The Design and Implementation of the FreeBSD Operating System, Second Edition
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sys/kern/kern_timeout.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 1982, 1986, 1991, 1993
    5  *      The Regents of the University of California.  All rights reserved.
    6  * (c) UNIX System Laboratories, Inc.
    7  * All or some portions of this file are derived from material licensed
    8  * to the University of California by American Telephone and Telegraph
    9  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
   10  * the permission of UNIX System Laboratories, Inc.
   11  *
   12  * Redistribution and use in source and binary forms, with or without
   13  * modification, are permitted provided that the following conditions
   14  * are met:
   15  * 1. Redistributions of source code must retain the above copyright
   16  *    notice, this list of conditions and the following disclaimer.
   17  * 2. Redistributions in binary form must reproduce the above copyright
   18  *    notice, this list of conditions and the following disclaimer in the
   19  *    documentation and/or other materials provided with the distribution.
   20  * 3. Neither the name of the University nor the names of its contributors
   21  *    may be used to endorse or promote products derived from this software
   22  *    without specific prior written permission.
   23  *
   24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   34  * SUCH DAMAGE.
   35  *
   36  *      From: @(#)kern_clock.c  8.5 (Berkeley) 1/21/94
   37  */
   38 
   39 #include <sys/cdefs.h>
   40 __FBSDID("$FreeBSD: head/sys/kern/kern_timeout.c 326218 2017-11-25 23:41:05Z nwhitehorn $");
   41 
   42 #include "opt_callout_profiling.h"
   43 #include "opt_ddb.h"
   44 #if defined(__arm__)
   45 #include "opt_timer.h"
   46 #endif
   47 #include "opt_rss.h"
   48 
   49 #include <sys/param.h>
   50 #include <sys/systm.h>
   51 #include <sys/bus.h>
   52 #include <sys/callout.h>
   53 #include <sys/file.h>
   54 #include <sys/interrupt.h>
   55 #include <sys/kernel.h>
   56 #include <sys/ktr.h>
   57 #include <sys/lock.h>
   58 #include <sys/malloc.h>
   59 #include <sys/mutex.h>
   60 #include <sys/proc.h>
   61 #include <sys/sdt.h>
   62 #include <sys/sleepqueue.h>
   63 #include <sys/sysctl.h>
   64 #include <sys/smp.h>
   65 
   66 #ifdef DDB
   67 #include <ddb/ddb.h>
   68 #include <machine/_inttypes.h>
   69 #endif
   70 
   71 #ifdef SMP
   72 #include <machine/cpu.h>
   73 #endif
   74 
   75 #ifndef NO_EVENTTIMERS
   76 DPCPU_DECLARE(sbintime_t, hardclocktime);
   77 #endif
   78 
   79 SDT_PROVIDER_DEFINE(callout_execute);
   80 SDT_PROBE_DEFINE1(callout_execute, , , callout__start, "struct callout *");
   81 SDT_PROBE_DEFINE1(callout_execute, , , callout__end, "struct callout *");
   82 
   83 #ifdef CALLOUT_PROFILING
   84 static int avg_depth;
   85 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
   86     "Average number of items examined per softclock call. Units = 1/1000");
   87 static int avg_gcalls;
   88 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
   89     "Average number of Giant callouts made per softclock call. Units = 1/1000");
   90 static int avg_lockcalls;
   91 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
   92     "Average number of lock callouts made per softclock call. Units = 1/1000");
   93 static int avg_mpcalls;
   94 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
   95     "Average number of MP callouts made per softclock call. Units = 1/1000");
   96 static int avg_depth_dir;
   97 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth_dir, CTLFLAG_RD, &avg_depth_dir, 0,
   98     "Average number of direct callouts examined per callout_process call. "
   99     "Units = 1/1000");
  100 static int avg_lockcalls_dir;
  101 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls_dir, CTLFLAG_RD,
  102     &avg_lockcalls_dir, 0, "Average number of lock direct callouts made per "
  103     "callout_process call. Units = 1/1000");
  104 static int avg_mpcalls_dir;
  105 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls_dir, CTLFLAG_RD, &avg_mpcalls_dir,
  106     0, "Average number of MP direct callouts made per callout_process call. "
  107     "Units = 1/1000");
  108 #endif
  109 
  110 static int ncallout;
  111 SYSCTL_INT(_kern, OID_AUTO, ncallout, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &ncallout, 0,
  112     "Number of entries in callwheel and size of timeout() preallocation");
  113 
  114 #ifdef  RSS
  115 static int pin_default_swi = 1;
  116 static int pin_pcpu_swi = 1;
  117 #else
  118 static int pin_default_swi = 0;
  119 static int pin_pcpu_swi = 0;
  120 #endif
  121 
  122 SYSCTL_INT(_kern, OID_AUTO, pin_default_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_default_swi,
  123     0, "Pin the default (non-per-cpu) swi (shared with PCPU 0 swi)");
  124 SYSCTL_INT(_kern, OID_AUTO, pin_pcpu_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_pcpu_swi,
  125     0, "Pin the per-CPU swis (except PCPU 0, which is also default");
  126 
  127 /*
  128  * TODO:
  129  *      allocate more timeout table slots when table overflows.
  130  */
  131 u_int callwheelsize, callwheelmask;
  132 
  133 /*
  134  * The callout cpu exec entities represent informations necessary for
  135  * describing the state of callouts currently running on the CPU and the ones
  136  * necessary for migrating callouts to the new callout cpu. In particular,
  137  * the first entry of the array cc_exec_entity holds informations for callout
  138  * running in SWI thread context, while the second one holds informations
  139  * for callout running directly from hardware interrupt context.
  140  * The cached informations are very important for deferring migration when
  141  * the migrating callout is already running.
  142  */
  143 struct cc_exec {
  144         struct callout          *cc_curr;
  145         void                    (*cc_drain)(void *);
  146 #ifdef SMP
  147         void                    (*ce_migration_func)(void *);
  148         void                    *ce_migration_arg;
  149         int                     ce_migration_cpu;
  150         sbintime_t              ce_migration_time;
  151         sbintime_t              ce_migration_prec;
  152 #endif
  153         bool                    cc_cancel;
  154         bool                    cc_waiting;
  155 };
  156 
  157 /*
  158  * There is one struct callout_cpu per cpu, holding all relevant
  159  * state for the callout processing thread on the individual CPU.
  160  */
  161 struct callout_cpu {
  162         struct mtx_padalign     cc_lock;
  163         struct cc_exec          cc_exec_entity[2];
  164         struct callout          *cc_next;
  165         struct callout          *cc_callout;
  166         struct callout_list     *cc_callwheel;
  167         struct callout_tailq    cc_expireq;
  168         struct callout_slist    cc_callfree;
  169         sbintime_t              cc_firstevent;
  170         sbintime_t              cc_lastscan;
  171         void                    *cc_cookie;
  172         u_int                   cc_bucket;
  173         u_int                   cc_inited;
  174         char                    cc_ktr_event_name[20];
  175 };
  176 
  177 #define callout_migrating(c)    ((c)->c_iflags & CALLOUT_DFRMIGRATION)
  178 
  179 #define cc_exec_curr(cc, dir)           cc->cc_exec_entity[dir].cc_curr
  180 #define cc_exec_drain(cc, dir)          cc->cc_exec_entity[dir].cc_drain
  181 #define cc_exec_next(cc)                cc->cc_next
  182 #define cc_exec_cancel(cc, dir)         cc->cc_exec_entity[dir].cc_cancel
  183 #define cc_exec_waiting(cc, dir)        cc->cc_exec_entity[dir].cc_waiting
  184 #ifdef SMP
  185 #define cc_migration_func(cc, dir)      cc->cc_exec_entity[dir].ce_migration_func
  186 #define cc_migration_arg(cc, dir)       cc->cc_exec_entity[dir].ce_migration_arg
  187 #define cc_migration_cpu(cc, dir)       cc->cc_exec_entity[dir].ce_migration_cpu
  188 #define cc_migration_time(cc, dir)      cc->cc_exec_entity[dir].ce_migration_time
  189 #define cc_migration_prec(cc, dir)      cc->cc_exec_entity[dir].ce_migration_prec
  190 
  191 struct callout_cpu cc_cpu[MAXCPU];
  192 #define CPUBLOCK        MAXCPU
  193 #define CC_CPU(cpu)     (&cc_cpu[(cpu)])
  194 #define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
  195 #else
  196 struct callout_cpu cc_cpu;
  197 #define CC_CPU(cpu)     &cc_cpu
  198 #define CC_SELF()       &cc_cpu
  199 #endif
  200 #define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
  201 #define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)
  202 #define CC_LOCK_ASSERT(cc)      mtx_assert(&(cc)->cc_lock, MA_OWNED)
  203 
  204 static int timeout_cpu;
  205 
  206 static void     callout_cpu_init(struct callout_cpu *cc, int cpu);
  207 static void     softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  208 #ifdef CALLOUT_PROFILING
  209                     int *mpcalls, int *lockcalls, int *gcalls,
  210 #endif
  211                     int direct);
  212 
  213 static MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
  214 
  215 /**
  216  * Locked by cc_lock:
  217  *   cc_curr         - If a callout is in progress, it is cc_curr.
  218  *                     If cc_curr is non-NULL, threads waiting in
  219  *                     callout_drain() will be woken up as soon as the
  220  *                     relevant callout completes.
  221  *   cc_cancel       - Changing to 1 with both callout_lock and cc_lock held
  222  *                     guarantees that the current callout will not run.
  223  *                     The softclock() function sets this to 0 before it
  224  *                     drops callout_lock to acquire c_lock, and it calls
  225  *                     the handler only if curr_cancelled is still 0 after
  226  *                     cc_lock is successfully acquired.
  227  *   cc_waiting      - If a thread is waiting in callout_drain(), then
  228  *                     callout_wait is nonzero.  Set only when
  229  *                     cc_curr is non-NULL.
  230  */
  231 
  232 /*
  233  * Resets the execution entity tied to a specific callout cpu.
  234  */
  235 static void
  236 cc_cce_cleanup(struct callout_cpu *cc, int direct)
  237 {
  238 
  239         cc_exec_curr(cc, direct) = NULL;
  240         cc_exec_cancel(cc, direct) = false;
  241         cc_exec_waiting(cc, direct) = false;
  242 #ifdef SMP
  243         cc_migration_cpu(cc, direct) = CPUBLOCK;
  244         cc_migration_time(cc, direct) = 0;
  245         cc_migration_prec(cc, direct) = 0;
  246         cc_migration_func(cc, direct) = NULL;
  247         cc_migration_arg(cc, direct) = NULL;
  248 #endif
  249 }
  250 
  251 /*
  252  * Checks if migration is requested by a specific callout cpu.
  253  */
  254 static int
  255 cc_cce_migrating(struct callout_cpu *cc, int direct)
  256 {
  257 
  258 #ifdef SMP
  259         return (cc_migration_cpu(cc, direct) != CPUBLOCK);
  260 #else
  261         return (0);
  262 #endif
  263 }
  264 
  265 /*
  266  * Kernel low level callwheel initialization
  267  * called on the BSP during kernel startup.
  268  */
  269 static void
  270 callout_callwheel_init(void *dummy)
  271 {
  272         struct callout_cpu *cc;
  273 
  274         /*
  275          * Calculate the size of the callout wheel and the preallocated
  276          * timeout() structures.
  277          * XXX: Clip callout to result of previous function of maxusers
  278          * maximum 384.  This is still huge, but acceptable.
  279          */
  280         memset(CC_CPU(curcpu), 0, sizeof(cc_cpu));
  281         ncallout = imin(16 + maxproc + maxfiles, 18508);
  282         TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
  283 
  284         /*
  285          * Calculate callout wheel size, should be next power of two higher
  286          * than 'ncallout'.
  287          */
  288         callwheelsize = 1 << fls(ncallout);
  289         callwheelmask = callwheelsize - 1;
  290 
  291         /*
  292          * Fetch whether we're pinning the swi's or not.
  293          */
  294         TUNABLE_INT_FETCH("kern.pin_default_swi", &pin_default_swi);
  295         TUNABLE_INT_FETCH("kern.pin_pcpu_swi", &pin_pcpu_swi);
  296 
  297         /*
  298          * Only BSP handles timeout(9) and receives a preallocation.
  299          *
  300          * XXX: Once all timeout(9) consumers are converted this can
  301          * be removed.
  302          */
  303         timeout_cpu = PCPU_GET(cpuid);
  304         cc = CC_CPU(timeout_cpu);
  305         cc->cc_callout = malloc(ncallout * sizeof(struct callout),
  306             M_CALLOUT, M_WAITOK);
  307         callout_cpu_init(cc, timeout_cpu);
  308 }
  309 SYSINIT(callwheel_init, SI_SUB_CPU, SI_ORDER_ANY, callout_callwheel_init, NULL);
  310 
  311 /*
  312  * Initialize the per-cpu callout structures.
  313  */
  314 static void
  315 callout_cpu_init(struct callout_cpu *cc, int cpu)
  316 {
  317         struct callout *c;
  318         int i;
  319 
  320         mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
  321         SLIST_INIT(&cc->cc_callfree);
  322         cc->cc_inited = 1;
  323         cc->cc_callwheel = malloc(sizeof(struct callout_list) * callwheelsize,
  324             M_CALLOUT, M_WAITOK);
  325         for (i = 0; i < callwheelsize; i++)
  326                 LIST_INIT(&cc->cc_callwheel[i]);
  327         TAILQ_INIT(&cc->cc_expireq);
  328         cc->cc_firstevent = SBT_MAX;
  329         for (i = 0; i < 2; i++)
  330                 cc_cce_cleanup(cc, i);
  331         snprintf(cc->cc_ktr_event_name, sizeof(cc->cc_ktr_event_name),
  332             "callwheel cpu %d", cpu);
  333         if (cc->cc_callout == NULL)     /* Only BSP handles timeout(9) */
  334                 return;
  335         for (i = 0; i < ncallout; i++) {
  336                 c = &cc->cc_callout[i];
  337                 callout_init(c, 0);
  338                 c->c_iflags = CALLOUT_LOCAL_ALLOC;
  339                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  340         }
  341 }
  342 
  343 #ifdef SMP
  344 /*
  345  * Switches the cpu tied to a specific callout.
  346  * The function expects a locked incoming callout cpu and returns with
  347  * locked outcoming callout cpu.
  348  */
  349 static struct callout_cpu *
  350 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
  351 {
  352         struct callout_cpu *new_cc;
  353 
  354         MPASS(c != NULL && cc != NULL);
  355         CC_LOCK_ASSERT(cc);
  356 
  357         /*
  358          * Avoid interrupts and preemption firing after the callout cpu
  359          * is blocked in order to avoid deadlocks as the new thread
  360          * may be willing to acquire the callout cpu lock.
  361          */
  362         c->c_cpu = CPUBLOCK;
  363         spinlock_enter();
  364         CC_UNLOCK(cc);
  365         new_cc = CC_CPU(new_cpu);
  366         CC_LOCK(new_cc);
  367         spinlock_exit();
  368         c->c_cpu = new_cpu;
  369         return (new_cc);
  370 }
  371 #endif
  372 
  373 /*
  374  * Start standard softclock thread.
  375  */
  376 static void
  377 start_softclock(void *dummy)
  378 {
  379         struct callout_cpu *cc;
  380         char name[MAXCOMLEN];
  381 #ifdef SMP
  382         int cpu;
  383         struct intr_event *ie;
  384 #endif
  385 
  386         cc = CC_CPU(timeout_cpu);
  387         snprintf(name, sizeof(name), "clock (%d)", timeout_cpu);
  388         if (swi_add(&clk_intr_event, name, softclock, cc, SWI_CLOCK,
  389             INTR_MPSAFE, &cc->cc_cookie))
  390                 panic("died while creating standard software ithreads");
  391         if (pin_default_swi &&
  392             (intr_event_bind(clk_intr_event, timeout_cpu) != 0)) {
  393                 printf("%s: timeout clock couldn't be pinned to cpu %d\n",
  394                     __func__,
  395                     timeout_cpu);
  396         }
  397 
  398 #ifdef SMP
  399         CPU_FOREACH(cpu) {
  400                 if (cpu == timeout_cpu)
  401                         continue;
  402                 cc = CC_CPU(cpu);
  403                 cc->cc_callout = NULL;  /* Only BSP handles timeout(9). */
  404                 callout_cpu_init(cc, cpu);
  405                 snprintf(name, sizeof(name), "clock (%d)", cpu);
  406                 ie = NULL;
  407                 if (swi_add(&ie, name, softclock, cc, SWI_CLOCK,
  408                     INTR_MPSAFE, &cc->cc_cookie))
  409                         panic("died while creating standard software ithreads");
  410                 if (pin_pcpu_swi && (intr_event_bind(ie, cpu) != 0)) {
  411                         printf("%s: per-cpu clock couldn't be pinned to "
  412                             "cpu %d\n",
  413                             __func__,
  414                             cpu);
  415                 }
  416         }
  417 #endif
  418 }
  419 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
  420 
  421 #define CC_HASH_SHIFT   8
  422 
  423 static inline u_int
  424 callout_hash(sbintime_t sbt)
  425 {
  426 
  427         return (sbt >> (32 - CC_HASH_SHIFT));
  428 }
  429 
  430 static inline u_int
  431 callout_get_bucket(sbintime_t sbt)
  432 {
  433 
  434         return (callout_hash(sbt) & callwheelmask);
  435 }
  436 
  437 void
  438 callout_process(sbintime_t now)
  439 {
  440         struct callout *tmp, *tmpn;
  441         struct callout_cpu *cc;
  442         struct callout_list *sc;
  443         sbintime_t first, last, max, tmp_max;
  444         uint32_t lookahead;
  445         u_int firstb, lastb, nowb;
  446 #ifdef CALLOUT_PROFILING
  447         int depth_dir = 0, mpcalls_dir = 0, lockcalls_dir = 0;
  448 #endif
  449 
  450         cc = CC_SELF();
  451         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  452 
  453         /* Compute the buckets of the last scan and present times. */
  454         firstb = callout_hash(cc->cc_lastscan);
  455         cc->cc_lastscan = now;
  456         nowb = callout_hash(now);
  457 
  458         /* Compute the last bucket and minimum time of the bucket after it. */
  459         if (nowb == firstb)
  460                 lookahead = (SBT_1S / 16);
  461         else if (nowb - firstb == 1)
  462                 lookahead = (SBT_1S / 8);
  463         else
  464                 lookahead = (SBT_1S / 2);
  465         first = last = now;
  466         first += (lookahead / 2);
  467         last += lookahead;
  468         last &= (0xffffffffffffffffLLU << (32 - CC_HASH_SHIFT));
  469         lastb = callout_hash(last) - 1;
  470         max = last;
  471 
  472         /*
  473          * Check if we wrapped around the entire wheel from the last scan.
  474          * In case, we need to scan entirely the wheel for pending callouts.
  475          */
  476         if (lastb - firstb >= callwheelsize) {
  477                 lastb = firstb + callwheelsize - 1;
  478                 if (nowb - firstb >= callwheelsize)
  479                         nowb = lastb;
  480         }
  481 
  482         /* Iterate callwheel from firstb to nowb and then up to lastb. */
  483         do {
  484                 sc = &cc->cc_callwheel[firstb & callwheelmask];
  485                 tmp = LIST_FIRST(sc);
  486                 while (tmp != NULL) {
  487                         /* Run the callout if present time within allowed. */
  488                         if (tmp->c_time <= now) {
  489                                 /*
  490                                  * Consumer told us the callout may be run
  491                                  * directly from hardware interrupt context.
  492                                  */
  493                                 if (tmp->c_iflags & CALLOUT_DIRECT) {
  494 #ifdef CALLOUT_PROFILING
  495                                         ++depth_dir;
  496 #endif
  497                                         cc_exec_next(cc) =
  498                                             LIST_NEXT(tmp, c_links.le);
  499                                         cc->cc_bucket = firstb & callwheelmask;
  500                                         LIST_REMOVE(tmp, c_links.le);
  501                                         softclock_call_cc(tmp, cc,
  502 #ifdef CALLOUT_PROFILING
  503                                             &mpcalls_dir, &lockcalls_dir, NULL,
  504 #endif
  505                                             1);
  506                                         tmp = cc_exec_next(cc);
  507                                         cc_exec_next(cc) = NULL;
  508                                 } else {
  509                                         tmpn = LIST_NEXT(tmp, c_links.le);
  510                                         LIST_REMOVE(tmp, c_links.le);
  511                                         TAILQ_INSERT_TAIL(&cc->cc_expireq,
  512                                             tmp, c_links.tqe);
  513                                         tmp->c_iflags |= CALLOUT_PROCESSED;
  514                                         tmp = tmpn;
  515                                 }
  516                                 continue;
  517                         }
  518                         /* Skip events from distant future. */
  519                         if (tmp->c_time >= max)
  520                                 goto next;
  521                         /*
  522                          * Event minimal time is bigger than present maximal
  523                          * time, so it cannot be aggregated.
  524                          */
  525                         if (tmp->c_time > last) {
  526                                 lastb = nowb;
  527                                 goto next;
  528                         }
  529                         /* Update first and last time, respecting this event. */
  530                         if (tmp->c_time < first)
  531                                 first = tmp->c_time;
  532                         tmp_max = tmp->c_time + tmp->c_precision;
  533                         if (tmp_max < last)
  534                                 last = tmp_max;
  535 next:
  536                         tmp = LIST_NEXT(tmp, c_links.le);
  537                 }
  538                 /* Proceed with the next bucket. */
  539                 firstb++;
  540                 /*
  541                  * Stop if we looked after present time and found
  542                  * some event we can't execute at now.
  543                  * Stop if we looked far enough into the future.
  544                  */
  545         } while (((int)(firstb - lastb)) <= 0);
  546         cc->cc_firstevent = last;
  547 #ifndef NO_EVENTTIMERS
  548         cpu_new_callout(curcpu, last, first);
  549 #endif
  550 #ifdef CALLOUT_PROFILING
  551         avg_depth_dir += (depth_dir * 1000 - avg_depth_dir) >> 8;
  552         avg_mpcalls_dir += (mpcalls_dir * 1000 - avg_mpcalls_dir) >> 8;
  553         avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
  554 #endif
  555         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  556         /*
  557          * swi_sched acquires the thread lock, so we don't want to call it
  558          * with cc_lock held; incorrect locking order.
  559          */
  560         if (!TAILQ_EMPTY(&cc->cc_expireq))
  561                 swi_sched(cc->cc_cookie, 0);
  562 }
  563 
  564 static struct callout_cpu *
  565 callout_lock(struct callout *c)
  566 {
  567         struct callout_cpu *cc;
  568         int cpu;
  569 
  570         for (;;) {
  571                 cpu = c->c_cpu;
  572 #ifdef SMP
  573                 if (cpu == CPUBLOCK) {
  574                         while (c->c_cpu == CPUBLOCK)
  575                                 cpu_spinwait();
  576                         continue;
  577                 }
  578 #endif
  579                 cc = CC_CPU(cpu);
  580                 CC_LOCK(cc);
  581                 if (cpu == c->c_cpu)
  582                         break;
  583                 CC_UNLOCK(cc);
  584         }
  585         return (cc);
  586 }
  587 
  588 static void
  589 callout_cc_add(struct callout *c, struct callout_cpu *cc,
  590     sbintime_t sbt, sbintime_t precision, void (*func)(void *),
  591     void *arg, int cpu, int flags)
  592 {
  593         int bucket;
  594 
  595         CC_LOCK_ASSERT(cc);
  596         if (sbt < cc->cc_lastscan)
  597                 sbt = cc->cc_lastscan;
  598         c->c_arg = arg;
  599         c->c_iflags |= CALLOUT_PENDING;
  600         c->c_iflags &= ~CALLOUT_PROCESSED;
  601         c->c_flags |= CALLOUT_ACTIVE;
  602         if (flags & C_DIRECT_EXEC)
  603                 c->c_iflags |= CALLOUT_DIRECT;
  604         c->c_func = func;
  605         c->c_time = sbt;
  606         c->c_precision = precision;
  607         bucket = callout_get_bucket(c->c_time);
  608         CTR3(KTR_CALLOUT, "precision set for %p: %d.%08x",
  609             c, (int)(c->c_precision >> 32),
  610             (u_int)(c->c_precision & 0xffffffff));
  611         LIST_INSERT_HEAD(&cc->cc_callwheel[bucket], c, c_links.le);
  612         if (cc->cc_bucket == bucket)
  613                 cc_exec_next(cc) = c;
  614 #ifndef NO_EVENTTIMERS
  615         /*
  616          * Inform the eventtimers(4) subsystem there's a new callout
  617          * that has been inserted, but only if really required.
  618          */
  619         if (SBT_MAX - c->c_time < c->c_precision)
  620                 c->c_precision = SBT_MAX - c->c_time;
  621         sbt = c->c_time + c->c_precision;
  622         if (sbt < cc->cc_firstevent) {
  623                 cc->cc_firstevent = sbt;
  624                 cpu_new_callout(cpu, sbt, c->c_time);
  625         }
  626 #endif
  627 }
  628 
  629 static void
  630 callout_cc_del(struct callout *c, struct callout_cpu *cc)
  631 {
  632 
  633         if ((c->c_iflags & CALLOUT_LOCAL_ALLOC) == 0)
  634                 return;
  635         c->c_func = NULL;
  636         SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  637 }
  638 
  639 static void
  640 softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  641 #ifdef CALLOUT_PROFILING
  642     int *mpcalls, int *lockcalls, int *gcalls,
  643 #endif
  644     int direct)
  645 {
  646         struct rm_priotracker tracker;
  647         void (*c_func)(void *);
  648         void *c_arg;
  649         struct lock_class *class;
  650         struct lock_object *c_lock;
  651         uintptr_t lock_status;
  652         int c_iflags;
  653 #ifdef SMP
  654         struct callout_cpu *new_cc;
  655         void (*new_func)(void *);
  656         void *new_arg;
  657         int flags, new_cpu;
  658         sbintime_t new_prec, new_time;
  659 #endif
  660 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING) 
  661         sbintime_t sbt1, sbt2;
  662         struct timespec ts2;
  663         static sbintime_t maxdt = 2 * SBT_1MS;  /* 2 msec */
  664         static timeout_t *lastfunc;
  665 #endif
  666 
  667         KASSERT((c->c_iflags & CALLOUT_PENDING) == CALLOUT_PENDING,
  668             ("softclock_call_cc: pend %p %x", c, c->c_iflags));
  669         KASSERT((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE,
  670             ("softclock_call_cc: act %p %x", c, c->c_flags));
  671         class = (c->c_lock != NULL) ? LOCK_CLASS(c->c_lock) : NULL;
  672         lock_status = 0;
  673         if (c->c_flags & CALLOUT_SHAREDLOCK) {
  674                 if (class == &lock_class_rm)
  675                         lock_status = (uintptr_t)&tracker;
  676                 else
  677                         lock_status = 1;
  678         }
  679         c_lock = c->c_lock;
  680         c_func = c->c_func;
  681         c_arg = c->c_arg;
  682         c_iflags = c->c_iflags;
  683         if (c->c_iflags & CALLOUT_LOCAL_ALLOC)
  684                 c->c_iflags = CALLOUT_LOCAL_ALLOC;
  685         else
  686                 c->c_iflags &= ~CALLOUT_PENDING;
  687         
  688         cc_exec_curr(cc, direct) = c;
  689         cc_exec_cancel(cc, direct) = false;
  690         cc_exec_drain(cc, direct) = NULL;
  691         CC_UNLOCK(cc);
  692         if (c_lock != NULL) {
  693                 class->lc_lock(c_lock, lock_status);
  694                 /*
  695                  * The callout may have been cancelled
  696                  * while we switched locks.
  697                  */
  698                 if (cc_exec_cancel(cc, direct)) {
  699                         class->lc_unlock(c_lock);
  700                         goto skip;
  701                 }
  702                 /* The callout cannot be stopped now. */
  703                 cc_exec_cancel(cc, direct) = true;
  704                 if (c_lock == &Giant.lock_object) {
  705 #ifdef CALLOUT_PROFILING
  706                         (*gcalls)++;
  707 #endif
  708                         CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
  709                             c, c_func, c_arg);
  710                 } else {
  711 #ifdef CALLOUT_PROFILING
  712                         (*lockcalls)++;
  713 #endif
  714                         CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
  715                             c, c_func, c_arg);
  716                 }
  717         } else {
  718 #ifdef CALLOUT_PROFILING
  719                 (*mpcalls)++;
  720 #endif
  721                 CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
  722                     c, c_func, c_arg);
  723         }
  724         KTR_STATE3(KTR_SCHED, "callout", cc->cc_ktr_event_name, "running",
  725             "func:%p", c_func, "arg:%p", c_arg, "direct:%d", direct);
  726 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  727         sbt1 = sbinuptime();
  728 #endif
  729         THREAD_NO_SLEEPING();
  730         SDT_PROBE1(callout_execute, , , callout__start, c);
  731         c_func(c_arg);
  732         SDT_PROBE1(callout_execute, , , callout__end, c);
  733         THREAD_SLEEPING_OK();
  734 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  735         sbt2 = sbinuptime();
  736         sbt2 -= sbt1;
  737         if (sbt2 > maxdt) {
  738                 if (lastfunc != c_func || sbt2 > maxdt * 2) {
  739                         ts2 = sbttots(sbt2);
  740                         printf(
  741                 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  742                             c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
  743                 }
  744                 maxdt = sbt2;
  745                 lastfunc = c_func;
  746         }
  747 #endif
  748         KTR_STATE0(KTR_SCHED, "callout", cc->cc_ktr_event_name, "idle");
  749         CTR1(KTR_CALLOUT, "callout %p finished", c);
  750         if ((c_iflags & CALLOUT_RETURNUNLOCKED) == 0)
  751                 class->lc_unlock(c_lock);
  752 skip:
  753         CC_LOCK(cc);
  754         KASSERT(cc_exec_curr(cc, direct) == c, ("mishandled cc_curr"));
  755         cc_exec_curr(cc, direct) = NULL;
  756         if (cc_exec_drain(cc, direct)) {
  757                 void (*drain)(void *);
  758                 
  759                 drain = cc_exec_drain(cc, direct);
  760                 cc_exec_drain(cc, direct) = NULL;
  761                 CC_UNLOCK(cc);
  762                 drain(c_arg);
  763                 CC_LOCK(cc);
  764         }
  765         if (cc_exec_waiting(cc, direct)) {
  766                 /*
  767                  * There is someone waiting for the
  768                  * callout to complete.
  769                  * If the callout was scheduled for
  770                  * migration just cancel it.
  771                  */
  772                 if (cc_cce_migrating(cc, direct)) {
  773                         cc_cce_cleanup(cc, direct);
  774 
  775                         /*
  776                          * It should be assert here that the callout is not
  777                          * destroyed but that is not easy.
  778                          */
  779                         c->c_iflags &= ~CALLOUT_DFRMIGRATION;
  780                 }
  781                 cc_exec_waiting(cc, direct) = false;
  782                 CC_UNLOCK(cc);
  783                 wakeup(&cc_exec_waiting(cc, direct));
  784                 CC_LOCK(cc);
  785         } else if (cc_cce_migrating(cc, direct)) {
  786                 KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0,
  787                     ("Migrating legacy callout %p", c));
  788 #ifdef SMP
  789                 /*
  790                  * If the callout was scheduled for
  791                  * migration just perform it now.
  792                  */
  793                 new_cpu = cc_migration_cpu(cc, direct);
  794                 new_time = cc_migration_time(cc, direct);
  795                 new_prec = cc_migration_prec(cc, direct);
  796                 new_func = cc_migration_func(cc, direct);
  797                 new_arg = cc_migration_arg(cc, direct);
  798                 cc_cce_cleanup(cc, direct);
  799 
  800                 /*
  801                  * It should be assert here that the callout is not destroyed
  802                  * but that is not easy.
  803                  *
  804                  * As first thing, handle deferred callout stops.
  805                  */
  806                 if (!callout_migrating(c)) {
  807                         CTR3(KTR_CALLOUT,
  808                              "deferred cancelled %p func %p arg %p",
  809                              c, new_func, new_arg);
  810                         callout_cc_del(c, cc);
  811                         return;
  812                 }
  813                 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
  814 
  815                 new_cc = callout_cpu_switch(c, cc, new_cpu);
  816                 flags = (direct) ? C_DIRECT_EXEC : 0;
  817                 callout_cc_add(c, new_cc, new_time, new_prec, new_func,
  818                     new_arg, new_cpu, flags);
  819                 CC_UNLOCK(new_cc);
  820                 CC_LOCK(cc);
  821 #else
  822                 panic("migration should not happen");
  823 #endif
  824         }
  825         /*
  826          * If the current callout is locally allocated (from
  827          * timeout(9)) then put it on the freelist.
  828          *
  829          * Note: we need to check the cached copy of c_iflags because
  830          * if it was not local, then it's not safe to deref the
  831          * callout pointer.
  832          */
  833         KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0 ||
  834             c->c_iflags == CALLOUT_LOCAL_ALLOC,
  835             ("corrupted callout"));
  836         if (c_iflags & CALLOUT_LOCAL_ALLOC)
  837                 callout_cc_del(c, cc);
  838 }
  839 
  840 /*
  841  * The callout mechanism is based on the work of Adam M. Costello and
  842  * George Varghese, published in a technical report entitled "Redesigning
  843  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  844  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  845  * used in this implementation was published by G. Varghese and T. Lauck in
  846  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  847  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  848  * the 11th ACM Annual Symposium on Operating Systems Principles,
  849  * Austin, Texas Nov 1987.
  850  */
  851 
  852 /*
  853  * Software (low priority) clock interrupt.
  854  * Run periodic events from timeout queue.
  855  */
  856 void
  857 softclock(void *arg)
  858 {
  859         struct callout_cpu *cc;
  860         struct callout *c;
  861 #ifdef CALLOUT_PROFILING
  862         int depth = 0, gcalls = 0, lockcalls = 0, mpcalls = 0;
  863 #endif
  864 
  865         cc = (struct callout_cpu *)arg;
  866         CC_LOCK(cc);
  867         while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
  868                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
  869                 softclock_call_cc(c, cc,
  870 #ifdef CALLOUT_PROFILING
  871                     &mpcalls, &lockcalls, &gcalls,
  872 #endif
  873                     0);
  874 #ifdef CALLOUT_PROFILING
  875                 ++depth;
  876 #endif
  877         }
  878 #ifdef CALLOUT_PROFILING
  879         avg_depth += (depth * 1000 - avg_depth) >> 8;
  880         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  881         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  882         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  883 #endif
  884         CC_UNLOCK(cc);
  885 }
  886 
  887 /*
  888  * timeout --
  889  *      Execute a function after a specified length of time.
  890  *
  891  * untimeout --
  892  *      Cancel previous timeout function call.
  893  *
  894  * callout_handle_init --
  895  *      Initialize a handle so that using it with untimeout is benign.
  896  *
  897  *      See AT&T BCI Driver Reference Manual for specification.  This
  898  *      implementation differs from that one in that although an
  899  *      identification value is returned from timeout, the original
  900  *      arguments to timeout as well as the identifier are used to
  901  *      identify entries for untimeout.
  902  */
  903 struct callout_handle
  904 timeout(timeout_t *ftn, void *arg, int to_ticks)
  905 {
  906         struct callout_cpu *cc;
  907         struct callout *new;
  908         struct callout_handle handle;
  909 
  910         cc = CC_CPU(timeout_cpu);
  911         CC_LOCK(cc);
  912         /* Fill in the next free callout structure. */
  913         new = SLIST_FIRST(&cc->cc_callfree);
  914         if (new == NULL)
  915                 /* XXX Attempt to malloc first */
  916                 panic("timeout table full");
  917         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  918         callout_reset(new, to_ticks, ftn, arg);
  919         handle.callout = new;
  920         CC_UNLOCK(cc);
  921 
  922         return (handle);
  923 }
  924 
  925 void
  926 untimeout(timeout_t *ftn, void *arg, struct callout_handle handle)
  927 {
  928         struct callout_cpu *cc;
  929 
  930         /*
  931          * Check for a handle that was initialized
  932          * by callout_handle_init, but never used
  933          * for a real timeout.
  934          */
  935         if (handle.callout == NULL)
  936                 return;
  937 
  938         cc = callout_lock(handle.callout);
  939         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  940                 callout_stop(handle.callout);
  941         CC_UNLOCK(cc);
  942 }
  943 
  944 void
  945 callout_handle_init(struct callout_handle *handle)
  946 {
  947         handle->callout = NULL;
  948 }
  949 
  950 void
  951 callout_when(sbintime_t sbt, sbintime_t precision, int flags,
  952     sbintime_t *res, sbintime_t *prec_res)
  953 {
  954         sbintime_t to_sbt, to_pr;
  955 
  956         if ((flags & (C_ABSOLUTE | C_PRECALC)) != 0) {
  957                 *res = sbt;
  958                 *prec_res = precision;
  959                 return;
  960         }
  961         if ((flags & C_HARDCLOCK) != 0 && sbt < tick_sbt)
  962                 sbt = tick_sbt;
  963         if ((flags & C_HARDCLOCK) != 0 ||
  964 #ifdef NO_EVENTTIMERS
  965             sbt >= sbt_timethreshold) {
  966                 to_sbt = getsbinuptime();
  967 
  968                 /* Add safety belt for the case of hz > 1000. */
  969                 to_sbt += tc_tick_sbt - tick_sbt;
  970 #else
  971             sbt >= sbt_tickthreshold) {
  972                 /*
  973                  * Obtain the time of the last hardclock() call on
  974                  * this CPU directly from the kern_clocksource.c.
  975                  * This value is per-CPU, but it is equal for all
  976                  * active ones.
  977                  */
  978 #ifdef __LP64__
  979                 to_sbt = DPCPU_GET(hardclocktime);
  980 #else
  981                 spinlock_enter();
  982                 to_sbt = DPCPU_GET(hardclocktime);
  983                 spinlock_exit();
  984 #endif
  985 #endif
  986                 if (cold && to_sbt == 0)
  987                         to_sbt = sbinuptime();
  988                 if ((flags & C_HARDCLOCK) == 0)
  989                         to_sbt += tick_sbt;
  990         } else
  991                 to_sbt = sbinuptime();
  992         if (SBT_MAX - to_sbt < sbt)
  993                 to_sbt = SBT_MAX;
  994         else
  995                 to_sbt += sbt;
  996         *res = to_sbt;
  997         to_pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
  998             sbt >> C_PRELGET(flags));
  999         *prec_res = to_pr > precision ? to_pr : precision;
 1000 }
 1001 
 1002 /*
 1003  * New interface; clients allocate their own callout structures.
 1004  *
 1005  * callout_reset() - establish or change a timeout
 1006  * callout_stop() - disestablish a timeout
 1007  * callout_init() - initialize a callout structure so that it can
 1008  *      safely be passed to callout_reset() and callout_stop()
 1009  *
 1010  * <sys/callout.h> defines three convenience macros:
 1011  *
 1012  * callout_active() - returns truth if callout has not been stopped,
 1013  *      drained, or deactivated since the last time the callout was
 1014  *      reset.
 1015  * callout_pending() - returns truth if callout is still waiting for timeout
 1016  * callout_deactivate() - marks the callout as having been serviced
 1017  */
 1018 int
 1019 callout_reset_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t prec,
 1020     void (*ftn)(void *), void *arg, int cpu, int flags)
 1021 {
 1022         sbintime_t to_sbt, precision;
 1023         struct callout_cpu *cc;
 1024         int cancelled, direct;
 1025         int ignore_cpu=0;
 1026 
 1027         cancelled = 0;
 1028         if (cpu == -1) {
 1029                 ignore_cpu = 1;
 1030         } else if ((cpu >= MAXCPU) ||
 1031                    ((CC_CPU(cpu))->cc_inited == 0)) {
 1032                 /* Invalid CPU spec */
 1033                 panic("Invalid CPU in callout %d", cpu);
 1034         }
 1035         callout_when(sbt, prec, flags, &to_sbt, &precision);
 1036 
 1037         /* 
 1038          * This flag used to be added by callout_cc_add, but the
 1039          * first time you call this we could end up with the
 1040          * wrong direct flag if we don't do it before we add.
 1041          */
 1042         if (flags & C_DIRECT_EXEC) {
 1043                 direct = 1;
 1044         } else {
 1045                 direct = 0;
 1046         }
 1047         KASSERT(!direct || c->c_lock == NULL,
 1048             ("%s: direct callout %p has lock", __func__, c));
 1049         cc = callout_lock(c);
 1050         /*
 1051          * Don't allow migration of pre-allocated callouts lest they
 1052          * become unbalanced or handle the case where the user does
 1053          * not care. 
 1054          */
 1055         if ((c->c_iflags & CALLOUT_LOCAL_ALLOC) ||
 1056             ignore_cpu) {
 1057                 cpu = c->c_cpu;
 1058         }
 1059 
 1060         if (cc_exec_curr(cc, direct) == c) {
 1061                 /*
 1062                  * We're being asked to reschedule a callout which is
 1063                  * currently in progress.  If there is a lock then we
 1064                  * can cancel the callout if it has not really started.
 1065                  */
 1066                 if (c->c_lock != NULL && !cc_exec_cancel(cc, direct))
 1067                         cancelled = cc_exec_cancel(cc, direct) = true;
 1068                 if (cc_exec_waiting(cc, direct) || cc_exec_drain(cc, direct)) {
 1069                         /*
 1070                          * Someone has called callout_drain to kill this
 1071                          * callout.  Don't reschedule.
 1072                          */
 1073                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
 1074                             cancelled ? "cancelled" : "failed to cancel",
 1075                             c, c->c_func, c->c_arg);
 1076                         CC_UNLOCK(cc);
 1077                         return (cancelled);
 1078                 }
 1079 #ifdef SMP
 1080                 if (callout_migrating(c)) {
 1081                         /* 
 1082                          * This only occurs when a second callout_reset_sbt_on
 1083                          * is made after a previous one moved it into
 1084                          * deferred migration (below). Note we do *not* change
 1085                          * the prev_cpu even though the previous target may
 1086                          * be different.
 1087                          */
 1088                         cc_migration_cpu(cc, direct) = cpu;
 1089                         cc_migration_time(cc, direct) = to_sbt;
 1090                         cc_migration_prec(cc, direct) = precision;
 1091                         cc_migration_func(cc, direct) = ftn;
 1092                         cc_migration_arg(cc, direct) = arg;
 1093                         cancelled = 1;
 1094                         CC_UNLOCK(cc);
 1095                         return (cancelled);
 1096                 }
 1097 #endif
 1098         }
 1099         if (c->c_iflags & CALLOUT_PENDING) {
 1100                 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
 1101                         if (cc_exec_next(cc) == c)
 1102                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1103                         LIST_REMOVE(c, c_links.le);
 1104                 } else {
 1105                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1106                 }
 1107                 cancelled = 1;
 1108                 c->c_iflags &= ~ CALLOUT_PENDING;
 1109                 c->c_flags &= ~ CALLOUT_ACTIVE;
 1110         }
 1111 
 1112 #ifdef SMP
 1113         /*
 1114          * If the callout must migrate try to perform it immediately.
 1115          * If the callout is currently running, just defer the migration
 1116          * to a more appropriate moment.
 1117          */
 1118         if (c->c_cpu != cpu) {
 1119                 if (cc_exec_curr(cc, direct) == c) {
 1120                         /* 
 1121                          * Pending will have been removed since we are
 1122                          * actually executing the callout on another
 1123                          * CPU. That callout should be waiting on the
 1124                          * lock the caller holds. If we set both
 1125                          * active/and/pending after we return and the
 1126                          * lock on the executing callout proceeds, it
 1127                          * will then see pending is true and return.
 1128                          * At the return from the actual callout execution
 1129                          * the migration will occur in softclock_call_cc
 1130                          * and this new callout will be placed on the 
 1131                          * new CPU via a call to callout_cpu_switch() which
 1132                          * will get the lock on the right CPU followed
 1133                          * by a call callout_cc_add() which will add it there.
 1134                          * (see above in softclock_call_cc()).
 1135                          */
 1136                         cc_migration_cpu(cc, direct) = cpu;
 1137                         cc_migration_time(cc, direct) = to_sbt;
 1138                         cc_migration_prec(cc, direct) = precision;
 1139                         cc_migration_func(cc, direct) = ftn;
 1140                         cc_migration_arg(cc, direct) = arg;
 1141                         c->c_iflags |= (CALLOUT_DFRMIGRATION | CALLOUT_PENDING);
 1142                         c->c_flags |= CALLOUT_ACTIVE;
 1143                         CTR6(KTR_CALLOUT,
 1144                     "migration of %p func %p arg %p in %d.%08x to %u deferred",
 1145                             c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1146                             (u_int)(to_sbt & 0xffffffff), cpu);
 1147                         CC_UNLOCK(cc);
 1148                         return (cancelled);
 1149                 }
 1150                 cc = callout_cpu_switch(c, cc, cpu);
 1151         }
 1152 #endif
 1153 
 1154         callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
 1155         CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
 1156             cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1157             (u_int)(to_sbt & 0xffffffff));
 1158         CC_UNLOCK(cc);
 1159 
 1160         return (cancelled);
 1161 }
 1162 
 1163 /*
 1164  * Common idioms that can be optimized in the future.
 1165  */
 1166 int
 1167 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
 1168 {
 1169         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
 1170 }
 1171 
 1172 int
 1173 callout_schedule(struct callout *c, int to_ticks)
 1174 {
 1175         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
 1176 }
 1177 
 1178 int
 1179 _callout_stop_safe(struct callout *c, int flags, void (*drain)(void *))
 1180 {
 1181         struct callout_cpu *cc, *old_cc;
 1182         struct lock_class *class;
 1183         int direct, sq_locked, use_lock;
 1184         int cancelled, not_on_a_list;
 1185 
 1186         if ((flags & CS_DRAIN) != 0)
 1187                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
 1188                     "calling %s", __func__);
 1189 
 1190         /*
 1191          * Some old subsystems don't hold Giant while running a callout_stop(),
 1192          * so just discard this check for the moment.
 1193          */
 1194         if ((flags & CS_DRAIN) == 0 && c->c_lock != NULL) {
 1195                 if (c->c_lock == &Giant.lock_object)
 1196                         use_lock = mtx_owned(&Giant);
 1197                 else {
 1198                         use_lock = 1;
 1199                         class = LOCK_CLASS(c->c_lock);
 1200                         class->lc_assert(c->c_lock, LA_XLOCKED);
 1201                 }
 1202         } else
 1203                 use_lock = 0;
 1204         if (c->c_iflags & CALLOUT_DIRECT) {
 1205                 direct = 1;
 1206         } else {
 1207                 direct = 0;
 1208         }
 1209         sq_locked = 0;
 1210         old_cc = NULL;
 1211 again:
 1212         cc = callout_lock(c);
 1213 
 1214         if ((c->c_iflags & (CALLOUT_DFRMIGRATION | CALLOUT_PENDING)) ==
 1215             (CALLOUT_DFRMIGRATION | CALLOUT_PENDING) &&
 1216             ((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE)) {
 1217                 /*
 1218                  * Special case where this slipped in while we
 1219                  * were migrating *as* the callout is about to
 1220                  * execute. The caller probably holds the lock
 1221                  * the callout wants.
 1222                  *
 1223                  * Get rid of the migration first. Then set
 1224                  * the flag that tells this code *not* to
 1225                  * try to remove it from any lists (its not
 1226                  * on one yet). When the callout wheel runs,
 1227                  * it will ignore this callout.
 1228                  */
 1229                 c->c_iflags &= ~CALLOUT_PENDING;
 1230                 c->c_flags &= ~CALLOUT_ACTIVE;
 1231                 not_on_a_list = 1;
 1232         } else {
 1233                 not_on_a_list = 0;
 1234         }
 1235 
 1236         /*
 1237          * If the callout was migrating while the callout cpu lock was
 1238          * dropped,  just drop the sleepqueue lock and check the states
 1239          * again.
 1240          */
 1241         if (sq_locked != 0 && cc != old_cc) {
 1242 #ifdef SMP
 1243                 CC_UNLOCK(cc);
 1244                 sleepq_release(&cc_exec_waiting(old_cc, direct));
 1245                 sq_locked = 0;
 1246                 old_cc = NULL;
 1247                 goto again;
 1248 #else
 1249                 panic("migration should not happen");
 1250 #endif
 1251         }
 1252 
 1253         /*
 1254          * If the callout is running, try to stop it or drain it.
 1255          */
 1256         if (cc_exec_curr(cc, direct) == c) {
 1257                 /*
 1258                  * Succeed we to stop it or not, we must clear the
 1259                  * active flag - this is what API users expect.  If we're
 1260                  * draining and the callout is currently executing, first wait
 1261                  * until it finishes.
 1262                  */
 1263                 if ((flags & CS_DRAIN) == 0)
 1264                         c->c_flags &= ~CALLOUT_ACTIVE;
 1265 
 1266                 if ((flags & CS_DRAIN) != 0) {
 1267                         /*
 1268                          * The current callout is running (or just
 1269                          * about to run) and blocking is allowed, so
 1270                          * just wait for the current invocation to
 1271                          * finish.
 1272                          */
 1273                         while (cc_exec_curr(cc, direct) == c) {
 1274                                 /*
 1275                                  * Use direct calls to sleepqueue interface
 1276                                  * instead of cv/msleep in order to avoid
 1277                                  * a LOR between cc_lock and sleepqueue
 1278                                  * chain spinlocks.  This piece of code
 1279                                  * emulates a msleep_spin() call actually.
 1280                                  *
 1281                                  * If we already have the sleepqueue chain
 1282                                  * locked, then we can safely block.  If we
 1283                                  * don't already have it locked, however,
 1284                                  * we have to drop the cc_lock to lock
 1285                                  * it.  This opens several races, so we
 1286                                  * restart at the beginning once we have
 1287                                  * both locks.  If nothing has changed, then
 1288                                  * we will end up back here with sq_locked
 1289                                  * set.
 1290                                  */
 1291                                 if (!sq_locked) {
 1292                                         CC_UNLOCK(cc);
 1293                                         sleepq_lock(
 1294                                             &cc_exec_waiting(cc, direct));
 1295                                         sq_locked = 1;
 1296                                         old_cc = cc;
 1297                                         goto again;
 1298                                 }
 1299 
 1300                                 /*
 1301                                  * Migration could be cancelled here, but
 1302                                  * as long as it is still not sure when it
 1303                                  * will be packed up, just let softclock()
 1304                                  * take care of it.
 1305                                  */
 1306                                 cc_exec_waiting(cc, direct) = true;
 1307                                 DROP_GIANT();
 1308                                 CC_UNLOCK(cc);
 1309                                 sleepq_add(
 1310                                     &cc_exec_waiting(cc, direct),
 1311                                     &cc->cc_lock.lock_object, "codrain",
 1312                                     SLEEPQ_SLEEP, 0);
 1313                                 sleepq_wait(
 1314                                     &cc_exec_waiting(cc, direct),
 1315                                              0);
 1316                                 sq_locked = 0;
 1317                                 old_cc = NULL;
 1318 
 1319                                 /* Reacquire locks previously released. */
 1320                                 PICKUP_GIANT();
 1321                                 CC_LOCK(cc);
 1322                         }
 1323                         c->c_flags &= ~CALLOUT_ACTIVE;
 1324                 } else if (use_lock &&
 1325                            !cc_exec_cancel(cc, direct) && (drain == NULL)) {
 1326                         
 1327                         /*
 1328                          * The current callout is waiting for its
 1329                          * lock which we hold.  Cancel the callout
 1330                          * and return.  After our caller drops the
 1331                          * lock, the callout will be skipped in
 1332                          * softclock(). This *only* works with a
 1333                          * callout_stop() *not* callout_drain() or
 1334                          * callout_async_drain().
 1335                          */
 1336                         cc_exec_cancel(cc, direct) = true;
 1337                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1338                             c, c->c_func, c->c_arg);
 1339                         KASSERT(!cc_cce_migrating(cc, direct),
 1340                             ("callout wrongly scheduled for migration"));
 1341                         if (callout_migrating(c)) {
 1342                                 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
 1343 #ifdef SMP
 1344                                 cc_migration_cpu(cc, direct) = CPUBLOCK;
 1345                                 cc_migration_time(cc, direct) = 0;
 1346                                 cc_migration_prec(cc, direct) = 0;
 1347                                 cc_migration_func(cc, direct) = NULL;
 1348                                 cc_migration_arg(cc, direct) = NULL;
 1349 #endif
 1350                         }
 1351                         CC_UNLOCK(cc);
 1352                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
 1353                         return (1);
 1354                 } else if (callout_migrating(c)) {
 1355                         /*
 1356                          * The callout is currently being serviced
 1357                          * and the "next" callout is scheduled at
 1358                          * its completion with a migration. We remove
 1359                          * the migration flag so it *won't* get rescheduled,
 1360                          * but we can't stop the one thats running so
 1361                          * we return 0.
 1362                          */
 1363                         c->c_iflags &= ~CALLOUT_DFRMIGRATION;
 1364 #ifdef SMP
 1365                         /* 
 1366                          * We can't call cc_cce_cleanup here since
 1367                          * if we do it will remove .ce_curr and
 1368                          * its still running. This will prevent a
 1369                          * reschedule of the callout when the 
 1370                          * execution completes.
 1371                          */
 1372                         cc_migration_cpu(cc, direct) = CPUBLOCK;
 1373                         cc_migration_time(cc, direct) = 0;
 1374                         cc_migration_prec(cc, direct) = 0;
 1375                         cc_migration_func(cc, direct) = NULL;
 1376                         cc_migration_arg(cc, direct) = NULL;
 1377 #endif
 1378                         CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
 1379                             c, c->c_func, c->c_arg);
 1380                         if (drain) {
 1381                                 cc_exec_drain(cc, direct) = drain;
 1382                         }
 1383                         CC_UNLOCK(cc);
 1384                         return ((flags & CS_EXECUTING) != 0);
 1385                 }
 1386                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1387                     c, c->c_func, c->c_arg);
 1388                 if (drain) {
 1389                         cc_exec_drain(cc, direct) = drain;
 1390                 }
 1391                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
 1392                 cancelled = ((flags & CS_EXECUTING) != 0);
 1393         } else
 1394                 cancelled = 1;
 1395 
 1396         if (sq_locked)
 1397                 sleepq_release(&cc_exec_waiting(cc, direct));
 1398 
 1399         if ((c->c_iflags & CALLOUT_PENDING) == 0) {
 1400                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1401                     c, c->c_func, c->c_arg);
 1402                 /*
 1403                  * For not scheduled and not executing callout return
 1404                  * negative value.
 1405                  */
 1406                 if (cc_exec_curr(cc, direct) != c)
 1407                         cancelled = -1;
 1408                 CC_UNLOCK(cc);
 1409                 return (cancelled);
 1410         }
 1411 
 1412         c->c_iflags &= ~CALLOUT_PENDING;
 1413         c->c_flags &= ~CALLOUT_ACTIVE;
 1414 
 1415         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1416             c, c->c_func, c->c_arg);
 1417         if (not_on_a_list == 0) {
 1418                 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
 1419                         if (cc_exec_next(cc) == c)
 1420                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1421                         LIST_REMOVE(c, c_links.le);
 1422                 } else {
 1423                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1424                 }
 1425         }
 1426         callout_cc_del(c, cc);
 1427         CC_UNLOCK(cc);
 1428         return (cancelled);
 1429 }
 1430 
 1431 void
 1432 callout_init(struct callout *c, int mpsafe)
 1433 {
 1434         bzero(c, sizeof *c);
 1435         if (mpsafe) {
 1436                 c->c_lock = NULL;
 1437                 c->c_iflags = CALLOUT_RETURNUNLOCKED;
 1438         } else {
 1439                 c->c_lock = &Giant.lock_object;
 1440                 c->c_iflags = 0;
 1441         }
 1442         c->c_cpu = timeout_cpu;
 1443 }
 1444 
 1445 void
 1446 _callout_init_lock(struct callout *c, struct lock_object *lock, int flags)
 1447 {
 1448         bzero(c, sizeof *c);
 1449         c->c_lock = lock;
 1450         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
 1451             ("callout_init_lock: bad flags %d", flags));
 1452         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
 1453             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
 1454         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
 1455             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
 1456             __func__));
 1457         c->c_iflags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
 1458         c->c_cpu = timeout_cpu;
 1459 }
 1460 
 1461 #ifdef APM_FIXUP_CALLTODO
 1462 /* 
 1463  * Adjust the kernel calltodo timeout list.  This routine is used after 
 1464  * an APM resume to recalculate the calltodo timer list values with the 
 1465  * number of hz's we have been sleeping.  The next hardclock() will detect 
 1466  * that there are fired timers and run softclock() to execute them.
 1467  *
 1468  * Please note, I have not done an exhaustive analysis of what code this
 1469  * might break.  I am motivated to have my select()'s and alarm()'s that
 1470  * have expired during suspend firing upon resume so that the applications
 1471  * which set the timer can do the maintanence the timer was for as close
 1472  * as possible to the originally intended time.  Testing this code for a 
 1473  * week showed that resuming from a suspend resulted in 22 to 25 timers 
 1474  * firing, which seemed independent on whether the suspend was 2 hours or
 1475  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 1476  */
 1477 void
 1478 adjust_timeout_calltodo(struct timeval *time_change)
 1479 {
 1480         struct callout *p;
 1481         unsigned long delta_ticks;
 1482 
 1483         /* 
 1484          * How many ticks were we asleep?
 1485          * (stolen from tvtohz()).
 1486          */
 1487 
 1488         /* Don't do anything */
 1489         if (time_change->tv_sec < 0)
 1490                 return;
 1491         else if (time_change->tv_sec <= LONG_MAX / 1000000)
 1492                 delta_ticks = howmany(time_change->tv_sec * 1000000 +
 1493                     time_change->tv_usec, tick) + 1;
 1494         else if (time_change->tv_sec <= LONG_MAX / hz)
 1495                 delta_ticks = time_change->tv_sec * hz +
 1496                     howmany(time_change->tv_usec, tick) + 1;
 1497         else
 1498                 delta_ticks = LONG_MAX;
 1499 
 1500         if (delta_ticks > INT_MAX)
 1501                 delta_ticks = INT_MAX;
 1502 
 1503         /* 
 1504          * Now rip through the timer calltodo list looking for timers
 1505          * to expire.
 1506          */
 1507 
 1508         /* don't collide with softclock() */
 1509         CC_LOCK(cc);
 1510         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 1511                 p->c_time -= delta_ticks;
 1512 
 1513                 /* Break if the timer had more time on it than delta_ticks */
 1514                 if (p->c_time > 0)
 1515                         break;
 1516 
 1517                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
 1518                 delta_ticks = -p->c_time;
 1519         }
 1520         CC_UNLOCK(cc);
 1521 
 1522         return;
 1523 }
 1524 #endif /* APM_FIXUP_CALLTODO */
 1525 
 1526 static int
 1527 flssbt(sbintime_t sbt)
 1528 {
 1529 
 1530         sbt += (uint64_t)sbt >> 1;
 1531         if (sizeof(long) >= sizeof(sbintime_t))
 1532                 return (flsl(sbt));
 1533         if (sbt >= SBT_1S)
 1534                 return (flsl(((uint64_t)sbt) >> 32) + 32);
 1535         return (flsl(sbt));
 1536 }
 1537 
 1538 /*
 1539  * Dump immediate statistic snapshot of the scheduled callouts.
 1540  */
 1541 static int
 1542 sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
 1543 {
 1544         struct callout *tmp;
 1545         struct callout_cpu *cc;
 1546         struct callout_list *sc;
 1547         sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
 1548         int ct[64], cpr[64], ccpbk[32];
 1549         int error, val, i, count, tcum, pcum, maxc, c, medc;
 1550 #ifdef SMP
 1551         int cpu;
 1552 #endif
 1553 
 1554         val = 0;
 1555         error = sysctl_handle_int(oidp, &val, 0, req);
 1556         if (error != 0 || req->newptr == NULL)
 1557                 return (error);
 1558         count = maxc = 0;
 1559         st = spr = maxt = maxpr = 0;
 1560         bzero(ccpbk, sizeof(ccpbk));
 1561         bzero(ct, sizeof(ct));
 1562         bzero(cpr, sizeof(cpr));
 1563         now = sbinuptime();
 1564 #ifdef SMP
 1565         CPU_FOREACH(cpu) {
 1566                 cc = CC_CPU(cpu);
 1567 #else
 1568                 cc = CC_CPU(timeout_cpu);
 1569 #endif
 1570                 CC_LOCK(cc);
 1571                 for (i = 0; i < callwheelsize; i++) {
 1572                         sc = &cc->cc_callwheel[i];
 1573                         c = 0;
 1574                         LIST_FOREACH(tmp, sc, c_links.le) {
 1575                                 c++;
 1576                                 t = tmp->c_time - now;
 1577                                 if (t < 0)
 1578                                         t = 0;
 1579                                 st += t / SBT_1US;
 1580                                 spr += tmp->c_precision / SBT_1US;
 1581                                 if (t > maxt)
 1582                                         maxt = t;
 1583                                 if (tmp->c_precision > maxpr)
 1584                                         maxpr = tmp->c_precision;
 1585                                 ct[flssbt(t)]++;
 1586                                 cpr[flssbt(tmp->c_precision)]++;
 1587                         }
 1588                         if (c > maxc)
 1589                                 maxc = c;
 1590                         ccpbk[fls(c + c / 2)]++;
 1591                         count += c;
 1592                 }
 1593                 CC_UNLOCK(cc);
 1594 #ifdef SMP
 1595         }
 1596 #endif
 1597 
 1598         for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
 1599                 tcum += ct[i];
 1600         medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1601         for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
 1602                 pcum += cpr[i];
 1603         medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1604         for (i = 0, c = 0; i < 32 && c < count / 2; i++)
 1605                 c += ccpbk[i];
 1606         medc = (i >= 2) ? (1 << (i - 2)) : 0;
 1607 
 1608         printf("Scheduled callouts statistic snapshot:\n");
 1609         printf("  Callouts: %6d  Buckets: %6d*%-3d  Bucket size: 0.%06ds\n",
 1610             count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
 1611         printf("  C/Bk: med %5d         avg %6d.%06jd  max %6d\n",
 1612             medc,
 1613             count / callwheelsize / mp_ncpus,
 1614             (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
 1615             maxc);
 1616         printf("  Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1617             medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
 1618             (st / count) / 1000000, (st / count) % 1000000,
 1619             maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
 1620         printf("  Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1621             medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
 1622             (spr / count) / 1000000, (spr / count) % 1000000,
 1623             maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
 1624         printf("  Distribution:       \tbuckets\t   time\t   tcum\t"
 1625             "   prec\t   pcum\n");
 1626         for (i = 0, tcum = pcum = 0; i < 64; i++) {
 1627                 if (ct[i] == 0 && cpr[i] == 0)
 1628                         continue;
 1629                 t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
 1630                 tcum += ct[i];
 1631                 pcum += cpr[i];
 1632                 printf("  %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
 1633                     t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
 1634                     i - 1 - (32 - CC_HASH_SHIFT),
 1635                     ct[i], tcum, cpr[i], pcum);
 1636         }
 1637         return (error);
 1638 }
 1639 SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
 1640     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 1641     0, 0, sysctl_kern_callout_stat, "I",
 1642     "Dump immediate statistic snapshot of the scheduled callouts");
 1643 
 1644 #ifdef DDB
 1645 static void
 1646 _show_callout(struct callout *c)
 1647 {
 1648 
 1649         db_printf("callout %p\n", c);
 1650 #define C_DB_PRINTF(f, e)       db_printf("   %s = " f "\n", #e, c->e);
 1651         db_printf("   &c_links = %p\n", &(c->c_links));
 1652         C_DB_PRINTF("%" PRId64, c_time);
 1653         C_DB_PRINTF("%" PRId64, c_precision);
 1654         C_DB_PRINTF("%p",       c_arg);
 1655         C_DB_PRINTF("%p",       c_func);
 1656         C_DB_PRINTF("%p",       c_lock);
 1657         C_DB_PRINTF("%#x",      c_flags);
 1658         C_DB_PRINTF("%#x",      c_iflags);
 1659         C_DB_PRINTF("%d",       c_cpu);
 1660 #undef  C_DB_PRINTF
 1661 }
 1662 
 1663 DB_SHOW_COMMAND(callout, db_show_callout)
 1664 {
 1665 
 1666         if (!have_addr) {
 1667                 db_printf("usage: show callout <struct callout *>\n");
 1668                 return;
 1669         }
 1670 
 1671         _show_callout((struct callout *)addr);
 1672 }
 1673 #endif /* DDB */

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