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

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    1 /*-
    2  * Copyright (c) 1982, 1986, 1991, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  * (c) UNIX System Laboratories, Inc.
    5  * All or some portions of this file are derived from material licensed
    6  * to the University of California by American Telephone and Telegraph
    7  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
    8  * the permission of UNIX System Laboratories, Inc.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      From: @(#)kern_clock.c  8.5 (Berkeley) 1/21/94
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: releng/10.1/sys/kern/kern_timeout.c 260817 2014-01-17 10:58:59Z avg $");
   39 
   40 #include "opt_callout_profiling.h"
   41 #include "opt_kdtrace.h"
   42 #if defined(__arm__)
   43 #include "opt_timer.h"
   44 #endif
   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, &ncallout, 0,
  106     "Number of entries in callwheel and size of timeout() preallocation");
  107 
  108 /*
  109  * TODO:
  110  *      allocate more timeout table slots when table overflows.
  111  */
  112 u_int callwheelsize, callwheelmask;
  113 
  114 /*
  115  * The callout cpu exec entities represent informations necessary for
  116  * describing the state of callouts currently running on the CPU and the ones
  117  * necessary for migrating callouts to the new callout cpu. In particular,
  118  * the first entry of the array cc_exec_entity holds informations for callout
  119  * running in SWI thread context, while the second one holds informations
  120  * for callout running directly from hardware interrupt context.
  121  * The cached informations are very important for deferring migration when
  122  * the migrating callout is already running.
  123  */
  124 struct cc_exec {
  125         struct callout          *cc_next;
  126         struct callout          *cc_curr;
  127 #ifdef SMP
  128         void                    (*ce_migration_func)(void *);
  129         void                    *ce_migration_arg;
  130         int                     ce_migration_cpu;
  131         sbintime_t              ce_migration_time;
  132         sbintime_t              ce_migration_prec;
  133 #endif
  134         bool                    cc_cancel;
  135         bool                    cc_waiting;
  136 };
  137 
  138 /*
  139  * There is one struct callout_cpu per cpu, holding all relevant
  140  * state for the callout processing thread on the individual CPU.
  141  */
  142 struct callout_cpu {
  143         struct mtx_padalign     cc_lock;
  144         struct cc_exec          cc_exec_entity[2];
  145         struct callout          *cc_callout;
  146         struct callout_list     *cc_callwheel;
  147         struct callout_tailq    cc_expireq;
  148         struct callout_slist    cc_callfree;
  149         sbintime_t              cc_firstevent;
  150         sbintime_t              cc_lastscan;
  151         void                    *cc_cookie;
  152         u_int                   cc_bucket;
  153 };
  154 
  155 #define cc_exec_curr            cc_exec_entity[0].cc_curr
  156 #define cc_exec_next            cc_exec_entity[0].cc_next
  157 #define cc_exec_cancel          cc_exec_entity[0].cc_cancel
  158 #define cc_exec_waiting         cc_exec_entity[0].cc_waiting
  159 #define cc_exec_curr_dir        cc_exec_entity[1].cc_curr
  160 #define cc_exec_next_dir        cc_exec_entity[1].cc_next
  161 #define cc_exec_cancel_dir      cc_exec_entity[1].cc_cancel
  162 #define cc_exec_waiting_dir     cc_exec_entity[1].cc_waiting
  163 
  164 #ifdef SMP
  165 #define cc_migration_func       cc_exec_entity[0].ce_migration_func
  166 #define cc_migration_arg        cc_exec_entity[0].ce_migration_arg
  167 #define cc_migration_cpu        cc_exec_entity[0].ce_migration_cpu
  168 #define cc_migration_time       cc_exec_entity[0].ce_migration_time
  169 #define cc_migration_prec       cc_exec_entity[0].ce_migration_prec
  170 #define cc_migration_func_dir   cc_exec_entity[1].ce_migration_func
  171 #define cc_migration_arg_dir    cc_exec_entity[1].ce_migration_arg
  172 #define cc_migration_cpu_dir    cc_exec_entity[1].ce_migration_cpu
  173 #define cc_migration_time_dir   cc_exec_entity[1].ce_migration_time
  174 #define cc_migration_prec_dir   cc_exec_entity[1].ce_migration_prec
  175 
  176 struct callout_cpu cc_cpu[MAXCPU];
  177 #define CPUBLOCK        MAXCPU
  178 #define CC_CPU(cpu)     (&cc_cpu[(cpu)])
  179 #define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
  180 #else
  181 struct callout_cpu cc_cpu;
  182 #define CC_CPU(cpu)     &cc_cpu
  183 #define CC_SELF()       &cc_cpu
  184 #endif
  185 #define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
  186 #define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)
  187 #define CC_LOCK_ASSERT(cc)      mtx_assert(&(cc)->cc_lock, MA_OWNED)
  188 
  189 static int timeout_cpu;
  190 
  191 static void     callout_cpu_init(struct callout_cpu *cc);
  192 static void     softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  193 #ifdef CALLOUT_PROFILING
  194                     int *mpcalls, int *lockcalls, int *gcalls,
  195 #endif
  196                     int direct);
  197 
  198 static MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
  199 
  200 /**
  201  * Locked by cc_lock:
  202  *   cc_curr         - If a callout is in progress, it is cc_curr.
  203  *                     If cc_curr is non-NULL, threads waiting in
  204  *                     callout_drain() will be woken up as soon as the
  205  *                     relevant callout completes.
  206  *   cc_cancel       - Changing to 1 with both callout_lock and cc_lock held
  207  *                     guarantees that the current callout will not run.
  208  *                     The softclock() function sets this to 0 before it
  209  *                     drops callout_lock to acquire c_lock, and it calls
  210  *                     the handler only if curr_cancelled is still 0 after
  211  *                     cc_lock is successfully acquired.
  212  *   cc_waiting      - If a thread is waiting in callout_drain(), then
  213  *                     callout_wait is nonzero.  Set only when
  214  *                     cc_curr is non-NULL.
  215  */
  216 
  217 /*
  218  * Resets the execution entity tied to a specific callout cpu.
  219  */
  220 static void
  221 cc_cce_cleanup(struct callout_cpu *cc, int direct)
  222 {
  223 
  224         cc->cc_exec_entity[direct].cc_curr = NULL;
  225         cc->cc_exec_entity[direct].cc_next = NULL;
  226         cc->cc_exec_entity[direct].cc_cancel = false;
  227         cc->cc_exec_entity[direct].cc_waiting = false;
  228 #ifdef SMP
  229         cc->cc_exec_entity[direct].ce_migration_cpu = CPUBLOCK;
  230         cc->cc_exec_entity[direct].ce_migration_time = 0;
  231         cc->cc_exec_entity[direct].ce_migration_prec = 0;
  232         cc->cc_exec_entity[direct].ce_migration_func = NULL;
  233         cc->cc_exec_entity[direct].ce_migration_arg = NULL;
  234 #endif
  235 }
  236 
  237 /*
  238  * Checks if migration is requested by a specific callout cpu.
  239  */
  240 static int
  241 cc_cce_migrating(struct callout_cpu *cc, int direct)
  242 {
  243 
  244 #ifdef SMP
  245         return (cc->cc_exec_entity[direct].ce_migration_cpu != CPUBLOCK);
  246 #else
  247         return (0);
  248 #endif
  249 }
  250 
  251 /*
  252  * Kernel low level callwheel initialization
  253  * called on cpu0 during kernel startup.
  254  */
  255 static void
  256 callout_callwheel_init(void *dummy)
  257 {
  258         struct callout_cpu *cc;
  259 
  260         /*
  261          * Calculate the size of the callout wheel and the preallocated
  262          * timeout() structures.
  263          * XXX: Clip callout to result of previous function of maxusers
  264          * maximum 384.  This is still huge, but acceptable.
  265          */
  266         ncallout = imin(16 + maxproc + maxfiles, 18508);
  267         TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
  268 
  269         /*
  270          * Calculate callout wheel size, should be next power of two higher
  271          * than 'ncallout'.
  272          */
  273         callwheelsize = 1 << fls(ncallout);
  274         callwheelmask = callwheelsize - 1;
  275 
  276         /*
  277          * Only cpu0 handles timeout(9) and receives a preallocation.
  278          *
  279          * XXX: Once all timeout(9) consumers are converted this can
  280          * be removed.
  281          */
  282         timeout_cpu = PCPU_GET(cpuid);
  283         cc = CC_CPU(timeout_cpu);
  284         cc->cc_callout = malloc(ncallout * sizeof(struct callout),
  285             M_CALLOUT, M_WAITOK);
  286         callout_cpu_init(cc);
  287 }
  288 SYSINIT(callwheel_init, SI_SUB_CPU, SI_ORDER_ANY, callout_callwheel_init, NULL);
  289 
  290 /*
  291  * Initialize the per-cpu callout structures.
  292  */
  293 static void
  294 callout_cpu_init(struct callout_cpu *cc)
  295 {
  296         struct callout *c;
  297         int i;
  298 
  299         mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
  300         SLIST_INIT(&cc->cc_callfree);
  301         cc->cc_callwheel = malloc(sizeof(struct callout_list) * callwheelsize,
  302             M_CALLOUT, M_WAITOK);
  303         for (i = 0; i < callwheelsize; i++)
  304                 LIST_INIT(&cc->cc_callwheel[i]);
  305         TAILQ_INIT(&cc->cc_expireq);
  306         cc->cc_firstevent = INT64_MAX;
  307         for (i = 0; i < 2; i++)
  308                 cc_cce_cleanup(cc, i);
  309         if (cc->cc_callout == NULL)     /* Only cpu0 handles timeout(9) */
  310                 return;
  311         for (i = 0; i < ncallout; i++) {
  312                 c = &cc->cc_callout[i];
  313                 callout_init(c, 0);
  314                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  315                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  316         }
  317 }
  318 
  319 #ifdef SMP
  320 /*
  321  * Switches the cpu tied to a specific callout.
  322  * The function expects a locked incoming callout cpu and returns with
  323  * locked outcoming callout cpu.
  324  */
  325 static struct callout_cpu *
  326 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
  327 {
  328         struct callout_cpu *new_cc;
  329 
  330         MPASS(c != NULL && cc != NULL);
  331         CC_LOCK_ASSERT(cc);
  332 
  333         /*
  334          * Avoid interrupts and preemption firing after the callout cpu
  335          * is blocked in order to avoid deadlocks as the new thread
  336          * may be willing to acquire the callout cpu lock.
  337          */
  338         c->c_cpu = CPUBLOCK;
  339         spinlock_enter();
  340         CC_UNLOCK(cc);
  341         new_cc = CC_CPU(new_cpu);
  342         CC_LOCK(new_cc);
  343         spinlock_exit();
  344         c->c_cpu = new_cpu;
  345         return (new_cc);
  346 }
  347 #endif
  348 
  349 /*
  350  * Start standard softclock thread.
  351  */
  352 static void
  353 start_softclock(void *dummy)
  354 {
  355         struct callout_cpu *cc;
  356 #ifdef SMP
  357         int cpu;
  358 #endif
  359 
  360         cc = CC_CPU(timeout_cpu);
  361         if (swi_add(&clk_intr_event, "clock", softclock, cc, SWI_CLOCK,
  362             INTR_MPSAFE, &cc->cc_cookie))
  363                 panic("died while creating standard software ithreads");
  364 #ifdef SMP
  365         CPU_FOREACH(cpu) {
  366                 if (cpu == timeout_cpu)
  367                         continue;
  368                 cc = CC_CPU(cpu);
  369                 cc->cc_callout = NULL;  /* Only cpu0 handles timeout(9). */
  370                 callout_cpu_init(cc);
  371                 if (swi_add(NULL, "clock", softclock, cc, SWI_CLOCK,
  372                     INTR_MPSAFE, &cc->cc_cookie))
  373                         panic("died while creating standard software ithreads");
  374         }
  375 #endif
  376 }
  377 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
  378 
  379 #define CC_HASH_SHIFT   8
  380 
  381 static inline u_int
  382 callout_hash(sbintime_t sbt)
  383 {
  384 
  385         return (sbt >> (32 - CC_HASH_SHIFT));
  386 }
  387 
  388 static inline u_int
  389 callout_get_bucket(sbintime_t sbt)
  390 {
  391 
  392         return (callout_hash(sbt) & callwheelmask);
  393 }
  394 
  395 void
  396 callout_process(sbintime_t now)
  397 {
  398         struct callout *tmp, *tmpn;
  399         struct callout_cpu *cc;
  400         struct callout_list *sc;
  401         sbintime_t first, last, max, tmp_max;
  402         uint32_t lookahead;
  403         u_int firstb, lastb, nowb;
  404 #ifdef CALLOUT_PROFILING
  405         int depth_dir = 0, mpcalls_dir = 0, lockcalls_dir = 0;
  406 #endif
  407 
  408         cc = CC_SELF();
  409         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  410 
  411         /* Compute the buckets of the last scan and present times. */
  412         firstb = callout_hash(cc->cc_lastscan);
  413         cc->cc_lastscan = now;
  414         nowb = callout_hash(now);
  415 
  416         /* Compute the last bucket and minimum time of the bucket after it. */
  417         if (nowb == firstb)
  418                 lookahead = (SBT_1S / 16);
  419         else if (nowb - firstb == 1)
  420                 lookahead = (SBT_1S / 8);
  421         else
  422                 lookahead = (SBT_1S / 2);
  423         first = last = now;
  424         first += (lookahead / 2);
  425         last += lookahead;
  426         last &= (0xffffffffffffffffLLU << (32 - CC_HASH_SHIFT));
  427         lastb = callout_hash(last) - 1;
  428         max = last;
  429 
  430         /*
  431          * Check if we wrapped around the entire wheel from the last scan.
  432          * In case, we need to scan entirely the wheel for pending callouts.
  433          */
  434         if (lastb - firstb >= callwheelsize) {
  435                 lastb = firstb + callwheelsize - 1;
  436                 if (nowb - firstb >= callwheelsize)
  437                         nowb = lastb;
  438         }
  439 
  440         /* Iterate callwheel from firstb to nowb and then up to lastb. */
  441         do {
  442                 sc = &cc->cc_callwheel[firstb & callwheelmask];
  443                 tmp = LIST_FIRST(sc);
  444                 while (tmp != NULL) {
  445                         /* Run the callout if present time within allowed. */
  446                         if (tmp->c_time <= now) {
  447                                 /*
  448                                  * Consumer told us the callout may be run
  449                                  * directly from hardware interrupt context.
  450                                  */
  451                                 if (tmp->c_flags & CALLOUT_DIRECT) {
  452 #ifdef CALLOUT_PROFILING
  453                                         ++depth_dir;
  454 #endif
  455                                         cc->cc_exec_next_dir =
  456                                             LIST_NEXT(tmp, c_links.le);
  457                                         cc->cc_bucket = firstb & callwheelmask;
  458                                         LIST_REMOVE(tmp, c_links.le);
  459                                         softclock_call_cc(tmp, cc,
  460 #ifdef CALLOUT_PROFILING
  461                                             &mpcalls_dir, &lockcalls_dir, NULL,
  462 #endif
  463                                             1);
  464                                         tmp = cc->cc_exec_next_dir;
  465                                 } else {
  466                                         tmpn = LIST_NEXT(tmp, c_links.le);
  467                                         LIST_REMOVE(tmp, c_links.le);
  468                                         TAILQ_INSERT_TAIL(&cc->cc_expireq,
  469                                             tmp, c_links.tqe);
  470                                         tmp->c_flags |= CALLOUT_PROCESSED;
  471                                         tmp = tmpn;
  472                                 }
  473                                 continue;
  474                         }
  475                         /* Skip events from distant future. */
  476                         if (tmp->c_time >= max)
  477                                 goto next;
  478                         /*
  479                          * Event minimal time is bigger than present maximal
  480                          * time, so it cannot be aggregated.
  481                          */
  482                         if (tmp->c_time > last) {
  483                                 lastb = nowb;
  484                                 goto next;
  485                         }
  486                         /* Update first and last time, respecting this event. */
  487                         if (tmp->c_time < first)
  488                                 first = tmp->c_time;
  489                         tmp_max = tmp->c_time + tmp->c_precision;
  490                         if (tmp_max < last)
  491                                 last = tmp_max;
  492 next:
  493                         tmp = LIST_NEXT(tmp, c_links.le);
  494                 }
  495                 /* Proceed with the next bucket. */
  496                 firstb++;
  497                 /*
  498                  * Stop if we looked after present time and found
  499                  * some event we can't execute at now.
  500                  * Stop if we looked far enough into the future.
  501                  */
  502         } while (((int)(firstb - lastb)) <= 0);
  503         cc->cc_firstevent = last;
  504 #ifndef NO_EVENTTIMERS
  505         cpu_new_callout(curcpu, last, first);
  506 #endif
  507 #ifdef CALLOUT_PROFILING
  508         avg_depth_dir += (depth_dir * 1000 - avg_depth_dir) >> 8;
  509         avg_mpcalls_dir += (mpcalls_dir * 1000 - avg_mpcalls_dir) >> 8;
  510         avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
  511 #endif
  512         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  513         /*
  514          * swi_sched acquires the thread lock, so we don't want to call it
  515          * with cc_lock held; incorrect locking order.
  516          */
  517         if (!TAILQ_EMPTY(&cc->cc_expireq))
  518                 swi_sched(cc->cc_cookie, 0);
  519 }
  520 
  521 static struct callout_cpu *
  522 callout_lock(struct callout *c)
  523 {
  524         struct callout_cpu *cc;
  525         int cpu;
  526 
  527         for (;;) {
  528                 cpu = c->c_cpu;
  529 #ifdef SMP
  530                 if (cpu == CPUBLOCK) {
  531                         while (c->c_cpu == CPUBLOCK)
  532                                 cpu_spinwait();
  533                         continue;
  534                 }
  535 #endif
  536                 cc = CC_CPU(cpu);
  537                 CC_LOCK(cc);
  538                 if (cpu == c->c_cpu)
  539                         break;
  540                 CC_UNLOCK(cc);
  541         }
  542         return (cc);
  543 }
  544 
  545 static void
  546 callout_cc_add(struct callout *c, struct callout_cpu *cc,
  547     sbintime_t sbt, sbintime_t precision, void (*func)(void *),
  548     void *arg, int cpu, int flags)
  549 {
  550         int bucket;
  551 
  552         CC_LOCK_ASSERT(cc);
  553         if (sbt < cc->cc_lastscan)
  554                 sbt = cc->cc_lastscan;
  555         c->c_arg = arg;
  556         c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
  557         if (flags & C_DIRECT_EXEC)
  558                 c->c_flags |= CALLOUT_DIRECT;
  559         c->c_flags &= ~CALLOUT_PROCESSED;
  560         c->c_func = func;
  561         c->c_time = sbt;
  562         c->c_precision = precision;
  563         bucket = callout_get_bucket(c->c_time);
  564         CTR3(KTR_CALLOUT, "precision set for %p: %d.%08x",
  565             c, (int)(c->c_precision >> 32),
  566             (u_int)(c->c_precision & 0xffffffff));
  567         LIST_INSERT_HEAD(&cc->cc_callwheel[bucket], c, c_links.le);
  568         if (cc->cc_bucket == bucket)
  569                 cc->cc_exec_next_dir = c;
  570 #ifndef NO_EVENTTIMERS
  571         /*
  572          * Inform the eventtimers(4) subsystem there's a new callout
  573          * that has been inserted, but only if really required.
  574          */
  575         if (INT64_MAX - c->c_time < c->c_precision)
  576                 c->c_precision = INT64_MAX - c->c_time;
  577         sbt = c->c_time + c->c_precision;
  578         if (sbt < cc->cc_firstevent) {
  579                 cc->cc_firstevent = sbt;
  580                 cpu_new_callout(cpu, sbt, c->c_time);
  581         }
  582 #endif
  583 }
  584 
  585 static void
  586 callout_cc_del(struct callout *c, struct callout_cpu *cc)
  587 {
  588 
  589         if ((c->c_flags & CALLOUT_LOCAL_ALLOC) == 0)
  590                 return;
  591         c->c_func = NULL;
  592         SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  593 }
  594 
  595 static void
  596 softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  597 #ifdef CALLOUT_PROFILING
  598     int *mpcalls, int *lockcalls, int *gcalls,
  599 #endif
  600     int direct)
  601 {
  602         struct rm_priotracker tracker;
  603         void (*c_func)(void *);
  604         void *c_arg;
  605         struct lock_class *class;
  606         struct lock_object *c_lock;
  607         uintptr_t lock_status;
  608         int c_flags;
  609 #ifdef SMP
  610         struct callout_cpu *new_cc;
  611         void (*new_func)(void *);
  612         void *new_arg;
  613         int flags, new_cpu;
  614         sbintime_t new_prec, new_time;
  615 #endif
  616 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING) 
  617         sbintime_t sbt1, sbt2;
  618         struct timespec ts2;
  619         static sbintime_t maxdt = 2 * SBT_1MS;  /* 2 msec */
  620         static timeout_t *lastfunc;
  621 #endif
  622 
  623         KASSERT((c->c_flags & (CALLOUT_PENDING | CALLOUT_ACTIVE)) ==
  624             (CALLOUT_PENDING | CALLOUT_ACTIVE),
  625             ("softclock_call_cc: pend|act %p %x", c, c->c_flags));
  626         class = (c->c_lock != NULL) ? LOCK_CLASS(c->c_lock) : NULL;
  627         lock_status = 0;
  628         if (c->c_flags & CALLOUT_SHAREDLOCK) {
  629                 if (class == &lock_class_rm)
  630                         lock_status = (uintptr_t)&tracker;
  631                 else
  632                         lock_status = 1;
  633         }
  634         c_lock = c->c_lock;
  635         c_func = c->c_func;
  636         c_arg = c->c_arg;
  637         c_flags = c->c_flags;
  638         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
  639                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  640         else
  641                 c->c_flags &= ~CALLOUT_PENDING;
  642         cc->cc_exec_entity[direct].cc_curr = c;
  643         cc->cc_exec_entity[direct].cc_cancel = false;
  644         CC_UNLOCK(cc);
  645         if (c_lock != NULL) {
  646                 class->lc_lock(c_lock, lock_status);
  647                 /*
  648                  * The callout may have been cancelled
  649                  * while we switched locks.
  650                  */
  651                 if (cc->cc_exec_entity[direct].cc_cancel) {
  652                         class->lc_unlock(c_lock);
  653                         goto skip;
  654                 }
  655                 /* The callout cannot be stopped now. */
  656                 cc->cc_exec_entity[direct].cc_cancel = true;
  657                 if (c_lock == &Giant.lock_object) {
  658 #ifdef CALLOUT_PROFILING
  659                         (*gcalls)++;
  660 #endif
  661                         CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
  662                             c, c_func, c_arg);
  663                 } else {
  664 #ifdef CALLOUT_PROFILING
  665                         (*lockcalls)++;
  666 #endif
  667                         CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
  668                             c, c_func, c_arg);
  669                 }
  670         } else {
  671 #ifdef CALLOUT_PROFILING
  672                 (*mpcalls)++;
  673 #endif
  674                 CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
  675                     c, c_func, c_arg);
  676         }
  677 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  678         sbt1 = sbinuptime();
  679 #endif
  680         THREAD_NO_SLEEPING();
  681         SDT_PROBE(callout_execute, kernel, , callout__start, c, 0, 0, 0, 0);
  682         c_func(c_arg);
  683         SDT_PROBE(callout_execute, kernel, , callout__end, c, 0, 0, 0, 0);
  684         THREAD_SLEEPING_OK();
  685 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  686         sbt2 = sbinuptime();
  687         sbt2 -= sbt1;
  688         if (sbt2 > maxdt) {
  689                 if (lastfunc != c_func || sbt2 > maxdt * 2) {
  690                         ts2 = sbttots(sbt2);
  691                         printf(
  692                 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  693                             c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
  694                 }
  695                 maxdt = sbt2;
  696                 lastfunc = c_func;
  697         }
  698 #endif
  699         CTR1(KTR_CALLOUT, "callout %p finished", c);
  700         if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
  701                 class->lc_unlock(c_lock);
  702 skip:
  703         CC_LOCK(cc);
  704         KASSERT(cc->cc_exec_entity[direct].cc_curr == c, ("mishandled cc_curr"));
  705         cc->cc_exec_entity[direct].cc_curr = NULL;
  706         if (cc->cc_exec_entity[direct].cc_waiting) {
  707                 /*
  708                  * There is someone waiting for the
  709                  * callout to complete.
  710                  * If the callout was scheduled for
  711                  * migration just cancel it.
  712                  */
  713                 if (cc_cce_migrating(cc, direct)) {
  714                         cc_cce_cleanup(cc, direct);
  715 
  716                         /*
  717                          * It should be assert here that the callout is not
  718                          * destroyed but that is not easy.
  719                          */
  720                         c->c_flags &= ~CALLOUT_DFRMIGRATION;
  721                 }
  722                 cc->cc_exec_entity[direct].cc_waiting = false;
  723                 CC_UNLOCK(cc);
  724                 wakeup(&cc->cc_exec_entity[direct].cc_waiting);
  725                 CC_LOCK(cc);
  726         } else if (cc_cce_migrating(cc, direct)) {
  727                 KASSERT((c_flags & CALLOUT_LOCAL_ALLOC) == 0,
  728                     ("Migrating legacy callout %p", c));
  729 #ifdef SMP
  730                 /*
  731                  * If the callout was scheduled for
  732                  * migration just perform it now.
  733                  */
  734                 new_cpu = cc->cc_exec_entity[direct].ce_migration_cpu;
  735                 new_time = cc->cc_exec_entity[direct].ce_migration_time;
  736                 new_prec = cc->cc_exec_entity[direct].ce_migration_prec;
  737                 new_func = cc->cc_exec_entity[direct].ce_migration_func;
  738                 new_arg = cc->cc_exec_entity[direct].ce_migration_arg;
  739                 cc_cce_cleanup(cc, direct);
  740 
  741                 /*
  742                  * It should be assert here that the callout is not destroyed
  743                  * but that is not easy.
  744                  *
  745                  * As first thing, handle deferred callout stops.
  746                  */
  747                 if ((c->c_flags & CALLOUT_DFRMIGRATION) == 0) {
  748                         CTR3(KTR_CALLOUT,
  749                              "deferred cancelled %p func %p arg %p",
  750                              c, new_func, new_arg);
  751                         callout_cc_del(c, cc);
  752                         return;
  753                 }
  754                 c->c_flags &= ~CALLOUT_DFRMIGRATION;
  755 
  756                 new_cc = callout_cpu_switch(c, cc, new_cpu);
  757                 flags = (direct) ? C_DIRECT_EXEC : 0;
  758                 callout_cc_add(c, new_cc, new_time, new_prec, new_func,
  759                     new_arg, new_cpu, flags);
  760                 CC_UNLOCK(new_cc);
  761                 CC_LOCK(cc);
  762 #else
  763                 panic("migration should not happen");
  764 #endif
  765         }
  766         /*
  767          * If the current callout is locally allocated (from
  768          * timeout(9)) then put it on the freelist.
  769          *
  770          * Note: we need to check the cached copy of c_flags because
  771          * if it was not local, then it's not safe to deref the
  772          * callout pointer.
  773          */
  774         KASSERT((c_flags & CALLOUT_LOCAL_ALLOC) == 0 ||
  775             c->c_flags == CALLOUT_LOCAL_ALLOC,
  776             ("corrupted callout"));
  777         if (c_flags & CALLOUT_LOCAL_ALLOC)
  778                 callout_cc_del(c, cc);
  779 }
  780 
  781 /*
  782  * The callout mechanism is based on the work of Adam M. Costello and
  783  * George Varghese, published in a technical report entitled "Redesigning
  784  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  785  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  786  * used in this implementation was published by G. Varghese and T. Lauck in
  787  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  788  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  789  * the 11th ACM Annual Symposium on Operating Systems Principles,
  790  * Austin, Texas Nov 1987.
  791  */
  792 
  793 /*
  794  * Software (low priority) clock interrupt.
  795  * Run periodic events from timeout queue.
  796  */
  797 void
  798 softclock(void *arg)
  799 {
  800         struct callout_cpu *cc;
  801         struct callout *c;
  802 #ifdef CALLOUT_PROFILING
  803         int depth = 0, gcalls = 0, lockcalls = 0, mpcalls = 0;
  804 #endif
  805 
  806         cc = (struct callout_cpu *)arg;
  807         CC_LOCK(cc);
  808         while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
  809                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
  810                 softclock_call_cc(c, cc,
  811 #ifdef CALLOUT_PROFILING
  812                     &mpcalls, &lockcalls, &gcalls,
  813 #endif
  814                     0);
  815 #ifdef CALLOUT_PROFILING
  816                 ++depth;
  817 #endif
  818         }
  819 #ifdef CALLOUT_PROFILING
  820         avg_depth += (depth * 1000 - avg_depth) >> 8;
  821         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  822         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  823         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  824 #endif
  825         CC_UNLOCK(cc);
  826 }
  827 
  828 /*
  829  * timeout --
  830  *      Execute a function after a specified length of time.
  831  *
  832  * untimeout --
  833  *      Cancel previous timeout function call.
  834  *
  835  * callout_handle_init --
  836  *      Initialize a handle so that using it with untimeout is benign.
  837  *
  838  *      See AT&T BCI Driver Reference Manual for specification.  This
  839  *      implementation differs from that one in that although an
  840  *      identification value is returned from timeout, the original
  841  *      arguments to timeout as well as the identifier are used to
  842  *      identify entries for untimeout.
  843  */
  844 struct callout_handle
  845 timeout(ftn, arg, to_ticks)
  846         timeout_t *ftn;
  847         void *arg;
  848         int to_ticks;
  849 {
  850         struct callout_cpu *cc;
  851         struct callout *new;
  852         struct callout_handle handle;
  853 
  854         cc = CC_CPU(timeout_cpu);
  855         CC_LOCK(cc);
  856         /* Fill in the next free callout structure. */
  857         new = SLIST_FIRST(&cc->cc_callfree);
  858         if (new == NULL)
  859                 /* XXX Attempt to malloc first */
  860                 panic("timeout table full");
  861         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  862         callout_reset(new, to_ticks, ftn, arg);
  863         handle.callout = new;
  864         CC_UNLOCK(cc);
  865 
  866         return (handle);
  867 }
  868 
  869 void
  870 untimeout(ftn, arg, handle)
  871         timeout_t *ftn;
  872         void *arg;
  873         struct callout_handle handle;
  874 {
  875         struct callout_cpu *cc;
  876 
  877         /*
  878          * Check for a handle that was initialized
  879          * by callout_handle_init, but never used
  880          * for a real timeout.
  881          */
  882         if (handle.callout == NULL)
  883                 return;
  884 
  885         cc = callout_lock(handle.callout);
  886         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  887                 callout_stop(handle.callout);
  888         CC_UNLOCK(cc);
  889 }
  890 
  891 void
  892 callout_handle_init(struct callout_handle *handle)
  893 {
  894         handle->callout = NULL;
  895 }
  896 
  897 /*
  898  * New interface; clients allocate their own callout structures.
  899  *
  900  * callout_reset() - establish or change a timeout
  901  * callout_stop() - disestablish a timeout
  902  * callout_init() - initialize a callout structure so that it can
  903  *      safely be passed to callout_reset() and callout_stop()
  904  *
  905  * <sys/callout.h> defines three convenience macros:
  906  *
  907  * callout_active() - returns truth if callout has not been stopped,
  908  *      drained, or deactivated since the last time the callout was
  909  *      reset.
  910  * callout_pending() - returns truth if callout is still waiting for timeout
  911  * callout_deactivate() - marks the callout as having been serviced
  912  */
  913 int
  914 callout_reset_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t precision,
  915     void (*ftn)(void *), void *arg, int cpu, int flags)
  916 {
  917         sbintime_t to_sbt, pr;
  918         struct callout_cpu *cc;
  919         int cancelled, direct;
  920 
  921         cancelled = 0;
  922         if (flags & C_ABSOLUTE) {
  923                 to_sbt = sbt;
  924         } else {
  925                 if ((flags & C_HARDCLOCK) && (sbt < tick_sbt))
  926                         sbt = tick_sbt;
  927                 if ((flags & C_HARDCLOCK) ||
  928 #ifdef NO_EVENTTIMERS
  929                     sbt >= sbt_timethreshold) {
  930                         to_sbt = getsbinuptime();
  931 
  932                         /* Add safety belt for the case of hz > 1000. */
  933                         to_sbt += tc_tick_sbt - tick_sbt;
  934 #else
  935                     sbt >= sbt_tickthreshold) {
  936                         /*
  937                          * Obtain the time of the last hardclock() call on
  938                          * this CPU directly from the kern_clocksource.c.
  939                          * This value is per-CPU, but it is equal for all
  940                          * active ones.
  941                          */
  942 #ifdef __LP64__
  943                         to_sbt = DPCPU_GET(hardclocktime);
  944 #else
  945                         spinlock_enter();
  946                         to_sbt = DPCPU_GET(hardclocktime);
  947                         spinlock_exit();
  948 #endif
  949 #endif
  950                         if ((flags & C_HARDCLOCK) == 0)
  951                                 to_sbt += tick_sbt;
  952                 } else
  953                         to_sbt = sbinuptime();
  954                 if (INT64_MAX - to_sbt < sbt)
  955                         to_sbt = INT64_MAX;
  956                 else
  957                         to_sbt += sbt;
  958                 pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
  959                     sbt >> C_PRELGET(flags));
  960                 if (pr > precision)
  961                         precision = pr;
  962         }
  963         /*
  964          * Don't allow migration of pre-allocated callouts lest they
  965          * become unbalanced.
  966          */
  967         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
  968                 cpu = c->c_cpu;
  969         direct = (c->c_flags & CALLOUT_DIRECT) != 0;
  970         KASSERT(!direct || c->c_lock == NULL,
  971             ("%s: direct callout %p has lock", __func__, c));
  972         cc = callout_lock(c);
  973         if (cc->cc_exec_entity[direct].cc_curr == c) {
  974                 /*
  975                  * We're being asked to reschedule a callout which is
  976                  * currently in progress.  If there is a lock then we
  977                  * can cancel the callout if it has not really started.
  978                  */
  979                 if (c->c_lock != NULL && !cc->cc_exec_entity[direct].cc_cancel)
  980                         cancelled = cc->cc_exec_entity[direct].cc_cancel = true;
  981                 if (cc->cc_exec_entity[direct].cc_waiting) {
  982                         /*
  983                          * Someone has called callout_drain to kill this
  984                          * callout.  Don't reschedule.
  985                          */
  986                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
  987                             cancelled ? "cancelled" : "failed to cancel",
  988                             c, c->c_func, c->c_arg);
  989                         CC_UNLOCK(cc);
  990                         return (cancelled);
  991                 }
  992         }
  993         if (c->c_flags & CALLOUT_PENDING) {
  994                 if ((c->c_flags & CALLOUT_PROCESSED) == 0) {
  995                         if (cc->cc_exec_next_dir == c)
  996                                 cc->cc_exec_next_dir = LIST_NEXT(c, c_links.le);
  997                         LIST_REMOVE(c, c_links.le);
  998                 } else
  999                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1000                 cancelled = 1;
 1001                 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
 1002         }
 1003 
 1004 #ifdef SMP
 1005         /*
 1006          * If the callout must migrate try to perform it immediately.
 1007          * If the callout is currently running, just defer the migration
 1008          * to a more appropriate moment.
 1009          */
 1010         if (c->c_cpu != cpu) {
 1011                 if (cc->cc_exec_entity[direct].cc_curr == c) {
 1012                         cc->cc_exec_entity[direct].ce_migration_cpu = cpu;
 1013                         cc->cc_exec_entity[direct].ce_migration_time
 1014                             = to_sbt;
 1015                         cc->cc_exec_entity[direct].ce_migration_prec 
 1016                             = precision;
 1017                         cc->cc_exec_entity[direct].ce_migration_func = ftn;
 1018                         cc->cc_exec_entity[direct].ce_migration_arg = arg;
 1019                         c->c_flags |= CALLOUT_DFRMIGRATION;
 1020                         CTR6(KTR_CALLOUT,
 1021                     "migration of %p func %p arg %p in %d.%08x to %u deferred",
 1022                             c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1023                             (u_int)(to_sbt & 0xffffffff), cpu);
 1024                         CC_UNLOCK(cc);
 1025                         return (cancelled);
 1026                 }
 1027                 cc = callout_cpu_switch(c, cc, cpu);
 1028         }
 1029 #endif
 1030 
 1031         callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
 1032         CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
 1033             cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1034             (u_int)(to_sbt & 0xffffffff));
 1035         CC_UNLOCK(cc);
 1036 
 1037         return (cancelled);
 1038 }
 1039 
 1040 /*
 1041  * Common idioms that can be optimized in the future.
 1042  */
 1043 int
 1044 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
 1045 {
 1046         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
 1047 }
 1048 
 1049 int
 1050 callout_schedule(struct callout *c, int to_ticks)
 1051 {
 1052         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
 1053 }
 1054 
 1055 int
 1056 _callout_stop_safe(c, safe)
 1057         struct  callout *c;
 1058         int     safe;
 1059 {
 1060         struct callout_cpu *cc, *old_cc;
 1061         struct lock_class *class;
 1062         int direct, sq_locked, use_lock;
 1063 
 1064         /*
 1065          * Some old subsystems don't hold Giant while running a callout_stop(),
 1066          * so just discard this check for the moment.
 1067          */
 1068         if (!safe && c->c_lock != NULL) {
 1069                 if (c->c_lock == &Giant.lock_object)
 1070                         use_lock = mtx_owned(&Giant);
 1071                 else {
 1072                         use_lock = 1;
 1073                         class = LOCK_CLASS(c->c_lock);
 1074                         class->lc_assert(c->c_lock, LA_XLOCKED);
 1075                 }
 1076         } else
 1077                 use_lock = 0;
 1078         direct = (c->c_flags & CALLOUT_DIRECT) != 0;
 1079         sq_locked = 0;
 1080         old_cc = NULL;
 1081 again:
 1082         cc = callout_lock(c);
 1083 
 1084         /*
 1085          * If the callout was migrating while the callout cpu lock was
 1086          * dropped,  just drop the sleepqueue lock and check the states
 1087          * again.
 1088          */
 1089         if (sq_locked != 0 && cc != old_cc) {
 1090 #ifdef SMP
 1091                 CC_UNLOCK(cc);
 1092                 sleepq_release(&old_cc->cc_exec_entity[direct].cc_waiting);
 1093                 sq_locked = 0;
 1094                 old_cc = NULL;
 1095                 goto again;
 1096 #else
 1097                 panic("migration should not happen");
 1098 #endif
 1099         }
 1100 
 1101         /*
 1102          * If the callout isn't pending, it's not on the queue, so
 1103          * don't attempt to remove it from the queue.  We can try to
 1104          * stop it by other means however.
 1105          */
 1106         if (!(c->c_flags & CALLOUT_PENDING)) {
 1107                 c->c_flags &= ~CALLOUT_ACTIVE;
 1108 
 1109                 /*
 1110                  * If it wasn't on the queue and it isn't the current
 1111                  * callout, then we can't stop it, so just bail.
 1112                  */
 1113                 if (cc->cc_exec_entity[direct].cc_curr != c) {
 1114                         CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1115                             c, c->c_func, c->c_arg);
 1116                         CC_UNLOCK(cc);
 1117                         if (sq_locked)
 1118                                 sleepq_release(
 1119                                     &cc->cc_exec_entity[direct].cc_waiting);
 1120                         return (0);
 1121                 }
 1122 
 1123                 if (safe) {
 1124                         /*
 1125                          * The current callout is running (or just
 1126                          * about to run) and blocking is allowed, so
 1127                          * just wait for the current invocation to
 1128                          * finish.
 1129                          */
 1130                         while (cc->cc_exec_entity[direct].cc_curr == c) {
 1131                                 /*
 1132                                  * Use direct calls to sleepqueue interface
 1133                                  * instead of cv/msleep in order to avoid
 1134                                  * a LOR between cc_lock and sleepqueue
 1135                                  * chain spinlocks.  This piece of code
 1136                                  * emulates a msleep_spin() call actually.
 1137                                  *
 1138                                  * If we already have the sleepqueue chain
 1139                                  * locked, then we can safely block.  If we
 1140                                  * don't already have it locked, however,
 1141                                  * we have to drop the cc_lock to lock
 1142                                  * it.  This opens several races, so we
 1143                                  * restart at the beginning once we have
 1144                                  * both locks.  If nothing has changed, then
 1145                                  * we will end up back here with sq_locked
 1146                                  * set.
 1147                                  */
 1148                                 if (!sq_locked) {
 1149                                         CC_UNLOCK(cc);
 1150                                         sleepq_lock(
 1151                                         &cc->cc_exec_entity[direct].cc_waiting);
 1152                                         sq_locked = 1;
 1153                                         old_cc = cc;
 1154                                         goto again;
 1155                                 }
 1156 
 1157                                 /*
 1158                                  * Migration could be cancelled here, but
 1159                                  * as long as it is still not sure when it
 1160                                  * will be packed up, just let softclock()
 1161                                  * take care of it.
 1162                                  */
 1163                                 cc->cc_exec_entity[direct].cc_waiting = true;
 1164                                 DROP_GIANT();
 1165                                 CC_UNLOCK(cc);
 1166                                 sleepq_add(
 1167                                     &cc->cc_exec_entity[direct].cc_waiting,
 1168                                     &cc->cc_lock.lock_object, "codrain",
 1169                                     SLEEPQ_SLEEP, 0);
 1170                                 sleepq_wait(
 1171                                     &cc->cc_exec_entity[direct].cc_waiting,
 1172                                              0);
 1173                                 sq_locked = 0;
 1174                                 old_cc = NULL;
 1175 
 1176                                 /* Reacquire locks previously released. */
 1177                                 PICKUP_GIANT();
 1178                                 CC_LOCK(cc);
 1179                         }
 1180                 } else if (use_lock &&
 1181                             !cc->cc_exec_entity[direct].cc_cancel) {
 1182                         /*
 1183                          * The current callout is waiting for its
 1184                          * lock which we hold.  Cancel the callout
 1185                          * and return.  After our caller drops the
 1186                          * lock, the callout will be skipped in
 1187                          * softclock().
 1188                          */
 1189                         cc->cc_exec_entity[direct].cc_cancel = true;
 1190                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1191                             c, c->c_func, c->c_arg);
 1192                         KASSERT(!cc_cce_migrating(cc, direct),
 1193                             ("callout wrongly scheduled for migration"));
 1194                         CC_UNLOCK(cc);
 1195                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
 1196                         return (1);
 1197                 } else if ((c->c_flags & CALLOUT_DFRMIGRATION) != 0) {
 1198                         c->c_flags &= ~CALLOUT_DFRMIGRATION;
 1199                         CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
 1200                             c, c->c_func, c->c_arg);
 1201                         CC_UNLOCK(cc);
 1202                         return (1);
 1203                 }
 1204                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1205                     c, c->c_func, c->c_arg);
 1206                 CC_UNLOCK(cc);
 1207                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
 1208                 return (0);
 1209         }
 1210         if (sq_locked)
 1211                 sleepq_release(&cc->cc_exec_entity[direct].cc_waiting);
 1212 
 1213         c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
 1214 
 1215         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1216             c, c->c_func, c->c_arg);
 1217         if ((c->c_flags & CALLOUT_PROCESSED) == 0) {
 1218                 if (cc->cc_exec_next_dir == c)
 1219                         cc->cc_exec_next_dir = LIST_NEXT(c, c_links.le);
 1220                 LIST_REMOVE(c, c_links.le);
 1221         } else
 1222                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1223         callout_cc_del(c, cc);
 1224 
 1225         CC_UNLOCK(cc);
 1226         return (1);
 1227 }
 1228 
 1229 void
 1230 callout_init(c, mpsafe)
 1231         struct  callout *c;
 1232         int mpsafe;
 1233 {
 1234         bzero(c, sizeof *c);
 1235         if (mpsafe) {
 1236                 c->c_lock = NULL;
 1237                 c->c_flags = CALLOUT_RETURNUNLOCKED;
 1238         } else {
 1239                 c->c_lock = &Giant.lock_object;
 1240                 c->c_flags = 0;
 1241         }
 1242         c->c_cpu = timeout_cpu;
 1243 }
 1244 
 1245 void
 1246 _callout_init_lock(c, lock, flags)
 1247         struct  callout *c;
 1248         struct  lock_object *lock;
 1249         int flags;
 1250 {
 1251         bzero(c, sizeof *c);
 1252         c->c_lock = lock;
 1253         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
 1254             ("callout_init_lock: bad flags %d", flags));
 1255         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
 1256             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
 1257         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
 1258             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
 1259             __func__));
 1260         c->c_flags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
 1261         c->c_cpu = timeout_cpu;
 1262 }
 1263 
 1264 #ifdef APM_FIXUP_CALLTODO
 1265 /* 
 1266  * Adjust the kernel calltodo timeout list.  This routine is used after 
 1267  * an APM resume to recalculate the calltodo timer list values with the 
 1268  * number of hz's we have been sleeping.  The next hardclock() will detect 
 1269  * that there are fired timers and run softclock() to execute them.
 1270  *
 1271  * Please note, I have not done an exhaustive analysis of what code this
 1272  * might break.  I am motivated to have my select()'s and alarm()'s that
 1273  * have expired during suspend firing upon resume so that the applications
 1274  * which set the timer can do the maintanence the timer was for as close
 1275  * as possible to the originally intended time.  Testing this code for a 
 1276  * week showed that resuming from a suspend resulted in 22 to 25 timers 
 1277  * firing, which seemed independant on whether the suspend was 2 hours or
 1278  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 1279  */
 1280 void
 1281 adjust_timeout_calltodo(time_change)
 1282     struct timeval *time_change;
 1283 {
 1284         register struct callout *p;
 1285         unsigned long delta_ticks;
 1286 
 1287         /* 
 1288          * How many ticks were we asleep?
 1289          * (stolen from tvtohz()).
 1290          */
 1291 
 1292         /* Don't do anything */
 1293         if (time_change->tv_sec < 0)
 1294                 return;
 1295         else if (time_change->tv_sec <= LONG_MAX / 1000000)
 1296                 delta_ticks = (time_change->tv_sec * 1000000 +
 1297                                time_change->tv_usec + (tick - 1)) / tick + 1;
 1298         else if (time_change->tv_sec <= LONG_MAX / hz)
 1299                 delta_ticks = time_change->tv_sec * hz +
 1300                               (time_change->tv_usec + (tick - 1)) / tick + 1;
 1301         else
 1302                 delta_ticks = LONG_MAX;
 1303 
 1304         if (delta_ticks > INT_MAX)
 1305                 delta_ticks = INT_MAX;
 1306 
 1307         /* 
 1308          * Now rip through the timer calltodo list looking for timers
 1309          * to expire.
 1310          */
 1311 
 1312         /* don't collide with softclock() */
 1313         CC_LOCK(cc);
 1314         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 1315                 p->c_time -= delta_ticks;
 1316 
 1317                 /* Break if the timer had more time on it than delta_ticks */
 1318                 if (p->c_time > 0)
 1319                         break;
 1320 
 1321                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
 1322                 delta_ticks = -p->c_time;
 1323         }
 1324         CC_UNLOCK(cc);
 1325 
 1326         return;
 1327 }
 1328 #endif /* APM_FIXUP_CALLTODO */
 1329 
 1330 static int
 1331 flssbt(sbintime_t sbt)
 1332 {
 1333 
 1334         sbt += (uint64_t)sbt >> 1;
 1335         if (sizeof(long) >= sizeof(sbintime_t))
 1336                 return (flsl(sbt));
 1337         if (sbt >= SBT_1S)
 1338                 return (flsl(((uint64_t)sbt) >> 32) + 32);
 1339         return (flsl(sbt));
 1340 }
 1341 
 1342 /*
 1343  * Dump immediate statistic snapshot of the scheduled callouts.
 1344  */
 1345 static int
 1346 sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
 1347 {
 1348         struct callout *tmp;
 1349         struct callout_cpu *cc;
 1350         struct callout_list *sc;
 1351         sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
 1352         int ct[64], cpr[64], ccpbk[32];
 1353         int error, val, i, count, tcum, pcum, maxc, c, medc;
 1354 #ifdef SMP
 1355         int cpu;
 1356 #endif
 1357 
 1358         val = 0;
 1359         error = sysctl_handle_int(oidp, &val, 0, req);
 1360         if (error != 0 || req->newptr == NULL)
 1361                 return (error);
 1362         count = maxc = 0;
 1363         st = spr = maxt = maxpr = 0;
 1364         bzero(ccpbk, sizeof(ccpbk));
 1365         bzero(ct, sizeof(ct));
 1366         bzero(cpr, sizeof(cpr));
 1367         now = sbinuptime();
 1368 #ifdef SMP
 1369         CPU_FOREACH(cpu) {
 1370                 cc = CC_CPU(cpu);
 1371 #else
 1372                 cc = CC_CPU(timeout_cpu);
 1373 #endif
 1374                 CC_LOCK(cc);
 1375                 for (i = 0; i < callwheelsize; i++) {
 1376                         sc = &cc->cc_callwheel[i];
 1377                         c = 0;
 1378                         LIST_FOREACH(tmp, sc, c_links.le) {
 1379                                 c++;
 1380                                 t = tmp->c_time - now;
 1381                                 if (t < 0)
 1382                                         t = 0;
 1383                                 st += t / SBT_1US;
 1384                                 spr += tmp->c_precision / SBT_1US;
 1385                                 if (t > maxt)
 1386                                         maxt = t;
 1387                                 if (tmp->c_precision > maxpr)
 1388                                         maxpr = tmp->c_precision;
 1389                                 ct[flssbt(t)]++;
 1390                                 cpr[flssbt(tmp->c_precision)]++;
 1391                         }
 1392                         if (c > maxc)
 1393                                 maxc = c;
 1394                         ccpbk[fls(c + c / 2)]++;
 1395                         count += c;
 1396                 }
 1397                 CC_UNLOCK(cc);
 1398 #ifdef SMP
 1399         }
 1400 #endif
 1401 
 1402         for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
 1403                 tcum += ct[i];
 1404         medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1405         for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
 1406                 pcum += cpr[i];
 1407         medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1408         for (i = 0, c = 0; i < 32 && c < count / 2; i++)
 1409                 c += ccpbk[i];
 1410         medc = (i >= 2) ? (1 << (i - 2)) : 0;
 1411 
 1412         printf("Scheduled callouts statistic snapshot:\n");
 1413         printf("  Callouts: %6d  Buckets: %6d*%-3d  Bucket size: 0.%06ds\n",
 1414             count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
 1415         printf("  C/Bk: med %5d         avg %6d.%06jd  max %6d\n",
 1416             medc,
 1417             count / callwheelsize / mp_ncpus,
 1418             (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
 1419             maxc);
 1420         printf("  Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1421             medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
 1422             (st / count) / 1000000, (st / count) % 1000000,
 1423             maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
 1424         printf("  Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1425             medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
 1426             (spr / count) / 1000000, (spr / count) % 1000000,
 1427             maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
 1428         printf("  Distribution:       \tbuckets\t   time\t   tcum\t"
 1429             "   prec\t   pcum\n");
 1430         for (i = 0, tcum = pcum = 0; i < 64; i++) {
 1431                 if (ct[i] == 0 && cpr[i] == 0)
 1432                         continue;
 1433                 t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
 1434                 tcum += ct[i];
 1435                 pcum += cpr[i];
 1436                 printf("  %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
 1437                     t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
 1438                     i - 1 - (32 - CC_HASH_SHIFT),
 1439                     ct[i], tcum, cpr[i], pcum);
 1440         }
 1441         return (error);
 1442 }
 1443 SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
 1444     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 1445     0, 0, sysctl_kern_callout_stat, "I",
 1446     "Dump immediate statistic snapshot of the scheduled callouts");

Cache object: 975957b027aca5cec0eb6ae48ed94d06


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