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 281511 2015-04-14 00:02:39Z rrs $");
   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, kernel, , callout__start,
   73     "struct callout *");
   74 SDT_PROBE_DEFINE1(callout_execute, kernel, , callout__end,
   75     "struct callout *");
   76 
   77 #ifdef CALLOUT_PROFILING
   78 static int avg_depth;
   79 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
   80     "Average number of items examined per softclock call. Units = 1/1000");
   81 static int avg_gcalls;
   82 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
   83     "Average number of Giant callouts made per softclock call. Units = 1/1000");
   84 static int avg_lockcalls;
   85 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
   86     "Average number of lock callouts made per softclock call. Units = 1/1000");
   87 static int avg_mpcalls;
   88 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
   89     "Average number of MP callouts made per softclock call. Units = 1/1000");
   90 static int avg_depth_dir;
   91 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth_dir, CTLFLAG_RD, &avg_depth_dir, 0,
   92     "Average number of direct callouts examined per callout_process call. "
   93     "Units = 1/1000");
   94 static int avg_lockcalls_dir;
   95 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls_dir, CTLFLAG_RD,
   96     &avg_lockcalls_dir, 0, "Average number of lock direct callouts made per "
   97     "callout_process call. Units = 1/1000");
   98 static int avg_mpcalls_dir;
   99 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls_dir, CTLFLAG_RD, &avg_mpcalls_dir,
  100     0, "Average number of MP direct callouts made per callout_process call. "
  101     "Units = 1/1000");
  102 #endif
  103 
  104 static int ncallout;
  105 SYSCTL_INT(_kern, OID_AUTO, ncallout, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &ncallout, 0,
  106     "Number of entries in callwheel and size of timeout() preallocation");
  107 
  108 #ifdef  RSS
  109 static int pin_default_swi = 1;
  110 static int pin_pcpu_swi = 1;
  111 #else
  112 static int pin_default_swi = 0;
  113 static int pin_pcpu_swi = 0;
  114 #endif
  115 
  116 SYSCTL_INT(_kern, OID_AUTO, pin_default_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_default_swi,
  117     0, "Pin the default (non-per-cpu) swi (shared with PCPU 0 swi)");
  118 SYSCTL_INT(_kern, OID_AUTO, pin_pcpu_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_pcpu_swi,
  119     0, "Pin the per-CPU swis (except PCPU 0, which is also default");
  120 
  121 /*
  122  * TODO:
  123  *      allocate more timeout table slots when table overflows.
  124  */
  125 u_int callwheelsize, callwheelmask;
  126 
  127 /*
  128  * The callout cpu exec entities represent informations necessary for
  129  * describing the state of callouts currently running on the CPU and the ones
  130  * necessary for migrating callouts to the new callout cpu. In particular,
  131  * the first entry of the array cc_exec_entity holds informations for callout
  132  * running in SWI thread context, while the second one holds informations
  133  * for callout running directly from hardware interrupt context.
  134  * The cached informations are very important for deferring migration when
  135  * the migrating callout is already running.
  136  */
  137 struct cc_exec {
  138         struct callout          *cc_curr;
  139 #ifdef SMP
  140         void                    (*ce_migration_func)(void *);
  141         void                    *ce_migration_arg;
  142         int                     ce_migration_cpu;
  143         sbintime_t              ce_migration_time;
  144         sbintime_t              ce_migration_prec;
  145 #endif
  146         bool                    cc_cancel;
  147         bool                    cc_waiting;
  148 };
  149 
  150 /*
  151  * There is one struct callout_cpu per cpu, holding all relevant
  152  * state for the callout processing thread on the individual CPU.
  153  */
  154 struct callout_cpu {
  155         struct mtx_padalign     cc_lock;
  156         struct cc_exec          cc_exec_entity[2];
  157         struct callout          *cc_next;
  158         struct callout          *cc_callout;
  159         struct callout_list     *cc_callwheel;
  160         struct callout_tailq    cc_expireq;
  161         struct callout_slist    cc_callfree;
  162         sbintime_t              cc_firstevent;
  163         sbintime_t              cc_lastscan;
  164         void                    *cc_cookie;
  165         u_int                   cc_bucket;
  166         u_int                   cc_inited;
  167         char                    cc_ktr_event_name[20];
  168 };
  169 
  170 #define callout_migrating(c)    ((c)->c_iflags & CALLOUT_DFRMIGRATION)
  171 
  172 #define cc_exec_curr(cc, dir)           cc->cc_exec_entity[dir].cc_curr
  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_UNLOCK(cc);
  683         if (c_lock != NULL) {
  684                 class->lc_lock(c_lock, lock_status);
  685                 /*
  686                  * The callout may have been cancelled
  687                  * while we switched locks.
  688                  */
  689                 if (cc_exec_cancel(cc, direct)) {
  690                         class->lc_unlock(c_lock);
  691                         goto skip;
  692                 }
  693                 /* The callout cannot be stopped now. */
  694                 cc_exec_cancel(cc, direct) = true;
  695                 if (c_lock == &Giant.lock_object) {
  696 #ifdef CALLOUT_PROFILING
  697                         (*gcalls)++;
  698 #endif
  699                         CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
  700                             c, c_func, c_arg);
  701                 } else {
  702 #ifdef CALLOUT_PROFILING
  703                         (*lockcalls)++;
  704 #endif
  705                         CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
  706                             c, c_func, c_arg);
  707                 }
  708         } else {
  709 #ifdef CALLOUT_PROFILING
  710                 (*mpcalls)++;
  711 #endif
  712                 CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
  713                     c, c_func, c_arg);
  714         }
  715         KTR_STATE3(KTR_SCHED, "callout", cc->cc_ktr_event_name, "running",
  716             "func:%p", c_func, "arg:%p", c_arg, "direct:%d", direct);
  717 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  718         sbt1 = sbinuptime();
  719 #endif
  720         THREAD_NO_SLEEPING();
  721         SDT_PROBE(callout_execute, kernel, , callout__start, c, 0, 0, 0, 0);
  722         c_func(c_arg);
  723         SDT_PROBE(callout_execute, kernel, , callout__end, c, 0, 0, 0, 0);
  724         THREAD_SLEEPING_OK();
  725 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  726         sbt2 = sbinuptime();
  727         sbt2 -= sbt1;
  728         if (sbt2 > maxdt) {
  729                 if (lastfunc != c_func || sbt2 > maxdt * 2) {
  730                         ts2 = sbttots(sbt2);
  731                         printf(
  732                 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  733                             c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
  734                 }
  735                 maxdt = sbt2;
  736                 lastfunc = c_func;
  737         }
  738 #endif
  739         KTR_STATE0(KTR_SCHED, "callout", cc->cc_ktr_event_name, "idle");
  740         CTR1(KTR_CALLOUT, "callout %p finished", c);
  741         if ((c_iflags & CALLOUT_RETURNUNLOCKED) == 0)
  742                 class->lc_unlock(c_lock);
  743 skip:
  744         CC_LOCK(cc);
  745         KASSERT(cc_exec_curr(cc, direct) == c, ("mishandled cc_curr"));
  746         cc_exec_curr(cc, direct) = NULL;
  747         if (cc_exec_waiting(cc, direct)) {
  748                 /*
  749                  * There is someone waiting for the
  750                  * callout to complete.
  751                  * If the callout was scheduled for
  752                  * migration just cancel it.
  753                  */
  754                 if (cc_cce_migrating(cc, direct)) {
  755                         cc_cce_cleanup(cc, direct);
  756 
  757                         /*
  758                          * It should be assert here that the callout is not
  759                          * destroyed but that is not easy.
  760                          */
  761                         c->c_iflags &= ~CALLOUT_DFRMIGRATION;
  762                 }
  763                 cc_exec_waiting(cc, direct) = false;
  764                 CC_UNLOCK(cc);
  765                 wakeup(&cc_exec_waiting(cc, direct));
  766                 CC_LOCK(cc);
  767         } else if (cc_cce_migrating(cc, direct)) {
  768                 KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0,
  769                     ("Migrating legacy callout %p", c));
  770 #ifdef SMP
  771                 /*
  772                  * If the callout was scheduled for
  773                  * migration just perform it now.
  774                  */
  775                 new_cpu = cc_migration_cpu(cc, direct);
  776                 new_time = cc_migration_time(cc, direct);
  777                 new_prec = cc_migration_prec(cc, direct);
  778                 new_func = cc_migration_func(cc, direct);
  779                 new_arg = cc_migration_arg(cc, direct);
  780                 cc_cce_cleanup(cc, direct);
  781 
  782                 /*
  783                  * It should be assert here that the callout is not destroyed
  784                  * but that is not easy.
  785                  *
  786                  * As first thing, handle deferred callout stops.
  787                  */
  788                 if (!callout_migrating(c)) {
  789                         CTR3(KTR_CALLOUT,
  790                              "deferred cancelled %p func %p arg %p",
  791                              c, new_func, new_arg);
  792                         callout_cc_del(c, cc);
  793                         return;
  794                 }
  795                 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
  796 
  797                 new_cc = callout_cpu_switch(c, cc, new_cpu);
  798                 flags = (direct) ? C_DIRECT_EXEC : 0;
  799                 callout_cc_add(c, new_cc, new_time, new_prec, new_func,
  800                     new_arg, new_cpu, flags);
  801                 CC_UNLOCK(new_cc);
  802                 CC_LOCK(cc);
  803 #else
  804                 panic("migration should not happen");
  805 #endif
  806         }
  807         /*
  808          * If the current callout is locally allocated (from
  809          * timeout(9)) then put it on the freelist.
  810          *
  811          * Note: we need to check the cached copy of c_iflags because
  812          * if it was not local, then it's not safe to deref the
  813          * callout pointer.
  814          */
  815         KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0 ||
  816             c->c_iflags == CALLOUT_LOCAL_ALLOC,
  817             ("corrupted callout"));
  818         if (c_iflags & CALLOUT_LOCAL_ALLOC)
  819                 callout_cc_del(c, cc);
  820 }
  821 
  822 /*
  823  * The callout mechanism is based on the work of Adam M. Costello and
  824  * George Varghese, published in a technical report entitled "Redesigning
  825  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  826  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  827  * used in this implementation was published by G. Varghese and T. Lauck in
  828  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  829  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  830  * the 11th ACM Annual Symposium on Operating Systems Principles,
  831  * Austin, Texas Nov 1987.
  832  */
  833 
  834 /*
  835  * Software (low priority) clock interrupt.
  836  * Run periodic events from timeout queue.
  837  */
  838 void
  839 softclock(void *arg)
  840 {
  841         struct callout_cpu *cc;
  842         struct callout *c;
  843 #ifdef CALLOUT_PROFILING
  844         int depth = 0, gcalls = 0, lockcalls = 0, mpcalls = 0;
  845 #endif
  846 
  847         cc = (struct callout_cpu *)arg;
  848         CC_LOCK(cc);
  849         while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
  850                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
  851                 softclock_call_cc(c, cc,
  852 #ifdef CALLOUT_PROFILING
  853                     &mpcalls, &lockcalls, &gcalls,
  854 #endif
  855                     0);
  856 #ifdef CALLOUT_PROFILING
  857                 ++depth;
  858 #endif
  859         }
  860 #ifdef CALLOUT_PROFILING
  861         avg_depth += (depth * 1000 - avg_depth) >> 8;
  862         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  863         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  864         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  865 #endif
  866         CC_UNLOCK(cc);
  867 }
  868 
  869 /*
  870  * timeout --
  871  *      Execute a function after a specified length of time.
  872  *
  873  * untimeout --
  874  *      Cancel previous timeout function call.
  875  *
  876  * callout_handle_init --
  877  *      Initialize a handle so that using it with untimeout is benign.
  878  *
  879  *      See AT&T BCI Driver Reference Manual for specification.  This
  880  *      implementation differs from that one in that although an
  881  *      identification value is returned from timeout, the original
  882  *      arguments to timeout as well as the identifier are used to
  883  *      identify entries for untimeout.
  884  */
  885 struct callout_handle
  886 timeout(timeout_t *ftn, void *arg, int to_ticks)
  887 {
  888         struct callout_cpu *cc;
  889         struct callout *new;
  890         struct callout_handle handle;
  891 
  892         cc = CC_CPU(timeout_cpu);
  893         CC_LOCK(cc);
  894         /* Fill in the next free callout structure. */
  895         new = SLIST_FIRST(&cc->cc_callfree);
  896         if (new == NULL)
  897                 /* XXX Attempt to malloc first */
  898                 panic("timeout table full");
  899         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  900         callout_reset(new, to_ticks, ftn, arg);
  901         handle.callout = new;
  902         CC_UNLOCK(cc);
  903 
  904         return (handle);
  905 }
  906 
  907 void
  908 untimeout(timeout_t *ftn, void *arg, struct callout_handle handle)
  909 {
  910         struct callout_cpu *cc;
  911 
  912         /*
  913          * Check for a handle that was initialized
  914          * by callout_handle_init, but never used
  915          * for a real timeout.
  916          */
  917         if (handle.callout == NULL)
  918                 return;
  919 
  920         cc = callout_lock(handle.callout);
  921         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  922                 callout_stop(handle.callout);
  923         CC_UNLOCK(cc);
  924 }
  925 
  926 void
  927 callout_handle_init(struct callout_handle *handle)
  928 {
  929         handle->callout = NULL;
  930 }
  931 
  932 /*
  933  * New interface; clients allocate their own callout structures.
  934  *
  935  * callout_reset() - establish or change a timeout
  936  * callout_stop() - disestablish a timeout
  937  * callout_init() - initialize a callout structure so that it can
  938  *      safely be passed to callout_reset() and callout_stop()
  939  *
  940  * <sys/callout.h> defines three convenience macros:
  941  *
  942  * callout_active() - returns truth if callout has not been stopped,
  943  *      drained, or deactivated since the last time the callout was
  944  *      reset.
  945  * callout_pending() - returns truth if callout is still waiting for timeout
  946  * callout_deactivate() - marks the callout as having been serviced
  947  */
  948 int
  949 callout_reset_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t precision,
  950     void (*ftn)(void *), void *arg, int cpu, int flags)
  951 {
  952         sbintime_t to_sbt, pr;
  953         struct callout_cpu *cc;
  954         int cancelled, direct;
  955         int ignore_cpu=0;
  956 
  957         cancelled = 0;
  958         if (cpu == -1) {
  959                 ignore_cpu = 1;
  960         } else if ((cpu >= MAXCPU) ||
  961                    ((CC_CPU(cpu))->cc_inited == 0)) {
  962                 /* Invalid CPU spec */
  963                 panic("Invalid CPU in callout %d", cpu);
  964         }
  965         if (flags & C_ABSOLUTE) {
  966                 to_sbt = sbt;
  967         } else {
  968                 if ((flags & C_HARDCLOCK) && (sbt < tick_sbt))
  969                         sbt = tick_sbt;
  970                 if ((flags & C_HARDCLOCK) ||
  971 #ifdef NO_EVENTTIMERS
  972                     sbt >= sbt_timethreshold) {
  973                         to_sbt = getsbinuptime();
  974 
  975                         /* Add safety belt for the case of hz > 1000. */
  976                         to_sbt += tc_tick_sbt - tick_sbt;
  977 #else
  978                     sbt >= sbt_tickthreshold) {
  979                         /*
  980                          * Obtain the time of the last hardclock() call on
  981                          * this CPU directly from the kern_clocksource.c.
  982                          * This value is per-CPU, but it is equal for all
  983                          * active ones.
  984                          */
  985 #ifdef __LP64__
  986                         to_sbt = DPCPU_GET(hardclocktime);
  987 #else
  988                         spinlock_enter();
  989                         to_sbt = DPCPU_GET(hardclocktime);
  990                         spinlock_exit();
  991 #endif
  992 #endif
  993                         if ((flags & C_HARDCLOCK) == 0)
  994                                 to_sbt += tick_sbt;
  995                 } else
  996                         to_sbt = sbinuptime();
  997                 if (SBT_MAX - to_sbt < sbt)
  998                         to_sbt = SBT_MAX;
  999                 else
 1000                         to_sbt += sbt;
 1001                 pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
 1002                     sbt >> C_PRELGET(flags));
 1003                 if (pr > precision)
 1004                         precision = pr;
 1005         }
 1006         /* 
 1007          * This flag used to be added by callout_cc_add, but the
 1008          * first time you call this we could end up with the
 1009          * wrong direct flag if we don't do it before we add.
 1010          */
 1011         if (flags & C_DIRECT_EXEC) {
 1012                 direct = 1;
 1013         } else {
 1014                 direct = 0;
 1015         }
 1016         KASSERT(!direct || c->c_lock == NULL,
 1017             ("%s: direct callout %p has lock", __func__, c));
 1018         cc = callout_lock(c);
 1019         /*
 1020          * Don't allow migration of pre-allocated callouts lest they
 1021          * become unbalanced or handle the case where the user does
 1022          * not care. 
 1023          */
 1024         if ((c->c_iflags & CALLOUT_LOCAL_ALLOC) ||
 1025             ignore_cpu) {
 1026                 cpu = c->c_cpu;
 1027         }
 1028 
 1029         if (cc_exec_curr(cc, direct) == c) {
 1030                 /*
 1031                  * We're being asked to reschedule a callout which is
 1032                  * currently in progress.  If there is a lock then we
 1033                  * can cancel the callout if it has not really started.
 1034                  */
 1035                 if (c->c_lock != NULL && cc_exec_cancel(cc, direct))
 1036                         cancelled = cc_exec_cancel(cc, direct) = true;
 1037                 if (cc_exec_waiting(cc, direct)) {
 1038                         /*
 1039                          * Someone has called callout_drain to kill this
 1040                          * callout.  Don't reschedule.
 1041                          */
 1042                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
 1043                             cancelled ? "cancelled" : "failed to cancel",
 1044                             c, c->c_func, c->c_arg);
 1045                         CC_UNLOCK(cc);
 1046                         return (cancelled);
 1047                 }
 1048 #ifdef SMP
 1049                 if (callout_migrating(c)) {
 1050                         /* 
 1051                          * This only occurs when a second callout_reset_sbt_on
 1052                          * is made after a previous one moved it into
 1053                          * deferred migration (below). Note we do *not* change
 1054                          * the prev_cpu even though the previous target may
 1055                          * be different.
 1056                          */
 1057                         cc_migration_cpu(cc, direct) = cpu;
 1058                         cc_migration_time(cc, direct) = to_sbt;
 1059                         cc_migration_prec(cc, direct) = precision;
 1060                         cc_migration_func(cc, direct) = ftn;
 1061                         cc_migration_arg(cc, direct) = arg;
 1062                         cancelled = 1;
 1063                         CC_UNLOCK(cc);
 1064                         return (cancelled);
 1065                 }
 1066 #endif
 1067         }
 1068         if (c->c_iflags & CALLOUT_PENDING) {
 1069                 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
 1070                         if (cc_exec_next(cc) == c)
 1071                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1072                         LIST_REMOVE(c, c_links.le);
 1073                 } else {
 1074                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1075                 }
 1076                 cancelled = 1;
 1077                 c->c_iflags &= ~ CALLOUT_PENDING;
 1078                 c->c_flags &= ~ CALLOUT_ACTIVE;
 1079         }
 1080 
 1081 #ifdef SMP
 1082         /*
 1083          * If the callout must migrate try to perform it immediately.
 1084          * If the callout is currently running, just defer the migration
 1085          * to a more appropriate moment.
 1086          */
 1087         if (c->c_cpu != cpu) {
 1088                 if (cc_exec_curr(cc, direct) == c) {
 1089                         /* 
 1090                          * Pending will have been removed since we are
 1091                          * actually executing the callout on another
 1092                          * CPU. That callout should be waiting on the
 1093                          * lock the caller holds. If we set both
 1094                          * active/and/pending after we return and the
 1095                          * lock on the executing callout proceeds, it
 1096                          * will then see pending is true and return.
 1097                          * At the return from the actual callout execution
 1098                          * the migration will occur in softclock_call_cc
 1099                          * and this new callout will be placed on the 
 1100                          * new CPU via a call to callout_cpu_switch() which
 1101                          * will get the lock on the right CPU followed
 1102                          * by a call callout_cc_add() which will add it there.
 1103                          * (see above in softclock_call_cc()).
 1104                          */
 1105                         cc_migration_cpu(cc, direct) = cpu;
 1106                         cc_migration_time(cc, direct) = to_sbt;
 1107                         cc_migration_prec(cc, direct) = precision;
 1108                         cc_migration_func(cc, direct) = ftn;
 1109                         cc_migration_arg(cc, direct) = arg;
 1110                         c->c_iflags |= (CALLOUT_DFRMIGRATION | CALLOUT_PENDING);
 1111                         c->c_flags |= CALLOUT_ACTIVE;
 1112                         CTR6(KTR_CALLOUT,
 1113                     "migration of %p func %p arg %p in %d.%08x to %u deferred",
 1114                             c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1115                             (u_int)(to_sbt & 0xffffffff), cpu);
 1116                         CC_UNLOCK(cc);
 1117                         return (cancelled);
 1118                 }
 1119                 cc = callout_cpu_switch(c, cc, cpu);
 1120         }
 1121 #endif
 1122 
 1123         callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
 1124         CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
 1125             cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1126             (u_int)(to_sbt & 0xffffffff));
 1127         CC_UNLOCK(cc);
 1128 
 1129         return (cancelled);
 1130 }
 1131 
 1132 /*
 1133  * Common idioms that can be optimized in the future.
 1134  */
 1135 int
 1136 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
 1137 {
 1138         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
 1139 }
 1140 
 1141 int
 1142 callout_schedule(struct callout *c, int to_ticks)
 1143 {
 1144         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
 1145 }
 1146 
 1147 int
 1148 _callout_stop_safe(struct callout *c, int safe)
 1149 {
 1150         struct callout_cpu *cc, *old_cc;
 1151         struct lock_class *class;
 1152         int direct, sq_locked, use_lock;
 1153         int not_on_a_list;
 1154 
 1155         if (safe)
 1156                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
 1157                     "calling %s", __func__);
 1158 
 1159         /*
 1160          * Some old subsystems don't hold Giant while running a callout_stop(),
 1161          * so just discard this check for the moment.
 1162          */
 1163         if (!safe && c->c_lock != NULL) {
 1164                 if (c->c_lock == &Giant.lock_object)
 1165                         use_lock = mtx_owned(&Giant);
 1166                 else {
 1167                         use_lock = 1;
 1168                         class = LOCK_CLASS(c->c_lock);
 1169                         class->lc_assert(c->c_lock, LA_XLOCKED);
 1170                 }
 1171         } else
 1172                 use_lock = 0;
 1173         if (c->c_iflags & CALLOUT_DIRECT) {
 1174                 direct = 1;
 1175         } else {
 1176                 direct = 0;
 1177         }
 1178         sq_locked = 0;
 1179         old_cc = NULL;
 1180 again:
 1181         cc = callout_lock(c);
 1182 
 1183         if ((c->c_iflags & (CALLOUT_DFRMIGRATION | CALLOUT_PENDING)) ==
 1184             (CALLOUT_DFRMIGRATION | CALLOUT_PENDING) &&
 1185             ((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE)) {
 1186                 /*
 1187                  * Special case where this slipped in while we
 1188                  * were migrating *as* the callout is about to
 1189                  * execute. The caller probably holds the lock
 1190                  * the callout wants.
 1191                  *
 1192                  * Get rid of the migration first. Then set
 1193                  * the flag that tells this code *not* to
 1194                  * try to remove it from any lists (its not
 1195                  * on one yet). When the callout wheel runs,
 1196                  * it will ignore this callout.
 1197                  */
 1198                 c->c_iflags &= ~CALLOUT_PENDING;
 1199                 c->c_flags &= ~CALLOUT_ACTIVE;
 1200                 not_on_a_list = 1;
 1201         } else {
 1202                 not_on_a_list = 0;
 1203         }
 1204 
 1205         /*
 1206          * If the callout was migrating while the callout cpu lock was
 1207          * dropped,  just drop the sleepqueue lock and check the states
 1208          * again.
 1209          */
 1210         if (sq_locked != 0 && cc != old_cc) {
 1211 #ifdef SMP
 1212                 CC_UNLOCK(cc);
 1213                 sleepq_release(&cc_exec_waiting(old_cc, direct));
 1214                 sq_locked = 0;
 1215                 old_cc = NULL;
 1216                 goto again;
 1217 #else
 1218                 panic("migration should not happen");
 1219 #endif
 1220         }
 1221 
 1222         /*
 1223          * If the callout isn't pending, it's not on the queue, so
 1224          * don't attempt to remove it from the queue.  We can try to
 1225          * stop it by other means however.
 1226          */
 1227         if (!(c->c_iflags & CALLOUT_PENDING)) {
 1228                 c->c_flags &= ~CALLOUT_ACTIVE;
 1229 
 1230                 /*
 1231                  * If it wasn't on the queue and it isn't the current
 1232                  * callout, then we can't stop it, so just bail.
 1233                  */
 1234                 if (cc_exec_curr(cc, direct) != c) {
 1235                         CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1236                             c, c->c_func, c->c_arg);
 1237                         CC_UNLOCK(cc);
 1238                         if (sq_locked)
 1239                                 sleepq_release(&cc_exec_waiting(cc, direct));
 1240                         return (0);
 1241                 }
 1242 
 1243                 if (safe) {
 1244                         /*
 1245                          * The current callout is running (or just
 1246                          * about to run) and blocking is allowed, so
 1247                          * just wait for the current invocation to
 1248                          * finish.
 1249                          */
 1250                         while (cc_exec_curr(cc, direct) == c) {
 1251                                 /*
 1252                                  * Use direct calls to sleepqueue interface
 1253                                  * instead of cv/msleep in order to avoid
 1254                                  * a LOR between cc_lock and sleepqueue
 1255                                  * chain spinlocks.  This piece of code
 1256                                  * emulates a msleep_spin() call actually.
 1257                                  *
 1258                                  * If we already have the sleepqueue chain
 1259                                  * locked, then we can safely block.  If we
 1260                                  * don't already have it locked, however,
 1261                                  * we have to drop the cc_lock to lock
 1262                                  * it.  This opens several races, so we
 1263                                  * restart at the beginning once we have
 1264                                  * both locks.  If nothing has changed, then
 1265                                  * we will end up back here with sq_locked
 1266                                  * set.
 1267                                  */
 1268                                 if (!sq_locked) {
 1269                                         CC_UNLOCK(cc);
 1270                                         sleepq_lock(
 1271                                             &cc_exec_waiting(cc, direct));
 1272                                         sq_locked = 1;
 1273                                         old_cc = cc;
 1274                                         goto again;
 1275                                 }
 1276 
 1277                                 /*
 1278                                  * Migration could be cancelled here, but
 1279                                  * as long as it is still not sure when it
 1280                                  * will be packed up, just let softclock()
 1281                                  * take care of it.
 1282                                  */
 1283                                 cc_exec_waiting(cc, direct) = true;
 1284                                 DROP_GIANT();
 1285                                 CC_UNLOCK(cc);
 1286                                 sleepq_add(
 1287                                     &cc_exec_waiting(cc, direct),
 1288                                     &cc->cc_lock.lock_object, "codrain",
 1289                                     SLEEPQ_SLEEP, 0);
 1290                                 sleepq_wait(
 1291                                     &cc_exec_waiting(cc, direct),
 1292                                              0);
 1293                                 sq_locked = 0;
 1294                                 old_cc = NULL;
 1295 
 1296                                 /* Reacquire locks previously released. */
 1297                                 PICKUP_GIANT();
 1298                                 CC_LOCK(cc);
 1299                         }
 1300                 } else if (use_lock &&
 1301                            !cc_exec_cancel(cc, direct)) {
 1302                         
 1303                         /*
 1304                          * The current callout is waiting for its
 1305                          * lock which we hold.  Cancel the callout
 1306                          * and return.  After our caller drops the
 1307                          * lock, the callout will be skipped in
 1308                          * softclock().
 1309                          */
 1310                         cc_exec_cancel(cc, direct) = true;
 1311                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1312                             c, c->c_func, c->c_arg);
 1313                         KASSERT(!cc_cce_migrating(cc, direct),
 1314                             ("callout wrongly scheduled for migration"));
 1315                         if (callout_migrating(c)) {
 1316                                 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
 1317 #ifdef SMP
 1318                                 cc_migration_cpu(cc, direct) = CPUBLOCK;
 1319                                 cc_migration_time(cc, direct) = 0;
 1320                                 cc_migration_prec(cc, direct) = 0;
 1321                                 cc_migration_func(cc, direct) = NULL;
 1322                                 cc_migration_arg(cc, direct) = NULL;
 1323 #endif
 1324                         }
 1325                         CC_UNLOCK(cc);
 1326                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
 1327                         return (1);
 1328                 } else if (callout_migrating(c)) {
 1329                         /*
 1330                          * The callout is currently being serviced
 1331                          * and the "next" callout is scheduled at
 1332                          * its completion with a migration. We remove
 1333                          * the migration flag so it *won't* get rescheduled,
 1334                          * but we can't stop the one thats running so
 1335                          * we return 0.
 1336                          */
 1337                         c->c_iflags &= ~CALLOUT_DFRMIGRATION;
 1338 #ifdef SMP
 1339                         /* 
 1340                          * We can't call cc_cce_cleanup here since
 1341                          * if we do it will remove .ce_curr and
 1342                          * its still running. This will prevent a
 1343                          * reschedule of the callout when the 
 1344                          * execution completes.
 1345                          */
 1346                         cc_migration_cpu(cc, direct) = CPUBLOCK;
 1347                         cc_migration_time(cc, direct) = 0;
 1348                         cc_migration_prec(cc, direct) = 0;
 1349                         cc_migration_func(cc, direct) = NULL;
 1350                         cc_migration_arg(cc, direct) = NULL;
 1351 #endif
 1352                         CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
 1353                             c, c->c_func, c->c_arg);
 1354                         CC_UNLOCK(cc);
 1355                         return (0);
 1356                 }
 1357                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1358                     c, c->c_func, c->c_arg);
 1359                 CC_UNLOCK(cc);
 1360                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
 1361                 return (0);
 1362         }
 1363         if (sq_locked)
 1364                 sleepq_release(&cc_exec_waiting(cc, direct));
 1365 
 1366         c->c_iflags &= ~CALLOUT_PENDING;
 1367         c->c_flags &= ~CALLOUT_ACTIVE;
 1368 
 1369         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1370             c, c->c_func, c->c_arg);
 1371         if (not_on_a_list == 0) {
 1372                 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
 1373                         if (cc_exec_next(cc) == c)
 1374                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1375                         LIST_REMOVE(c, c_links.le);
 1376                 } else {
 1377                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1378                 }
 1379         }
 1380         callout_cc_del(c, cc);
 1381         CC_UNLOCK(cc);
 1382         return (1);
 1383 }
 1384 
 1385 void
 1386 callout_init(struct callout *c, int mpsafe)
 1387 {
 1388         bzero(c, sizeof *c);
 1389         if (mpsafe) {
 1390                 c->c_lock = NULL;
 1391                 c->c_iflags = CALLOUT_RETURNUNLOCKED;
 1392         } else {
 1393                 c->c_lock = &Giant.lock_object;
 1394                 c->c_iflags = 0;
 1395         }
 1396         c->c_cpu = timeout_cpu;
 1397 }
 1398 
 1399 void
 1400 _callout_init_lock(struct callout *c, struct lock_object *lock, int flags)
 1401 {
 1402         bzero(c, sizeof *c);
 1403         c->c_lock = lock;
 1404         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
 1405             ("callout_init_lock: bad flags %d", flags));
 1406         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
 1407             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
 1408         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
 1409             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
 1410             __func__));
 1411         c->c_iflags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
 1412         c->c_cpu = timeout_cpu;
 1413 }
 1414 
 1415 #ifdef APM_FIXUP_CALLTODO
 1416 /* 
 1417  * Adjust the kernel calltodo timeout list.  This routine is used after 
 1418  * an APM resume to recalculate the calltodo timer list values with the 
 1419  * number of hz's we have been sleeping.  The next hardclock() will detect 
 1420  * that there are fired timers and run softclock() to execute them.
 1421  *
 1422  * Please note, I have not done an exhaustive analysis of what code this
 1423  * might break.  I am motivated to have my select()'s and alarm()'s that
 1424  * have expired during suspend firing upon resume so that the applications
 1425  * which set the timer can do the maintanence the timer was for as close
 1426  * as possible to the originally intended time.  Testing this code for a 
 1427  * week showed that resuming from a suspend resulted in 22 to 25 timers 
 1428  * firing, which seemed independant on whether the suspend was 2 hours or
 1429  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 1430  */
 1431 void
 1432 adjust_timeout_calltodo(struct timeval *time_change)
 1433 {
 1434         register struct callout *p;
 1435         unsigned long delta_ticks;
 1436 
 1437         /* 
 1438          * How many ticks were we asleep?
 1439          * (stolen from tvtohz()).
 1440          */
 1441 
 1442         /* Don't do anything */
 1443         if (time_change->tv_sec < 0)
 1444                 return;
 1445         else if (time_change->tv_sec <= LONG_MAX / 1000000)
 1446                 delta_ticks = (time_change->tv_sec * 1000000 +
 1447                                time_change->tv_usec + (tick - 1)) / tick + 1;
 1448         else if (time_change->tv_sec <= LONG_MAX / hz)
 1449                 delta_ticks = time_change->tv_sec * hz +
 1450                               (time_change->tv_usec + (tick - 1)) / tick + 1;
 1451         else
 1452                 delta_ticks = LONG_MAX;
 1453 
 1454         if (delta_ticks > INT_MAX)
 1455                 delta_ticks = INT_MAX;
 1456 
 1457         /* 
 1458          * Now rip through the timer calltodo list looking for timers
 1459          * to expire.
 1460          */
 1461 
 1462         /* don't collide with softclock() */
 1463         CC_LOCK(cc);
 1464         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 1465                 p->c_time -= delta_ticks;
 1466 
 1467                 /* Break if the timer had more time on it than delta_ticks */
 1468                 if (p->c_time > 0)
 1469                         break;
 1470 
 1471                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
 1472                 delta_ticks = -p->c_time;
 1473         }
 1474         CC_UNLOCK(cc);
 1475 
 1476         return;
 1477 }
 1478 #endif /* APM_FIXUP_CALLTODO */
 1479 
 1480 static int
 1481 flssbt(sbintime_t sbt)
 1482 {
 1483 
 1484         sbt += (uint64_t)sbt >> 1;
 1485         if (sizeof(long) >= sizeof(sbintime_t))
 1486                 return (flsl(sbt));
 1487         if (sbt >= SBT_1S)
 1488                 return (flsl(((uint64_t)sbt) >> 32) + 32);
 1489         return (flsl(sbt));
 1490 }
 1491 
 1492 /*
 1493  * Dump immediate statistic snapshot of the scheduled callouts.
 1494  */
 1495 static int
 1496 sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
 1497 {
 1498         struct callout *tmp;
 1499         struct callout_cpu *cc;
 1500         struct callout_list *sc;
 1501         sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
 1502         int ct[64], cpr[64], ccpbk[32];
 1503         int error, val, i, count, tcum, pcum, maxc, c, medc;
 1504 #ifdef SMP
 1505         int cpu;
 1506 #endif
 1507 
 1508         val = 0;
 1509         error = sysctl_handle_int(oidp, &val, 0, req);
 1510         if (error != 0 || req->newptr == NULL)
 1511                 return (error);
 1512         count = maxc = 0;
 1513         st = spr = maxt = maxpr = 0;
 1514         bzero(ccpbk, sizeof(ccpbk));
 1515         bzero(ct, sizeof(ct));
 1516         bzero(cpr, sizeof(cpr));
 1517         now = sbinuptime();
 1518 #ifdef SMP
 1519         CPU_FOREACH(cpu) {
 1520                 cc = CC_CPU(cpu);
 1521 #else
 1522                 cc = CC_CPU(timeout_cpu);
 1523 #endif
 1524                 CC_LOCK(cc);
 1525                 for (i = 0; i < callwheelsize; i++) {
 1526                         sc = &cc->cc_callwheel[i];
 1527                         c = 0;
 1528                         LIST_FOREACH(tmp, sc, c_links.le) {
 1529                                 c++;
 1530                                 t = tmp->c_time - now;
 1531                                 if (t < 0)
 1532                                         t = 0;
 1533                                 st += t / SBT_1US;
 1534                                 spr += tmp->c_precision / SBT_1US;
 1535                                 if (t > maxt)
 1536                                         maxt = t;
 1537                                 if (tmp->c_precision > maxpr)
 1538                                         maxpr = tmp->c_precision;
 1539                                 ct[flssbt(t)]++;
 1540                                 cpr[flssbt(tmp->c_precision)]++;
 1541                         }
 1542                         if (c > maxc)
 1543                                 maxc = c;
 1544                         ccpbk[fls(c + c / 2)]++;
 1545                         count += c;
 1546                 }
 1547                 CC_UNLOCK(cc);
 1548 #ifdef SMP
 1549         }
 1550 #endif
 1551 
 1552         for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
 1553                 tcum += ct[i];
 1554         medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1555         for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
 1556                 pcum += cpr[i];
 1557         medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1558         for (i = 0, c = 0; i < 32 && c < count / 2; i++)
 1559                 c += ccpbk[i];
 1560         medc = (i >= 2) ? (1 << (i - 2)) : 0;
 1561 
 1562         printf("Scheduled callouts statistic snapshot:\n");
 1563         printf("  Callouts: %6d  Buckets: %6d*%-3d  Bucket size: 0.%06ds\n",
 1564             count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
 1565         printf("  C/Bk: med %5d         avg %6d.%06jd  max %6d\n",
 1566             medc,
 1567             count / callwheelsize / mp_ncpus,
 1568             (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
 1569             maxc);
 1570         printf("  Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1571             medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
 1572             (st / count) / 1000000, (st / count) % 1000000,
 1573             maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
 1574         printf("  Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1575             medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
 1576             (spr / count) / 1000000, (spr / count) % 1000000,
 1577             maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
 1578         printf("  Distribution:       \tbuckets\t   time\t   tcum\t"
 1579             "   prec\t   pcum\n");
 1580         for (i = 0, tcum = pcum = 0; i < 64; i++) {
 1581                 if (ct[i] == 0 && cpr[i] == 0)
 1582                         continue;
 1583                 t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
 1584                 tcum += ct[i];
 1585                 pcum += cpr[i];
 1586                 printf("  %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
 1587                     t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
 1588                     i - 1 - (32 - CC_HASH_SHIFT),
 1589                     ct[i], tcum, cpr[i], pcum);
 1590         }
 1591         return (error);
 1592 }
 1593 SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
 1594     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 1595     0, 0, sysctl_kern_callout_stat, "I",
 1596     "Dump immediate statistic snapshot of the scheduled callouts");

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