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 278623 2015-02-12 13:31:08Z rrs $");
   39 
   40 #include "opt_callout_profiling.h"
   41 #if defined(__arm__)
   42 #include "opt_timer.h"
   43 #endif
   44 #include "opt_rss.h"
   45 
   46 #include <sys/param.h>
   47 #include <sys/systm.h>
   48 #include <sys/bus.h>
   49 #include <sys/callout.h>
   50 #include <sys/file.h>
   51 #include <sys/interrupt.h>
   52 #include <sys/kernel.h>
   53 #include <sys/ktr.h>
   54 #include <sys/lock.h>
   55 #include <sys/malloc.h>
   56 #include <sys/mutex.h>
   57 #include <sys/proc.h>
   58 #include <sys/sdt.h>
   59 #include <sys/sleepqueue.h>
   60 #include <sys/sysctl.h>
   61 #include <sys/smp.h>
   62 
   63 #ifdef SMP
   64 #include <machine/cpu.h>
   65 #endif
   66 
   67 #ifndef NO_EVENTTIMERS
   68 DPCPU_DECLARE(sbintime_t, hardclocktime);
   69 #endif
   70 
   71 SDT_PROVIDER_DEFINE(callout_execute);
   72 SDT_PROBE_DEFINE1(callout_execute, kernel, , callout__start,
   73     "struct callout *");
   74 SDT_PROBE_DEFINE1(callout_execute, kernel, , callout__end,
   75     "struct callout *");
   76 
   77 #ifdef CALLOUT_PROFILING
   78 static int avg_depth;
   79 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
   80     "Average number of items examined per softclock call. Units = 1/1000");
   81 static int avg_gcalls;
   82 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
   83     "Average number of Giant callouts made per softclock call. Units = 1/1000");
   84 static int avg_lockcalls;
   85 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
   86     "Average number of lock callouts made per softclock call. Units = 1/1000");
   87 static int avg_mpcalls;
   88 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
   89     "Average number of MP callouts made per softclock call. Units = 1/1000");
   90 static int avg_depth_dir;
   91 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth_dir, CTLFLAG_RD, &avg_depth_dir, 0,
   92     "Average number of direct callouts examined per callout_process call. "
   93     "Units = 1/1000");
   94 static int avg_lockcalls_dir;
   95 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls_dir, CTLFLAG_RD,
   96     &avg_lockcalls_dir, 0, "Average number of lock direct callouts made per "
   97     "callout_process call. Units = 1/1000");
   98 static int avg_mpcalls_dir;
   99 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls_dir, CTLFLAG_RD, &avg_mpcalls_dir,
  100     0, "Average number of MP direct callouts made per callout_process call. "
  101     "Units = 1/1000");
  102 #endif
  103 
  104 static int ncallout;
  105 SYSCTL_INT(_kern, OID_AUTO, ncallout, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &ncallout, 0,
  106     "Number of entries in callwheel and size of timeout() preallocation");
  107 
  108 #ifdef  RSS
  109 static int pin_default_swi = 1;
  110 static int pin_pcpu_swi = 1;
  111 #else
  112 static int pin_default_swi = 0;
  113 static int pin_pcpu_swi = 0;
  114 #endif
  115 
  116 SYSCTL_INT(_kern, OID_AUTO, pin_default_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_default_swi,
  117     0, "Pin the default (non-per-cpu) swi (shared with PCPU 0 swi)");
  118 SYSCTL_INT(_kern, OID_AUTO, pin_pcpu_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_pcpu_swi,
  119     0, "Pin the per-CPU swis (except PCPU 0, which is also default");
  120 
  121 /*
  122  * TODO:
  123  *      allocate more timeout table slots when table overflows.
  124  */
  125 u_int callwheelsize, callwheelmask;
  126 
  127 /*
  128  * The callout cpu exec entities represent informations necessary for
  129  * describing the state of callouts currently running on the CPU and the ones
  130  * necessary for migrating callouts to the new callout cpu. In particular,
  131  * the first entry of the array cc_exec_entity holds informations for callout
  132  * running in SWI thread context, while the second one holds informations
  133  * for callout running directly from hardware interrupt context.
  134  * The cached informations are very important for deferring migration when
  135  * the migrating callout is already running.
  136  */
  137 struct cc_exec {
  138         struct callout          *cc_curr;
  139 #ifdef SMP
  140         void                    (*ce_migration_func)(void *);
  141         void                    *ce_migration_arg;
  142         int                     ce_migration_cpu;
  143         sbintime_t              ce_migration_time;
  144         sbintime_t              ce_migration_prec;
  145 #endif
  146         bool                    cc_cancel;
  147         bool                    cc_waiting;
  148 };
  149 
  150 /*
  151  * There is one struct callout_cpu per cpu, holding all relevant
  152  * state for the callout processing thread on the individual CPU.
  153  */
  154 struct callout_cpu {
  155         struct mtx_padalign     cc_lock;
  156         struct cc_exec          cc_exec_entity[2];
  157         struct callout          *cc_next;
  158         struct callout          *cc_callout;
  159         struct callout_list     *cc_callwheel;
  160         struct callout_tailq    cc_expireq;
  161         struct callout_slist    cc_callfree;
  162         sbintime_t              cc_firstevent;
  163         sbintime_t              cc_lastscan;
  164         void                    *cc_cookie;
  165         u_int                   cc_bucket;
  166         char                    cc_ktr_event_name[20];
  167 };
  168 
  169 #define cc_exec_curr(cc, dir)           cc->cc_exec_entity[dir].cc_curr
  170 #define cc_exec_next(cc)                cc->cc_next
  171 #define cc_exec_cancel(cc, dir)         cc->cc_exec_entity[dir].cc_cancel
  172 #define cc_exec_waiting(cc, dir)        cc->cc_exec_entity[dir].cc_waiting
  173 #ifdef SMP
  174 #define cc_migration_func(cc, dir)      cc->cc_exec_entity[dir].ce_migration_func
  175 #define cc_migration_arg(cc, dir)       cc->cc_exec_entity[dir].ce_migration_arg
  176 #define cc_migration_cpu(cc, dir)       cc->cc_exec_entity[dir].ce_migration_cpu
  177 #define cc_migration_time(cc, dir)      cc->cc_exec_entity[dir].ce_migration_time
  178 #define cc_migration_prec(cc, dir)      cc->cc_exec_entity[dir].ce_migration_prec
  179 
  180 struct callout_cpu cc_cpu[MAXCPU];
  181 #define CPUBLOCK        MAXCPU
  182 #define CC_CPU(cpu)     (&cc_cpu[(cpu)])
  183 #define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
  184 #else
  185 struct callout_cpu cc_cpu;
  186 #define CC_CPU(cpu)     &cc_cpu
  187 #define CC_SELF()       &cc_cpu
  188 #endif
  189 #define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
  190 #define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)
  191 #define CC_LOCK_ASSERT(cc)      mtx_assert(&(cc)->cc_lock, MA_OWNED)
  192 
  193 static int timeout_cpu;
  194 
  195 static void     callout_cpu_init(struct callout_cpu *cc, int cpu);
  196 static void     softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  197 #ifdef CALLOUT_PROFILING
  198                     int *mpcalls, int *lockcalls, int *gcalls,
  199 #endif
  200                     int direct);
  201 
  202 static MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
  203 
  204 /**
  205  * Locked by cc_lock:
  206  *   cc_curr         - If a callout is in progress, it is cc_curr.
  207  *                     If cc_curr is non-NULL, threads waiting in
  208  *                     callout_drain() will be woken up as soon as the
  209  *                     relevant callout completes.
  210  *   cc_cancel       - Changing to 1 with both callout_lock and cc_lock held
  211  *                     guarantees that the current callout will not run.
  212  *                     The softclock() function sets this to 0 before it
  213  *                     drops callout_lock to acquire c_lock, and it calls
  214  *                     the handler only if curr_cancelled is still 0 after
  215  *                     cc_lock is successfully acquired.
  216  *   cc_waiting      - If a thread is waiting in callout_drain(), then
  217  *                     callout_wait is nonzero.  Set only when
  218  *                     cc_curr is non-NULL.
  219  */
  220 
  221 /*
  222  * Resets the execution entity tied to a specific callout cpu.
  223  */
  224 static void
  225 cc_cce_cleanup(struct callout_cpu *cc, int direct)
  226 {
  227 
  228         cc_exec_curr(cc, direct) = NULL;
  229         cc_exec_cancel(cc, direct) = false;
  230         cc_exec_waiting(cc, direct) = false;
  231 #ifdef SMP
  232         cc_migration_cpu(cc, direct) = CPUBLOCK;
  233         cc_migration_time(cc, direct) = 0;
  234         cc_migration_prec(cc, direct) = 0;
  235         cc_migration_func(cc, direct) = NULL;
  236         cc_migration_arg(cc, direct) = NULL;
  237 #endif
  238 }
  239 
  240 /*
  241  * Checks if migration is requested by a specific callout cpu.
  242  */
  243 static int
  244 cc_cce_migrating(struct callout_cpu *cc, int direct)
  245 {
  246 
  247 #ifdef SMP
  248         return (cc_migration_cpu(cc, direct) != CPUBLOCK);
  249 #else
  250         return (0);
  251 #endif
  252 }
  253 
  254 /*
  255  * Kernel low level callwheel initialization
  256  * called on cpu0 during kernel startup.
  257  */
  258 static void
  259 callout_callwheel_init(void *dummy)
  260 {
  261         struct callout_cpu *cc;
  262 
  263         /*
  264          * Calculate the size of the callout wheel and the preallocated
  265          * timeout() structures.
  266          * XXX: Clip callout to result of previous function of maxusers
  267          * maximum 384.  This is still huge, but acceptable.
  268          */
  269         ncallout = imin(16 + maxproc + maxfiles, 18508);
  270         TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
  271 
  272         /*
  273          * Calculate callout wheel size, should be next power of two higher
  274          * than 'ncallout'.
  275          */
  276         callwheelsize = 1 << fls(ncallout);
  277         callwheelmask = callwheelsize - 1;
  278 
  279         /*
  280          * Fetch whether we're pinning the swi's or not.
  281          */
  282         TUNABLE_INT_FETCH("kern.pin_default_swi", &pin_default_swi);
  283         TUNABLE_INT_FETCH("kern.pin_pcpu_swi", &pin_pcpu_swi);
  284 
  285         /*
  286          * Only cpu0 handles timeout(9) and receives a preallocation.
  287          *
  288          * XXX: Once all timeout(9) consumers are converted this can
  289          * be removed.
  290          */
  291         timeout_cpu = PCPU_GET(cpuid);
  292         cc = CC_CPU(timeout_cpu);
  293         cc->cc_callout = malloc(ncallout * sizeof(struct callout),
  294             M_CALLOUT, M_WAITOK);
  295         callout_cpu_init(cc, timeout_cpu);
  296 }
  297 SYSINIT(callwheel_init, SI_SUB_CPU, SI_ORDER_ANY, callout_callwheel_init, NULL);
  298 
  299 /*
  300  * Initialize the per-cpu callout structures.
  301  */
  302 static void
  303 callout_cpu_init(struct callout_cpu *cc, int cpu)
  304 {
  305         struct callout *c;
  306         int i;
  307 
  308         mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
  309         SLIST_INIT(&cc->cc_callfree);
  310         cc->cc_callwheel = malloc(sizeof(struct callout_list) * callwheelsize,
  311             M_CALLOUT, M_WAITOK);
  312         for (i = 0; i < callwheelsize; i++)
  313                 LIST_INIT(&cc->cc_callwheel[i]);
  314         TAILQ_INIT(&cc->cc_expireq);
  315         cc->cc_firstevent = SBT_MAX;
  316         for (i = 0; i < 2; i++)
  317                 cc_cce_cleanup(cc, i);
  318         snprintf(cc->cc_ktr_event_name, sizeof(cc->cc_ktr_event_name),
  319             "callwheel cpu %d", cpu);
  320         if (cc->cc_callout == NULL)     /* Only cpu0 handles timeout(9) */
  321                 return;
  322         for (i = 0; i < ncallout; i++) {
  323                 c = &cc->cc_callout[i];
  324                 callout_init(c, 0);
  325                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  326                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  327         }
  328 }
  329 
  330 #ifdef SMP
  331 /*
  332  * Switches the cpu tied to a specific callout.
  333  * The function expects a locked incoming callout cpu and returns with
  334  * locked outcoming callout cpu.
  335  */
  336 static struct callout_cpu *
  337 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
  338 {
  339         struct callout_cpu *new_cc;
  340 
  341         MPASS(c != NULL && cc != NULL);
  342         CC_LOCK_ASSERT(cc);
  343 
  344         /*
  345          * Avoid interrupts and preemption firing after the callout cpu
  346          * is blocked in order to avoid deadlocks as the new thread
  347          * may be willing to acquire the callout cpu lock.
  348          */
  349         c->c_cpu = CPUBLOCK;
  350         spinlock_enter();
  351         CC_UNLOCK(cc);
  352         new_cc = CC_CPU(new_cpu);
  353         CC_LOCK(new_cc);
  354         spinlock_exit();
  355         c->c_cpu = new_cpu;
  356         return (new_cc);
  357 }
  358 #endif
  359 
  360 /*
  361  * Start standard softclock thread.
  362  */
  363 static void
  364 start_softclock(void *dummy)
  365 {
  366         struct callout_cpu *cc;
  367         char name[MAXCOMLEN];
  368 #ifdef SMP
  369         int cpu;
  370         struct intr_event *ie;
  371 #endif
  372 
  373         cc = CC_CPU(timeout_cpu);
  374         snprintf(name, sizeof(name), "clock (%d)", timeout_cpu);
  375         if (swi_add(&clk_intr_event, name, softclock, cc, SWI_CLOCK,
  376             INTR_MPSAFE, &cc->cc_cookie))
  377                 panic("died while creating standard software ithreads");
  378         if (pin_default_swi &&
  379             (intr_event_bind(clk_intr_event, timeout_cpu) != 0)) {
  380                 printf("%s: timeout clock couldn't be pinned to cpu %d\n",
  381                     __func__,
  382                     timeout_cpu);
  383         }
  384 
  385 #ifdef SMP
  386         CPU_FOREACH(cpu) {
  387                 if (cpu == timeout_cpu)
  388                         continue;
  389                 cc = CC_CPU(cpu);
  390                 cc->cc_callout = NULL;  /* Only cpu0 handles timeout(9). */
  391                 callout_cpu_init(cc, cpu);
  392                 snprintf(name, sizeof(name), "clock (%d)", cpu);
  393                 ie = NULL;
  394                 if (swi_add(&ie, name, softclock, cc, SWI_CLOCK,
  395                     INTR_MPSAFE, &cc->cc_cookie))
  396                         panic("died while creating standard software ithreads");
  397                 if (pin_pcpu_swi && (intr_event_bind(ie, cpu) != 0)) {
  398                         printf("%s: per-cpu clock couldn't be pinned to "
  399                             "cpu %d\n",
  400                             __func__,
  401                             cpu);
  402                 }
  403         }
  404 #endif
  405 }
  406 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
  407 
  408 #define CC_HASH_SHIFT   8
  409 
  410 static inline u_int
  411 callout_hash(sbintime_t sbt)
  412 {
  413 
  414         return (sbt >> (32 - CC_HASH_SHIFT));
  415 }
  416 
  417 static inline u_int
  418 callout_get_bucket(sbintime_t sbt)
  419 {
  420 
  421         return (callout_hash(sbt) & callwheelmask);
  422 }
  423 
  424 void
  425 callout_process(sbintime_t now)
  426 {
  427         struct callout *tmp, *tmpn;
  428         struct callout_cpu *cc;
  429         struct callout_list *sc;
  430         sbintime_t first, last, max, tmp_max;
  431         uint32_t lookahead;
  432         u_int firstb, lastb, nowb;
  433 #ifdef CALLOUT_PROFILING
  434         int depth_dir = 0, mpcalls_dir = 0, lockcalls_dir = 0;
  435 #endif
  436 
  437         cc = CC_SELF();
  438         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  439 
  440         /* Compute the buckets of the last scan and present times. */
  441         firstb = callout_hash(cc->cc_lastscan);
  442         cc->cc_lastscan = now;
  443         nowb = callout_hash(now);
  444 
  445         /* Compute the last bucket and minimum time of the bucket after it. */
  446         if (nowb == firstb)
  447                 lookahead = (SBT_1S / 16);
  448         else if (nowb - firstb == 1)
  449                 lookahead = (SBT_1S / 8);
  450         else
  451                 lookahead = (SBT_1S / 2);
  452         first = last = now;
  453         first += (lookahead / 2);
  454         last += lookahead;
  455         last &= (0xffffffffffffffffLLU << (32 - CC_HASH_SHIFT));
  456         lastb = callout_hash(last) - 1;
  457         max = last;
  458 
  459         /*
  460          * Check if we wrapped around the entire wheel from the last scan.
  461          * In case, we need to scan entirely the wheel for pending callouts.
  462          */
  463         if (lastb - firstb >= callwheelsize) {
  464                 lastb = firstb + callwheelsize - 1;
  465                 if (nowb - firstb >= callwheelsize)
  466                         nowb = lastb;
  467         }
  468 
  469         /* Iterate callwheel from firstb to nowb and then up to lastb. */
  470         do {
  471                 sc = &cc->cc_callwheel[firstb & callwheelmask];
  472                 tmp = LIST_FIRST(sc);
  473                 while (tmp != NULL) {
  474                         /* Run the callout if present time within allowed. */
  475                         if (tmp->c_time <= now) {
  476                                 /*
  477                                  * Consumer told us the callout may be run
  478                                  * directly from hardware interrupt context.
  479                                  */
  480                                 if (tmp->c_flags & CALLOUT_DIRECT) {
  481 #ifdef CALLOUT_PROFILING
  482                                         ++depth_dir;
  483 #endif
  484                                         cc_exec_next(cc) =
  485                                             LIST_NEXT(tmp, c_links.le);
  486                                         cc->cc_bucket = firstb & callwheelmask;
  487                                         LIST_REMOVE(tmp, c_links.le);
  488                                         softclock_call_cc(tmp, cc,
  489 #ifdef CALLOUT_PROFILING
  490                                             &mpcalls_dir, &lockcalls_dir, NULL,
  491 #endif
  492                                             1);
  493                                         tmp = cc_exec_next(cc);
  494                                         cc_exec_next(cc) = NULL;
  495                                 } else {
  496                                         tmpn = LIST_NEXT(tmp, c_links.le);
  497                                         LIST_REMOVE(tmp, c_links.le);
  498                                         TAILQ_INSERT_TAIL(&cc->cc_expireq,
  499                                             tmp, c_links.tqe);
  500                                         tmp->c_flags |= CALLOUT_PROCESSED;
  501                                         tmp = tmpn;
  502                                 }
  503                                 continue;
  504                         }
  505                         /* Skip events from distant future. */
  506                         if (tmp->c_time >= max)
  507                                 goto next;
  508                         /*
  509                          * Event minimal time is bigger than present maximal
  510                          * time, so it cannot be aggregated.
  511                          */
  512                         if (tmp->c_time > last) {
  513                                 lastb = nowb;
  514                                 goto next;
  515                         }
  516                         /* Update first and last time, respecting this event. */
  517                         if (tmp->c_time < first)
  518                                 first = tmp->c_time;
  519                         tmp_max = tmp->c_time + tmp->c_precision;
  520                         if (tmp_max < last)
  521                                 last = tmp_max;
  522 next:
  523                         tmp = LIST_NEXT(tmp, c_links.le);
  524                 }
  525                 /* Proceed with the next bucket. */
  526                 firstb++;
  527                 /*
  528                  * Stop if we looked after present time and found
  529                  * some event we can't execute at now.
  530                  * Stop if we looked far enough into the future.
  531                  */
  532         } while (((int)(firstb - lastb)) <= 0);
  533         cc->cc_firstevent = last;
  534 #ifndef NO_EVENTTIMERS
  535         cpu_new_callout(curcpu, last, first);
  536 #endif
  537 #ifdef CALLOUT_PROFILING
  538         avg_depth_dir += (depth_dir * 1000 - avg_depth_dir) >> 8;
  539         avg_mpcalls_dir += (mpcalls_dir * 1000 - avg_mpcalls_dir) >> 8;
  540         avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
  541 #endif
  542         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  543         /*
  544          * swi_sched acquires the thread lock, so we don't want to call it
  545          * with cc_lock held; incorrect locking order.
  546          */
  547         if (!TAILQ_EMPTY(&cc->cc_expireq))
  548                 swi_sched(cc->cc_cookie, 0);
  549 }
  550 
  551 static struct callout_cpu *
  552 callout_lock(struct callout *c)
  553 {
  554         struct callout_cpu *cc;
  555         int cpu;
  556 
  557         for (;;) {
  558                 cpu = c->c_cpu;
  559 #ifdef SMP
  560                 if (cpu == CPUBLOCK) {
  561                         while (c->c_cpu == CPUBLOCK)
  562                                 cpu_spinwait();
  563                         continue;
  564                 }
  565 #endif
  566                 cc = CC_CPU(cpu);
  567                 CC_LOCK(cc);
  568                 if (cpu == c->c_cpu)
  569                         break;
  570                 CC_UNLOCK(cc);
  571         }
  572         return (cc);
  573 }
  574 
  575 static void
  576 callout_cc_add(struct callout *c, struct callout_cpu *cc,
  577     sbintime_t sbt, sbintime_t precision, void (*func)(void *),
  578     void *arg, int cpu, int flags)
  579 {
  580         int bucket;
  581 
  582         CC_LOCK_ASSERT(cc);
  583         if (sbt < cc->cc_lastscan)
  584                 sbt = cc->cc_lastscan;
  585         c->c_arg = arg;
  586         c->c_flags |= (CALLOUT_ACTIVE | CALLOUT_PENDING);
  587         c->c_flags &= ~CALLOUT_PROCESSED;
  588         c->c_func = func;
  589         c->c_time = sbt;
  590         c->c_precision = precision;
  591         bucket = callout_get_bucket(c->c_time);
  592         CTR3(KTR_CALLOUT, "precision set for %p: %d.%08x",
  593             c, (int)(c->c_precision >> 32),
  594             (u_int)(c->c_precision & 0xffffffff));
  595         LIST_INSERT_HEAD(&cc->cc_callwheel[bucket], c, c_links.le);
  596         if (cc->cc_bucket == bucket)
  597                 cc_exec_next(cc) = c;
  598 #ifndef NO_EVENTTIMERS
  599         /*
  600          * Inform the eventtimers(4) subsystem there's a new callout
  601          * that has been inserted, but only if really required.
  602          */
  603         if (SBT_MAX - c->c_time < c->c_precision)
  604                 c->c_precision = SBT_MAX - c->c_time;
  605         sbt = c->c_time + c->c_precision;
  606         if (sbt < cc->cc_firstevent) {
  607                 cc->cc_firstevent = sbt;
  608                 cpu_new_callout(cpu, sbt, c->c_time);
  609         }
  610 #endif
  611 }
  612 
  613 static void
  614 callout_cc_del(struct callout *c, struct callout_cpu *cc)
  615 {
  616 
  617         if ((c->c_flags & CALLOUT_LOCAL_ALLOC) == 0)
  618                 return;
  619         c->c_func = NULL;
  620         SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  621 }
  622 
  623 static void
  624 softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  625 #ifdef CALLOUT_PROFILING
  626     int *mpcalls, int *lockcalls, int *gcalls,
  627 #endif
  628     int direct)
  629 {
  630         struct rm_priotracker tracker;
  631         void (*c_func)(void *);
  632         void *c_arg;
  633         struct lock_class *class;
  634         struct lock_object *c_lock;
  635         uintptr_t lock_status;
  636         int c_flags;
  637 #ifdef SMP
  638         struct callout_cpu *new_cc;
  639         void (*new_func)(void *);
  640         void *new_arg;
  641         int flags, new_cpu;
  642         sbintime_t new_prec, new_time;
  643 #endif
  644 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING) 
  645         sbintime_t sbt1, sbt2;
  646         struct timespec ts2;
  647         static sbintime_t maxdt = 2 * SBT_1MS;  /* 2 msec */
  648         static timeout_t *lastfunc;
  649 #endif
  650 
  651         KASSERT((c->c_flags & (CALLOUT_PENDING | CALLOUT_ACTIVE)) ==
  652             (CALLOUT_PENDING | CALLOUT_ACTIVE),
  653             ("softclock_call_cc: pend|act %p %x", c, c->c_flags));
  654         class = (c->c_lock != NULL) ? LOCK_CLASS(c->c_lock) : NULL;
  655         lock_status = 0;
  656         if (c->c_flags & CALLOUT_SHAREDLOCK) {
  657                 if (class == &lock_class_rm)
  658                         lock_status = (uintptr_t)&tracker;
  659                 else
  660                         lock_status = 1;
  661         }
  662         c_lock = c->c_lock;
  663         c_func = c->c_func;
  664         c_arg = c->c_arg;
  665         c_flags = c->c_flags;
  666         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
  667                 c->c_flags = CALLOUT_LOCAL_ALLOC;
  668         else
  669                 c->c_flags &= ~CALLOUT_PENDING;
  670         
  671         cc_exec_curr(cc, direct) = c;
  672         cc_exec_cancel(cc, direct) = false;
  673         CC_UNLOCK(cc);
  674         if (c_lock != NULL) {
  675                 class->lc_lock(c_lock, lock_status);
  676                 /*
  677                  * The callout may have been cancelled
  678                  * while we switched locks.
  679                  */
  680                 if (cc_exec_cancel(cc, direct)) {
  681                         class->lc_unlock(c_lock);
  682                         goto skip;
  683                 }
  684                 /* The callout cannot be stopped now. */
  685                 cc_exec_cancel(cc, direct) = true;
  686                 if (c_lock == &Giant.lock_object) {
  687 #ifdef CALLOUT_PROFILING
  688                         (*gcalls)++;
  689 #endif
  690                         CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
  691                             c, c_func, c_arg);
  692                 } else {
  693 #ifdef CALLOUT_PROFILING
  694                         (*lockcalls)++;
  695 #endif
  696                         CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
  697                             c, c_func, c_arg);
  698                 }
  699         } else {
  700 #ifdef CALLOUT_PROFILING
  701                 (*mpcalls)++;
  702 #endif
  703                 CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
  704                     c, c_func, c_arg);
  705         }
  706         KTR_STATE3(KTR_SCHED, "callout", cc->cc_ktr_event_name, "running",
  707             "func:%p", c_func, "arg:%p", c_arg, "direct:%d", direct);
  708 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  709         sbt1 = sbinuptime();
  710 #endif
  711         THREAD_NO_SLEEPING();
  712         SDT_PROBE(callout_execute, kernel, , callout__start, c, 0, 0, 0, 0);
  713         c_func(c_arg);
  714         SDT_PROBE(callout_execute, kernel, , callout__end, c, 0, 0, 0, 0);
  715         THREAD_SLEEPING_OK();
  716 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  717         sbt2 = sbinuptime();
  718         sbt2 -= sbt1;
  719         if (sbt2 > maxdt) {
  720                 if (lastfunc != c_func || sbt2 > maxdt * 2) {
  721                         ts2 = sbttots(sbt2);
  722                         printf(
  723                 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  724                             c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
  725                 }
  726                 maxdt = sbt2;
  727                 lastfunc = c_func;
  728         }
  729 #endif
  730         KTR_STATE0(KTR_SCHED, "callout", cc->cc_ktr_event_name, "idle");
  731         CTR1(KTR_CALLOUT, "callout %p finished", c);
  732         if ((c_flags & CALLOUT_RETURNUNLOCKED) == 0)
  733                 class->lc_unlock(c_lock);
  734 skip:
  735         CC_LOCK(cc);
  736         KASSERT(cc_exec_curr(cc, direct) == c, ("mishandled cc_curr"));
  737         cc_exec_curr(cc, direct) = NULL;
  738         if (cc_exec_waiting(cc, direct)) {
  739                 /*
  740                  * There is someone waiting for the
  741                  * callout to complete.
  742                  * If the callout was scheduled for
  743                  * migration just cancel it.
  744                  */
  745                 if (cc_cce_migrating(cc, direct)) {
  746                         cc_cce_cleanup(cc, direct);
  747 
  748                         /*
  749                          * It should be assert here that the callout is not
  750                          * destroyed but that is not easy.
  751                          */
  752                         c->c_flags &= ~CALLOUT_DFRMIGRATION;
  753                 }
  754                 cc_exec_waiting(cc, direct) = false;
  755                 CC_UNLOCK(cc);
  756                 wakeup(&cc_exec_waiting(cc, direct));
  757                 CC_LOCK(cc);
  758         } else if (cc_cce_migrating(cc, direct)) {
  759                 KASSERT((c_flags & CALLOUT_LOCAL_ALLOC) == 0,
  760                     ("Migrating legacy callout %p", c));
  761 #ifdef SMP
  762                 /*
  763                  * If the callout was scheduled for
  764                  * migration just perform it now.
  765                  */
  766                 new_cpu = cc_migration_cpu(cc, direct);
  767                 new_time = cc_migration_time(cc, direct);
  768                 new_prec = cc_migration_prec(cc, direct);
  769                 new_func = cc_migration_func(cc, direct);
  770                 new_arg = cc_migration_arg(cc, direct);
  771                 cc_cce_cleanup(cc, direct);
  772 
  773                 /*
  774                  * It should be assert here that the callout is not destroyed
  775                  * but that is not easy.
  776                  *
  777                  * As first thing, handle deferred callout stops.
  778                  */
  779                 if (!callout_migrating(c)) {
  780                         CTR3(KTR_CALLOUT,
  781                              "deferred cancelled %p func %p arg %p",
  782                              c, new_func, new_arg);
  783                         callout_cc_del(c, cc);
  784                         return;
  785                 }
  786                 c->c_flags &= ~CALLOUT_DFRMIGRATION;
  787 
  788                 new_cc = callout_cpu_switch(c, cc, new_cpu);
  789                 flags = (direct) ? C_DIRECT_EXEC : 0;
  790                 callout_cc_add(c, new_cc, new_time, new_prec, new_func,
  791                     new_arg, new_cpu, flags);
  792                 CC_UNLOCK(new_cc);
  793                 CC_LOCK(cc);
  794 #else
  795                 panic("migration should not happen");
  796 #endif
  797         }
  798         /*
  799          * If the current callout is locally allocated (from
  800          * timeout(9)) then put it on the freelist.
  801          *
  802          * Note: we need to check the cached copy of c_flags because
  803          * if it was not local, then it's not safe to deref the
  804          * callout pointer.
  805          */
  806         KASSERT((c_flags & CALLOUT_LOCAL_ALLOC) == 0 ||
  807             c->c_flags == CALLOUT_LOCAL_ALLOC,
  808             ("corrupted callout"));
  809         if (c_flags & CALLOUT_LOCAL_ALLOC)
  810                 callout_cc_del(c, cc);
  811 }
  812 
  813 /*
  814  * The callout mechanism is based on the work of Adam M. Costello and
  815  * George Varghese, published in a technical report entitled "Redesigning
  816  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  817  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  818  * used in this implementation was published by G. Varghese and T. Lauck in
  819  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  820  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  821  * the 11th ACM Annual Symposium on Operating Systems Principles,
  822  * Austin, Texas Nov 1987.
  823  */
  824 
  825 /*
  826  * Software (low priority) clock interrupt.
  827  * Run periodic events from timeout queue.
  828  */
  829 void
  830 softclock(void *arg)
  831 {
  832         struct callout_cpu *cc;
  833         struct callout *c;
  834 #ifdef CALLOUT_PROFILING
  835         int depth = 0, gcalls = 0, lockcalls = 0, mpcalls = 0;
  836 #endif
  837 
  838         cc = (struct callout_cpu *)arg;
  839         CC_LOCK(cc);
  840         while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
  841                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
  842                 softclock_call_cc(c, cc,
  843 #ifdef CALLOUT_PROFILING
  844                     &mpcalls, &lockcalls, &gcalls,
  845 #endif
  846                     0);
  847 #ifdef CALLOUT_PROFILING
  848                 ++depth;
  849 #endif
  850         }
  851 #ifdef CALLOUT_PROFILING
  852         avg_depth += (depth * 1000 - avg_depth) >> 8;
  853         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  854         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  855         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  856 #endif
  857         CC_UNLOCK(cc);
  858 }
  859 
  860 /*
  861  * timeout --
  862  *      Execute a function after a specified length of time.
  863  *
  864  * untimeout --
  865  *      Cancel previous timeout function call.
  866  *
  867  * callout_handle_init --
  868  *      Initialize a handle so that using it with untimeout is benign.
  869  *
  870  *      See AT&T BCI Driver Reference Manual for specification.  This
  871  *      implementation differs from that one in that although an
  872  *      identification value is returned from timeout, the original
  873  *      arguments to timeout as well as the identifier are used to
  874  *      identify entries for untimeout.
  875  */
  876 struct callout_handle
  877 timeout(timeout_t *ftn, void *arg, int to_ticks)
  878 {
  879         struct callout_cpu *cc;
  880         struct callout *new;
  881         struct callout_handle handle;
  882 
  883         cc = CC_CPU(timeout_cpu);
  884         CC_LOCK(cc);
  885         /* Fill in the next free callout structure. */
  886         new = SLIST_FIRST(&cc->cc_callfree);
  887         if (new == NULL)
  888                 /* XXX Attempt to malloc first */
  889                 panic("timeout table full");
  890         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  891         callout_reset(new, to_ticks, ftn, arg);
  892         handle.callout = new;
  893         CC_UNLOCK(cc);
  894 
  895         return (handle);
  896 }
  897 
  898 void
  899 untimeout(timeout_t *ftn, void *arg, struct callout_handle handle)
  900 {
  901         struct callout_cpu *cc;
  902 
  903         /*
  904          * Check for a handle that was initialized
  905          * by callout_handle_init, but never used
  906          * for a real timeout.
  907          */
  908         if (handle.callout == NULL)
  909                 return;
  910 
  911         cc = callout_lock(handle.callout);
  912         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  913                 callout_stop(handle.callout);
  914         CC_UNLOCK(cc);
  915 }
  916 
  917 void
  918 callout_handle_init(struct callout_handle *handle)
  919 {
  920         handle->callout = NULL;
  921 }
  922 
  923 /*
  924  * New interface; clients allocate their own callout structures.
  925  *
  926  * callout_reset() - establish or change a timeout
  927  * callout_stop() - disestablish a timeout
  928  * callout_init() - initialize a callout structure so that it can
  929  *      safely be passed to callout_reset() and callout_stop()
  930  *
  931  * <sys/callout.h> defines three convenience macros:
  932  *
  933  * callout_active() - returns truth if callout has not been stopped,
  934  *      drained, or deactivated since the last time the callout was
  935  *      reset.
  936  * callout_pending() - returns truth if callout is still waiting for timeout
  937  * callout_deactivate() - marks the callout as having been serviced
  938  */
  939 int
  940 callout_reset_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t precision,
  941     void (*ftn)(void *), void *arg, int cpu, int flags)
  942 {
  943         sbintime_t to_sbt, pr;
  944         struct callout_cpu *cc;
  945         int cancelled, direct;
  946 
  947         cancelled = 0;
  948         if (flags & C_ABSOLUTE) {
  949                 to_sbt = sbt;
  950         } else {
  951                 if ((flags & C_HARDCLOCK) && (sbt < tick_sbt))
  952                         sbt = tick_sbt;
  953                 if ((flags & C_HARDCLOCK) ||
  954 #ifdef NO_EVENTTIMERS
  955                     sbt >= sbt_timethreshold) {
  956                         to_sbt = getsbinuptime();
  957 
  958                         /* Add safety belt for the case of hz > 1000. */
  959                         to_sbt += tc_tick_sbt - tick_sbt;
  960 #else
  961                     sbt >= sbt_tickthreshold) {
  962                         /*
  963                          * Obtain the time of the last hardclock() call on
  964                          * this CPU directly from the kern_clocksource.c.
  965                          * This value is per-CPU, but it is equal for all
  966                          * active ones.
  967                          */
  968 #ifdef __LP64__
  969                         to_sbt = DPCPU_GET(hardclocktime);
  970 #else
  971                         spinlock_enter();
  972                         to_sbt = DPCPU_GET(hardclocktime);
  973                         spinlock_exit();
  974 #endif
  975 #endif
  976                         if ((flags & C_HARDCLOCK) == 0)
  977                                 to_sbt += tick_sbt;
  978                 } else
  979                         to_sbt = sbinuptime();
  980                 if (SBT_MAX - to_sbt < sbt)
  981                         to_sbt = SBT_MAX;
  982                 else
  983                         to_sbt += sbt;
  984                 pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
  985                     sbt >> C_PRELGET(flags));
  986                 if (pr > precision)
  987                         precision = pr;
  988         }
  989         /*
  990          * Don't allow migration of pre-allocated callouts lest they
  991          * become unbalanced.
  992          */
  993         if (c->c_flags & CALLOUT_LOCAL_ALLOC)
  994                 cpu = c->c_cpu;
  995         /* 
  996          * This flag used to be added by callout_cc_add, but the
  997          * first time you call this we could end up with the
  998          * wrong direct flag if we don't do it before we add.
  999          */
 1000         if (flags & C_DIRECT_EXEC) {
 1001                 c->c_flags |= CALLOUT_DIRECT;
 1002         }
 1003         direct = (c->c_flags & CALLOUT_DIRECT) != 0;
 1004         KASSERT(!direct || c->c_lock == NULL,
 1005             ("%s: direct callout %p has lock", __func__, c));
 1006         cc = callout_lock(c);
 1007         if (cc_exec_curr(cc, direct) == c) {
 1008                 /*
 1009                  * We're being asked to reschedule a callout which is
 1010                  * currently in progress.  If there is a lock then we
 1011                  * can cancel the callout if it has not really started.
 1012                  */
 1013                 if (c->c_lock != NULL && cc_exec_cancel(cc, direct))
 1014                         cancelled = cc_exec_cancel(cc, direct) = true;
 1015                 if (cc_exec_waiting(cc, direct)) {
 1016                         /*
 1017                          * Someone has called callout_drain to kill this
 1018                          * callout.  Don't reschedule.
 1019                          */
 1020                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
 1021                             cancelled ? "cancelled" : "failed to cancel",
 1022                             c, c->c_func, c->c_arg);
 1023                         CC_UNLOCK(cc);
 1024                         return (cancelled);
 1025                 }
 1026 #ifdef SMP
 1027                 if (callout_migrating(c)) {
 1028                         /* 
 1029                          * This only occurs when a second callout_reset_sbt_on
 1030                          * is made after a previous one moved it into
 1031                          * deferred migration (below). Note we do *not* change
 1032                          * the prev_cpu even though the previous target may
 1033                          * be different.
 1034                          */
 1035                         cc_migration_cpu(cc, direct) = cpu;
 1036                         cc_migration_time(cc, direct) = to_sbt;
 1037                         cc_migration_prec(cc, direct) = precision;
 1038                         cc_migration_func(cc, direct) = ftn;
 1039                         cc_migration_arg(cc, direct) = arg;
 1040                         cancelled = 1;
 1041                         CC_UNLOCK(cc);
 1042                         return (cancelled);
 1043                 }
 1044 #endif
 1045         }
 1046         if (c->c_flags & CALLOUT_PENDING) {
 1047                 if ((c->c_flags & CALLOUT_PROCESSED) == 0) {
 1048                         if (cc_exec_next(cc) == c)
 1049                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1050                         LIST_REMOVE(c, c_links.le);
 1051                 } else
 1052                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1053                 cancelled = 1;
 1054                 c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
 1055         }
 1056 
 1057 #ifdef SMP
 1058         /*
 1059          * If the callout must migrate try to perform it immediately.
 1060          * If the callout is currently running, just defer the migration
 1061          * to a more appropriate moment.
 1062          */
 1063         if (c->c_cpu != cpu) {
 1064                 if (cc_exec_curr(cc, direct) == c) {
 1065                         /* 
 1066                          * Pending will have been removed since we are
 1067                          * actually executing the callout on another
 1068                          * CPU. That callout should be waiting on the
 1069                          * lock the caller holds. If we set both
 1070                          * active/and/pending after we return and the
 1071                          * lock on the executing callout proceeds, it
 1072                          * will then see pending is true and return.
 1073                          * At the return from the actual callout execution
 1074                          * the migration will occur in softclock_call_cc
 1075                          * and this new callout will be placed on the 
 1076                          * new CPU via a call to callout_cpu_switch() which
 1077                          * will get the lock on the right CPU followed
 1078                          * by a call callout_cc_add() which will add it there.
 1079                          * (see above in softclock_call_cc()).
 1080                          */
 1081                         cc_migration_cpu(cc, direct) = cpu;
 1082                         cc_migration_time(cc, direct) = to_sbt;
 1083                         cc_migration_prec(cc, direct) = precision;
 1084                         cc_migration_func(cc, direct) = ftn;
 1085                         cc_migration_arg(cc, direct) = arg;
 1086                         c->c_flags |= (CALLOUT_DFRMIGRATION | CALLOUT_ACTIVE | CALLOUT_PENDING);
 1087                         CTR6(KTR_CALLOUT,
 1088                     "migration of %p func %p arg %p in %d.%08x to %u deferred",
 1089                             c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1090                             (u_int)(to_sbt & 0xffffffff), cpu);
 1091                         CC_UNLOCK(cc);
 1092                         return (cancelled);
 1093                 }
 1094                 cc = callout_cpu_switch(c, cc, cpu);
 1095         }
 1096 #endif
 1097 
 1098         callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
 1099         CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
 1100             cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1101             (u_int)(to_sbt & 0xffffffff));
 1102         CC_UNLOCK(cc);
 1103 
 1104         return (cancelled);
 1105 }
 1106 
 1107 /*
 1108  * Common idioms that can be optimized in the future.
 1109  */
 1110 int
 1111 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
 1112 {
 1113         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
 1114 }
 1115 
 1116 int
 1117 callout_schedule(struct callout *c, int to_ticks)
 1118 {
 1119         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
 1120 }
 1121 
 1122 int
 1123 _callout_stop_safe(struct callout *c, int safe)
 1124 {
 1125         struct callout_cpu *cc, *old_cc;
 1126         struct lock_class *class;
 1127         int direct, sq_locked, use_lock;
 1128         int not_on_a_list;
 1129 
 1130         if (safe)
 1131                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
 1132                     "calling %s", __func__);
 1133 
 1134         /*
 1135          * Some old subsystems don't hold Giant while running a callout_stop(),
 1136          * so just discard this check for the moment.
 1137          */
 1138         if (!safe && c->c_lock != NULL) {
 1139                 if (c->c_lock == &Giant.lock_object)
 1140                         use_lock = mtx_owned(&Giant);
 1141                 else {
 1142                         use_lock = 1;
 1143                         class = LOCK_CLASS(c->c_lock);
 1144                         class->lc_assert(c->c_lock, LA_XLOCKED);
 1145                 }
 1146         } else
 1147                 use_lock = 0;
 1148         direct = (c->c_flags & CALLOUT_DIRECT) != 0;
 1149         sq_locked = 0;
 1150         old_cc = NULL;
 1151 again:
 1152         cc = callout_lock(c);
 1153 
 1154         if ((c->c_flags & (CALLOUT_DFRMIGRATION | CALLOUT_ACTIVE | CALLOUT_PENDING)) ==
 1155             (CALLOUT_DFRMIGRATION | CALLOUT_ACTIVE | CALLOUT_PENDING)) {
 1156                 /*
 1157                  * Special case where this slipped in while we
 1158                  * were migrating *as* the callout is about to
 1159                  * execute. The caller probably holds the lock
 1160                  * the callout wants.
 1161                  *
 1162                  * Get rid of the migration first. Then set
 1163                  * the flag that tells this code *not* to
 1164                  * try to remove it from any lists (its not
 1165                  * on one yet). When the callout wheel runs,
 1166                  * it will ignore this callout.
 1167                  */
 1168                 c->c_flags &= ~(CALLOUT_PENDING|CALLOUT_ACTIVE);
 1169                 not_on_a_list = 1;
 1170         } else {
 1171                 not_on_a_list = 0;
 1172         }
 1173 
 1174         /*
 1175          * If the callout was migrating while the callout cpu lock was
 1176          * dropped,  just drop the sleepqueue lock and check the states
 1177          * again.
 1178          */
 1179         if (sq_locked != 0 && cc != old_cc) {
 1180 #ifdef SMP
 1181                 CC_UNLOCK(cc);
 1182                 sleepq_release(&cc_exec_waiting(old_cc, direct));
 1183                 sq_locked = 0;
 1184                 old_cc = NULL;
 1185                 goto again;
 1186 #else
 1187                 panic("migration should not happen");
 1188 #endif
 1189         }
 1190 
 1191         /*
 1192          * If the callout isn't pending, it's not on the queue, so
 1193          * don't attempt to remove it from the queue.  We can try to
 1194          * stop it by other means however.
 1195          */
 1196         if (!(c->c_flags & CALLOUT_PENDING)) {
 1197                 c->c_flags &= ~CALLOUT_ACTIVE;
 1198 
 1199                 /*
 1200                  * If it wasn't on the queue and it isn't the current
 1201                  * callout, then we can't stop it, so just bail.
 1202                  */
 1203                 if (cc_exec_curr(cc, direct) != c) {
 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                         if (sq_locked)
 1208                                 sleepq_release(&cc_exec_waiting(cc, direct));
 1209                         return (0);
 1210                 }
 1211 
 1212                 if (safe) {
 1213                         /*
 1214                          * The current callout is running (or just
 1215                          * about to run) and blocking is allowed, so
 1216                          * just wait for the current invocation to
 1217                          * finish.
 1218                          */
 1219                         while (cc_exec_curr(cc, direct) == c) {
 1220                                 /*
 1221                                  * Use direct calls to sleepqueue interface
 1222                                  * instead of cv/msleep in order to avoid
 1223                                  * a LOR between cc_lock and sleepqueue
 1224                                  * chain spinlocks.  This piece of code
 1225                                  * emulates a msleep_spin() call actually.
 1226                                  *
 1227                                  * If we already have the sleepqueue chain
 1228                                  * locked, then we can safely block.  If we
 1229                                  * don't already have it locked, however,
 1230                                  * we have to drop the cc_lock to lock
 1231                                  * it.  This opens several races, so we
 1232                                  * restart at the beginning once we have
 1233                                  * both locks.  If nothing has changed, then
 1234                                  * we will end up back here with sq_locked
 1235                                  * set.
 1236                                  */
 1237                                 if (!sq_locked) {
 1238                                         CC_UNLOCK(cc);
 1239                                         sleepq_lock(
 1240                                             &cc_exec_waiting(cc, direct));
 1241                                         sq_locked = 1;
 1242                                         old_cc = cc;
 1243                                         goto again;
 1244                                 }
 1245 
 1246                                 /*
 1247                                  * Migration could be cancelled here, but
 1248                                  * as long as it is still not sure when it
 1249                                  * will be packed up, just let softclock()
 1250                                  * take care of it.
 1251                                  */
 1252                                 cc_exec_waiting(cc, direct) = true;
 1253                                 DROP_GIANT();
 1254                                 CC_UNLOCK(cc);
 1255                                 sleepq_add(
 1256                                     &cc_exec_waiting(cc, direct),
 1257                                     &cc->cc_lock.lock_object, "codrain",
 1258                                     SLEEPQ_SLEEP, 0);
 1259                                 sleepq_wait(
 1260                                     &cc_exec_waiting(cc, direct),
 1261                                              0);
 1262                                 sq_locked = 0;
 1263                                 old_cc = NULL;
 1264 
 1265                                 /* Reacquire locks previously released. */
 1266                                 PICKUP_GIANT();
 1267                                 CC_LOCK(cc);
 1268                         }
 1269                 } else if (use_lock &&
 1270                            !cc_exec_cancel(cc, direct)) {
 1271                         
 1272                         /*
 1273                          * The current callout is waiting for its
 1274                          * lock which we hold.  Cancel the callout
 1275                          * and return.  After our caller drops the
 1276                          * lock, the callout will be skipped in
 1277                          * softclock().
 1278                          */
 1279                         cc_exec_cancel(cc, direct) = true;
 1280                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1281                             c, c->c_func, c->c_arg);
 1282                         KASSERT(!cc_cce_migrating(cc, direct),
 1283                             ("callout wrongly scheduled for migration"));
 1284                         CC_UNLOCK(cc);
 1285                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
 1286                         return (1);
 1287                 } else if (callout_migrating(c)) {
 1288                         /*
 1289                          * The callout is currently being serviced
 1290                          * and the "next" callout is scheduled at
 1291                          * its completion with a migration. We remove
 1292                          * the migration flag so it *won't* get rescheduled,
 1293                          * but we can't stop the one thats running so
 1294                          * we return 0.
 1295                          */
 1296                         c->c_flags &= ~CALLOUT_DFRMIGRATION;
 1297 #ifdef SMP
 1298                         /* 
 1299                          * We can't call cc_cce_cleanup here since
 1300                          * if we do it will remove .ce_curr and
 1301                          * its still running. This will prevent a
 1302                          * reschedule of the callout when the 
 1303                          * execution completes.
 1304                          */
 1305                         cc_migration_cpu(cc, direct) = CPUBLOCK;
 1306                         cc_migration_time(cc, direct) = 0;
 1307                         cc_migration_prec(cc, direct) = 0;
 1308                         cc_migration_func(cc, direct) = NULL;
 1309                         cc_migration_arg(cc, direct) = NULL;
 1310 #endif
 1311                         CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
 1312                             c, c->c_func, c->c_arg);
 1313                         CC_UNLOCK(cc);
 1314                         return (0);
 1315                 }
 1316                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1317                     c, c->c_func, c->c_arg);
 1318                 CC_UNLOCK(cc);
 1319                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
 1320                 return (0);
 1321         }
 1322         if (sq_locked)
 1323                 sleepq_release(&cc_exec_waiting(cc, direct));
 1324 
 1325         c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
 1326 
 1327         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1328             c, c->c_func, c->c_arg);
 1329         if (not_on_a_list == 0) {
 1330                 if ((c->c_flags & CALLOUT_PROCESSED) == 0) {
 1331                         if (cc_exec_next(cc) == c)
 1332                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1333                         LIST_REMOVE(c, c_links.le);
 1334                 } else
 1335                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1336         }
 1337         callout_cc_del(c, cc);
 1338         CC_UNLOCK(cc);
 1339         return (1);
 1340 }
 1341 
 1342 void
 1343 callout_init(struct callout *c, int mpsafe)
 1344 {
 1345         bzero(c, sizeof *c);
 1346         if (mpsafe) {
 1347                 c->c_lock = NULL;
 1348                 c->c_flags = CALLOUT_RETURNUNLOCKED;
 1349         } else {
 1350                 c->c_lock = &Giant.lock_object;
 1351                 c->c_flags = 0;
 1352         }
 1353         c->c_cpu = timeout_cpu;
 1354 }
 1355 
 1356 void
 1357 _callout_init_lock(struct callout *c, struct lock_object *lock, int flags)
 1358 {
 1359         bzero(c, sizeof *c);
 1360         c->c_lock = lock;
 1361         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
 1362             ("callout_init_lock: bad flags %d", flags));
 1363         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
 1364             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
 1365         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
 1366             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
 1367             __func__));
 1368         c->c_flags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
 1369         c->c_cpu = timeout_cpu;
 1370 }
 1371 
 1372 #ifdef APM_FIXUP_CALLTODO
 1373 /* 
 1374  * Adjust the kernel calltodo timeout list.  This routine is used after 
 1375  * an APM resume to recalculate the calltodo timer list values with the 
 1376  * number of hz's we have been sleeping.  The next hardclock() will detect 
 1377  * that there are fired timers and run softclock() to execute them.
 1378  *
 1379  * Please note, I have not done an exhaustive analysis of what code this
 1380  * might break.  I am motivated to have my select()'s and alarm()'s that
 1381  * have expired during suspend firing upon resume so that the applications
 1382  * which set the timer can do the maintanence the timer was for as close
 1383  * as possible to the originally intended time.  Testing this code for a 
 1384  * week showed that resuming from a suspend resulted in 22 to 25 timers 
 1385  * firing, which seemed independant on whether the suspend was 2 hours or
 1386  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 1387  */
 1388 void
 1389 adjust_timeout_calltodo(struct timeval *time_change)
 1390 {
 1391         register struct callout *p;
 1392         unsigned long delta_ticks;
 1393 
 1394         /* 
 1395          * How many ticks were we asleep?
 1396          * (stolen from tvtohz()).
 1397          */
 1398 
 1399         /* Don't do anything */
 1400         if (time_change->tv_sec < 0)
 1401                 return;
 1402         else if (time_change->tv_sec <= LONG_MAX / 1000000)
 1403                 delta_ticks = (time_change->tv_sec * 1000000 +
 1404                                time_change->tv_usec + (tick - 1)) / tick + 1;
 1405         else if (time_change->tv_sec <= LONG_MAX / hz)
 1406                 delta_ticks = time_change->tv_sec * hz +
 1407                               (time_change->tv_usec + (tick - 1)) / tick + 1;
 1408         else
 1409                 delta_ticks = LONG_MAX;
 1410 
 1411         if (delta_ticks > INT_MAX)
 1412                 delta_ticks = INT_MAX;
 1413 
 1414         /* 
 1415          * Now rip through the timer calltodo list looking for timers
 1416          * to expire.
 1417          */
 1418 
 1419         /* don't collide with softclock() */
 1420         CC_LOCK(cc);
 1421         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 1422                 p->c_time -= delta_ticks;
 1423 
 1424                 /* Break if the timer had more time on it than delta_ticks */
 1425                 if (p->c_time > 0)
 1426                         break;
 1427 
 1428                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
 1429                 delta_ticks = -p->c_time;
 1430         }
 1431         CC_UNLOCK(cc);
 1432 
 1433         return;
 1434 }
 1435 #endif /* APM_FIXUP_CALLTODO */
 1436 
 1437 static int
 1438 flssbt(sbintime_t sbt)
 1439 {
 1440 
 1441         sbt += (uint64_t)sbt >> 1;
 1442         if (sizeof(long) >= sizeof(sbintime_t))
 1443                 return (flsl(sbt));
 1444         if (sbt >= SBT_1S)
 1445                 return (flsl(((uint64_t)sbt) >> 32) + 32);
 1446         return (flsl(sbt));
 1447 }
 1448 
 1449 /*
 1450  * Dump immediate statistic snapshot of the scheduled callouts.
 1451  */
 1452 static int
 1453 sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
 1454 {
 1455         struct callout *tmp;
 1456         struct callout_cpu *cc;
 1457         struct callout_list *sc;
 1458         sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
 1459         int ct[64], cpr[64], ccpbk[32];
 1460         int error, val, i, count, tcum, pcum, maxc, c, medc;
 1461 #ifdef SMP
 1462         int cpu;
 1463 #endif
 1464 
 1465         val = 0;
 1466         error = sysctl_handle_int(oidp, &val, 0, req);
 1467         if (error != 0 || req->newptr == NULL)
 1468                 return (error);
 1469         count = maxc = 0;
 1470         st = spr = maxt = maxpr = 0;
 1471         bzero(ccpbk, sizeof(ccpbk));
 1472         bzero(ct, sizeof(ct));
 1473         bzero(cpr, sizeof(cpr));
 1474         now = sbinuptime();
 1475 #ifdef SMP
 1476         CPU_FOREACH(cpu) {
 1477                 cc = CC_CPU(cpu);
 1478 #else
 1479                 cc = CC_CPU(timeout_cpu);
 1480 #endif
 1481                 CC_LOCK(cc);
 1482                 for (i = 0; i < callwheelsize; i++) {
 1483                         sc = &cc->cc_callwheel[i];
 1484                         c = 0;
 1485                         LIST_FOREACH(tmp, sc, c_links.le) {
 1486                                 c++;
 1487                                 t = tmp->c_time - now;
 1488                                 if (t < 0)
 1489                                         t = 0;
 1490                                 st += t / SBT_1US;
 1491                                 spr += tmp->c_precision / SBT_1US;
 1492                                 if (t > maxt)
 1493                                         maxt = t;
 1494                                 if (tmp->c_precision > maxpr)
 1495                                         maxpr = tmp->c_precision;
 1496                                 ct[flssbt(t)]++;
 1497                                 cpr[flssbt(tmp->c_precision)]++;
 1498                         }
 1499                         if (c > maxc)
 1500                                 maxc = c;
 1501                         ccpbk[fls(c + c / 2)]++;
 1502                         count += c;
 1503                 }
 1504                 CC_UNLOCK(cc);
 1505 #ifdef SMP
 1506         }
 1507 #endif
 1508 
 1509         for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
 1510                 tcum += ct[i];
 1511         medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1512         for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
 1513                 pcum += cpr[i];
 1514         medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1515         for (i = 0, c = 0; i < 32 && c < count / 2; i++)
 1516                 c += ccpbk[i];
 1517         medc = (i >= 2) ? (1 << (i - 2)) : 0;
 1518 
 1519         printf("Scheduled callouts statistic snapshot:\n");
 1520         printf("  Callouts: %6d  Buckets: %6d*%-3d  Bucket size: 0.%06ds\n",
 1521             count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
 1522         printf("  C/Bk: med %5d         avg %6d.%06jd  max %6d\n",
 1523             medc,
 1524             count / callwheelsize / mp_ncpus,
 1525             (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
 1526             maxc);
 1527         printf("  Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1528             medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
 1529             (st / count) / 1000000, (st / count) % 1000000,
 1530             maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
 1531         printf("  Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1532             medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
 1533             (spr / count) / 1000000, (spr / count) % 1000000,
 1534             maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
 1535         printf("  Distribution:       \tbuckets\t   time\t   tcum\t"
 1536             "   prec\t   pcum\n");
 1537         for (i = 0, tcum = pcum = 0; i < 64; i++) {
 1538                 if (ct[i] == 0 && cpr[i] == 0)
 1539                         continue;
 1540                 t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
 1541                 tcum += ct[i];
 1542                 pcum += cpr[i];
 1543                 printf("  %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
 1544                     t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
 1545                     i - 1 - (32 - CC_HASH_SHIFT),
 1546                     ct[i], tcum, cpr[i], pcum);
 1547         }
 1548         return (error);
 1549 }
 1550 SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
 1551     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 1552     0, 0, sysctl_kern_callout_stat, "I",
 1553     "Dump immediate statistic snapshot of the scheduled callouts");

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