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 261906 2014-02-14 23:19:51Z adrian $");
   39 
   40 #include "opt_callout_profiling.h"
   41 #if defined(__arm__)
   42 #include "opt_timer.h"
   43 #endif
   44 
   45 #include <sys/param.h>
   46 #include <sys/systm.h>
   47 #include <sys/bus.h>
   48 #include <sys/callout.h>
   49 #include <sys/file.h>
   50 #include <sys/interrupt.h>
   51 #include <sys/kernel.h>
   52 #include <sys/ktr.h>
   53 #include <sys/lock.h>
   54 #include <sys/malloc.h>
   55 #include <sys/mutex.h>
   56 #include <sys/proc.h>
   57 #include <sys/sdt.h>
   58 #include <sys/sleepqueue.h>
   59 #include <sys/sysctl.h>
   60 #include <sys/smp.h>
   61 
   62 #ifdef SMP
   63 #include <machine/cpu.h>
   64 #endif
   65 
   66 #ifndef NO_EVENTTIMERS
   67 DPCPU_DECLARE(sbintime_t, hardclocktime);
   68 #endif
   69 
   70 SDT_PROVIDER_DEFINE(callout_execute);
   71 SDT_PROBE_DEFINE1(callout_execute, kernel, , callout__start,
   72     "struct callout *");
   73 SDT_PROBE_DEFINE1(callout_execute, kernel, , callout__end,
   74     "struct callout *");
   75 
   76 #ifdef CALLOUT_PROFILING
   77 static int avg_depth;
   78 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
   79     "Average number of items examined per softclock call. Units = 1/1000");
   80 static int avg_gcalls;
   81 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
   82     "Average number of Giant callouts made per softclock call. Units = 1/1000");
   83 static int avg_lockcalls;
   84 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
   85     "Average number of lock callouts made per softclock call. Units = 1/1000");
   86 static int avg_mpcalls;
   87 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
   88     "Average number of MP callouts made per softclock call. Units = 1/1000");
   89 static int avg_depth_dir;
   90 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth_dir, CTLFLAG_RD, &avg_depth_dir, 0,
   91     "Average number of direct callouts examined per callout_process call. "
   92     "Units = 1/1000");
   93 static int avg_lockcalls_dir;
   94 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls_dir, CTLFLAG_RD,
   95     &avg_lockcalls_dir, 0, "Average number of lock direct callouts made per "
   96     "callout_process call. Units = 1/1000");
   97 static int avg_mpcalls_dir;
   98 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls_dir, CTLFLAG_RD, &avg_mpcalls_dir,
   99     0, "Average number of MP direct callouts made per callout_process call. "
  100     "Units = 1/1000");
  101 #endif
  102 
  103 static int ncallout;
  104 SYSCTL_INT(_kern, OID_AUTO, ncallout, CTLFLAG_RDTUN, &ncallout, 0,
  105     "Number of entries in callwheel and size of timeout() preallocation");
  106 
  107 /*
  108  * TODO:
  109  *      allocate more timeout table slots when table overflows.
  110  */
  111 u_int callwheelsize, callwheelmask;
  112 
  113 /*
  114  * The callout cpu exec entities represent informations necessary for
  115  * describing the state of callouts currently running on the CPU and the ones
  116  * necessary for migrating callouts to the new callout cpu. In particular,
  117  * the first entry of the array cc_exec_entity holds informations for callout
  118  * running in SWI thread context, while the second one holds informations
  119  * for callout running directly from hardware interrupt context.
  120  * The cached informations are very important for deferring migration when
  121  * the migrating callout is already running.
  122  */
  123 struct cc_exec {
  124         struct callout          *cc_next;
  125         struct callout          *cc_curr;
  126 #ifdef SMP
  127         void                    (*ce_migration_func)(void *);
  128         void                    *ce_migration_arg;
  129         int                     ce_migration_cpu;
  130         sbintime_t              ce_migration_time;
  131         sbintime_t              ce_migration_prec;
  132 #endif
  133         bool                    cc_cancel;
  134         bool                    cc_waiting;
  135 };
  136 
  137 /*
  138  * There is one struct callout_cpu per cpu, holding all relevant
  139  * state for the callout processing thread on the individual CPU.
  140  */
  141 struct callout_cpu {
  142         struct mtx_padalign     cc_lock;
  143         struct cc_exec          cc_exec_entity[2];
  144         struct callout          *cc_callout;
  145         struct callout_list     *cc_callwheel;
  146         struct callout_tailq    cc_expireq;
  147         struct callout_slist    cc_callfree;
  148         sbintime_t              cc_firstevent;
  149         sbintime_t              cc_lastscan;
  150         void                    *cc_cookie;
  151         u_int                   cc_bucket;
  152 };
  153 
  154 #define cc_exec_curr            cc_exec_entity[0].cc_curr
  155 #define cc_exec_next            cc_exec_entity[0].cc_next
  156 #define cc_exec_cancel          cc_exec_entity[0].cc_cancel
  157 #define cc_exec_waiting         cc_exec_entity[0].cc_waiting
  158 #define cc_exec_curr_dir        cc_exec_entity[1].cc_curr
  159 #define cc_exec_next_dir        cc_exec_entity[1].cc_next
  160 #define cc_exec_cancel_dir      cc_exec_entity[1].cc_cancel
  161 #define cc_exec_waiting_dir     cc_exec_entity[1].cc_waiting
  162 
  163 #ifdef SMP
  164 #define cc_migration_func       cc_exec_entity[0].ce_migration_func
  165 #define cc_migration_arg        cc_exec_entity[0].ce_migration_arg
  166 #define cc_migration_cpu        cc_exec_entity[0].ce_migration_cpu
  167 #define cc_migration_time       cc_exec_entity[0].ce_migration_time
  168 #define cc_migration_prec       cc_exec_entity[0].ce_migration_prec
  169 #define cc_migration_func_dir   cc_exec_entity[1].ce_migration_func
  170 #define cc_migration_arg_dir    cc_exec_entity[1].ce_migration_arg
  171 #define cc_migration_cpu_dir    cc_exec_entity[1].ce_migration_cpu
  172 #define cc_migration_time_dir   cc_exec_entity[1].ce_migration_time
  173 #define cc_migration_prec_dir   cc_exec_entity[1].ce_migration_prec
  174 
  175 struct callout_cpu cc_cpu[MAXCPU];
  176 #define CPUBLOCK        MAXCPU
  177 #define CC_CPU(cpu)     (&cc_cpu[(cpu)])
  178 #define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
  179 #else
  180 struct callout_cpu cc_cpu;
  181 #define CC_CPU(cpu)     &cc_cpu
  182 #define CC_SELF()       &cc_cpu
  183 #endif
  184 #define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
  185 #define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)
  186 #define CC_LOCK_ASSERT(cc)      mtx_assert(&(cc)->cc_lock, MA_OWNED)
  187 
  188 static int timeout_cpu;
  189 
  190 static void     callout_cpu_init(struct callout_cpu *cc);
  191 static void     softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  192 #ifdef CALLOUT_PROFILING
  193                     int *mpcalls, int *lockcalls, int *gcalls,
  194 #endif
  195                     int direct);
  196 
  197 static MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
  198 
  199 /**
  200  * Locked by cc_lock:
  201  *   cc_curr         - If a callout is in progress, it is cc_curr.
  202  *                     If cc_curr is non-NULL, threads waiting in
  203  *                     callout_drain() will be woken up as soon as the
  204  *                     relevant callout completes.
  205  *   cc_cancel       - Changing to 1 with both callout_lock and cc_lock held
  206  *                     guarantees that the current callout will not run.
  207  *                     The softclock() function sets this to 0 before it
  208  *                     drops callout_lock to acquire c_lock, and it calls
  209  *                     the handler only if curr_cancelled is still 0 after
  210  *                     cc_lock is successfully acquired.
  211  *   cc_waiting      - If a thread is waiting in callout_drain(), then
  212  *                     callout_wait is nonzero.  Set only when
  213  *                     cc_curr is non-NULL.
  214  */
  215 
  216 /*
  217  * Resets the execution entity tied to a specific callout cpu.
  218  */
  219 static void
  220 cc_cce_cleanup(struct callout_cpu *cc, int direct)
  221 {
  222 
  223         cc->cc_exec_entity[direct].cc_curr = NULL;
  224         cc->cc_exec_entity[direct].cc_next = NULL;
  225         cc->cc_exec_entity[direct].cc_cancel = false;
  226         cc->cc_exec_entity[direct].cc_waiting = false;
  227 #ifdef SMP
  228         cc->cc_exec_entity[direct].ce_migration_cpu = CPUBLOCK;
  229         cc->cc_exec_entity[direct].ce_migration_time = 0;
  230         cc->cc_exec_entity[direct].ce_migration_prec = 0;
  231         cc->cc_exec_entity[direct].ce_migration_func = NULL;
  232         cc->cc_exec_entity[direct].ce_migration_arg = NULL;
  233 #endif
  234 }
  235 
  236 /*
  237  * Checks if migration is requested by a specific callout cpu.
  238  */
  239 static int
  240 cc_cce_migrating(struct callout_cpu *cc, int direct)
  241 {
  242 
  243 #ifdef SMP
  244         return (cc->cc_exec_entity[direct].ce_migration_cpu != CPUBLOCK);
  245 #else
  246         return (0);
  247 #endif
  248 }
  249 
  250 /*
  251  * Kernel low level callwheel initialization
  252  * called on cpu0 during kernel startup.
  253  */
  254 static void
  255 callout_callwheel_init(void *dummy)
  256 {
  257         struct callout_cpu *cc;
  258 
  259         /*
  260          * Calculate the size of the callout wheel and the preallocated
  261          * timeout() structures.
  262          * XXX: Clip callout to result of previous function of maxusers
  263          * maximum 384.  This is still huge, but acceptable.
  264          */
  265         ncallout = imin(16 + maxproc + maxfiles, 18508);
  266         TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
  267 
  268         /*
  269          * Calculate callout wheel size, should be next power of two higher
  270          * than 'ncallout'.
  271          */
  272         callwheelsize = 1 << fls(ncallout);
  273         callwheelmask = callwheelsize - 1;
  274 
  275         /*
  276          * Only cpu0 handles timeout(9) and receives a preallocation.
  277          *
  278          * XXX: Once all timeout(9) consumers are converted this can
  279          * be removed.
  280          */
  281         timeout_cpu = PCPU_GET(cpuid);
  282         cc = CC_CPU(timeout_cpu);
  283         cc->cc_callout = malloc(ncallout * sizeof(struct callout),
  284             M_CALLOUT, M_WAITOK);
  285         callout_cpu_init(cc);
  286 }
  287 SYSINIT(callwheel_init, SI_SUB_CPU, SI_ORDER_ANY, callout_callwheel_init, NULL);
  288 
  289 /*
  290  * Initialize the per-cpu callout structures.
  291  */
  292 static void
  293 callout_cpu_init(struct callout_cpu *cc)
  294 {
  295         struct callout *c;
  296         int i;
  297 
  298         mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
  299         SLIST_INIT(&cc->cc_callfree);
  300         cc->cc_callwheel = malloc(sizeof(struct callout_list) * callwheelsize,
  301             M_CALLOUT, M_WAITOK);
  302         for (i = 0; i < callwheelsize; i++)
  303                 LIST_INIT(&cc->cc_callwheel[i]);
  304         TAILQ_INIT(&cc->cc_expireq);
  305         cc->cc_firstevent = INT64_MAX;
  306         for (i = 0; i < 2; i++)
  307                 cc_cce_cleanup(cc, i);
  308         if (cc->cc_callout == NULL)     /* Only cpu0 handles timeout(9) */
  309                 return;
  310         for (i = 0; i < ncallout; i++) {
  311                 c = &cc->cc_callout[i];
  312                 callout_init(c, 0);
  313                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  314                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  315         }
  316 }
  317 
  318 #ifdef SMP
  319 /*
  320  * Switches the cpu tied to a specific callout.
  321  * The function expects a locked incoming callout cpu and returns with
  322  * locked outcoming callout cpu.
  323  */
  324 static struct callout_cpu *
  325 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
  326 {
  327         struct callout_cpu *new_cc;
  328 
  329         MPASS(c != NULL && cc != NULL);
  330         CC_LOCK_ASSERT(cc);
  331 
  332         /*
  333          * Avoid interrupts and preemption firing after the callout cpu
  334          * is blocked in order to avoid deadlocks as the new thread
  335          * may be willing to acquire the callout cpu lock.
  336          */
  337         c->c_cpu = CPUBLOCK;
  338         spinlock_enter();
  339         CC_UNLOCK(cc);
  340         new_cc = CC_CPU(new_cpu);
  341         CC_LOCK(new_cc);
  342         spinlock_exit();
  343         c->c_cpu = new_cpu;
  344         return (new_cc);
  345 }
  346 #endif
  347 
  348 /*
  349  * Start standard softclock thread.
  350  */
  351 static void
  352 start_softclock(void *dummy)
  353 {
  354         struct callout_cpu *cc;
  355         char name[MAXCOMLEN];
  356 #ifdef SMP
  357         int cpu;
  358 #endif
  359 
  360         cc = CC_CPU(timeout_cpu);
  361         snprintf(name, sizeof(name), "clock (%d)", timeout_cpu);
  362         if (swi_add(&clk_intr_event, name, softclock, cc, SWI_CLOCK,
  363             INTR_MPSAFE, &cc->cc_cookie))
  364                 panic("died while creating standard software ithreads");
  365 #ifdef SMP
  366         CPU_FOREACH(cpu) {
  367                 if (cpu == timeout_cpu)
  368                         continue;
  369                 cc = CC_CPU(cpu);
  370                 cc->cc_callout = NULL;  /* Only cpu0 handles timeout(9). */
  371                 callout_cpu_init(cc);
  372                 snprintf(name, sizeof(name), "clock (%d)", cpu);
  373                 if (swi_add(NULL, name, softclock, cc, SWI_CLOCK,
  374                     INTR_MPSAFE, &cc->cc_cookie))
  375                         panic("died while creating standard software ithreads");
  376         }
  377 #endif
  378 }
  379 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
  380 
  381 #define CC_HASH_SHIFT   8
  382 
  383 static inline u_int
  384 callout_hash(sbintime_t sbt)
  385 {
  386 
  387         return (sbt >> (32 - CC_HASH_SHIFT));
  388 }
  389 
  390 static inline u_int
  391 callout_get_bucket(sbintime_t sbt)
  392 {
  393 
  394         return (callout_hash(sbt) & callwheelmask);
  395 }
  396 
  397 void
  398 callout_process(sbintime_t now)
  399 {
  400         struct callout *tmp, *tmpn;
  401         struct callout_cpu *cc;
  402         struct callout_list *sc;
  403         sbintime_t first, last, max, tmp_max;
  404         uint32_t lookahead;
  405         u_int firstb, lastb, nowb;
  406 #ifdef CALLOUT_PROFILING
  407         int depth_dir = 0, mpcalls_dir = 0, lockcalls_dir = 0;
  408 #endif
  409 
  410         cc = CC_SELF();
  411         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  412 
  413         /* Compute the buckets of the last scan and present times. */
  414         firstb = callout_hash(cc->cc_lastscan);
  415         cc->cc_lastscan = now;
  416         nowb = callout_hash(now);
  417 
  418         /* Compute the last bucket and minimum time of the bucket after it. */
  419         if (nowb == firstb)
  420                 lookahead = (SBT_1S / 16);
  421         else if (nowb - firstb == 1)
  422                 lookahead = (SBT_1S / 8);
  423         else
  424                 lookahead = (SBT_1S / 2);
  425         first = last = now;
  426         first += (lookahead / 2);
  427         last += lookahead;
  428         last &= (0xffffffffffffffffLLU << (32 - CC_HASH_SHIFT));
  429         lastb = callout_hash(last) - 1;
  430         max = last;
  431 
  432         /*
  433          * Check if we wrapped around the entire wheel from the last scan.
  434          * In case, we need to scan entirely the wheel for pending callouts.
  435          */
  436         if (lastb - firstb >= callwheelsize) {
  437                 lastb = firstb + callwheelsize - 1;
  438                 if (nowb - firstb >= callwheelsize)
  439                         nowb = lastb;
  440         }
  441 
  442         /* Iterate callwheel from firstb to nowb and then up to lastb. */
  443         do {
  444                 sc = &cc->cc_callwheel[firstb & callwheelmask];
  445                 tmp = LIST_FIRST(sc);
  446                 while (tmp != NULL) {
  447                         /* Run the callout if present time within allowed. */
  448                         if (tmp->c_time <= now) {
  449                                 /*
  450                                  * Consumer told us the callout may be run
  451                                  * directly from hardware interrupt context.
  452                                  */
  453                                 if (tmp->c_flags & CALLOUT_DIRECT) {
  454 #ifdef CALLOUT_PROFILING
  455                                         ++depth_dir;
  456 #endif
  457                                         cc->cc_exec_next_dir =
  458                                             LIST_NEXT(tmp, c_links.le);
  459                                         cc->cc_bucket = firstb & callwheelmask;
  460                                         LIST_REMOVE(tmp, c_links.le);
  461                                         softclock_call_cc(tmp, cc,
  462 #ifdef CALLOUT_PROFILING
  463                                             &mpcalls_dir, &lockcalls_dir, NULL,
  464 #endif
  465                                             1);
  466                                         tmp = cc->cc_exec_next_dir;
  467                                 } else {
  468                                         tmpn = LIST_NEXT(tmp, c_links.le);
  469                                         LIST_REMOVE(tmp, c_links.le);
  470                                         TAILQ_INSERT_TAIL(&cc->cc_expireq,
  471                                             tmp, c_links.tqe);
  472                                         tmp->c_flags |= CALLOUT_PROCESSED;
  473                                         tmp = tmpn;
  474                                 }
  475                                 continue;
  476                         }
  477                         /* Skip events from distant future. */
  478                         if (tmp->c_time >= max)
  479                                 goto next;
  480                         /*
  481                          * Event minimal time is bigger than present maximal
  482                          * time, so it cannot be aggregated.
  483                          */
  484                         if (tmp->c_time > last) {
  485                                 lastb = nowb;
  486                                 goto next;
  487                         }
  488                         /* Update first and last time, respecting this event. */
  489                         if (tmp->c_time < first)
  490                                 first = tmp->c_time;
  491                         tmp_max = tmp->c_time + tmp->c_precision;
  492                         if (tmp_max < last)
  493                                 last = tmp_max;
  494 next:
  495                         tmp = LIST_NEXT(tmp, c_links.le);
  496                 }
  497                 /* Proceed with the next bucket. */
  498                 firstb++;
  499                 /*
  500                  * Stop if we looked after present time and found
  501                  * some event we can't execute at now.
  502                  * Stop if we looked far enough into the future.
  503                  */
  504         } while (((int)(firstb - lastb)) <= 0);
  505         cc->cc_firstevent = last;
  506 #ifndef NO_EVENTTIMERS
  507         cpu_new_callout(curcpu, last, first);
  508 #endif
  509 #ifdef CALLOUT_PROFILING
  510         avg_depth_dir += (depth_dir * 1000 - avg_depth_dir) >> 8;
  511         avg_mpcalls_dir += (mpcalls_dir * 1000 - avg_mpcalls_dir) >> 8;
  512         avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
  513 #endif
  514         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  515         /*
  516          * swi_sched acquires the thread lock, so we don't want to call it
  517          * with cc_lock held; incorrect locking order.
  518          */
  519         if (!TAILQ_EMPTY(&cc->cc_expireq))
  520                 swi_sched(cc->cc_cookie, 0);
  521 }
  522 
  523 static struct callout_cpu *
  524 callout_lock(struct callout *c)
  525 {
  526         struct callout_cpu *cc;
  527         int cpu;
  528 
  529         for (;;) {
  530                 cpu = c->c_cpu;
  531 #ifdef SMP
  532                 if (cpu == CPUBLOCK) {
  533                         while (c->c_cpu == CPUBLOCK)
  534                                 cpu_spinwait();
  535                         continue;
  536                 }
  537 #endif
  538                 cc = CC_CPU(cpu);
  539                 CC_LOCK(cc);
  540                 if (cpu == c->c_cpu)
  541                         break;
  542                 CC_UNLOCK(cc);
  543         }
  544         return (cc);
  545 }
  546 
  547 static void
  548 callout_cc_add(struct callout *c, struct callout_cpu *cc,
  549     sbintime_t sbt, sbintime_t precision, void (*func)(void *),
  550     void *arg, int cpu, int flags)
  551 {
  552         int bucket;
  553 
  554         CC_LOCK_ASSERT(cc);
  555         if (sbt < cc->cc_lastscan)
  556                 sbt = cc->cc_lastscan;
  557         c->c_arg = arg;
  558         c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
  559         if (flags & C_DIRECT_EXEC)
  560                 c->c_flags |= CALLOUT_DIRECT;
  561         c->c_flags &= ~CALLOUT_PROCESSED;
  562         c->c_func = func;
  563         c->c_time = sbt;
  564         c->c_precision = precision;
  565         bucket = callout_get_bucket(c->c_time);
  566         CTR3(KTR_CALLOUT, "precision set for %p: %d.%08x",
  567             c, (int)(c->c_precision >> 32),
  568             (u_int)(c->c_precision & 0xffffffff));
  569         LIST_INSERT_HEAD(&cc->cc_callwheel[bucket], c, c_links.le);
  570         if (cc->cc_bucket == bucket)
  571                 cc->cc_exec_next_dir = c;
  572 #ifndef NO_EVENTTIMERS
  573         /*
  574          * Inform the eventtimers(4) subsystem there's a new callout
  575          * that has been inserted, but only if really required.
  576          */
  577         if (INT64_MAX - c->c_time < c->c_precision)
  578                 c->c_precision = INT64_MAX - c->c_time;
  579         sbt = c->c_time + c->c_precision;
  580         if (sbt < cc->cc_firstevent) {
  581                 cc->cc_firstevent = sbt;
  582                 cpu_new_callout(cpu, sbt, c->c_time);
  583         }
  584 #endif
  585 }
  586 
  587 static void
  588 callout_cc_del(struct callout *c, struct callout_cpu *cc)
  589 {
  590 
  591         if ((c->c_flags & CALLOUT_LOCAL_ALLOC) == 0)
  592                 return;
  593         c->c_func = NULL;
  594         SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  595 }
  596 
  597 static void
  598 softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  599 #ifdef CALLOUT_PROFILING
  600     int *mpcalls, int *lockcalls, int *gcalls,
  601 #endif
  602     int direct)
  603 {
  604         struct rm_priotracker tracker;
  605         void (*c_func)(void *);
  606         void *c_arg;
  607         struct lock_class *class;
  608         struct lock_object *c_lock;
  609         uintptr_t lock_status;
  610         int c_flags;
  611 #ifdef SMP
  612         struct callout_cpu *new_cc;
  613         void (*new_func)(void *);
  614         void *new_arg;
  615         int flags, new_cpu;
  616         sbintime_t new_prec, new_time;
  617 #endif
  618 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING) 
  619         sbintime_t sbt1, sbt2;
  620         struct timespec ts2;
  621         static sbintime_t maxdt = 2 * SBT_1MS;  /* 2 msec */
  622         static timeout_t *lastfunc;
  623 #endif
  624 
  625         KASSERT((c->c_flags & (CALLOUT_PENDING | CALLOUT_ACTIVE)) ==
  626             (CALLOUT_PENDING | CALLOUT_ACTIVE),
  627             ("softclock_call_cc: pend|act %p %x", c, c->c_flags));
  628         class = (c->c_lock != NULL) ? LOCK_CLASS(c->c_lock) : NULL;
  629         lock_status = 0;
  630         if (c->c_flags & CALLOUT_SHAREDLOCK) {
  631                 if (class == &lock_class_rm)
  632                         lock_status = (uintptr_t)&tracker;
  633                 else
  634                         lock_status = 1;
  635         }
  636         c_lock = c->c_lock;
  637         c_func = c->c_func;
  638         c_arg = c->c_arg;
  639         c_flags = c->c_flags;
  640         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
  641                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  642         else
  643                 c->c_flags &= ~CALLOUT_PENDING;
  644         cc->cc_exec_entity[direct].cc_curr = c;
  645         cc->cc_exec_entity[direct].cc_cancel = false;
  646         CC_UNLOCK(cc);
  647         if (c_lock != NULL) {
  648                 class->lc_lock(c_lock, lock_status);
  649                 /*
  650                  * The callout may have been cancelled
  651                  * while we switched locks.
  652                  */
  653                 if (cc->cc_exec_entity[direct].cc_cancel) {
  654                         class->lc_unlock(c_lock);
  655                         goto skip;
  656                 }
  657                 /* The callout cannot be stopped now. */
  658                 cc->cc_exec_entity[direct].cc_cancel = true;
  659                 if (c_lock == &Giant.lock_object) {
  660 #ifdef CALLOUT_PROFILING
  661                         (*gcalls)++;
  662 #endif
  663                         CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
  664                             c, c_func, c_arg);
  665                 } else {
  666 #ifdef CALLOUT_PROFILING
  667                         (*lockcalls)++;
  668 #endif
  669                         CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
  670                             c, c_func, c_arg);
  671                 }
  672         } else {
  673 #ifdef CALLOUT_PROFILING
  674                 (*mpcalls)++;
  675 #endif
  676                 CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
  677                     c, c_func, c_arg);
  678         }
  679 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  680         sbt1 = sbinuptime();
  681 #endif
  682         THREAD_NO_SLEEPING();
  683         SDT_PROBE(callout_execute, kernel, , callout__start, c, 0, 0, 0, 0);
  684         c_func(c_arg);
  685         SDT_PROBE(callout_execute, kernel, , callout__end, c, 0, 0, 0, 0);
  686         THREAD_SLEEPING_OK();
  687 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  688         sbt2 = sbinuptime();
  689         sbt2 -= sbt1;
  690         if (sbt2 > maxdt) {
  691                 if (lastfunc != c_func || sbt2 > maxdt * 2) {
  692                         ts2 = sbttots(sbt2);
  693                         printf(
  694                 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  695                             c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
  696                 }
  697                 maxdt = sbt2;
  698                 lastfunc = c_func;
  699         }
  700 #endif
  701         CTR1(KTR_CALLOUT, "callout %p finished", c);
  702         if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
  703                 class->lc_unlock(c_lock);
  704 skip:
  705         CC_LOCK(cc);
  706         KASSERT(cc->cc_exec_entity[direct].cc_curr == c, ("mishandled cc_curr"));
  707         cc->cc_exec_entity[direct].cc_curr = NULL;
  708         if (cc->cc_exec_entity[direct].cc_waiting) {
  709                 /*
  710                  * There is someone waiting for the
  711                  * callout to complete.
  712                  * If the callout was scheduled for
  713                  * migration just cancel it.
  714                  */
  715                 if (cc_cce_migrating(cc, direct)) {
  716                         cc_cce_cleanup(cc, direct);
  717 
  718                         /*
  719                          * It should be assert here that the callout is not
  720                          * destroyed but that is not easy.
  721                          */
  722                         c->c_flags &= ~CALLOUT_DFRMIGRATION;
  723                 }
  724                 cc->cc_exec_entity[direct].cc_waiting = false;
  725                 CC_UNLOCK(cc);
  726                 wakeup(&cc->cc_exec_entity[direct].cc_waiting);
  727                 CC_LOCK(cc);
  728         } else if (cc_cce_migrating(cc, direct)) {
  729                 KASSERT((c_flags & CALLOUT_LOCAL_ALLOC) == 0,
  730                     ("Migrating legacy callout %p", c));
  731 #ifdef SMP
  732                 /*
  733                  * If the callout was scheduled for
  734                  * migration just perform it now.
  735                  */
  736                 new_cpu = cc->cc_exec_entity[direct].ce_migration_cpu;
  737                 new_time = cc->cc_exec_entity[direct].ce_migration_time;
  738                 new_prec = cc->cc_exec_entity[direct].ce_migration_prec;
  739                 new_func = cc->cc_exec_entity[direct].ce_migration_func;
  740                 new_arg = cc->cc_exec_entity[direct].ce_migration_arg;
  741                 cc_cce_cleanup(cc, direct);
  742 
  743                 /*
  744                  * It should be assert here that the callout is not destroyed
  745                  * but that is not easy.
  746                  *
  747                  * As first thing, handle deferred callout stops.
  748                  */
  749                 if ((c->c_flags & CALLOUT_DFRMIGRATION) == 0) {
  750                         CTR3(KTR_CALLOUT,
  751                              "deferred cancelled %p func %p arg %p",
  752                              c, new_func, new_arg);
  753                         callout_cc_del(c, cc);
  754                         return;
  755                 }
  756                 c->c_flags &= ~CALLOUT_DFRMIGRATION;
  757 
  758                 new_cc = callout_cpu_switch(c, cc, new_cpu);
  759                 flags = (direct) ? C_DIRECT_EXEC : 0;
  760                 callout_cc_add(c, new_cc, new_time, new_prec, new_func,
  761                     new_arg, new_cpu, flags);
  762                 CC_UNLOCK(new_cc);
  763                 CC_LOCK(cc);
  764 #else
  765                 panic("migration should not happen");
  766 #endif
  767         }
  768         /*
  769          * If the current callout is locally allocated (from
  770          * timeout(9)) then put it on the freelist.
  771          *
  772          * Note: we need to check the cached copy of c_flags because
  773          * if it was not local, then it's not safe to deref the
  774          * callout pointer.
  775          */
  776         KASSERT((c_flags & CALLOUT_LOCAL_ALLOC) == 0 ||
  777             c->c_flags == CALLOUT_LOCAL_ALLOC,
  778             ("corrupted callout"));
  779         if (c_flags & CALLOUT_LOCAL_ALLOC)
  780                 callout_cc_del(c, cc);
  781 }
  782 
  783 /*
  784  * The callout mechanism is based on the work of Adam M. Costello and
  785  * George Varghese, published in a technical report entitled "Redesigning
  786  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  787  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  788  * used in this implementation was published by G. Varghese and T. Lauck in
  789  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  790  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  791  * the 11th ACM Annual Symposium on Operating Systems Principles,
  792  * Austin, Texas Nov 1987.
  793  */
  794 
  795 /*
  796  * Software (low priority) clock interrupt.
  797  * Run periodic events from timeout queue.
  798  */
  799 void
  800 softclock(void *arg)
  801 {
  802         struct callout_cpu *cc;
  803         struct callout *c;
  804 #ifdef CALLOUT_PROFILING
  805         int depth = 0, gcalls = 0, lockcalls = 0, mpcalls = 0;
  806 #endif
  807 
  808         cc = (struct callout_cpu *)arg;
  809         CC_LOCK(cc);
  810         while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
  811                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
  812                 softclock_call_cc(c, cc,
  813 #ifdef CALLOUT_PROFILING
  814                     &mpcalls, &lockcalls, &gcalls,
  815 #endif
  816                     0);
  817 #ifdef CALLOUT_PROFILING
  818                 ++depth;
  819 #endif
  820         }
  821 #ifdef CALLOUT_PROFILING
  822         avg_depth += (depth * 1000 - avg_depth) >> 8;
  823         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  824         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  825         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  826 #endif
  827         CC_UNLOCK(cc);
  828 }
  829 
  830 /*
  831  * timeout --
  832  *      Execute a function after a specified length of time.
  833  *
  834  * untimeout --
  835  *      Cancel previous timeout function call.
  836  *
  837  * callout_handle_init --
  838  *      Initialize a handle so that using it with untimeout is benign.
  839  *
  840  *      See AT&T BCI Driver Reference Manual for specification.  This
  841  *      implementation differs from that one in that although an
  842  *      identification value is returned from timeout, the original
  843  *      arguments to timeout as well as the identifier are used to
  844  *      identify entries for untimeout.
  845  */
  846 struct callout_handle
  847 timeout(ftn, arg, to_ticks)
  848         timeout_t *ftn;
  849         void *arg;
  850         int to_ticks;
  851 {
  852         struct callout_cpu *cc;
  853         struct callout *new;
  854         struct callout_handle handle;
  855 
  856         cc = CC_CPU(timeout_cpu);
  857         CC_LOCK(cc);
  858         /* Fill in the next free callout structure. */
  859         new = SLIST_FIRST(&cc->cc_callfree);
  860         if (new == NULL)
  861                 /* XXX Attempt to malloc first */
  862                 panic("timeout table full");
  863         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  864         callout_reset(new, to_ticks, ftn, arg);
  865         handle.callout = new;
  866         CC_UNLOCK(cc);
  867 
  868         return (handle);
  869 }
  870 
  871 void
  872 untimeout(ftn, arg, handle)
  873         timeout_t *ftn;
  874         void *arg;
  875         struct callout_handle handle;
  876 {
  877         struct callout_cpu *cc;
  878 
  879         /*
  880          * Check for a handle that was initialized
  881          * by callout_handle_init, but never used
  882          * for a real timeout.
  883          */
  884         if (handle.callout == NULL)
  885                 return;
  886 
  887         cc = callout_lock(handle.callout);
  888         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  889                 callout_stop(handle.callout);
  890         CC_UNLOCK(cc);
  891 }
  892 
  893 void
  894 callout_handle_init(struct callout_handle *handle)
  895 {
  896         handle->callout = NULL;
  897 }
  898 
  899 /*
  900  * New interface; clients allocate their own callout structures.
  901  *
  902  * callout_reset() - establish or change a timeout
  903  * callout_stop() - disestablish a timeout
  904  * callout_init() - initialize a callout structure so that it can
  905  *      safely be passed to callout_reset() and callout_stop()
  906  *
  907  * <sys/callout.h> defines three convenience macros:
  908  *
  909  * callout_active() - returns truth if callout has not been stopped,
  910  *      drained, or deactivated since the last time the callout was
  911  *      reset.
  912  * callout_pending() - returns truth if callout is still waiting for timeout
  913  * callout_deactivate() - marks the callout as having been serviced
  914  */
  915 int
  916 callout_reset_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t precision,
  917     void (*ftn)(void *), void *arg, int cpu, int flags)
  918 {
  919         sbintime_t to_sbt, pr;
  920         struct callout_cpu *cc;
  921         int cancelled, direct;
  922 
  923         cancelled = 0;
  924         if (flags & C_ABSOLUTE) {
  925                 to_sbt = sbt;
  926         } else {
  927                 if ((flags & C_HARDCLOCK) && (sbt < tick_sbt))
  928                         sbt = tick_sbt;
  929                 if ((flags & C_HARDCLOCK) ||
  930 #ifdef NO_EVENTTIMERS
  931                     sbt >= sbt_timethreshold) {
  932                         to_sbt = getsbinuptime();
  933 
  934                         /* Add safety belt for the case of hz > 1000. */
  935                         to_sbt += tc_tick_sbt - tick_sbt;
  936 #else
  937                     sbt >= sbt_tickthreshold) {
  938                         /*
  939                          * Obtain the time of the last hardclock() call on
  940                          * this CPU directly from the kern_clocksource.c.
  941                          * This value is per-CPU, but it is equal for all
  942                          * active ones.
  943                          */
  944 #ifdef __LP64__
  945                         to_sbt = DPCPU_GET(hardclocktime);
  946 #else
  947                         spinlock_enter();
  948                         to_sbt = DPCPU_GET(hardclocktime);
  949                         spinlock_exit();
  950 #endif
  951 #endif
  952                         if ((flags & C_HARDCLOCK) == 0)
  953                                 to_sbt += tick_sbt;
  954                 } else
  955                         to_sbt = sbinuptime();
  956                 if (INT64_MAX - to_sbt < sbt)
  957                         to_sbt = INT64_MAX;
  958                 else
  959                         to_sbt += sbt;
  960                 pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
  961                     sbt >> C_PRELGET(flags));
  962                 if (pr > precision)
  963                         precision = pr;
  964         }
  965         /*
  966          * Don't allow migration of pre-allocated callouts lest they
  967          * become unbalanced.
  968          */
  969         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
  970                 cpu = c->c_cpu;
  971         direct = (c->c_flags & CALLOUT_DIRECT) != 0;
  972         KASSERT(!direct || c->c_lock == NULL,
  973             ("%s: direct callout %p has lock", __func__, c));
  974         cc = callout_lock(c);
  975         if (cc->cc_exec_entity[direct].cc_curr == c) {
  976                 /*
  977                  * We're being asked to reschedule a callout which is
  978                  * currently in progress.  If there is a lock then we
  979                  * can cancel the callout if it has not really started.
  980                  */
  981                 if (c->c_lock != NULL && !cc->cc_exec_entity[direct].cc_cancel)
  982                         cancelled = cc->cc_exec_entity[direct].cc_cancel = true;
  983                 if (cc->cc_exec_entity[direct].cc_waiting) {
  984                         /*
  985                          * Someone has called callout_drain to kill this
  986                          * callout.  Don't reschedule.
  987                          */
  988                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
  989                             cancelled ? "cancelled" : "failed to cancel",
  990                             c, c->c_func, c->c_arg);
  991                         CC_UNLOCK(cc);
  992                         return (cancelled);
  993                 }
  994         }
  995         if (c->c_flags & CALLOUT_PENDING) {
  996                 if ((c->c_flags & CALLOUT_PROCESSED) == 0) {
  997                         if (cc->cc_exec_next_dir == c)
  998                                 cc->cc_exec_next_dir = LIST_NEXT(c, c_links.le);
  999                         LIST_REMOVE(c, c_links.le);
 1000                 } else
 1001                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1002                 cancelled = 1;
 1003                 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
 1004         }
 1005 
 1006 #ifdef SMP
 1007         /*
 1008          * If the callout must migrate try to perform it immediately.
 1009          * If the callout is currently running, just defer the migration
 1010          * to a more appropriate moment.
 1011          */
 1012         if (c->c_cpu != cpu) {
 1013                 if (cc->cc_exec_entity[direct].cc_curr == c) {
 1014                         cc->cc_exec_entity[direct].ce_migration_cpu = cpu;
 1015                         cc->cc_exec_entity[direct].ce_migration_time
 1016                             = to_sbt;
 1017                         cc->cc_exec_entity[direct].ce_migration_prec 
 1018                             = precision;
 1019                         cc->cc_exec_entity[direct].ce_migration_func = ftn;
 1020                         cc->cc_exec_entity[direct].ce_migration_arg = arg;
 1021                         c->c_flags |= CALLOUT_DFRMIGRATION;
 1022                         CTR6(KTR_CALLOUT,
 1023                     "migration of %p func %p arg %p in %d.%08x to %u deferred",
 1024                             c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1025                             (u_int)(to_sbt & 0xffffffff), cpu);
 1026                         CC_UNLOCK(cc);
 1027                         return (cancelled);
 1028                 }
 1029                 cc = callout_cpu_switch(c, cc, cpu);
 1030         }
 1031 #endif
 1032 
 1033         callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
 1034         CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
 1035             cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1036             (u_int)(to_sbt & 0xffffffff));
 1037         CC_UNLOCK(cc);
 1038 
 1039         return (cancelled);
 1040 }
 1041 
 1042 /*
 1043  * Common idioms that can be optimized in the future.
 1044  */
 1045 int
 1046 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
 1047 {
 1048         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
 1049 }
 1050 
 1051 int
 1052 callout_schedule(struct callout *c, int to_ticks)
 1053 {
 1054         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
 1055 }
 1056 
 1057 int
 1058 _callout_stop_safe(c, safe)
 1059         struct  callout *c;
 1060         int     safe;
 1061 {
 1062         struct callout_cpu *cc, *old_cc;
 1063         struct lock_class *class;
 1064         int direct, sq_locked, use_lock;
 1065 
 1066         /*
 1067          * Some old subsystems don't hold Giant while running a callout_stop(),
 1068          * so just discard this check for the moment.
 1069          */
 1070         if (!safe && c->c_lock != NULL) {
 1071                 if (c->c_lock == &Giant.lock_object)
 1072                         use_lock = mtx_owned(&Giant);
 1073                 else {
 1074                         use_lock = 1;
 1075                         class = LOCK_CLASS(c->c_lock);
 1076                         class->lc_assert(c->c_lock, LA_XLOCKED);
 1077                 }
 1078         } else
 1079                 use_lock = 0;
 1080         direct = (c->c_flags & CALLOUT_DIRECT) != 0;
 1081         sq_locked = 0;
 1082         old_cc = NULL;
 1083 again:
 1084         cc = callout_lock(c);
 1085 
 1086         /*
 1087          * If the callout was migrating while the callout cpu lock was
 1088          * dropped,  just drop the sleepqueue lock and check the states
 1089          * again.
 1090          */
 1091         if (sq_locked != 0 && cc != old_cc) {
 1092 #ifdef SMP
 1093                 CC_UNLOCK(cc);
 1094                 sleepq_release(&old_cc->cc_exec_entity[direct].cc_waiting);
 1095                 sq_locked = 0;
 1096                 old_cc = NULL;
 1097                 goto again;
 1098 #else
 1099                 panic("migration should not happen");
 1100 #endif
 1101         }
 1102 
 1103         /*
 1104          * If the callout isn't pending, it's not on the queue, so
 1105          * don't attempt to remove it from the queue.  We can try to
 1106          * stop it by other means however.
 1107          */
 1108         if (!(c->c_flags & CALLOUT_PENDING)) {
 1109                 c->c_flags &= ~CALLOUT_ACTIVE;
 1110 
 1111                 /*
 1112                  * If it wasn't on the queue and it isn't the current
 1113                  * callout, then we can't stop it, so just bail.
 1114                  */
 1115                 if (cc->cc_exec_entity[direct].cc_curr != c) {
 1116                         CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1117                             c, c->c_func, c->c_arg);
 1118                         CC_UNLOCK(cc);
 1119                         if (sq_locked)
 1120                                 sleepq_release(
 1121                                     &cc->cc_exec_entity[direct].cc_waiting);
 1122                         return (0);
 1123                 }
 1124 
 1125                 if (safe) {
 1126                         /*
 1127                          * The current callout is running (or just
 1128                          * about to run) and blocking is allowed, so
 1129                          * just wait for the current invocation to
 1130                          * finish.
 1131                          */
 1132                         while (cc->cc_exec_entity[direct].cc_curr == c) {
 1133                                 /*
 1134                                  * Use direct calls to sleepqueue interface
 1135                                  * instead of cv/msleep in order to avoid
 1136                                  * a LOR between cc_lock and sleepqueue
 1137                                  * chain spinlocks.  This piece of code
 1138                                  * emulates a msleep_spin() call actually.
 1139                                  *
 1140                                  * If we already have the sleepqueue chain
 1141                                  * locked, then we can safely block.  If we
 1142                                  * don't already have it locked, however,
 1143                                  * we have to drop the cc_lock to lock
 1144                                  * it.  This opens several races, so we
 1145                                  * restart at the beginning once we have
 1146                                  * both locks.  If nothing has changed, then
 1147                                  * we will end up back here with sq_locked
 1148                                  * set.
 1149                                  */
 1150                                 if (!sq_locked) {
 1151                                         CC_UNLOCK(cc);
 1152                                         sleepq_lock(
 1153                                         &cc->cc_exec_entity[direct].cc_waiting);
 1154                                         sq_locked = 1;
 1155                                         old_cc = cc;
 1156                                         goto again;
 1157                                 }
 1158 
 1159                                 /*
 1160                                  * Migration could be cancelled here, but
 1161                                  * as long as it is still not sure when it
 1162                                  * will be packed up, just let softclock()
 1163                                  * take care of it.
 1164                                  */
 1165                                 cc->cc_exec_entity[direct].cc_waiting = true;
 1166                                 DROP_GIANT();
 1167                                 CC_UNLOCK(cc);
 1168                                 sleepq_add(
 1169                                     &cc->cc_exec_entity[direct].cc_waiting,
 1170                                     &cc->cc_lock.lock_object, "codrain",
 1171                                     SLEEPQ_SLEEP, 0);
 1172                                 sleepq_wait(
 1173                                     &cc->cc_exec_entity[direct].cc_waiting,
 1174                                              0);
 1175                                 sq_locked = 0;
 1176                                 old_cc = NULL;
 1177 
 1178                                 /* Reacquire locks previously released. */
 1179                                 PICKUP_GIANT();
 1180                                 CC_LOCK(cc);
 1181                         }
 1182                 } else if (use_lock &&
 1183                             !cc->cc_exec_entity[direct].cc_cancel) {
 1184                         /*
 1185                          * The current callout is waiting for its
 1186                          * lock which we hold.  Cancel the callout
 1187                          * and return.  After our caller drops the
 1188                          * lock, the callout will be skipped in
 1189                          * softclock().
 1190                          */
 1191                         cc->cc_exec_entity[direct].cc_cancel = true;
 1192                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1193                             c, c->c_func, c->c_arg);
 1194                         KASSERT(!cc_cce_migrating(cc, direct),
 1195                             ("callout wrongly scheduled for migration"));
 1196                         CC_UNLOCK(cc);
 1197                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
 1198                         return (1);
 1199                 } else if ((c->c_flags & CALLOUT_DFRMIGRATION) != 0) {
 1200                         c->c_flags &= ~CALLOUT_DFRMIGRATION;
 1201                         CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
 1202                             c, c->c_func, c->c_arg);
 1203                         CC_UNLOCK(cc);
 1204                         return (1);
 1205                 }
 1206                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1207                     c, c->c_func, c->c_arg);
 1208                 CC_UNLOCK(cc);
 1209                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
 1210                 return (0);
 1211         }
 1212         if (sq_locked)
 1213                 sleepq_release(&cc->cc_exec_entity[direct].cc_waiting);
 1214 
 1215         c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
 1216 
 1217         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1218             c, c->c_func, c->c_arg);
 1219         if ((c->c_flags & CALLOUT_PROCESSED) == 0) {
 1220                 if (cc->cc_exec_next_dir == c)
 1221                         cc->cc_exec_next_dir = LIST_NEXT(c, c_links.le);
 1222                 LIST_REMOVE(c, c_links.le);
 1223         } else
 1224                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1225         callout_cc_del(c, cc);
 1226 
 1227         CC_UNLOCK(cc);
 1228         return (1);
 1229 }
 1230 
 1231 void
 1232 callout_init(c, mpsafe)
 1233         struct  callout *c;
 1234         int mpsafe;
 1235 {
 1236         bzero(c, sizeof *c);
 1237         if (mpsafe) {
 1238                 c->c_lock = NULL;
 1239                 c->c_flags = CALLOUT_RETURNUNLOCKED;
 1240         } else {
 1241                 c->c_lock = &Giant.lock_object;
 1242                 c->c_flags = 0;
 1243         }
 1244         c->c_cpu = timeout_cpu;
 1245 }
 1246 
 1247 void
 1248 _callout_init_lock(c, lock, flags)
 1249         struct  callout *c;
 1250         struct  lock_object *lock;
 1251         int flags;
 1252 {
 1253         bzero(c, sizeof *c);
 1254         c->c_lock = lock;
 1255         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
 1256             ("callout_init_lock: bad flags %d", flags));
 1257         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
 1258             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
 1259         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
 1260             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
 1261             __func__));
 1262         c->c_flags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
 1263         c->c_cpu = timeout_cpu;
 1264 }
 1265 
 1266 #ifdef APM_FIXUP_CALLTODO
 1267 /* 
 1268  * Adjust the kernel calltodo timeout list.  This routine is used after 
 1269  * an APM resume to recalculate the calltodo timer list values with the 
 1270  * number of hz's we have been sleeping.  The next hardclock() will detect 
 1271  * that there are fired timers and run softclock() to execute them.
 1272  *
 1273  * Please note, I have not done an exhaustive analysis of what code this
 1274  * might break.  I am motivated to have my select()'s and alarm()'s that
 1275  * have expired during suspend firing upon resume so that the applications
 1276  * which set the timer can do the maintanence the timer was for as close
 1277  * as possible to the originally intended time.  Testing this code for a 
 1278  * week showed that resuming from a suspend resulted in 22 to 25 timers 
 1279  * firing, which seemed independant on whether the suspend was 2 hours or
 1280  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 1281  */
 1282 void
 1283 adjust_timeout_calltodo(time_change)
 1284     struct timeval *time_change;
 1285 {
 1286         register struct callout *p;
 1287         unsigned long delta_ticks;
 1288 
 1289         /* 
 1290          * How many ticks were we asleep?
 1291          * (stolen from tvtohz()).
 1292          */
 1293 
 1294         /* Don't do anything */
 1295         if (time_change->tv_sec < 0)
 1296                 return;
 1297         else if (time_change->tv_sec <= LONG_MAX / 1000000)
 1298                 delta_ticks = (time_change->tv_sec * 1000000 +
 1299                                time_change->tv_usec + (tick - 1)) / tick + 1;
 1300         else if (time_change->tv_sec <= LONG_MAX / hz)
 1301                 delta_ticks = time_change->tv_sec * hz +
 1302                               (time_change->tv_usec + (tick - 1)) / tick + 1;
 1303         else
 1304                 delta_ticks = LONG_MAX;
 1305 
 1306         if (delta_ticks > INT_MAX)
 1307                 delta_ticks = INT_MAX;
 1308 
 1309         /* 
 1310          * Now rip through the timer calltodo list looking for timers
 1311          * to expire.
 1312          */
 1313 
 1314         /* don't collide with softclock() */
 1315         CC_LOCK(cc);
 1316         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 1317                 p->c_time -= delta_ticks;
 1318 
 1319                 /* Break if the timer had more time on it than delta_ticks */
 1320                 if (p->c_time > 0)
 1321                         break;
 1322 
 1323                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
 1324                 delta_ticks = -p->c_time;
 1325         }
 1326         CC_UNLOCK(cc);
 1327 
 1328         return;
 1329 }
 1330 #endif /* APM_FIXUP_CALLTODO */
 1331 
 1332 static int
 1333 flssbt(sbintime_t sbt)
 1334 {
 1335 
 1336         sbt += (uint64_t)sbt >> 1;
 1337         if (sizeof(long) >= sizeof(sbintime_t))
 1338                 return (flsl(sbt));
 1339         if (sbt >= SBT_1S)
 1340                 return (flsl(((uint64_t)sbt) >> 32) + 32);
 1341         return (flsl(sbt));
 1342 }
 1343 
 1344 /*
 1345  * Dump immediate statistic snapshot of the scheduled callouts.
 1346  */
 1347 static int
 1348 sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
 1349 {
 1350         struct callout *tmp;
 1351         struct callout_cpu *cc;
 1352         struct callout_list *sc;
 1353         sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
 1354         int ct[64], cpr[64], ccpbk[32];
 1355         int error, val, i, count, tcum, pcum, maxc, c, medc;
 1356 #ifdef SMP
 1357         int cpu;
 1358 #endif
 1359 
 1360         val = 0;
 1361         error = sysctl_handle_int(oidp, &val, 0, req);
 1362         if (error != 0 || req->newptr == NULL)
 1363                 return (error);
 1364         count = maxc = 0;
 1365         st = spr = maxt = maxpr = 0;
 1366         bzero(ccpbk, sizeof(ccpbk));
 1367         bzero(ct, sizeof(ct));
 1368         bzero(cpr, sizeof(cpr));
 1369         now = sbinuptime();
 1370 #ifdef SMP
 1371         CPU_FOREACH(cpu) {
 1372                 cc = CC_CPU(cpu);
 1373 #else
 1374                 cc = CC_CPU(timeout_cpu);
 1375 #endif
 1376                 CC_LOCK(cc);
 1377                 for (i = 0; i < callwheelsize; i++) {
 1378                         sc = &cc->cc_callwheel[i];
 1379                         c = 0;
 1380                         LIST_FOREACH(tmp, sc, c_links.le) {
 1381                                 c++;
 1382                                 t = tmp->c_time - now;
 1383                                 if (t < 0)
 1384                                         t = 0;
 1385                                 st += t / SBT_1US;
 1386                                 spr += tmp->c_precision / SBT_1US;
 1387                                 if (t > maxt)
 1388                                         maxt = t;
 1389                                 if (tmp->c_precision > maxpr)
 1390                                         maxpr = tmp->c_precision;
 1391                                 ct[flssbt(t)]++;
 1392                                 cpr[flssbt(tmp->c_precision)]++;
 1393                         }
 1394                         if (c > maxc)
 1395                                 maxc = c;
 1396                         ccpbk[fls(c + c / 2)]++;
 1397                         count += c;
 1398                 }
 1399                 CC_UNLOCK(cc);
 1400 #ifdef SMP
 1401         }
 1402 #endif
 1403 
 1404         for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
 1405                 tcum += ct[i];
 1406         medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1407         for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
 1408                 pcum += cpr[i];
 1409         medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1410         for (i = 0, c = 0; i < 32 && c < count / 2; i++)
 1411                 c += ccpbk[i];
 1412         medc = (i >= 2) ? (1 << (i - 2)) : 0;
 1413 
 1414         printf("Scheduled callouts statistic snapshot:\n");
 1415         printf("  Callouts: %6d  Buckets: %6d*%-3d  Bucket size: 0.%06ds\n",
 1416             count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
 1417         printf("  C/Bk: med %5d         avg %6d.%06jd  max %6d\n",
 1418             medc,
 1419             count / callwheelsize / mp_ncpus,
 1420             (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
 1421             maxc);
 1422         printf("  Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1423             medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
 1424             (st / count) / 1000000, (st / count) % 1000000,
 1425             maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
 1426         printf("  Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1427             medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
 1428             (spr / count) / 1000000, (spr / count) % 1000000,
 1429             maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
 1430         printf("  Distribution:       \tbuckets\t   time\t   tcum\t"
 1431             "   prec\t   pcum\n");
 1432         for (i = 0, tcum = pcum = 0; i < 64; i++) {
 1433                 if (ct[i] == 0 && cpr[i] == 0)
 1434                         continue;
 1435                 t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
 1436                 tcum += ct[i];
 1437                 pcum += cpr[i];
 1438                 printf("  %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
 1439                     t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
 1440                     i - 1 - (32 - CC_HASH_SHIFT),
 1441                     ct[i], tcum, cpr[i], pcum);
 1442         }
 1443         return (error);
 1444 }
 1445 SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
 1446     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 1447     0, 0, sysctl_kern_callout_stat, "I",
 1448     "Dump immediate statistic snapshot of the scheduled callouts");

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