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 <sys/cdefs.h>
   30 __FBSDID("$FreeBSD: releng/6.0/sys/kern/kern_thread.c 150951 2005-10-04 22:53:56Z davidxu $");
   31 
   32 #include <sys/param.h>
   33 #include <sys/systm.h>
   34 #include <sys/kernel.h>
   35 #include <sys/lock.h>
   36 #include <sys/mutex.h>
   37 #include <sys/proc.h>
   38 #include <sys/smp.h>
   39 #include <sys/sysctl.h>
   40 #include <sys/sched.h>
   41 #include <sys/sleepqueue.h>
   42 #include <sys/turnstile.h>
   43 #include <sys/ktr.h>
   44 #include <sys/umtx.h>
   45 
   46 #include <vm/vm.h>
   47 #include <vm/vm_extern.h>
   48 #include <vm/uma.h>
   49 
   50 /*
   51  * KSEGRP related storage.
   52  */
   53 static uma_zone_t ksegrp_zone;
   54 static uma_zone_t thread_zone;
   55 
   56 /* DEBUG ONLY */
   57 SYSCTL_NODE(_kern, OID_AUTO, threads, CTLFLAG_RW, 0, "thread allocation");
   58 static int thread_debug = 0;
   59 SYSCTL_INT(_kern_threads, OID_AUTO, debug, CTLFLAG_RW,
   60         &thread_debug, 0, "thread debug");
   61 
   62 int max_threads_per_proc = 1500;
   63 SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_per_proc, CTLFLAG_RW,
   64         &max_threads_per_proc, 0, "Limit on threads per proc");
   65 
   66 int max_groups_per_proc = 1500;
   67 SYSCTL_INT(_kern_threads, OID_AUTO, max_groups_per_proc, CTLFLAG_RW,
   68         &max_groups_per_proc, 0, "Limit on thread groups per proc");
   69 
   70 int max_threads_hits;
   71 SYSCTL_INT(_kern_threads, OID_AUTO, max_threads_hits, CTLFLAG_RD,
   72         &max_threads_hits, 0, "");
   73 
   74 int virtual_cpu;
   75 
   76 TAILQ_HEAD(, thread) zombie_threads = TAILQ_HEAD_INITIALIZER(zombie_threads);
   77 TAILQ_HEAD(, ksegrp) zombie_ksegrps = TAILQ_HEAD_INITIALIZER(zombie_ksegrps);
   78 struct mtx kse_zombie_lock;
   79 MTX_SYSINIT(kse_zombie_lock, &kse_zombie_lock, "kse zombie lock", MTX_SPIN);
   80 
   81 static int
   82 sysctl_kse_virtual_cpu(SYSCTL_HANDLER_ARGS)
   83 {
   84         int error, new_val;
   85         int def_val;
   86 
   87         def_val = mp_ncpus;
   88         if (virtual_cpu == 0)
   89                 new_val = def_val;
   90         else
   91                 new_val = virtual_cpu;
   92         error = sysctl_handle_int(oidp, &new_val, 0, req);
   93         if (error != 0 || req->newptr == NULL)
   94                 return (error);
   95         if (new_val < 0)
   96                 return (EINVAL);
   97         virtual_cpu = new_val;
   98         return (0);
   99 }
  100 
  101 /* DEBUG ONLY */
  102 SYSCTL_PROC(_kern_threads, OID_AUTO, virtual_cpu, CTLTYPE_INT|CTLFLAG_RW,
  103         0, sizeof(virtual_cpu), sysctl_kse_virtual_cpu, "I",
  104         "debug virtual cpus");
  105 
  106 struct mtx tid_lock;
  107 static struct unrhdr *tid_unrhdr;
  108 
  109 /*
  110  * Prepare a thread for use.
  111  */
  112 static int
  113 thread_ctor(void *mem, int size, void *arg, int flags)
  114 {
  115         struct thread   *td;
  116 
  117         td = (struct thread *)mem;
  118         td->td_state = TDS_INACTIVE;
  119         td->td_oncpu = NOCPU;
  120 
  121         td->td_tid = alloc_unr(tid_unrhdr);
  122 
  123         /*
  124          * Note that td_critnest begins life as 1 because the thread is not
  125          * running and is thereby implicitly waiting to be on the receiving
  126          * end of a context switch.  A context switch must occur inside a
  127          * critical section, and in fact, includes hand-off of the sched_lock.
  128          * After a context switch to a newly created thread, it will release
  129          * sched_lock for the first time, and its td_critnest will hit 0 for
  130          * the first time.  This happens on the far end of a context switch,
  131          * and when it context switches away from itself, it will in fact go
  132          * back into a critical section, and hand off the sched lock to the
  133          * next thread.
  134          */
  135         td->td_critnest = 1;
  136         return (0);
  137 }
  138 
  139 /*
  140  * Reclaim a thread after use.
  141  */
  142 static void
  143 thread_dtor(void *mem, int size, void *arg)
  144 {
  145         struct thread *td;
  146 
  147         td = (struct thread *)mem;
  148 
  149 #ifdef INVARIANTS
  150         /* Verify that this thread is in a safe state to free. */
  151         switch (td->td_state) {
  152         case TDS_INHIBITED:
  153         case TDS_RUNNING:
  154         case TDS_CAN_RUN:
  155         case TDS_RUNQ:
  156                 /*
  157                  * We must never unlink a thread that is in one of
  158                  * these states, because it is currently active.
  159                  */
  160                 panic("bad state for thread unlinking");
  161                 /* NOTREACHED */
  162         case TDS_INACTIVE:
  163                 break;
  164         default:
  165                 panic("bad thread state");
  166                 /* NOTREACHED */
  167         }
  168 #endif
  169 
  170         free_unr(tid_unrhdr, td->td_tid);
  171         sched_newthread(td);
  172 }
  173 
  174 /*
  175  * Initialize type-stable parts of a thread (when newly created).
  176  */
  177 static int
  178 thread_init(void *mem, int size, int flags)
  179 {
  180         struct thread *td;
  181 
  182         td = (struct thread *)mem;
  183 
  184         vm_thread_new(td, 0);
  185         cpu_thread_setup(td);
  186         td->td_sleepqueue = sleepq_alloc();
  187         td->td_turnstile = turnstile_alloc();
  188         td->td_umtxq = umtxq_alloc();
  189         td->td_sched = (struct td_sched *)&td[1];
  190         sched_newthread(td);
  191         return (0);
  192 }
  193 
  194 /*
  195  * Tear down type-stable parts of a thread (just before being discarded).
  196  */
  197 static void
  198 thread_fini(void *mem, int size)
  199 {
  200         struct thread *td;
  201 
  202         td = (struct thread *)mem;
  203         turnstile_free(td->td_turnstile);
  204         sleepq_free(td->td_sleepqueue);
  205         umtxq_free(td->td_umtxq);
  206         vm_thread_dispose(td);
  207 }
  208 
  209 /*
  210  * Initialize type-stable parts of a ksegrp (when newly created).
  211  */
  212 static int
  213 ksegrp_ctor(void *mem, int size, void *arg, int flags)
  214 {
  215         struct ksegrp   *kg;
  216 
  217         kg = (struct ksegrp *)mem;
  218         bzero(mem, size);
  219         kg->kg_sched = (struct kg_sched *)&kg[1];
  220         return (0);
  221 }
  222 
  223 void
  224 ksegrp_link(struct ksegrp *kg, struct proc *p)
  225 {
  226 
  227         TAILQ_INIT(&kg->kg_threads);
  228         TAILQ_INIT(&kg->kg_runq);       /* links with td_runq */
  229         TAILQ_INIT(&kg->kg_upcalls);    /* all upcall structure in ksegrp */
  230         kg->kg_proc = p;
  231         /*
  232          * the following counters are in the -zero- section
  233          * and may not need clearing
  234          */
  235         kg->kg_numthreads = 0;
  236         kg->kg_numupcalls = 0;
  237         /* link it in now that it's consistent */
  238         p->p_numksegrps++;
  239         TAILQ_INSERT_HEAD(&p->p_ksegrps, kg, kg_ksegrp);
  240 }
  241 
  242 /*
  243  * Called from:
  244  *   thread-exit()
  245  */
  246 void
  247 ksegrp_unlink(struct ksegrp *kg)
  248 {
  249         struct proc *p;
  250 
  251         mtx_assert(&sched_lock, MA_OWNED);
  252         KASSERT((kg->kg_numthreads == 0), ("ksegrp_unlink: residual threads"));
  253         KASSERT((kg->kg_numupcalls == 0), ("ksegrp_unlink: residual upcalls"));
  254 
  255         p = kg->kg_proc;
  256         TAILQ_REMOVE(&p->p_ksegrps, kg, kg_ksegrp);
  257         p->p_numksegrps--;
  258         /*
  259          * Aggregate stats from the KSE
  260          */
  261         if (p->p_procscopegrp == kg)
  262                 p->p_procscopegrp = NULL;
  263 }
  264 
  265 /*
  266  * For a newly created process,
  267  * link up all the structures and its initial threads etc.
  268  * called from:
  269  * {arch}/{arch}/machdep.c   ia64_init(), init386() etc.
  270  * proc_dtor() (should go away)
  271  * proc_init()
  272  */
  273 void
  274 proc_linkup(struct proc *p, struct ksegrp *kg, struct thread *td)
  275 {
  276 
  277         TAILQ_INIT(&p->p_ksegrps);           /* all ksegrps in proc */
  278         TAILQ_INIT(&p->p_threads);           /* all threads in proc */
  279         TAILQ_INIT(&p->p_suspended);         /* Threads suspended */
  280         p->p_numksegrps = 0;
  281         p->p_numthreads = 0;
  282 
  283         ksegrp_link(kg, p);
  284         thread_link(td, kg);
  285 }
  286 
  287 /*
  288  * Initialize global thread allocation resources.
  289  */
  290 void
  291 threadinit(void)
  292 {
  293 
  294         mtx_init(&tid_lock, "TID lock", NULL, MTX_DEF);
  295         tid_unrhdr = new_unrhdr(PID_MAX + 1, INT_MAX, &tid_lock);
  296 
  297         thread_zone = uma_zcreate("THREAD", sched_sizeof_thread(),
  298             thread_ctor, thread_dtor, thread_init, thread_fini,
  299             UMA_ALIGN_CACHE, 0);
  300         ksegrp_zone = uma_zcreate("KSEGRP", sched_sizeof_ksegrp(),
  301             ksegrp_ctor, NULL, NULL, NULL,
  302             UMA_ALIGN_CACHE, 0);
  303         kseinit();      /* set up kse specific stuff  e.g. upcall zone*/
  304 }
  305 
  306 /*
  307  * Stash an embarasingly extra thread into the zombie thread queue.
  308  */
  309 void
  310 thread_stash(struct thread *td)
  311 {
  312         mtx_lock_spin(&kse_zombie_lock);
  313         TAILQ_INSERT_HEAD(&zombie_threads, td, td_runq);
  314         mtx_unlock_spin(&kse_zombie_lock);
  315 }
  316 
  317 /*
  318  * Stash an embarasingly extra ksegrp into the zombie ksegrp queue.
  319  */
  320 void
  321 ksegrp_stash(struct ksegrp *kg)
  322 {
  323         mtx_lock_spin(&kse_zombie_lock);
  324         TAILQ_INSERT_HEAD(&zombie_ksegrps, kg, kg_ksegrp);
  325         mtx_unlock_spin(&kse_zombie_lock);
  326 }
  327 
  328 /*
  329  * Reap zombie kse resource.
  330  */
  331 void
  332 thread_reap(void)
  333 {
  334         struct thread *td_first, *td_next;
  335         struct ksegrp *kg_first, * kg_next;
  336 
  337         /*
  338          * Don't even bother to lock if none at this instant,
  339          * we really don't care about the next instant..
  340          */
  341         if ((!TAILQ_EMPTY(&zombie_threads))
  342             || (!TAILQ_EMPTY(&zombie_ksegrps))) {
  343                 mtx_lock_spin(&kse_zombie_lock);
  344                 td_first = TAILQ_FIRST(&zombie_threads);
  345                 kg_first = TAILQ_FIRST(&zombie_ksegrps);
  346                 if (td_first)
  347                         TAILQ_INIT(&zombie_threads);
  348                 if (kg_first)
  349                         TAILQ_INIT(&zombie_ksegrps);
  350                 mtx_unlock_spin(&kse_zombie_lock);
  351                 while (td_first) {
  352                         td_next = TAILQ_NEXT(td_first, td_runq);
  353                         if (td_first->td_ucred)
  354                                 crfree(td_first->td_ucred);
  355                         thread_free(td_first);
  356                         td_first = td_next;
  357                 }
  358                 while (kg_first) {
  359                         kg_next = TAILQ_NEXT(kg_first, kg_ksegrp);
  360                         ksegrp_free(kg_first);
  361                         kg_first = kg_next;
  362                 }
  363                 /*
  364                  * there will always be a thread on the list if one of these
  365                  * is there.
  366                  */
  367                 kse_GC();
  368         }
  369 }
  370 
  371 /*
  372  * Allocate a ksegrp.
  373  */
  374 struct ksegrp *
  375 ksegrp_alloc(void)
  376 {
  377         return (uma_zalloc(ksegrp_zone, M_WAITOK));
  378 }
  379 
  380 /*
  381  * Allocate a thread.
  382  */
  383 struct thread *
  384 thread_alloc(void)
  385 {
  386         thread_reap(); /* check if any zombies to get */
  387         return (uma_zalloc(thread_zone, M_WAITOK));
  388 }
  389 
  390 /*
  391  * Deallocate a ksegrp.
  392  */
  393 void
  394 ksegrp_free(struct ksegrp *td)
  395 {
  396         uma_zfree(ksegrp_zone, td);
  397 }
  398 
  399 /*
  400  * Deallocate a thread.
  401  */
  402 void
  403 thread_free(struct thread *td)
  404 {
  405 
  406         cpu_thread_clean(td);
  407         uma_zfree(thread_zone, td);
  408 }
  409 
  410 /*
  411  * Discard the current thread and exit from its context.
  412  * Always called with scheduler locked.
  413  *
  414  * Because we can't free a thread while we're operating under its context,
  415  * push the current thread into our CPU's deadthread holder. This means
  416  * we needn't worry about someone else grabbing our context before we
  417  * do a cpu_throw().  This may not be needed now as we are under schedlock.
  418  * Maybe we can just do a thread_stash() as thr_exit1 does.
  419  */
  420 /*  XXX
  421  * libthr expects its thread exit to return for the last
  422  * thread, meaning that the program is back to non-threaded
  423  * mode I guess. Because we do this (cpu_throw) unconditionally
  424  * here, they have their own version of it. (thr_exit1()) 
  425  * that doesn't do it all if this was the last thread.
  426  * It is also called from thread_suspend_check().
  427  * Of course in the end, they end up coming here through exit1
  428  * anyhow..  After fixing 'thr' to play by the rules we should be able 
  429  * to merge these two functions together.
  430  *
  431  * called from:
  432  * exit1()
  433  * kse_exit()
  434  * thr_exit()
  435  * thread_user_enter()
  436  * thread_userret()
  437  * thread_suspend_check()
  438  */
  439 void
  440 thread_exit(void)
  441 {
  442         struct thread *td;
  443         struct proc *p;
  444         struct ksegrp   *kg;
  445 
  446         td = curthread;
  447         kg = td->td_ksegrp;
  448         p = td->td_proc;
  449 
  450         mtx_assert(&sched_lock, MA_OWNED);
  451         mtx_assert(&Giant, MA_NOTOWNED);
  452         PROC_LOCK_ASSERT(p, MA_OWNED);
  453         KASSERT(p != NULL, ("thread exiting without a process"));
  454         KASSERT(kg != NULL, ("thread exiting without a kse group"));
  455         CTR3(KTR_PROC, "thread_exit: thread %p (pid %ld, %s)", td,
  456             (long)p->p_pid, p->p_comm);
  457 
  458         if (td->td_standin != NULL) {
  459                 /*
  460                  * Note that we don't need to free the cred here as it
  461                  * is done in thread_reap().
  462                  */
  463                 thread_stash(td->td_standin);
  464                 td->td_standin = NULL;
  465         }
  466 
  467         /*
  468          * drop FPU & debug register state storage, or any other
  469          * architecture specific resources that
  470          * would not be on a new untouched process.
  471          */
  472         cpu_thread_exit(td);    /* XXXSMP */
  473 
  474         /*
  475          * The thread is exiting. scheduler can release its stuff
  476          * and collect stats etc.
  477          */
  478         sched_thread_exit(td);
  479 
  480         /*
  481          * The last thread is left attached to the process
  482          * So that the whole bundle gets recycled. Skip
  483          * all this stuff if we never had threads.
  484          * EXIT clears all sign of other threads when
  485          * it goes to single threading, so the last thread always
  486          * takes the short path.
  487          */
  488         if (p->p_flag & P_HADTHREADS) {
  489                 if (p->p_numthreads > 1) {
  490                         thread_unlink(td);
  491 
  492                         /* XXX first arg not used in 4BSD or ULE */
  493                         sched_exit_thread(FIRST_THREAD_IN_PROC(p), td);
  494 
  495                         /*
  496                          * The test below is NOT true if we are the
  497                          * sole exiting thread. P_STOPPED_SNGL is unset
  498                          * in exit1() after it is the only survivor.
  499                          */
  500                         if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  501                                 if (p->p_numthreads == p->p_suspcount) {
  502                                         thread_unsuspend_one(p->p_singlethread);
  503                                 }
  504                         }
  505 
  506                         /*
  507                          * Because each upcall structure has an owner thread,
  508                          * owner thread exits only when process is in exiting
  509                          * state, so upcall to userland is no longer needed,
  510                          * deleting upcall structure is safe here.
  511                          * So when all threads in a group is exited, all upcalls
  512                          * in the group should be automatically freed.
  513                          *  XXXKSE This is a KSE thing and should be exported
  514                          * there somehow.
  515                          */
  516                         upcall_remove(td);
  517 
  518                         /*
  519                          * If the thread we unlinked above was the last one,
  520                          * then this ksegrp should go away too.
  521                          */
  522                         if (kg->kg_numthreads == 0) {
  523                                 /*
  524                                  * let the scheduler know about this in case
  525                                  * it needs to recover stats or resources.
  526                                  * Theoretically we could let
  527                                  * sched_exit_ksegrp()  do the equivalent of
  528                                  * setting the concurrency to 0
  529                                  * but don't do it yet to avoid changing
  530                                  * the existing scheduler code until we
  531                                  * are ready.
  532                                  * We supply a random other ksegrp
  533                                  * as the recipient of any built up
  534                                  * cpu usage etc. (If the scheduler wants it).
  535                                  * XXXKSE
  536                                  * This is probably not fair so think of
  537                                  * a better answer.
  538                                  */
  539                                 sched_exit_ksegrp(FIRST_KSEGRP_IN_PROC(p), td);
  540                                 sched_set_concurrency(kg, 0); /* XXX TEMP */
  541                                 ksegrp_unlink(kg);
  542                                 ksegrp_stash(kg);
  543                         }
  544                         PROC_UNLOCK(p);
  545                         td->td_ksegrp   = NULL;
  546                         PCPU_SET(deadthread, td);
  547                 } else {
  548                         /*
  549                          * The last thread is exiting.. but not through exit()
  550                          * what should we do?
  551                          * Theoretically this can't happen
  552                          * exit1() - clears threading flags before coming here
  553                          * kse_exit() - treats last thread specially
  554                          * thr_exit() - treats last thread specially
  555                          * thread_user_enter() - only if more exist
  556                          * thread_userret() - only if more exist
  557                          * thread_suspend_check() - only if more exist
  558                          */
  559                         panic ("thread_exit: Last thread exiting on its own");
  560                 }
  561         } else {
  562                 /*
  563                  * non threaded process comes here.
  564                  * This includes an EX threaded process that is coming
  565                  * here via exit1(). (exit1 dethreads the proc first).
  566                  */
  567                 PROC_UNLOCK(p);
  568         }
  569         td->td_state = TDS_INACTIVE;
  570         CTR1(KTR_PROC, "thread_exit: cpu_throw() thread %p", td);
  571         cpu_throw(td, choosethread());
  572         panic("I'm a teapot!");
  573         /* NOTREACHED */
  574 }
  575 
  576 /*
  577  * Do any thread specific cleanups that may be needed in wait()
  578  * called with Giant, proc and schedlock not held.
  579  */
  580 void
  581 thread_wait(struct proc *p)
  582 {
  583         struct thread *td;
  584 
  585         mtx_assert(&Giant, MA_NOTOWNED);
  586         KASSERT((p->p_numthreads == 1), ("Multiple threads in wait1()"));
  587         KASSERT((p->p_numksegrps == 1), ("Multiple ksegrps in wait1()"));
  588         FOREACH_THREAD_IN_PROC(p, td) {
  589                 if (td->td_standin != NULL) {
  590                         if (td->td_standin->td_ucred != NULL) {
  591                                 crfree(td->td_standin->td_ucred);
  592                                 td->td_standin->td_ucred = NULL;
  593                         }
  594                         thread_free(td->td_standin);
  595                         td->td_standin = NULL;
  596                 }
  597                 cpu_thread_clean(td);
  598                 crfree(td->td_ucred);
  599         }
  600         thread_reap();  /* check for zombie threads etc. */
  601 }
  602 
  603 /*
  604  * Link a thread to a process.
  605  * set up anything that needs to be initialized for it to
  606  * be used by the process.
  607  *
  608  * Note that we do not link to the proc's ucred here.
  609  * The thread is linked as if running but no KSE assigned.
  610  * Called from:
  611  *  proc_linkup()
  612  *  thread_schedule_upcall()
  613  *  thr_create()
  614  */
  615 void
  616 thread_link(struct thread *td, struct ksegrp *kg)
  617 {
  618         struct proc *p;
  619 
  620         p = kg->kg_proc;
  621         td->td_state    = TDS_INACTIVE;
  622         td->td_proc     = p;
  623         td->td_ksegrp   = kg;
  624         td->td_flags    = 0;
  625         td->td_kflags   = 0;
  626 
  627         LIST_INIT(&td->td_contested);
  628         callout_init(&td->td_slpcallout, CALLOUT_MPSAFE);
  629         TAILQ_INSERT_HEAD(&p->p_threads, td, td_plist);
  630         TAILQ_INSERT_HEAD(&kg->kg_threads, td, td_kglist);
  631         p->p_numthreads++;
  632         kg->kg_numthreads++;
  633 }
  634 
  635 /*
  636  * Convert a process with one thread to an unthreaded process.
  637  * Called from:
  638  *  thread_single(exit)  (called from execve and exit)
  639  *  kse_exit()          XXX may need cleaning up wrt KSE stuff
  640  */
  641 void
  642 thread_unthread(struct thread *td)
  643 {
  644         struct proc *p = td->td_proc;
  645 
  646         KASSERT((p->p_numthreads == 1), ("Unthreading with >1 threads"));
  647         upcall_remove(td);
  648         p->p_flag &= ~(P_SA|P_HADTHREADS);
  649         td->td_mailbox = NULL;
  650         td->td_pflags &= ~(TDP_SA | TDP_CAN_UNBIND);
  651         if (td->td_standin != NULL) {
  652                 thread_stash(td->td_standin);
  653                 td->td_standin = NULL;
  654         }
  655         sched_set_concurrency(td->td_ksegrp, 1);
  656 }
  657 
  658 /*
  659  * Called from:
  660  *  thread_exit()
  661  */
  662 void
  663 thread_unlink(struct thread *td)
  664 {
  665         struct proc *p = td->td_proc;
  666         struct ksegrp *kg = td->td_ksegrp;
  667 
  668         mtx_assert(&sched_lock, MA_OWNED);
  669         TAILQ_REMOVE(&p->p_threads, td, td_plist);
  670         p->p_numthreads--;
  671         TAILQ_REMOVE(&kg->kg_threads, td, td_kglist);
  672         kg->kg_numthreads--;
  673         /* could clear a few other things here */
  674         /* Must  NOT clear links to proc and ksegrp! */
  675 }
  676 
  677 /*
  678  * Enforce single-threading.
  679  *
  680  * Returns 1 if the caller must abort (another thread is waiting to
  681  * exit the process or similar). Process is locked!
  682  * Returns 0 when you are successfully the only thread running.
  683  * A process has successfully single threaded in the suspend mode when
  684  * There are no threads in user mode. Threads in the kernel must be
  685  * allowed to continue until they get to the user boundary. They may even
  686  * copy out their return values and data before suspending. They may however be
  687  * accellerated in reaching the user boundary as we will wake up
  688  * any sleeping threads that are interruptable. (PCATCH).
  689  */
  690 int
  691 thread_single(int mode)
  692 {
  693         struct thread *td;
  694         struct thread *td2;
  695         struct proc *p;
  696         int remaining;
  697 
  698         td = curthread;
  699         p = td->td_proc;
  700         mtx_assert(&Giant, MA_NOTOWNED);
  701         PROC_LOCK_ASSERT(p, MA_OWNED);
  702         KASSERT((td != NULL), ("curthread is NULL"));
  703 
  704         if ((p->p_flag & P_HADTHREADS) == 0)
  705                 return (0);
  706 
  707         /* Is someone already single threading? */
  708         if (p->p_singlethread != NULL && p->p_singlethread != td)
  709                 return (1);
  710 
  711         if (mode == SINGLE_EXIT) {
  712                 p->p_flag |= P_SINGLE_EXIT;
  713                 p->p_flag &= ~P_SINGLE_BOUNDARY;
  714         } else {
  715                 p->p_flag &= ~P_SINGLE_EXIT;
  716                 if (mode == SINGLE_BOUNDARY)
  717                         p->p_flag |= P_SINGLE_BOUNDARY;
  718                 else
  719                         p->p_flag &= ~P_SINGLE_BOUNDARY;
  720         }
  721         p->p_flag |= P_STOPPED_SINGLE;
  722         mtx_lock_spin(&sched_lock);
  723         p->p_singlethread = td;
  724         if (mode == SINGLE_EXIT)
  725                 remaining = p->p_numthreads;
  726         else if (mode == SINGLE_BOUNDARY)
  727                 remaining = p->p_numthreads - p->p_boundary_count;
  728         else
  729                 remaining = p->p_numthreads - p->p_suspcount;
  730         while (remaining != 1) {
  731                 FOREACH_THREAD_IN_PROC(p, td2) {
  732                         if (td2 == td)
  733                                 continue;
  734                         td2->td_flags |= TDF_ASTPENDING;
  735                         if (TD_IS_INHIBITED(td2)) {
  736                                 switch (mode) {
  737                                 case SINGLE_EXIT:
  738                                         if (td->td_flags & TDF_DBSUSPEND)
  739                                                 td->td_flags &= ~TDF_DBSUSPEND;
  740                                         if (TD_IS_SUSPENDED(td2))
  741                                                 thread_unsuspend_one(td2);
  742                                         if (TD_ON_SLEEPQ(td2) &&
  743                                             (td2->td_flags & TDF_SINTR))
  744                                                 sleepq_abort(td2);
  745                                         break;
  746                                 case SINGLE_BOUNDARY:
  747                                         if (TD_IS_SUSPENDED(td2) &&
  748                                             !(td2->td_flags & TDF_BOUNDARY))
  749                                                 thread_unsuspend_one(td2);
  750                                         if (TD_ON_SLEEPQ(td2) &&
  751                                             (td2->td_flags & TDF_SINTR))
  752                                                 sleepq_abort(td2);
  753                                         break;
  754                                 default:        
  755                                         if (TD_IS_SUSPENDED(td2))
  756                                                 continue;
  757                                         /*
  758                                          * maybe other inhibitted states too?
  759                                          */
  760                                         if ((td2->td_flags & TDF_SINTR) &&
  761                                             (td2->td_inhibitors &
  762                                             (TDI_SLEEPING | TDI_SWAPPED)))
  763                                                 thread_suspend_one(td2);
  764                                         break;
  765                                 }
  766                         }
  767                 }
  768                 if (mode == SINGLE_EXIT)
  769                         remaining = p->p_numthreads;
  770                 else if (mode == SINGLE_BOUNDARY)
  771                         remaining = p->p_numthreads - p->p_boundary_count;
  772                 else
  773                         remaining = p->p_numthreads - p->p_suspcount;
  774 
  775                 /*
  776                  * Maybe we suspended some threads.. was it enough?
  777                  */
  778                 if (remaining == 1)
  779                         break;
  780 
  781                 /*
  782                  * Wake us up when everyone else has suspended.
  783                  * In the mean time we suspend as well.
  784                  */
  785                 thread_suspend_one(td);
  786                 PROC_UNLOCK(p);
  787                 mi_switch(SW_VOL, NULL);
  788                 mtx_unlock_spin(&sched_lock);
  789                 PROC_LOCK(p);
  790                 mtx_lock_spin(&sched_lock);
  791                 if (mode == SINGLE_EXIT)
  792                         remaining = p->p_numthreads;
  793                 else if (mode == SINGLE_BOUNDARY)
  794                         remaining = p->p_numthreads - p->p_boundary_count;
  795                 else
  796                         remaining = p->p_numthreads - p->p_suspcount;
  797         }
  798         if (mode == SINGLE_EXIT) {
  799                 /*
  800                  * We have gotten rid of all the other threads and we
  801                  * are about to either exit or exec. In either case,
  802                  * we try our utmost  to revert to being a non-threaded
  803                  * process.
  804                  */
  805                 p->p_singlethread = NULL;
  806                 p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT);
  807                 thread_unthread(td);
  808         }
  809         mtx_unlock_spin(&sched_lock);
  810         return (0);
  811 }
  812 
  813 /*
  814  * Called in from locations that can safely check to see
  815  * whether we have to suspend or at least throttle for a
  816  * single-thread event (e.g. fork).
  817  *
  818  * Such locations include userret().
  819  * If the "return_instead" argument is non zero, the thread must be able to
  820  * accept 0 (caller may continue), or 1 (caller must abort) as a result.
  821  *
  822  * The 'return_instead' argument tells the function if it may do a
  823  * thread_exit() or suspend, or whether the caller must abort and back
  824  * out instead.
  825  *
  826  * If the thread that set the single_threading request has set the
  827  * P_SINGLE_EXIT bit in the process flags then this call will never return
  828  * if 'return_instead' is false, but will exit.
  829  *
  830  * P_SINGLE_EXIT | return_instead == 0| return_instead != 0
  831  *---------------+--------------------+---------------------
  832  *       0       | returns 0          |   returns 0 or 1
  833  *               | when ST ends       |   immediatly
  834  *---------------+--------------------+---------------------
  835  *       1       | thread exits       |   returns 1
  836  *               |                    |  immediatly
  837  * 0 = thread_exit() or suspension ok,
  838  * other = return error instead of stopping the thread.
  839  *
  840  * While a full suspension is under effect, even a single threading
  841  * thread would be suspended if it made this call (but it shouldn't).
  842  * This call should only be made from places where
  843  * thread_exit() would be safe as that may be the outcome unless
  844  * return_instead is set.
  845  */
  846 int
  847 thread_suspend_check(int return_instead)
  848 {
  849         struct thread *td;
  850         struct proc *p;
  851 
  852         td = curthread;
  853         p = td->td_proc;
  854         mtx_assert(&Giant, MA_NOTOWNED);
  855         PROC_LOCK_ASSERT(p, MA_OWNED);
  856         while (P_SHOULDSTOP(p) ||
  857               ((p->p_flag & P_TRACED) && (td->td_flags & TDF_DBSUSPEND))) {
  858                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  859                         KASSERT(p->p_singlethread != NULL,
  860                             ("singlethread not set"));
  861                         /*
  862                          * The only suspension in action is a
  863                          * single-threading. Single threader need not stop.
  864                          * XXX Should be safe to access unlocked
  865                          * as it can only be set to be true by us.
  866                          */
  867                         if (p->p_singlethread == td)
  868                                 return (0);     /* Exempt from stopping. */
  869                 }
  870                 if ((p->p_flag & P_SINGLE_EXIT) && return_instead)
  871                         return (1);
  872 
  873                 /* Should we goto user boundary if we didn't come from there? */
  874                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE &&
  875                     (p->p_flag & P_SINGLE_BOUNDARY) && return_instead)
  876                         return (1);
  877 
  878                 mtx_lock_spin(&sched_lock);
  879                 thread_stopped(p);
  880                 /*
  881                  * If the process is waiting for us to exit,
  882                  * this thread should just suicide.
  883                  * Assumes that P_SINGLE_EXIT implies P_STOPPED_SINGLE.
  884                  */
  885                 if ((p->p_flag & P_SINGLE_EXIT) && (p->p_singlethread != td))
  886                         thread_exit();
  887 
  888                 /*
  889                  * When a thread suspends, it just
  890                  * moves to the processes's suspend queue
  891                  * and stays there.
  892                  */
  893                 thread_suspend_one(td);
  894                 if (return_instead == 0) {
  895                         p->p_boundary_count++;
  896                         td->td_flags |= TDF_BOUNDARY;
  897                 }
  898                 if (P_SHOULDSTOP(p) == P_STOPPED_SINGLE) {
  899                         if (p->p_numthreads == p->p_suspcount) 
  900                                 thread_unsuspend_one(p->p_singlethread);
  901                 }
  902                 PROC_UNLOCK(p);
  903                 mi_switch(SW_INVOL, NULL);
  904                 if (return_instead == 0) {
  905                         p->p_boundary_count--;
  906                         td->td_flags &= ~TDF_BOUNDARY;
  907                 }
  908                 mtx_unlock_spin(&sched_lock);
  909                 PROC_LOCK(p);
  910         }
  911         return (0);
  912 }
  913 
  914 void
  915 thread_suspend_one(struct thread *td)
  916 {
  917         struct proc *p = td->td_proc;
  918 
  919         mtx_assert(&sched_lock, MA_OWNED);
  920         PROC_LOCK_ASSERT(p, MA_OWNED);
  921         KASSERT(!TD_IS_SUSPENDED(td), ("already suspended"));
  922         p->p_suspcount++;
  923         TD_SET_SUSPENDED(td);
  924         TAILQ_INSERT_TAIL(&p->p_suspended, td, td_runq);
  925 }
  926 
  927 void
  928 thread_unsuspend_one(struct thread *td)
  929 {
  930         struct proc *p = td->td_proc;
  931 
  932         mtx_assert(&sched_lock, MA_OWNED);
  933         PROC_LOCK_ASSERT(p, MA_OWNED);
  934         TAILQ_REMOVE(&p->p_suspended, td, td_runq);
  935         TD_CLR_SUSPENDED(td);
  936         p->p_suspcount--;
  937         setrunnable(td);
  938 }
  939 
  940 /*
  941  * Allow all threads blocked by single threading to continue running.
  942  */
  943 void
  944 thread_unsuspend(struct proc *p)
  945 {
  946         struct thread *td;
  947 
  948         mtx_assert(&sched_lock, MA_OWNED);
  949         PROC_LOCK_ASSERT(p, MA_OWNED);
  950         if (!P_SHOULDSTOP(p)) {
  951                 while ((td = TAILQ_FIRST(&p->p_suspended))) {
  952                         thread_unsuspend_one(td);
  953                 }
  954         } else if ((P_SHOULDSTOP(p) == P_STOPPED_SINGLE) &&
  955             (p->p_numthreads == p->p_suspcount)) {
  956                 /*
  957                  * Stopping everything also did the job for the single
  958                  * threading request. Now we've downgraded to single-threaded,
  959                  * let it continue.
  960                  */
  961                 thread_unsuspend_one(p->p_singlethread);
  962         }
  963 }
  964 
  965 /*
  966  * End the single threading mode..
  967  */
  968 void
  969 thread_single_end(void)
  970 {
  971         struct thread *td;
  972         struct proc *p;
  973 
  974         td = curthread;
  975         p = td->td_proc;
  976         PROC_LOCK_ASSERT(p, MA_OWNED);
  977         p->p_flag &= ~(P_STOPPED_SINGLE | P_SINGLE_EXIT | P_SINGLE_BOUNDARY);
  978         mtx_lock_spin(&sched_lock);
  979         p->p_singlethread = NULL;
  980         p->p_procscopegrp = NULL;
  981         /*
  982          * If there are other threads they mey now run,
  983          * unless of course there is a blanket 'stop order'
  984          * on the process. The single threader must be allowed
  985          * to continue however as this is a bad place to stop.
  986          */
  987         if ((p->p_numthreads != 1) && (!P_SHOULDSTOP(p))) {
  988                 while ((td = TAILQ_FIRST(&p->p_suspended))) {
  989                         thread_unsuspend_one(td);
  990                 }
  991         }
  992         mtx_unlock_spin(&sched_lock);
  993 }
  994 
  995 /*
  996  * Called before going into an interruptible sleep to see if we have been
  997  * interrupted or requested to exit.
  998  */
  999 int
 1000 thread_sleep_check(struct thread *td)
 1001 {
 1002         struct proc *p;
 1003 
 1004         p = td->td_proc;
 1005         mtx_assert(&sched_lock, MA_OWNED);
 1006         if (p->p_flag & P_HADTHREADS) {
 1007                 if (p->p_singlethread != td) {
 1008                         if (p->p_flag & P_SINGLE_EXIT)
 1009                                 return (EINTR);
 1010                         if (p->p_flag & P_SINGLE_BOUNDARY)
 1011                                 return (ERESTART);
 1012                 }
 1013                 if (td->td_flags & TDF_INTERRUPT)
 1014                         return (td->td_intrval);
 1015         }
 1016         return (0);
 1017 }
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_thread.c

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