The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  * (c) UNIX System Laboratories, Inc.
    5  * All or some portions of this file are derived from material licensed
    6  * to the University of California by American Telephone and Telegraph
    7  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
    8  * the permission of UNIX System Laboratories, Inc.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      From: @(#)kern_clock.c  8.5 (Berkeley) 1/21/94
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: releng/9.0/sys/kern/kern_timeout.c 225057 2011-08-21 10:52:50Z attilio $");
   39 
   40 #include "opt_kdtrace.h"
   41 
   42 #include <sys/param.h>
   43 #include <sys/systm.h>
   44 #include <sys/bus.h>
   45 #include <sys/callout.h>
   46 #include <sys/condvar.h>
   47 #include <sys/interrupt.h>
   48 #include <sys/kernel.h>
   49 #include <sys/ktr.h>
   50 #include <sys/lock.h>
   51 #include <sys/malloc.h>
   52 #include <sys/mutex.h>
   53 #include <sys/proc.h>
   54 #include <sys/sdt.h>
   55 #include <sys/sleepqueue.h>
   56 #include <sys/sysctl.h>
   57 #include <sys/smp.h>
   58 
   59 #ifdef SMP
   60 #include <machine/cpu.h>
   61 #endif
   62 
   63 SDT_PROVIDER_DEFINE(callout_execute);
   64 SDT_PROBE_DEFINE(callout_execute, kernel, , callout_start, callout-start);
   65 SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_start, 0,
   66     "struct callout *");
   67 SDT_PROBE_DEFINE(callout_execute, kernel, , callout_end, callout-end); 
   68 SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_end, 0,
   69     "struct callout *");
   70 
   71 static int avg_depth;
   72 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
   73     "Average number of items examined per softclock call. Units = 1/1000");
   74 static int avg_gcalls;
   75 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
   76     "Average number of Giant callouts made per softclock call. Units = 1/1000");
   77 static int avg_lockcalls;
   78 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
   79     "Average number of lock callouts made per softclock call. Units = 1/1000");
   80 static int avg_mpcalls;
   81 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
   82     "Average number of MP callouts made per softclock call. Units = 1/1000");
   83 /*
   84  * TODO:
   85  *      allocate more timeout table slots when table overflows.
   86  */
   87 int callwheelsize, callwheelbits, callwheelmask;
   88 
   89 /*
   90  * The callout cpu migration entity represents informations necessary for
   91  * describing the migrating callout to the new callout cpu.
   92  * The cached informations are very important for deferring migration when
   93  * the migrating callout is already running.
   94  */
   95 struct cc_mig_ent {
   96 #ifdef SMP
   97         void    (*ce_migration_func)(void *);
   98         void    *ce_migration_arg;
   99         int     ce_migration_cpu;
  100         int     ce_migration_ticks;
  101 #endif
  102 };
  103         
  104 /*
  105  * There is one struct callout_cpu per cpu, holding all relevant
  106  * state for the callout processing thread on the individual CPU.
  107  * In particular:
  108  *      cc_ticks is incremented once per tick in callout_cpu().
  109  *      It tracks the global 'ticks' but in a way that the individual
  110  *      threads should not worry about races in the order in which
  111  *      hardclock() and hardclock_cpu() run on the various CPUs.
  112  *      cc_softclock is advanced in callout_cpu() to point to the
  113  *      first entry in cc_callwheel that may need handling. In turn,
  114  *      a softclock() is scheduled so it can serve the various entries i
  115  *      such that cc_softclock <= i <= cc_ticks .
  116  *      XXX maybe cc_softclock and cc_ticks should be volatile ?
  117  *
  118  *      cc_ticks is also used in callout_reset_cpu() to determine
  119  *      when the callout should be served.
  120  */
  121 struct callout_cpu {
  122         struct cc_mig_ent       cc_migrating_entity;
  123         struct mtx              cc_lock;
  124         struct callout          *cc_callout;
  125         struct callout_tailq    *cc_callwheel;
  126         struct callout_list     cc_callfree;
  127         struct callout          *cc_next;
  128         struct callout          *cc_curr;
  129         void                    *cc_cookie;
  130         int                     cc_ticks;
  131         int                     cc_softticks;
  132         int                     cc_cancel;
  133         int                     cc_waiting;
  134         int                     cc_firsttick;
  135 };
  136 
  137 #ifdef SMP
  138 #define cc_migration_func       cc_migrating_entity.ce_migration_func
  139 #define cc_migration_arg        cc_migrating_entity.ce_migration_arg
  140 #define cc_migration_cpu        cc_migrating_entity.ce_migration_cpu
  141 #define cc_migration_ticks      cc_migrating_entity.ce_migration_ticks
  142 
  143 struct callout_cpu cc_cpu[MAXCPU];
  144 #define CPUBLOCK        MAXCPU
  145 #define CC_CPU(cpu)     (&cc_cpu[(cpu)])
  146 #define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
  147 #else
  148 struct callout_cpu cc_cpu;
  149 #define CC_CPU(cpu)     &cc_cpu
  150 #define CC_SELF()       &cc_cpu
  151 #endif
  152 #define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
  153 #define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)
  154 #define CC_LOCK_ASSERT(cc)      mtx_assert(&(cc)->cc_lock, MA_OWNED)
  155 
  156 static int timeout_cpu;
  157 void (*callout_new_inserted)(int cpu, int ticks) = NULL;
  158 
  159 MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
  160 
  161 /**
  162  * Locked by cc_lock:
  163  *   cc_curr         - If a callout is in progress, it is curr_callout.
  164  *                     If curr_callout is non-NULL, threads waiting in
  165  *                     callout_drain() will be woken up as soon as the
  166  *                     relevant callout completes.
  167  *   cc_cancel       - Changing to 1 with both callout_lock and c_lock held
  168  *                     guarantees that the current callout will not run.
  169  *                     The softclock() function sets this to 0 before it
  170  *                     drops callout_lock to acquire c_lock, and it calls
  171  *                     the handler only if curr_cancelled is still 0 after
  172  *                     c_lock is successfully acquired.
  173  *   cc_waiting      - If a thread is waiting in callout_drain(), then
  174  *                     callout_wait is nonzero.  Set only when
  175  *                     curr_callout is non-NULL.
  176  */
  177 
  178 /*
  179  * Resets the migration entity tied to a specific callout cpu.
  180  */
  181 static void
  182 cc_cme_cleanup(struct callout_cpu *cc)
  183 {
  184 
  185 #ifdef SMP
  186         cc->cc_migration_cpu = CPUBLOCK;
  187         cc->cc_migration_ticks = 0;
  188         cc->cc_migration_func = NULL;
  189         cc->cc_migration_arg = NULL;
  190 #endif
  191 }
  192 
  193 /*
  194  * Checks if migration is requested by a specific callout cpu.
  195  */
  196 static int
  197 cc_cme_migrating(struct callout_cpu *cc)
  198 {
  199 
  200 #ifdef SMP
  201         return (cc->cc_migration_cpu != CPUBLOCK);
  202 #else
  203         return (0);
  204 #endif
  205 }
  206 
  207 /*
  208  * kern_timeout_callwheel_alloc() - kernel low level callwheel initialization 
  209  *
  210  *      This code is called very early in the kernel initialization sequence,
  211  *      and may be called more then once.
  212  */
  213 caddr_t
  214 kern_timeout_callwheel_alloc(caddr_t v)
  215 {
  216         struct callout_cpu *cc;
  217 
  218         timeout_cpu = PCPU_GET(cpuid);
  219         cc = CC_CPU(timeout_cpu);
  220         /*
  221          * Calculate callout wheel size
  222          */
  223         for (callwheelsize = 1, callwheelbits = 0;
  224              callwheelsize < ncallout;
  225              callwheelsize <<= 1, ++callwheelbits)
  226                 ;
  227         callwheelmask = callwheelsize - 1;
  228 
  229         cc->cc_callout = (struct callout *)v;
  230         v = (caddr_t)(cc->cc_callout + ncallout);
  231         cc->cc_callwheel = (struct callout_tailq *)v;
  232         v = (caddr_t)(cc->cc_callwheel + callwheelsize);
  233         return(v);
  234 }
  235 
  236 static void
  237 callout_cpu_init(struct callout_cpu *cc)
  238 {
  239         struct callout *c;
  240         int i;
  241 
  242         mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
  243         SLIST_INIT(&cc->cc_callfree);
  244         for (i = 0; i < callwheelsize; i++) {
  245                 TAILQ_INIT(&cc->cc_callwheel[i]);
  246         }
  247         cc_cme_cleanup(cc);
  248         if (cc->cc_callout == NULL)
  249                 return;
  250         for (i = 0; i < ncallout; i++) {
  251                 c = &cc->cc_callout[i];
  252                 callout_init(c, 0);
  253                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  254                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  255         }
  256 }
  257 
  258 #ifdef SMP
  259 /*
  260  * Switches the cpu tied to a specific callout.
  261  * The function expects a locked incoming callout cpu and returns with
  262  * locked outcoming callout cpu.
  263  */
  264 static struct callout_cpu *
  265 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
  266 {
  267         struct callout_cpu *new_cc;
  268 
  269         MPASS(c != NULL && cc != NULL);
  270         CC_LOCK_ASSERT(cc);
  271 
  272         /*
  273          * Avoid interrupts and preemption firing after the callout cpu
  274          * is blocked in order to avoid deadlocks as the new thread
  275          * may be willing to acquire the callout cpu lock.
  276          */
  277         c->c_cpu = CPUBLOCK;
  278         spinlock_enter();
  279         CC_UNLOCK(cc);
  280         new_cc = CC_CPU(new_cpu);
  281         CC_LOCK(new_cc);
  282         spinlock_exit();
  283         c->c_cpu = new_cpu;
  284         return (new_cc);
  285 }
  286 #endif
  287 
  288 /*
  289  * kern_timeout_callwheel_init() - initialize previously reserved callwheel
  290  *                                 space.
  291  *
  292  *      This code is called just once, after the space reserved for the
  293  *      callout wheel has been finalized.
  294  */
  295 void
  296 kern_timeout_callwheel_init(void)
  297 {
  298         callout_cpu_init(CC_CPU(timeout_cpu));
  299 }
  300 
  301 /*
  302  * Start standard softclock thread.
  303  */
  304 static void
  305 start_softclock(void *dummy)
  306 {
  307         struct callout_cpu *cc;
  308 #ifdef SMP
  309         int cpu;
  310 #endif
  311 
  312         cc = CC_CPU(timeout_cpu);
  313         if (swi_add(&clk_intr_event, "clock", softclock, cc, SWI_CLOCK,
  314             INTR_MPSAFE, &cc->cc_cookie))
  315                 panic("died while creating standard software ithreads");
  316 #ifdef SMP
  317         CPU_FOREACH(cpu) {
  318                 if (cpu == timeout_cpu)
  319                         continue;
  320                 cc = CC_CPU(cpu);
  321                 if (swi_add(NULL, "clock", softclock, cc, SWI_CLOCK,
  322                     INTR_MPSAFE, &cc->cc_cookie))
  323                         panic("died while creating standard software ithreads");
  324                 cc->cc_callout = NULL;  /* Only cpu0 handles timeout(). */
  325                 cc->cc_callwheel = malloc(
  326                     sizeof(struct callout_tailq) * callwheelsize, M_CALLOUT,
  327                     M_WAITOK);
  328                 callout_cpu_init(cc);
  329         }
  330 #endif
  331 }
  332 
  333 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
  334 
  335 void
  336 callout_tick(void)
  337 {
  338         struct callout_cpu *cc;
  339         int need_softclock;
  340         int bucket;
  341 
  342         /*
  343          * Process callouts at a very low cpu priority, so we don't keep the
  344          * relatively high clock interrupt priority any longer than necessary.
  345          */
  346         need_softclock = 0;
  347         cc = CC_SELF();
  348         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  349         cc->cc_firsttick = cc->cc_ticks = ticks;
  350         for (; (cc->cc_softticks - cc->cc_ticks) <= 0; cc->cc_softticks++) {
  351                 bucket = cc->cc_softticks & callwheelmask;
  352                 if (!TAILQ_EMPTY(&cc->cc_callwheel[bucket])) {
  353                         need_softclock = 1;
  354                         break;
  355                 }
  356         }
  357         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  358         /*
  359          * swi_sched acquires the thread lock, so we don't want to call it
  360          * with cc_lock held; incorrect locking order.
  361          */
  362         if (need_softclock)
  363                 swi_sched(cc->cc_cookie, 0);
  364 }
  365 
  366 int
  367 callout_tickstofirst(int limit)
  368 {
  369         struct callout_cpu *cc;
  370         struct callout *c;
  371         struct callout_tailq *sc;
  372         int curticks;
  373         int skip = 1;
  374 
  375         cc = CC_SELF();
  376         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  377         curticks = cc->cc_ticks;
  378         while( skip < ncallout && skip < limit ) {
  379                 sc = &cc->cc_callwheel[ (curticks+skip) & callwheelmask ];
  380                 /* search scanning ticks */
  381                 TAILQ_FOREACH( c, sc, c_links.tqe ){
  382                         if (c->c_time - curticks <= ncallout)
  383                                 goto out;
  384                 }
  385                 skip++;
  386         }
  387 out:
  388         cc->cc_firsttick = curticks + skip;
  389         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  390         return (skip);
  391 }
  392 
  393 static struct callout_cpu *
  394 callout_lock(struct callout *c)
  395 {
  396         struct callout_cpu *cc;
  397         int cpu;
  398 
  399         for (;;) {
  400                 cpu = c->c_cpu;
  401 #ifdef SMP
  402                 if (cpu == CPUBLOCK) {
  403                         while (c->c_cpu == CPUBLOCK)
  404                                 cpu_spinwait();
  405                         continue;
  406                 }
  407 #endif
  408                 cc = CC_CPU(cpu);
  409                 CC_LOCK(cc);
  410                 if (cpu == c->c_cpu)
  411                         break;
  412                 CC_UNLOCK(cc);
  413         }
  414         return (cc);
  415 }
  416 
  417 static void
  418 callout_cc_add(struct callout *c, struct callout_cpu *cc, int to_ticks,
  419     void (*func)(void *), void *arg, int cpu)
  420 {
  421 
  422         CC_LOCK_ASSERT(cc);
  423 
  424         if (to_ticks <= 0)
  425                 to_ticks = 1;
  426         c->c_arg = arg;
  427         c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
  428         c->c_func = func;
  429         c->c_time = ticks + to_ticks;
  430         TAILQ_INSERT_TAIL(&cc->cc_callwheel[c->c_time & callwheelmask], 
  431             c, c_links.tqe);
  432         if ((c->c_time - cc->cc_firsttick) < 0 &&
  433             callout_new_inserted != NULL) {
  434                 cc->cc_firsttick = c->c_time;
  435                 (*callout_new_inserted)(cpu,
  436                     to_ticks + (ticks - cc->cc_ticks));
  437         }
  438 }
  439 
  440 /*
  441  * The callout mechanism is based on the work of Adam M. Costello and 
  442  * George Varghese, published in a technical report entitled "Redesigning
  443  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  444  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  445  * used in this implementation was published by G. Varghese and T. Lauck in
  446  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  447  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  448  * the 11th ACM Annual Symposium on Operating Systems Principles,
  449  * Austin, Texas Nov 1987.
  450  */
  451 
  452 /*
  453  * Software (low priority) clock interrupt.
  454  * Run periodic events from timeout queue.
  455  */
  456 void
  457 softclock(void *arg)
  458 {
  459         struct callout_cpu *cc;
  460         struct callout *c;
  461         struct callout_tailq *bucket;
  462         int curticks;
  463         int steps;      /* #steps since we last allowed interrupts */
  464         int depth;
  465         int mpcalls;
  466         int lockcalls;
  467         int gcalls;
  468 #ifdef DIAGNOSTIC
  469         struct bintime bt1, bt2;
  470         struct timespec ts2;
  471         static uint64_t maxdt = 36893488147419102LL;    /* 2 msec */
  472         static timeout_t *lastfunc;
  473 #endif
  474 
  475 #ifndef MAX_SOFTCLOCK_STEPS
  476 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
  477 #endif /* MAX_SOFTCLOCK_STEPS */
  478 
  479         mpcalls = 0;
  480         lockcalls = 0;
  481         gcalls = 0;
  482         depth = 0;
  483         steps = 0;
  484         cc = (struct callout_cpu *)arg;
  485         CC_LOCK(cc);
  486         while (cc->cc_softticks - 1 != cc->cc_ticks) {
  487                 /*
  488                  * cc_softticks may be modified by hard clock, so cache
  489                  * it while we work on a given bucket.
  490                  */
  491                 curticks = cc->cc_softticks;
  492                 cc->cc_softticks++;
  493                 bucket = &cc->cc_callwheel[curticks & callwheelmask];
  494                 c = TAILQ_FIRST(bucket);
  495                 while (c) {
  496                         depth++;
  497                         if (c->c_time != curticks) {
  498                                 c = TAILQ_NEXT(c, c_links.tqe);
  499                                 ++steps;
  500                                 if (steps >= MAX_SOFTCLOCK_STEPS) {
  501                                         cc->cc_next = c;
  502                                         /* Give interrupts a chance. */
  503                                         CC_UNLOCK(cc);
  504                                         ;       /* nothing */
  505                                         CC_LOCK(cc);
  506                                         c = cc->cc_next;
  507                                         steps = 0;
  508                                 }
  509                         } else {
  510                                 void (*c_func)(void *);
  511                                 void *c_arg;
  512                                 struct lock_class *class;
  513                                 struct lock_object *c_lock;
  514                                 int c_flags, sharedlock;
  515 
  516                                 cc->cc_next = TAILQ_NEXT(c, c_links.tqe);
  517                                 TAILQ_REMOVE(bucket, c, c_links.tqe);
  518                                 class = (c->c_lock != NULL) ?
  519                                     LOCK_CLASS(c->c_lock) : NULL;
  520                                 sharedlock = (c->c_flags & CALLOUT_SHAREDLOCK) ?
  521                                     0 : 1;
  522                                 c_lock = c->c_lock;
  523                                 c_func = c->c_func;
  524                                 c_arg = c->c_arg;
  525                                 c_flags = c->c_flags;
  526                                 if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
  527                                         c->c_flags = CALLOUT_LOCAL_ALLOC;
  528                                 } else {
  529                                         c->c_flags =
  530                                             (c->c_flags & ~CALLOUT_PENDING);
  531                                 }
  532                                 cc->cc_curr = c;
  533                                 cc->cc_cancel = 0;
  534                                 CC_UNLOCK(cc);
  535                                 if (c_lock != NULL) {
  536                                         class->lc_lock(c_lock, sharedlock);
  537                                         /*
  538                                          * The callout may have been cancelled
  539                                          * while we switched locks.
  540                                          */
  541                                         if (cc->cc_cancel) {
  542                                                 class->lc_unlock(c_lock);
  543                                                 goto skip;
  544                                         }
  545                                         /* The callout cannot be stopped now. */
  546                                         cc->cc_cancel = 1;
  547 
  548                                         if (c_lock == &Giant.lock_object) {
  549                                                 gcalls++;
  550                                                 CTR3(KTR_CALLOUT,
  551                                                     "callout %p func %p arg %p",
  552                                                     c, c_func, c_arg);
  553                                         } else {
  554                                                 lockcalls++;
  555                                                 CTR3(KTR_CALLOUT, "callout lock"
  556                                                     " %p func %p arg %p",
  557                                                     c, c_func, c_arg);
  558                                         }
  559                                 } else {
  560                                         mpcalls++;
  561                                         CTR3(KTR_CALLOUT,
  562                                             "callout mpsafe %p func %p arg %p",
  563                                             c, c_func, c_arg);
  564                                 }
  565 #ifdef DIAGNOSTIC
  566                                 binuptime(&bt1);
  567 #endif
  568                                 THREAD_NO_SLEEPING();
  569                                 SDT_PROBE(callout_execute, kernel, ,
  570                                     callout_start, c, 0, 0, 0, 0);
  571                                 c_func(c_arg);
  572                                 SDT_PROBE(callout_execute, kernel, ,
  573                                     callout_end, c, 0, 0, 0, 0);
  574                                 THREAD_SLEEPING_OK();
  575 #ifdef DIAGNOSTIC
  576                                 binuptime(&bt2);
  577                                 bintime_sub(&bt2, &bt1);
  578                                 if (bt2.frac > maxdt) {
  579                                         if (lastfunc != c_func ||
  580                                             bt2.frac > maxdt * 2) {
  581                                                 bintime2timespec(&bt2, &ts2);
  582                                                 printf(
  583                         "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  584                                                     c_func, c_arg,
  585                                                     (intmax_t)ts2.tv_sec,
  586                                                     ts2.tv_nsec);
  587                                         }
  588                                         maxdt = bt2.frac;
  589                                         lastfunc = c_func;
  590                                 }
  591 #endif
  592                                 CTR1(KTR_CALLOUT, "callout %p finished", c);
  593                                 if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
  594                                         class->lc_unlock(c_lock);
  595                         skip:
  596                                 CC_LOCK(cc);
  597                                 /*
  598                                  * If the current callout is locally
  599                                  * allocated (from timeout(9))
  600                                  * then put it on the freelist.
  601                                  *
  602                                  * Note: we need to check the cached
  603                                  * copy of c_flags because if it was not
  604                                  * local, then it's not safe to deref the
  605                                  * callout pointer.
  606                                  */
  607                                 if (c_flags & CALLOUT_LOCAL_ALLOC) {
  608                                         KASSERT(c->c_flags ==
  609                                             CALLOUT_LOCAL_ALLOC,
  610                                             ("corrupted callout"));
  611                                         c->c_func = NULL;
  612                                         SLIST_INSERT_HEAD(&cc->cc_callfree, c,
  613                                             c_links.sle);
  614                                 }
  615                                 cc->cc_curr = NULL;
  616                                 if (cc->cc_waiting) {
  617 
  618                                         /*
  619                                          * There is someone waiting for the
  620                                          * callout to complete.
  621                                          * If the callout was scheduled for
  622                                          * migration just cancel it.
  623                                          */
  624                                         if (cc_cme_migrating(cc))
  625                                                 cc_cme_cleanup(cc);
  626                                         cc->cc_waiting = 0;
  627                                         CC_UNLOCK(cc);
  628                                         wakeup(&cc->cc_waiting);
  629                                         CC_LOCK(cc);
  630                                 } else if (cc_cme_migrating(cc)) {
  631 #ifdef SMP
  632                                         struct callout_cpu *new_cc;
  633                                         void (*new_func)(void *);
  634                                         void *new_arg;
  635                                         int new_cpu, new_ticks;
  636 
  637                                         /*
  638                                          * If the callout was scheduled for
  639                                          * migration just perform it now.
  640                                          */
  641                                         new_cpu = cc->cc_migration_cpu;
  642                                         new_ticks = cc->cc_migration_ticks;
  643                                         new_func = cc->cc_migration_func;
  644                                         new_arg = cc->cc_migration_arg;
  645                                         cc_cme_cleanup(cc);
  646 
  647                                         /*
  648                                          * It should be assert here that the
  649                                          * callout is not destroyed but that
  650                                          * is not easy.
  651                                          */
  652                                         new_cc = callout_cpu_switch(c, cc,
  653                                             new_cpu);
  654                                         callout_cc_add(c, new_cc, new_ticks,
  655                                             new_func, new_arg, new_cpu);
  656                                         CC_UNLOCK(new_cc);
  657                                         CC_LOCK(cc);
  658 #else
  659                                         panic("migration should not happen");
  660 #endif
  661                                 }
  662                                 steps = 0;
  663                                 c = cc->cc_next;
  664                         }
  665                 }
  666         }
  667         avg_depth += (depth * 1000 - avg_depth) >> 8;
  668         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  669         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  670         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  671         cc->cc_next = NULL;
  672         CC_UNLOCK(cc);
  673 }
  674 
  675 /*
  676  * timeout --
  677  *      Execute a function after a specified length of time.
  678  *
  679  * untimeout --
  680  *      Cancel previous timeout function call.
  681  *
  682  * callout_handle_init --
  683  *      Initialize a handle so that using it with untimeout is benign.
  684  *
  685  *      See AT&T BCI Driver Reference Manual for specification.  This
  686  *      implementation differs from that one in that although an 
  687  *      identification value is returned from timeout, the original
  688  *      arguments to timeout as well as the identifier are used to
  689  *      identify entries for untimeout.
  690  */
  691 struct callout_handle
  692 timeout(ftn, arg, to_ticks)
  693         timeout_t *ftn;
  694         void *arg;
  695         int to_ticks;
  696 {
  697         struct callout_cpu *cc;
  698         struct callout *new;
  699         struct callout_handle handle;
  700 
  701         cc = CC_CPU(timeout_cpu);
  702         CC_LOCK(cc);
  703         /* Fill in the next free callout structure. */
  704         new = SLIST_FIRST(&cc->cc_callfree);
  705         if (new == NULL)
  706                 /* XXX Attempt to malloc first */
  707                 panic("timeout table full");
  708         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  709         callout_reset(new, to_ticks, ftn, arg);
  710         handle.callout = new;
  711         CC_UNLOCK(cc);
  712 
  713         return (handle);
  714 }
  715 
  716 void
  717 untimeout(ftn, arg, handle)
  718         timeout_t *ftn;
  719         void *arg;
  720         struct callout_handle handle;
  721 {
  722         struct callout_cpu *cc;
  723 
  724         /*
  725          * Check for a handle that was initialized
  726          * by callout_handle_init, but never used
  727          * for a real timeout.
  728          */
  729         if (handle.callout == NULL)
  730                 return;
  731 
  732         cc = callout_lock(handle.callout);
  733         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  734                 callout_stop(handle.callout);
  735         CC_UNLOCK(cc);
  736 }
  737 
  738 void
  739 callout_handle_init(struct callout_handle *handle)
  740 {
  741         handle->callout = NULL;
  742 }
  743 
  744 /*
  745  * New interface; clients allocate their own callout structures.
  746  *
  747  * callout_reset() - establish or change a timeout
  748  * callout_stop() - disestablish a timeout
  749  * callout_init() - initialize a callout structure so that it can
  750  *      safely be passed to callout_reset() and callout_stop()
  751  *
  752  * <sys/callout.h> defines three convenience macros:
  753  *
  754  * callout_active() - returns truth if callout has not been stopped,
  755  *      drained, or deactivated since the last time the callout was
  756  *      reset.
  757  * callout_pending() - returns truth if callout is still waiting for timeout
  758  * callout_deactivate() - marks the callout as having been serviced
  759  */
  760 int
  761 callout_reset_on(struct callout *c, int to_ticks, void (*ftn)(void *),
  762     void *arg, int cpu)
  763 {
  764         struct callout_cpu *cc;
  765         int cancelled = 0;
  766 
  767         /*
  768          * Don't allow migration of pre-allocated callouts lest they
  769          * become unbalanced.
  770          */
  771         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
  772                 cpu = c->c_cpu;
  773         cc = callout_lock(c);
  774         if (cc->cc_curr == c) {
  775                 /*
  776                  * We're being asked to reschedule a callout which is
  777                  * currently in progress.  If there is a lock then we
  778                  * can cancel the callout if it has not really started.
  779                  */
  780                 if (c->c_lock != NULL && !cc->cc_cancel)
  781                         cancelled = cc->cc_cancel = 1;
  782                 if (cc->cc_waiting) {
  783                         /*
  784                          * Someone has called callout_drain to kill this
  785                          * callout.  Don't reschedule.
  786                          */
  787                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
  788                             cancelled ? "cancelled" : "failed to cancel",
  789                             c, c->c_func, c->c_arg);
  790                         CC_UNLOCK(cc);
  791                         return (cancelled);
  792                 }
  793         }
  794         if (c->c_flags & CALLOUT_PENDING) {
  795                 if (cc->cc_next == c) {
  796                         cc->cc_next = TAILQ_NEXT(c, c_links.tqe);
  797                 }
  798                 TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c,
  799                     c_links.tqe);
  800 
  801                 cancelled = 1;
  802                 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
  803         }
  804 
  805 #ifdef SMP
  806         /*
  807          * If the callout must migrate try to perform it immediately.
  808          * If the callout is currently running, just defer the migration
  809          * to a more appropriate moment.
  810          */
  811         if (c->c_cpu != cpu) {
  812                 if (cc->cc_curr == c) {
  813                         cc->cc_migration_cpu = cpu;
  814                         cc->cc_migration_ticks = to_ticks;
  815                         cc->cc_migration_func = ftn;
  816                         cc->cc_migration_arg = arg;
  817                         CTR5(KTR_CALLOUT,
  818                     "migration of %p func %p arg %p in %d to %u deferred",
  819                             c, c->c_func, c->c_arg, to_ticks, cpu);
  820                         CC_UNLOCK(cc);
  821                         return (cancelled);
  822                 }
  823                 cc = callout_cpu_switch(c, cc, cpu);
  824         }
  825 #endif
  826 
  827         callout_cc_add(c, cc, to_ticks, ftn, arg, cpu);
  828         CTR5(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d",
  829             cancelled ? "re" : "", c, c->c_func, c->c_arg, to_ticks);
  830         CC_UNLOCK(cc);
  831 
  832         return (cancelled);
  833 }
  834 
  835 /*
  836  * Common idioms that can be optimized in the future.
  837  */
  838 int
  839 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
  840 {
  841         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
  842 }
  843 
  844 int
  845 callout_schedule(struct callout *c, int to_ticks)
  846 {
  847         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
  848 }
  849 
  850 int
  851 _callout_stop_safe(c, safe)
  852         struct  callout *c;
  853         int     safe;
  854 {
  855         struct callout_cpu *cc, *old_cc;
  856         struct lock_class *class;
  857         int use_lock, sq_locked;
  858 
  859         /*
  860          * Some old subsystems don't hold Giant while running a callout_stop(),
  861          * so just discard this check for the moment.
  862          */
  863         if (!safe && c->c_lock != NULL) {
  864                 if (c->c_lock == &Giant.lock_object)
  865                         use_lock = mtx_owned(&Giant);
  866                 else {
  867                         use_lock = 1;
  868                         class = LOCK_CLASS(c->c_lock);
  869                         class->lc_assert(c->c_lock, LA_XLOCKED);
  870                 }
  871         } else
  872                 use_lock = 0;
  873 
  874         sq_locked = 0;
  875         old_cc = NULL;
  876 again:
  877         cc = callout_lock(c);
  878 
  879         /*
  880          * If the callout was migrating while the callout cpu lock was
  881          * dropped,  just drop the sleepqueue lock and check the states
  882          * again.
  883          */
  884         if (sq_locked != 0 && cc != old_cc) {
  885 #ifdef SMP
  886                 CC_UNLOCK(cc);
  887                 sleepq_release(&old_cc->cc_waiting);
  888                 sq_locked = 0;
  889                 old_cc = NULL;
  890                 goto again;
  891 #else
  892                 panic("migration should not happen");
  893 #endif
  894         }
  895 
  896         /*
  897          * If the callout isn't pending, it's not on the queue, so
  898          * don't attempt to remove it from the queue.  We can try to
  899          * stop it by other means however.
  900          */
  901         if (!(c->c_flags & CALLOUT_PENDING)) {
  902                 c->c_flags &= ~CALLOUT_ACTIVE;
  903 
  904                 /*
  905                  * If it wasn't on the queue and it isn't the current
  906                  * callout, then we can't stop it, so just bail.
  907                  */
  908                 if (cc->cc_curr != c) {
  909                         CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
  910                             c, c->c_func, c->c_arg);
  911                         CC_UNLOCK(cc);
  912                         if (sq_locked)
  913                                 sleepq_release(&cc->cc_waiting);
  914                         return (0);
  915                 }
  916 
  917                 if (safe) {
  918                         /*
  919                          * The current callout is running (or just
  920                          * about to run) and blocking is allowed, so
  921                          * just wait for the current invocation to
  922                          * finish.
  923                          */
  924                         while (cc->cc_curr == c) {
  925 
  926                                 /*
  927                                  * Use direct calls to sleepqueue interface
  928                                  * instead of cv/msleep in order to avoid
  929                                  * a LOR between cc_lock and sleepqueue
  930                                  * chain spinlocks.  This piece of code
  931                                  * emulates a msleep_spin() call actually.
  932                                  *
  933                                  * If we already have the sleepqueue chain
  934                                  * locked, then we can safely block.  If we
  935                                  * don't already have it locked, however,
  936                                  * we have to drop the cc_lock to lock
  937                                  * it.  This opens several races, so we
  938                                  * restart at the beginning once we have
  939                                  * both locks.  If nothing has changed, then
  940                                  * we will end up back here with sq_locked
  941                                  * set.
  942                                  */
  943                                 if (!sq_locked) {
  944                                         CC_UNLOCK(cc);
  945                                         sleepq_lock(&cc->cc_waiting);
  946                                         sq_locked = 1;
  947                                         old_cc = cc;
  948                                         goto again;
  949                                 }
  950 
  951                                 /*
  952                                  * Migration could be cancelled here, but
  953                                  * as long as it is still not sure when it
  954                                  * will be packed up, just let softclock()
  955                                  * take care of it.
  956                                  */
  957                                 cc->cc_waiting = 1;
  958                                 DROP_GIANT();
  959                                 CC_UNLOCK(cc);
  960                                 sleepq_add(&cc->cc_waiting,
  961                                     &cc->cc_lock.lock_object, "codrain",
  962                                     SLEEPQ_SLEEP, 0);
  963                                 sleepq_wait(&cc->cc_waiting, 0);
  964                                 sq_locked = 0;
  965                                 old_cc = NULL;
  966 
  967                                 /* Reacquire locks previously released. */
  968                                 PICKUP_GIANT();
  969                                 CC_LOCK(cc);
  970                         }
  971                 } else if (use_lock && !cc->cc_cancel) {
  972                         /*
  973                          * The current callout is waiting for its
  974                          * lock which we hold.  Cancel the callout
  975                          * and return.  After our caller drops the
  976                          * lock, the callout will be skipped in
  977                          * softclock().
  978                          */
  979                         cc->cc_cancel = 1;
  980                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
  981                             c, c->c_func, c->c_arg);
  982                         KASSERT(!cc_cme_migrating(cc),
  983                             ("callout wrongly scheduled for migration"));
  984                         CC_UNLOCK(cc);
  985                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
  986                         return (1);
  987                 }
  988                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
  989                     c, c->c_func, c->c_arg);
  990                 CC_UNLOCK(cc);
  991                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
  992                 return (0);
  993         }
  994         if (sq_locked)
  995                 sleepq_release(&cc->cc_waiting);
  996 
  997         c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
  998 
  999         if (cc->cc_next == c) {
 1000                 cc->cc_next = TAILQ_NEXT(c, c_links.tqe);
 1001         }
 1002         TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c,
 1003             c_links.tqe);
 1004 
 1005         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1006             c, c->c_func, c->c_arg);
 1007 
 1008         if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
 1009                 c->c_func = NULL;
 1010                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
 1011         }
 1012         CC_UNLOCK(cc);
 1013         return (1);
 1014 }
 1015 
 1016 void
 1017 callout_init(c, mpsafe)
 1018         struct  callout *c;
 1019         int mpsafe;
 1020 {
 1021         bzero(c, sizeof *c);
 1022         if (mpsafe) {
 1023                 c->c_lock = NULL;
 1024                 c->c_flags = CALLOUT_RETURNUNLOCKED;
 1025         } else {
 1026                 c->c_lock = &Giant.lock_object;
 1027                 c->c_flags = 0;
 1028         }
 1029         c->c_cpu = timeout_cpu;
 1030 }
 1031 
 1032 void
 1033 _callout_init_lock(c, lock, flags)
 1034         struct  callout *c;
 1035         struct  lock_object *lock;
 1036         int flags;
 1037 {
 1038         bzero(c, sizeof *c);
 1039         c->c_lock = lock;
 1040         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
 1041             ("callout_init_lock: bad flags %d", flags));
 1042         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
 1043             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
 1044         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
 1045             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
 1046             __func__));
 1047         c->c_flags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
 1048         c->c_cpu = timeout_cpu;
 1049 }
 1050 
 1051 #ifdef APM_FIXUP_CALLTODO
 1052 /* 
 1053  * Adjust the kernel calltodo timeout list.  This routine is used after 
 1054  * an APM resume to recalculate the calltodo timer list values with the 
 1055  * number of hz's we have been sleeping.  The next hardclock() will detect 
 1056  * that there are fired timers and run softclock() to execute them.
 1057  *
 1058  * Please note, I have not done an exhaustive analysis of what code this
 1059  * might break.  I am motivated to have my select()'s and alarm()'s that
 1060  * have expired during suspend firing upon resume so that the applications
 1061  * which set the timer can do the maintanence the timer was for as close
 1062  * as possible to the originally intended time.  Testing this code for a 
 1063  * week showed that resuming from a suspend resulted in 22 to 25 timers 
 1064  * firing, which seemed independant on whether the suspend was 2 hours or
 1065  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 1066  */
 1067 void
 1068 adjust_timeout_calltodo(time_change)
 1069     struct timeval *time_change;
 1070 {
 1071         register struct callout *p;
 1072         unsigned long delta_ticks;
 1073 
 1074         /* 
 1075          * How many ticks were we asleep?
 1076          * (stolen from tvtohz()).
 1077          */
 1078 
 1079         /* Don't do anything */
 1080         if (time_change->tv_sec < 0)
 1081                 return;
 1082         else if (time_change->tv_sec <= LONG_MAX / 1000000)
 1083                 delta_ticks = (time_change->tv_sec * 1000000 +
 1084                                time_change->tv_usec + (tick - 1)) / tick + 1;
 1085         else if (time_change->tv_sec <= LONG_MAX / hz)
 1086                 delta_ticks = time_change->tv_sec * hz +
 1087                               (time_change->tv_usec + (tick - 1)) / tick + 1;
 1088         else
 1089                 delta_ticks = LONG_MAX;
 1090 
 1091         if (delta_ticks > INT_MAX)
 1092                 delta_ticks = INT_MAX;
 1093 
 1094         /* 
 1095          * Now rip through the timer calltodo list looking for timers
 1096          * to expire.
 1097          */
 1098 
 1099         /* don't collide with softclock() */
 1100         CC_LOCK(cc);
 1101         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 1102                 p->c_time -= delta_ticks;
 1103 
 1104                 /* Break if the timer had more time on it than delta_ticks */
 1105                 if (p->c_time > 0)
 1106                         break;
 1107 
 1108                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
 1109                 delta_ticks = -p->c_time;
 1110         }
 1111         CC_UNLOCK(cc);
 1112 
 1113         return;
 1114 }
 1115 #endif /* APM_FIXUP_CALLTODO */

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