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/8.0/sys/kern/kern_timeout.c 187664 2009-01-24 10:22:49Z rwatson $");
   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 SDT_PROVIDER_DEFINE(callout_execute);
   60 SDT_PROBE_DEFINE(callout_execute, kernel, , callout_start);
   61 SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_start, 0,
   62     "struct callout *");
   63 SDT_PROBE_DEFINE(callout_execute, kernel, , callout_end); 
   64 SDT_PROBE_ARGTYPE(callout_execute, kernel, , callout_end, 0,
   65     "struct callout *");
   66 
   67 static int avg_depth;
   68 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
   69     "Average number of items examined per softclock call. Units = 1/1000");
   70 static int avg_gcalls;
   71 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
   72     "Average number of Giant callouts made per softclock call. Units = 1/1000");
   73 static int avg_lockcalls;
   74 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
   75     "Average number of lock callouts made per softclock call. Units = 1/1000");
   76 static int avg_mpcalls;
   77 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
   78     "Average number of MP callouts made per softclock call. Units = 1/1000");
   79 /*
   80  * TODO:
   81  *      allocate more timeout table slots when table overflows.
   82  */
   83 int callwheelsize, callwheelbits, callwheelmask;
   84 
   85 struct callout_cpu {
   86         struct mtx              cc_lock;
   87         struct callout          *cc_callout;
   88         struct callout_tailq    *cc_callwheel;
   89         struct callout_list     cc_callfree;
   90         struct callout          *cc_next;
   91         struct callout          *cc_curr;
   92         void                    *cc_cookie;
   93         int                     cc_softticks;
   94         int                     cc_cancel;
   95         int                     cc_waiting;
   96 };
   97 
   98 #ifdef SMP
   99 struct callout_cpu cc_cpu[MAXCPU];
  100 #define CC_CPU(cpu)     (&cc_cpu[(cpu)])
  101 #define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
  102 #else
  103 struct callout_cpu cc_cpu;
  104 #define CC_CPU(cpu)     &cc_cpu
  105 #define CC_SELF()       &cc_cpu
  106 #endif
  107 #define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
  108 #define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)
  109 
  110 static int timeout_cpu;
  111 
  112 MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
  113 
  114 /**
  115  * Locked by cc_lock:
  116  *   cc_curr         - If a callout is in progress, it is curr_callout.
  117  *                     If curr_callout is non-NULL, threads waiting in
  118  *                     callout_drain() will be woken up as soon as the
  119  *                     relevant callout completes.
  120  *   cc_cancel       - Changing to 1 with both callout_lock and c_lock held
  121  *                     guarantees that the current callout will not run.
  122  *                     The softclock() function sets this to 0 before it
  123  *                     drops callout_lock to acquire c_lock, and it calls
  124  *                     the handler only if curr_cancelled is still 0 after
  125  *                     c_lock is successfully acquired.
  126  *   cc_waiting      - If a thread is waiting in callout_drain(), then
  127  *                     callout_wait is nonzero.  Set only when
  128  *                     curr_callout is non-NULL.
  129  */
  130 
  131 /*
  132  * kern_timeout_callwheel_alloc() - kernel low level callwheel initialization 
  133  *
  134  *      This code is called very early in the kernel initialization sequence,
  135  *      and may be called more then once.
  136  */
  137 caddr_t
  138 kern_timeout_callwheel_alloc(caddr_t v)
  139 {
  140         struct callout_cpu *cc;
  141 
  142         timeout_cpu = PCPU_GET(cpuid);
  143         cc = CC_CPU(timeout_cpu);
  144         /*
  145          * Calculate callout wheel size
  146          */
  147         for (callwheelsize = 1, callwheelbits = 0;
  148              callwheelsize < ncallout;
  149              callwheelsize <<= 1, ++callwheelbits)
  150                 ;
  151         callwheelmask = callwheelsize - 1;
  152 
  153         cc->cc_callout = (struct callout *)v;
  154         v = (caddr_t)(cc->cc_callout + ncallout);
  155         cc->cc_callwheel = (struct callout_tailq *)v;
  156         v = (caddr_t)(cc->cc_callwheel + callwheelsize);
  157         return(v);
  158 }
  159 
  160 static void
  161 callout_cpu_init(struct callout_cpu *cc)
  162 {
  163         struct callout *c;
  164         int i;
  165 
  166         mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
  167         SLIST_INIT(&cc->cc_callfree);
  168         for (i = 0; i < callwheelsize; i++) {
  169                 TAILQ_INIT(&cc->cc_callwheel[i]);
  170         }
  171         if (cc->cc_callout == NULL)
  172                 return;
  173         for (i = 0; i < ncallout; i++) {
  174                 c = &cc->cc_callout[i];
  175                 callout_init(c, 0);
  176                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  177                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  178         }
  179 }
  180 
  181 /*
  182  * kern_timeout_callwheel_init() - initialize previously reserved callwheel
  183  *                                 space.
  184  *
  185  *      This code is called just once, after the space reserved for the
  186  *      callout wheel has been finalized.
  187  */
  188 void
  189 kern_timeout_callwheel_init(void)
  190 {
  191         callout_cpu_init(CC_CPU(timeout_cpu));
  192 }
  193 
  194 /*
  195  * Start standard softclock thread.
  196  */
  197 void    *softclock_ih;
  198 
  199 static void
  200 start_softclock(void *dummy)
  201 {
  202         struct callout_cpu *cc;
  203 #ifdef SMP
  204         int cpu;
  205 #endif
  206 
  207         cc = CC_CPU(timeout_cpu);
  208         if (swi_add(&clk_intr_event, "clock", softclock, cc, SWI_CLOCK,
  209             INTR_MPSAFE, &softclock_ih))
  210                 panic("died while creating standard software ithreads");
  211         cc->cc_cookie = softclock_ih;
  212 #ifdef SMP
  213         for (cpu = 0; cpu <= mp_maxid; cpu++) {
  214                 if (cpu == timeout_cpu)
  215                         continue;
  216                 if (CPU_ABSENT(cpu))
  217                         continue;
  218                 cc = CC_CPU(cpu);
  219                 if (swi_add(NULL, "clock", softclock, cc, SWI_CLOCK,
  220                     INTR_MPSAFE, &cc->cc_cookie))
  221                         panic("died while creating standard software ithreads");
  222                 cc->cc_callout = NULL;  /* Only cpu0 handles timeout(). */
  223                 cc->cc_callwheel = malloc(
  224                     sizeof(struct callout_tailq) * callwheelsize, M_CALLOUT,
  225                     M_WAITOK);
  226                 callout_cpu_init(cc);
  227         }
  228 #endif
  229 }
  230 
  231 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
  232 
  233 void
  234 callout_tick(void)
  235 {
  236         struct callout_cpu *cc;
  237         int need_softclock;
  238         int bucket;
  239 
  240         /*
  241          * Process callouts at a very low cpu priority, so we don't keep the
  242          * relatively high clock interrupt priority any longer than necessary.
  243          */
  244         need_softclock = 0;
  245         cc = CC_SELF();
  246         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  247         for (; (cc->cc_softticks - ticks) < 0; cc->cc_softticks++) {
  248                 bucket = cc->cc_softticks & callwheelmask;
  249                 if (!TAILQ_EMPTY(&cc->cc_callwheel[bucket])) {
  250                         need_softclock = 1;
  251                         break;
  252                 }
  253         }
  254         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  255         /*
  256          * swi_sched acquires the thread lock, so we don't want to call it
  257          * with cc_lock held; incorrect locking order.
  258          */
  259         if (need_softclock)
  260                 swi_sched(cc->cc_cookie, 0);
  261 }
  262 
  263 static struct callout_cpu *
  264 callout_lock(struct callout *c)
  265 {
  266         struct callout_cpu *cc;
  267         int cpu;
  268 
  269         for (;;) {
  270                 cpu = c->c_cpu;
  271                 cc = CC_CPU(cpu);
  272                 CC_LOCK(cc);
  273                 if (cpu == c->c_cpu)
  274                         break;
  275                 CC_UNLOCK(cc);
  276         }
  277         return (cc);
  278 }
  279 
  280 /*
  281  * The callout mechanism is based on the work of Adam M. Costello and 
  282  * George Varghese, published in a technical report entitled "Redesigning
  283  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  284  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  285  * used in this implementation was published by G. Varghese and T. Lauck in
  286  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  287  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  288  * the 11th ACM Annual Symposium on Operating Systems Principles,
  289  * Austin, Texas Nov 1987.
  290  */
  291 
  292 /*
  293  * Software (low priority) clock interrupt.
  294  * Run periodic events from timeout queue.
  295  */
  296 void
  297 softclock(void *arg)
  298 {
  299         struct callout_cpu *cc;
  300         struct callout *c;
  301         struct callout_tailq *bucket;
  302         int curticks;
  303         int steps;      /* #steps since we last allowed interrupts */
  304         int depth;
  305         int mpcalls;
  306         int lockcalls;
  307         int gcalls;
  308 #ifdef DIAGNOSTIC
  309         struct bintime bt1, bt2;
  310         struct timespec ts2;
  311         static uint64_t maxdt = 36893488147419102LL;    /* 2 msec */
  312         static timeout_t *lastfunc;
  313 #endif
  314 
  315 #ifndef MAX_SOFTCLOCK_STEPS
  316 #define MAX_SOFTCLOCK_STEPS 100 /* Maximum allowed value of steps. */
  317 #endif /* MAX_SOFTCLOCK_STEPS */
  318 
  319         mpcalls = 0;
  320         lockcalls = 0;
  321         gcalls = 0;
  322         depth = 0;
  323         steps = 0;
  324         cc = (struct callout_cpu *)arg;
  325         CC_LOCK(cc);
  326         while (cc->cc_softticks != ticks) {
  327                 /*
  328                  * cc_softticks may be modified by hard clock, so cache
  329                  * it while we work on a given bucket.
  330                  */
  331                 curticks = cc->cc_softticks;
  332                 cc->cc_softticks++;
  333                 bucket = &cc->cc_callwheel[curticks & callwheelmask];
  334                 c = TAILQ_FIRST(bucket);
  335                 while (c) {
  336                         depth++;
  337                         if (c->c_time != curticks) {
  338                                 c = TAILQ_NEXT(c, c_links.tqe);
  339                                 ++steps;
  340                                 if (steps >= MAX_SOFTCLOCK_STEPS) {
  341                                         cc->cc_next = c;
  342                                         /* Give interrupts a chance. */
  343                                         CC_UNLOCK(cc);
  344                                         ;       /* nothing */
  345                                         CC_LOCK(cc);
  346                                         c = cc->cc_next;
  347                                         steps = 0;
  348                                 }
  349                         } else {
  350                                 void (*c_func)(void *);
  351                                 void *c_arg;
  352                                 struct lock_class *class;
  353                                 struct lock_object *c_lock;
  354                                 int c_flags, sharedlock;
  355 
  356                                 cc->cc_next = TAILQ_NEXT(c, c_links.tqe);
  357                                 TAILQ_REMOVE(bucket, c, c_links.tqe);
  358                                 class = (c->c_lock != NULL) ?
  359                                     LOCK_CLASS(c->c_lock) : NULL;
  360                                 sharedlock = (c->c_flags & CALLOUT_SHAREDLOCK) ?
  361                                     0 : 1;
  362                                 c_lock = c->c_lock;
  363                                 c_func = c->c_func;
  364                                 c_arg = c->c_arg;
  365                                 c_flags = c->c_flags;
  366                                 if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
  367                                         c->c_flags = CALLOUT_LOCAL_ALLOC;
  368                                 } else {
  369                                         c->c_flags =
  370                                             (c->c_flags & ~CALLOUT_PENDING);
  371                                 }
  372                                 cc->cc_curr = c;
  373                                 cc->cc_cancel = 0;
  374                                 CC_UNLOCK(cc);
  375                                 if (c_lock != NULL) {
  376                                         class->lc_lock(c_lock, sharedlock);
  377                                         /*
  378                                          * The callout may have been cancelled
  379                                          * while we switched locks.
  380                                          */
  381                                         if (cc->cc_cancel) {
  382                                                 class->lc_unlock(c_lock);
  383                                                 goto skip;
  384                                         }
  385                                         /* The callout cannot be stopped now. */
  386                                         cc->cc_cancel = 1;
  387 
  388                                         if (c_lock == &Giant.lock_object) {
  389                                                 gcalls++;
  390                                                 CTR3(KTR_CALLOUT,
  391                                                     "callout %p func %p arg %p",
  392                                                     c, c_func, c_arg);
  393                                         } else {
  394                                                 lockcalls++;
  395                                                 CTR3(KTR_CALLOUT, "callout lock"
  396                                                     " %p func %p arg %p",
  397                                                     c, c_func, c_arg);
  398                                         }
  399                                 } else {
  400                                         mpcalls++;
  401                                         CTR3(KTR_CALLOUT,
  402                                             "callout mpsafe %p func %p arg %p",
  403                                             c, c_func, c_arg);
  404                                 }
  405 #ifdef DIAGNOSTIC
  406                                 binuptime(&bt1);
  407 #endif
  408                                 THREAD_NO_SLEEPING();
  409                                 SDT_PROBE(callout_execute, kernel, ,
  410                                     callout_start, c, 0, 0, 0, 0);
  411                                 c_func(c_arg);
  412                                 SDT_PROBE(callout_execute, kernel, ,
  413                                     callout_end, c, 0, 0, 0, 0);
  414                                 THREAD_SLEEPING_OK();
  415 #ifdef DIAGNOSTIC
  416                                 binuptime(&bt2);
  417                                 bintime_sub(&bt2, &bt1);
  418                                 if (bt2.frac > maxdt) {
  419                                         if (lastfunc != c_func ||
  420                                             bt2.frac > maxdt * 2) {
  421                                                 bintime2timespec(&bt2, &ts2);
  422                                                 printf(
  423                         "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  424                                                     c_func, c_arg,
  425                                                     (intmax_t)ts2.tv_sec,
  426                                                     ts2.tv_nsec);
  427                                         }
  428                                         maxdt = bt2.frac;
  429                                         lastfunc = c_func;
  430                                 }
  431 #endif
  432                                 CTR1(KTR_CALLOUT, "callout %p finished", c);
  433                                 if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
  434                                         class->lc_unlock(c_lock);
  435                         skip:
  436                                 CC_LOCK(cc);
  437                                 /*
  438                                  * If the current callout is locally
  439                                  * allocated (from timeout(9))
  440                                  * then put it on the freelist.
  441                                  *
  442                                  * Note: we need to check the cached
  443                                  * copy of c_flags because if it was not
  444                                  * local, then it's not safe to deref the
  445                                  * callout pointer.
  446                                  */
  447                                 if (c_flags & CALLOUT_LOCAL_ALLOC) {
  448                                         KASSERT(c->c_flags ==
  449                                             CALLOUT_LOCAL_ALLOC,
  450                                             ("corrupted callout"));
  451                                         c->c_func = NULL;
  452                                         SLIST_INSERT_HEAD(&cc->cc_callfree, c,
  453                                             c_links.sle);
  454                                 }
  455                                 cc->cc_curr = NULL;
  456                                 if (cc->cc_waiting) {
  457                                         /*
  458                                          * There is someone waiting
  459                                          * for the callout to complete.
  460                                          */
  461                                         cc->cc_waiting = 0;
  462                                         CC_UNLOCK(cc);
  463                                         wakeup(&cc->cc_waiting);
  464                                         CC_LOCK(cc);
  465                                 }
  466                                 steps = 0;
  467                                 c = cc->cc_next;
  468                         }
  469                 }
  470         }
  471         avg_depth += (depth * 1000 - avg_depth) >> 8;
  472         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  473         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  474         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  475         cc->cc_next = NULL;
  476         CC_UNLOCK(cc);
  477 }
  478 
  479 /*
  480  * timeout --
  481  *      Execute a function after a specified length of time.
  482  *
  483  * untimeout --
  484  *      Cancel previous timeout function call.
  485  *
  486  * callout_handle_init --
  487  *      Initialize a handle so that using it with untimeout is benign.
  488  *
  489  *      See AT&T BCI Driver Reference Manual for specification.  This
  490  *      implementation differs from that one in that although an 
  491  *      identification value is returned from timeout, the original
  492  *      arguments to timeout as well as the identifier are used to
  493  *      identify entries for untimeout.
  494  */
  495 struct callout_handle
  496 timeout(ftn, arg, to_ticks)
  497         timeout_t *ftn;
  498         void *arg;
  499         int to_ticks;
  500 {
  501         struct callout_cpu *cc;
  502         struct callout *new;
  503         struct callout_handle handle;
  504 
  505         cc = CC_CPU(timeout_cpu);
  506         CC_LOCK(cc);
  507         /* Fill in the next free callout structure. */
  508         new = SLIST_FIRST(&cc->cc_callfree);
  509         if (new == NULL)
  510                 /* XXX Attempt to malloc first */
  511                 panic("timeout table full");
  512         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  513         callout_reset(new, to_ticks, ftn, arg);
  514         handle.callout = new;
  515         CC_UNLOCK(cc);
  516 
  517         return (handle);
  518 }
  519 
  520 void
  521 untimeout(ftn, arg, handle)
  522         timeout_t *ftn;
  523         void *arg;
  524         struct callout_handle handle;
  525 {
  526         struct callout_cpu *cc;
  527 
  528         /*
  529          * Check for a handle that was initialized
  530          * by callout_handle_init, but never used
  531          * for a real timeout.
  532          */
  533         if (handle.callout == NULL)
  534                 return;
  535 
  536         cc = callout_lock(handle.callout);
  537         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  538                 callout_stop(handle.callout);
  539         CC_UNLOCK(cc);
  540 }
  541 
  542 void
  543 callout_handle_init(struct callout_handle *handle)
  544 {
  545         handle->callout = NULL;
  546 }
  547 
  548 /*
  549  * New interface; clients allocate their own callout structures.
  550  *
  551  * callout_reset() - establish or change a timeout
  552  * callout_stop() - disestablish a timeout
  553  * callout_init() - initialize a callout structure so that it can
  554  *      safely be passed to callout_reset() and callout_stop()
  555  *
  556  * <sys/callout.h> defines three convenience macros:
  557  *
  558  * callout_active() - returns truth if callout has not been stopped,
  559  *      drained, or deactivated since the last time the callout was
  560  *      reset.
  561  * callout_pending() - returns truth if callout is still waiting for timeout
  562  * callout_deactivate() - marks the callout as having been serviced
  563  */
  564 int
  565 callout_reset_on(struct callout *c, int to_ticks, void (*ftn)(void *),
  566     void *arg, int cpu)
  567 {
  568         struct callout_cpu *cc;
  569         int cancelled = 0;
  570 
  571         /*
  572          * Don't allow migration of pre-allocated callouts lest they
  573          * become unbalanced.
  574          */
  575         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
  576                 cpu = c->c_cpu;
  577 retry:
  578         cc = callout_lock(c);
  579         if (cc->cc_curr == c) {
  580                 /*
  581                  * We're being asked to reschedule a callout which is
  582                  * currently in progress.  If there is a lock then we
  583                  * can cancel the callout if it has not really started.
  584                  */
  585                 if (c->c_lock != NULL && !cc->cc_cancel)
  586                         cancelled = cc->cc_cancel = 1;
  587                 if (cc->cc_waiting) {
  588                         /*
  589                          * Someone has called callout_drain to kill this
  590                          * callout.  Don't reschedule.
  591                          */
  592                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
  593                             cancelled ? "cancelled" : "failed to cancel",
  594                             c, c->c_func, c->c_arg);
  595                         CC_UNLOCK(cc);
  596                         return (cancelled);
  597                 }
  598         }
  599         if (c->c_flags & CALLOUT_PENDING) {
  600                 if (cc->cc_next == c) {
  601                         cc->cc_next = TAILQ_NEXT(c, c_links.tqe);
  602                 }
  603                 TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c,
  604                     c_links.tqe);
  605 
  606                 cancelled = 1;
  607                 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
  608         }
  609         /*
  610          * If the lock must migrate we have to check the state again as
  611          * we can't hold both the new and old locks simultaneously.
  612          */
  613         if (c->c_cpu != cpu) {
  614                 c->c_cpu = cpu;
  615                 CC_UNLOCK(cc);
  616                 goto retry;
  617         }
  618 
  619         if (to_ticks <= 0)
  620                 to_ticks = 1;
  621 
  622         c->c_arg = arg;
  623         c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
  624         c->c_func = ftn;
  625         c->c_time = ticks + to_ticks;
  626         TAILQ_INSERT_TAIL(&cc->cc_callwheel[c->c_time & callwheelmask], 
  627                           c, c_links.tqe);
  628         CTR5(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d",
  629             cancelled ? "re" : "", c, c->c_func, c->c_arg, to_ticks);
  630         CC_UNLOCK(cc);
  631 
  632         return (cancelled);
  633 }
  634 
  635 /*
  636  * Common idioms that can be optimized in the future.
  637  */
  638 int
  639 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
  640 {
  641         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
  642 }
  643 
  644 int
  645 callout_schedule(struct callout *c, int to_ticks)
  646 {
  647         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
  648 }
  649 
  650 int
  651 _callout_stop_safe(c, safe)
  652         struct  callout *c;
  653         int     safe;
  654 {
  655         struct callout_cpu *cc;
  656         struct lock_class *class;
  657         int use_lock, sq_locked;
  658 
  659         /*
  660          * Some old subsystems don't hold Giant while running a callout_stop(),
  661          * so just discard this check for the moment.
  662          */
  663         if (!safe && c->c_lock != NULL) {
  664                 if (c->c_lock == &Giant.lock_object)
  665                         use_lock = mtx_owned(&Giant);
  666                 else {
  667                         use_lock = 1;
  668                         class = LOCK_CLASS(c->c_lock);
  669                         class->lc_assert(c->c_lock, LA_XLOCKED);
  670                 }
  671         } else
  672                 use_lock = 0;
  673 
  674         sq_locked = 0;
  675 again:
  676         cc = callout_lock(c);
  677         /*
  678          * If the callout isn't pending, it's not on the queue, so
  679          * don't attempt to remove it from the queue.  We can try to
  680          * stop it by other means however.
  681          */
  682         if (!(c->c_flags & CALLOUT_PENDING)) {
  683                 c->c_flags &= ~CALLOUT_ACTIVE;
  684 
  685                 /*
  686                  * If it wasn't on the queue and it isn't the current
  687                  * callout, then we can't stop it, so just bail.
  688                  */
  689                 if (cc->cc_curr != c) {
  690                         CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
  691                             c, c->c_func, c->c_arg);
  692                         CC_UNLOCK(cc);
  693                         if (sq_locked)
  694                                 sleepq_release(&cc->cc_waiting);
  695                         return (0);
  696                 }
  697 
  698                 if (safe) {
  699                         /*
  700                          * The current callout is running (or just
  701                          * about to run) and blocking is allowed, so
  702                          * just wait for the current invocation to
  703                          * finish.
  704                          */
  705                         while (cc->cc_curr == c) {
  706 
  707                                 /*
  708                                  * Use direct calls to sleepqueue interface
  709                                  * instead of cv/msleep in order to avoid
  710                                  * a LOR between cc_lock and sleepqueue
  711                                  * chain spinlocks.  This piece of code
  712                                  * emulates a msleep_spin() call actually.
  713                                  *
  714                                  * If we already have the sleepqueue chain
  715                                  * locked, then we can safely block.  If we
  716                                  * don't already have it locked, however,
  717                                  * we have to drop the cc_lock to lock
  718                                  * it.  This opens several races, so we
  719                                  * restart at the beginning once we have
  720                                  * both locks.  If nothing has changed, then
  721                                  * we will end up back here with sq_locked
  722                                  * set.
  723                                  */
  724                                 if (!sq_locked) {
  725                                         CC_UNLOCK(cc);
  726                                         sleepq_lock(&cc->cc_waiting);
  727                                         sq_locked = 1;
  728                                         goto again;
  729                                 }
  730                                 cc->cc_waiting = 1;
  731                                 DROP_GIANT();
  732                                 CC_UNLOCK(cc);
  733                                 sleepq_add(&cc->cc_waiting,
  734                                     &cc->cc_lock.lock_object, "codrain",
  735                                     SLEEPQ_SLEEP, 0);
  736                                 sleepq_wait(&cc->cc_waiting, 0);
  737                                 sq_locked = 0;
  738 
  739                                 /* Reacquire locks previously released. */
  740                                 PICKUP_GIANT();
  741                                 CC_LOCK(cc);
  742                         }
  743                 } else if (use_lock && !cc->cc_cancel) {
  744                         /*
  745                          * The current callout is waiting for its
  746                          * lock which we hold.  Cancel the callout
  747                          * and return.  After our caller drops the
  748                          * lock, the callout will be skipped in
  749                          * softclock().
  750                          */
  751                         cc->cc_cancel = 1;
  752                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
  753                             c, c->c_func, c->c_arg);
  754                         CC_UNLOCK(cc);
  755                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
  756                         return (1);
  757                 }
  758                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
  759                     c, c->c_func, c->c_arg);
  760                 CC_UNLOCK(cc);
  761                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
  762                 return (0);
  763         }
  764         if (sq_locked)
  765                 sleepq_release(&cc->cc_waiting);
  766 
  767         c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
  768 
  769         if (cc->cc_next == c) {
  770                 cc->cc_next = TAILQ_NEXT(c, c_links.tqe);
  771         }
  772         TAILQ_REMOVE(&cc->cc_callwheel[c->c_time & callwheelmask], c,
  773             c_links.tqe);
  774 
  775         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
  776             c, c->c_func, c->c_arg);
  777 
  778         if (c->c_flags & CALLOUT_LOCAL_ALLOC) {
  779                 c->c_func = NULL;
  780                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  781         }
  782         CC_UNLOCK(cc);
  783         return (1);
  784 }
  785 
  786 void
  787 callout_init(c, mpsafe)
  788         struct  callout *c;
  789         int mpsafe;
  790 {
  791         bzero(c, sizeof *c);
  792         if (mpsafe) {
  793                 c->c_lock = NULL;
  794                 c->c_flags = CALLOUT_RETURNUNLOCKED;
  795         } else {
  796                 c->c_lock = &Giant.lock_object;
  797                 c->c_flags = 0;
  798         }
  799         c->c_cpu = timeout_cpu;
  800 }
  801 
  802 void
  803 _callout_init_lock(c, lock, flags)
  804         struct  callout *c;
  805         struct  lock_object *lock;
  806         int flags;
  807 {
  808         bzero(c, sizeof *c);
  809         c->c_lock = lock;
  810         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
  811             ("callout_init_lock: bad flags %d", flags));
  812         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
  813             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
  814         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
  815             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
  816             __func__));
  817         c->c_flags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
  818         c->c_cpu = timeout_cpu;
  819 }
  820 
  821 #ifdef APM_FIXUP_CALLTODO
  822 /* 
  823  * Adjust the kernel calltodo timeout list.  This routine is used after 
  824  * an APM resume to recalculate the calltodo timer list values with the 
  825  * number of hz's we have been sleeping.  The next hardclock() will detect 
  826  * that there are fired timers and run softclock() to execute them.
  827  *
  828  * Please note, I have not done an exhaustive analysis of what code this
  829  * might break.  I am motivated to have my select()'s and alarm()'s that
  830  * have expired during suspend firing upon resume so that the applications
  831  * which set the timer can do the maintanence the timer was for as close
  832  * as possible to the originally intended time.  Testing this code for a 
  833  * week showed that resuming from a suspend resulted in 22 to 25 timers 
  834  * firing, which seemed independant on whether the suspend was 2 hours or
  835  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
  836  */
  837 void
  838 adjust_timeout_calltodo(time_change)
  839     struct timeval *time_change;
  840 {
  841         register struct callout *p;
  842         unsigned long delta_ticks;
  843 
  844         /* 
  845          * How many ticks were we asleep?
  846          * (stolen from tvtohz()).
  847          */
  848 
  849         /* Don't do anything */
  850         if (time_change->tv_sec < 0)
  851                 return;
  852         else if (time_change->tv_sec <= LONG_MAX / 1000000)
  853                 delta_ticks = (time_change->tv_sec * 1000000 +
  854                                time_change->tv_usec + (tick - 1)) / tick + 1;
  855         else if (time_change->tv_sec <= LONG_MAX / hz)
  856                 delta_ticks = time_change->tv_sec * hz +
  857                               (time_change->tv_usec + (tick - 1)) / tick + 1;
  858         else
  859                 delta_ticks = LONG_MAX;
  860 
  861         if (delta_ticks > INT_MAX)
  862                 delta_ticks = INT_MAX;
  863 
  864         /* 
  865          * Now rip through the timer calltodo list looking for timers
  866          * to expire.
  867          */
  868 
  869         /* don't collide with softclock() */
  870         CC_LOCK(cc);
  871         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
  872                 p->c_time -= delta_ticks;
  873 
  874                 /* Break if the timer had more time on it than delta_ticks */
  875                 if (p->c_time > 0)
  876                         break;
  877 
  878                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
  879                 delta_ticks = -p->c_time;
  880         }
  881         CC_UNLOCK(cc);
  882 
  883         return;
  884 }
  885 #endif /* APM_FIXUP_CALLTODO */

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