 {
  769         struct thread *td;
  770         struct proc *p;
  771         int wakeup_swapper;
  772 
  773         td = curthread;
  774         p = td->td_proc;
  775         mtx_assert(&Giant, MA_NOTOWNED);
  776         PROC_LOCK_ASSERT(p, MA_OWNED);
  777         while (P_SHOULDSTOP(p) ||
  778               ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
  779                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  780                         KASSERT(p->p_singlethread != NULL,
  781                             ("singlethread not set"));
  782                         /*
  783                          * The only suspension in action is a
  784                          * single-threading. Single threader need not stop.
  785                          * XXX Should be safe to access unlocked
  786                          * as it can only be set to be true by us.
  787                          */
  788                         if (p->p_singlethread == td)
  789                                 return (0);     /* Exempt from stopping. */
  790                 }
  791                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
  792                         return (EINTR);
  793 
  794                 /* Should we goto user boundary if we didn't come from there? */
  795                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
  796                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
  797                         return (ERESTART);
  798 
  799                 /*
  800                  * Ignore suspend requests for stop signals if they
  801                  * are deferred.
  802                  */
  803                 if (P_SHOULDSTOP(p) == P_STOPPED_SIG &&
  804                     td->td_flags & TDF_SBDRY) {
  805                         KASSERT(return_instead,
  806                             ("TDF_SBDRY set for unsafe thread_suspend_check"));
  807                         return (0);
  808                 }
  809 
  810                 /*
  811                  * If the process is waiting for us to exit,
  812                  * this thread should just suicide.
  813                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
  814                  */
  815                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
  816                         PROC_UNLOCK(p);
  817                         tidhash_remove(td);
  818                         PROC_LOCK(p);
  819                         tdsigcleanup(td);
  820                         PROC_SLOCK(p);
  821                         thread_stopped(p);
  822                         thread_exit();
  823                 }
  824 
  825                 PROC_SLOCK(p);
  826                 thread_stopped(p);
  827                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  828                         if (p->p_numthreads == p->p_suspcount + 1) {
  829                                 thread_lock(p->p_singlethread);
  830                                 wakeup_swapper =
  831                                     thread_unsuspend_one(p->p_singlethread);
  832                                 thread_unlock(p->p_singlethread);
  833                                 if (wakeup_swapper)
  834                                         kick_proc0();
  835                         }
  836                 }
  837                 PROC_UNLOCK(p);
  838                 thread_lock(td);
  839                 /*
  840                  * When a thread suspends, it just
  841                  * gets taken off all queues.
  842                  */
  843                 thread_suspend_one(td);
  844                 if (return_instead == 0) {
  845                         p->p_boundary_count++;
  846                         td->td_flags |= TDF_BOUNDARY;
  847                 }
  848                 PROC_SUNLOCK(p);
  849                 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
  850                 if (return_instead == 0)
  851                         td->td_flags &= ~TDF_BOUNDARY;
  852                 thread_unlock(td);
  853                 PROC_LOCK(p);
  854                 if (return_instead == 0) {
  855                         PROC_SLOCK(p);
  856                         p->p_boundary_count--;
  857                         PROC_SUNLOCK(p);
  858                 }
  859         }
  860         return (0);
  861 }
  862 
  863 void
  864 thread_suspend_switch(struct thread *td)
  865 {
  866         struct proc *p;
  867 
  868         p = td->td_proc;
  869         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
  870         PROC_LOCK_ASSERT(p, MA_OWNED);
  871         PROC_SLOCK_ASSERT(p, MA_OWNED);
  872         /*
  873          * We implement thread_suspend_one in stages here to avoid
  874          * dropping the proc lock while the thread lock is owned.
  875          */
  876         thread_stopped(p);
  877         p->p_suspcount++;
  878         PROC_UNLOCK(p);
  879         thread_lock(td);
  880         td->td_flags &= ~TDF_NEEDSUSPCHK;
  881         TD_SET_SUSPENDED(td);
  882         sched_sleep(td, 0);
  883         PROC_SUNLOCK(p);
  884         DROP_GIANT();
  885         mi_switch(SW_VOL | SWT_SUSPEND, NULL);
  886         thread_unlock(td);
  887         PICKUP_GIANT();
  888         PROC_LOCK(p);
  889         PROC_SLOCK(p);
  890 }
  891 
  892 void
  893 thread_suspend_one(struct thread *td)
  894 {
  895         struct proc *p = td->td_proc;
  896 
  897         PROC_SLOCK_ASSERT(p, MA_OWNED);
  898         THREAD_LOCK_ASSERT(td, MA_OWNED);
  899         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
  900         p->p_suspcount++;
  901         td->td_flags &= ~TDF_NEEDSUSPCHK;
  902         TD_SET_SUSPENDED(td);
  903         sched_sleep(td, 0);
  904 }
  905 
  906 int
  907 thread_unsuspend_one(struct thread *td)
  908 {
  909         struct proc *p = td->td_proc;
  910 
  911         PROC_SLOCK_ASSERT(p, MA_OWNED);
  912         THREAD_LOCK_ASSERT(td, MA_OWNED);
  913         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
  914         TD_CLR_SUSPENDED(td);
  915         p->p_suspcount--;
  916         return (setrunnable(td));
  917 }
  918 
  919 /*
  920  * Allow all threads blocked by single threading to continue running.
  921  */
  922 void
  923 thread_unsuspend(struct proc *p)
  924 {
  925         struct thread *td;
  926         int wakeup_swapper;
  927 
  928         PROC_LOCK_ASSERT(p, MA_OWNED);
  929         PROC_SLOCK_ASSERT(p, MA_OWNED);
  930         wakeup_swapper = 0;
  931         if (!P_SHOULDSTOP(p)) {
  932                 FOREACH_THREAD_IN_PROC(p, td) {
  933                         thread_lock(td);
  934                         if (TD_IS_SUSPENDED(td)) {
  935                                 wakeup_swapper |= thread_unsuspend_one(td);
  936                         }
  937                         thread_unlock(td);
  938                 }
  939         } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
  940             (p->p_numthreads == p->p_suspcount)) {
  941                 /*
  942                  * Stopping everything also did the job for the single
  943                  * threading request. Now we've downgraded to single-threaded,
  944                  * let it continue.
  945                  */
  946                 thread_lock(p->p_singlethread);
  947                 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
  948                 thread_unlock(p->p_singlethread);
  949         }
  950         if (wakeup_swapper)
  951                 kick_proc0();
  952 }
  953 
  954 /*
  955  * End the single threading mode..
  956  */
  957 void
  958 thread_single_end(void)
  959 {
  960         struct thread *td;
  961         struct proc *p;
  962         int wakeup_swapper;
  963 
  964         td = curthread;
  965         p = td->td_proc;
  966         PROC_LOCK_ASSERT(p, MA_OWNED);
  967         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
  968         PROC_SLOCK(p);
  969         p->p_singlethread = NULL;
  970         wakeup_swapper = 0;
  971         /*
  972          * If there are other threads they may now run,
  973          * unless of course there is a blanket 'stop order'
  974          * on the process. The single threader must be allowed
  975          * to continue however as this is a bad place to stop.
  976          */
  977         if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
  978                 FOREACH_THREAD_IN_PROC(p, td) {
  979                         thread_lock(td);
  980                         if (TD_IS_SUSPENDED(td)) {
  981                                 wakeup_swapper |= thread_unsuspend_one(td);
  982                         }
  983                         thread_unlock(td);
  984                 }
  985         }
  986         PROC_SUNLOCK(p);
  987         if (wakeup_swapper)
  988                 kick_proc0();
  989 }
  990 
  991 struct thread *
  992 thread_find(struct proc *p, lwpid_t tid)
  993 {
  994         struct thread *td;
  995 
  996         PROC_LOCK_ASSERT(p, MA_OWNED);
  997         FOREACH_THREAD_IN_PROC(p, td) {
  998                 if (td->td_tid == tid)
  999                         break;
 1000         }
 1001         return (td);
 1002 }
 1003 
 1004 /* Locate a thread by number; return with proc lock held. */
 1005 struct thread *
 1006 tdfind(lwpid_t tid, pid_t pid)
 1007 {
 1008 #define RUN_THRESH      16
 1009         struct thread *td;
 1010         int run = 0;
 1011 
 1012         rw_rlock(&tidhash_lock);
 1013         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
 1014                 if (td->td_tid == tid) {
 1015                         if (pid != -1 && td->td_proc->p_pid != pid) {
 1016                                 td = NULL;
 1017                                 break;
 1018                         }
 1019                         PROC_LOCK(td->td_proc);
 1020                         if (td->td_proc->p_state == PRS_NEW) {
 1021                                 PROC_UNLOCK(td->td_proc);
 1022                                 td = NULL;
 1023                                 break;
 1024                         }
 1025                         if (run > RUN_THRESH) {
 1026                                 if (rw_try_upgrade(&tidhash_lock)) {
 1027                                         LIST_REMOVE(td, td_hash);
 1028                                         LIST_INSERT_HEAD(TIDHASH(td->td_tid),
 1029                                                 td, td_hash);
 1030                                         rw_wunlock(&tidhash_lock);
 1031                                         return (td);
 1032                                 }
 1033                         }
 1034                         break;
 1035                 }
 1036                 run++;
 1037         }
 1038         rw_runlock(&tidhash_lock);
 1039         return (td);
 1040 }
 1041 
 1042 void
 1043 tidhash_add(struct thread *td)
 1044 {
 1045         rw_wlock(&tidhash_lock);
 1046         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
 1047         rw_wunlock(&tidhash_lock);
 1048 }
 1049 
 1050 void
 1051 tidhash_remove(struct thread *td)
 1052 {
 1053         rw_wlock(&tidhash_lock);
 1054         LIST_REMOVE(td, td_hash);
 1055         rw_wunlock(&tidhash_lock);
 1056 }
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_thread.c

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