The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/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/9.1/sys/kern/kern_thread.c 236344 2012-05-30 23:22:52Z rstone $");
   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/resourcevar.h>
   43 #include <sys/sdt.h>
   44 #include <sys/smp.h>
   45 #include <sys/sched.h>
   46 #include <sys/sleepqueue.h>
   47 #include <sys/selinfo.h>
   48 #include <sys/turnstile.h>
   49 #include <sys/ktr.h>
   50 #include <sys/rwlock.h>
   51 #include <sys/umtx.h>
   52 #include <sys/cpuset.h>
   53 #ifdef  HWPMC_HOOKS
   54 #include <sys/pmckern.h>
   55 #endif
   56 
   57 #include <security/audit/audit.h>
   58 
   59 #include <vm/vm.h>
   60 #include <vm/vm_extern.h>
   61 #include <vm/uma.h>
   62 #include <sys/eventhandler.h>
   63 
   64 SDT_PROVIDER_DECLARE(proc);
   65 SDT_PROBE_DEFINE(proc, , , lwp_exit, lwp-exit);
   66 
   67 
   68 /*
   69  * thread related storage.
   70  */
   71 static uma_zone_t thread_zone;
   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 #define TID_BUFFER_SIZE 1024
   80 
   81 struct mtx tid_lock;
   82 static struct unrhdr *tid_unrhdr;
   83 static lwpid_t tid_buffer[TID_BUFFER_SIZE];
   84 static int tid_head, tid_tail;
   85 static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
   86 
   87 struct  tidhashhead *tidhashtbl;
   88 u_long  tidhash;
   89 struct  rwlock tidhash_lock;
   90 
   91 static lwpid_t
   92 tid_alloc(void)
   93 {
   94         lwpid_t tid;
   95 
   96         tid = alloc_unr(tid_unrhdr);
   97         if (tid != -1)
   98                 return (tid);
   99         mtx_lock(&tid_lock);
  100         if (tid_head == tid_tail) {
  101                 mtx_unlock(&tid_lock);
  102                 return (-1);
  103         }
  104         tid = tid_buffer[tid_head++];
  105         tid_head %= TID_BUFFER_SIZE;
  106         mtx_unlock(&tid_lock);
  107         return (tid);
  108 }
  109 
  110 static void
  111 tid_free(lwpid_t tid)
  112 {
  113         lwpid_t tmp_tid = -1;
  114 
  115         mtx_lock(&tid_lock);
  116         if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
  117                 tmp_tid = tid_buffer[tid_head++];
  118                 tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
  119         }
  120         tid_buffer[tid_tail++] = tid;
  121         tid_tail %= TID_BUFFER_SIZE;
  122         mtx_unlock(&tid_lock);
  123         if (tmp_tid != -1)
  124                 free_unr(tid_unrhdr, tmp_tid);
  125 }
  126 
  127 /*
  128  * Prepare a thread for use.
  129  */
  130 static int
  131 thread_ctor(void *mem, int size, void *arg, int flags)
  132 {
  133         struct thread   *td;
  134 
  135         td = (struct thread *)mem;
  136         td->td_state = TDS_INACTIVE;
  137         td->td_oncpu = NOCPU;
  138 
  139         td->td_tid = tid_alloc();
  140 
  141         /*
  142          * Note that td_critnest begins life as 1 because the thread is not
  143          * running and is thereby implicitly waiting to be on the receiving
  144          * end of a context switch.
  145          */
  146         td->td_critnest = 1;
  147         td->td_lend_user_pri = PRI_MAX;
  148         EVENTHANDLER_INVOKE(thread_ctor, td);
  149 #ifdef AUDIT
  150         audit_thread_alloc(td);
  151 #endif
  152         umtx_thread_alloc(td);
  153         return (0);
  154 }
  155 
  156 /*
  157  * Reclaim a thread after use.
  158  */
  159 static void
  160 thread_dtor(void *mem, int size, void *arg)
  161 {
  162         struct thread *td;
  163 
  164         td = (struct thread *)mem;
  165 
  166 #ifdef INVARIANTS
  167         /* Verify that this thread is in a safe state to free. */
  168         switch (td->td_state) {
  169         case TDS_INHIBITED:
  170         case TDS_RUNNING:
  171         case TDS_CAN_RUN:
  172         case TDS_RUNQ:
  173                 /*
  174                  * We must never unlink a thread that is in one of
  175                  * these states, because it is currently active.
  176                  */
  177                 panic("bad state for thread unlinking");
  178                 /* NOTREACHED */
  179         case TDS_INACTIVE:
  180                 break;
  181         default:
  182                 panic("bad thread state");
  183                 /* NOTREACHED */
  184         }
  185 #endif
  186 #ifdef AUDIT
  187         audit_thread_free(td);
  188 #endif
  189         /* Free all OSD associated to this thread. */
  190         osd_thread_exit(td);
  191 
  192         EVENTHANDLER_INVOKE(thread_dtor, td);
  193         tid_free(td->td_tid);
  194 }
  195 
  196 /*
  197  * Initialize type-stable parts of a thread (when newly created).
  198  */
  199 static int
  200 thread_init(void *mem, int size, int flags)
  201 {
  202         struct thread *td;
  203 
  204         td = (struct thread *)mem;
  205 
  206         td->td_sleepqueue = sleepq_alloc();
  207         td->td_turnstile = turnstile_alloc();
  208         EVENTHANDLER_INVOKE(thread_init, td);
  209         td->td_sched = (struct td_sched *)&td[1];
  210         umtx_thread_init(td);
  211         td->td_kstack = 0;
  212         return (0);
  213 }
  214 
  215 /*
  216  * Tear down type-stable parts of a thread (just before being discarded).
  217  */
  218 static void
  219 thread_fini(void *mem, int size)
  220 {
  221         struct thread *td;
  222 
  223         td = (struct thread *)mem;
  224         EVENTHANDLER_INVOKE(thread_fini, td);
  225         turnstile_free(td->td_turnstile);
  226         sleepq_free(td->td_sleepqueue);
  227         umtx_thread_fini(td);
  228         seltdfini(td);
  229 }
  230 
  231 /*
  232  * For a newly created process,
  233  * link up all the structures and its initial threads etc.
  234  * called from:
  235  * {arch}/{arch}/machdep.c   ia64_init(), init386() etc.
  236  * proc_dtor() (should go away)
  237  * proc_init()
  238  */
  239 void
  240 proc_linkup0(struct proc *p, struct thread *td)
  241 {
  242         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
  243         proc_linkup(p, td);
  244 }
  245 
  246 void
  247 proc_linkup(struct proc *p, struct thread *td)
  248 {
  249 
  250         sigqueue_init(&p->p_sigqueue, p);
  251         p->p_ksi = ksiginfo_alloc(1);
  252         if (p->p_ksi != NULL) {
  253                 /* XXX p_ksi may be null if ksiginfo zone is not ready */
  254                 p->p_ksi->ksi_flags = KSI_EXT | KSI_INS;
  255         }
  256         LIST_INIT(&p->p_mqnotifier);
  257         p->p_numthreads = 0;
  258         thread_link(td, p);
  259 }
  260 
  261 /*
  262  * Initialize global thread allocation resources.
  263  */
  264 void
  265 threadinit(void)
  266 {
  267 
  268         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
  269         /* leave one number for thread0 */
  270         tid_unrhdr = new_unrhdr(PID_MAX + 2, INT_MAX, &tid_lock);
  271 
  272         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
  273             thread_ctor, thread_dtor, thread_init, thread_fini,
  274             16 - 1, 0);
  275         tidhashtbl = hashinit(maxproc / 2, M_TIDHASH, &tidhash);
  276         rw_init(&tidhash_lock, "tidhash");
  277 }
  278 
  279 /*
  280  * Place an unused thread on the zombie list.
  281  * Use the slpq as that must be unused by now.
  282  */
  283 void
  284 thread_zombie(struct thread *td)
  285 {
  286         mtx_lock_spin(&zombie_lock);
  287         TAILQ_INSERT_HEAD(&zombie_threads, td, td_slpq);
  288         mtx_unlock_spin(&zombie_lock);
  289 }
  290 
  291 /*
  292  * Release a thread that has exited after cpu_throw().
  293  */
  294 void
  295 thread_stash(struct thread *td)
  296 {
  297         atomic_subtract_rel_int(&td->td_proc->p_exitthreads, 1);
  298         thread_zombie(td);
  299 }
  300 
  301 /*
  302  * Reap zombie resources.
  303  */
  304 void
  305 thread_reap(void)
  306 {
  307         struct thread *td_first, *td_next;
  308 
  309         /*
  310          * Don't even bother to lock if none at this instant,
  311          * we really don't care about the next instant..
  312          */
  313         if (!TAILQ_EMPTY(&zombie_threads)) {
  314                 mtx_lock_spin(&zombie_lock);
  315                 td_first = TAILQ_FIRST(&zombie_threads);
  316                 if (td_first)
  317                         TAILQ_INIT(&zombie_threads);
  318                 mtx_unlock_spin(&zombie_lock);
  319                 while (td_first) {
  320                         td_next = TAILQ_NEXT(td_first, td_slpq);
  321                         if (td_first->td_ucred)
  322                                 crfree(td_first->td_ucred);
  323                         thread_free(td_first);
  324                         td_first = td_next;
  325                 }
  326         }
  327 }
  328 
  329 /*
  330  * Allocate a thread.
  331  */
  332 struct thread *
  333 thread_alloc(int pages)
  334 {
  335         struct thread *td;
  336 
  337         thread_reap(); /* check if any zombies to get */
  338 
  339         td = (struct thread *)uma_zalloc(thread_zone, M_WAITOK);
  340         KASSERT(td->td_kstack == 0, ("thread_alloc got thread with kstack"));
  341         if (!vm_thread_new(td, pages)) {
  342                 uma_zfree(thread_zone, td);
  343                 return (NULL);
  344         }
  345         cpu_thread_alloc(td);
  346         return (td);
  347 }
  348 
  349 int
  350 thread_alloc_stack(struct thread *td, int pages)
  351 {
  352 
  353         KASSERT(td->td_kstack == 0,
  354             ("thread_alloc_stack called on a thread with kstack"));
  355         if (!vm_thread_new(td, pages))
  356                 return (0);
  357         cpu_thread_alloc(td);
  358         return (1);
  359 }
  360 
  361 /*
  362  * Deallocate a thread.
  363  */
  364 void
  365 thread_free(struct thread *td)
  366 {
  367 
  368         lock_profile_thread_exit(td);
  369         if (td->td_cpuset)
  370                 cpuset_rel(td->td_cpuset);
  371         td->td_cpuset = NULL;
  372         cpu_thread_free(td);
  373         if (td->td_kstack != 0)
  374                 vm_thread_dispose(td);
  375         uma_zfree(thread_zone, td);
  376 }
  377 
  378 /*
  379  * Discard the current thread and exit from its context.
  380  * Always called with scheduler locked.
  381  *
  382  * Because we can't free a thread while we're operating under its context,
  383  * push the current thread into our CPU's deadthread holder. This means
  384  * we needn't worry about someone else grabbing our context before we
  385  * do a cpu_throw().
  386  */
  387 void
  388 thread_exit(void)
  389 {
  390         uint64_t runtime, new_switchtime;
  391         struct thread *td;
  392         struct thread *td2;
  393         struct proc *p;
  394         int wakeup_swapper;
  395 
  396         td = curthread;
  397         p = td->td_proc;
  398 
  399         PROC_SLOCK_ASSERT(p, MA_OWNED);
  400         mtx_assert(&Giant, MA_NOTOWNED);
  401 
  402         PROC_LOCK_ASSERT(p, MA_OWNED);
  403         KASSERT(p != NULL, ("thread exiting without a process"));
  404         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
  405             (long)p->p_pid, td->td_name);
  406         KASSERT(TAILQ_EMPTY(&td->td_sigqueue.sq_list), ("signal pending"));
  407 
  408 #ifdef AUDIT
  409         AUDIT_SYSCALL_EXIT(0, td);
  410 #endif
  411         umtx_thread_exit(td);
  412         /*
  413          * drop FPU & debug register state storage, or any other
  414          * architecture specific resources that
  415          * would not be on a new untouched process.
  416          */
  417         cpu_thread_exit(td);    /* XXXSMP */
  418 
  419         /*
  420          * The last thread is left attached to the process
  421          * So that the whole bundle gets recycled. Skip
  422          * all this stuff if we never had threads.
  423          * EXIT clears all sign of other threads when
  424          * it goes to single threading, so the last thread always
  425          * takes the short path.
  426          */
  427         if (p->p_flag & P_HADTHREADS) {
  428                 if (p->p_numthreads > 1) {
  429                         thread_unlink(td);
  430                         td2 = FIRST_THREAD_IN_PROC(p);
  431                         sched_exit_thread(td2, td);
  432 
  433                         /*
  434                          * The test below is NOT true if we are the
  435                          * sole exiting thread. P_STOPPED_SINGLE is unset
  436                          * in exit1() after it is the only survivor.
  437                          */
  438                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  439                                 if (p->p_numthreads == p->p_suspcount) {
  440                                         thread_lock(p->p_singlethread);
  441                                         wakeup_swapper = thread_unsuspend_one(
  442                                                 p->p_singlethread);
  443                                         thread_unlock(p->p_singlethread);
  444                                         if (wakeup_swapper)
  445                                                 kick_proc0();
  446                                 }
  447                         }
  448 
  449                         atomic_add_int(&td->td_proc->p_exitthreads, 1);
  450                         PCPU_SET(deadthread, td);
  451                 } else {
  452                         /*
  453                          * The last thread is exiting.. but not through exit()
  454                          */
  455                         panic ("thread_exit: Last thread exiting on its own");
  456                 }
  457         } 
  458 #ifdef  HWPMC_HOOKS
  459         /*
  460          * If this thread is part of a process that is being tracked by hwpmc(4),
  461          * inform the module of the thread's impending exit.
  462          */
  463         if (PMC_PROC_IS_USING_PMCS(td->td_proc))
  464                 PMC_SWITCH_CONTEXT(td, PMC_FN_CSW_OUT);
  465 #endif
  466         PROC_UNLOCK(p);
  467 
  468         /* Do the same timestamp bookkeeping that mi_switch() would do. */
  469         new_switchtime = cpu_ticks();
  470         runtime = new_switchtime - PCPU_GET(switchtime);
  471         td->td_runtime += runtime;
  472         td->td_incruntime += runtime;
  473         PCPU_SET(switchtime, new_switchtime);
  474         PCPU_SET(switchticks, ticks);
  475         PCPU_INC(cnt.v_swtch);
  476 
  477         /* Save our resource usage in our process. */
  478         td->td_ru.ru_nvcsw++;
  479         ruxagg(p, td);
  480         rucollect(&p->p_ru, &td->td_ru);
  481 
  482         thread_lock(td);
  483         PROC_SUNLOCK(p);
  484         td->td_state = TDS_INACTIVE;
  485 #ifdef WITNESS
  486         witness_thread_exit(td);
  487 #endif
  488         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
  489         sched_throw(td);
  490         panic("I'm a teapot!");
  491         /* NOTREACHED */
  492 }
  493 
  494 /*
  495  * Do any thread specific cleanups that may be needed in wait()
  496  * called with Giant, proc and schedlock not held.
  497  */
  498 void
  499 thread_wait(struct proc *p)
  500 {
  501         struct thread *td;
  502 
  503         mtx_assert(&Giant, MA_NOTOWNED);
  504         KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
  505         td = FIRST_THREAD_IN_PROC(p);
  506         /* Lock the last thread so we spin until it exits cpu_throw(). */
  507         thread_lock(td);
  508         thread_unlock(td);
  509         /* Wait for any remaining threads to exit cpu_throw(). */
  510         while (p->p_exitthreads)
  511                 sched_relinquish(curthread);
  512         lock_profile_thread_exit(td);
  513         cpuset_rel(td->td_cpuset);
  514         td->td_cpuset = NULL;
  515         cpu_thread_clean(td);
  516         crfree(td->td_ucred);
  517         thread_reap();  /* check for zombie threads etc. */
  518 }
  519 
  520 /*
  521  * Link a thread to a process.
  522  * set up anything that needs to be initialized for it to
  523  * be used by the process.
  524  */
  525 void
  526 thread_link(struct thread *td, struct proc *p)
  527 {
  528 
  529         /*
  530          * XXX This can't be enabled because it's called for proc0 before
  531          * its lock has been created.
  532          * PROC_LOCK_ASSERT(p, MA_OWNED);
  533          */
  534         td->td_state    = TDS_INACTIVE;
  535         td->td_proc     = p;
  536         td->td_flags    = TDF_INMEM;
  537 
  538         LIST_INIT(&td->td_contested);
  539         LIST_INIT(&td->td_lprof[0]);
  540         LIST_INIT(&td->td_lprof[1]);
  541         sigqueue_init(&td->td_sigqueue, p);
  542         callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
  543         TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
  544         p->p_numthreads++;
  545 }
  546 
  547 /*
  548  * Convert a process with one thread to an unthreaded process.
  549  */
  550 void
  551 thread_unthread(struct thread *td)
  552 {
  553         struct proc *p = td->td_proc;
  554 
  555         KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
  556         p->p_flag &= ~P_HADTHREADS;
  557 }
  558 
  559 /*
  560  * Called from:
  561  *  thread_exit()
  562  */
  563 void
  564 thread_unlink(struct thread *td)
  565 {
  566         struct proc *p = td->td_proc;
  567 
  568         PROC_LOCK_ASSERT(p, MA_OWNED);
  569         TAILQ_REMOVE(&p->p_threads, td, td_plist);
  570         p->p_numthreads--;
  571         /* could clear a few other things here */
  572         /* Must  NOT clear links to proc! */
  573 }
  574 
  575 static int
  576 calc_remaining(struct proc *p, int mode)
  577 {
  578         int remaining;
  579 
  580         PROC_LOCK_ASSERT(p, MA_OWNED);
  581         PROC_SLOCK_ASSERT(p, MA_OWNED);
  582         if (mode == SINGLE_EXIT)
  583                 remaining = p->p_numthreads;
  584         else if (mode == SINGLE_BOUNDARY)
  585                 remaining = p->p_numthreads - p->p_boundary_count;
  586         else if (mode == SINGLE_NO_EXIT)
  587                 remaining = p->p_numthreads - p->p_suspcount;
  588         else
  589                 panic("calc_remaining: wrong mode %d", mode);
  590         return (remaining);
  591 }
  592 
  593 /*
  594  * Enforce single-threading.
  595  *
  596  * Returns 1 if the caller must abort (another thread is waiting to
  597  * exit the process or similar). Process is locked!
  598  * Returns 0 when you are successfully the only thread running.
  599  * A process has successfully single threaded in the suspend mode when
  600  * There are no threads in user mode. Threads in the kernel must be
  601  * allowed to continue until they get to the user boundary. They may even
  602  * copy out their return values and data before suspending. They may however be
  603  * accelerated in reaching the user boundary as we will wake up
  604  * any sleeping threads that are interruptable. (PCATCH).
  605  */
  606 int
  607 thread_single(int mode)
  608 {
  609         struct thread *td;
  610         struct thread *td2;
  611         struct proc *p;
  612         int remaining, wakeup_swapper;
  613 
  614         td = curthread;
  615         p = td->td_proc;
  616         mtx_assert(&Giant, MA_NOTOWNED);
  617         PROC_LOCK_ASSERT(p, MA_OWNED);
  618         KASSERT((td != NULL), ("curthread is NULL"));
  619 
  620         if ((p->p_flag & P_HADTHREADS) == 0)
  621                 return (0);
  622 
  623         /* Is someone already single threading? */
  624         if (p->p_singlethread != NULL && p->p_singlethread != td)
  625                 return (1);
  626 
  627         if (mode == SINGLE_EXIT) {
  628                 p->p_flag |= P_SINGLE_EXIT;
  629                 p->p_flag &= ~P_SINGLE_BOUNDARY;
  630         } else {
  631                 p->p_flag &= ~P_SINGLE_EXIT;
  632                 if (mode == SINGLE_BOUNDARY)
  633                         p->p_flag |= P_SINGLE_BOUNDARY;
  634                 else
  635                         p->p_flag &= ~P_SINGLE_BOUNDARY;
  636         }
  637         p->p_flag |= P_STOPPED_SINGLE;
  638         PROC_SLOCK(p);
  639         p->p_singlethread = td;
  640         remaining = calc_remaining(p, mode);
  641         while (remaining != 1) {
  642                 if (P_SHOULDSTOP(p) != P_STOPPED_SINGLE)
  643                         goto stopme;
  644                 wakeup_swapper = 0;
  645                 FOREACH_THREAD_IN_PROC(p, td2) {
  646                         if (td2 == td)
  647                                 continue;
  648                         thread_lock(td2);
  649                         td2->td_flags |= TDF_ASTPENDING | TDF_NEEDSUSPCHK;
  650                         if (TD_IS_INHIBITED(td2)) {
  651                                 switch (mode) {
  652                                 case SINGLE_EXIT:
  653                                         if (TD_IS_SUSPENDED(td2))
  654                                                 wakeup_swapper |=
  655                                                     thread_unsuspend_one(td2);
  656                                         if (TD_ON_SLEEPQ(td2) &&
  657                                             (td2->td_flags & TDF_SINTR))
  658                                                 wakeup_swapper |=
  659                                                     sleepq_abort(td2, EINTR);
  660                                         break;
  661                                 case SINGLE_BOUNDARY:
  662                                         if (TD_IS_SUSPENDED(td2) &&
  663                                             !(td2->td_flags & TDF_BOUNDARY))
  664                                                 wakeup_swapper |=
  665                                                     thread_unsuspend_one(td2);
  666                                         if (TD_ON_SLEEPQ(td2) &&
  667                                             (td2->td_flags & TDF_SINTR))
  668                                                 wakeup_swapper |=
  669                                                     sleepq_abort(td2, ERESTART);
  670                                         break;
  671                                 case SINGLE_NO_EXIT:
  672                                         if (TD_IS_SUSPENDED(td2) &&
  673                                             !(td2->td_flags & TDF_BOUNDARY))
  674                                                 wakeup_swapper |=
  675                                                     thread_unsuspend_one(td2);
  676                                         if (TD_ON_SLEEPQ(td2) &&
  677                                             (td2->td_flags & TDF_SINTR))
  678                                                 wakeup_swapper |=
  679                                                     sleepq_abort(td2, ERESTART);
  680                                         break;
  681                                 default:
  682                                         break;
  683                                 }
  684                         }
  685 #ifdef SMP
  686                         else if (TD_IS_RUNNING(td2) && td != td2) {
  687                                 forward_signal(td2);
  688                         }
  689 #endif
  690                         thread_unlock(td2);
  691                 }
  692                 if (wakeup_swapper)
  693                         kick_proc0();
  694                 remaining = calc_remaining(p, mode);
  695 
  696                 /*
  697                  * Maybe we suspended some threads.. was it enough?
  698                  */
  699                 if (remaining == 1)
  700                         break;
  701 
  702 stopme:
  703                 /*
  704                  * Wake us up when everyone else has suspended.
  705                  * In the mean time we suspend as well.
  706                  */
  707                 thread_suspend_switch(td);
  708                 remaining = calc_remaining(p, mode);
  709         }
  710         if (mode == SINGLE_EXIT) {
  711                 /*
  712                  * We have gotten rid of all the other threads and we
  713                  * are about to either exit or exec. In either case,
  714                  * we try our utmost  to revert to being a non-threaded
  715                  * process.
  716                  */
  717                 p->p_singlethread = NULL;
  718                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
  719                 thread_unthread(td);
  720         }
  721         PROC_SUNLOCK(p);
  722         return (0);
  723 }
  724 
  725 /*
  726  * Called in from locations that can safely check to see
  727  * whether we have to suspend or at least throttle for a
  728  * single-thread event (e.g. fork).
  729  *
  730  * Such locations include userret().
  731  * If the "return_instead" argument is non zero, the thread must be able to
  732  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
  733  *
  734  * The 'return_instead' argument tells the function if it may do a
  735  * thread_exit() or suspend, or whether the caller must abort and back
  736  * out instead.
  737  *
  738  * If the thread that set the single_threading request has set the
  739  * P_SINGLE_EXIT bit in the process flags then this call will never return
  740  * if 'return_instead' is false, but will exit.
  741  *
  742  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
  743  *---------------+--------------------+---------------------
  744  *       0       | returns 0          |   returns 0 or 1
  745  *               | when ST ends       |   immediatly
  746  *---------------+--------------------+---------------------
  747  *       1       | thread exits       |   returns 1
  748  *               |                    |  immediatly
  749  * 0 = thread_exit() or suspension ok,
  750  * other = return error instead of stopping the thread.
  751  *
  752  * While a full suspension is under effect, even a single threading
  753  * thread would be suspended if it made this call (but it shouldn't).
  754  * This call should only be made from places where
  755  * thread_exit() would be safe as that may be the outcome unless
  756  * return_instead is set.
  757  */
  758 int
  759 thread_suspend_check(int return_instead)
  760 {
  761         struct thread *td;
  762         struct proc *p;
  763         int wakeup_swapper;
  764 
  765         td = curthread;
  766         p = td->td_proc;
  767         mtx_assert(&Giant, MA_NOTOWNED);
  768         PROC_LOCK_ASSERT(p, MA_OWNED);
  769         while (P_SHOULDSTOP(p) ||
  770               ((p->p_flag & P_TRACED) && (td->td_dbgflags & TDB_SUSPEND))) {
  771                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  772                         KASSERT(p->p_singlethread != NULL,
  773                             ("singlethread not set"));
  774                         /*
  775                          * The only suspension in action is a
  776                          * single-threading. Single threader need not stop.
  777                          * XXX Should be safe to access unlocked
  778                          * as it can only be set to be true by us.
  779                          */
  780                         if (p->p_singlethread == td)
  781                                 return (0);     /* Exempt from stopping. */
  782                 }
  783                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
  784                         return (EINTR);
  785 
  786                 /* Should we goto user boundary if we didn't come from there? */
  787                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
  788                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
  789                         return (ERESTART);
  790 
  791                 /*
  792                  * If the process is waiting for us to exit,
  793                  * this thread should just suicide.
  794                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
  795                  */
  796                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td)) {
  797                         PROC_UNLOCK(p);
  798                         tidhash_remove(td);
  799                         PROC_LOCK(p);
  800                         tdsigcleanup(td);
  801                         PROC_SLOCK(p);
  802                         thread_stopped(p);
  803                         thread_exit();
  804                 }
  805 
  806                 PROC_SLOCK(p);
  807                 thread_stopped(p);
  808                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  809                         if (p->p_numthreads == p->p_suspcount + 1) {
  810                                 thread_lock(p->p_singlethread);
  811                                 wakeup_swapper =
  812                                     thread_unsuspend_one(p->p_singlethread);
  813                                 thread_unlock(p->p_singlethread);
  814                                 if (wakeup_swapper)
  815                                         kick_proc0();
  816                         }
  817                 }
  818                 PROC_UNLOCK(p);
  819                 thread_lock(td);
  820                 /*
  821                  * When a thread suspends, it just
  822                  * gets taken off all queues.
  823                  */
  824                 thread_suspend_one(td);
  825                 if (return_instead == 0) {
  826                         p->p_boundary_count++;
  827                         td->td_flags |= TDF_BOUNDARY;
  828                 }
  829                 PROC_SUNLOCK(p);
  830                 mi_switch(SW_INVOL | SWT_SUSPEND, NULL);
  831                 if (return_instead == 0)
  832                         td->td_flags &= ~TDF_BOUNDARY;
  833                 thread_unlock(td);
  834                 PROC_LOCK(p);
  835                 if (return_instead == 0) {
  836                         PROC_SLOCK(p);
  837                         p->p_boundary_count--;
  838                         PROC_SUNLOCK(p);
  839                 }
  840         }
  841         return (0);
  842 }
  843 
  844 void
  845 thread_suspend_switch(struct thread *td)
  846 {
  847         struct proc *p;
  848 
  849         p = td->td_proc;
  850         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
  851         PROC_LOCK_ASSERT(p, MA_OWNED);
  852         PROC_SLOCK_ASSERT(p, MA_OWNED);
  853         /*
  854          * We implement thread_suspend_one in stages here to avoid
  855          * dropping the proc lock while the thread lock is owned.
  856          */
  857         thread_stopped(p);
  858         p->p_suspcount++;
  859         PROC_UNLOCK(p);
  860         thread_lock(td);
  861         td->td_flags &= ~TDF_NEEDSUSPCHK;
  862         TD_SET_SUSPENDED(td);
  863         sched_sleep(td, 0);
  864         PROC_SUNLOCK(p);
  865         DROP_GIANT();
  866         mi_switch(SW_VOL | SWT_SUSPEND, NULL);
  867         thread_unlock(td);
  868         PICKUP_GIANT();
  869         PROC_LOCK(p);
  870         PROC_SLOCK(p);
  871 }
  872 
  873 void
  874 thread_suspend_one(struct thread *td)
  875 {
  876         struct proc *p = td->td_proc;
  877 
  878         PROC_SLOCK_ASSERT(p, MA_OWNED);
  879         THREAD_LOCK_ASSERT(td, MA_OWNED);
  880         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
  881         p->p_suspcount++;
  882         td->td_flags &= ~TDF_NEEDSUSPCHK;
  883         TD_SET_SUSPENDED(td);
  884         sched_sleep(td, 0);
  885 }
  886 
  887 int
  888 thread_unsuspend_one(struct thread *td)
  889 {
  890         struct proc *p = td->td_proc;
  891 
  892         PROC_SLOCK_ASSERT(p, MA_OWNED);
  893         THREAD_LOCK_ASSERT(td, MA_OWNED);
  894         KASSERT(TD_IS_SUSPENDED(td), ("Thread not suspended"));
  895         TD_CLR_SUSPENDED(td);
  896         p->p_suspcount--;
  897         return (setrunnable(td));
  898 }
  899 
  900 /*
  901  * Allow all threads blocked by single threading to continue running.
  902  */
  903 void
  904 thread_unsuspend(struct proc *p)
  905 {
  906         struct thread *td;
  907         int wakeup_swapper;
  908 
  909         PROC_LOCK_ASSERT(p, MA_OWNED);
  910         PROC_SLOCK_ASSERT(p, MA_OWNED);
  911         wakeup_swapper = 0;
  912         if (!P_SHOULDSTOP(p)) {
  913                 FOREACH_THREAD_IN_PROC(p, td) {
  914                         thread_lock(td);
  915                         if (TD_IS_SUSPENDED(td)) {
  916                                 wakeup_swapper |= thread_unsuspend_one(td);
  917                         }
  918                         thread_unlock(td);
  919                 }
  920         } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
  921             (p->p_numthreads == p->p_suspcount)) {
  922                 /*
  923                  * Stopping everything also did the job for the single
  924                  * threading request. Now we've downgraded to single-threaded,
  925                  * let it continue.
  926                  */
  927                 thread_lock(p->p_singlethread);
  928                 wakeup_swapper = thread_unsuspend_one(p->p_singlethread);
  929                 thread_unlock(p->p_singlethread);
  930         }
  931         if (wakeup_swapper)
  932                 kick_proc0();
  933 }
  934 
  935 /*
  936  * End the single threading mode..
  937  */
  938 void
  939 thread_single_end(void)
  940 {
  941         struct thread *td;
  942         struct proc *p;
  943         int wakeup_swapper;
  944 
  945         td = curthread;
  946         p = td->td_proc;
  947         PROC_LOCK_ASSERT(p, MA_OWNED);
  948         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
  949         PROC_SLOCK(p);
  950         p->p_singlethread = NULL;
  951         wakeup_swapper = 0;
  952         /*
  953          * If there are other threads they may now run,
  954          * unless of course there is a blanket 'stop order'
  955          * on the process. The single threader must be allowed
  956          * to continue however as this is a bad place to stop.
  957          */
  958         if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
  959                 FOREACH_THREAD_IN_PROC(p, td) {
  960                         thread_lock(td);
  961                         if (TD_IS_SUSPENDED(td)) {
  962                                 wakeup_swapper |= thread_unsuspend_one(td);
  963                         }
  964                         thread_unlock(td);
  965                 }
  966         }
  967         PROC_SUNLOCK(p);
  968         if (wakeup_swapper)
  969                 kick_proc0();
  970 }
  971 
  972 struct thread *
  973 thread_find(struct proc *p, lwpid_t tid)
  974 {
  975         struct thread *td;
  976 
  977         PROC_LOCK_ASSERT(p, MA_OWNED);
  978         FOREACH_THREAD_IN_PROC(p, td) {
  979                 if (td->td_tid == tid)
  980                         break;
  981         }
  982         return (td);
  983 }
  984 
  985 /* Locate a thread by number; return with proc lock held. */
  986 struct thread *
  987 tdfind(lwpid_t tid, pid_t pid)
  988 {
  989 #define RUN_THRESH      16
  990         struct thread *td;
  991         int run = 0;
  992 
  993         rw_rlock(&tidhash_lock);
  994         LIST_FOREACH(td, TIDHASH(tid), td_hash) {
  995                 if (td->td_tid == tid) {
  996                         if (pid != -1 && td->td_proc->p_pid != pid) {
  997                                 td = NULL;
  998                                 break;
  999                         }
 1000                         PROC_LOCK(td->td_proc);
 1001                         if (td->td_proc->p_state == PRS_NEW) {
 1002                                 PROC_UNLOCK(td->td_proc);
 1003                                 td = NULL;
 1004                                 break;
 1005                         }
 1006                         if (run > RUN_THRESH) {
 1007                                 if (rw_try_upgrade(&tidhash_lock)) {
 1008                                         LIST_REMOVE(td, td_hash);
 1009                                         LIST_INSERT_HEAD(TIDHASH(td->td_tid),
 1010                                                 td, td_hash);
 1011                                         rw_wunlock(&tidhash_lock);
 1012                                         return (td);
 1013                                 }
 1014                         }
 1015                         break;
 1016                 }
 1017                 run++;
 1018         }
 1019         rw_runlock(&tidhash_lock);
 1020         return (td);
 1021 }
 1022 
 1023 void
 1024 tidhash_add(struct thread *td)
 1025 {
 1026         rw_wlock(&tidhash_lock);
 1027         LIST_INSERT_HEAD(TIDHASH(td->td_tid), td, td_hash);
 1028         rw_wunlock(&tidhash_lock);
 1029 }
 1030 
 1031 void
 1032 tidhash_remove(struct thread *td)
 1033 {
 1034         rw_wlock(&tidhash_lock);
 1035         LIST_REMOVE(td, td_hash);
 1036         rw_wunlock(&tidhash_lock);
 1037 }

Cache object: a6490ff4523b787c921d1a7a908deee5


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