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: releng/10.1/sys/kern/kern_thread.c 271372 2014-09-10 09:47:16Z kib $");
   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         EVENTHANDLER_INVOKE(thread_init, td);
  211         td->td_sched = (struct td_sched *)&td[1];
  212         umtx_thread_init(td);
  213         td->td_kstack = 0;
  214         return (0);
  215 }
  216 
  217 /*
  218  * Tear down type-stable parts of a thread (just before being discarded).
  219  */
  220 static void
  221 thread_fini(void *mem, int size)
  222 {
  223         struct thread *td;
  224 
  225         td = (struct thread *)mem;
  226         EVENTHANDLER_INVOKE(thread_fini, td);
  227         rlqentry_free(td->td_rlqe);
  228         turnstile_free(td->td_turnstile);
  229         sleepq_free(td->td_sleepqueue);
  230         umtx_thread_fini(td);
  231         seltdfini(td);
  232 }
  233 
  234 /*
  235  * For a newly created process,
  236  * link up all the structures and its initial threads etc.
  237  * called from:
  238  * {arch}/{arch}/machdep.c   ia64_init(), init386() etc.
  239  * proc_dtor() (should go away)
  240  * proc_init()
  241  */
  242 void
  243 proc_linkup0(struct proc *p, struct thread *td)
  244 {
  245         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
  246         proc_linkup(p, td);
  247 }
  248 
  249 void
  250 proc_linkup(struct proc *p, struct thread *td)
  251 {
  252 
  253         sigqueue_init(&p->p_sigqueue, p);
  254         p->p_ksi = ksiginfo_alloc(1);
  255         if (p->p_ksi != NULL) {
  256                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
  257                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
  258         }
  259         LIST_INIT(&p->p_mqnotifier);
  260         p->p_numthreads = 0;
  261         thread_link(td, p);
  262 }
  263 
  264 /*
  265  * Initialize global thread allocation resources.
  266  */
  267 void
  268 threadinit(void)
  269 {
  270 
  271         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
  272 
  273         /*
  274          * pid_max cannot be greater than PID_MAX.
  275          * leave one number for thread0.
  276          */
  277         tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
  278 
  279         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
  280             thread_ctor, thread_dtor, thread_init, thread_fini,
  281             16 - 1, 0);
  282         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
  283         rw_init(&tidhash_lock, "tidhash");
  284 }
  285 
  286 /*
  287  * Place an unused thread on the zombie list.
  288  * Use the slpq as that must be unused by now.
  289  */
  290 void
  291 thread_zombie(struct thread *td)
  292 {
  293         mtx_lock_spin(&zombie_lock);
  294         TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
  295         mtx_unlock_spin(&zombie_lock);
  296 }
  297 
  298 /*
  299  * Release a thread that has exited after cpu_throw().
  300  */
  301 void
  302 thread_stash(struct thread *td)
  303 {
  304         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
  305         thread_zombie(td);
  306 }
  307 
  308 /*
  309  * Reap zombie resources.
  310  */
  311 void
  312 thread_reap(void)
  313 {
  314         struct thread *td_first, *td_next;
  315 
  316         /*
  317          * Don't even bother to lock if none at this instant,
  318          * we really don't care about the next instant..
  319          */
  320         if (!TAILQ_EMPTY(&zombie_threads)) {
  321                 mtx_lock_spin(&zombie_lock);
  322                 td_first = TAILQ_FIRST(&zombie_threads);
  323                 if (td_first)
  324                         TAILQ_INIT(&zombie_threads);
  325                 mtx_unlock_spin(&zombie_lock);
  326                 while (td_first) {
  327                         td_next = TAILQ_NEXT(td_first, td_slpq);
  328                         if (td_first->td_ucred)
  329                                 crfree(td_first->td_ucred);
  330                         thread_free(td_first);
  331                         td_first = td_next;
  332                 }
  333         }
  334 }
  335 
  336 /*
  337  * Allocate a thread.
  338  */
  339 struct thread *
  340 thread_alloc(int pages)
  341 {
  342         struct thread *td;
  343 
  344         thread_reap(); /* check if any zombies to get */
  345 
  346         td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
  347         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
  348         if (!vm_thread_new(td, pages)) {
  349                 uma_zfree(thread_zone, td);
  350                 return (NULL);
  351         }
  352         cpu_thread_alloc(td);
  353         return (td);
  354 }
  355 
  356 int
  357 thread_alloc_stack(struct thread *td, int pages)
  358 {
  359 
  360         KASSERT(td->td_kstack == 0,
  361             ("thread_alloc_stack called on a thread with kstack"));
  362         if (!vm_thread_new(td, pages))
  363                 return (0);
  364         cpu_thread_alloc(td);
  365         return (1);
  366 }
  367 
  368 /*
  369  * Deallocate a thread.
  370  */
  371 void
  372 thread_free(struct thread *td)
  373 {
  374 
  375         lock_profile_thread_exit(td);
  376         if (td->td_cpuset)
  377                 cpuset_rel(td->td_cpuset);
  378         td->td_cpuset = NULL;
  379         cpu_thread_free(td);
  380         if (td->td_kstack != 0)
  381                 vm_thread_dispose(td);
  382         uma_zfree(thread_zone, td);
  383 }
  384 
  385 /*
  386  * Discard the current thread and exit from its context.
  387  * Always called with scheduler locked.
  388  *
  389  * Because we can't free a thread while we're operating under its context,
  390  * push the current thread into our CPU's deadthread holder. This means
  391  * we needn't worry about someone else grabbing our context before we
  392  * do a cpu_throw().
  393  */
  394 void
  395 thread_exit(void)
  396 {
  397         uint64_t runtime, new_switchtime;
  398         struct thread *td;
  399         struct thread *td2;
  400         struct proc *p;
  401         int wakeup_swapper;
  402 
  403         td = curthread;
  404         p = td->td_proc;
  405 
  406         PROC_SLOCK_ASSERT(p, MA_OWNED);
  407         mtx_assert(&Giant, MA_NOTOWNED);
  408 
  409         PROC_LOCK_ASSERT(p, MA_OWNED);
  410         KASSERT(p != NULL, ("thread exiting without a process"));
  411         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
  412             (long)p->p_pid, td->td_name);
  413         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
  414 
  415 #ifdef AUDIT
  416         AUDIT_SYSCALL_EXIT(0, td);
  417 #endif
  418         umtx_thread_exit(td);
  419         /*
  420          * drop FPU & debug register state storage, or any other
  421          * architecture specific resources that
  422          * would not be on a new untouched process.
  423          */
  424         cpu_thread_exit(td);    /* XXXSMP */
  425 
  426         /*
  427          * The last thread is left attached to the process
  428          * So that the whole bundle gets recycled. Skip
  429          * all this stuff if we never had threads.
  430          * EXIT clears all sign of other threads when
  431          * it goes to single threading, so the last thread always
  432          * takes the short path.
  433          */
  434         if (p->p_flag & P_HADTHREADS) {
  435                 if (p->p_numthreads > 1) {
  436                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
  437                         thread_unlink(td);
  438                         td2 = FIRST_THREAD_IN_PROC(p);
  439                         sched_exit_thread(td2, td);
  440 
  441                         /*
  442                          * The test below is NOT true if we are the
  443                          * sole exiting thread. P_STOPPED_SINGLE is unset
  444                          * in exit1() after it is the only survivor.
  445                          */
  446                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  447                                 if (p->p_numthreads == p->p_suspcount) {
  448                                         thread_lock(p->p_singlethread);
  449                                         wakeup_swapper = thread_unsuspend_one(
  450                                                 p->p_singlethread);
  451                                         thread_unlock(p->p_singlethread);
  452                                         if (wakeup_swapper)
  453                                                 kick_proc0();
  454                                 }
  455                         }
  456 
  457                         PCPU_SET(deadthread, td);
  458                 } else {
  459                         /*
  460                          * The last thread is exiting.. but not through exit()
  461                          */
  462                         panic ("thread_exit: Last thread exiting on its own");
  463                 }
  464         } 
  465 #ifdef  HWPMC_HOOKS
  466         /*
  467          * If this thread is part of a process that is being tracked by hwpmc(4),
  468          * inform the module of the thread's impending exit.
  469          */
  470         if (PMC_PROC_IS_USING_PMCS(td->td_proc))
  471                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
  472 #endif
  473         PROC_UNLOCK(p);
  474 
  475         /* Do the same timestamp bookkeeping that mi_switch() would do. */
  476         new_switchtime = cpu_ticks();
  477         runtime = new_switchtime - PCPU_GET(switchtime);
  478         td->td_runtime += runtime;
  479         td->td_incruntime += runtime;
  480         PCPU_SET(switchtime, new_switchtime);
  481         PCPU_SET(switchticks, ticks);
  482         PCPU_INC(cnt.v_swtch);
  483 
  484         /* Save our resource usage in our process. */
  485         td->td_ru.ru_nvcsw++;
  486         ruxagg(p, td);
  487         rucollect(&p->p_ru, &td->td_ru);
  488 
  489         thread_lock(td);
  490         PROC_SUNLOCK(p);
  491         td->td_state = TDS_INACTIVE;
  492 #ifdef WITNESS
  493         witness_thread_exit(td);
  494 #endif
  495         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
  496         sched_throw(td);
  497         panic("I'm a teapot!");
  498         /* NOTREACHED */
  499 }
  500 
  501 /*
  502  * Do any thread specific cleanups that may be needed in wait()
  503  * called with Giant, proc and schedlock not held.
  504  */
  505 void
  506 thread_wait(struct proc *p)
  507 {
  508         struct thread *td;
  509 
  510         mtx_assert(&Giant, MA_NOTOWNED);
  511         KASSERT(p->p_numthreads == 1, ("multiple threads in thread_wait()"));
  512         KASSERT(p->p_exitthreads == 0, ("p_exitthreads leaking"));
  513         td = FIRST_THREAD_IN_PROC(p);
  514         /* Lock the last thread so we spin until it exits cpu_throw(). */
  515         thread_lock(td);
  516         thread_unlock(td);
  517         lock_profile_thread_exit(td);
  518         cpuset_rel(td->td_cpuset);
  519         td->td_cpuset = NULL;
  520         cpu_thread_clean(td);
  521         crfree(td->td_ucred);
  522         thread_reap();  /* check for zombie threads etc. */
  523 }
  524 
  525 /*
  526  * Link a thread to a process.
  527  * set up anything that needs to be initialized for it to
  528  * be used by the process.
  529  */
  530 void
  531 thread_link(struct thread *td, struct proc *p)
  532 {
  533 
  534         /*
  535          * XXX This can't be enabled because it's called for proc0 before
  536          * its lock has been created.
  537          * PROC_LOCK_ASSERT(p, MA_OWNED);
  538          */
  539         td->td_state    = TDS_INACTIVE;
  540         td->td_proc     = p;
  541         td->td_flags    = TDF_INMEM;
  542 
  543         LIST_INIT(&td->td_contested);
  544         LIST_INIT(&td->td_lprof[0]);
  545         LIST_INIT(&td->td_lprof[1]);
  546         sigqueue_init(&td->td_sigqueue, p);
  547         callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
  548         TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
  549         p->p_numthreads++;
  550 }
  551 
  552 /*
  553  * Called from:
  554  *  thread_exit()
  555  */
  556 void
  557 thread_unlink(struct thread *td)
  558 {
  559         struct proc *p = td->td_proc;
  560 
  561         PROC_LOCK_ASSERT(p, MA_OWNED);
  562         TAILQ_REMOVE(&p->p_threads, td, td_plist);
  563         p->p_numthreads--;
  564         /* could clear a few other things here */
  565         /* Must  NOT clear links to proc! */
  566 }
  567 
  568 static int
  569 calc_remaining(struct proc *p, int mode)
  570 {
  571         int remaining;
  572 
  573         PROC_LOCK_ASSERT(p, MA_OWNED);
  574         PROC_SLOCK_ASSERT(p, MA_OWNED);
  575         if (mode == SINGLE_EXIT)
  576                 remaining = p->p_numthreads;
  577         else if (mode == SINGLE_BOUNDARY)
  578                 remaining = p->p_numthreads - p->p_boundary_count;
  579         else if (mode == SINGLE_NO_EXIT)
  580                 remaining = p->p_numthreads - p->p_suspcount;
  581         else
  582                 panic("calc_remaining: wrong mode %d", mode);
  583         return (remaining);
  584 }
  585 
  586 /*
  587  * Enforce single-threading.
  588  *
  589  * Returns 1 if the caller must abort (another thread is waiting to
  590  * exit the process or similar). Process is locked!
  591  * Returns 0 when you are successfully the only thread running.
  592  * A process has successfully single threaded in the suspend mode when
  593  * There are no threads in user mode. Threads in the kernel must be
  594  * allowed to continue until they get to the user boundary. They may even
  595  * copy out their return values and data before suspending. They may however be
  596  * accelerated in reaching the user boundary as we will wake up
  597  * any sleeping threads that are interruptable. (PCATCH).
  598  */
  599 int
  600 thread_single(int mode)
  601 {
  602         struct thread *td;
  603         struct thread *td2;
  604         struct proc *p;
  605         int remaining, wakeup_swapper;
  606 
  607         td = curthread;
  608         p = td->td_proc;
  609         mtx_assert(&Giant, MA_NOTOWNED);
  610         PROC_LOCK_ASSERT(p, MA_OWNED);
  611 
  612         if ((p->p_flag & P_HADTHREADS) == 0)
  613                 return (0);
  614 
  615         /* Is someone already single threading? */
  616         if (p->p_singlethread != NULL && p->p_singlethread != td)
  617                 return (1);
  618 
  619         if (mode == SINGLE_EXIT) {
  620                 p->p_flag |= P_SINGLE_EXIT;
  621                 p->p_flag &= ~P_SINGLE_BOUNDARY;
  622         } else {
  623                 p->p_flag &= ~P_SINGLE_EXIT;
  624                 if (mode == SINGLE_BOUNDARY)
  625                         p->p_flag |= P_SINGLE_BOUNDARY;
  626                 else
  627                         p->p_flag &= ~P_SINGLE_BOUNDARY;
  628         }
  629         p->p_flag |= P_STOPPED_SINGLE;
  630         PROC_SLOCK(p);
  631         p->p_singlethread = td;
  632         remaining = calc_remaining(p, mode);
  633         while (remaining != 1) {
  634                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
  635                         goto stopme;
  636                 wakeup_swapper = 0;
  637                 FOREACH_THREAD_IN_PROC(p, td2) {
  638                         if (td2 == td)
  639                                 continue;
  640                         thread_lock(td2);
  641                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
  642                         if (TD_IS_INHIBITED(td2)) {
  643                                 switch (mode) {
  644                                 case SINGLE_EXIT:
  645                                         if (TD_IS_SUSPENDED(td2))
  646                                                 wakeup_swapper |=
  647                                                     thread_unsuspend_one(td2);
  648                                         if (TD_ON_SLEEPQ(td2) &&
  649                                             (td2->td_flags & TDF_SINTR))
  650                                                 wakeup_swapper |=
  651                                                     sleepq_abort(td2, EINTR);
  652                                         break;
  653                                 case SINGLE_BOUNDARY:
  654                                         if (TD_IS_SUSPENDED(td2) &&
  655                                             !(td2->td_flags & TDF_BOUNDARY))
  656                                                 wakeup_swapper |=
  657                                                     thread_unsuspend_one(td2);
  658                                         if (TD_ON_SLEEPQ(td2) &&
  659                                             (td2->td_flags & TDF_SINTR))
  660                                                 wakeup_swapper |=
  661                                                     sleepq_abort(td2, ERESTART);
  662                                         break;
  663                                 case SINGLE_NO_EXIT:
  664                                         if (TD_IS_SUSPENDED(td2) &&
  665                                             !(td2->td_flags & TDF_BOUNDARY))
  666                                                 wakeup_swapper |=
  667                                                     thread_unsuspend_one(td2);
  668                                         if (TD_ON_SLEEPQ(td2) &&
  669                                             (td2->td_flags & TDF_SINTR))
  670                                                 wakeup_swapper |=
  671                                                     sleepq_abort(td2, ERESTART);
  672                                         break;
  673                                 default:
  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 (wakeup_swapper)
  685                         kick_proc0();
  686                 remaining = calc_remaining(p, mode);
  687 
  688                 /*
  689                  * Maybe we suspended some threads.. was it enough?
  690                  */
  691                 if (remaining == 1)
  692                         break;
  693 
  694 stopme:
  695                 /*
  696                  * Wake us up when everyone else has suspended.
  697                  * In the mean time we suspend as well.
  698                  */
  699                 thread_suspend_switch(td);
  700                 remaining = calc_remaining(p, mode);
  701         }
  702         if (mode == SINGLE_EXIT) {
  703                 /*
  704                  * Convert the process to an unthreaded process.  The
  705                  * SINGLE_EXIT is called by exit1() or execve(), in
  706                  * both cases other threads must be retired.
  707                  */
  708                 KASSERT(p->p_numthreads == 1, ("Unthreading with >1 threads"));
  709                 p->p_singlethread = NULL;
  710                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_HADTHREADS);
  711 
  712                 /*
  713                  * Wait for any remaining threads to exit cpu_throw().
  714                  */
  715                 while (p->p_exitthreads != 0) {
  716                         PROC_SUNLOCK(p);
  717                         PROC_UNLOCK(p);
  718                         sched_relinquish(td);
  719                         PROC_LOCK(p);
  720                         PROC_SLOCK(p);
  721                 }
  722         }
  723         PROC_SUNLOCK(p);
  724         return (0);
  725 }
  726 
  727 /*
  728  * Called in from locations that can safely check to see
  729  * whether we have to suspend or at least throttle for a
  730  * single-thread event (e.g. fork).
  731  *
  732  * Such locations include userret().
  733  * If the "return_instead" argument is non zero, the thread must be able to
  734  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
  735  *
  736  * The 'return_instead' argument tells the function if it may do a
  737  * thread_exit() or suspend, or whether the caller must abort and back
  738  * out instead.
  739  *
  740  * If the thread that set the single_threading request has set the
  741  * P_SINGLE_EXIT bit in the process flags then this call will never return
  742  * if 'return_instead' is false, but will exit.
  743  *
  744  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
  745  *---------------+--------------------+---------------------
  746  *       0       | returns 0          |   returns 0 or 1
  747  *               | when ST ends       |   immediately
  748  *---------------+--------------------+---------------------
  749  *       1       | thread exits       |   returns 1
  750  *               |                    |  immediately
  751  * 0 = thread_exit() or suspension ok,
  752  * other = return error instead of stopping the thread.
  753  *
  754  * While a full suspension is under effect, even a single threading
  755  * thread would be suspended if it made this call (but it shouldn't).
  756  * This call should only be made from places where
  757  * thread_exit() would be safe as that may be the outcome unless
  758  * return_instead is set.
  759  */
  760 int
  761 thread_suspend_check(int return_instead)
  762 {
  763         struct thread *td;
  764         struct proc *p;
  765         int wakeup_swapper;
  766 
  767         td = curthread;
  768         p = td->td_proc;
  769         mtx_assert(&Giant, MA_NOTOWNED);
  770         PROC_LOCK_ASSERT(p, MA_OWNED);
  771         while (P_SHOULDSTOP(p) ||
  772               ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
  773                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  774                         KASSERT(p->p_singlethread != NULL,
  775                             ("singlethread not set"));
  776                         /*
  777                          * The only suspension in action is a
  778                          * single-threading. Single threader need not stop.
  779                          * XXX Should be safe to access unlocked
  780                          * as it can only be set to be true by us.
  781                          */
  782                         if (p->p_singlethread == td)
  783                                 return (0);     /* Exempt from stopping. */
  784                 }
  785                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
  786                         return (EINTR);
  787 
  788                 /* Should we goto user boundary if we didn't come from there? */
  789                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
  790                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
  791                         return (ERESTART);
  792 
  793                 /*
  794                  * Ignore suspend requests for stop signals if they
  795                  * are deferred.
  796                  */
  797                 if (P_SHOULDSTOP(p) == P_STOPPED_SIG &&
  798                     td->td_flags & TDF_SBDRY) {
  799                         KASSERT(return_instead,
  800                             ("TDF_SBDRY set for unsafe thread_suspend_check"));
  801                         return (0);
  802                 }
  803 
  804                 /*
  805                  * If the process is waiting for us to exit,
  806                  * this thread should just suicide.
  807                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
  808                  */
  809                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
  810                         PROC_UNLOCK(p);
  811                         tidhash_remove(td);
  812                         PROC_LOCK(p);
  813                         tdsigcleanup(td);
  814                         PROC_SLOCK(p);
  815                         thread_stopped(p);
  816                         thread_exit();
  817                 }
  818 
  819                 PROC_SLOCK(p);
  820                 thread_stopped(p);
  821                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  822                         if (p->p_numthreads == p->p_suspcount + 1) {
  823                                 thread_lock(p->p_singlethread);
  824                                 wakeup_swapper =
  825                                     thread_unsuspend_one(p->p_singlethread);
  826                                 thread_unlock(p->p_singlethread);
  827                                 if (wakeup_swapper)
  828                                         kick_proc0();
  829                         }
  830                 }
  831                 PROC_UNLOCK(p);
  832                 thread_lock(td);
  833                 /*
  834                  * When a thread suspends, it just
  835                  * gets taken off all queues.
  836                  */
  837                 thread_suspend_one(td);
  838                 if (return_instead == 0) {
  839                         p->p_boundary_count++;
  840                         td->td_flags |= TDF_BOUNDARY;
  841                 }
  842                 PROC_SUNLOCK(p);
  843                 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
  844                 if (return_instead == 0)
  845                         td->td_flags &= ~TDF_BOUNDARY;
  846                 thread_unlock(td);
  847                 PROC_LOCK(p);
  848                 if (return_instead == 0) {
  849                         PROC_SLOCK(p);
  850                         p->p_boundary_count--;
  851                         PROC_SUNLOCK(p);
  852                 }
  853         }
  854         return (0);
  855 }
  856 
  857 void
  858 thread_suspend_switch(struct thread *td)
  859 {
  860         struct proc *p;
  861 
  862         p = td->td_proc;
  863         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
  864         PROC_LOCK_ASSERT(p, MA_OWNED);
  865         PROC_SLOCK_ASSERT(p, MA_OWNED);
  866         /*
  867          * We implement thread_suspend_one in stages here to avoid
  868          * dropping the proc lock while the thread lock is owned.
  869          */
  870         thread_stopped(p);
  871         p->p_suspcount++;
  872         PROC_UNLOCK(p);
  873         thread_lock(td);
  874         td->td_flags &= ~TDF_NEEDSUSPCHK;
  875         TD_SET_SUSPENDED(td);
  876         sched_sleep(td, 0);
  877         PROC_SUNLOCK(p);
  878         DROP_GIANT();
  879         mi_switch(SW_VOL | SWT_SUSPEND, NULL);
  880         thread_unlock(td);
  881         PICKUP_GIANT();
  882         PROC_LOCK(p);
  883         PROC_SLOCK(p);
  884 }
  885 
  886 void
  887 thread_suspend_one(struct thread *td)
  888 {
  889         struct proc *p = td->td_proc;
  890 
  891         PROC_SLOCK_ASSERT(p, MA_OWNED);
  892         THREAD_LOCK_ASSERT(td, MA_OWNED);
  893         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
  894         p->p_suspcount++;
  895         td->td_flags &= ~TDF_NEEDSUSPCHK;
  896         TD_SET_SUSPENDED(td);
  897         sched_sleep(td, 0);
  898 }
  899 
  900 int
  901 thread_unsuspend_one(struct thread *td)
  902 {
  903         struct proc *p = td->td_proc;
  904 
  905         PROC_SLOCK_ASSERT(p, MA_OWNED);
  906         THREAD_LOCK_ASSERT(td, MA_OWNED);
  907         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
  908         TD_CLR_SUSPENDED(td);
  909         p->p_suspcount--;
  910         return (setrunnable(td));
  911 }
  912 
  913 /*
  914  * Allow all threads blocked by single threading to continue running.
  915  */
  916 void
  917 thread_unsuspend(struct proc *p)
  918 {
  919         struct thread *td;
  920         int wakeup_swapper;
  921 
  922         PROC_LOCK_ASSERT(p, MA_OWNED);
  923         PROC_SLOCK_ASSERT(p, MA_OWNED);
  924         wakeup_swapper = 0;
  925         if (!P_SHOULDSTOP(p)) {
  926                 FOREACH_THREAD_IN_PROC(p, td) {
  927                         thread_lock(td);
  928                         if (TD_IS_SUSPENDED(td)) {
  929                                 wakeup_swapper |= thread_unsuspend_one(td);
  930                         }
  931                         thread_unlock(td);
  932                 }
  933         } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
  934             (p->p_numthreads == p->p_suspcount)) {
  935                 /*
  936                  * Stopping everything also did the job for the single
  937                  * threading request. Now we've downgraded to single-threaded,
  938                  * let it continue.
  939                  */
  940                 thread_lock(p->p_singlethread);
  941                 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
  942                 thread_unlock(p->p_singlethread);
  943         }
  944         if (wakeup_swapper)
  945                 kick_proc0();
  946 }
  947 
  948 /*
  949  * End the single threading mode..
  950  */
  951 void
  952 thread_single_end(void)
  953 {
  954         struct thread *td;
  955         struct proc *p;
  956         int wakeup_swapper;
  957 
  958         td = curthread;
  959         p = td->td_proc;
  960         PROC_LOCK_ASSERT(p, MA_OWNED);
  961         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
  962         PROC_SLOCK(p);
  963         p->p_singlethread = NULL;
  964         wakeup_swapper = 0;
  965         /*
  966          * If there are other threads they may now run,
  967          * unless of course there is a blanket 'stop order'
  968          * on the process. The single threader must be allowed
  969          * to continue however as this is a bad place to stop.
  970          */
  971         if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
  972                 FOREACH_THREAD_IN_PROC(p, td) {
  973                         thread_lock(td);
  974                         if (TD_IS_SUSPENDED(td)) {
  975                                 wakeup_swapper |= thread_unsuspend_one(td);
  976                         }
  977                         thread_unlock(td);
  978                 }
  979         }
  980         PROC_SUNLOCK(p);
  981         if (wakeup_swapper)
  982                 kick_proc0();
  983 }
  984 
  985 struct thread *
  986 thread_find(struct proc *p, lwpid_t tid)
  987 {
  988         struct thread *td;
  989 
  990         PROC_LOCK_ASSERT(p, MA_OWNED);
  991         FOREACH_THREAD_IN_PROC(p, td) {
  992                 if (td->td_tid == tid)
  993                         break;
  994         }
  995         return (td);
  996 }
  997 
  998 /* Locate a thread by number; return with proc lock held. */
  999 struct thread *
 1000 tdfind(lwpid_t tid, pid_t pid)
 1001 {
 1002 #define RUN_THRESH      16
 1003         struct thread *td;
 1004         int run = 0;
 1005 
 1006         rw_rlock(&tidhash_lock);
 1007         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
 1008                 if (td->td_tid == tid) {
 1009                         if (pid != -1 && td->td_proc->p_pid != pid) {
 1010                                 td = NULL;
 1011                                 break;
 1012                         }
 1013                         PROC_LOCK(td->td_proc);
 1014                         if (td->td_proc->p_state == PRS_NEW) {
 1015                                 PROC_UNLOCK(td->td_proc);
 1016                                 td = NULL;
 1017                                 break;
 1018                         }
 1019                         if (run > RUN_THRESH) {
 1020                                 if (rw_try_upgrade(&tidhash_lock)) {
 1021                                         LIST_REMOVE(td, td_hash);
 1022                                         LIST_INSERT_HEAD(TIDHASH(td->td_tid),
 1023                                                 td, td_hash);
 1024                                         rw_wunlock(&tidhash_lock);
 1025                                         return (td);
 1026                                 }
 1027                         }
 1028                         break;
 1029                 }
 1030                 run++;
 1031         }
 1032         rw_runlock(&tidhash_lock);
 1033         return (td);
 1034 }
 1035 
 1036 void
 1037 tidhash_add(struct thread *td)
 1038 {
 1039         rw_wlock(&tidhash_lock);
 1040         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
 1041         rw_wunlock(&tidhash_lock);
 1042 }
 1043 
 1044 void
 1045 tidhash_remove(struct thread *td)
 1046 {
 1047         rw_wlock(&tidhash_lock);
 1048         LIST_REMOVE(td, td_hash);
 1049         rw_wunlock(&tidhash_lock);
 1050 }
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_thread.c

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