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: head/sys/kern/kern_timeout.c 296320 2016-03-02 18:46:17Z kib $");
   39 
   40 #include "opt_callout_profiling.h"
   41 #if defined(__arm__)
   42 #include "opt_timer.h"
   43 #endif
   44 #include "opt_rss.h"
   45 
   46 #include <sys/param.h>
   47 #include <sys/systm.h>
   48 #include <sys/bus.h>
   49 #include <sys/callout.h>
   50 #include <sys/file.h>
   51 #include <sys/interrupt.h>
   52 #include <sys/kernel.h>
   53 #include <sys/ktr.h>
   54 #include <sys/lock.h>
   55 #include <sys/malloc.h>
   56 #include <sys/mutex.h>
   57 #include <sys/proc.h>
   58 #include <sys/sdt.h>
   59 #include <sys/sleepqueue.h>
   60 #include <sys/sysctl.h>
   61 #include <sys/smp.h>
   62 
   63 #ifdef SMP
   64 #include <machine/cpu.h>
   65 #endif
   66 
   67 #ifndef NO_EVENTTIMERS
   68 DPCPU_DECLARE(sbintime_t, hardclocktime);
   69 #endif
   70 
   71 SDT_PROVIDER_DEFINE(callout_execute);
   72 SDT_PROBE_DEFINE1(callout_execute, , , callout__start, "struct callout *");
   73 SDT_PROBE_DEFINE1(callout_execute, , , callout__end, "struct callout *");
   74 
   75 #ifdef CALLOUT_PROFILING
   76 static int avg_depth;
   77 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
   78     "Average number of items examined per softclock call. Units = 1/1000");
   79 static int avg_gcalls;
   80 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
   81     "Average number of Giant callouts made per softclock call. Units = 1/1000");
   82 static int avg_lockcalls;
   83 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
   84     "Average number of lock callouts made per softclock call. Units = 1/1000");
   85 static int avg_mpcalls;
   86 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
   87     "Average number of MP callouts made per softclock call. Units = 1/1000");
   88 static int avg_depth_dir;
   89 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth_dir, CTLFLAG_RD, &avg_depth_dir, 0,
   90     "Average number of direct callouts examined per callout_process call. "
   91     "Units = 1/1000");
   92 static int avg_lockcalls_dir;
   93 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls_dir, CTLFLAG_RD,
   94     &avg_lockcalls_dir, 0, "Average number of lock direct callouts made per "
   95     "callout_process call. Units = 1/1000");
   96 static int avg_mpcalls_dir;
   97 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls_dir, CTLFLAG_RD, &avg_mpcalls_dir,
   98     0, "Average number of MP direct callouts made per callout_process call. "
   99     "Units = 1/1000");
  100 #endif
  101 
  102 static int ncallout;
  103 SYSCTL_INT(_kern, OID_AUTO, ncallout, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &ncallout, 0,
  104     "Number of entries in callwheel and size of timeout() preallocation");
  105 
  106 #ifdef  RSS
  107 static int pin_default_swi = 1;
  108 static int pin_pcpu_swi = 1;
  109 #else
  110 static int pin_default_swi = 0;
  111 static int pin_pcpu_swi = 0;
  112 #endif
  113 
  114 SYSCTL_INT(_kern, OID_AUTO, pin_default_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_default_swi,
  115     0, "Pin the default (non-per-cpu) swi (shared with PCPU 0 swi)");
  116 SYSCTL_INT(_kern, OID_AUTO, pin_pcpu_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_pcpu_swi,
  117     0, "Pin the per-CPU swis (except PCPU 0, which is also default");
  118 
  119 /*
  120  * TODO:
  121  *      allocate more timeout table slots when table overflows.
  122  */
  123 u_int callwheelsize, callwheelmask;
  124 
  125 /*
  126  * The callout cpu exec entities represent informations necessary for
  127  * describing the state of callouts currently running on the CPU and the ones
  128  * necessary for migrating callouts to the new callout cpu. In particular,
  129  * the first entry of the array cc_exec_entity holds informations for callout
  130  * running in SWI thread context, while the second one holds informations
  131  * for callout running directly from hardware interrupt context.
  132  * The cached informations are very important for deferring migration when
  133  * the migrating callout is already running.
  134  */
  135 struct cc_exec {
  136         struct callout          *cc_curr;
  137         void                    (*cc_drain)(void *);
  138 #ifdef SMP
  139         void                    (*ce_migration_func)(void *);
  140         void                    *ce_migration_arg;
  141         int                     ce_migration_cpu;
  142         sbintime_t              ce_migration_time;
  143         sbintime_t              ce_migration_prec;
  144 #endif
  145         bool                    cc_cancel;
  146         bool                    cc_waiting;
  147 };
  148 
  149 /*
  150  * There is one struct callout_cpu per cpu, holding all relevant
  151  * state for the callout processing thread on the individual CPU.
  152  */
  153 struct callout_cpu {
  154         struct mtx_padalign     cc_lock;
  155         struct cc_exec          cc_exec_entity[2];
  156         struct callout          *cc_next;
  157         struct callout          *cc_callout;
  158         struct callout_list     *cc_callwheel;
  159         struct callout_tailq    cc_expireq;
  160         struct callout_slist    cc_callfree;
  161         sbintime_t              cc_firstevent;
  162         sbintime_t              cc_lastscan;
  163         void                    *cc_cookie;
  164         u_int                   cc_bucket;
  165         u_int                   cc_inited;
  166         char                    cc_ktr_event_name[20];
  167 };
  168 
  169 #define callout_migrating(c)    ((c)->c_iflags & CALLOUT_DFRMIGRATION)
  170 
  171 #define cc_exec_curr(cc, dir)           cc->cc_exec_entity[dir].cc_curr
  172 #define cc_exec_drain(cc, dir)          cc->cc_exec_entity[dir].cc_drain
  173 #define cc_exec_next(cc)                cc->cc_next
  174 #define cc_exec_cancel(cc, dir)         cc->cc_exec_entity[dir].cc_cancel
  175 #define cc_exec_waiting(cc, dir)        cc->cc_exec_entity[dir].cc_waiting
  176 #ifdef SMP
  177 #define cc_migration_func(cc, dir)      cc->cc_exec_entity[dir].ce_migration_func
  178 #define cc_migration_arg(cc, dir)       cc->cc_exec_entity[dir].ce_migration_arg
  179 #define cc_migration_cpu(cc, dir)       cc->cc_exec_entity[dir].ce_migration_cpu
  180 #define cc_migration_time(cc, dir)      cc->cc_exec_entity[dir].ce_migration_time
  181 #define cc_migration_prec(cc, dir)      cc->cc_exec_entity[dir].ce_migration_prec
  182 
  183 struct callout_cpu cc_cpu[MAXCPU];
  184 #define CPUBLOCK        MAXCPU
  185 #define CC_CPU(cpu)     (&cc_cpu[(cpu)])
  186 #define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
  187 #else
  188 struct callout_cpu cc_cpu;
  189 #define CC_CPU(cpu)     &cc_cpu
  190 #define CC_SELF()       &cc_cpu
  191 #endif
  192 #define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
  193 #define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)
  194 #define CC_LOCK_ASSERT(cc)      mtx_assert(&(cc)->cc_lock, MA_OWNED)
  195 
  196 static int timeout_cpu;
  197 
  198 static void     callout_cpu_init(struct callout_cpu *cc, int cpu);
  199 static void     softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  200 #ifdef CALLOUT_PROFILING
  201                     int *mpcalls, int *lockcalls, int *gcalls,
  202 #endif
  203                     int direct);
  204 
  205 static MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
  206 
  207 /**
  208  * Locked by cc_lock:
  209  *   cc_curr         - If a callout is in progress, it is cc_curr.
  210  *                     If cc_curr is non-NULL, threads waiting in
  211  *                     callout_drain() will be woken up as soon as the
  212  *                     relevant callout completes.
  213  *   cc_cancel       - Changing to 1 with both callout_lock and cc_lock held
  214  *                     guarantees that the current callout will not run.
  215  *                     The softclock() function sets this to 0 before it
  216  *                     drops callout_lock to acquire c_lock, and it calls
  217  *                     the handler only if curr_cancelled is still 0 after
  218  *                     cc_lock is successfully acquired.
  219  *   cc_waiting      - If a thread is waiting in callout_drain(), then
  220  *                     callout_wait is nonzero.  Set only when
  221  *                     cc_curr is non-NULL.
  222  */
  223 
  224 /*
  225  * Resets the execution entity tied to a specific callout cpu.
  226  */
  227 static void
  228 cc_cce_cleanup(struct callout_cpu *cc, int direct)
  229 {
  230 
  231         cc_exec_curr(cc, direct) = NULL;
  232         cc_exec_cancel(cc, direct) = false;
  233         cc_exec_waiting(cc, direct) = false;
  234 #ifdef SMP
  235         cc_migration_cpu(cc, direct) = CPUBLOCK;
  236         cc_migration_time(cc, direct) = 0;
  237         cc_migration_prec(cc, direct) = 0;
  238         cc_migration_func(cc, direct) = NULL;
  239         cc_migration_arg(cc, direct) = NULL;
  240 #endif
  241 }
  242 
  243 /*
  244  * Checks if migration is requested by a specific callout cpu.
  245  */
  246 static int
  247 cc_cce_migrating(struct callout_cpu *cc, int direct)
  248 {
  249 
  250 #ifdef SMP
  251         return (cc_migration_cpu(cc, direct) != CPUBLOCK);
  252 #else
  253         return (0);
  254 #endif
  255 }
  256 
  257 /*
  258  * Kernel low level callwheel initialization
  259  * called on cpu0 during kernel startup.
  260  */
  261 static void
  262 callout_callwheel_init(void *dummy)
  263 {
  264         struct callout_cpu *cc;
  265 
  266         /*
  267          * Calculate the size of the callout wheel and the preallocated
  268          * timeout() structures.
  269          * XXX: Clip callout to result of previous function of maxusers
  270          * maximum 384.  This is still huge, but acceptable.
  271          */
  272         memset(CC_CPU(0), 0, sizeof(cc_cpu));
  273         ncallout = imin(16 + maxproc + maxfiles, 18508);
  274         TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
  275 
  276         /*
  277          * Calculate callout wheel size, should be next power of two higher
  278          * than 'ncallout'.
  279          */
  280         callwheelsize = 1 << fls(ncallout);
  281         callwheelmask = callwheelsize - 1;
  282 
  283         /*
  284          * Fetch whether we're pinning the swi's or not.
  285          */
  286         TUNABLE_INT_FETCH("kern.pin_default_swi", &pin_default_swi);
  287         TUNABLE_INT_FETCH("kern.pin_pcpu_swi", &pin_pcpu_swi);
  288 
  289         /*
  290          * Only cpu0 handles timeout(9) and receives a preallocation.
  291          *
  292          * XXX: Once all timeout(9) consumers are converted this can
  293          * be removed.
  294          */
  295         timeout_cpu = PCPU_GET(cpuid);
  296         cc = CC_CPU(timeout_cpu);
  297         cc->cc_callout = malloc(ncallout * sizeof(struct callout),
  298             M_CALLOUT, M_WAITOK);
  299         callout_cpu_init(cc, timeout_cpu);
  300 }
  301 SYSINIT(callwheel_init, SI_SUB_CPU, SI_ORDER_ANY, callout_callwheel_init, NULL);
  302 
  303 /*
  304  * Initialize the per-cpu callout structures.
  305  */
  306 static void
  307 callout_cpu_init(struct callout_cpu *cc, int cpu)
  308 {
  309         struct callout *c;
  310         int i;
  311 
  312         mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
  313         SLIST_INIT(&cc->cc_callfree);
  314         cc->cc_inited = 1;
  315         cc->cc_callwheel = malloc(sizeof(struct callout_list) * callwheelsize,
  316             M_CALLOUT, M_WAITOK);
  317         for (i = 0; i < callwheelsize; i++)
  318                 LIST_INIT(&cc->cc_callwheel[i]);
  319         TAILQ_INIT(&cc->cc_expireq);
  320         cc->cc_firstevent = SBT_MAX;
  321         for (i = 0; i < 2; i++)
  322                 cc_cce_cleanup(cc, i);
  323         snprintf(cc->cc_ktr_event_name, sizeof(cc->cc_ktr_event_name),
  324             "callwheel cpu %d", cpu);
  325         if (cc->cc_callout == NULL)     /* Only cpu0 handles timeout(9) */
  326                 return;
  327         for (i = 0; i < ncallout; i++) {
  328                 c = &cc->cc_callout[i];
  329                 callout_init(c, 0);
  330                 c->c_iflags = CALLOUT_LOCAL_ALLOC;
  331                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  332         }
  333 }
  334 
  335 #ifdef SMP
  336 /*
  337  * Switches the cpu tied to a specific callout.
  338  * The function expects a locked incoming callout cpu and returns with
  339  * locked outcoming callout cpu.
  340  */
  341 static struct callout_cpu *
  342 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
  343 {
  344         struct callout_cpu *new_cc;
  345 
  346         MPASS(c != NULL && cc != NULL);
  347         CC_LOCK_ASSERT(cc);
  348 
  349         /*
  350          * Avoid interrupts and preemption firing after the callout cpu
  351          * is blocked in order to avoid deadlocks as the new thread
  352          * may be willing to acquire the callout cpu lock.
  353          */
  354         c->c_cpu = CPUBLOCK;
  355         spinlock_enter();
  356         CC_UNLOCK(cc);
  357         new_cc = CC_CPU(new_cpu);
  358         CC_LOCK(new_cc);
  359         spinlock_exit();
  360         c->c_cpu = new_cpu;
  361         return (new_cc);
  362 }
  363 #endif
  364 
  365 /*
  366  * Start standard softclock thread.
  367  */
  368 static void
  369 start_softclock(void *dummy)
  370 {
  371         struct callout_cpu *cc;
  372         char name[MAXCOMLEN];
  373 #ifdef SMP
  374         int cpu;
  375         struct intr_event *ie;
  376 #endif
  377 
  378         cc = CC_CPU(timeout_cpu);
  379         snprintf(name, sizeof(name), "clock (%d)", timeout_cpu);
  380         if (swi_add(&clk_intr_event, name, softclock, cc, SWI_CLOCK,
  381             INTR_MPSAFE, &cc->cc_cookie))
  382                 panic("died while creating standard software ithreads");
  383         if (pin_default_swi &&
  384             (intr_event_bind(clk_intr_event, timeout_cpu) != 0)) {
  385                 printf("%s: timeout clock couldn't be pinned to cpu %d\n",
  386                     __func__,
  387                     timeout_cpu);
  388         }
  389 
  390 #ifdef SMP
  391         CPU_FOREACH(cpu) {
  392                 if (cpu == timeout_cpu)
  393                         continue;
  394                 cc = CC_CPU(cpu);
  395                 cc->cc_callout = NULL;  /* Only cpu0 handles timeout(9). */
  396                 callout_cpu_init(cc, cpu);
  397                 snprintf(name, sizeof(name), "clock (%d)", cpu);
  398                 ie = NULL;
  399                 if (swi_add(&ie, name, softclock, cc, SWI_CLOCK,
  400                     INTR_MPSAFE, &cc->cc_cookie))
  401                         panic("died while creating standard software ithreads");
  402                 if (pin_pcpu_swi && (intr_event_bind(ie, cpu) != 0)) {
  403                         printf("%s: per-cpu clock couldn't be pinned to "
  404                             "cpu %d\n",
  405                             __func__,
  406                             cpu);
  407                 }
  408         }
  409 #endif
  410 }
  411 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
  412 
  413 #define CC_HASH_SHIFT   8
  414 
  415 static inline u_int
  416 callout_hash(sbintime_t sbt)
  417 {
  418 
  419         return (sbt >> (32 - CC_HASH_SHIFT));
  420 }
  421 
  422 static inline u_int
  423 callout_get_bucket(sbintime_t sbt)
  424 {
  425 
  426         return (callout_hash(sbt) & callwheelmask);
  427 }
  428 
  429 void
  430 callout_process(sbintime_t now)
  431 {
  432         struct callout *tmp, *tmpn;
  433         struct callout_cpu *cc;
  434         struct callout_list *sc;
  435         sbintime_t first, last, max, tmp_max;
  436         uint32_t lookahead;
  437         u_int firstb, lastb, nowb;
  438 #ifdef CALLOUT_PROFILING
  439         int depth_dir = 0, mpcalls_dir = 0, lockcalls_dir = 0;
  440 #endif
  441 
  442         cc = CC_SELF();
  443         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  444 
  445         /* Compute the buckets of the last scan and present times. */
  446         firstb = callout_hash(cc->cc_lastscan);
  447         cc->cc_lastscan = now;
  448         nowb = callout_hash(now);
  449 
  450         /* Compute the last bucket and minimum time of the bucket after it. */
  451         if (nowb == firstb)
  452                 lookahead = (SBT_1S / 16);
  453         else if (nowb - firstb == 1)
  454                 lookahead = (SBT_1S / 8);
  455         else
  456                 lookahead = (SBT_1S / 2);
  457         first = last = now;
  458         first += (lookahead / 2);
  459         last += lookahead;
  460         last &= (0xffffffffffffffffLLU << (32 - CC_HASH_SHIFT));
  461         lastb = callout_hash(last) - 1;
  462         max = last;
  463 
  464         /*
  465          * Check if we wrapped around the entire wheel from the last scan.
  466          * In case, we need to scan entirely the wheel for pending callouts.
  467          */
  468         if (lastb - firstb >= callwheelsize) {
  469                 lastb = firstb + callwheelsize - 1;
  470                 if (nowb - firstb >= callwheelsize)
  471                         nowb = lastb;
  472         }
  473 
  474         /* Iterate callwheel from firstb to nowb and then up to lastb. */
  475         do {
  476                 sc = &cc->cc_callwheel[firstb & callwheelmask];
  477                 tmp = LIST_FIRST(sc);
  478                 while (tmp != NULL) {
  479                         /* Run the callout if present time within allowed. */
  480                         if (tmp->c_time <= now) {
  481                                 /*
  482                                  * Consumer told us the callout may be run
  483                                  * directly from hardware interrupt context.
  484                                  */
  485                                 if (tmp->c_iflags & CALLOUT_DIRECT) {
  486 #ifdef CALLOUT_PROFILING
  487                                         ++depth_dir;
  488 #endif
  489                                         cc_exec_next(cc) =
  490                                             LIST_NEXT(tmp, c_links.le);
  491                                         cc->cc_bucket = firstb & callwheelmask;
  492                                         LIST_REMOVE(tmp, c_links.le);
  493                                         softclock_call_cc(tmp, cc,
  494 #ifdef CALLOUT_PROFILING
  495                                             &mpcalls_dir, &lockcalls_dir, NULL,
  496 #endif
  497                                             1);
  498                                         tmp = cc_exec_next(cc);
  499                                         cc_exec_next(cc) = NULL;
  500                                 } else {
  501                                         tmpn = LIST_NEXT(tmp, c_links.le);
  502                                         LIST_REMOVE(tmp, c_links.le);
  503                                         TAILQ_INSERT_TAIL(&cc->cc_expireq,
  504                                             tmp, c_links.tqe);
  505                                         tmp->c_iflags |= CALLOUT_PROCESSED;
  506                                         tmp = tmpn;
  507                                 }
  508                                 continue;
  509                         }
  510                         /* Skip events from distant future. */
  511                         if (tmp->c_time >= max)
  512                                 goto next;
  513                         /*
  514                          * Event minimal time is bigger than present maximal
  515                          * time, so it cannot be aggregated.
  516                          */
  517                         if (tmp->c_time > last) {
  518                                 lastb = nowb;
  519                                 goto next;
  520                         }
  521                         /* Update first and last time, respecting this event. */
  522                         if (tmp->c_time < first)
  523                                 first = tmp->c_time;
  524                         tmp_max = tmp->c_time + tmp->c_precision;
  525                         if (tmp_max < last)
  526                                 last = tmp_max;
  527 next:
  528                         tmp = LIST_NEXT(tmp, c_links.le);
  529                 }
  530                 /* Proceed with the next bucket. */
  531                 firstb++;
  532                 /*
  533                  * Stop if we looked after present time and found
  534                  * some event we can't execute at now.
  535                  * Stop if we looked far enough into the future.
  536                  */
  537         } while (((int)(firstb - lastb)) <= 0);
  538         cc->cc_firstevent = last;
  539 #ifndef NO_EVENTTIMERS
  540         cpu_new_callout(curcpu, last, first);
  541 #endif
  542 #ifdef CALLOUT_PROFILING
  543         avg_depth_dir += (depth_dir * 1000 - avg_depth_dir) >> 8;
  544         avg_mpcalls_dir += (mpcalls_dir * 1000 - avg_mpcalls_dir) >> 8;
  545         avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
  546 #endif
  547         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  548         /*
  549          * swi_sched acquires the thread lock, so we don't want to call it
  550          * with cc_lock held; incorrect locking order.
  551          */
  552         if (!TAILQ_EMPTY(&cc->cc_expireq))
  553                 swi_sched(cc->cc_cookie, 0);
  554 }
  555 
  556 static struct callout_cpu *
  557 callout_lock(struct callout *c)
  558 {
  559         struct callout_cpu *cc;
  560         int cpu;
  561 
  562         for (;;) {
  563                 cpu = c->c_cpu;
  564 #ifdef SMP
  565                 if (cpu == CPUBLOCK) {
  566                         while (c->c_cpu == CPUBLOCK)
  567                                 cpu_spinwait();
  568                         continue;
  569                 }
  570 #endif
  571                 cc = CC_CPU(cpu);
  572                 CC_LOCK(cc);
  573                 if (cpu == c->c_cpu)
  574                         break;
  575                 CC_UNLOCK(cc);
  576         }
  577         return (cc);
  578 }
  579 
  580 static void
  581 callout_cc_add(struct callout *c, struct callout_cpu *cc,
  582     sbintime_t sbt, sbintime_t precision, void (*func)(void *),
  583     void *arg, int cpu, int flags)
  584 {
  585         int bucket;
  586 
  587         CC_LOCK_ASSERT(cc);
  588         if (sbt < cc->cc_lastscan)
  589                 sbt = cc->cc_lastscan;
  590         c->c_arg = arg;
  591         c->c_iflags |= CALLOUT_PENDING;
  592         c->c_iflags &= ~CALLOUT_PROCESSED;
  593         c->c_flags |= CALLOUT_ACTIVE;
  594         if (flags & C_DIRECT_EXEC)
  595                 c->c_iflags |= CALLOUT_DIRECT;
  596         c->c_func = func;
  597         c->c_time = sbt;
  598         c->c_precision = precision;
  599         bucket = callout_get_bucket(c->c_time);
  600         CTR3(KTR_CALLOUT, "precision set for %p: %d.%08x",
  601             c, (int)(c->c_precision >> 32),
  602             (u_int)(c->c_precision & 0xffffffff));
  603         LIST_INSERT_HEAD(&cc->cc_callwheel[bucket], c, c_links.le);
  604         if (cc->cc_bucket == bucket)
  605                 cc_exec_next(cc) = c;
  606 #ifndef NO_EVENTTIMERS
  607         /*
  608          * Inform the eventtimers(4) subsystem there's a new callout
  609          * that has been inserted, but only if really required.
  610          */
  611         if (SBT_MAX - c->c_time < c->c_precision)
  612                 c->c_precision = SBT_MAX - c->c_time;
  613         sbt = c->c_time + c->c_precision;
  614         if (sbt < cc->cc_firstevent) {
  615                 cc->cc_firstevent = sbt;
  616                 cpu_new_callout(cpu, sbt, c->c_time);
  617         }
  618 #endif
  619 }
  620 
  621 static void
  622 callout_cc_del(struct callout *c, struct callout_cpu *cc)
  623 {
  624 
  625         if ((c->c_iflags & CALLOUT_LOCAL_ALLOC) == 0)
  626                 return;
  627         c->c_func = NULL;
  628         SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  629 }
  630 
  631 static void
  632 softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  633 #ifdef CALLOUT_PROFILING
  634     int *mpcalls, int *lockcalls, int *gcalls,
  635 #endif
  636     int direct)
  637 {
  638         struct rm_priotracker tracker;
  639         void (*c_func)(void *);
  640         void *c_arg;
  641         struct lock_class *class;
  642         struct lock_object *c_lock;
  643         uintptr_t lock_status;
  644         int c_iflags;
  645 #ifdef SMP
  646         struct callout_cpu *new_cc;
  647         void (*new_func)(void *);
  648         void *new_arg;
  649         int flags, new_cpu;
  650         sbintime_t new_prec, new_time;
  651 #endif
  652 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING) 
  653         sbintime_t sbt1, sbt2;
  654         struct timespec ts2;
  655         static sbintime_t maxdt = 2 * SBT_1MS;  /* 2 msec */
  656         static timeout_t *lastfunc;
  657 #endif
  658 
  659         KASSERT((c->c_iflags & CALLOUT_PENDING) == CALLOUT_PENDING,
  660             ("softclock_call_cc: pend %p %x", c, c->c_iflags));
  661         KASSERT((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE,
  662             ("softclock_call_cc: act %p %x", c, c->c_flags));
  663         class = (c->c_lock != NULL) ? LOCK_CLASS(c->c_lock) : NULL;
  664         lock_status = 0;
  665         if (c->c_flags & CALLOUT_SHAREDLOCK) {
  666                 if (class == &lock_class_rm)
  667                         lock_status = (uintptr_t)&tracker;
  668                 else
  669                         lock_status = 1;
  670         }
  671         c_lock = c->c_lock;
  672         c_func = c->c_func;
  673         c_arg = c->c_arg;
  674         c_iflags = c->c_iflags;
  675         if (c->c_iflags & CALLOUT_LOCAL_ALLOC)
  676                 c->c_iflags = CALLOUT_LOCAL_ALLOC;
  677         else
  678                 c->c_iflags &= ~CALLOUT_PENDING;
  679         
  680         cc_exec_curr(cc, direct) = c;
  681         cc_exec_cancel(cc, direct) = false;
  682         cc_exec_drain(cc, direct) = NULL;
  683         CC_UNLOCK(cc);
  684         if (c_lock != NULL) {
  685                 class->lc_lock(c_lock, lock_status);
  686                 /*
  687                  * The callout may have been cancelled
  688                  * while we switched locks.
  689                  */
  690                 if (cc_exec_cancel(cc, direct)) {
  691                         class->lc_unlock(c_lock);
  692                         goto skip;
  693                 }
  694                 /* The callout cannot be stopped now. */
  695                 cc_exec_cancel(cc, direct) = true;
  696                 if (c_lock == &Giant.lock_object) {
  697 #ifdef CALLOUT_PROFILING
  698                         (*gcalls)++;
  699 #endif
  700                         CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
  701                             c, c_func, c_arg);
  702                 } else {
  703 #ifdef CALLOUT_PROFILING
  704                         (*lockcalls)++;
  705 #endif
  706                         CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
  707                             c, c_func, c_arg);
  708                 }
  709         } else {
  710 #ifdef CALLOUT_PROFILING
  711                 (*mpcalls)++;
  712 #endif
  713                 CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
  714                     c, c_func, c_arg);
  715         }
  716         KTR_STATE3(KTR_SCHED, "callout", cc->cc_ktr_event_name, "running",
  717             "func:%p", c_func, "arg:%p", c_arg, "direct:%d", direct);
  718 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  719         sbt1 = sbinuptime();
  720 #endif
  721         THREAD_NO_SLEEPING();
  722         SDT_PROBE1(callout_execute, , , callout__start, c);
  723         c_func(c_arg);
  724         SDT_PROBE1(callout_execute, , , callout__end, c);
  725         THREAD_SLEEPING_OK();
  726 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  727         sbt2 = sbinuptime();
  728         sbt2 -= sbt1;
  729         if (sbt2 > maxdt) {
  730                 if (lastfunc != c_func || sbt2 > maxdt * 2) {
  731                         ts2 = sbttots(sbt2);
  732                         printf(
  733                 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  734                             c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
  735                 }
  736                 maxdt = sbt2;
  737                 lastfunc = c_func;
  738         }
  739 #endif
  740         KTR_STATE0(KTR_SCHED, "callout", cc->cc_ktr_event_name, "idle");
  741         CTR1(KTR_CALLOUT, "callout %p finished", c);
  742         if ((c_iflags & CALLOUT_RETURNUNLOCKED) == 0)
  743                 class->lc_unlock(c_lock);
  744 skip:
  745         CC_LOCK(cc);
  746         KASSERT(cc_exec_curr(cc, direct) == c, ("mishandled cc_curr"));
  747         cc_exec_curr(cc, direct) = NULL;
  748         if (cc_exec_drain(cc, direct)) {
  749                 void (*drain)(void *);
  750                 
  751                 drain = cc_exec_drain(cc, direct);
  752                 cc_exec_drain(cc, direct) = NULL;
  753                 CC_UNLOCK(cc);
  754                 drain(c_arg);
  755                 CC_LOCK(cc);
  756         }
  757         if (cc_exec_waiting(cc, direct)) {
  758                 /*
  759                  * There is someone waiting for the
  760                  * callout to complete.
  761                  * If the callout was scheduled for
  762                  * migration just cancel it.
  763                  */
  764                 if (cc_cce_migrating(cc, direct)) {
  765                         cc_cce_cleanup(cc, direct);
  766 
  767                         /*
  768                          * It should be assert here that the callout is not
  769                          * destroyed but that is not easy.
  770                          */
  771                         c->c_iflags &= ~CALLOUT_DFRMIGRATION;
  772                 }
  773                 cc_exec_waiting(cc, direct) = false;
  774                 CC_UNLOCK(cc);
  775                 wakeup(&cc_exec_waiting(cc, direct));
  776                 CC_LOCK(cc);
  777         } else if (cc_cce_migrating(cc, direct)) {
  778                 KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0,
  779                     ("Migrating legacy callout %p", c));
  780 #ifdef SMP
  781                 /*
  782                  * If the callout was scheduled for
  783                  * migration just perform it now.
  784                  */
  785                 new_cpu = cc_migration_cpu(cc, direct);
  786                 new_time = cc_migration_time(cc, direct);
  787                 new_prec = cc_migration_prec(cc, direct);
  788                 new_func = cc_migration_func(cc, direct);
  789                 new_arg = cc_migration_arg(cc, direct);
  790                 cc_cce_cleanup(cc, direct);
  791 
  792                 /*
  793                  * It should be assert here that the callout is not destroyed
  794                  * but that is not easy.
  795                  *
  796                  * As first thing, handle deferred callout stops.
  797                  */
  798                 if (!callout_migrating(c)) {
  799                         CTR3(KTR_CALLOUT,
  800                              "deferred cancelled %p func %p arg %p",
  801                              c, new_func, new_arg);
  802                         callout_cc_del(c, cc);
  803                         return;
  804                 }
  805                 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
  806 
  807                 new_cc = callout_cpu_switch(c, cc, new_cpu);
  808                 flags = (direct) ? C_DIRECT_EXEC : 0;
  809                 callout_cc_add(c, new_cc, new_time, new_prec, new_func,
  810                     new_arg, new_cpu, flags);
  811                 CC_UNLOCK(new_cc);
  812                 CC_LOCK(cc);
  813 #else
  814                 panic("migration should not happen");
  815 #endif
  816         }
  817         /*
  818          * If the current callout is locally allocated (from
  819          * timeout(9)) then put it on the freelist.
  820          *
  821          * Note: we need to check the cached copy of c_iflags because
  822          * if it was not local, then it's not safe to deref the
  823          * callout pointer.
  824          */
  825         KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0 ||
  826             c->c_iflags == CALLOUT_LOCAL_ALLOC,
  827             ("corrupted callout"));
  828         if (c_iflags & CALLOUT_LOCAL_ALLOC)
  829                 callout_cc_del(c, cc);
  830 }
  831 
  832 /*
  833  * The callout mechanism is based on the work of Adam M. Costello and
  834  * George Varghese, published in a technical report entitled "Redesigning
  835  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  836  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  837  * used in this implementation was published by G. Varghese and T. Lauck in
  838  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  839  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  840  * the 11th ACM Annual Symposium on Operating Systems Principles,
  841  * Austin, Texas Nov 1987.
  842  */
  843 
  844 /*
  845  * Software (low priority) clock interrupt.
  846  * Run periodic events from timeout queue.
  847  */
  848 void
  849 softclock(void *arg)
  850 {
  851         struct callout_cpu *cc;
  852         struct callout *c;
  853 #ifdef CALLOUT_PROFILING
  854         int depth = 0, gcalls = 0, lockcalls = 0, mpcalls = 0;
  855 #endif
  856 
  857         cc = (struct callout_cpu *)arg;
  858         CC_LOCK(cc);
  859         while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
  860                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
  861                 softclock_call_cc(c, cc,
  862 #ifdef CALLOUT_PROFILING
  863                     &mpcalls, &lockcalls, &gcalls,
  864 #endif
  865                     0);
  866 #ifdef CALLOUT_PROFILING
  867                 ++depth;
  868 #endif
  869         }
  870 #ifdef CALLOUT_PROFILING
  871         avg_depth += (depth * 1000 - avg_depth) >> 8;
  872         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  873         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  874         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  875 #endif
  876         CC_UNLOCK(cc);
  877 }
  878 
  879 /*
  880  * timeout --
  881  *      Execute a function after a specified length of time.
  882  *
  883  * untimeout --
  884  *      Cancel previous timeout function call.
  885  *
  886  * callout_handle_init --
  887  *      Initialize a handle so that using it with untimeout is benign.
  888  *
  889  *      See AT&T BCI Driver Reference Manual for specification.  This
  890  *      implementation differs from that one in that although an
  891  *      identification value is returned from timeout, the original
  892  *      arguments to timeout as well as the identifier are used to
  893  *      identify entries for untimeout.
  894  */
  895 struct callout_handle
  896 timeout(timeout_t *ftn, void *arg, int to_ticks)
  897 {
  898         struct callout_cpu *cc;
  899         struct callout *new;
  900         struct callout_handle handle;
  901 
  902         cc = CC_CPU(timeout_cpu);
  903         CC_LOCK(cc);
  904         /* Fill in the next free callout structure. */
  905         new = SLIST_FIRST(&cc->cc_callfree);
  906         if (new == NULL)
  907                 /* XXX Attempt to malloc first */
  908                 panic("timeout table full");
  909         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  910         callout_reset(new, to_ticks, ftn, arg);
  911         handle.callout = new;
  912         CC_UNLOCK(cc);
  913 
  914         return (handle);
  915 }
  916 
  917 void
  918 untimeout(timeout_t *ftn, void *arg, struct callout_handle handle)
  919 {
  920         struct callout_cpu *cc;
  921 
  922         /*
  923          * Check for a handle that was initialized
  924          * by callout_handle_init, but never used
  925          * for a real timeout.
  926          */
  927         if (handle.callout == NULL)
  928                 return;
  929 
  930         cc = callout_lock(handle.callout);
  931         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  932                 callout_stop(handle.callout);
  933         CC_UNLOCK(cc);
  934 }
  935 
  936 void
  937 callout_handle_init(struct callout_handle *handle)
  938 {
  939         handle->callout = NULL;
  940 }
  941 
  942 /*
  943  * New interface; clients allocate their own callout structures.
  944  *
  945  * callout_reset() - establish or change a timeout
  946  * callout_stop() - disestablish a timeout
  947  * callout_init() - initialize a callout structure so that it can
  948  *      safely be passed to callout_reset() and callout_stop()
  949  *
  950  * <sys/callout.h> defines three convenience macros:
  951  *
  952  * callout_active() - returns truth if callout has not been stopped,
  953  *      drained, or deactivated since the last time the callout was
  954  *      reset.
  955  * callout_pending() - returns truth if callout is still waiting for timeout
  956  * callout_deactivate() - marks the callout as having been serviced
  957  */
  958 int
  959 callout_reset_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t precision,
  960     void (*ftn)(void *), void *arg, int cpu, int flags)
  961 {
  962         sbintime_t to_sbt, pr;
  963         struct callout_cpu *cc;
  964         int cancelled, direct;
  965         int ignore_cpu=0;
  966 
  967         cancelled = 0;
  968         if (cpu == -1) {
  969                 ignore_cpu = 1;
  970         } else if ((cpu >= MAXCPU) ||
  971                    ((CC_CPU(cpu))->cc_inited == 0)) {
  972                 /* Invalid CPU spec */
  973                 panic("Invalid CPU in callout %d", cpu);
  974         }
  975         if (flags & C_ABSOLUTE) {
  976                 to_sbt = sbt;
  977         } else {
  978                 if ((flags & C_HARDCLOCK) && (sbt < tick_sbt))
  979                         sbt = tick_sbt;
  980                 if ((flags & C_HARDCLOCK) ||
  981 #ifdef NO_EVENTTIMERS
  982                     sbt >= sbt_timethreshold) {
  983                         to_sbt = getsbinuptime();
  984 
  985                         /* Add safety belt for the case of hz > 1000. */
  986                         to_sbt += tc_tick_sbt - tick_sbt;
  987 #else
  988                     sbt >= sbt_tickthreshold) {
  989                         /*
  990                          * Obtain the time of the last hardclock() call on
  991                          * this CPU directly from the kern_clocksource.c.
  992                          * This value is per-CPU, but it is equal for all
  993                          * active ones.
  994                          */
  995 #ifdef __LP64__
  996                         to_sbt = DPCPU_GET(hardclocktime);
  997 #else
  998                         spinlock_enter();
  999                         to_sbt = DPCPU_GET(hardclocktime);
 1000                         spinlock_exit();
 1001 #endif
 1002 #endif
 1003                         if ((flags & C_HARDCLOCK) == 0)
 1004                                 to_sbt += tick_sbt;
 1005                 } else
 1006                         to_sbt = sbinuptime();
 1007                 if (SBT_MAX - to_sbt < sbt)
 1008                         to_sbt = SBT_MAX;
 1009                 else
 1010                         to_sbt += sbt;
 1011                 pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
 1012                     sbt >> C_PRELGET(flags));
 1013                 if (pr > precision)
 1014                         precision = pr;
 1015         }
 1016         /* 
 1017          * This flag used to be added by callout_cc_add, but the
 1018          * first time you call this we could end up with the
 1019          * wrong direct flag if we don't do it before we add.
 1020          */
 1021         if (flags & C_DIRECT_EXEC) {
 1022                 direct = 1;
 1023         } else {
 1024                 direct = 0;
 1025         }
 1026         KASSERT(!direct || c->c_lock == NULL,
 1027             ("%s: direct callout %p has lock", __func__, c));
 1028         cc = callout_lock(c);
 1029         /*
 1030          * Don't allow migration of pre-allocated callouts lest they
 1031          * become unbalanced or handle the case where the user does
 1032          * not care. 
 1033          */
 1034         if ((c->c_iflags & CALLOUT_LOCAL_ALLOC) ||
 1035             ignore_cpu) {
 1036                 cpu = c->c_cpu;
 1037         }
 1038 
 1039         if (cc_exec_curr(cc, direct) == c) {
 1040                 /*
 1041                  * We're being asked to reschedule a callout which is
 1042                  * currently in progress.  If there is a lock then we
 1043                  * can cancel the callout if it has not really started.
 1044                  */
 1045                 if (c->c_lock != NULL && !cc_exec_cancel(cc, direct))
 1046                         cancelled = cc_exec_cancel(cc, direct) = true;
 1047                 if (cc_exec_waiting(cc, direct)) {
 1048                         /*
 1049                          * Someone has called callout_drain to kill this
 1050                          * callout.  Don't reschedule.
 1051                          */
 1052                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
 1053                             cancelled ? "cancelled" : "failed to cancel",
 1054                             c, c->c_func, c->c_arg);
 1055                         CC_UNLOCK(cc);
 1056                         return (cancelled);
 1057                 }
 1058 #ifdef SMP
 1059                 if (callout_migrating(c)) {
 1060                         /* 
 1061                          * This only occurs when a second callout_reset_sbt_on
 1062                          * is made after a previous one moved it into
 1063                          * deferred migration (below). Note we do *not* change
 1064                          * the prev_cpu even though the previous target may
 1065                          * be different.
 1066                          */
 1067                         cc_migration_cpu(cc, direct) = cpu;
 1068                         cc_migration_time(cc, direct) = to_sbt;
 1069                         cc_migration_prec(cc, direct) = precision;
 1070                         cc_migration_func(cc, direct) = ftn;
 1071                         cc_migration_arg(cc, direct) = arg;
 1072                         cancelled = 1;
 1073                         CC_UNLOCK(cc);
 1074                         return (cancelled);
 1075                 }
 1076 #endif
 1077         }
 1078         if (c->c_iflags & CALLOUT_PENDING) {
 1079                 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
 1080                         if (cc_exec_next(cc) == c)
 1081                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1082                         LIST_REMOVE(c, c_links.le);
 1083                 } else {
 1084                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1085                 }
 1086                 cancelled = 1;
 1087                 c->c_iflags &= ~ CALLOUT_PENDING;
 1088                 c->c_flags &= ~ CALLOUT_ACTIVE;
 1089         }
 1090 
 1091 #ifdef SMP
 1092         /*
 1093          * If the callout must migrate try to perform it immediately.
 1094          * If the callout is currently running, just defer the migration
 1095          * to a more appropriate moment.
 1096          */
 1097         if (c->c_cpu != cpu) {
 1098                 if (cc_exec_curr(cc, direct) == c) {
 1099                         /* 
 1100                          * Pending will have been removed since we are
 1101                          * actually executing the callout on another
 1102                          * CPU. That callout should be waiting on the
 1103                          * lock the caller holds. If we set both
 1104                          * active/and/pending after we return and the
 1105                          * lock on the executing callout proceeds, it
 1106                          * will then see pending is true and return.
 1107                          * At the return from the actual callout execution
 1108                          * the migration will occur in softclock_call_cc
 1109                          * and this new callout will be placed on the 
 1110                          * new CPU via a call to callout_cpu_switch() which
 1111                          * will get the lock on the right CPU followed
 1112                          * by a call callout_cc_add() which will add it there.
 1113                          * (see above in softclock_call_cc()).
 1114                          */
 1115                         cc_migration_cpu(cc, direct) = cpu;
 1116                         cc_migration_time(cc, direct) = to_sbt;
 1117                         cc_migration_prec(cc, direct) = precision;
 1118                         cc_migration_func(cc, direct) = ftn;
 1119                         cc_migration_arg(cc, direct) = arg;
 1120                         c->c_iflags |= (CALLOUT_DFRMIGRATION | CALLOUT_PENDING);
 1121                         c->c_flags |= CALLOUT_ACTIVE;
 1122                         CTR6(KTR_CALLOUT,
 1123                     "migration of %p func %p arg %p in %d.%08x to %u deferred",
 1124                             c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1125                             (u_int)(to_sbt & 0xffffffff), cpu);
 1126                         CC_UNLOCK(cc);
 1127                         return (cancelled);
 1128                 }
 1129                 cc = callout_cpu_switch(c, cc, cpu);
 1130         }
 1131 #endif
 1132 
 1133         callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
 1134         CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
 1135             cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1136             (u_int)(to_sbt & 0xffffffff));
 1137         CC_UNLOCK(cc);
 1138 
 1139         return (cancelled);
 1140 }
 1141 
 1142 /*
 1143  * Common idioms that can be optimized in the future.
 1144  */
 1145 int
 1146 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
 1147 {
 1148         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
 1149 }
 1150 
 1151 int
 1152 callout_schedule(struct callout *c, int to_ticks)
 1153 {
 1154         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
 1155 }
 1156 
 1157 int
 1158 _callout_stop_safe(struct callout *c, int flags, void (*drain)(void *))
 1159 {
 1160         struct callout_cpu *cc, *old_cc;
 1161         struct lock_class *class;
 1162         int direct, sq_locked, use_lock;
 1163         int not_on_a_list;
 1164 
 1165         if ((flags & CS_DRAIN) != 0)
 1166                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
 1167                     "calling %s", __func__);
 1168 
 1169         /*
 1170          * Some old subsystems don't hold Giant while running a callout_stop(),
 1171          * so just discard this check for the moment.
 1172          */
 1173         if ((flags & CS_DRAIN) == 0 && c->c_lock != NULL) {
 1174                 if (c->c_lock == &Giant.lock_object)
 1175                         use_lock = mtx_owned(&Giant);
 1176                 else {
 1177                         use_lock = 1;
 1178                         class = LOCK_CLASS(c->c_lock);
 1179                         class->lc_assert(c->c_lock, LA_XLOCKED);
 1180                 }
 1181         } else
 1182                 use_lock = 0;
 1183         if (c->c_iflags & CALLOUT_DIRECT) {
 1184                 direct = 1;
 1185         } else {
 1186                 direct = 0;
 1187         }
 1188         sq_locked = 0;
 1189         old_cc = NULL;
 1190 again:
 1191         cc = callout_lock(c);
 1192 
 1193         if ((c->c_iflags & (CALLOUT_DFRMIGRATION | CALLOUT_PENDING)) ==
 1194             (CALLOUT_DFRMIGRATION | CALLOUT_PENDING) &&
 1195             ((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE)) {
 1196                 /*
 1197                  * Special case where this slipped in while we
 1198                  * were migrating *as* the callout is about to
 1199                  * execute. The caller probably holds the lock
 1200                  * the callout wants.
 1201                  *
 1202                  * Get rid of the migration first. Then set
 1203                  * the flag that tells this code *not* to
 1204                  * try to remove it from any lists (its not
 1205                  * on one yet). When the callout wheel runs,
 1206                  * it will ignore this callout.
 1207                  */
 1208                 c->c_iflags &= ~CALLOUT_PENDING;
 1209                 c->c_flags &= ~CALLOUT_ACTIVE;
 1210                 not_on_a_list = 1;
 1211         } else {
 1212                 not_on_a_list = 0;
 1213         }
 1214 
 1215         /*
 1216          * If the callout was migrating while the callout cpu lock was
 1217          * dropped,  just drop the sleepqueue lock and check the states
 1218          * again.
 1219          */
 1220         if (sq_locked != 0 && cc != old_cc) {
 1221 #ifdef SMP
 1222                 CC_UNLOCK(cc);
 1223                 sleepq_release(&cc_exec_waiting(old_cc, direct));
 1224                 sq_locked = 0;
 1225                 old_cc = NULL;
 1226                 goto again;
 1227 #else
 1228                 panic("migration should not happen");
 1229 #endif
 1230         }
 1231 
 1232         /*
 1233          * If the callout isn't pending, it's not on the queue, so
 1234          * don't attempt to remove it from the queue.  We can try to
 1235          * stop it by other means however.
 1236          */
 1237         if (!(c->c_iflags & CALLOUT_PENDING)) {
 1238                 /*
 1239                  * If it wasn't on the queue and it isn't the current
 1240                  * callout, then we can't stop it, so just bail.
 1241                  * It probably has already been run (if locking
 1242                  * is properly done). You could get here if the caller
 1243                  * calls stop twice in a row for example. The second
 1244                  * call would fall here without CALLOUT_ACTIVE set.
 1245                  */
 1246                 c->c_flags &= ~CALLOUT_ACTIVE;
 1247                 if (cc_exec_curr(cc, direct) != c) {
 1248                         CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1249                             c, c->c_func, c->c_arg);
 1250                         CC_UNLOCK(cc);
 1251                         if (sq_locked)
 1252                                 sleepq_release(&cc_exec_waiting(cc, direct));
 1253                         return (-1);
 1254                 }
 1255 
 1256                 if ((flags & CS_DRAIN) != 0) {
 1257                         /*
 1258                          * The current callout is running (or just
 1259                          * about to run) and blocking is allowed, so
 1260                          * just wait for the current invocation to
 1261                          * finish.
 1262                          */
 1263                         while (cc_exec_curr(cc, direct) == c) {
 1264                                 /*
 1265                                  * Use direct calls to sleepqueue interface
 1266                                  * instead of cv/msleep in order to avoid
 1267                                  * a LOR between cc_lock and sleepqueue
 1268                                  * chain spinlocks.  This piece of code
 1269                                  * emulates a msleep_spin() call actually.
 1270                                  *
 1271                                  * If we already have the sleepqueue chain
 1272                                  * locked, then we can safely block.  If we
 1273                                  * don't already have it locked, however,
 1274                                  * we have to drop the cc_lock to lock
 1275                                  * it.  This opens several races, so we
 1276                                  * restart at the beginning once we have
 1277                                  * both locks.  If nothing has changed, then
 1278                                  * we will end up back here with sq_locked
 1279                                  * set.
 1280                                  */
 1281                                 if (!sq_locked) {
 1282                                         CC_UNLOCK(cc);
 1283                                         sleepq_lock(
 1284                                             &cc_exec_waiting(cc, direct));
 1285                                         sq_locked = 1;
 1286                                         old_cc = cc;
 1287                                         goto again;
 1288                                 }
 1289 
 1290                                 /*
 1291                                  * Migration could be cancelled here, but
 1292                                  * as long as it is still not sure when it
 1293                                  * will be packed up, just let softclock()
 1294                                  * take care of it.
 1295                                  */
 1296                                 cc_exec_waiting(cc, direct) = true;
 1297                                 DROP_GIANT();
 1298                                 CC_UNLOCK(cc);
 1299                                 sleepq_add(
 1300                                     &cc_exec_waiting(cc, direct),
 1301                                     &cc->cc_lock.lock_object, "codrain",
 1302                                     SLEEPQ_SLEEP, 0);
 1303                                 sleepq_wait(
 1304                                     &cc_exec_waiting(cc, direct),
 1305                                              0);
 1306                                 sq_locked = 0;
 1307                                 old_cc = NULL;
 1308 
 1309                                 /* Reacquire locks previously released. */
 1310                                 PICKUP_GIANT();
 1311                                 CC_LOCK(cc);
 1312                         }
 1313                 } else if (use_lock &&
 1314                            !cc_exec_cancel(cc, direct) && (drain == NULL)) {
 1315                         
 1316                         /*
 1317                          * The current callout is waiting for its
 1318                          * lock which we hold.  Cancel the callout
 1319                          * and return.  After our caller drops the
 1320                          * lock, the callout will be skipped in
 1321                          * softclock(). This *only* works with a
 1322                          * callout_stop() *not* callout_drain() or
 1323                          * callout_async_drain().
 1324                          */
 1325                         cc_exec_cancel(cc, direct) = true;
 1326                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1327                             c, c->c_func, c->c_arg);
 1328                         KASSERT(!cc_cce_migrating(cc, direct),
 1329                             ("callout wrongly scheduled for migration"));
 1330                         if (callout_migrating(c)) {
 1331                                 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
 1332 #ifdef SMP
 1333                                 cc_migration_cpu(cc, direct) = CPUBLOCK;
 1334                                 cc_migration_time(cc, direct) = 0;
 1335                                 cc_migration_prec(cc, direct) = 0;
 1336                                 cc_migration_func(cc, direct) = NULL;
 1337                                 cc_migration_arg(cc, direct) = NULL;
 1338 #endif
 1339                         }
 1340                         CC_UNLOCK(cc);
 1341                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
 1342                         return (1);
 1343                 } else if (callout_migrating(c)) {
 1344                         /*
 1345                          * The callout is currently being serviced
 1346                          * and the "next" callout is scheduled at
 1347                          * its completion with a migration. We remove
 1348                          * the migration flag so it *won't* get rescheduled,
 1349                          * but we can't stop the one thats running so
 1350                          * we return 0.
 1351                          */
 1352                         c->c_iflags &= ~CALLOUT_DFRMIGRATION;
 1353 #ifdef SMP
 1354                         /* 
 1355                          * We can't call cc_cce_cleanup here since
 1356                          * if we do it will remove .ce_curr and
 1357                          * its still running. This will prevent a
 1358                          * reschedule of the callout when the 
 1359                          * execution completes.
 1360                          */
 1361                         cc_migration_cpu(cc, direct) = CPUBLOCK;
 1362                         cc_migration_time(cc, direct) = 0;
 1363                         cc_migration_prec(cc, direct) = 0;
 1364                         cc_migration_func(cc, direct) = NULL;
 1365                         cc_migration_arg(cc, direct) = NULL;
 1366 #endif
 1367                         CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
 1368                             c, c->c_func, c->c_arg);
 1369                         if (drain) {
 1370                                 cc_exec_drain(cc, direct) = drain;
 1371                         }
 1372                         CC_UNLOCK(cc);
 1373                         return ((flags & CS_MIGRBLOCK) != 0);
 1374                 }
 1375                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1376                     c, c->c_func, c->c_arg);
 1377                 if (drain) {
 1378                         cc_exec_drain(cc, direct) = drain;
 1379                 }
 1380                 CC_UNLOCK(cc);
 1381                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
 1382                 return (0);
 1383         }
 1384         if (sq_locked)
 1385                 sleepq_release(&cc_exec_waiting(cc, direct));
 1386 
 1387         c->c_iflags &= ~CALLOUT_PENDING;
 1388         c->c_flags &= ~CALLOUT_ACTIVE;
 1389 
 1390         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1391             c, c->c_func, c->c_arg);
 1392         if (not_on_a_list == 0) {
 1393                 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
 1394                         if (cc_exec_next(cc) == c)
 1395                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1396                         LIST_REMOVE(c, c_links.le);
 1397                 } else {
 1398                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1399                 }
 1400         }
 1401         callout_cc_del(c, cc);
 1402         CC_UNLOCK(cc);
 1403         return (1);
 1404 }
 1405 
 1406 void
 1407 callout_init(struct callout *c, int mpsafe)
 1408 {
 1409         bzero(c, sizeof *c);
 1410         if (mpsafe) {
 1411                 c->c_lock = NULL;
 1412                 c->c_iflags = CALLOUT_RETURNUNLOCKED;
 1413         } else {
 1414                 c->c_lock = &Giant.lock_object;
 1415                 c->c_iflags = 0;
 1416         }
 1417         c->c_cpu = timeout_cpu;
 1418 }
 1419 
 1420 void
 1421 _callout_init_lock(struct callout *c, struct lock_object *lock, int flags)
 1422 {
 1423         bzero(c, sizeof *c);
 1424         c->c_lock = lock;
 1425         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
 1426             ("callout_init_lock: bad flags %d", flags));
 1427         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
 1428             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
 1429         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
 1430             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
 1431             __func__));
 1432         c->c_iflags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
 1433         c->c_cpu = timeout_cpu;
 1434 }
 1435 
 1436 #ifdef APM_FIXUP_CALLTODO
 1437 /* 
 1438  * Adjust the kernel calltodo timeout list.  This routine is used after 
 1439  * an APM resume to recalculate the calltodo timer list values with the 
 1440  * number of hz's we have been sleeping.  The next hardclock() will detect 
 1441  * that there are fired timers and run softclock() to execute them.
 1442  *
 1443  * Please note, I have not done an exhaustive analysis of what code this
 1444  * might break.  I am motivated to have my select()'s and alarm()'s that
 1445  * have expired during suspend firing upon resume so that the applications
 1446  * which set the timer can do the maintanence the timer was for as close
 1447  * as possible to the originally intended time.  Testing this code for a 
 1448  * week showed that resuming from a suspend resulted in 22 to 25 timers 
 1449  * firing, which seemed independant on whether the suspend was 2 hours or
 1450  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 1451  */
 1452 void
 1453 adjust_timeout_calltodo(struct timeval *time_change)
 1454 {
 1455         register struct callout *p;
 1456         unsigned long delta_ticks;
 1457 
 1458         /* 
 1459          * How many ticks were we asleep?
 1460          * (stolen from tvtohz()).
 1461          */
 1462 
 1463         /* Don't do anything */
 1464         if (time_change->tv_sec < 0)
 1465                 return;
 1466         else if (time_change->tv_sec <= LONG_MAX / 1000000)
 1467                 delta_ticks = (time_change->tv_sec * 1000000 +
 1468                                time_change->tv_usec + (tick - 1)) / tick + 1;
 1469         else if (time_change->tv_sec <= LONG_MAX / hz)
 1470                 delta_ticks = time_change->tv_sec * hz +
 1471                               (time_change->tv_usec + (tick - 1)) / tick + 1;
 1472         else
 1473                 delta_ticks = LONG_MAX;
 1474 
 1475         if (delta_ticks > INT_MAX)
 1476                 delta_ticks = INT_MAX;
 1477 
 1478         /* 
 1479          * Now rip through the timer calltodo list looking for timers
 1480          * to expire.
 1481          */
 1482 
 1483         /* don't collide with softclock() */
 1484         CC_LOCK(cc);
 1485         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 1486                 p->c_time -= delta_ticks;
 1487 
 1488                 /* Break if the timer had more time on it than delta_ticks */
 1489                 if (p->c_time > 0)
 1490                         break;
 1491 
 1492                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
 1493                 delta_ticks = -p->c_time;
 1494         }
 1495         CC_UNLOCK(cc);
 1496 
 1497         return;
 1498 }
 1499 #endif /* APM_FIXUP_CALLTODO */
 1500 
 1501 static int
 1502 flssbt(sbintime_t sbt)
 1503 {
 1504 
 1505         sbt += (uint64_t)sbt >> 1;
 1506         if (sizeof(long) >= sizeof(sbintime_t))
 1507                 return (flsl(sbt));
 1508         if (sbt >= SBT_1S)
 1509                 return (flsl(((uint64_t)sbt) >> 32) + 32);
 1510         return (flsl(sbt));
 1511 }
 1512 
 1513 /*
 1514  * Dump immediate statistic snapshot of the scheduled callouts.
 1515  */
 1516 static int
 1517 sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
 1518 {
 1519         struct callout *tmp;
 1520         struct callout_cpu *cc;
 1521         struct callout_list *sc;
 1522         sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
 1523         int ct[64], cpr[64], ccpbk[32];
 1524         int error, val, i, count, tcum, pcum, maxc, c, medc;
 1525 #ifdef SMP
 1526         int cpu;
 1527 #endif
 1528 
 1529         val = 0;
 1530         error = sysctl_handle_int(oidp, &val, 0, req);
 1531         if (error != 0 || req->newptr == NULL)
 1532                 return (error);
 1533         count = maxc = 0;
 1534         st = spr = maxt = maxpr = 0;
 1535         bzero(ccpbk, sizeof(ccpbk));
 1536         bzero(ct, sizeof(ct));
 1537         bzero(cpr, sizeof(cpr));
 1538         now = sbinuptime();
 1539 #ifdef SMP
 1540         CPU_FOREACH(cpu) {
 1541                 cc = CC_CPU(cpu);
 1542 #else
 1543                 cc = CC_CPU(timeout_cpu);
 1544 #endif
 1545                 CC_LOCK(cc);
 1546                 for (i = 0; i < callwheelsize; i++) {
 1547                         sc = &cc->cc_callwheel[i];
 1548                         c = 0;
 1549                         LIST_FOREACH(tmp, sc, c_links.le) {
 1550                                 c++;
 1551                                 t = tmp->c_time - now;
 1552                                 if (t < 0)
 1553                                         t = 0;
 1554                                 st += t / SBT_1US;
 1555                                 spr += tmp->c_precision / SBT_1US;
 1556                                 if (t > maxt)
 1557                                         maxt = t;
 1558                                 if (tmp->c_precision > maxpr)
 1559                                         maxpr = tmp->c_precision;
 1560                                 ct[flssbt(t)]++;
 1561                                 cpr[flssbt(tmp->c_precision)]++;
 1562                         }
 1563                         if (c > maxc)
 1564                                 maxc = c;
 1565                         ccpbk[fls(c + c / 2)]++;
 1566                         count += c;
 1567                 }
 1568                 CC_UNLOCK(cc);
 1569 #ifdef SMP
 1570         }
 1571 #endif
 1572 
 1573         for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
 1574                 tcum += ct[i];
 1575         medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1576         for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
 1577                 pcum += cpr[i];
 1578         medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1579         for (i = 0, c = 0; i < 32 && c < count / 2; i++)
 1580                 c += ccpbk[i];
 1581         medc = (i >= 2) ? (1 << (i - 2)) : 0;
 1582 
 1583         printf("Scheduled callouts statistic snapshot:\n");
 1584         printf("  Callouts: %6d  Buckets: %6d*%-3d  Bucket size: 0.%06ds\n",
 1585             count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
 1586         printf("  C/Bk: med %5d         avg %6d.%06jd  max %6d\n",
 1587             medc,
 1588             count / callwheelsize / mp_ncpus,
 1589             (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
 1590             maxc);
 1591         printf("  Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1592             medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
 1593             (st / count) / 1000000, (st / count) % 1000000,
 1594             maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
 1595         printf("  Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1596             medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
 1597             (spr / count) / 1000000, (spr / count) % 1000000,
 1598             maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
 1599         printf("  Distribution:       \tbuckets\t   time\t   tcum\t"
 1600             "   prec\t   pcum\n");
 1601         for (i = 0, tcum = pcum = 0; i < 64; i++) {
 1602                 if (ct[i] == 0 && cpr[i] == 0)
 1603                         continue;
 1604                 t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
 1605                 tcum += ct[i];
 1606                 pcum += cpr[i];
 1607                 printf("  %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
 1608                     t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
 1609                     i - 1 - (32 - CC_HASH_SHIFT),
 1610                     ct[i], tcum, cpr[i], pcum);
 1611         }
 1612         return (error);
 1613 }
 1614 SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
 1615     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 1616     0, 0, sysctl_kern_callout_stat, "I",
 1617     "Dump immediate statistic snapshot of the scheduled callouts");

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