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 302350 2016-07-05 18:47:17Z glebius $");
   39 
   40 #include "opt_callout_profiling.h"
   41 #include "opt_ddb.h"
   42 #if defined(__arm__)
   43 #include "opt_timer.h"
   44 #endif
   45 #include "opt_rss.h"
   46 
   47 #include <sys/param.h>
   48 #include <sys/systm.h>
   49 #include <sys/bus.h>
   50 #include <sys/callout.h>
   51 #include <sys/file.h>
   52 #include <sys/interrupt.h>
   53 #include <sys/kernel.h>
   54 #include <sys/ktr.h>
   55 #include <sys/lock.h>
   56 #include <sys/malloc.h>
   57 #include <sys/mutex.h>
   58 #include <sys/proc.h>
   59 #include <sys/sdt.h>
   60 #include <sys/sleepqueue.h>
   61 #include <sys/sysctl.h>
   62 #include <sys/smp.h>
   63 
   64 #ifdef DDB
   65 #include <ddb/ddb.h>
   66 #include <machine/_inttypes.h>
   67 #endif
   68 
   69 #ifdef SMP
   70 #include <machine/cpu.h>
   71 #endif
   72 
   73 #ifndef NO_EVENTTIMERS
   74 DPCPU_DECLARE(sbintime_t, hardclocktime);
   75 #endif
   76 
   77 SDT_PROVIDER_DEFINE(callout_execute);
   78 SDT_PROBE_DEFINE1(callout_execute, , , callout__start, "struct callout *");
   79 SDT_PROBE_DEFINE1(callout_execute, , , callout__end, "struct callout *");
   80 
   81 #ifdef CALLOUT_PROFILING
   82 static int avg_depth;
   83 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth, CTLFLAG_RD, &avg_depth, 0,
   84     "Average number of items examined per softclock call. Units = 1/1000");
   85 static int avg_gcalls;
   86 SYSCTL_INT(_debug, OID_AUTO, to_avg_gcalls, CTLFLAG_RD, &avg_gcalls, 0,
   87     "Average number of Giant callouts made per softclock call. Units = 1/1000");
   88 static int avg_lockcalls;
   89 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls, CTLFLAG_RD, &avg_lockcalls, 0,
   90     "Average number of lock callouts made per softclock call. Units = 1/1000");
   91 static int avg_mpcalls;
   92 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls, CTLFLAG_RD, &avg_mpcalls, 0,
   93     "Average number of MP callouts made per softclock call. Units = 1/1000");
   94 static int avg_depth_dir;
   95 SYSCTL_INT(_debug, OID_AUTO, to_avg_depth_dir, CTLFLAG_RD, &avg_depth_dir, 0,
   96     "Average number of direct callouts examined per callout_process call. "
   97     "Units = 1/1000");
   98 static int avg_lockcalls_dir;
   99 SYSCTL_INT(_debug, OID_AUTO, to_avg_lockcalls_dir, CTLFLAG_RD,
  100     &avg_lockcalls_dir, 0, "Average number of lock direct callouts made per "
  101     "callout_process call. Units = 1/1000");
  102 static int avg_mpcalls_dir;
  103 SYSCTL_INT(_debug, OID_AUTO, to_avg_mpcalls_dir, CTLFLAG_RD, &avg_mpcalls_dir,
  104     0, "Average number of MP direct callouts made per callout_process call. "
  105     "Units = 1/1000");
  106 #endif
  107 
  108 static int ncallout;
  109 SYSCTL_INT(_kern, OID_AUTO, ncallout, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &ncallout, 0,
  110     "Number of entries in callwheel and size of timeout() preallocation");
  111 
  112 #ifdef  RSS
  113 static int pin_default_swi = 1;
  114 static int pin_pcpu_swi = 1;
  115 #else
  116 static int pin_default_swi = 0;
  117 static int pin_pcpu_swi = 0;
  118 #endif
  119 
  120 SYSCTL_INT(_kern, OID_AUTO, pin_default_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_default_swi,
  121     0, "Pin the default (non-per-cpu) swi (shared with PCPU 0 swi)");
  122 SYSCTL_INT(_kern, OID_AUTO, pin_pcpu_swi, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &pin_pcpu_swi,
  123     0, "Pin the per-CPU swis (except PCPU 0, which is also default");
  124 
  125 /*
  126  * TODO:
  127  *      allocate more timeout table slots when table overflows.
  128  */
  129 u_int callwheelsize, callwheelmask;
  130 
  131 /*
  132  * The callout cpu exec entities represent informations necessary for
  133  * describing the state of callouts currently running on the CPU and the ones
  134  * necessary for migrating callouts to the new callout cpu. In particular,
  135  * the first entry of the array cc_exec_entity holds informations for callout
  136  * running in SWI thread context, while the second one holds informations
  137  * for callout running directly from hardware interrupt context.
  138  * The cached informations are very important for deferring migration when
  139  * the migrating callout is already running.
  140  */
  141 struct cc_exec {
  142         struct callout          *cc_curr;
  143         void                    (*cc_drain)(void *);
  144 #ifdef SMP
  145         void                    (*ce_migration_func)(void *);
  146         void                    *ce_migration_arg;
  147         int                     ce_migration_cpu;
  148         sbintime_t              ce_migration_time;
  149         sbintime_t              ce_migration_prec;
  150 #endif
  151         bool                    cc_cancel;
  152         bool                    cc_waiting;
  153 };
  154 
  155 /*
  156  * There is one struct callout_cpu per cpu, holding all relevant
  157  * state for the callout processing thread on the individual CPU.
  158  */
  159 struct callout_cpu {
  160         struct mtx_padalign     cc_lock;
  161         struct cc_exec          cc_exec_entity[2];
  162         struct callout          *cc_next;
  163         struct callout          *cc_callout;
  164         struct callout_list     *cc_callwheel;
  165         struct callout_tailq    cc_expireq;
  166         struct callout_slist    cc_callfree;
  167         sbintime_t              cc_firstevent;
  168         sbintime_t              cc_lastscan;
  169         void                    *cc_cookie;
  170         u_int                   cc_bucket;
  171         u_int                   cc_inited;
  172         char                    cc_ktr_event_name[20];
  173 };
  174 
  175 #define callout_migrating(c)    ((c)->c_iflags & CALLOUT_DFRMIGRATION)
  176 
  177 #define cc_exec_curr(cc, dir)           cc->cc_exec_entity[dir].cc_curr
  178 #define cc_exec_drain(cc, dir)          cc->cc_exec_entity[dir].cc_drain
  179 #define cc_exec_next(cc)                cc->cc_next
  180 #define cc_exec_cancel(cc, dir)         cc->cc_exec_entity[dir].cc_cancel
  181 #define cc_exec_waiting(cc, dir)        cc->cc_exec_entity[dir].cc_waiting
  182 #ifdef SMP
  183 #define cc_migration_func(cc, dir)      cc->cc_exec_entity[dir].ce_migration_func
  184 #define cc_migration_arg(cc, dir)       cc->cc_exec_entity[dir].ce_migration_arg
  185 #define cc_migration_cpu(cc, dir)       cc->cc_exec_entity[dir].ce_migration_cpu
  186 #define cc_migration_time(cc, dir)      cc->cc_exec_entity[dir].ce_migration_time
  187 #define cc_migration_prec(cc, dir)      cc->cc_exec_entity[dir].ce_migration_prec
  188 
  189 struct callout_cpu cc_cpu[MAXCPU];
  190 #define CPUBLOCK        MAXCPU
  191 #define CC_CPU(cpu)     (&cc_cpu[(cpu)])
  192 #define CC_SELF()       CC_CPU(PCPU_GET(cpuid))
  193 #else
  194 struct callout_cpu cc_cpu;
  195 #define CC_CPU(cpu)     &cc_cpu
  196 #define CC_SELF()       &cc_cpu
  197 #endif
  198 #define CC_LOCK(cc)     mtx_lock_spin(&(cc)->cc_lock)
  199 #define CC_UNLOCK(cc)   mtx_unlock_spin(&(cc)->cc_lock)
  200 #define CC_LOCK_ASSERT(cc)      mtx_assert(&(cc)->cc_lock, MA_OWNED)
  201 
  202 static int timeout_cpu;
  203 
  204 static void     callout_cpu_init(struct callout_cpu *cc, int cpu);
  205 static void     softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  206 #ifdef CALLOUT_PROFILING
  207                     int *mpcalls, int *lockcalls, int *gcalls,
  208 #endif
  209                     int direct);
  210 
  211 static MALLOC_DEFINE(M_CALLOUT, "callout", "Callout datastructures");
  212 
  213 /**
  214  * Locked by cc_lock:
  215  *   cc_curr         - If a callout is in progress, it is cc_curr.
  216  *                     If cc_curr is non-NULL, threads waiting in
  217  *                     callout_drain() will be woken up as soon as the
  218  *                     relevant callout completes.
  219  *   cc_cancel       - Changing to 1 with both callout_lock and cc_lock held
  220  *                     guarantees that the current callout will not run.
  221  *                     The softclock() function sets this to 0 before it
  222  *                     drops callout_lock to acquire c_lock, and it calls
  223  *                     the handler only if curr_cancelled is still 0 after
  224  *                     cc_lock is successfully acquired.
  225  *   cc_waiting      - If a thread is waiting in callout_drain(), then
  226  *                     callout_wait is nonzero.  Set only when
  227  *                     cc_curr is non-NULL.
  228  */
  229 
  230 /*
  231  * Resets the execution entity tied to a specific callout cpu.
  232  */
  233 static void
  234 cc_cce_cleanup(struct callout_cpu *cc, int direct)
  235 {
  236 
  237         cc_exec_curr(cc, direct) = NULL;
  238         cc_exec_cancel(cc, direct) = false;
  239         cc_exec_waiting(cc, direct) = false;
  240 #ifdef SMP
  241         cc_migration_cpu(cc, direct) = CPUBLOCK;
  242         cc_migration_time(cc, direct) = 0;
  243         cc_migration_prec(cc, direct) = 0;
  244         cc_migration_func(cc, direct) = NULL;
  245         cc_migration_arg(cc, direct) = NULL;
  246 #endif
  247 }
  248 
  249 /*
  250  * Checks if migration is requested by a specific callout cpu.
  251  */
  252 static int
  253 cc_cce_migrating(struct callout_cpu *cc, int direct)
  254 {
  255 
  256 #ifdef SMP
  257         return (cc_migration_cpu(cc, direct) != CPUBLOCK);
  258 #else
  259         return (0);
  260 #endif
  261 }
  262 
  263 /*
  264  * Kernel low level callwheel initialization
  265  * called on cpu0 during kernel startup.
  266  */
  267 static void
  268 callout_callwheel_init(void *dummy)
  269 {
  270         struct callout_cpu *cc;
  271 
  272         /*
  273          * Calculate the size of the callout wheel and the preallocated
  274          * timeout() structures.
  275          * XXX: Clip callout to result of previous function of maxusers
  276          * maximum 384.  This is still huge, but acceptable.
  277          */
  278         memset(CC_CPU(0), 0, sizeof(cc_cpu));
  279         ncallout = imin(16 + maxproc + maxfiles, 18508);
  280         TUNABLE_INT_FETCH("kern.ncallout", &ncallout);
  281 
  282         /*
  283          * Calculate callout wheel size, should be next power of two higher
  284          * than 'ncallout'.
  285          */
  286         callwheelsize = 1 << fls(ncallout);
  287         callwheelmask = callwheelsize - 1;
  288 
  289         /*
  290          * Fetch whether we're pinning the swi's or not.
  291          */
  292         TUNABLE_INT_FETCH("kern.pin_default_swi", &pin_default_swi);
  293         TUNABLE_INT_FETCH("kern.pin_pcpu_swi", &pin_pcpu_swi);
  294 
  295         /*
  296          * Only cpu0 handles timeout(9) and receives a preallocation.
  297          *
  298          * XXX: Once all timeout(9) consumers are converted this can
  299          * be removed.
  300          */
  301         timeout_cpu = PCPU_GET(cpuid);
  302         cc = CC_CPU(timeout_cpu);
  303         cc->cc_callout = malloc(ncallout * sizeof(struct callout),
  304             M_CALLOUT, M_WAITOK);
  305         callout_cpu_init(cc, timeout_cpu);
  306 }
  307 SYSINIT(callwheel_init, SI_SUB_CPU, SI_ORDER_ANY, callout_callwheel_init, NULL);
  308 
  309 /*
  310  * Initialize the per-cpu callout structures.
  311  */
  312 static void
  313 callout_cpu_init(struct callout_cpu *cc, int cpu)
  314 {
  315         struct callout *c;
  316         int i;
  317 
  318         mtx_init(&cc->cc_lock, "callout", NULL, MTX_SPIN | MTX_RECURSE);
  319         SLIST_INIT(&cc->cc_callfree);
  320         cc->cc_inited = 1;
  321         cc->cc_callwheel = malloc(sizeof(struct callout_list) * callwheelsize,
  322             M_CALLOUT, M_WAITOK);
  323         for (i = 0; i < callwheelsize; i++)
  324                 LIST_INIT(&cc->cc_callwheel[i]);
  325         TAILQ_INIT(&cc->cc_expireq);
  326         cc->cc_firstevent = SBT_MAX;
  327         for (i = 0; i < 2; i++)
  328                 cc_cce_cleanup(cc, i);
  329         snprintf(cc->cc_ktr_event_name, sizeof(cc->cc_ktr_event_name),
  330             "callwheel cpu %d", cpu);
  331         if (cc->cc_callout == NULL)     /* Only cpu0 handles timeout(9) */
  332                 return;
  333         for (i = 0; i < ncallout; i++) {
  334                 c = &cc->cc_callout[i];
  335                 callout_init(c, 0);
  336                 c->c_iflags = CALLOUT_LOCAL_ALLOC;
  337                 SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  338         }
  339 }
  340 
  341 #ifdef SMP
  342 /*
  343  * Switches the cpu tied to a specific callout.
  344  * The function expects a locked incoming callout cpu and returns with
  345  * locked outcoming callout cpu.
  346  */
  347 static struct callout_cpu *
  348 callout_cpu_switch(struct callout *c, struct callout_cpu *cc, int new_cpu)
  349 {
  350         struct callout_cpu *new_cc;
  351 
  352         MPASS(c != NULL && cc != NULL);
  353         CC_LOCK_ASSERT(cc);
  354 
  355         /*
  356          * Avoid interrupts and preemption firing after the callout cpu
  357          * is blocked in order to avoid deadlocks as the new thread
  358          * may be willing to acquire the callout cpu lock.
  359          */
  360         c->c_cpu = CPUBLOCK;
  361         spinlock_enter();
  362         CC_UNLOCK(cc);
  363         new_cc = CC_CPU(new_cpu);
  364         CC_LOCK(new_cc);
  365         spinlock_exit();
  366         c->c_cpu = new_cpu;
  367         return (new_cc);
  368 }
  369 #endif
  370 
  371 /*
  372  * Start standard softclock thread.
  373  */
  374 static void
  375 start_softclock(void *dummy)
  376 {
  377         struct callout_cpu *cc;
  378         char name[MAXCOMLEN];
  379 #ifdef SMP
  380         int cpu;
  381         struct intr_event *ie;
  382 #endif
  383 
  384         cc = CC_CPU(timeout_cpu);
  385         snprintf(name, sizeof(name), "clock (%d)", timeout_cpu);
  386         if (swi_add(&clk_intr_event, name, softclock, cc, SWI_CLOCK,
  387             INTR_MPSAFE, &cc->cc_cookie))
  388                 panic("died while creating standard software ithreads");
  389         if (pin_default_swi &&
  390             (intr_event_bind(clk_intr_event, timeout_cpu) != 0)) {
  391                 printf("%s: timeout clock couldn't be pinned to cpu %d\n",
  392                     __func__,
  393                     timeout_cpu);
  394         }
  395 
  396 #ifdef SMP
  397         CPU_FOREACH(cpu) {
  398                 if (cpu == timeout_cpu)
  399                         continue;
  400                 cc = CC_CPU(cpu);
  401                 cc->cc_callout = NULL;  /* Only cpu0 handles timeout(9). */
  402                 callout_cpu_init(cc, cpu);
  403                 snprintf(name, sizeof(name), "clock (%d)", cpu);
  404                 ie = NULL;
  405                 if (swi_add(&ie, name, softclock, cc, SWI_CLOCK,
  406                     INTR_MPSAFE, &cc->cc_cookie))
  407                         panic("died while creating standard software ithreads");
  408                 if (pin_pcpu_swi && (intr_event_bind(ie, cpu) != 0)) {
  409                         printf("%s: per-cpu clock couldn't be pinned to "
  410                             "cpu %d\n",
  411                             __func__,
  412                             cpu);
  413                 }
  414         }
  415 #endif
  416 }
  417 SYSINIT(start_softclock, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_softclock, NULL);
  418 
  419 #define CC_HASH_SHIFT   8
  420 
  421 static inline u_int
  422 callout_hash(sbintime_t sbt)
  423 {
  424 
  425         return (sbt >> (32 - CC_HASH_SHIFT));
  426 }
  427 
  428 static inline u_int
  429 callout_get_bucket(sbintime_t sbt)
  430 {
  431 
  432         return (callout_hash(sbt) & callwheelmask);
  433 }
  434 
  435 void
  436 callout_process(sbintime_t now)
  437 {
  438         struct callout *tmp, *tmpn;
  439         struct callout_cpu *cc;
  440         struct callout_list *sc;
  441         sbintime_t first, last, max, tmp_max;
  442         uint32_t lookahead;
  443         u_int firstb, lastb, nowb;
  444 #ifdef CALLOUT_PROFILING
  445         int depth_dir = 0, mpcalls_dir = 0, lockcalls_dir = 0;
  446 #endif
  447 
  448         cc = CC_SELF();
  449         mtx_lock_spin_flags(&cc->cc_lock, MTX_QUIET);
  450 
  451         /* Compute the buckets of the last scan and present times. */
  452         firstb = callout_hash(cc->cc_lastscan);
  453         cc->cc_lastscan = now;
  454         nowb = callout_hash(now);
  455 
  456         /* Compute the last bucket and minimum time of the bucket after it. */
  457         if (nowb == firstb)
  458                 lookahead = (SBT_1S / 16);
  459         else if (nowb - firstb == 1)
  460                 lookahead = (SBT_1S / 8);
  461         else
  462                 lookahead = (SBT_1S / 2);
  463         first = last = now;
  464         first += (lookahead / 2);
  465         last += lookahead;
  466         last &= (0xffffffffffffffffLLU << (32 - CC_HASH_SHIFT));
  467         lastb = callout_hash(last) - 1;
  468         max = last;
  469 
  470         /*
  471          * Check if we wrapped around the entire wheel from the last scan.
  472          * In case, we need to scan entirely the wheel for pending callouts.
  473          */
  474         if (lastb - firstb >= callwheelsize) {
  475                 lastb = firstb + callwheelsize - 1;
  476                 if (nowb - firstb >= callwheelsize)
  477                         nowb = lastb;
  478         }
  479 
  480         /* Iterate callwheel from firstb to nowb and then up to lastb. */
  481         do {
  482                 sc = &cc->cc_callwheel[firstb & callwheelmask];
  483                 tmp = LIST_FIRST(sc);
  484                 while (tmp != NULL) {
  485                         /* Run the callout if present time within allowed. */
  486                         if (tmp->c_time <= now) {
  487                                 /*
  488                                  * Consumer told us the callout may be run
  489                                  * directly from hardware interrupt context.
  490                                  */
  491                                 if (tmp->c_iflags & CALLOUT_DIRECT) {
  492 #ifdef CALLOUT_PROFILING
  493                                         ++depth_dir;
  494 #endif
  495                                         cc_exec_next(cc) =
  496                                             LIST_NEXT(tmp, c_links.le);
  497                                         cc->cc_bucket = firstb & callwheelmask;
  498                                         LIST_REMOVE(tmp, c_links.le);
  499                                         softclock_call_cc(tmp, cc,
  500 #ifdef CALLOUT_PROFILING
  501                                             &mpcalls_dir, &lockcalls_dir, NULL,
  502 #endif
  503                                             1);
  504                                         tmp = cc_exec_next(cc);
  505                                         cc_exec_next(cc) = NULL;
  506                                 } else {
  507                                         tmpn = LIST_NEXT(tmp, c_links.le);
  508                                         LIST_REMOVE(tmp, c_links.le);
  509                                         TAILQ_INSERT_TAIL(&cc->cc_expireq,
  510                                             tmp, c_links.tqe);
  511                                         tmp->c_iflags |= CALLOUT_PROCESSED;
  512                                         tmp = tmpn;
  513                                 }
  514                                 continue;
  515                         }
  516                         /* Skip events from distant future. */
  517                         if (tmp->c_time >= max)
  518                                 goto next;
  519                         /*
  520                          * Event minimal time is bigger than present maximal
  521                          * time, so it cannot be aggregated.
  522                          */
  523                         if (tmp->c_time > last) {
  524                                 lastb = nowb;
  525                                 goto next;
  526                         }
  527                         /* Update first and last time, respecting this event. */
  528                         if (tmp->c_time < first)
  529                                 first = tmp->c_time;
  530                         tmp_max = tmp->c_time + tmp->c_precision;
  531                         if (tmp_max < last)
  532                                 last = tmp_max;
  533 next:
  534                         tmp = LIST_NEXT(tmp, c_links.le);
  535                 }
  536                 /* Proceed with the next bucket. */
  537                 firstb++;
  538                 /*
  539                  * Stop if we looked after present time and found
  540                  * some event we can't execute at now.
  541                  * Stop if we looked far enough into the future.
  542                  */
  543         } while (((int)(firstb - lastb)) <= 0);
  544         cc->cc_firstevent = last;
  545 #ifndef NO_EVENTTIMERS
  546         cpu_new_callout(curcpu, last, first);
  547 #endif
  548 #ifdef CALLOUT_PROFILING
  549         avg_depth_dir += (depth_dir * 1000 - avg_depth_dir) >> 8;
  550         avg_mpcalls_dir += (mpcalls_dir * 1000 - avg_mpcalls_dir) >> 8;
  551         avg_lockcalls_dir += (lockcalls_dir * 1000 - avg_lockcalls_dir) >> 8;
  552 #endif
  553         mtx_unlock_spin_flags(&cc->cc_lock, MTX_QUIET);
  554         /*
  555          * swi_sched acquires the thread lock, so we don't want to call it
  556          * with cc_lock held; incorrect locking order.
  557          */
  558         if (!TAILQ_EMPTY(&cc->cc_expireq))
  559                 swi_sched(cc->cc_cookie, 0);
  560 }
  561 
  562 static struct callout_cpu *
  563 callout_lock(struct callout *c)
  564 {
  565         struct callout_cpu *cc;
  566         int cpu;
  567 
  568         for (;;) {
  569                 cpu = c->c_cpu;
  570 #ifdef SMP
  571                 if (cpu == CPUBLOCK) {
  572                         while (c->c_cpu == CPUBLOCK)
  573                                 cpu_spinwait();
  574                         continue;
  575                 }
  576 #endif
  577                 cc = CC_CPU(cpu);
  578                 CC_LOCK(cc);
  579                 if (cpu == c->c_cpu)
  580                         break;
  581                 CC_UNLOCK(cc);
  582         }
  583         return (cc);
  584 }
  585 
  586 static void
  587 callout_cc_add(struct callout *c, struct callout_cpu *cc,
  588     sbintime_t sbt, sbintime_t precision, void (*func)(void *),
  589     void *arg, int cpu, int flags)
  590 {
  591         int bucket;
  592 
  593         CC_LOCK_ASSERT(cc);
  594         if (sbt < cc->cc_lastscan)
  595                 sbt = cc->cc_lastscan;
  596         c->c_arg = arg;
  597         c->c_iflags |= CALLOUT_PENDING;
  598         c->c_iflags &= ~CALLOUT_PROCESSED;
  599         c->c_flags |= CALLOUT_ACTIVE;
  600         if (flags & C_DIRECT_EXEC)
  601                 c->c_iflags |= CALLOUT_DIRECT;
  602         c->c_func = func;
  603         c->c_time = sbt;
  604         c->c_precision = precision;
  605         bucket = callout_get_bucket(c->c_time);
  606         CTR3(KTR_CALLOUT, "precision set for %p: %d.%08x",
  607             c, (int)(c->c_precision >> 32),
  608             (u_int)(c->c_precision & 0xffffffff));
  609         LIST_INSERT_HEAD(&cc->cc_callwheel[bucket], c, c_links.le);
  610         if (cc->cc_bucket == bucket)
  611                 cc_exec_next(cc) = c;
  612 #ifndef NO_EVENTTIMERS
  613         /*
  614          * Inform the eventtimers(4) subsystem there's a new callout
  615          * that has been inserted, but only if really required.
  616          */
  617         if (SBT_MAX - c->c_time < c->c_precision)
  618                 c->c_precision = SBT_MAX - c->c_time;
  619         sbt = c->c_time + c->c_precision;
  620         if (sbt < cc->cc_firstevent) {
  621                 cc->cc_firstevent = sbt;
  622                 cpu_new_callout(cpu, sbt, c->c_time);
  623         }
  624 #endif
  625 }
  626 
  627 static void
  628 callout_cc_del(struct callout *c, struct callout_cpu *cc)
  629 {
  630 
  631         if ((c->c_iflags & CALLOUT_LOCAL_ALLOC) == 0)
  632                 return;
  633         c->c_func = NULL;
  634         SLIST_INSERT_HEAD(&cc->cc_callfree, c, c_links.sle);
  635 }
  636 
  637 static void
  638 softclock_call_cc(struct callout *c, struct callout_cpu *cc,
  639 #ifdef CALLOUT_PROFILING
  640     int *mpcalls, int *lockcalls, int *gcalls,
  641 #endif
  642     int direct)
  643 {
  644         struct rm_priotracker tracker;
  645         void (*c_func)(void *);
  646         void *c_arg;
  647         struct lock_class *class;
  648         struct lock_object *c_lock;
  649         uintptr_t lock_status;
  650         int c_iflags;
  651 #ifdef SMP
  652         struct callout_cpu *new_cc;
  653         void (*new_func)(void *);
  654         void *new_arg;
  655         int flags, new_cpu;
  656         sbintime_t new_prec, new_time;
  657 #endif
  658 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING) 
  659         sbintime_t sbt1, sbt2;
  660         struct timespec ts2;
  661         static sbintime_t maxdt = 2 * SBT_1MS;  /* 2 msec */
  662         static timeout_t *lastfunc;
  663 #endif
  664 
  665         KASSERT((c->c_iflags & CALLOUT_PENDING) == CALLOUT_PENDING,
  666             ("softclock_call_cc: pend %p %x", c, c->c_iflags));
  667         KASSERT((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE,
  668             ("softclock_call_cc: act %p %x", c, c->c_flags));
  669         class = (c->c_lock != NULL) ? LOCK_CLASS(c->c_lock) : NULL;
  670         lock_status = 0;
  671         if (c->c_flags & CALLOUT_SHAREDLOCK) {
  672                 if (class == &lock_class_rm)
  673                         lock_status = (uintptr_t)&tracker;
  674                 else
  675                         lock_status = 1;
  676         }
  677         c_lock = c->c_lock;
  678         c_func = c->c_func;
  679         c_arg = c->c_arg;
  680         c_iflags = c->c_iflags;
  681         if (c->c_iflags & CALLOUT_LOCAL_ALLOC)
  682                 c->c_iflags = CALLOUT_LOCAL_ALLOC;
  683         else
  684                 c->c_iflags &= ~CALLOUT_PENDING;
  685         
  686         cc_exec_curr(cc, direct) = c;
  687         cc_exec_cancel(cc, direct) = false;
  688         cc_exec_drain(cc, direct) = NULL;
  689         CC_UNLOCK(cc);
  690         if (c_lock != NULL) {
  691                 class->lc_lock(c_lock, lock_status);
  692                 /*
  693                  * The callout may have been cancelled
  694                  * while we switched locks.
  695                  */
  696                 if (cc_exec_cancel(cc, direct)) {
  697                         class->lc_unlock(c_lock);
  698                         goto skip;
  699                 }
  700                 /* The callout cannot be stopped now. */
  701                 cc_exec_cancel(cc, direct) = true;
  702                 if (c_lock == &Giant.lock_object) {
  703 #ifdef CALLOUT_PROFILING
  704                         (*gcalls)++;
  705 #endif
  706                         CTR3(KTR_CALLOUT, "callout giant %p func %p arg %p",
  707                             c, c_func, c_arg);
  708                 } else {
  709 #ifdef CALLOUT_PROFILING
  710                         (*lockcalls)++;
  711 #endif
  712                         CTR3(KTR_CALLOUT, "callout lock %p func %p arg %p",
  713                             c, c_func, c_arg);
  714                 }
  715         } else {
  716 #ifdef CALLOUT_PROFILING
  717                 (*mpcalls)++;
  718 #endif
  719                 CTR3(KTR_CALLOUT, "callout %p func %p arg %p",
  720                     c, c_func, c_arg);
  721         }
  722         KTR_STATE3(KTR_SCHED, "callout", cc->cc_ktr_event_name, "running",
  723             "func:%p", c_func, "arg:%p", c_arg, "direct:%d", direct);
  724 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  725         sbt1 = sbinuptime();
  726 #endif
  727         THREAD_NO_SLEEPING();
  728         SDT_PROBE1(callout_execute, , , callout__start, c);
  729         c_func(c_arg);
  730         SDT_PROBE1(callout_execute, , , callout__end, c);
  731         THREAD_SLEEPING_OK();
  732 #if defined(DIAGNOSTIC) || defined(CALLOUT_PROFILING)
  733         sbt2 = sbinuptime();
  734         sbt2 -= sbt1;
  735         if (sbt2 > maxdt) {
  736                 if (lastfunc != c_func || sbt2 > maxdt * 2) {
  737                         ts2 = sbttots(sbt2);
  738                         printf(
  739                 "Expensive timeout(9) function: %p(%p) %jd.%09ld s\n",
  740                             c_func, c_arg, (intmax_t)ts2.tv_sec, ts2.tv_nsec);
  741                 }
  742                 maxdt = sbt2;
  743                 lastfunc = c_func;
  744         }
  745 #endif
  746         KTR_STATE0(KTR_SCHED, "callout", cc->cc_ktr_event_name, "idle");
  747         CTR1(KTR_CALLOUT, "callout %p finished", c);
  748         if ((c_iflags & CALLOUT_RETURNUNLOCKED) == 0)
  749                 class->lc_unlock(c_lock);
  750 skip:
  751         CC_LOCK(cc);
  752         KASSERT(cc_exec_curr(cc, direct) == c, ("mishandled cc_curr"));
  753         cc_exec_curr(cc, direct) = NULL;
  754         if (cc_exec_drain(cc, direct)) {
  755                 void (*drain)(void *);
  756                 
  757                 drain = cc_exec_drain(cc, direct);
  758                 cc_exec_drain(cc, direct) = NULL;
  759                 CC_UNLOCK(cc);
  760                 drain(c_arg);
  761                 CC_LOCK(cc);
  762         }
  763         if (cc_exec_waiting(cc, direct)) {
  764                 /*
  765                  * There is someone waiting for the
  766                  * callout to complete.
  767                  * If the callout was scheduled for
  768                  * migration just cancel it.
  769                  */
  770                 if (cc_cce_migrating(cc, direct)) {
  771                         cc_cce_cleanup(cc, direct);
  772 
  773                         /*
  774                          * It should be assert here that the callout is not
  775                          * destroyed but that is not easy.
  776                          */
  777                         c->c_iflags &= ~CALLOUT_DFRMIGRATION;
  778                 }
  779                 cc_exec_waiting(cc, direct) = false;
  780                 CC_UNLOCK(cc);
  781                 wakeup(&cc_exec_waiting(cc, direct));
  782                 CC_LOCK(cc);
  783         } else if (cc_cce_migrating(cc, direct)) {
  784                 KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0,
  785                     ("Migrating legacy callout %p", c));
  786 #ifdef SMP
  787                 /*
  788                  * If the callout was scheduled for
  789                  * migration just perform it now.
  790                  */
  791                 new_cpu = cc_migration_cpu(cc, direct);
  792                 new_time = cc_migration_time(cc, direct);
  793                 new_prec = cc_migration_prec(cc, direct);
  794                 new_func = cc_migration_func(cc, direct);
  795                 new_arg = cc_migration_arg(cc, direct);
  796                 cc_cce_cleanup(cc, direct);
  797 
  798                 /*
  799                  * It should be assert here that the callout is not destroyed
  800                  * but that is not easy.
  801                  *
  802                  * As first thing, handle deferred callout stops.
  803                  */
  804                 if (!callout_migrating(c)) {
  805                         CTR3(KTR_CALLOUT,
  806                              "deferred cancelled %p func %p arg %p",
  807                              c, new_func, new_arg);
  808                         callout_cc_del(c, cc);
  809                         return;
  810                 }
  811                 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
  812 
  813                 new_cc = callout_cpu_switch(c, cc, new_cpu);
  814                 flags = (direct) ? C_DIRECT_EXEC : 0;
  815                 callout_cc_add(c, new_cc, new_time, new_prec, new_func,
  816                     new_arg, new_cpu, flags);
  817                 CC_UNLOCK(new_cc);
  818                 CC_LOCK(cc);
  819 #else
  820                 panic("migration should not happen");
  821 #endif
  822         }
  823         /*
  824          * If the current callout is locally allocated (from
  825          * timeout(9)) then put it on the freelist.
  826          *
  827          * Note: we need to check the cached copy of c_iflags because
  828          * if it was not local, then it's not safe to deref the
  829          * callout pointer.
  830          */
  831         KASSERT((c_iflags & CALLOUT_LOCAL_ALLOC) == 0 ||
  832             c->c_iflags == CALLOUT_LOCAL_ALLOC,
  833             ("corrupted callout"));
  834         if (c_iflags & CALLOUT_LOCAL_ALLOC)
  835                 callout_cc_del(c, cc);
  836 }
  837 
  838 /*
  839  * The callout mechanism is based on the work of Adam M. Costello and
  840  * George Varghese, published in a technical report entitled "Redesigning
  841  * the BSD Callout and Timer Facilities" and modified slightly for inclusion
  842  * in FreeBSD by Justin T. Gibbs.  The original work on the data structures
  843  * used in this implementation was published by G. Varghese and T. Lauck in
  844  * the paper "Hashed and Hierarchical Timing Wheels: Data Structures for
  845  * the Efficient Implementation of a Timer Facility" in the Proceedings of
  846  * the 11th ACM Annual Symposium on Operating Systems Principles,
  847  * Austin, Texas Nov 1987.
  848  */
  849 
  850 /*
  851  * Software (low priority) clock interrupt.
  852  * Run periodic events from timeout queue.
  853  */
  854 void
  855 softclock(void *arg)
  856 {
  857         struct callout_cpu *cc;
  858         struct callout *c;
  859 #ifdef CALLOUT_PROFILING
  860         int depth = 0, gcalls = 0, lockcalls = 0, mpcalls = 0;
  861 #endif
  862 
  863         cc = (struct callout_cpu *)arg;
  864         CC_LOCK(cc);
  865         while ((c = TAILQ_FIRST(&cc->cc_expireq)) != NULL) {
  866                 TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
  867                 softclock_call_cc(c, cc,
  868 #ifdef CALLOUT_PROFILING
  869                     &mpcalls, &lockcalls, &gcalls,
  870 #endif
  871                     0);
  872 #ifdef CALLOUT_PROFILING
  873                 ++depth;
  874 #endif
  875         }
  876 #ifdef CALLOUT_PROFILING
  877         avg_depth += (depth * 1000 - avg_depth) >> 8;
  878         avg_mpcalls += (mpcalls * 1000 - avg_mpcalls) >> 8;
  879         avg_lockcalls += (lockcalls * 1000 - avg_lockcalls) >> 8;
  880         avg_gcalls += (gcalls * 1000 - avg_gcalls) >> 8;
  881 #endif
  882         CC_UNLOCK(cc);
  883 }
  884 
  885 /*
  886  * timeout --
  887  *      Execute a function after a specified length of time.
  888  *
  889  * untimeout --
  890  *      Cancel previous timeout function call.
  891  *
  892  * callout_handle_init --
  893  *      Initialize a handle so that using it with untimeout is benign.
  894  *
  895  *      See AT&T BCI Driver Reference Manual for specification.  This
  896  *      implementation differs from that one in that although an
  897  *      identification value is returned from timeout, the original
  898  *      arguments to timeout as well as the identifier are used to
  899  *      identify entries for untimeout.
  900  */
  901 struct callout_handle
  902 timeout(timeout_t *ftn, void *arg, int to_ticks)
  903 {
  904         struct callout_cpu *cc;
  905         struct callout *new;
  906         struct callout_handle handle;
  907 
  908         cc = CC_CPU(timeout_cpu);
  909         CC_LOCK(cc);
  910         /* Fill in the next free callout structure. */
  911         new = SLIST_FIRST(&cc->cc_callfree);
  912         if (new == NULL)
  913                 /* XXX Attempt to malloc first */
  914                 panic("timeout table full");
  915         SLIST_REMOVE_HEAD(&cc->cc_callfree, c_links.sle);
  916         callout_reset(new, to_ticks, ftn, arg);
  917         handle.callout = new;
  918         CC_UNLOCK(cc);
  919 
  920         return (handle);
  921 }
  922 
  923 void
  924 untimeout(timeout_t *ftn, void *arg, struct callout_handle handle)
  925 {
  926         struct callout_cpu *cc;
  927 
  928         /*
  929          * Check for a handle that was initialized
  930          * by callout_handle_init, but never used
  931          * for a real timeout.
  932          */
  933         if (handle.callout == NULL)
  934                 return;
  935 
  936         cc = callout_lock(handle.callout);
  937         if (handle.callout->c_func == ftn && handle.callout->c_arg == arg)
  938                 callout_stop(handle.callout);
  939         CC_UNLOCK(cc);
  940 }
  941 
  942 void
  943 callout_handle_init(struct callout_handle *handle)
  944 {
  945         handle->callout = NULL;
  946 }
  947 
  948 /*
  949  * New interface; clients allocate their own callout structures.
  950  *
  951  * callout_reset() - establish or change a timeout
  952  * callout_stop() - disestablish a timeout
  953  * callout_init() - initialize a callout structure so that it can
  954  *      safely be passed to callout_reset() and callout_stop()
  955  *
  956  * <sys/callout.h> defines three convenience macros:
  957  *
  958  * callout_active() - returns truth if callout has not been stopped,
  959  *      drained, or deactivated since the last time the callout was
  960  *      reset.
  961  * callout_pending() - returns truth if callout is still waiting for timeout
  962  * callout_deactivate() - marks the callout as having been serviced
  963  */
  964 int
  965 callout_reset_sbt_on(struct callout *c, sbintime_t sbt, sbintime_t precision,
  966     void (*ftn)(void *), void *arg, int cpu, int flags)
  967 {
  968         sbintime_t to_sbt, pr;
  969         struct callout_cpu *cc;
  970         int cancelled, direct;
  971         int ignore_cpu=0;
  972 
  973         cancelled = 0;
  974         if (cpu == -1) {
  975                 ignore_cpu = 1;
  976         } else if ((cpu >= MAXCPU) ||
  977                    ((CC_CPU(cpu))->cc_inited == 0)) {
  978                 /* Invalid CPU spec */
  979                 panic("Invalid CPU in callout %d", cpu);
  980         }
  981         if (flags & C_ABSOLUTE) {
  982                 to_sbt = sbt;
  983         } else {
  984                 if ((flags & C_HARDCLOCK) && (sbt < tick_sbt))
  985                         sbt = tick_sbt;
  986                 if ((flags & C_HARDCLOCK) ||
  987 #ifdef NO_EVENTTIMERS
  988                     sbt >= sbt_timethreshold) {
  989                         to_sbt = getsbinuptime();
  990 
  991                         /* Add safety belt for the case of hz > 1000. */
  992                         to_sbt += tc_tick_sbt - tick_sbt;
  993 #else
  994                     sbt >= sbt_tickthreshold) {
  995                         /*
  996                          * Obtain the time of the last hardclock() call on
  997                          * this CPU directly from the kern_clocksource.c.
  998                          * This value is per-CPU, but it is equal for all
  999                          * active ones.
 1000                          */
 1001 #ifdef __LP64__
 1002                         to_sbt = DPCPU_GET(hardclocktime);
 1003 #else
 1004                         spinlock_enter();
 1005                         to_sbt = DPCPU_GET(hardclocktime);
 1006                         spinlock_exit();
 1007 #endif
 1008 #endif
 1009                         if ((flags & C_HARDCLOCK) == 0)
 1010                                 to_sbt += tick_sbt;
 1011                 } else
 1012                         to_sbt = sbinuptime();
 1013                 if (SBT_MAX - to_sbt < sbt)
 1014                         to_sbt = SBT_MAX;
 1015                 else
 1016                         to_sbt += sbt;
 1017                 pr = ((C_PRELGET(flags) < 0) ? sbt >> tc_precexp :
 1018                     sbt >> C_PRELGET(flags));
 1019                 if (pr > precision)
 1020                         precision = pr;
 1021         }
 1022         /* 
 1023          * This flag used to be added by callout_cc_add, but the
 1024          * first time you call this we could end up with the
 1025          * wrong direct flag if we don't do it before we add.
 1026          */
 1027         if (flags & C_DIRECT_EXEC) {
 1028                 direct = 1;
 1029         } else {
 1030                 direct = 0;
 1031         }
 1032         KASSERT(!direct || c->c_lock == NULL,
 1033             ("%s: direct callout %p has lock", __func__, c));
 1034         cc = callout_lock(c);
 1035         /*
 1036          * Don't allow migration of pre-allocated callouts lest they
 1037          * become unbalanced or handle the case where the user does
 1038          * not care. 
 1039          */
 1040         if ((c->c_iflags & CALLOUT_LOCAL_ALLOC) ||
 1041             ignore_cpu) {
 1042                 cpu = c->c_cpu;
 1043         }
 1044 
 1045         if (cc_exec_curr(cc, direct) == c) {
 1046                 /*
 1047                  * We're being asked to reschedule a callout which is
 1048                  * currently in progress.  If there is a lock then we
 1049                  * can cancel the callout if it has not really started.
 1050                  */
 1051                 if (c->c_lock != NULL && !cc_exec_cancel(cc, direct))
 1052                         cancelled = cc_exec_cancel(cc, direct) = true;
 1053                 if (cc_exec_waiting(cc, direct)) {
 1054                         /*
 1055                          * Someone has called callout_drain to kill this
 1056                          * callout.  Don't reschedule.
 1057                          */
 1058                         CTR4(KTR_CALLOUT, "%s %p func %p arg %p",
 1059                             cancelled ? "cancelled" : "failed to cancel",
 1060                             c, c->c_func, c->c_arg);
 1061                         CC_UNLOCK(cc);
 1062                         return (cancelled);
 1063                 }
 1064 #ifdef SMP
 1065                 if (callout_migrating(c)) {
 1066                         /* 
 1067                          * This only occurs when a second callout_reset_sbt_on
 1068                          * is made after a previous one moved it into
 1069                          * deferred migration (below). Note we do *not* change
 1070                          * the prev_cpu even though the previous target may
 1071                          * be different.
 1072                          */
 1073                         cc_migration_cpu(cc, direct) = cpu;
 1074                         cc_migration_time(cc, direct) = to_sbt;
 1075                         cc_migration_prec(cc, direct) = precision;
 1076                         cc_migration_func(cc, direct) = ftn;
 1077                         cc_migration_arg(cc, direct) = arg;
 1078                         cancelled = 1;
 1079                         CC_UNLOCK(cc);
 1080                         return (cancelled);
 1081                 }
 1082 #endif
 1083         }
 1084         if (c->c_iflags & CALLOUT_PENDING) {
 1085                 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
 1086                         if (cc_exec_next(cc) == c)
 1087                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1088                         LIST_REMOVE(c, c_links.le);
 1089                 } else {
 1090                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1091                 }
 1092                 cancelled = 1;
 1093                 c->c_iflags &= ~ CALLOUT_PENDING;
 1094                 c->c_flags &= ~ CALLOUT_ACTIVE;
 1095         }
 1096 
 1097 #ifdef SMP
 1098         /*
 1099          * If the callout must migrate try to perform it immediately.
 1100          * If the callout is currently running, just defer the migration
 1101          * to a more appropriate moment.
 1102          */
 1103         if (c->c_cpu != cpu) {
 1104                 if (cc_exec_curr(cc, direct) == c) {
 1105                         /* 
 1106                          * Pending will have been removed since we are
 1107                          * actually executing the callout on another
 1108                          * CPU. That callout should be waiting on the
 1109                          * lock the caller holds. If we set both
 1110                          * active/and/pending after we return and the
 1111                          * lock on the executing callout proceeds, it
 1112                          * will then see pending is true and return.
 1113                          * At the return from the actual callout execution
 1114                          * the migration will occur in softclock_call_cc
 1115                          * and this new callout will be placed on the 
 1116                          * new CPU via a call to callout_cpu_switch() which
 1117                          * will get the lock on the right CPU followed
 1118                          * by a call callout_cc_add() which will add it there.
 1119                          * (see above in softclock_call_cc()).
 1120                          */
 1121                         cc_migration_cpu(cc, direct) = cpu;
 1122                         cc_migration_time(cc, direct) = to_sbt;
 1123                         cc_migration_prec(cc, direct) = precision;
 1124                         cc_migration_func(cc, direct) = ftn;
 1125                         cc_migration_arg(cc, direct) = arg;
 1126                         c->c_iflags |= (CALLOUT_DFRMIGRATION | CALLOUT_PENDING);
 1127                         c->c_flags |= CALLOUT_ACTIVE;
 1128                         CTR6(KTR_CALLOUT,
 1129                     "migration of %p func %p arg %p in %d.%08x to %u deferred",
 1130                             c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1131                             (u_int)(to_sbt & 0xffffffff), cpu);
 1132                         CC_UNLOCK(cc);
 1133                         return (cancelled);
 1134                 }
 1135                 cc = callout_cpu_switch(c, cc, cpu);
 1136         }
 1137 #endif
 1138 
 1139         callout_cc_add(c, cc, to_sbt, precision, ftn, arg, cpu, flags);
 1140         CTR6(KTR_CALLOUT, "%sscheduled %p func %p arg %p in %d.%08x",
 1141             cancelled ? "re" : "", c, c->c_func, c->c_arg, (int)(to_sbt >> 32),
 1142             (u_int)(to_sbt & 0xffffffff));
 1143         CC_UNLOCK(cc);
 1144 
 1145         return (cancelled);
 1146 }
 1147 
 1148 /*
 1149  * Common idioms that can be optimized in the future.
 1150  */
 1151 int
 1152 callout_schedule_on(struct callout *c, int to_ticks, int cpu)
 1153 {
 1154         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, cpu);
 1155 }
 1156 
 1157 int
 1158 callout_schedule(struct callout *c, int to_ticks)
 1159 {
 1160         return callout_reset_on(c, to_ticks, c->c_func, c->c_arg, c->c_cpu);
 1161 }
 1162 
 1163 int
 1164 _callout_stop_safe(struct callout *c, int flags, void (*drain)(void *))
 1165 {
 1166         struct callout_cpu *cc, *old_cc;
 1167         struct lock_class *class;
 1168         int direct, sq_locked, use_lock;
 1169         int cancelled, not_on_a_list;
 1170 
 1171         if ((flags & CS_DRAIN) != 0)
 1172                 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, c->c_lock,
 1173                     "calling %s", __func__);
 1174 
 1175         /*
 1176          * Some old subsystems don't hold Giant while running a callout_stop(),
 1177          * so just discard this check for the moment.
 1178          */
 1179         if ((flags & CS_DRAIN) == 0 && c->c_lock != NULL) {
 1180                 if (c->c_lock == &Giant.lock_object)
 1181                         use_lock = mtx_owned(&Giant);
 1182                 else {
 1183                         use_lock = 1;
 1184                         class = LOCK_CLASS(c->c_lock);
 1185                         class->lc_assert(c->c_lock, LA_XLOCKED);
 1186                 }
 1187         } else
 1188                 use_lock = 0;
 1189         if (c->c_iflags & CALLOUT_DIRECT) {
 1190                 direct = 1;
 1191         } else {
 1192                 direct = 0;
 1193         }
 1194         sq_locked = 0;
 1195         old_cc = NULL;
 1196 again:
 1197         cc = callout_lock(c);
 1198 
 1199         if ((c->c_iflags & (CALLOUT_DFRMIGRATION | CALLOUT_PENDING)) ==
 1200             (CALLOUT_DFRMIGRATION | CALLOUT_PENDING) &&
 1201             ((c->c_flags & CALLOUT_ACTIVE) == CALLOUT_ACTIVE)) {
 1202                 /*
 1203                  * Special case where this slipped in while we
 1204                  * were migrating *as* the callout is about to
 1205                  * execute. The caller probably holds the lock
 1206                  * the callout wants.
 1207                  *
 1208                  * Get rid of the migration first. Then set
 1209                  * the flag that tells this code *not* to
 1210                  * try to remove it from any lists (its not
 1211                  * on one yet). When the callout wheel runs,
 1212                  * it will ignore this callout.
 1213                  */
 1214                 c->c_iflags &= ~CALLOUT_PENDING;
 1215                 c->c_flags &= ~CALLOUT_ACTIVE;
 1216                 not_on_a_list = 1;
 1217         } else {
 1218                 not_on_a_list = 0;
 1219         }
 1220 
 1221         /*
 1222          * If the callout was migrating while the callout cpu lock was
 1223          * dropped,  just drop the sleepqueue lock and check the states
 1224          * again.
 1225          */
 1226         if (sq_locked != 0 && cc != old_cc) {
 1227 #ifdef SMP
 1228                 CC_UNLOCK(cc);
 1229                 sleepq_release(&cc_exec_waiting(old_cc, direct));
 1230                 sq_locked = 0;
 1231                 old_cc = NULL;
 1232                 goto again;
 1233 #else
 1234                 panic("migration should not happen");
 1235 #endif
 1236         }
 1237 
 1238         /*
 1239          * If the callout is running, try to stop it or drain it.
 1240          */
 1241         if (cc_exec_curr(cc, direct) == c) {
 1242                 /*
 1243                  * Succeed we to stop it or not, we must clear the
 1244                  * active flag - this is what API users expect.
 1245                  */
 1246                 c->c_flags &= ~CALLOUT_ACTIVE;
 1247 
 1248                 if ((flags & CS_DRAIN) != 0) {
 1249                         /*
 1250                          * The current callout is running (or just
 1251                          * about to run) and blocking is allowed, so
 1252                          * just wait for the current invocation to
 1253                          * finish.
 1254                          */
 1255                         while (cc_exec_curr(cc, direct) == c) {
 1256                                 /*
 1257                                  * Use direct calls to sleepqueue interface
 1258                                  * instead of cv/msleep in order to avoid
 1259                                  * a LOR between cc_lock and sleepqueue
 1260                                  * chain spinlocks.  This piece of code
 1261                                  * emulates a msleep_spin() call actually.
 1262                                  *
 1263                                  * If we already have the sleepqueue chain
 1264                                  * locked, then we can safely block.  If we
 1265                                  * don't already have it locked, however,
 1266                                  * we have to drop the cc_lock to lock
 1267                                  * it.  This opens several races, so we
 1268                                  * restart at the beginning once we have
 1269                                  * both locks.  If nothing has changed, then
 1270                                  * we will end up back here with sq_locked
 1271                                  * set.
 1272                                  */
 1273                                 if (!sq_locked) {
 1274                                         CC_UNLOCK(cc);
 1275                                         sleepq_lock(
 1276                                             &cc_exec_waiting(cc, direct));
 1277                                         sq_locked = 1;
 1278                                         old_cc = cc;
 1279                                         goto again;
 1280                                 }
 1281 
 1282                                 /*
 1283                                  * Migration could be cancelled here, but
 1284                                  * as long as it is still not sure when it
 1285                                  * will be packed up, just let softclock()
 1286                                  * take care of it.
 1287                                  */
 1288                                 cc_exec_waiting(cc, direct) = true;
 1289                                 DROP_GIANT();
 1290                                 CC_UNLOCK(cc);
 1291                                 sleepq_add(
 1292                                     &cc_exec_waiting(cc, direct),
 1293                                     &cc->cc_lock.lock_object, "codrain",
 1294                                     SLEEPQ_SLEEP, 0);
 1295                                 sleepq_wait(
 1296                                     &cc_exec_waiting(cc, direct),
 1297                                              0);
 1298                                 sq_locked = 0;
 1299                                 old_cc = NULL;
 1300 
 1301                                 /* Reacquire locks previously released. */
 1302                                 PICKUP_GIANT();
 1303                                 CC_LOCK(cc);
 1304                         }
 1305                 } else if (use_lock &&
 1306                            !cc_exec_cancel(cc, direct) && (drain == NULL)) {
 1307                         
 1308                         /*
 1309                          * The current callout is waiting for its
 1310                          * lock which we hold.  Cancel the callout
 1311                          * and return.  After our caller drops the
 1312                          * lock, the callout will be skipped in
 1313                          * softclock(). This *only* works with a
 1314                          * callout_stop() *not* callout_drain() or
 1315                          * callout_async_drain().
 1316                          */
 1317                         cc_exec_cancel(cc, direct) = true;
 1318                         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1319                             c, c->c_func, c->c_arg);
 1320                         KASSERT(!cc_cce_migrating(cc, direct),
 1321                             ("callout wrongly scheduled for migration"));
 1322                         if (callout_migrating(c)) {
 1323                                 c->c_iflags &= ~CALLOUT_DFRMIGRATION;
 1324 #ifdef SMP
 1325                                 cc_migration_cpu(cc, direct) = CPUBLOCK;
 1326                                 cc_migration_time(cc, direct) = 0;
 1327                                 cc_migration_prec(cc, direct) = 0;
 1328                                 cc_migration_func(cc, direct) = NULL;
 1329                                 cc_migration_arg(cc, direct) = NULL;
 1330 #endif
 1331                         }
 1332                         CC_UNLOCK(cc);
 1333                         KASSERT(!sq_locked, ("sleepqueue chain locked"));
 1334                         return (1);
 1335                 } else if (callout_migrating(c)) {
 1336                         /*
 1337                          * The callout is currently being serviced
 1338                          * and the "next" callout is scheduled at
 1339                          * its completion with a migration. We remove
 1340                          * the migration flag so it *won't* get rescheduled,
 1341                          * but we can't stop the one thats running so
 1342                          * we return 0.
 1343                          */
 1344                         c->c_iflags &= ~CALLOUT_DFRMIGRATION;
 1345 #ifdef SMP
 1346                         /* 
 1347                          * We can't call cc_cce_cleanup here since
 1348                          * if we do it will remove .ce_curr and
 1349                          * its still running. This will prevent a
 1350                          * reschedule of the callout when the 
 1351                          * execution completes.
 1352                          */
 1353                         cc_migration_cpu(cc, direct) = CPUBLOCK;
 1354                         cc_migration_time(cc, direct) = 0;
 1355                         cc_migration_prec(cc, direct) = 0;
 1356                         cc_migration_func(cc, direct) = NULL;
 1357                         cc_migration_arg(cc, direct) = NULL;
 1358 #endif
 1359                         CTR3(KTR_CALLOUT, "postponing stop %p func %p arg %p",
 1360                             c, c->c_func, c->c_arg);
 1361                         if (drain) {
 1362                                 cc_exec_drain(cc, direct) = drain;
 1363                         }
 1364                         CC_UNLOCK(cc);
 1365                         return ((flags & CS_EXECUTING) != 0);
 1366                 }
 1367                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1368                     c, c->c_func, c->c_arg);
 1369                 if (drain) {
 1370                         cc_exec_drain(cc, direct) = drain;
 1371                 }
 1372                 KASSERT(!sq_locked, ("sleepqueue chain still locked"));
 1373                 cancelled = ((flags & CS_EXECUTING) != 0);
 1374         } else
 1375                 cancelled = 1;
 1376 
 1377         if (sq_locked)
 1378                 sleepq_release(&cc_exec_waiting(cc, direct));
 1379 
 1380         if ((c->c_iflags & CALLOUT_PENDING) == 0) {
 1381                 CTR3(KTR_CALLOUT, "failed to stop %p func %p arg %p",
 1382                     c, c->c_func, c->c_arg);
 1383                 CC_UNLOCK(cc);
 1384                 return (cancelled);
 1385         }
 1386 
 1387         c->c_iflags &= ~CALLOUT_PENDING;
 1388         c->c_flags &= ~CALLOUT_ACTIVE;
 1389 
 1390         CTR3(KTR_CALLOUT, "cancelled %p func %p arg %p",
 1391             c, c->c_func, c->c_arg);
 1392         if (not_on_a_list == 0) {
 1393                 if ((c->c_iflags & CALLOUT_PROCESSED) == 0) {
 1394                         if (cc_exec_next(cc) == c)
 1395                                 cc_exec_next(cc) = LIST_NEXT(c, c_links.le);
 1396                         LIST_REMOVE(c, c_links.le);
 1397                 } else {
 1398                         TAILQ_REMOVE(&cc->cc_expireq, c, c_links.tqe);
 1399                 }
 1400         }
 1401         callout_cc_del(c, cc);
 1402         CC_UNLOCK(cc);
 1403         return (cancelled);
 1404 }
 1405 
 1406 void
 1407 callout_init(struct callout *c, int mpsafe)
 1408 {
 1409         bzero(c, sizeof *c);
 1410         if (mpsafe) {
 1411                 c->c_lock = NULL;
 1412                 c->c_iflags = CALLOUT_RETURNUNLOCKED;
 1413         } else {
 1414                 c->c_lock = &Giant.lock_object;
 1415                 c->c_iflags = 0;
 1416         }
 1417         c->c_cpu = timeout_cpu;
 1418 }
 1419 
 1420 void
 1421 _callout_init_lock(struct callout *c, struct lock_object *lock, int flags)
 1422 {
 1423         bzero(c, sizeof *c);
 1424         c->c_lock = lock;
 1425         KASSERT((flags & ~(CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK)) == 0,
 1426             ("callout_init_lock: bad flags %d", flags));
 1427         KASSERT(lock != NULL || (flags & CALLOUT_RETURNUNLOCKED) == 0,
 1428             ("callout_init_lock: CALLOUT_RETURNUNLOCKED with no lock"));
 1429         KASSERT(lock == NULL || !(LOCK_CLASS(lock)->lc_flags &
 1430             (LC_SPINLOCK | LC_SLEEPABLE)), ("%s: invalid lock class",
 1431             __func__));
 1432         c->c_iflags = flags & (CALLOUT_RETURNUNLOCKED | CALLOUT_SHAREDLOCK);
 1433         c->c_cpu = timeout_cpu;
 1434 }
 1435 
 1436 #ifdef APM_FIXUP_CALLTODO
 1437 /* 
 1438  * Adjust the kernel calltodo timeout list.  This routine is used after 
 1439  * an APM resume to recalculate the calltodo timer list values with the 
 1440  * number of hz's we have been sleeping.  The next hardclock() will detect 
 1441  * that there are fired timers and run softclock() to execute them.
 1442  *
 1443  * Please note, I have not done an exhaustive analysis of what code this
 1444  * might break.  I am motivated to have my select()'s and alarm()'s that
 1445  * have expired during suspend firing upon resume so that the applications
 1446  * which set the timer can do the maintanence the timer was for as close
 1447  * as possible to the originally intended time.  Testing this code for a 
 1448  * week showed that resuming from a suspend resulted in 22 to 25 timers 
 1449  * firing, which seemed independent on whether the suspend was 2 hours or
 1450  * 2 days.  Your milage may vary.   - Ken Key <key@cs.utk.edu>
 1451  */
 1452 void
 1453 adjust_timeout_calltodo(struct timeval *time_change)
 1454 {
 1455         register struct callout *p;
 1456         unsigned long delta_ticks;
 1457 
 1458         /* 
 1459          * How many ticks were we asleep?
 1460          * (stolen from tvtohz()).
 1461          */
 1462 
 1463         /* Don't do anything */
 1464         if (time_change->tv_sec < 0)
 1465                 return;
 1466         else if (time_change->tv_sec <= LONG_MAX / 1000000)
 1467                 delta_ticks = howmany(time_change->tv_sec * 1000000 +
 1468                     time_change->tv_usec, tick) + 1;
 1469         else if (time_change->tv_sec <= LONG_MAX / hz)
 1470                 delta_ticks = time_change->tv_sec * hz +
 1471                     howmany(time_change->tv_usec, tick) + 1;
 1472         else
 1473                 delta_ticks = LONG_MAX;
 1474 
 1475         if (delta_ticks > INT_MAX)
 1476                 delta_ticks = INT_MAX;
 1477 
 1478         /* 
 1479          * Now rip through the timer calltodo list looking for timers
 1480          * to expire.
 1481          */
 1482 
 1483         /* don't collide with softclock() */
 1484         CC_LOCK(cc);
 1485         for (p = calltodo.c_next; p != NULL; p = p->c_next) {
 1486                 p->c_time -= delta_ticks;
 1487 
 1488                 /* Break if the timer had more time on it than delta_ticks */
 1489                 if (p->c_time > 0)
 1490                         break;
 1491 
 1492                 /* take back the ticks the timer didn't use (p->c_time <= 0) */
 1493                 delta_ticks = -p->c_time;
 1494         }
 1495         CC_UNLOCK(cc);
 1496 
 1497         return;
 1498 }
 1499 #endif /* APM_FIXUP_CALLTODO */
 1500 
 1501 static int
 1502 flssbt(sbintime_t sbt)
 1503 {
 1504 
 1505         sbt += (uint64_t)sbt >> 1;
 1506         if (sizeof(long) >= sizeof(sbintime_t))
 1507                 return (flsl(sbt));
 1508         if (sbt >= SBT_1S)
 1509                 return (flsl(((uint64_t)sbt) >> 32) + 32);
 1510         return (flsl(sbt));
 1511 }
 1512 
 1513 /*
 1514  * Dump immediate statistic snapshot of the scheduled callouts.
 1515  */
 1516 static int
 1517 sysctl_kern_callout_stat(SYSCTL_HANDLER_ARGS)
 1518 {
 1519         struct callout *tmp;
 1520         struct callout_cpu *cc;
 1521         struct callout_list *sc;
 1522         sbintime_t maxpr, maxt, medpr, medt, now, spr, st, t;
 1523         int ct[64], cpr[64], ccpbk[32];
 1524         int error, val, i, count, tcum, pcum, maxc, c, medc;
 1525 #ifdef SMP
 1526         int cpu;
 1527 #endif
 1528 
 1529         val = 0;
 1530         error = sysctl_handle_int(oidp, &val, 0, req);
 1531         if (error != 0 || req->newptr == NULL)
 1532                 return (error);
 1533         count = maxc = 0;
 1534         st = spr = maxt = maxpr = 0;
 1535         bzero(ccpbk, sizeof(ccpbk));
 1536         bzero(ct, sizeof(ct));
 1537         bzero(cpr, sizeof(cpr));
 1538         now = sbinuptime();
 1539 #ifdef SMP
 1540         CPU_FOREACH(cpu) {
 1541                 cc = CC_CPU(cpu);
 1542 #else
 1543                 cc = CC_CPU(timeout_cpu);
 1544 #endif
 1545                 CC_LOCK(cc);
 1546                 for (i = 0; i < callwheelsize; i++) {
 1547                         sc = &cc->cc_callwheel[i];
 1548                         c = 0;
 1549                         LIST_FOREACH(tmp, sc, c_links.le) {
 1550                                 c++;
 1551                                 t = tmp->c_time - now;
 1552                                 if (t < 0)
 1553                                         t = 0;
 1554                                 st += t / SBT_1US;
 1555                                 spr += tmp->c_precision / SBT_1US;
 1556                                 if (t > maxt)
 1557                                         maxt = t;
 1558                                 if (tmp->c_precision > maxpr)
 1559                                         maxpr = tmp->c_precision;
 1560                                 ct[flssbt(t)]++;
 1561                                 cpr[flssbt(tmp->c_precision)]++;
 1562                         }
 1563                         if (c > maxc)
 1564                                 maxc = c;
 1565                         ccpbk[fls(c + c / 2)]++;
 1566                         count += c;
 1567                 }
 1568                 CC_UNLOCK(cc);
 1569 #ifdef SMP
 1570         }
 1571 #endif
 1572 
 1573         for (i = 0, tcum = 0; i < 64 && tcum < count / 2; i++)
 1574                 tcum += ct[i];
 1575         medt = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1576         for (i = 0, pcum = 0; i < 64 && pcum < count / 2; i++)
 1577                 pcum += cpr[i];
 1578         medpr = (i >= 2) ? (((sbintime_t)1) << (i - 2)) : 0;
 1579         for (i = 0, c = 0; i < 32 && c < count / 2; i++)
 1580                 c += ccpbk[i];
 1581         medc = (i >= 2) ? (1 << (i - 2)) : 0;
 1582 
 1583         printf("Scheduled callouts statistic snapshot:\n");
 1584         printf("  Callouts: %6d  Buckets: %6d*%-3d  Bucket size: 0.%06ds\n",
 1585             count, callwheelsize, mp_ncpus, 1000000 >> CC_HASH_SHIFT);
 1586         printf("  C/Bk: med %5d         avg %6d.%06jd  max %6d\n",
 1587             medc,
 1588             count / callwheelsize / mp_ncpus,
 1589             (uint64_t)count * 1000000 / callwheelsize / mp_ncpus % 1000000,
 1590             maxc);
 1591         printf("  Time: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1592             medt / SBT_1S, (medt & 0xffffffff) * 1000000 >> 32,
 1593             (st / count) / 1000000, (st / count) % 1000000,
 1594             maxt / SBT_1S, (maxt & 0xffffffff) * 1000000 >> 32);
 1595         printf("  Prec: med %5jd.%06jds avg %6jd.%06jds max %6jd.%06jds\n",
 1596             medpr / SBT_1S, (medpr & 0xffffffff) * 1000000 >> 32,
 1597             (spr / count) / 1000000, (spr / count) % 1000000,
 1598             maxpr / SBT_1S, (maxpr & 0xffffffff) * 1000000 >> 32);
 1599         printf("  Distribution:       \tbuckets\t   time\t   tcum\t"
 1600             "   prec\t   pcum\n");
 1601         for (i = 0, tcum = pcum = 0; i < 64; i++) {
 1602                 if (ct[i] == 0 && cpr[i] == 0)
 1603                         continue;
 1604                 t = (i != 0) ? (((sbintime_t)1) << (i - 1)) : 0;
 1605                 tcum += ct[i];
 1606                 pcum += cpr[i];
 1607                 printf("  %10jd.%06jds\t 2**%d\t%7d\t%7d\t%7d\t%7d\n",
 1608                     t / SBT_1S, (t & 0xffffffff) * 1000000 >> 32,
 1609                     i - 1 - (32 - CC_HASH_SHIFT),
 1610                     ct[i], tcum, cpr[i], pcum);
 1611         }
 1612         return (error);
 1613 }
 1614 SYSCTL_PROC(_kern, OID_AUTO, callout_stat,
 1615     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 1616     0, 0, sysctl_kern_callout_stat, "I",
 1617     "Dump immediate statistic snapshot of the scheduled callouts");
 1618 
 1619 #ifdef DDB
 1620 static void
 1621 _show_callout(struct callout *c)
 1622 {
 1623 
 1624         db_printf("callout %p\n", c);
 1625 #define C_DB_PRINTF(f, e)       db_printf("   %s = " f "\n", #e, c->e);
 1626         db_printf("   &c_links = %p\n", &(c->c_links));
 1627         C_DB_PRINTF("%" PRId64, c_time);
 1628         C_DB_PRINTF("%" PRId64, c_precision);
 1629         C_DB_PRINTF("%p",       c_arg);
 1630         C_DB_PRINTF("%p",       c_func);
 1631         C_DB_PRINTF("%p",       c_lock);
 1632         C_DB_PRINTF("%#x",      c_flags);
 1633         C_DB_PRINTF("%#x",      c_iflags);
 1634         C_DB_PRINTF("%d",       c_cpu);
 1635 #undef  C_DB_PRINTF
 1636 }
 1637 
 1638 DB_SHOW_COMMAND(callout, db_show_callout)
 1639 {
 1640 
 1641         if (!have_addr) {
 1642                 db_printf("usage: show callout <struct callout *>\n");
 1643                 return;
 1644         }
 1645 
 1646         _show_callout((struct callout *)addr);
 1647 }
 1648 #endif /* DDB */

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