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 272757 2014-10-08 16:22:59Z jhb $");
   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_next;
  139         struct callout          *cc_curr;
  140 #ifdef SMP
  141         void                    (*ce_migration_func)(void *);
  142         void                    *ce_migration_arg;
  143         int                     ce_migration_cpu;
  144         sbintime_t              ce_migration_time;
  145         sbintime_t              ce_migration_prec;
  146 #endif
  147         bool                    cc_cancel;
  148         bool                    cc_waiting;
  149 };
  150 
  151 /*
  152  * There is one struct callout_cpu per cpu, holding all relevant
  153  * state for the callout processing thread on the individual CPU.
  154  */
  155 struct callout_cpu {
  156         struct mtx_padalign     cc_lock;
  157         struct cc_exec          cc_exec_entity[2];
  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         char                    cc_ktr_event_name[20];
  167 };
  168 
  169 #define cc_exec_curr            cc_exec_entity[0].cc_curr
  170 #define cc_exec_next            cc_exec_entity[0].cc_next
  171 #define cc_exec_cancel          cc_exec_entity[0].cc_cancel
  172 #define cc_exec_waiting         cc_exec_entity[0].cc_waiting
  173 #define cc_exec_curr_dir        cc_exec_entity[1].cc_curr
  174 #define cc_exec_next_dir        cc_exec_entity[1].cc_next
  175 #define cc_exec_cancel_dir      cc_exec_entity[1].cc_cancel
  176 #define cc_exec_waiting_dir     cc_exec_entity[1].cc_waiting
  177 
  178 #ifdef SMP
  179 #define cc_migration_func       cc_exec_entity[0].ce_migration_func
  180 #define cc_migration_arg        cc_exec_entity[0].ce_migration_arg
  181 #define cc_migration_cpu        cc_exec_entity[0].ce_migration_cpu
  182 #define cc_migration_time       cc_exec_entity[0].ce_migration_time
  183 #define cc_migration_prec       cc_exec_entity[0].ce_migration_prec
  184 #define cc_migration_func_dir   cc_exec_entity[1].ce_migration_func
  185 #define cc_migration_arg_dir    cc_exec_entity[1].ce_migration_arg
  186 #define cc_migration_cpu_dir    cc_exec_entity[1].ce_migration_cpu
  187 #define cc_migration_time_dir   cc_exec_entity[1].ce_migration_time
  188 #define cc_migration_prec_dir   cc_exec_entity[1].ce_migration_prec
  189 
  190 struct callout_cpu cc_cpu[MAXCPU];
  191 #define CPUBLOCK        MAXCPU
  192 #define CC_CPU(cpu)     (&cc_cpu[(cpu)])
  193 #define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
  194 #else
  195 struct callout_cpu cc_cpu;
  196 #define CC_CPU(cpu)     &cc_cpu
  197 #define CC_SELF()       &cc_cpu
  198 #endif
  199 #define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
  200 #define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)
  201 #define CC_LOCK_ASSERT(cc)      mtx_assert(&(cc)->cc_lock, MA_OWNED)
  202 
  203 static int timeout_cpu;
  204 
  205 static void     callout_cpu_init(struct callout_cpu *cc, int cpu);
  206 static void     softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  207 #ifdef CALLOUT_PROFILING
  208                     int *mpcalls, int *lockcalls, int *gcalls,
  209 #endif
  210                     int direct);
  211 
  212 static MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
  213 
  214 /**
  215  * Locked by cc_lock:
  216  *   cc_curr         - If a callout is in progress, it is cc_curr.
  217  *                     If cc_curr is non-NULL, threads waiting in
  218  *                     callout_drain() will be woken up as soon as the
  219  *                     relevant callout completes.
  220  *   cc_cancel       - Changing to 1 with both callout_lock and cc_lock held
  221  *                     guarantees that the current callout will not run.
  222  *                     The softclock() function sets this to 0 before it
  223  *                     drops callout_lock to acquire c_lock, and it calls
  224  *                     the handler only if curr_cancelled is still 0 after
  225  *                     cc_lock is successfully acquired.
  226  *   cc_waiting      - If a thread is waiting in callout_drain(), then
  227  *                     callout_wait is nonzero.  Set only when
  228  *                     cc_curr is non-NULL.
  229  */
  230 
  231 /*
  232  * Resets the execution entity tied to a specific callout cpu.
  233  */
  234 static void
  235 cc_cce_cleanup(struct callout_cpu *cc, int direct)
  236 {
  237 
  238         cc->cc_exec_entity[direct].cc_curr = NULL;
  239         cc->cc_exec_entity[direct].cc_next = NULL;
  240         cc->cc_exec_entity[direct].cc_cancel = false;
  241         cc->cc_exec_entity[direct].cc_waiting = false;
  242 #ifdef SMP
  243         cc->cc_exec_entity[direct].ce_migration_cpu = CPUBLOCK;
  244         cc->cc_exec_entity[direct].ce_migration_time = 0;
  245         cc->cc_exec_entity[direct].ce_migration_prec = 0;
  246         cc->cc_exec_entity[direct].ce_migration_func = NULL;
  247         cc->cc_exec_entity[direct].ce_migration_arg = NULL;
  248 #endif
  249 }
  250 
  251 /*
  252  * Checks if migration is requested by a specific callout cpu.
  253  */
  254 static int
  255 cc_cce_migrating(struct callout_cpu *cc, int direct)
  256 {
  257 
  258 #ifdef SMP
  259         return (cc->cc_exec_entity[direct].ce_migration_cpu != CPUBLOCK);
  260 #else
  261         return (0);
  262 #endif
  263 }
  264 
  265 /*
  266  * Kernel low level callwheel initialization
  267  * called on cpu0 during kernel startup.
  268  */
  269 static void
  270 callout_callwheel_init(void *dummy)
  271 {
  272         struct callout_cpu *cc;
  273 
  274         /*
  275          * Calculate the size of the callout wheel and the preallocated
  276          * timeout() structures.
  277          * XXX: Clip callout to result of previous function of maxusers
  278          * maximum 384.  This is still huge, but acceptable.
  279          */
  280         ncallout = imin(16 + maxproc + maxfiles, 18508);
  281         TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
  282 
  283         /*
  284          * Calculate callout wheel size, should be next power of two higher
  285          * than 'ncallout'.
  286          */
  287         callwheelsize = 1 << fls(ncallout);
  288         callwheelmask = callwheelsize - 1;
  289 
  290         /*
  291          * Fetch whether we're pinning the swi's or not.
  292          */
  293         TUNABLE_INT_FETCH("kern.pin_default_swi", &pin_default_swi);
  294         TUNABLE_INT_FETCH("kern.pin_pcpu_swi", &pin_pcpu_swi);
  295 
  296         /*
  297          * Only cpu0 handles timeout(9) and receives a preallocation.
  298          *
  299          * XXX: Once all timeout(9) consumers are converted this can
  300          * be removed.
  301          */
  302         timeout_cpu = PCPU_GET(cpuid);
  303         cc = CC_CPU(timeout_cpu);
  304         cc->cc_callout = malloc(ncallout * sizeof(struct callout),
  305             M_CALLOUT, M_WAITOK);
  306         callout_cpu_init(cc, timeout_cpu);
  307 }
  308 SYSINIT(callwheel_init, SI_SUB_CPU, SI_ORDER_ANY, callout_callwheel_init, NULL);
  309 
  310 /*
  311  * Initialize the per-cpu callout structures.
  312  */
  313 static void
  314 callout_cpu_init(struct callout_cpu *cc, int cpu)
  315 {
  316         struct callout *c;
  317         int i;
  318 
  319         mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
  320         SLIST_INIT(&cc->cc_callfree);
  321         cc->cc_callwheel = malloc(sizeof(struct callout_list) * callwheelsize,
  322             M_CALLOUT, M_WAITOK);
  323         for (i = 0; i < callwheelsize; i++)
  324                 LIST_INIT(&cc->cc_callwheel[i]);
  325         TAILQ_INIT(&cc->cc_expireq);
  326         cc->cc_firstevent = SBT_MAX;
  327         for (i = 0; i < 2; i++)
  328                 cc_cce_cleanup(cc, i);
  329         snprintf(cc->cc_ktr_event_name, sizeof(cc->cc_ktr_event_name),
  330             "callwheel cpu %d", cpu);
  331         if (cc->cc_callout == NULL)     /* Only cpu0 handles timeout(9) */
  332                 return;
  333         for (i = 0; i < ncallout; i++) {
  334                 c = &cc->cc_callout[i];
  335                 callout_init(c, 0);
  336                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  337                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  338         }
  339 }
  340 
  341 #ifdef SMP
  342 /*
  343  * Switches the cpu tied to a specific callout.
  344  * The function expects a locked incoming callout cpu and returns with
  345  * locked outcoming callout cpu.
  346  */
  347 static struct callout_cpu *
  348 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
  349 {
  350         struct callout_cpu *new_cc;
  351 
  352         MPASS(c != NULL && cc != NULL);
  353         CC_LOCK_ASSERT(cc);
  354 
  355         /*
  356          * Avoid interrupts and preemption firing after the callout cpu
  357          * is blocked in order to avoid deadlocks as the new thread
  358          * may be willing to acquire the callout cpu lock.
  359          */
  360         c->c_cpu = CPUBLOCK;
  361         spinlock_enter();
  362         CC_UNLOCK(cc);
  363         new_cc = CC_CPU(new_cpu);
  364         CC_LOCK(new_cc);
  365         spinlock_exit();
  366         c->c_cpu = new_cpu;
  367         return (new_cc);
  368 }
  369 #endif
  370 
  371 /*
  372  * Start standard softclock thread.
  373  */
  374 static void
  375 start_softclock(void *dummy)
  376 {
  377         struct callout_cpu *cc;
  378         char name[MAXCOMLEN];
  379 #ifdef SMP
  380         int cpu;
  381         struct intr_event *ie;
  382 #endif
  383 
  384         cc = CC_CPU(timeout_cpu);
  385         snprintf(name, sizeof(name), "clock (%d)", timeout_cpu);
  386         if (swi_add(&clk_intr_event, name, softclock, cc, SWI_CLOCK,
  387             INTR_MPSAFE, &cc->cc_cookie))
  388                 panic("died while creating standard software ithreads");
  389         if (pin_default_swi &&
  390             (intr_event_bind(clk_intr_event, timeout_cpu) != 0)) {
  391                 printf("%s: timeout clock couldn't be pinned to cpu %d\n",
  392                     __func__,
  393                     timeout_cpu);
  394         }
  395 
  396 #ifdef SMP
  397         CPU_FOREACH(cpu) {
  398                 if (cpu == timeout_cpu)
  399                         continue;
  400                 cc = CC_CPU(cpu);
  401                 cc->cc_callout = NULL;  /* Only cpu0 handles timeout(9). */
  402                 callout_cpu_init(cc, cpu);
  403                 snprintf(name, sizeof(name), "clock (%d)", cpu);
  404                 ie = NULL;
  405                 if (swi_add(&ie, name, softclock, cc, SWI_CLOCK,
  406                     INTR_MPSAFE, &cc->cc_cookie))
  407                         panic("died while creating standard software ithreads");
  408                 if (pin_pcpu_swi && (intr_event_bind(ie, cpu) != 0)) {
  409                         printf("%s: per-cpu clock couldn't be pinned to "
  410                             "cpu %d\n",
  411                             __func__,
  412                             cpu);
  413                 }
  414         }
  415 #endif
  416 }
  417 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
  418 
  419 #define CC_HASH_SHIFT   8
  420 
  421 static inline u_int
  422 callout_hash(sbintime_t sbt)
  423 {
  424 
  425         return (sbt >> (32 - CC_HASH_SHIFT));
  426 }
  427 
  428 static inline u_int
  429 callout_get_bucket(sbintime_t sbt)
  430 {
  431 
  432         return (callout_hash(sbt) & callwheelmask);
  433 }
  434 
  435 void
  436 callout_process(sbintime_t now)
  437 {
  438         struct callout *tmp, *tmpn;
  439         struct callout_cpu *cc;
  440         struct callout_list *sc;
  441         sbintime_t first, last, max, tmp_max;
  442         uint32_t lookahead;
  443         u_int firstb, lastb, nowb;
  444 #ifdef CALLOUT_PROFILING
  445         int depth_dir = 0, mpcalls_dir = 0, lockcalls_dir = 0;
  446 #endif
  447 
  448         cc = CC_SELF();
  449         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  450 
  451         /* Compute the buckets of the last scan and present times. */
  452         firstb = callout_hash(cc->cc_lastscan);
  453         cc->cc_lastscan = now;
  454         nowb = callout_hash(now);
  455 
  456         /* Compute the last bucket and minimum time of the bucket after it. */
  457         if (nowb == firstb)
  458                 lookahead = (SBT_1S / 16);
  459         else if (nowb - firstb == 1)
  460                 lookahead = (SBT_1S / 8);
  461         else
  462                 lookahead = (SBT_1S / 2);
  463         first = last = now;
  464         first += (lookahead / 2);
  465         last += lookahead;
  466         last &= (0xffffffffffffffffLLU << (32 - CC_HASH_SHIFT));
  467         lastb = callout_hash(last) - 1;
  468         max = last;
  469 
  470         /*
  471          * Check if we wrapped around the entire wheel from the last scan.
  472          * In case, we need to scan entirely the wheel for pending callouts.
  473          */
  474         if (lastb - firstb >= callwheelsize) {
  475                 lastb = firstb + callwheelsize - 1;
  476                 if (nowb - firstb >= callwheelsize)
  477                         nowb = lastb;
  478         }
  479 
  480         /* Iterate callwheel from firstb to nowb and then up to lastb. */
  481         do {
  482                 sc = &cc->cc_callwheel[firstb & callwheelmask];
  483                 tmp = LIST_FIRST(sc);
  484                 while (tmp != NULL) {
  485                         /* Run the callout if present time within allowed. */
  486                         if (tmp->c_time <= now) {
  487                                 /*
  488                                  * Consumer told us the callout may be run
  489                                  * directly from hardware interrupt context.
  490                                  */
  491                                 if (tmp->c_flags & CALLOUT_DIRECT) {
  492 #ifdef CALLOUT_PROFILING
  493                                         ++depth_dir;
  494 #endif
  495                                         cc->cc_exec_next_dir =
  496                                             LIST_NEXT(tmp, c_links.le);
  497                                         cc->cc_bucket = firstb & callwheelmask;
  498                                         LIST_REMOVE(tmp, c_links.le);
  499                                         softclock_call_cc(tmp, cc,
  500 #ifdef CALLOUT_PROFILING
  501                                             &mpcalls_dir, &lockcalls_dir, NULL,
  502 #endif
  503                                             1);
  504                                         tmp = cc->cc_exec_next_dir;
  505                                 } else {
  506                                         tmpn = LIST_NEXT(tmp, c_links.le);
  507                                         LIST_REMOVE(tmp, c_links.le);
  508                                         TAILQ_INSERT_TAIL(&cc->cc_expireq,
  509                                             tmp, c_links.tqe);
  510                                         tmp->c_flags |= CALLOUT_PROCESSED;
  511                                         tmp = tmpn;
  512                                 }
  513                                 continue;
  514                         }
  515                         /* Skip events from distant future. */
  516                         if (tmp->c_time >= max)
  517                                 goto next;
  518                         /*
  519                          * Event minimal time is bigger than present maximal
  520                          * time, so it cannot be aggregated.
  521                          */
  522                         if (tmp->c_time > last) {
  523                                 lastb = nowb;
  524                                 goto next;
  525                         }
  526                         /* Update first and last time, respecting this event. */
  527                         if (tmp->c_time < first)
  528                                 first = tmp->c_time;
  529                         tmp_max = tmp->c_time + tmp->c_precision;
  530                         if (tmp_max < last)
  531                                 last = tmp_max;
  532 next:
  533                         tmp = LIST_NEXT(tmp, c_links.le);
  534                 }
  535                 /* Proceed with the next bucket. */
  536                 firstb++;
  537                 /*
  538                  * Stop if we looked after present time and found
  539                  * some event we can't execute at now.
  540                  * Stop if we looked far enough into the future.
  541                  */
  542         } while (((int)(firstb - lastb)) <= 0);
  543         cc->cc_firstevent = last;
  544 #ifndef NO_EVENTTIMERS
  545         cpu_new_callout(curcpu, last, first);
  546 #endif
  547 #ifdef CALLOUT_PROFILING
  548         avg_depth_dir += (depth_dir * 1000 - avg_depth_dir) >> 8;
  549         avg_mpcalls_dir += (mpcalls_dir * 1000 - avg_mpcalls_dir) >> 8;
  550         avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
  551 #endif
  552         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  553         /*
  554          * swi_sched acquires the thread lock, so we don't want to call it
  555          * with cc_lock held; incorrect locking order.
  556          */
  557         if (!TAILQ_EMPTY(&cc->cc_expireq))
  558                 swi_sched(cc->cc_cookie, 0);
  559 }
  560 
  561 static struct callout_cpu *
  562 callout_lock(struct callout *c)
  563 {
  564         struct callout_cpu *cc;
  565         int cpu;
  566 
  567         for (;;) {
  568                 cpu = c->c_cpu;
  569 #ifdef SMP
  570                 if (cpu == CPUBLOCK) {
  571                         while (c->c_cpu == CPUBLOCK)
  572                                 cpu_spinwait();
  573                         continue;
  574                 }
  575 #endif
  576                 cc = CC_CPU(cpu);
  577                 CC_LOCK(cc);
  578                 if (cpu == c->c_cpu)
  579                         break;
  580                 CC_UNLOCK(cc);
  581         }
  582         return (cc);
  583 }
  584 
  585 static void
  586 callout_cc_add(struct callout *c, struct callout_cpu *cc,
  587     sbintime_t sbt, sbintime_t precision, void (*func)(void *),
  588     void *arg, int cpu, int flags)
  589 {
  590         int bucket;
  591 
  592         CC_LOCK_ASSERT(cc);
  593         if (sbt < cc->cc_lastscan)
  594                 sbt = cc->cc_lastscan;
  595         c->c_arg = arg;
  596         c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
  597         if (flags & C_DIRECT_EXEC)
  598                 c->c_flags |= CALLOUT_DIRECT;
  599         c->c_flags &= ~CALLOUT_PROCESSED;
  600         c->c_func = func;
  601         c->c_time = sbt;
  602         c->c_precision = precision;
  603         bucket = callout_get_bucket(c->c_time);
  604         CTR3(KTR_CALLOUT, "precision set for %p: %d.%08x",
  605             c, (int)(c->c_precision >> 32),
  606             (u_int)(c->c_precision & 0xffffffff));
  607         LIST_INSERT_HEAD(&cc->cc_callwheel[bucket], c, c_links.le);
  608         if (cc->cc_bucket == bucket)
  609                 cc->cc_exec_next_dir = c;
  610 #ifndef NO_EVENTTIMERS
  611         /*
  612          * Inform the eventtimers(4) subsystem there's a new callout
  613          * that has been inserted, but only if really required.
  614          */
  615         if (SBT_MAX - c->c_time < c->c_precision)
  616                 c->c_precision = SBT_MAX - c->c_time;
  617         sbt = c->c_time + c->c_precision;
  618         if (sbt < cc->cc_firstevent) {
  619                 cc->cc_firstevent = sbt;
  620                 cpu_new_callout(cpu, sbt, c->c_time);
  621         }
  622 #endif
  623 }
  624 
  625 static void
  626 callout_cc_del(struct callout *c, struct callout_cpu *cc)
  627 {
  628 
  629         if ((c->c_flags & CALLOUT_LOCAL_ALLOC) == 0)
  630                 return;
  631         c->c_func = NULL;
  632         SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  633 }
  634 
  635 static void
  636 softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  637 #ifdef CALLOUT_PROFILING
  638     int *mpcalls, int *lockcalls, int *gcalls,
  639 #endif
  640     int direct)
  641 {
  642         struct rm_priotracker tracker;
  643         void (*c_func)(void *);
  644         void *c_arg;
  645         struct lock_class *class;
  646         struct lock_object *c_lock;
  647         uintptr_t lock_status;
  648         int c_flags;
  649 #ifdef SMP
  650         struct callout_cpu *new_cc;
  651         void (*new_func)(void *);
  652         void *new_arg;
  653         int flags, new_cpu;
  654         sbintime_t new_prec, new_time;
  655 #endif
  656 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING) 
  657         sbintime_t sbt1, sbt2;
  658         struct timespec ts2;
  659         static sbintime_t maxdt = 2 * SBT_1MS;  /* 2 msec */
  660         static timeout_t *lastfunc;
  661 #endif
  662 
  663         KASSERT((c->c_flags & (CALLOUT_PENDING | CALLOUT_ACTIVE)) ==
  664             (CALLOUT_PENDING | CALLOUT_ACTIVE),
  665             ("softclock_call_cc: pend|act %p %x", c, c->c_flags));
  666         class = (c->c_lock != NULL) ? LOCK_CLASS(c->c_lock) : NULL;
  667         lock_status = 0;
  668         if (c->c_flags & CALLOUT_SHAREDLOCK) {
  669                 if (class == &lock_class_rm)
  670                         lock_status = (uintptr_t)&tracker;
  671                 else
  672                         lock_status = 1;
  673         }
  674         c_lock = c->c_lock;
  675         c_func = c->c_func;
  676         c_arg = c->c_arg;
  677         c_flags = c->c_flags;
  678         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
  679                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  680         else
  681                 c->c_flags &= ~CALLOUT_PENDING;
  682         cc->cc_exec_entity[direct].cc_curr = c;
  683         cc->cc_exec_entity[direct].cc_cancel = false;
  684         CC_UNLOCK(cc);
  685         if (c_lock != NULL) {
  686                 class->lc_lock(c_lock, lock_status);
  687                 /*
  688                  * The callout may have been cancelled
  689                  * while we switched locks.
  690                  */
  691                 if (cc->cc_exec_entity[direct].cc_cancel) {
  692                         class->lc_unlock(c_lock);
  693                         goto skip;
  694                 }
  695                 /* The callout cannot be stopped now. */
  696                 cc->cc_exec_entity[direct].cc_cancel = true;
  697                 if (c_lock == &Giant.lock_object) {
  698 #ifdef CALLOUT_PROFILING
  699                         (*gcalls)++;
  700 #endif
  701                         CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
  702                             c, c_func, c_arg);
  703                 } else {
  704 #ifdef CALLOUT_PROFILING
  705                         (*lockcalls)++;
  706 #endif
  707                         CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
  708                             c, c_func, c_arg);
  709                 }
  710         } else {
  711 #ifdef CALLOUT_PROFILING
  712                 (*mpcalls)++;
  713 #endif
  714                 CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
  715                     c, c_func, c_arg);
  716         }
  717         KTR_STATE3(KTR_SCHED, "callout", cc->cc_ktr_event_name, "running",
  718             "func:%p", c_func, "arg:%p", c_arg, "direct:%d", direct);
  719 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  720         sbt1 = sbinuptime();
  721 #endif
  722         THREAD_NO_SLEEPING();
  723         SDT_PROBE(callout_execute, kernel, , callout__start, c, 0, 0, 0, 0);
  724         c_func(c_arg);
  725         SDT_PROBE(callout_execute, kernel, , callout__end, c, 0, 0, 0, 0);
  726         THREAD_SLEEPING_OK();
  727 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  728         sbt2 = sbinuptime();
  729         sbt2 -= sbt1;
  730         if (sbt2 > maxdt) {
  731                 if (lastfunc != c_func || sbt2 > maxdt * 2) {
  732                         ts2 = sbttots(sbt2);
  733                         printf(
  734                 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  735                             c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
  736                 }
  737                 maxdt = sbt2;
  738                 lastfunc = c_func;
  739         }
  740 #endif
  741         KTR_STATE0(KTR_SCHED, "callout", cc->cc_ktr_event_name, "idle");
  742         CTR1(KTR_CALLOUT, "callout %p finished", c);
  743         if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
  744                 class->lc_unlock(c_lock);
  745 skip:
  746         CC_LOCK(cc);
  747         KASSERT(cc->cc_exec_entity[direct].cc_curr == c, ("mishandled cc_curr"));
  748         cc->cc_exec_entity[direct].cc_curr = NULL;
  749         if (cc->cc_exec_entity[direct].cc_waiting) {
  750                 /*
  751                  * There is someone waiting for the
  752                  * callout to complete.
  753                  * If the callout was scheduled for
  754                  * migration just cancel it.
  755                  */
  756                 if (cc_cce_migrating(cc, direct)) {
  757                         cc_cce_cleanup(cc, direct);
  758 
  759                         /*
  760                          * It should be assert here that the callout is not
  761                          * destroyed but that is not easy.
  762                          */
  763                         c->c_flags &= ~CALLOUT_DFRMIGRATION;
  764                 }
  765                 cc->cc_exec_entity[direct].cc_waiting = false;
  766                 CC_UNLOCK(cc);
  767                 wakeup(&cc->cc_exec_entity[direct].cc_waiting);
  768                 CC_LOCK(cc);
  769         } else if (cc_cce_migrating(cc, direct)) {
  770                 KASSERT((c_flags & CALLOUT_LOCAL_ALLOC) == 0,
  771                     ("Migrating legacy callout %p", c));
  772 #ifdef SMP
  773                 /*
  774                  * If the callout was scheduled for
  775                  * migration just perform it now.
  776                  */
  777                 new_cpu = cc->cc_exec_entity[direct].ce_migration_cpu;
  778                 new_time = cc->cc_exec_entity[direct].ce_migration_time;
  779                 new_prec = cc->cc_exec_entity[direct].ce_migration_prec;
  780                 new_func = cc->cc_exec_entity[direct].ce_migration_func;
  781                 new_arg = cc->cc_exec_entity[direct].ce_migration_arg;
  782                 cc_cce_cleanup(cc, direct);
  783 
  784                 /*
  785                  * It should be assert here that the callout is not destroyed
  786                  * but that is not easy.
  787                  *
  788                  * As first thing, handle deferred callout stops.
  789                  */
  790                 if ((c->c_flags & CALLOUT_DFRMIGRATION) == 0) {
  791                         CTR3(KTR_CALLOUT,
  792                              "deferred cancelled %p func %p arg %p",
  793                              c, new_func, new_arg);
  794                         callout_cc_del(c, cc);
  795                         return;
  796                 }
  797                 c->c_flags &= ~CALLOUT_DFRMIGRATION;
  798 
  799                 new_cc = callout_cpu_switch(c, cc, new_cpu);
  800                 flags = (direct) ? C_DIRECT_EXEC : 0;
  801                 callout_cc_add(c, new_cc, new_time, new_prec, new_func,
  802                     new_arg, new_cpu, flags);
  803                 CC_UNLOCK(new_cc);
  804                 CC_LOCK(cc);
  805 #else
  806                 panic("migration should not happen");
  807 #endif
  808         }
  809         /*
  810          * If the current callout is locally allocated (from
  811          * timeout(9)) then put it on the freelist.
  812          *
  813          * Note: we need to check the cached copy of c_flags because
  814          * if it was not local, then it's not safe to deref the
  815          * callout pointer.
  816          */
  817         KASSERT((c_flags & CALLOUT_LOCAL_ALLOC) == 0 ||
  818             c->c_flags == CALLOUT_LOCAL_ALLOC,
  819             ("corrupted callout"));
  820         if (c_flags & CALLOUT_LOCAL_ALLOC)
  821                 callout_cc_del(c, cc);
  822 }
  823 
  824 /*
  825  * The callout mechanism is based on the work of Adam M. Costello and
  826  * George Varghese, published in a technical report entitled "Redesigning
  827  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  828  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  829  * used in this implementation was published by G. Varghese and T. Lauck in
  830  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  831  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  832  * the 11th ACM Annual Symposium on Operating Systems Principles,
  833  * Austin, Texas Nov 1987.
  834  */
  835 
  836 /*
  837  * Software (low priority) clock interrupt.
  838  * Run periodic events from timeout queue.
  839  */
  840 void
  841 softclock(void *arg)
  842 {
  843         struct callout_cpu *cc;
  844         struct callout *c;
  845 #ifdef CALLOUT_PROFILING
  846         int depth = 0, gcalls = 0, lockcalls = 0, mpcalls = 0;
  847 #endif
  848 
  849         cc = (struct callout_cpu *)arg;
  850         CC_LOCK(cc);
  851         while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
  852                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
  853                 softclock_call_cc(c, cc,
  854 #ifdef CALLOUT_PROFILING
  855                     &mpcalls, &lockcalls, &gcalls,
  856 #endif
  857                     0);
  858 #ifdef CALLOUT_PROFILING
  859                 ++depth;
  860 #endif
  861         }
  862 #ifdef CALLOUT_PROFILING
  863         avg_depth += (depth * 1000 - avg_depth) >> 8;
  864         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  865         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  866         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  867 #endif
  868         CC_UNLOCK(cc);
  869 }
  870 
  871 /*
  872  * timeout --
  873  *      Execute a function after a specified length of time.
  874  *
  875  * untimeout --
  876  *      Cancel previous timeout function call.
  877  *
  878  * callout_handle_init --
  879  *      Initialize a handle so that using it with untimeout is benign.
  880  *
  881  *      See AT&T BCI Driver Reference Manual for specification.  This
  882  *      implementation differs from that one in that although an
  883  *      identification value is returned from timeout, the original
  884  *      arguments to timeout as well as the identifier are used to
  885  *      identify entries for untimeout.
  886  */
  887 struct callout_handle
  888 timeout(timeout_t *ftn, void *arg, int to_ticks)
  889 {
  890         struct callout_cpu *cc;
  891         struct callout *new;
  892         struct callout_handle handle;
  893 
  894         cc = CC_CPU(timeout_cpu);
  895         CC_LOCK(cc);
  896         /* Fill in the next free callout structure. */
  897         new = SLIST_FIRST(&cc->cc_callfree);
  898         if (new == NULL)
  899                 /* XXX Attempt to malloc first */
  900                 panic("timeout table full");
  901         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  902         callout_reset(new, to_ticks, ftn, arg);
  903         handle.callout = new;
  904         CC_UNLOCK(cc);
  905 
  906         return (handle);
  907 }
  908 
  909 void
  910 untimeout(timeout_t *ftn, void *arg, struct callout_handle handle)
  911 {
  912         struct callout_cpu *cc;
  913 
  914         /*
  915          * Check for a handle that was initialized
  916          * by callout_handle_init, but never used
  917          * for a real timeout.
  918          */
  919         if (handle.callout == NULL)
  920                 return;
  921 
  922         cc = callout_lock(handle.callout);
  923         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  924                 callout_stop(handle.callout);
  925         CC_UNLOCK(cc);
  926 }
  927 
  928 void
  929 callout_handle_init(struct callout_handle *handle)
  930 {
  931         handle->callout = NULL;
  932 }
  933 
  934 /*
  935  * New interface; clients allocate their own callout structures.
  936  *
  937  * callout_reset() - establish or change a timeout
  938  * callout_stop() - disestablish a timeout
  939  * callout_init() - initialize a callout structure so that it can
  940  *      safely be passed to callout_reset() and callout_stop()
  941  *
  942  * <sys/callout.h> defines three convenience macros:
  943  *
  944  * callout_active() - returns truth if callout has not been stopped,
  945  *      drained, or deactivated since the last time the callout was
  946  *      reset.
  947  * callout_pending() - returns truth if callout is still waiting for timeout
  948  * callout_deactivate() - marks the callout as having been serviced
  949  */
  950 int
  951 callout_reset_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t precision,
  952     void (*ftn)(void *), void *arg, int cpu, int flags)
  953 {
  954         sbintime_t to_sbt, pr;
  955         struct callout_cpu *cc;
  956         int cancelled, direct;
  957 
  958         cancelled = 0;
  959         if (flags & C_ABSOLUTE) {
  960                 to_sbt = sbt;
  961         } else {
  962                 if ((flags & C_HARDCLOCK) && (sbt < tick_sbt))
  963                         sbt = tick_sbt;
  964                 if ((flags & C_HARDCLOCK) ||
  965 #ifdef NO_EVENTTIMERS
  966                     sbt >= sbt_timethreshold) {
  967                         to_sbt = getsbinuptime();
  968 
  969                         /* Add safety belt for the case of hz > 1000. */
  970                         to_sbt += tc_tick_sbt - tick_sbt;
  971 #else
  972                     sbt >= sbt_tickthreshold) {
  973                         /*
  974                          * Obtain the time of the last hardclock() call on
  975                          * this CPU directly from the kern_clocksource.c.
  976                          * This value is per-CPU, but it is equal for all
  977                          * active ones.
  978                          */
  979 #ifdef __LP64__
  980                         to_sbt = DPCPU_GET(hardclocktime);
  981 #else
  982                         spinlock_enter();
  983                         to_sbt = DPCPU_GET(hardclocktime);
  984                         spinlock_exit();
  985 #endif
  986 #endif
  987                         if ((flags & C_HARDCLOCK) == 0)
  988                                 to_sbt += tick_sbt;
  989                 } else
  990                         to_sbt = sbinuptime();
  991                 if (SBT_MAX - to_sbt < sbt)
  992                         to_sbt = SBT_MAX;
  993                 else
  994                         to_sbt += sbt;
  995                 pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
  996                     sbt >> C_PRELGET(flags));
  997                 if (pr > precision)
  998                         precision = pr;
  999         }
 1000         /*
 1001          * Don't allow migration of pre-allocated callouts lest they
 1002          * become unbalanced.
 1003          */
 1004         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
 1005                 cpu = c->c_cpu;
 1006         direct = (c->c_flags & CALLOUT_DIRECT) != 0;
 1007         KASSERT(!direct || c->c_lock == NULL,
 1008             ("%s: direct callout %p has lock", __func__, c));
 1009         cc = callout_lock(c);
 1010         if (cc->cc_exec_entity[direct].cc_curr == c) {
 1011                 /*
 1012                  * We're being asked to reschedule a callout which is
 1013                  * currently in progress.  If there is a lock then we
 1014                  * can cancel the callout if it has not really started.
 1015                  */
 1016                 if (c->c_lock != NULL && !cc->cc_exec_entity[direct].cc_cancel)
 1017                         cancelled = cc->cc_exec_entity[direct].cc_cancel = true;
 1018                 if (cc->cc_exec_entity[direct].cc_waiting) {
 1019                         /*
 1020                          * Someone has called callout_drain to kill this
 1021                          * callout.  Don't reschedule.
 1022                          */
 1023                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
 1024                             cancelled ? "cancelled" : "failed to cancel",
 1025                             c, c->c_func, c->c_arg);
 1026                         CC_UNLOCK(cc);
 1027                         return (cancelled);
 1028                 }
 1029         }
 1030         if (c->c_flags & CALLOUT_PENDING) {
 1031                 if ((c->c_flags & CALLOUT_PROCESSED) == 0) {
 1032                         if (cc->cc_exec_next_dir == c)
 1033                                 cc->cc_exec_next_dir = LIST_NEXT(c, c_links.le);
 1034                         LIST_REMOVE(c, c_links.le);
 1035                 } else
 1036                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1037                 cancelled = 1;
 1038                 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
 1039         }
 1040 
 1041 #ifdef SMP
 1042         /*
 1043          * If the callout must migrate try to perform it immediately.
 1044          * If the callout is currently running, just defer the migration
 1045          * to a more appropriate moment.
 1046          */
 1047         if (c->c_cpu != cpu) {
 1048                 if (cc->cc_exec_entity[direct].cc_curr == c) {
 1049                         cc->cc_exec_entity[direct].ce_migration_cpu = cpu;
 1050                         cc->cc_exec_entity[direct].ce_migration_time
 1051                             = to_sbt;
 1052                         cc->cc_exec_entity[direct].ce_migration_prec 
 1053                             = precision;
 1054                         cc->cc_exec_entity[direct].ce_migration_func = ftn;
 1055                         cc->cc_exec_entity[direct].ce_migration_arg = arg;
 1056                         c->c_flags |= CALLOUT_DFRMIGRATION;
 1057                         CTR6(KTR_CALLOUT,
 1058                     "migration of %p func %p arg %p in %d.%08x to %u deferred",
 1059                             c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1060                             (u_int)(to_sbt & 0xffffffff), cpu);
 1061                         CC_UNLOCK(cc);
 1062                         return (cancelled);
 1063                 }
 1064                 cc = callout_cpu_switch(c, cc, cpu);
 1065         }
 1066 #endif
 1067 
 1068         callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
 1069         CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
 1070             cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1071             (u_int)(to_sbt & 0xffffffff));
 1072         CC_UNLOCK(cc);
 1073 
 1074         return (cancelled);
 1075 }
 1076 
 1077 /*
 1078  * Common idioms that can be optimized in the future.
 1079  */
 1080 int
 1081 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
 1082 {
 1083         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
 1084 }
 1085 
 1086 int
 1087 callout_schedule(struct callout *c, int to_ticks)
 1088 {
 1089         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
 1090 }
 1091 
 1092 int
 1093 _callout_stop_safe(struct callout *c, int safe)
 1094 {
 1095         struct callout_cpu *cc, *old_cc;
 1096         struct lock_class *class;
 1097         int direct, sq_locked, use_lock;
 1098 
 1099         /*
 1100          * Some old subsystems don't hold Giant while running a callout_stop(),
 1101          * so just discard this check for the moment.
 1102          */
 1103         if (!safe && c->c_lock != NULL) {
 1104                 if (c->c_lock == &Giant.lock_object)
 1105                         use_lock = mtx_owned(&Giant);
 1106                 else {
 1107                         use_lock = 1;
 1108                         class = LOCK_CLASS(c->c_lock);
 1109                         class->lc_assert(c->c_lock, LA_XLOCKED);
 1110                 }
 1111         } else
 1112                 use_lock = 0;
 1113         direct = (c->c_flags & CALLOUT_DIRECT) != 0;
 1114         sq_locked = 0;
 1115         old_cc = NULL;
 1116 again:
 1117         cc = callout_lock(c);
 1118 
 1119         /*
 1120          * If the callout was migrating while the callout cpu lock was
 1121          * dropped,  just drop the sleepqueue lock and check the states
 1122          * again.
 1123          */
 1124         if (sq_locked != 0 && cc != old_cc) {
 1125 #ifdef SMP
 1126                 CC_UNLOCK(cc);
 1127                 sleepq_release(&old_cc->cc_exec_entity[direct].cc_waiting);
 1128                 sq_locked = 0;
 1129                 old_cc = NULL;
 1130                 goto again;
 1131 #else
 1132                 panic("migration should not happen");
 1133 #endif
 1134         }
 1135 
 1136         /*
 1137          * If the callout isn't pending, it's not on the queue, so
 1138          * don't attempt to remove it from the queue.  We can try to
 1139          * stop it by other means however.
 1140          */
 1141         if (!(c->c_flags & CALLOUT_PENDING)) {
 1142                 c->c_flags &= ~CALLOUT_ACTIVE;
 1143 
 1144                 /*
 1145                  * If it wasn't on the queue and it isn't the current
 1146                  * callout, then we can't stop it, so just bail.
 1147                  */
 1148                 if (cc->cc_exec_entity[direct].cc_curr != c) {
 1149                         CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1150                             c, c->c_func, c->c_arg);
 1151                         CC_UNLOCK(cc);
 1152                         if (sq_locked)
 1153                                 sleepq_release(
 1154                                     &cc->cc_exec_entity[direct].cc_waiting);
 1155                         return (0);
 1156                 }
 1157 
 1158                 if (safe) {
 1159                         /*
 1160                          * The current callout is running (or just
 1161                          * about to run) and blocking is allowed, so
 1162                          * just wait for the current invocation to
 1163                          * finish.
 1164                          */
 1165                         while (cc->cc_exec_entity[direct].cc_curr == c) {
 1166                                 /*
 1167                                  * Use direct calls to sleepqueue interface
 1168                                  * instead of cv/msleep in order to avoid
 1169                                  * a LOR between cc_lock and sleepqueue
 1170                                  * chain spinlocks.  This piece of code
 1171                                  * emulates a msleep_spin() call actually.
 1172                                  *
 1173                                  * If we already have the sleepqueue chain
 1174                                  * locked, then we can safely block.  If we
 1175                                  * don't already have it locked, however,
 1176                                  * we have to drop the cc_lock to lock
 1177                                  * it.  This opens several races, so we
 1178                                  * restart at the beginning once we have
 1179                                  * both locks.  If nothing has changed, then
 1180                                  * we will end up back here with sq_locked
 1181                                  * set.
 1182                                  */
 1183                                 if (!sq_locked) {
 1184                                         CC_UNLOCK(cc);
 1185                                         sleepq_lock(
 1186                                         &cc->cc_exec_entity[direct].cc_waiting);
 1187                                         sq_locked = 1;
 1188                                         old_cc = cc;
 1189                                         goto again;
 1190                                 }
 1191 
 1192                                 /*
 1193                                  * Migration could be cancelled here, but
 1194                                  * as long as it is still not sure when it
 1195                                  * will be packed up, just let softclock()
 1196                                  * take care of it.
 1197                                  */
 1198                                 cc->cc_exec_entity[direct].cc_waiting = true;
 1199                                 DROP_GIANT();
 1200                                 CC_UNLOCK(cc);
 1201                                 sleepq_add(
 1202                                     &cc->cc_exec_entity[direct].cc_waiting,
 1203                                     &cc->cc_lock.lock_object, "codrain",
 1204                                     SLEEPQ_SLEEP, 0);
 1205                                 sleepq_wait(
 1206                                     &cc->cc_exec_entity[direct].cc_waiting,
 1207                                              0);
 1208                                 sq_locked = 0;
 1209                                 old_cc = NULL;
 1210 
 1211                                 /* Reacquire locks previously released. */
 1212                                 PICKUP_GIANT();
 1213                                 CC_LOCK(cc);
 1214                         }
 1215                 } else if (use_lock &&
 1216                             !cc->cc_exec_entity[direct].cc_cancel) {
 1217                         /*
 1218                          * The current callout is waiting for its
 1219                          * lock which we hold.  Cancel the callout
 1220                          * and return.  After our caller drops the
 1221                          * lock, the callout will be skipped in
 1222                          * softclock().
 1223                          */
 1224                         cc->cc_exec_entity[direct].cc_cancel = true;
 1225                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1226                             c, c->c_func, c->c_arg);
 1227                         KASSERT(!cc_cce_migrating(cc, direct),
 1228                             ("callout wrongly scheduled for migration"));
 1229                         CC_UNLOCK(cc);
 1230                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
 1231                         return (1);
 1232                 } else if ((c->c_flags & CALLOUT_DFRMIGRATION) != 0) {
 1233                         c->c_flags &= ~CALLOUT_DFRMIGRATION;
 1234                         CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
 1235                             c, c->c_func, c->c_arg);
 1236                         CC_UNLOCK(cc);
 1237                         return (1);
 1238                 }
 1239                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1240                     c, c->c_func, c->c_arg);
 1241                 CC_UNLOCK(cc);
 1242                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
 1243                 return (0);
 1244         }
 1245         if (sq_locked)
 1246                 sleepq_release(&cc->cc_exec_entity[direct].cc_waiting);
 1247 
 1248         c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
 1249 
 1250         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1251             c, c->c_func, c->c_arg);
 1252         if ((c->c_flags & CALLOUT_PROCESSED) == 0) {
 1253                 if (cc->cc_exec_next_dir == c)
 1254                         cc->cc_exec_next_dir = LIST_NEXT(c, c_links.le);
 1255                 LIST_REMOVE(c, c_links.le);
 1256         } else
 1257                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1258         callout_cc_del(c, cc);
 1259 
 1260         CC_UNLOCK(cc);
 1261         return (1);
 1262 }
 1263 
 1264 void
 1265 callout_init(struct callout *c, int mpsafe)
 1266 {
 1267         bzero(c, sizeof *c);
 1268         if (mpsafe) {
 1269                 c->c_lock = NULL;
 1270                 c->c_flags = CALLOUT_RETURNUNLOCKED;
 1271         } else {
 1272                 c->c_lock = &Giant.lock_object;
 1273                 c->c_flags = 0;
 1274         }
 1275         c->c_cpu = timeout_cpu;
 1276 }
 1277 
 1278 void
 1279 _callout_init_lock(struct callout *c, struct lock_object *lock, int flags)
 1280 {
 1281         bzero(c, sizeof *c);
 1282         c->c_lock = lock;
 1283         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
 1284             ("callout_init_lock: bad flags %d", flags));
 1285         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
 1286             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
 1287         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
 1288             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
 1289             __func__));
 1290         c->c_flags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
 1291         c->c_cpu = timeout_cpu;
 1292 }
 1293 
 1294 #ifdef APM_FIXUP_CALLTODO
 1295 /* 
 1296  * Adjust the kernel calltodo timeout list.  This routine is used after 
 1297  * an APM resume to recalculate the calltodo timer list values with the 
 1298  * number of hz's we have been sleeping.  The next hardclock() will detect 
 1299  * that there are fired timers and run softclock() to execute them.
 1300  *
 1301  * Please note, I have not done an exhaustive analysis of what code this
 1302  * might break.  I am motivated to have my select()'s and alarm()'s that
 1303  * have expired during suspend firing upon resume so that the applications
 1304  * which set the timer can do the maintanence the timer was for as close
 1305  * as possible to the originally intended time.  Testing this code for a 
 1306  * week showed that resuming from a suspend resulted in 22 to 25 timers 
 1307  * firing, which seemed independant on whether the suspend was 2 hours or
 1308  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 1309  */
 1310 void
 1311 adjust_timeout_calltodo(struct timeval *time_change)
 1312 {
 1313         register struct callout *p;
 1314         unsigned long delta_ticks;
 1315 
 1316         /* 
 1317          * How many ticks were we asleep?
 1318          * (stolen from tvtohz()).
 1319          */
 1320 
 1321         /* Don't do anything */
 1322         if (time_change->tv_sec < 0)
 1323                 return;
 1324         else if (time_change->tv_sec <= LONG_MAX / 1000000)
 1325                 delta_ticks = (time_change->tv_sec * 1000000 +
 1326                                time_change->tv_usec + (tick - 1)) / tick + 1;
 1327         else if (time_change->tv_sec <= LONG_MAX / hz)
 1328                 delta_ticks = time_change->tv_sec * hz +
 1329                               (time_change->tv_usec + (tick - 1)) / tick + 1;
 1330         else
 1331                 delta_ticks = LONG_MAX;
 1332 
 1333         if (delta_ticks > INT_MAX)
 1334                 delta_ticks = INT_MAX;
 1335 
 1336         /* 
 1337          * Now rip through the timer calltodo list looking for timers
 1338          * to expire.
 1339          */
 1340 
 1341         /* don't collide with softclock() */
 1342         CC_LOCK(cc);
 1343         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 1344                 p->c_time -= delta_ticks;
 1345 
 1346                 /* Break if the timer had more time on it than delta_ticks */
 1347                 if (p->c_time > 0)
 1348                         break;
 1349 
 1350                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
 1351                 delta_ticks = -p->c_time;
 1352         }
 1353         CC_UNLOCK(cc);
 1354 
 1355         return;
 1356 }
 1357 #endif /* APM_FIXUP_CALLTODO */
 1358 
 1359 static int
 1360 flssbt(sbintime_t sbt)
 1361 {
 1362 
 1363         sbt += (uint64_t)sbt >> 1;
 1364         if (sizeof(long) >= sizeof(sbintime_t))
 1365                 return (flsl(sbt));
 1366         if (sbt >= SBT_1S)
 1367                 return (flsl(((uint64_t)sbt) >> 32) + 32);
 1368         return (flsl(sbt));
 1369 }
 1370 
 1371 /*
 1372  * Dump immediate statistic snapshot of the scheduled callouts.
 1373  */
 1374 static int
 1375 sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
 1376 {
 1377         struct callout *tmp;
 1378         struct callout_cpu *cc;
 1379         struct callout_list *sc;
 1380         sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
 1381         int ct[64], cpr[64], ccpbk[32];
 1382         int error, val, i, count, tcum, pcum, maxc, c, medc;
 1383 #ifdef SMP
 1384         int cpu;
 1385 #endif
 1386 
 1387         val = 0;
 1388         error = sysctl_handle_int(oidp, &val, 0, req);
 1389         if (error != 0 || req->newptr == NULL)
 1390                 return (error);
 1391         count = maxc = 0;
 1392         st = spr = maxt = maxpr = 0;
 1393         bzero(ccpbk, sizeof(ccpbk));
 1394         bzero(ct, sizeof(ct));
 1395         bzero(cpr, sizeof(cpr));
 1396         now = sbinuptime();
 1397 #ifdef SMP
 1398         CPU_FOREACH(cpu) {
 1399                 cc = CC_CPU(cpu);
 1400 #else
 1401                 cc = CC_CPU(timeout_cpu);
 1402 #endif
 1403                 CC_LOCK(cc);
 1404                 for (i = 0; i < callwheelsize; i++) {
 1405                         sc = &cc->cc_callwheel[i];
 1406                         c = 0;
 1407                         LIST_FOREACH(tmp, sc, c_links.le) {
 1408                                 c++;
 1409                                 t = tmp->c_time - now;
 1410                                 if (t < 0)
 1411                                         t = 0;
 1412                                 st += t / SBT_1US;
 1413                                 spr += tmp->c_precision / SBT_1US;
 1414                                 if (t > maxt)
 1415                                         maxt = t;
 1416                                 if (tmp->c_precision > maxpr)
 1417                                         maxpr = tmp->c_precision;
 1418                                 ct[flssbt(t)]++;
 1419                                 cpr[flssbt(tmp->c_precision)]++;
 1420                         }
 1421                         if (c > maxc)
 1422                                 maxc = c;
 1423                         ccpbk[fls(c + c / 2)]++;
 1424                         count += c;
 1425                 }
 1426                 CC_UNLOCK(cc);
 1427 #ifdef SMP
 1428         }
 1429 #endif
 1430 
 1431         for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
 1432                 tcum += ct[i];
 1433         medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1434         for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
 1435                 pcum += cpr[i];
 1436         medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1437         for (i = 0, c = 0; i < 32 && c < count / 2; i++)
 1438                 c += ccpbk[i];
 1439         medc = (i >= 2) ? (1 << (i - 2)) : 0;
 1440 
 1441         printf("Scheduled callouts statistic snapshot:\n");
 1442         printf("  Callouts: %6d  Buckets: %6d*%-3d  Bucket size: 0.%06ds\n",
 1443             count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
 1444         printf("  C/Bk: med %5d         avg %6d.%06jd  max %6d\n",
 1445             medc,
 1446             count / callwheelsize / mp_ncpus,
 1447             (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
 1448             maxc);
 1449         printf("  Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1450             medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
 1451             (st / count) / 1000000, (st / count) % 1000000,
 1452             maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
 1453         printf("  Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1454             medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
 1455             (spr / count) / 1000000, (spr / count) % 1000000,
 1456             maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
 1457         printf("  Distribution:       \tbuckets\t   time\t   tcum\t"
 1458             "   prec\t   pcum\n");
 1459         for (i = 0, tcum = pcum = 0; i < 64; i++) {
 1460                 if (ct[i] == 0 && cpr[i] == 0)
 1461                         continue;
 1462                 t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
 1463                 tcum += ct[i];
 1464                 pcum += cpr[i];
 1465                 printf("  %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
 1466                     t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
 1467                     i - 1 - (32 - CC_HASH_SHIFT),
 1468                     ct[i], tcum, cpr[i], pcum);
 1469         }
 1470         return (error);
 1471 }
 1472 SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
 1473     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 1474     0, 0, sysctl_kern_callout_stat, "I",
 1475     "Dump immediate statistic snapshot of the scheduled callouts");

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