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

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    1 /*-
    2  * SPDX-License-Identifier: Beerware
    3  *
    4  * ----------------------------------------------------------------------------
    5  * "THE BEER-WARE LICENSE" (Revision 42):
    6  * <phk@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
    7  * can do whatever you want with this stuff. If we meet some day, and you think
    8  * this stuff is worth it, you can buy me a beer in return.   Poul-Henning Kamp
    9  * ----------------------------------------------------------------------------
   10  *
   11  * Copyright (c) 2011, 2015, 2016 The FreeBSD Foundation
   12  *
   13  * Portions of this software were developed by Julien Ridoux at the University
   14  * of Melbourne under sponsorship from the FreeBSD Foundation.
   15  *
   16  * Portions of this software were developed by Konstantin Belousov
   17  * under sponsorship from the FreeBSD Foundation.
   18  */
   19 
   20 #include <sys/cdefs.h>
   21 __FBSDID("$FreeBSD$");
   22 
   23 #include "opt_ntp.h"
   24 #include "opt_ffclock.h"
   25 
   26 #include <sys/param.h>
   27 #include <sys/kernel.h>
   28 #include <sys/limits.h>
   29 #include <sys/lock.h>
   30 #include <sys/mutex.h>
   31 #include <sys/proc.h>
   32 #include <sys/sbuf.h>
   33 #include <sys/sleepqueue.h>
   34 #include <sys/sysctl.h>
   35 #include <sys/syslog.h>
   36 #include <sys/systm.h>
   37 #include <sys/timeffc.h>
   38 #include <sys/timepps.h>
   39 #include <sys/timetc.h>
   40 #include <sys/timex.h>
   41 #include <sys/vdso.h>
   42 
   43 /*
   44  * A large step happens on boot.  This constant detects such steps.
   45  * It is relatively small so that ntp_update_second gets called enough
   46  * in the typical 'missed a couple of seconds' case, but doesn't loop
   47  * forever when the time step is large.
   48  */
   49 #define LARGE_STEP      200
   50 
   51 /*
   52  * Implement a dummy timecounter which we can use until we get a real one
   53  * in the air.  This allows the console and other early stuff to use
   54  * time services.
   55  */
   56 
   57 static u_int
   58 dummy_get_timecount(struct timecounter *tc)
   59 {
   60         static u_int now;
   61 
   62         return (++now);
   63 }
   64 
   65 static struct timecounter dummy_timecounter = {
   66         dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000
   67 };
   68 
   69 struct timehands {
   70         /* These fields must be initialized by the driver. */
   71         struct timecounter      *th_counter;
   72         int64_t                 th_adjustment;
   73         uint64_t                th_scale;
   74         u_int                   th_large_delta;
   75         u_int                   th_offset_count;
   76         struct bintime          th_offset;
   77         struct bintime          th_bintime;
   78         struct timeval          th_microtime;
   79         struct timespec         th_nanotime;
   80         struct bintime          th_boottime;
   81         /* Fields not to be copied in tc_windup start with th_generation. */
   82         u_int                   th_generation;
   83         struct timehands        *th_next;
   84 };
   85 
   86 static struct timehands ths[16] = {
   87     [0] =  {
   88         .th_counter = &dummy_timecounter,
   89         .th_scale = (uint64_t)-1 / 1000000,
   90         .th_large_delta = 1000000,
   91         .th_offset = { .sec = 1 },
   92         .th_generation = 1,
   93     },
   94 };
   95 
   96 static struct timehands *volatile timehands = &ths[0];
   97 struct timecounter *timecounter = &dummy_timecounter;
   98 static struct timecounter *timecounters = &dummy_timecounter;
   99 
  100 /* Mutex to protect the timecounter list. */
  101 static struct mtx tc_lock;
  102 
  103 int tc_min_ticktock_freq = 1;
  104 
  105 volatile time_t time_second = 1;
  106 volatile time_t time_uptime = 1;
  107 
  108 /*
  109  * The system time is always computed by summing the estimated boot time and the
  110  * system uptime. The timehands track boot time, but it changes when the system
  111  * time is set by the user, stepped by ntpd or adjusted when resuming. It
  112  * is set to new_time - uptime.
  113  */
  114 static int sysctl_kern_boottime(SYSCTL_HANDLER_ARGS);
  115 SYSCTL_PROC(_kern, KERN_BOOTTIME, boottime,
  116     CTLTYPE_STRUCT | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0,
  117     sysctl_kern_boottime, "S,timeval",
  118     "Estimated system boottime");
  119 
  120 SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
  121     "");
  122 static SYSCTL_NODE(_kern_timecounter, OID_AUTO, tc,
  123     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
  124     "");
  125 
  126 static int timestepwarnings;
  127 SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RWTUN,
  128     &timestepwarnings, 0, "Log time steps");
  129 
  130 static int timehands_count = 2;
  131 SYSCTL_INT(_kern_timecounter, OID_AUTO, timehands_count,
  132     CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
  133     &timehands_count, 0, "Count of timehands in rotation");
  134 
  135 struct bintime bt_timethreshold;
  136 struct bintime bt_tickthreshold;
  137 sbintime_t sbt_timethreshold;
  138 sbintime_t sbt_tickthreshold;
  139 struct bintime tc_tick_bt;
  140 sbintime_t tc_tick_sbt;
  141 int tc_precexp;
  142 int tc_timepercentage = TC_DEFAULTPERC;
  143 static int sysctl_kern_timecounter_adjprecision(SYSCTL_HANDLER_ARGS);
  144 SYSCTL_PROC(_kern_timecounter, OID_AUTO, alloweddeviation,
  145     CTLTYPE_INT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE, 0, 0,
  146     sysctl_kern_timecounter_adjprecision, "I",
  147     "Allowed time interval deviation in percents");
  148 
  149 volatile int rtc_generation = 1;
  150 
  151 static int tc_chosen;   /* Non-zero if a specific tc was chosen via sysctl. */
  152 static char tc_from_tunable[16];
  153 
  154 static void tc_windup(struct bintime *new_boottimebin);
  155 static void cpu_tick_calibrate(int);
  156 
  157 void dtrace_getnanotime(struct timespec *tsp);
  158 void dtrace_getnanouptime(struct timespec *tsp);
  159 
  160 static int
  161 sysctl_kern_boottime(SYSCTL_HANDLER_ARGS)
  162 {
  163         struct timeval boottime;
  164 
  165         getboottime(&boottime);
  166 
  167 /* i386 is the only arch which uses a 32bits time_t */
  168 #ifdef __amd64__
  169 #ifdef SCTL_MASK32
  170         int tv[2];
  171 
  172         if (req->flags & SCTL_MASK32) {
  173                 tv[0] = boottime.tv_sec;
  174                 tv[1] = boottime.tv_usec;
  175                 return (SYSCTL_OUT(req, tv, sizeof(tv)));
  176         }
  177 #endif
  178 #endif
  179         return (SYSCTL_OUT(req, &boottime, sizeof(boottime)));
  180 }
  181 
  182 static int
  183 sysctl_kern_timecounter_get(SYSCTL_HANDLER_ARGS)
  184 {
  185         u_int ncount;
  186         struct timecounter *tc = arg1;
  187 
  188         ncount = tc->tc_get_timecount(tc);
  189         return (sysctl_handle_int(oidp, &ncount, 0, req));
  190 }
  191 
  192 static int
  193 sysctl_kern_timecounter_freq(SYSCTL_HANDLER_ARGS)
  194 {
  195         uint64_t freq;
  196         struct timecounter *tc = arg1;
  197 
  198         freq = tc->tc_frequency;
  199         return (sysctl_handle_64(oidp, &freq, 0, req));
  200 }
  201 
  202 /*
  203  * Return the difference between the timehands' counter value now and what
  204  * was when we copied it to the timehands' offset_count.
  205  */
  206 static __inline u_int
  207 tc_delta(struct timehands *th)
  208 {
  209         struct timecounter *tc;
  210 
  211         tc = th->th_counter;
  212         return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
  213             tc->tc_counter_mask);
  214 }
  215 
  216 static __inline void
  217 bintime_add_tc_delta(struct bintime *bt, uint64_t scale,
  218     uint64_t large_delta, uint64_t delta)
  219 {
  220         uint64_t x;
  221 
  222         if (__predict_false(delta >= large_delta)) {
  223                 /* Avoid overflow for scale * delta. */
  224                 x = (scale >> 32) * delta;
  225                 bt->sec += x >> 32;
  226                 bintime_addx(bt, x << 32);
  227                 bintime_addx(bt, (scale & 0xffffffff) * delta);
  228         } else {
  229                 bintime_addx(bt, scale * delta);
  230         }
  231 }
  232 
  233 /*
  234  * Functions for reading the time.  We have to loop until we are sure that
  235  * the timehands that we operated on was not updated under our feet.  See
  236  * the comment in <sys/time.h> for a description of these 12 functions.
  237  */
  238 
  239 static __inline void
  240 bintime_off(struct bintime *bt, u_int off)
  241 {
  242         struct timehands *th;
  243         struct bintime *btp;
  244         uint64_t scale;
  245         u_int delta, gen, large_delta;
  246 
  247         do {
  248                 th = timehands;
  249                 gen = atomic_load_acq_int(&th->th_generation);
  250                 btp = (struct bintime *)((vm_offset_t)th + off);
  251                 *bt = *btp;
  252                 scale = th->th_scale;
  253                 delta = tc_delta(th);
  254                 large_delta = th->th_large_delta;
  255                 atomic_thread_fence_acq();
  256         } while (gen == 0 || gen != th->th_generation);
  257 
  258         bintime_add_tc_delta(bt, scale, large_delta, delta);
  259 }
  260 #define GETTHBINTIME(dst, member)                                       \
  261 do {                                                                    \
  262         _Static_assert(_Generic(((struct timehands *)NULL)->member,     \
  263             struct bintime: 1, default: 0) == 1,                        \
  264             "struct timehands member is not of struct bintime type");   \
  265         bintime_off(dst, __offsetof(struct timehands, member));         \
  266 } while (0)
  267 
  268 static __inline void
  269 getthmember(void *out, size_t out_size, u_int off)
  270 {
  271         struct timehands *th;
  272         u_int gen;
  273 
  274         do {
  275                 th = timehands;
  276                 gen = atomic_load_acq_int(&th->th_generation);
  277                 memcpy(out, (char *)th + off, out_size);
  278                 atomic_thread_fence_acq();
  279         } while (gen == 0 || gen != th->th_generation);
  280 }
  281 #define GETTHMEMBER(dst, member)                                        \
  282 do {                                                                    \
  283         _Static_assert(_Generic(*dst,                                   \
  284             __typeof(((struct timehands *)NULL)->member): 1,            \
  285             default: 0) == 1,                                           \
  286             "*dst and struct timehands member have different types");   \
  287         getthmember(dst, sizeof(*dst), __offsetof(struct timehands,     \
  288             member));                                                   \
  289 } while (0)
  290 
  291 #ifdef FFCLOCK
  292 void
  293 fbclock_binuptime(struct bintime *bt)
  294 {
  295 
  296         GETTHBINTIME(bt, th_offset);
  297 }
  298 
  299 void
  300 fbclock_nanouptime(struct timespec *tsp)
  301 {
  302         struct bintime bt;
  303 
  304         fbclock_binuptime(&bt);
  305         bintime2timespec(&bt, tsp);
  306 }
  307 
  308 void
  309 fbclock_microuptime(struct timeval *tvp)
  310 {
  311         struct bintime bt;
  312 
  313         fbclock_binuptime(&bt);
  314         bintime2timeval(&bt, tvp);
  315 }
  316 
  317 void
  318 fbclock_bintime(struct bintime *bt)
  319 {
  320 
  321         GETTHBINTIME(bt, th_bintime);
  322 }
  323 
  324 void
  325 fbclock_nanotime(struct timespec *tsp)
  326 {
  327         struct bintime bt;
  328 
  329         fbclock_bintime(&bt);
  330         bintime2timespec(&bt, tsp);
  331 }
  332 
  333 void
  334 fbclock_microtime(struct timeval *tvp)
  335 {
  336         struct bintime bt;
  337 
  338         fbclock_bintime(&bt);
  339         bintime2timeval(&bt, tvp);
  340 }
  341 
  342 void
  343 fbclock_getbinuptime(struct bintime *bt)
  344 {
  345 
  346         GETTHMEMBER(bt, th_offset);
  347 }
  348 
  349 void
  350 fbclock_getnanouptime(struct timespec *tsp)
  351 {
  352         struct bintime bt;
  353 
  354         GETTHMEMBER(&bt, th_offset);
  355         bintime2timespec(&bt, tsp);
  356 }
  357 
  358 void
  359 fbclock_getmicrouptime(struct timeval *tvp)
  360 {
  361         struct bintime bt;
  362 
  363         GETTHMEMBER(&bt, th_offset);
  364         bintime2timeval(&bt, tvp);
  365 }
  366 
  367 void
  368 fbclock_getbintime(struct bintime *bt)
  369 {
  370 
  371         GETTHMEMBER(bt, th_bintime);
  372 }
  373 
  374 void
  375 fbclock_getnanotime(struct timespec *tsp)
  376 {
  377 
  378         GETTHMEMBER(tsp, th_nanotime);
  379 }
  380 
  381 void
  382 fbclock_getmicrotime(struct timeval *tvp)
  383 {
  384 
  385         GETTHMEMBER(tvp, th_microtime);
  386 }
  387 #else /* !FFCLOCK */
  388 
  389 void
  390 binuptime(struct bintime *bt)
  391 {
  392 
  393         GETTHBINTIME(bt, th_offset);
  394 }
  395 
  396 void
  397 nanouptime(struct timespec *tsp)
  398 {
  399         struct bintime bt;
  400 
  401         binuptime(&bt);
  402         bintime2timespec(&bt, tsp);
  403 }
  404 
  405 void
  406 microuptime(struct timeval *tvp)
  407 {
  408         struct bintime bt;
  409 
  410         binuptime(&bt);
  411         bintime2timeval(&bt, tvp);
  412 }
  413 
  414 void
  415 bintime(struct bintime *bt)
  416 {
  417 
  418         GETTHBINTIME(bt, th_bintime);
  419 }
  420 
  421 void
  422 nanotime(struct timespec *tsp)
  423 {
  424         struct bintime bt;
  425 
  426         bintime(&bt);
  427         bintime2timespec(&bt, tsp);
  428 }
  429 
  430 void
  431 microtime(struct timeval *tvp)
  432 {
  433         struct bintime bt;
  434 
  435         bintime(&bt);
  436         bintime2timeval(&bt, tvp);
  437 }
  438 
  439 void
  440 getbinuptime(struct bintime *bt)
  441 {
  442 
  443         GETTHMEMBER(bt, th_offset);
  444 }
  445 
  446 void
  447 getnanouptime(struct timespec *tsp)
  448 {
  449         struct bintime bt;
  450 
  451         GETTHMEMBER(&bt, th_offset);
  452         bintime2timespec(&bt, tsp);
  453 }
  454 
  455 void
  456 getmicrouptime(struct timeval *tvp)
  457 {
  458         struct bintime bt;
  459 
  460         GETTHMEMBER(&bt, th_offset);
  461         bintime2timeval(&bt, tvp);
  462 }
  463 
  464 void
  465 getbintime(struct bintime *bt)
  466 {
  467 
  468         GETTHMEMBER(bt, th_bintime);
  469 }
  470 
  471 void
  472 getnanotime(struct timespec *tsp)
  473 {
  474 
  475         GETTHMEMBER(tsp, th_nanotime);
  476 }
  477 
  478 void
  479 getmicrotime(struct timeval *tvp)
  480 {
  481 
  482         GETTHMEMBER(tvp, th_microtime);
  483 }
  484 #endif /* FFCLOCK */
  485 
  486 void
  487 getboottime(struct timeval *boottime)
  488 {
  489         struct bintime boottimebin;
  490 
  491         getboottimebin(&boottimebin);
  492         bintime2timeval(&boottimebin, boottime);
  493 }
  494 
  495 void
  496 getboottimebin(struct bintime *boottimebin)
  497 {
  498 
  499         GETTHMEMBER(boottimebin, th_boottime);
  500 }
  501 
  502 #ifdef FFCLOCK
  503 /*
  504  * Support for feed-forward synchronization algorithms. This is heavily inspired
  505  * by the timehands mechanism but kept independent from it. *_windup() functions
  506  * have some connection to avoid accessing the timecounter hardware more than
  507  * necessary.
  508  */
  509 
  510 /* Feed-forward clock estimates kept updated by the synchronization daemon. */
  511 struct ffclock_estimate ffclock_estimate;
  512 struct bintime ffclock_boottime;        /* Feed-forward boot time estimate. */
  513 uint32_t ffclock_status;                /* Feed-forward clock status. */
  514 int8_t ffclock_updated;                 /* New estimates are available. */
  515 struct mtx ffclock_mtx;                 /* Mutex on ffclock_estimate. */
  516 
  517 struct fftimehands {
  518         struct ffclock_estimate cest;
  519         struct bintime          tick_time;
  520         struct bintime          tick_time_lerp;
  521         ffcounter               tick_ffcount;
  522         uint64_t                period_lerp;
  523         volatile uint8_t        gen;
  524         struct fftimehands      *next;
  525 };
  526 
  527 #define NUM_ELEMENTS(x) (sizeof(x) / sizeof(*x))
  528 
  529 static struct fftimehands ffth[10];
  530 static struct fftimehands *volatile fftimehands = ffth;
  531 
  532 static void
  533 ffclock_init(void)
  534 {
  535         struct fftimehands *cur;
  536         struct fftimehands *last;
  537 
  538         memset(ffth, 0, sizeof(ffth));
  539 
  540         last = ffth + NUM_ELEMENTS(ffth) - 1;
  541         for (cur = ffth; cur < last; cur++)
  542                 cur->next = cur + 1;
  543         last->next = ffth;
  544 
  545         ffclock_updated = 0;
  546         ffclock_status = FFCLOCK_STA_UNSYNC;
  547         mtx_init(&ffclock_mtx, "ffclock lock", NULL, MTX_DEF);
  548 }
  549 
  550 /*
  551  * Reset the feed-forward clock estimates. Called from inittodr() to get things
  552  * kick started and uses the timecounter nominal frequency as a first period
  553  * estimate. Note: this function may be called several time just after boot.
  554  * Note: this is the only function that sets the value of boot time for the
  555  * monotonic (i.e. uptime) version of the feed-forward clock.
  556  */
  557 void
  558 ffclock_reset_clock(struct timespec *ts)
  559 {
  560         struct timecounter *tc;
  561         struct ffclock_estimate cest;
  562 
  563         tc = timehands->th_counter;
  564         memset(&cest, 0, sizeof(struct ffclock_estimate));
  565 
  566         timespec2bintime(ts, &ffclock_boottime);
  567         timespec2bintime(ts, &(cest.update_time));
  568         ffclock_read_counter(&cest.update_ffcount);
  569         cest.leapsec_next = 0;
  570         cest.period = ((1ULL << 63) / tc->tc_frequency) << 1;
  571         cest.errb_abs = 0;
  572         cest.errb_rate = 0;
  573         cest.status = FFCLOCK_STA_UNSYNC;
  574         cest.leapsec_total = 0;
  575         cest.leapsec = 0;
  576 
  577         mtx_lock(&ffclock_mtx);
  578         bcopy(&cest, &ffclock_estimate, sizeof(struct ffclock_estimate));
  579         ffclock_updated = INT8_MAX;
  580         mtx_unlock(&ffclock_mtx);
  581 
  582         printf("ffclock reset: %s (%llu Hz), time = %ld.%09lu\n", tc->tc_name,
  583             (unsigned long long)tc->tc_frequency, (long)ts->tv_sec,
  584             (unsigned long)ts->tv_nsec);
  585 }
  586 
  587 /*
  588  * Sub-routine to convert a time interval measured in RAW counter units to time
  589  * in seconds stored in bintime format.
  590  * NOTE: bintime_mul requires u_int, but the value of the ffcounter may be
  591  * larger than the max value of u_int (on 32 bit architecture). Loop to consume
  592  * extra cycles.
  593  */
  594 static void
  595 ffclock_convert_delta(ffcounter ffdelta, uint64_t period, struct bintime *bt)
  596 {
  597         struct bintime bt2;
  598         ffcounter delta, delta_max;
  599 
  600         delta_max = (1ULL << (8 * sizeof(unsigned int))) - 1;
  601         bintime_clear(bt);
  602         do {
  603                 if (ffdelta > delta_max)
  604                         delta = delta_max;
  605                 else
  606                         delta = ffdelta;
  607                 bt2.sec = 0;
  608                 bt2.frac = period;
  609                 bintime_mul(&bt2, (unsigned int)delta);
  610                 bintime_add(bt, &bt2);
  611                 ffdelta -= delta;
  612         } while (ffdelta > 0);
  613 }
  614 
  615 /*
  616  * Update the fftimehands.
  617  * Push the tick ffcount and time(s) forward based on current clock estimate.
  618  * The conversion from ffcounter to bintime relies on the difference clock
  619  * principle, whose accuracy relies on computing small time intervals. If a new
  620  * clock estimate has been passed by the synchronisation daemon, make it
  621  * current, and compute the linear interpolation for monotonic time if needed.
  622  */
  623 static void
  624 ffclock_windup(unsigned int delta)
  625 {
  626         struct ffclock_estimate *cest;
  627         struct fftimehands *ffth;
  628         struct bintime bt, gap_lerp;
  629         ffcounter ffdelta;
  630         uint64_t frac;
  631         unsigned int polling;
  632         uint8_t forward_jump, ogen;
  633 
  634         /*
  635          * Pick the next timehand, copy current ffclock estimates and move tick
  636          * times and counter forward.
  637          */
  638         forward_jump = 0;
  639         ffth = fftimehands->next;
  640         ogen = ffth->gen;
  641         ffth->gen = 0;
  642         cest = &ffth->cest;
  643         bcopy(&fftimehands->cest, cest, sizeof(struct ffclock_estimate));
  644         ffdelta = (ffcounter)delta;
  645         ffth->period_lerp = fftimehands->period_lerp;
  646 
  647         ffth->tick_time = fftimehands->tick_time;
  648         ffclock_convert_delta(ffdelta, cest->period, &bt);
  649         bintime_add(&ffth->tick_time, &bt);
  650 
  651         ffth->tick_time_lerp = fftimehands->tick_time_lerp;
  652         ffclock_convert_delta(ffdelta, ffth->period_lerp, &bt);
  653         bintime_add(&ffth->tick_time_lerp, &bt);
  654 
  655         ffth->tick_ffcount = fftimehands->tick_ffcount + ffdelta;
  656 
  657         /*
  658          * Assess the status of the clock, if the last update is too old, it is
  659          * likely the synchronisation daemon is dead and the clock is free
  660          * running.
  661          */
  662         if (ffclock_updated == 0) {
  663                 ffdelta = ffth->tick_ffcount - cest->update_ffcount;
  664                 ffclock_convert_delta(ffdelta, cest->period, &bt);
  665                 if (bt.sec > 2 * FFCLOCK_SKM_SCALE)
  666                         ffclock_status |= FFCLOCK_STA_UNSYNC;
  667         }
  668 
  669         /*
  670          * If available, grab updated clock estimates and make them current.
  671          * Recompute time at this tick using the updated estimates. The clock
  672          * estimates passed the feed-forward synchronisation daemon may result
  673          * in time conversion that is not monotonically increasing (just after
  674          * the update). time_lerp is a particular linear interpolation over the
  675          * synchronisation algo polling period that ensures monotonicity for the
  676          * clock ids requesting it.
  677          */
  678         if (ffclock_updated > 0) {
  679                 bcopy(&ffclock_estimate, cest, sizeof(struct ffclock_estimate));
  680                 ffdelta = ffth->tick_ffcount - cest->update_ffcount;
  681                 ffth->tick_time = cest->update_time;
  682                 ffclock_convert_delta(ffdelta, cest->period, &bt);
  683                 bintime_add(&ffth->tick_time, &bt);
  684 
  685                 /* ffclock_reset sets ffclock_updated to INT8_MAX */
  686                 if (ffclock_updated == INT8_MAX)
  687                         ffth->tick_time_lerp = ffth->tick_time;
  688 
  689                 if (bintime_cmp(&ffth->tick_time, &ffth->tick_time_lerp, >))
  690                         forward_jump = 1;
  691                 else
  692                         forward_jump = 0;
  693 
  694                 bintime_clear(&gap_lerp);
  695                 if (forward_jump) {
  696                         gap_lerp = ffth->tick_time;
  697                         bintime_sub(&gap_lerp, &ffth->tick_time_lerp);
  698                 } else {
  699                         gap_lerp = ffth->tick_time_lerp;
  700                         bintime_sub(&gap_lerp, &ffth->tick_time);
  701                 }
  702 
  703                 /*
  704                  * The reset from the RTC clock may be far from accurate, and
  705                  * reducing the gap between real time and interpolated time
  706                  * could take a very long time if the interpolated clock insists
  707                  * on strict monotonicity. The clock is reset under very strict
  708                  * conditions (kernel time is known to be wrong and
  709                  * synchronization daemon has been restarted recently.
  710                  * ffclock_boottime absorbs the jump to ensure boot time is
  711                  * correct and uptime functions stay consistent.
  712                  */
  713                 if (((ffclock_status & FFCLOCK_STA_UNSYNC) == FFCLOCK_STA_UNSYNC) &&
  714                     ((cest->status & FFCLOCK_STA_UNSYNC) == 0) &&
  715                     ((cest->status & FFCLOCK_STA_WARMUP) == FFCLOCK_STA_WARMUP)) {
  716                         if (forward_jump)
  717                                 bintime_add(&ffclock_boottime, &gap_lerp);
  718                         else
  719                                 bintime_sub(&ffclock_boottime, &gap_lerp);
  720                         ffth->tick_time_lerp = ffth->tick_time;
  721                         bintime_clear(&gap_lerp);
  722                 }
  723 
  724                 ffclock_status = cest->status;
  725                 ffth->period_lerp = cest->period;
  726 
  727                 /*
  728                  * Compute corrected period used for the linear interpolation of
  729                  * time. The rate of linear interpolation is capped to 5000PPM
  730                  * (5ms/s).
  731                  */
  732                 if (bintime_isset(&gap_lerp)) {
  733                         ffdelta = cest->update_ffcount;
  734                         ffdelta -= fftimehands->cest.update_ffcount;
  735                         ffclock_convert_delta(ffdelta, cest->period, &bt);
  736                         polling = bt.sec;
  737                         bt.sec = 0;
  738                         bt.frac = 5000000 * (uint64_t)18446744073LL;
  739                         bintime_mul(&bt, polling);
  740                         if (bintime_cmp(&gap_lerp, &bt, >))
  741                                 gap_lerp = bt;
  742 
  743                         /* Approximate 1 sec by 1-(1/2^64) to ease arithmetic */
  744                         frac = 0;
  745                         if (gap_lerp.sec > 0) {
  746                                 frac -= 1;
  747                                 frac /= ffdelta / gap_lerp.sec;
  748                         }
  749                         frac += gap_lerp.frac / ffdelta;
  750 
  751                         if (forward_jump)
  752                                 ffth->period_lerp += frac;
  753                         else
  754                                 ffth->period_lerp -= frac;
  755                 }
  756 
  757                 ffclock_updated = 0;
  758         }
  759         if (++ogen == 0)
  760                 ogen = 1;
  761         ffth->gen = ogen;
  762         fftimehands = ffth;
  763 }
  764 
  765 /*
  766  * Adjust the fftimehands when the timecounter is changed. Stating the obvious,
  767  * the old and new hardware counter cannot be read simultaneously. tc_windup()
  768  * does read the two counters 'back to back', but a few cycles are effectively
  769  * lost, and not accumulated in tick_ffcount. This is a fairly radical
  770  * operation for a feed-forward synchronization daemon, and it is its job to not
  771  * pushing irrelevant data to the kernel. Because there is no locking here,
  772  * simply force to ignore pending or next update to give daemon a chance to
  773  * realize the counter has changed.
  774  */
  775 static void
  776 ffclock_change_tc(struct timehands *th)
  777 {
  778         struct fftimehands *ffth;
  779         struct ffclock_estimate *cest;
  780         struct timecounter *tc;
  781         uint8_t ogen;
  782 
  783         tc = th->th_counter;
  784         ffth = fftimehands->next;
  785         ogen = ffth->gen;
  786         ffth->gen = 0;
  787 
  788         cest = &ffth->cest;
  789         bcopy(&(fftimehands->cest), cest, sizeof(struct ffclock_estimate));
  790         cest->period = ((1ULL << 63) / tc->tc_frequency ) << 1;
  791         cest->errb_abs = 0;
  792         cest->errb_rate = 0;
  793         cest->status |= FFCLOCK_STA_UNSYNC;
  794 
  795         ffth->tick_ffcount = fftimehands->tick_ffcount;
  796         ffth->tick_time_lerp = fftimehands->tick_time_lerp;
  797         ffth->tick_time = fftimehands->tick_time;
  798         ffth->period_lerp = cest->period;
  799 
  800         /* Do not lock but ignore next update from synchronization daemon. */
  801         ffclock_updated--;
  802 
  803         if (++ogen == 0)
  804                 ogen = 1;
  805         ffth->gen = ogen;
  806         fftimehands = ffth;
  807 }
  808 
  809 /*
  810  * Retrieve feed-forward counter and time of last kernel tick.
  811  */
  812 void
  813 ffclock_last_tick(ffcounter *ffcount, struct bintime *bt, uint32_t flags)
  814 {
  815         struct fftimehands *ffth;
  816         uint8_t gen;
  817 
  818         /*
  819          * No locking but check generation has not changed. Also need to make
  820          * sure ffdelta is positive, i.e. ffcount > tick_ffcount.
  821          */
  822         do {
  823                 ffth = fftimehands;
  824                 gen = ffth->gen;
  825                 if ((flags & FFCLOCK_LERP) == FFCLOCK_LERP)
  826                         *bt = ffth->tick_time_lerp;
  827                 else
  828                         *bt = ffth->tick_time;
  829                 *ffcount = ffth->tick_ffcount;
  830         } while (gen == 0 || gen != ffth->gen);
  831 }
  832 
  833 /*
  834  * Absolute clock conversion. Low level function to convert ffcounter to
  835  * bintime. The ffcounter is converted using the current ffclock period estimate
  836  * or the "interpolated period" to ensure monotonicity.
  837  * NOTE: this conversion may have been deferred, and the clock updated since the
  838  * hardware counter has been read.
  839  */
  840 void
  841 ffclock_convert_abs(ffcounter ffcount, struct bintime *bt, uint32_t flags)
  842 {
  843         struct fftimehands *ffth;
  844         struct bintime bt2;
  845         ffcounter ffdelta;
  846         uint8_t gen;
  847 
  848         /*
  849          * No locking but check generation has not changed. Also need to make
  850          * sure ffdelta is positive, i.e. ffcount > tick_ffcount.
  851          */
  852         do {
  853                 ffth = fftimehands;
  854                 gen = ffth->gen;
  855                 if (ffcount > ffth->tick_ffcount)
  856                         ffdelta = ffcount - ffth->tick_ffcount;
  857                 else
  858                         ffdelta = ffth->tick_ffcount - ffcount;
  859 
  860                 if ((flags & FFCLOCK_LERP) == FFCLOCK_LERP) {
  861                         *bt = ffth->tick_time_lerp;
  862                         ffclock_convert_delta(ffdelta, ffth->period_lerp, &bt2);
  863                 } else {
  864                         *bt = ffth->tick_time;
  865                         ffclock_convert_delta(ffdelta, ffth->cest.period, &bt2);
  866                 }
  867 
  868                 if (ffcount > ffth->tick_ffcount)
  869                         bintime_add(bt, &bt2);
  870                 else
  871                         bintime_sub(bt, &bt2);
  872         } while (gen == 0 || gen != ffth->gen);
  873 }
  874 
  875 /*
  876  * Difference clock conversion.
  877  * Low level function to Convert a time interval measured in RAW counter units
  878  * into bintime. The difference clock allows measuring small intervals much more
  879  * reliably than the absolute clock.
  880  */
  881 void
  882 ffclock_convert_diff(ffcounter ffdelta, struct bintime *bt)
  883 {
  884         struct fftimehands *ffth;
  885         uint8_t gen;
  886 
  887         /* No locking but check generation has not changed. */
  888         do {
  889                 ffth = fftimehands;
  890                 gen = ffth->gen;
  891                 ffclock_convert_delta(ffdelta, ffth->cest.period, bt);
  892         } while (gen == 0 || gen != ffth->gen);
  893 }
  894 
  895 /*
  896  * Access to current ffcounter value.
  897  */
  898 void
  899 ffclock_read_counter(ffcounter *ffcount)
  900 {
  901         struct timehands *th;
  902         struct fftimehands *ffth;
  903         unsigned int gen, delta;
  904 
  905         /*
  906          * ffclock_windup() called from tc_windup(), safe to rely on
  907          * th->th_generation only, for correct delta and ffcounter.
  908          */
  909         do {
  910                 th = timehands;
  911                 gen = atomic_load_acq_int(&th->th_generation);
  912                 ffth = fftimehands;
  913                 delta = tc_delta(th);
  914                 *ffcount = ffth->tick_ffcount;
  915                 atomic_thread_fence_acq();
  916         } while (gen == 0 || gen != th->th_generation);
  917 
  918         *ffcount += delta;
  919 }
  920 
  921 void
  922 binuptime(struct bintime *bt)
  923 {
  924 
  925         binuptime_fromclock(bt, sysclock_active);
  926 }
  927 
  928 void
  929 nanouptime(struct timespec *tsp)
  930 {
  931 
  932         nanouptime_fromclock(tsp, sysclock_active);
  933 }
  934 
  935 void
  936 microuptime(struct timeval *tvp)
  937 {
  938 
  939         microuptime_fromclock(tvp, sysclock_active);
  940 }
  941 
  942 void
  943 bintime(struct bintime *bt)
  944 {
  945 
  946         bintime_fromclock(bt, sysclock_active);
  947 }
  948 
  949 void
  950 nanotime(struct timespec *tsp)
  951 {
  952 
  953         nanotime_fromclock(tsp, sysclock_active);
  954 }
  955 
  956 void
  957 microtime(struct timeval *tvp)
  958 {
  959 
  960         microtime_fromclock(tvp, sysclock_active);
  961 }
  962 
  963 void
  964 getbinuptime(struct bintime *bt)
  965 {
  966 
  967         getbinuptime_fromclock(bt, sysclock_active);
  968 }
  969 
  970 void
  971 getnanouptime(struct timespec *tsp)
  972 {
  973 
  974         getnanouptime_fromclock(tsp, sysclock_active);
  975 }
  976 
  977 void
  978 getmicrouptime(struct timeval *tvp)
  979 {
  980 
  981         getmicrouptime_fromclock(tvp, sysclock_active);
  982 }
  983 
  984 void
  985 getbintime(struct bintime *bt)
  986 {
  987 
  988         getbintime_fromclock(bt, sysclock_active);
  989 }
  990 
  991 void
  992 getnanotime(struct timespec *tsp)
  993 {
  994 
  995         getnanotime_fromclock(tsp, sysclock_active);
  996 }
  997 
  998 void
  999 getmicrotime(struct timeval *tvp)
 1000 {
 1001 
 1002         getmicrouptime_fromclock(tvp, sysclock_active);
 1003 }
 1004 
 1005 #endif /* FFCLOCK */
 1006 
 1007 /*
 1008  * This is a clone of getnanotime and used for walltimestamps.
 1009  * The dtrace_ prefix prevents fbt from creating probes for
 1010  * it so walltimestamp can be safely used in all fbt probes.
 1011  */
 1012 void
 1013 dtrace_getnanotime(struct timespec *tsp)
 1014 {
 1015 
 1016         GETTHMEMBER(tsp, th_nanotime);
 1017 }
 1018 
 1019 /*
 1020  * This is a clone of getnanouptime used for time since boot.
 1021  * The dtrace_ prefix prevents fbt from creating probes for
 1022  * it so an uptime that can be safely used in all fbt probes.
 1023  */
 1024 void
 1025 dtrace_getnanouptime(struct timespec *tsp)
 1026 {
 1027         struct bintime bt;
 1028 
 1029         GETTHMEMBER(&bt, th_offset);
 1030         bintime2timespec(&bt, tsp);
 1031 }
 1032 
 1033 /*
 1034  * System clock currently providing time to the system. Modifiable via sysctl
 1035  * when the FFCLOCK option is defined.
 1036  */
 1037 int sysclock_active = SYSCLOCK_FBCK;
 1038 
 1039 /* Internal NTP status and error estimates. */
 1040 extern int time_status;
 1041 extern long time_esterror;
 1042 
 1043 /*
 1044  * Take a snapshot of sysclock data which can be used to compare system clocks
 1045  * and generate timestamps after the fact.
 1046  */
 1047 void
 1048 sysclock_getsnapshot(struct sysclock_snap *clock_snap, int fast)
 1049 {
 1050         struct fbclock_info *fbi;
 1051         struct timehands *th;
 1052         struct bintime bt;
 1053         unsigned int delta, gen;
 1054 #ifdef FFCLOCK
 1055         ffcounter ffcount;
 1056         struct fftimehands *ffth;
 1057         struct ffclock_info *ffi;
 1058         struct ffclock_estimate cest;
 1059 
 1060         ffi = &clock_snap->ff_info;
 1061 #endif
 1062 
 1063         fbi = &clock_snap->fb_info;
 1064         delta = 0;
 1065 
 1066         do {
 1067                 th = timehands;
 1068                 gen = atomic_load_acq_int(&th->th_generation);
 1069                 fbi->th_scale = th->th_scale;
 1070                 fbi->tick_time = th->th_offset;
 1071 #ifdef FFCLOCK
 1072                 ffth = fftimehands;
 1073                 ffi->tick_time = ffth->tick_time_lerp;
 1074                 ffi->tick_time_lerp = ffth->tick_time_lerp;
 1075                 ffi->period = ffth->cest.period;
 1076                 ffi->period_lerp = ffth->period_lerp;
 1077                 clock_snap->ffcount = ffth->tick_ffcount;
 1078                 cest = ffth->cest;
 1079 #endif
 1080                 if (!fast)
 1081                         delta = tc_delta(th);
 1082                 atomic_thread_fence_acq();
 1083         } while (gen == 0 || gen != th->th_generation);
 1084 
 1085         clock_snap->delta = delta;
 1086         clock_snap->sysclock_active = sysclock_active;
 1087 
 1088         /* Record feedback clock status and error. */
 1089         clock_snap->fb_info.status = time_status;
 1090         /* XXX: Very crude estimate of feedback clock error. */
 1091         bt.sec = time_esterror / 1000000;
 1092         bt.frac = ((time_esterror - bt.sec) * 1000000) *
 1093             (uint64_t)18446744073709ULL;
 1094         clock_snap->fb_info.error = bt;
 1095 
 1096 #ifdef FFCLOCK
 1097         if (!fast)
 1098                 clock_snap->ffcount += delta;
 1099 
 1100         /* Record feed-forward clock leap second adjustment. */
 1101         ffi->leapsec_adjustment = cest.leapsec_total;
 1102         if (clock_snap->ffcount > cest.leapsec_next)
 1103                 ffi->leapsec_adjustment -= cest.leapsec;
 1104 
 1105         /* Record feed-forward clock status and error. */
 1106         clock_snap->ff_info.status = cest.status;
 1107         ffcount = clock_snap->ffcount - cest.update_ffcount;
 1108         ffclock_convert_delta(ffcount, cest.period, &bt);
 1109         /* 18446744073709 = int(2^64/1e12), err_bound_rate in [ps/s]. */
 1110         bintime_mul(&bt, cest.errb_rate * (uint64_t)18446744073709ULL);
 1111         /* 18446744073 = int(2^64 / 1e9), since err_abs in [ns]. */
 1112         bintime_addx(&bt, cest.errb_abs * (uint64_t)18446744073ULL);
 1113         clock_snap->ff_info.error = bt;
 1114 #endif
 1115 }
 1116 
 1117 /*
 1118  * Convert a sysclock snapshot into a struct bintime based on the specified
 1119  * clock source and flags.
 1120  */
 1121 int
 1122 sysclock_snap2bintime(struct sysclock_snap *cs, struct bintime *bt,
 1123     int whichclock, uint32_t flags)
 1124 {
 1125         struct bintime boottimebin;
 1126 #ifdef FFCLOCK
 1127         struct bintime bt2;
 1128         uint64_t period;
 1129 #endif
 1130 
 1131         switch (whichclock) {
 1132         case SYSCLOCK_FBCK:
 1133                 *bt = cs->fb_info.tick_time;
 1134 
 1135                 /* If snapshot was created with !fast, delta will be >0. */
 1136                 if (cs->delta > 0)
 1137                         bintime_addx(bt, cs->fb_info.th_scale * cs->delta);
 1138 
 1139                 if ((flags & FBCLOCK_UPTIME) == 0) {
 1140                         getboottimebin(&boottimebin);
 1141                         bintime_add(bt, &boottimebin);
 1142                 }
 1143                 break;
 1144 #ifdef FFCLOCK
 1145         case SYSCLOCK_FFWD:
 1146                 if (flags & FFCLOCK_LERP) {
 1147                         *bt = cs->ff_info.tick_time_lerp;
 1148                         period = cs->ff_info.period_lerp;
 1149                 } else {
 1150                         *bt = cs->ff_info.tick_time;
 1151                         period = cs->ff_info.period;
 1152                 }
 1153 
 1154                 /* If snapshot was created with !fast, delta will be >0. */
 1155                 if (cs->delta > 0) {
 1156                         ffclock_convert_delta(cs->delta, period, &bt2);
 1157                         bintime_add(bt, &bt2);
 1158                 }
 1159 
 1160                 /* Leap second adjustment. */
 1161                 if (flags & FFCLOCK_LEAPSEC)
 1162                         bt->sec -= cs->ff_info.leapsec_adjustment;
 1163 
 1164                 /* Boot time adjustment, for uptime/monotonic clocks. */
 1165                 if (flags & FFCLOCK_UPTIME)
 1166                         bintime_sub(bt, &ffclock_boottime);
 1167                 break;
 1168 #endif
 1169         default:
 1170                 return (EINVAL);
 1171                 break;
 1172         }
 1173 
 1174         return (0);
 1175 }
 1176 
 1177 /*
 1178  * Initialize a new timecounter and possibly use it.
 1179  */
 1180 void
 1181 tc_init(struct timecounter *tc)
 1182 {
 1183         u_int u;
 1184         struct sysctl_oid *tc_root;
 1185 
 1186         u = tc->tc_frequency / tc->tc_counter_mask;
 1187         /* XXX: We need some margin here, 10% is a guess */
 1188         u *= 11;
 1189         u /= 10;
 1190         if (u > hz && tc->tc_quality >= 0) {
 1191                 tc->tc_quality = -2000;
 1192                 if (bootverbose) {
 1193                         printf("Timecounter \"%s\" frequency %ju Hz",
 1194                             tc->tc_name, (uintmax_t)tc->tc_frequency);
 1195                         printf(" -- Insufficient hz, needs at least %u\n", u);
 1196                 }
 1197         } else if (tc->tc_quality >= 0 || bootverbose) {
 1198                 printf("Timecounter \"%s\" frequency %ju Hz quality %d\n",
 1199                     tc->tc_name, (uintmax_t)tc->tc_frequency,
 1200                     tc->tc_quality);
 1201         }
 1202 
 1203         /*
 1204          * Set up sysctl tree for this counter.
 1205          */
 1206         tc_root = SYSCTL_ADD_NODE_WITH_LABEL(NULL,
 1207             SYSCTL_STATIC_CHILDREN(_kern_timecounter_tc), OID_AUTO, tc->tc_name,
 1208             CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
 1209             "timecounter description", "timecounter");
 1210         SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
 1211             "mask", CTLFLAG_RD, &(tc->tc_counter_mask), 0,
 1212             "mask for implemented bits");
 1213         SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
 1214             "counter", CTLTYPE_UINT | CTLFLAG_RD | CTLFLAG_MPSAFE, tc,
 1215             sizeof(*tc), sysctl_kern_timecounter_get, "IU",
 1216             "current timecounter value");
 1217         SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
 1218             "frequency", CTLTYPE_U64 | CTLFLAG_RD | CTLFLAG_MPSAFE, tc,
 1219             sizeof(*tc), sysctl_kern_timecounter_freq, "QU",
 1220             "timecounter frequency");
 1221         SYSCTL_ADD_INT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
 1222             "quality", CTLFLAG_RD, &(tc->tc_quality), 0,
 1223             "goodness of time counter");
 1224 
 1225         mtx_lock(&tc_lock);
 1226         tc->tc_next = timecounters;
 1227         timecounters = tc;
 1228 
 1229         /*
 1230          * Do not automatically switch if the current tc was specifically
 1231          * chosen.  Never automatically use a timecounter with negative quality.
 1232          * Even though we run on the dummy counter, switching here may be
 1233          * worse since this timecounter may not be monotonic.
 1234          */
 1235         if (tc_chosen)
 1236                 goto unlock;
 1237         if (tc->tc_quality < 0)
 1238                 goto unlock;
 1239         if (tc_from_tunable[0] != '\0' &&
 1240             strcmp(tc->tc_name, tc_from_tunable) == 0) {
 1241                 tc_chosen = 1;
 1242                 tc_from_tunable[0] = '\0';
 1243         } else {
 1244                 if (tc->tc_quality < timecounter->tc_quality)
 1245                         goto unlock;
 1246                 if (tc->tc_quality == timecounter->tc_quality &&
 1247                     tc->tc_frequency < timecounter->tc_frequency)
 1248                         goto unlock;
 1249         }
 1250         (void)tc->tc_get_timecount(tc);
 1251         timecounter = tc;
 1252 unlock:
 1253         mtx_unlock(&tc_lock);
 1254 }
 1255 
 1256 /* Report the frequency of the current timecounter. */
 1257 uint64_t
 1258 tc_getfrequency(void)
 1259 {
 1260 
 1261         return (timehands->th_counter->tc_frequency);
 1262 }
 1263 
 1264 static bool
 1265 sleeping_on_old_rtc(struct thread *td)
 1266 {
 1267 
 1268         /*
 1269          * td_rtcgen is modified by curthread when it is running,
 1270          * and by other threads in this function.  By finding the thread
 1271          * on a sleepqueue and holding the lock on the sleepqueue
 1272          * chain, we guarantee that the thread is not running and that
 1273          * modifying td_rtcgen is safe.  Setting td_rtcgen to zero informs
 1274          * the thread that it was woken due to a real-time clock adjustment.
 1275          * (The declaration of td_rtcgen refers to this comment.)
 1276          */
 1277         if (td->td_rtcgen != 0 && td->td_rtcgen != rtc_generation) {
 1278                 td->td_rtcgen = 0;
 1279                 return (true);
 1280         }
 1281         return (false);
 1282 }
 1283 
 1284 static struct mtx tc_setclock_mtx;
 1285 MTX_SYSINIT(tc_setclock_init, &tc_setclock_mtx, "tcsetc", MTX_SPIN);
 1286 
 1287 /*
 1288  * Step our concept of UTC.  This is done by modifying our estimate of
 1289  * when we booted.
 1290  */
 1291 void
 1292 tc_setclock(struct timespec *ts)
 1293 {
 1294         struct timespec tbef, taft;
 1295         struct bintime bt, bt2;
 1296 
 1297         timespec2bintime(ts, &bt);
 1298         nanotime(&tbef);
 1299         mtx_lock_spin(&tc_setclock_mtx);
 1300         cpu_tick_calibrate(1);
 1301         binuptime(&bt2);
 1302         bintime_sub(&bt, &bt2);
 1303 
 1304         /* XXX fiddle all the little crinkly bits around the fiords... */
 1305         tc_windup(&bt);
 1306         mtx_unlock_spin(&tc_setclock_mtx);
 1307 
 1308         /* Avoid rtc_generation == 0, since td_rtcgen == 0 is special. */
 1309         atomic_add_rel_int(&rtc_generation, 2);
 1310         sleepq_chains_remove_matching(sleeping_on_old_rtc);
 1311         if (timestepwarnings) {
 1312                 nanotime(&taft);
 1313                 log(LOG_INFO,
 1314                     "Time stepped from %jd.%09ld to %jd.%09ld (%jd.%09ld)\n",
 1315                     (intmax_t)tbef.tv_sec, tbef.tv_nsec,
 1316                     (intmax_t)taft.tv_sec, taft.tv_nsec,
 1317                     (intmax_t)ts->tv_sec, ts->tv_nsec);
 1318         }
 1319 }
 1320 
 1321 /*
 1322  * Recalculate the scaling factor.  We want the number of 1/2^64
 1323  * fractions of a second per period of the hardware counter, taking
 1324  * into account the th_adjustment factor which the NTP PLL/adjtime(2)
 1325  * processing provides us with.
 1326  *
 1327  * The th_adjustment is nanoseconds per second with 32 bit binary
 1328  * fraction and we want 64 bit binary fraction of second:
 1329  *
 1330  *       x = a * 2^32 / 10^9 = a * 4.294967296
 1331  *
 1332  * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
 1333  * we can only multiply by about 850 without overflowing, that
 1334  * leaves no suitably precise fractions for multiply before divide.
 1335  *
 1336  * Divide before multiply with a fraction of 2199/512 results in a
 1337  * systematic undercompensation of 10PPM of th_adjustment.  On a
 1338  * 5000PPM adjustment this is a 0.05PPM error.  This is acceptable.
 1339  *
 1340  * We happily sacrifice the lowest of the 64 bits of our result
 1341  * to the goddess of code clarity.
 1342  */
 1343 static void
 1344 recalculate_scaling_factor_and_large_delta(struct timehands *th)
 1345 {
 1346         uint64_t scale;
 1347 
 1348         scale = (uint64_t)1 << 63;
 1349         scale += (th->th_adjustment / 1024) * 2199;
 1350         scale /= th->th_counter->tc_frequency;
 1351         th->th_scale = scale * 2;
 1352         th->th_large_delta = MIN(((uint64_t)1 << 63) / scale, UINT_MAX);
 1353 }
 1354 
 1355 /*
 1356  * Initialize the next struct timehands in the ring and make
 1357  * it the active timehands.  Along the way we might switch to a different
 1358  * timecounter and/or do seconds processing in NTP.  Slightly magic.
 1359  */
 1360 static void
 1361 tc_windup(struct bintime *new_boottimebin)
 1362 {
 1363         struct bintime bt;
 1364         struct timecounter *tc;
 1365         struct timehands *th, *tho;
 1366         u_int delta, ncount, ogen;
 1367         int i;
 1368         time_t t;
 1369 
 1370         /*
 1371          * Make the next timehands a copy of the current one, but do
 1372          * not overwrite the generation or next pointer.  While we
 1373          * update the contents, the generation must be zero.  We need
 1374          * to ensure that the zero generation is visible before the
 1375          * data updates become visible, which requires release fence.
 1376          * For similar reasons, re-reading of the generation after the
 1377          * data is read should use acquire fence.
 1378          */
 1379         tho = timehands;
 1380         th = tho->th_next;
 1381         ogen = th->th_generation;
 1382         th->th_generation = 0;
 1383         atomic_thread_fence_rel();
 1384         memcpy(th, tho, offsetof(struct timehands, th_generation));
 1385         if (new_boottimebin != NULL)
 1386                 th->th_boottime = *new_boottimebin;
 1387 
 1388         /*
 1389          * Capture a timecounter delta on the current timecounter and if
 1390          * changing timecounters, a counter value from the new timecounter.
 1391          * Update the offset fields accordingly.
 1392          */
 1393         tc = atomic_load_ptr(&timecounter);
 1394         delta = tc_delta(th);
 1395         if (th->th_counter != tc)
 1396                 ncount = tc->tc_get_timecount(tc);
 1397         else
 1398                 ncount = 0;
 1399 #ifdef FFCLOCK
 1400         ffclock_windup(delta);
 1401 #endif
 1402         th->th_offset_count += delta;
 1403         th->th_offset_count &= th->th_counter->tc_counter_mask;
 1404         bintime_add_tc_delta(&th->th_offset, th->th_scale,
 1405             th->th_large_delta, delta);
 1406 
 1407         /*
 1408          * Hardware latching timecounters may not generate interrupts on
 1409          * PPS events, so instead we poll them.  There is a finite risk that
 1410          * the hardware might capture a count which is later than the one we
 1411          * got above, and therefore possibly in the next NTP second which might
 1412          * have a different rate than the current NTP second.  It doesn't
 1413          * matter in practice.
 1414          */
 1415         if (tho->th_counter->tc_poll_pps)
 1416                 tho->th_counter->tc_poll_pps(tho->th_counter);
 1417 
 1418         /*
 1419          * Deal with NTP second processing.  The loop normally
 1420          * iterates at most once, but in extreme situations it might
 1421          * keep NTP sane if timeouts are not run for several seconds.
 1422          * At boot, the time step can be large when the TOD hardware
 1423          * has been read, so on really large steps, we call
 1424          * ntp_update_second only twice.  We need to call it twice in
 1425          * case we missed a leap second.
 1426          */
 1427         bt = th->th_offset;
 1428         bintime_add(&bt, &th->th_boottime);
 1429         i = bt.sec - tho->th_microtime.tv_sec;
 1430         if (i > 0) {
 1431                 if (i > LARGE_STEP)
 1432                         i = 2;
 1433 
 1434                 do {
 1435                         t = bt.sec;
 1436                         ntp_update_second(&th->th_adjustment, &bt.sec);
 1437                         if (bt.sec != t)
 1438                                 th->th_boottime.sec += bt.sec - t;
 1439                         --i;
 1440                 } while (i > 0);
 1441 
 1442                 recalculate_scaling_factor_and_large_delta(th);
 1443         }
 1444 
 1445         /* Update the UTC timestamps used by the get*() functions. */
 1446         th->th_bintime = bt;
 1447         bintime2timeval(&bt, &th->th_microtime);
 1448         bintime2timespec(&bt, &th->th_nanotime);
 1449 
 1450         /* Now is a good time to change timecounters. */
 1451         if (th->th_counter != tc) {
 1452 #ifndef __arm__
 1453                 if ((tc->tc_flags & TC_FLAGS_C2STOP) != 0)
 1454                         cpu_disable_c2_sleep++;
 1455                 if ((th->th_counter->tc_flags & TC_FLAGS_C2STOP) != 0)
 1456                         cpu_disable_c2_sleep--;
 1457 #endif
 1458                 th->th_counter = tc;
 1459                 th->th_offset_count = ncount;
 1460                 tc_min_ticktock_freq = max(1, tc->tc_frequency /
 1461                     (((uint64_t)tc->tc_counter_mask + 1) / 3));
 1462                 recalculate_scaling_factor_and_large_delta(th);
 1463 #ifdef FFCLOCK
 1464                 ffclock_change_tc(th);
 1465 #endif
 1466         }
 1467 
 1468         /*
 1469          * Now that the struct timehands is again consistent, set the new
 1470          * generation number, making sure to not make it zero.
 1471          */
 1472         if (++ogen == 0)
 1473                 ogen = 1;
 1474         atomic_store_rel_int(&th->th_generation, ogen);
 1475 
 1476         /* Go live with the new struct timehands. */
 1477 #ifdef FFCLOCK
 1478         switch (sysclock_active) {
 1479         case SYSCLOCK_FBCK:
 1480 #endif
 1481                 time_second = th->th_microtime.tv_sec;
 1482                 time_uptime = th->th_offset.sec;
 1483 #ifdef FFCLOCK
 1484                 break;
 1485         case SYSCLOCK_FFWD:
 1486                 time_second = fftimehands->tick_time_lerp.sec;
 1487                 time_uptime = fftimehands->tick_time_lerp.sec - ffclock_boottime.sec;
 1488                 break;
 1489         }
 1490 #endif
 1491 
 1492         timehands = th;
 1493         timekeep_push_vdso();
 1494 }
 1495 
 1496 /* Report or change the active timecounter hardware. */
 1497 static int
 1498 sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
 1499 {
 1500         char newname[32];
 1501         struct timecounter *newtc, *tc;
 1502         int error;
 1503 
 1504         mtx_lock(&tc_lock);
 1505         tc = timecounter;
 1506         strlcpy(newname, tc->tc_name, sizeof(newname));
 1507         mtx_unlock(&tc_lock);
 1508 
 1509         error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
 1510         if (error != 0 || req->newptr == NULL)
 1511                 return (error);
 1512 
 1513         mtx_lock(&tc_lock);
 1514         /* Record that the tc in use now was specifically chosen. */
 1515         tc_chosen = 1;
 1516         if (strcmp(newname, tc->tc_name) == 0) {
 1517                 mtx_unlock(&tc_lock);
 1518                 return (0);
 1519         }
 1520         for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
 1521                 if (strcmp(newname, newtc->tc_name) != 0)
 1522                         continue;
 1523 
 1524                 /* Warm up new timecounter. */
 1525                 (void)newtc->tc_get_timecount(newtc);
 1526 
 1527                 timecounter = newtc;
 1528 
 1529                 /*
 1530                  * The vdso timehands update is deferred until the next
 1531                  * 'tc_windup()'.
 1532                  *
 1533                  * This is prudent given that 'timekeep_push_vdso()' does not
 1534                  * use any locking and that it can be called in hard interrupt
 1535                  * context via 'tc_windup()'.
 1536                  */
 1537                 break;
 1538         }
 1539         mtx_unlock(&tc_lock);
 1540         return (newtc != NULL ? 0 : EINVAL);
 1541 }
 1542 SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware,
 1543     CTLTYPE_STRING | CTLFLAG_RWTUN | CTLFLAG_NOFETCH | CTLFLAG_MPSAFE, 0, 0,
 1544     sysctl_kern_timecounter_hardware, "A",
 1545     "Timecounter hardware selected");
 1546 
 1547 /* Report the available timecounter hardware. */
 1548 static int
 1549 sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS)
 1550 {
 1551         struct sbuf sb;
 1552         struct timecounter *tc;
 1553         int error;
 1554 
 1555         error = sysctl_wire_old_buffer(req, 0);
 1556         if (error != 0)
 1557                 return (error);
 1558         sbuf_new_for_sysctl(&sb, NULL, 0, req);
 1559         mtx_lock(&tc_lock);
 1560         for (tc = timecounters; tc != NULL; tc = tc->tc_next) {
 1561                 if (tc != timecounters)
 1562                         sbuf_putc(&sb, ' ');
 1563                 sbuf_printf(&sb, "%s(%d)", tc->tc_name, tc->tc_quality);
 1564         }
 1565         mtx_unlock(&tc_lock);
 1566         error = sbuf_finish(&sb);
 1567         sbuf_delete(&sb);
 1568         return (error);
 1569 }
 1570 
 1571 SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice,
 1572     CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE, 0, 0,
 1573     sysctl_kern_timecounter_choice, "A",
 1574     "Timecounter hardware detected");
 1575 
 1576 /*
 1577  * RFC 2783 PPS-API implementation.
 1578  */
 1579 
 1580 /*
 1581  *  Return true if the driver is aware of the abi version extensions in the
 1582  *  pps_state structure, and it supports at least the given abi version number.
 1583  */
 1584 static inline int
 1585 abi_aware(struct pps_state *pps, int vers)
 1586 {
 1587 
 1588         return ((pps->kcmode & KCMODE_ABIFLAG) && pps->driver_abi >= vers);
 1589 }
 1590 
 1591 static int
 1592 pps_fetch(struct pps_fetch_args *fapi, struct pps_state *pps)
 1593 {
 1594         int err, timo;
 1595         pps_seq_t aseq, cseq;
 1596         struct timeval tv;
 1597 
 1598         if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
 1599                 return (EINVAL);
 1600 
 1601         /*
 1602          * If no timeout is requested, immediately return whatever values were
 1603          * most recently captured.  If timeout seconds is -1, that's a request
 1604          * to block without a timeout.  WITNESS won't let us sleep forever
 1605          * without a lock (we really don't need a lock), so just repeatedly
 1606          * sleep a long time.
 1607          */
 1608         if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec) {
 1609                 if (fapi->timeout.tv_sec == -1)
 1610                         timo = 0x7fffffff;
 1611                 else {
 1612                         tv.tv_sec = fapi->timeout.tv_sec;
 1613                         tv.tv_usec = fapi->timeout.tv_nsec / 1000;
 1614                         timo = tvtohz(&tv);
 1615                 }
 1616                 aseq = atomic_load_int(&pps->ppsinfo.assert_sequence);
 1617                 cseq = atomic_load_int(&pps->ppsinfo.clear_sequence);
 1618                 while (aseq == atomic_load_int(&pps->ppsinfo.assert_sequence) &&
 1619                     cseq == atomic_load_int(&pps->ppsinfo.clear_sequence)) {
 1620                         if (abi_aware(pps, 1) && pps->driver_mtx != NULL) {
 1621                                 if (pps->flags & PPSFLAG_MTX_SPIN) {
 1622                                         err = msleep_spin(pps, pps->driver_mtx,
 1623                                             "ppsfch", timo);
 1624                                 } else {
 1625                                         err = msleep(pps, pps->driver_mtx, PCATCH,
 1626                                             "ppsfch", timo);
 1627                                 }
 1628                         } else {
 1629                                 err = tsleep(pps, PCATCH, "ppsfch", timo);
 1630                         }
 1631                         if (err == EWOULDBLOCK) {
 1632                                 if (fapi->timeout.tv_sec == -1) {
 1633                                         continue;
 1634                                 } else {
 1635                                         return (ETIMEDOUT);
 1636                                 }
 1637                         } else if (err != 0) {
 1638                                 return (err);
 1639                         }
 1640                 }
 1641         }
 1642 
 1643         pps->ppsinfo.current_mode = pps->ppsparam.mode;
 1644         fapi->pps_info_buf = pps->ppsinfo;
 1645 
 1646         return (0);
 1647 }
 1648 
 1649 int
 1650 pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
 1651 {
 1652         pps_params_t *app;
 1653         struct pps_fetch_args *fapi;
 1654 #ifdef FFCLOCK
 1655         struct pps_fetch_ffc_args *fapi_ffc;
 1656 #endif
 1657 #ifdef PPS_SYNC
 1658         struct pps_kcbind_args *kapi;
 1659 #endif
 1660 
 1661         KASSERT(pps != NULL, ("NULL pps pointer in pps_ioctl"));
 1662         switch (cmd) {
 1663         case PPS_IOC_CREATE:
 1664                 return (0);
 1665         case PPS_IOC_DESTROY:
 1666                 return (0);
 1667         case PPS_IOC_SETPARAMS:
 1668                 app = (pps_params_t *)data;
 1669                 if (app->mode & ~pps->ppscap)
 1670                         return (EINVAL);
 1671 #ifdef FFCLOCK
 1672                 /* Ensure only a single clock is selected for ffc timestamp. */
 1673                 if ((app->mode & PPS_TSCLK_MASK) == PPS_TSCLK_MASK)
 1674                         return (EINVAL);
 1675 #endif
 1676                 pps->ppsparam = *app;
 1677                 return (0);
 1678         case PPS_IOC_GETPARAMS:
 1679                 app = (pps_params_t *)data;
 1680                 *app = pps->ppsparam;
 1681                 app->api_version = PPS_API_VERS_1;
 1682                 return (0);
 1683         case PPS_IOC_GETCAP:
 1684                 *(int*)data = pps->ppscap;
 1685                 return (0);
 1686         case PPS_IOC_FETCH:
 1687                 fapi = (struct pps_fetch_args *)data;
 1688                 return (pps_fetch(fapi, pps));
 1689 #ifdef FFCLOCK
 1690         case PPS_IOC_FETCH_FFCOUNTER:
 1691                 fapi_ffc = (struct pps_fetch_ffc_args *)data;
 1692                 if (fapi_ffc->tsformat && fapi_ffc->tsformat !=
 1693                     PPS_TSFMT_TSPEC)
 1694                         return (EINVAL);
 1695                 if (fapi_ffc->timeout.tv_sec || fapi_ffc->timeout.tv_nsec)
 1696                         return (EOPNOTSUPP);
 1697                 pps->ppsinfo_ffc.current_mode = pps->ppsparam.mode;
 1698                 fapi_ffc->pps_info_buf_ffc = pps->ppsinfo_ffc;
 1699                 /* Overwrite timestamps if feedback clock selected. */
 1700                 switch (pps->ppsparam.mode & PPS_TSCLK_MASK) {
 1701                 case PPS_TSCLK_FBCK:
 1702                         fapi_ffc->pps_info_buf_ffc.assert_timestamp =
 1703                             pps->ppsinfo.assert_timestamp;
 1704                         fapi_ffc->pps_info_buf_ffc.clear_timestamp =
 1705                             pps->ppsinfo.clear_timestamp;
 1706                         break;
 1707                 case PPS_TSCLK_FFWD:
 1708                         break;
 1709                 default:
 1710                         break;
 1711                 }
 1712                 return (0);
 1713 #endif /* FFCLOCK */
 1714         case PPS_IOC_KCBIND:
 1715 #ifdef PPS_SYNC
 1716                 kapi = (struct pps_kcbind_args *)data;
 1717                 /* XXX Only root should be able to do this */
 1718                 if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
 1719                         return (EINVAL);
 1720                 if (kapi->kernel_consumer != PPS_KC_HARDPPS)
 1721                         return (EINVAL);
 1722                 if (kapi->edge & ~pps->ppscap)
 1723                         return (EINVAL);
 1724                 pps->kcmode = (kapi->edge & KCMODE_EDGEMASK) |
 1725                     (pps->kcmode & KCMODE_ABIFLAG);
 1726                 return (0);
 1727 #else
 1728                 return (EOPNOTSUPP);
 1729 #endif
 1730         default:
 1731                 return (ENOIOCTL);
 1732         }
 1733 }
 1734 
 1735 void
 1736 pps_init(struct pps_state *pps)
 1737 {
 1738         pps->ppscap |= PPS_TSFMT_TSPEC | PPS_CANWAIT;
 1739         if (pps->ppscap & PPS_CAPTUREASSERT)
 1740                 pps->ppscap |= PPS_OFFSETASSERT;
 1741         if (pps->ppscap & PPS_CAPTURECLEAR)
 1742                 pps->ppscap |= PPS_OFFSETCLEAR;
 1743 #ifdef FFCLOCK
 1744         pps->ppscap |= PPS_TSCLK_MASK;
 1745 #endif
 1746         pps->kcmode &= ~KCMODE_ABIFLAG;
 1747 }
 1748 
 1749 void
 1750 pps_init_abi(struct pps_state *pps)
 1751 {
 1752 
 1753         pps_init(pps);
 1754         if (pps->driver_abi > 0) {
 1755                 pps->kcmode |= KCMODE_ABIFLAG;
 1756                 pps->kernel_abi = PPS_ABI_VERSION;
 1757         }
 1758 }
 1759 
 1760 void
 1761 pps_capture(struct pps_state *pps)
 1762 {
 1763         struct timehands *th;
 1764 
 1765         KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
 1766         th = timehands;
 1767         pps->capgen = atomic_load_acq_int(&th->th_generation);
 1768         pps->capth = th;
 1769 #ifdef FFCLOCK
 1770         pps->capffth = fftimehands;
 1771 #endif
 1772         pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
 1773         atomic_thread_fence_acq();
 1774         if (pps->capgen != th->th_generation)
 1775                 pps->capgen = 0;
 1776 }
 1777 
 1778 void
 1779 pps_event(struct pps_state *pps, int event)
 1780 {
 1781         struct bintime bt;
 1782         struct timespec ts, *tsp, *osp;
 1783         u_int tcount, *pcount;
 1784         int foff;
 1785         pps_seq_t *pseq;
 1786 #ifdef FFCLOCK
 1787         struct timespec *tsp_ffc;
 1788         pps_seq_t *pseq_ffc;
 1789         ffcounter *ffcount;
 1790 #endif
 1791 #ifdef PPS_SYNC
 1792         int fhard;
 1793 #endif
 1794 
 1795         KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
 1796         /* Nothing to do if not currently set to capture this event type. */
 1797         if ((event & pps->ppsparam.mode) == 0)
 1798                 return;
 1799         /* If the timecounter was wound up underneath us, bail out. */
 1800         if (pps->capgen == 0 || pps->capgen !=
 1801             atomic_load_acq_int(&pps->capth->th_generation))
 1802                 return;
 1803 
 1804         /* Things would be easier with arrays. */
 1805         if (event == PPS_CAPTUREASSERT) {
 1806                 tsp = &pps->ppsinfo.assert_timestamp;
 1807                 osp = &pps->ppsparam.assert_offset;
 1808                 foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
 1809 #ifdef PPS_SYNC
 1810                 fhard = pps->kcmode & PPS_CAPTUREASSERT;
 1811 #endif
 1812                 pcount = &pps->ppscount[0];
 1813                 pseq = &pps->ppsinfo.assert_sequence;
 1814 #ifdef FFCLOCK
 1815                 ffcount = &pps->ppsinfo_ffc.assert_ffcount;
 1816                 tsp_ffc = &pps->ppsinfo_ffc.assert_timestamp;
 1817                 pseq_ffc = &pps->ppsinfo_ffc.assert_sequence;
 1818 #endif
 1819         } else {
 1820                 tsp = &pps->ppsinfo.clear_timestamp;
 1821                 osp = &pps->ppsparam.clear_offset;
 1822                 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
 1823 #ifdef PPS_SYNC
 1824                 fhard = pps->kcmode & PPS_CAPTURECLEAR;
 1825 #endif
 1826                 pcount = &pps->ppscount[1];
 1827                 pseq = &pps->ppsinfo.clear_sequence;
 1828 #ifdef FFCLOCK
 1829                 ffcount = &pps->ppsinfo_ffc.clear_ffcount;
 1830                 tsp_ffc = &pps->ppsinfo_ffc.clear_timestamp;
 1831                 pseq_ffc = &pps->ppsinfo_ffc.clear_sequence;
 1832 #endif
 1833         }
 1834 
 1835         /*
 1836          * If the timecounter changed, we cannot compare the count values, so
 1837          * we have to drop the rest of the PPS-stuff until the next event.
 1838          */
 1839         if (pps->ppstc != pps->capth->th_counter) {
 1840                 pps->ppstc = pps->capth->th_counter;
 1841                 *pcount = pps->capcount;
 1842                 pps->ppscount[2] = pps->capcount;
 1843                 return;
 1844         }
 1845 
 1846         /* Convert the count to a timespec. */
 1847         tcount = pps->capcount - pps->capth->th_offset_count;
 1848         tcount &= pps->capth->th_counter->tc_counter_mask;
 1849         bt = pps->capth->th_bintime;
 1850         bintime_addx(&bt, pps->capth->th_scale * tcount);
 1851         bintime2timespec(&bt, &ts);
 1852 
 1853         /* If the timecounter was wound up underneath us, bail out. */
 1854         atomic_thread_fence_acq();
 1855         if (pps->capgen != pps->capth->th_generation)
 1856                 return;
 1857 
 1858         *pcount = pps->capcount;
 1859         (*pseq)++;
 1860         *tsp = ts;
 1861 
 1862         if (foff) {
 1863                 timespecadd(tsp, osp, tsp);
 1864                 if (tsp->tv_nsec < 0) {
 1865                         tsp->tv_nsec += 1000000000;
 1866                         tsp->tv_sec -= 1;
 1867                 }
 1868         }
 1869 
 1870 #ifdef FFCLOCK
 1871         *ffcount = pps->capffth->tick_ffcount + tcount;
 1872         bt = pps->capffth->tick_time;
 1873         ffclock_convert_delta(tcount, pps->capffth->cest.period, &bt);
 1874         bintime_add(&bt, &pps->capffth->tick_time);
 1875         bintime2timespec(&bt, &ts);
 1876         (*pseq_ffc)++;
 1877         *tsp_ffc = ts;
 1878 #endif
 1879 
 1880 #ifdef PPS_SYNC
 1881         if (fhard) {
 1882                 uint64_t scale;
 1883 
 1884                 /*
 1885                  * Feed the NTP PLL/FLL.
 1886                  * The FLL wants to know how many (hardware) nanoseconds
 1887                  * elapsed since the previous event.
 1888                  */
 1889                 tcount = pps->capcount - pps->ppscount[2];
 1890                 pps->ppscount[2] = pps->capcount;
 1891                 tcount &= pps->capth->th_counter->tc_counter_mask;
 1892                 scale = (uint64_t)1 << 63;
 1893                 scale /= pps->capth->th_counter->tc_frequency;
 1894                 scale *= 2;
 1895                 bt.sec = 0;
 1896                 bt.frac = 0;
 1897                 bintime_addx(&bt, scale * tcount);
 1898                 bintime2timespec(&bt, &ts);
 1899                 hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
 1900         }
 1901 #endif
 1902 
 1903         /* Wakeup anyone sleeping in pps_fetch().  */
 1904         wakeup(pps);
 1905 }
 1906 
 1907 /*
 1908  * Timecounters need to be updated every so often to prevent the hardware
 1909  * counter from overflowing.  Updating also recalculates the cached values
 1910  * used by the get*() family of functions, so their precision depends on
 1911  * the update frequency.
 1912  */
 1913 
 1914 static int tc_tick;
 1915 SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0,
 1916     "Approximate number of hardclock ticks in a millisecond");
 1917 
 1918 void
 1919 tc_ticktock(int cnt)
 1920 {
 1921         static int count;
 1922 
 1923         if (mtx_trylock_spin(&tc_setclock_mtx)) {
 1924                 count += cnt;
 1925                 if (count >= tc_tick) {
 1926                         count = 0;
 1927                         tc_windup(NULL);
 1928                 }
 1929                 mtx_unlock_spin(&tc_setclock_mtx);
 1930         }
 1931 }
 1932 
 1933 static void __inline
 1934 tc_adjprecision(void)
 1935 {
 1936         int t;
 1937 
 1938         if (tc_timepercentage > 0) {
 1939                 t = (99 + tc_timepercentage) / tc_timepercentage;
 1940                 tc_precexp = fls(t + (t >> 1)) - 1;
 1941                 FREQ2BT(hz / tc_tick, &bt_timethreshold);
 1942                 FREQ2BT(hz, &bt_tickthreshold);
 1943                 bintime_shift(&bt_timethreshold, tc_precexp);
 1944                 bintime_shift(&bt_tickthreshold, tc_precexp);
 1945         } else {
 1946                 tc_precexp = 31;
 1947                 bt_timethreshold.sec = INT_MAX;
 1948                 bt_timethreshold.frac = ~(uint64_t)0;
 1949                 bt_tickthreshold = bt_timethreshold;
 1950         }
 1951         sbt_timethreshold = bttosbt(bt_timethreshold);
 1952         sbt_tickthreshold = bttosbt(bt_tickthreshold);
 1953 }
 1954 
 1955 static int
 1956 sysctl_kern_timecounter_adjprecision(SYSCTL_HANDLER_ARGS)
 1957 {
 1958         int error, val;
 1959 
 1960         val = tc_timepercentage;
 1961         error = sysctl_handle_int(oidp, &val, 0, req);
 1962         if (error != 0 || req->newptr == NULL)
 1963                 return (error);
 1964         tc_timepercentage = val;
 1965         if (cold)
 1966                 goto done;
 1967         tc_adjprecision();
 1968 done:
 1969         return (0);
 1970 }
 1971 
 1972 /* Set up the requested number of timehands. */
 1973 static void
 1974 inittimehands(void *dummy)
 1975 {
 1976         struct timehands *thp;
 1977         int i;
 1978 
 1979         TUNABLE_INT_FETCH("kern.timecounter.timehands_count",
 1980             &timehands_count);
 1981         if (timehands_count < 1)
 1982                 timehands_count = 1;
 1983         if (timehands_count > nitems(ths))
 1984                 timehands_count = nitems(ths);
 1985         for (i = 1, thp = &ths[0]; i < timehands_count;  thp = &ths[i++])
 1986                 thp->th_next = &ths[i];
 1987         thp->th_next = &ths[0];
 1988 
 1989         TUNABLE_STR_FETCH("kern.timecounter.hardware", tc_from_tunable,
 1990             sizeof(tc_from_tunable));
 1991 
 1992         mtx_init(&tc_lock, "tc", NULL, MTX_DEF);
 1993 }
 1994 SYSINIT(timehands, SI_SUB_TUNABLES, SI_ORDER_ANY, inittimehands, NULL);
 1995 
 1996 static void
 1997 inittimecounter(void *dummy)
 1998 {
 1999         u_int p;
 2000         int tick_rate;
 2001 
 2002         /*
 2003          * Set the initial timeout to
 2004          * max(1, <approx. number of hardclock ticks in a millisecond>).
 2005          * People should probably not use the sysctl to set the timeout
 2006          * to smaller than its initial value, since that value is the
 2007          * smallest reasonable one.  If they want better timestamps they
 2008          * should use the non-"get"* functions.
 2009          */
 2010         if (hz > 1000)
 2011                 tc_tick = (hz + 500) / 1000;
 2012         else
 2013                 tc_tick = 1;
 2014         tc_adjprecision();
 2015         FREQ2BT(hz, &tick_bt);
 2016         tick_sbt = bttosbt(tick_bt);
 2017         tick_rate = hz / tc_tick;
 2018         FREQ2BT(tick_rate, &tc_tick_bt);
 2019         tc_tick_sbt = bttosbt(tc_tick_bt);
 2020         p = (tc_tick * 1000000) / hz;
 2021         printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
 2022 
 2023 #ifdef FFCLOCK
 2024         ffclock_init();
 2025 #endif
 2026 
 2027         /* warm up new timecounter (again) and get rolling. */
 2028         (void)timecounter->tc_get_timecount(timecounter);
 2029         mtx_lock_spin(&tc_setclock_mtx);
 2030         tc_windup(NULL);
 2031         mtx_unlock_spin(&tc_setclock_mtx);
 2032 }
 2033 
 2034 SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL);
 2035 
 2036 /* Cpu tick handling -------------------------------------------------*/
 2037 
 2038 static bool cpu_tick_variable;
 2039 static uint64_t cpu_tick_frequency;
 2040 
 2041 DPCPU_DEFINE_STATIC(uint64_t, tc_cpu_ticks_base);
 2042 DPCPU_DEFINE_STATIC(unsigned, tc_cpu_ticks_last);
 2043 
 2044 static uint64_t
 2045 tc_cpu_ticks(void)
 2046 {
 2047         struct timecounter *tc;
 2048         uint64_t res, *base;
 2049         unsigned u, *last;
 2050 
 2051         critical_enter();
 2052         base = DPCPU_PTR(tc_cpu_ticks_base);
 2053         last = DPCPU_PTR(tc_cpu_ticks_last);
 2054         tc = timehands->th_counter;
 2055         u = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
 2056         if (u < *last)
 2057                 *base += (uint64_t)tc->tc_counter_mask + 1;
 2058         *last = u;
 2059         res = u + *base;
 2060         critical_exit();
 2061         return (res);
 2062 }
 2063 
 2064 void
 2065 cpu_tick_calibration(void)
 2066 {
 2067         static time_t last_calib;
 2068 
 2069         if (time_uptime != last_calib && !(time_uptime & 0xf)) {
 2070                 cpu_tick_calibrate(0);
 2071                 last_calib = time_uptime;
 2072         }
 2073 }
 2074 
 2075 /*
 2076  * This function gets called every 16 seconds on only one designated
 2077  * CPU in the system from hardclock() via cpu_tick_calibration()().
 2078  *
 2079  * Whenever the real time clock is stepped we get called with reset=1
 2080  * to make sure we handle suspend/resume and similar events correctly.
 2081  */
 2082 
 2083 static void
 2084 cpu_tick_calibrate(int reset)
 2085 {
 2086         static uint64_t c_last;
 2087         uint64_t c_this, c_delta;
 2088         static struct bintime  t_last;
 2089         struct bintime t_this, t_delta;
 2090         uint32_t divi;
 2091 
 2092         if (reset) {
 2093                 /* The clock was stepped, abort & reset */
 2094                 t_last.sec = 0;
 2095                 return;
 2096         }
 2097 
 2098         /* we don't calibrate fixed rate cputicks */
 2099         if (!cpu_tick_variable)
 2100                 return;
 2101 
 2102         getbinuptime(&t_this);
 2103         c_this = cpu_ticks();
 2104         if (t_last.sec != 0) {
 2105                 c_delta = c_this - c_last;
 2106                 t_delta = t_this;
 2107                 bintime_sub(&t_delta, &t_last);
 2108                 /*
 2109                  * Headroom:
 2110                  *      2^(64-20) / 16[s] =
 2111                  *      2^(44) / 16[s] =
 2112                  *      17.592.186.044.416 / 16 =
 2113                  *      1.099.511.627.776 [Hz]
 2114                  */
 2115                 divi = t_delta.sec << 20;
 2116                 divi |= t_delta.frac >> (64 - 20);
 2117                 c_delta <<= 20;
 2118                 c_delta /= divi;
 2119                 if (c_delta > cpu_tick_frequency) {
 2120                         if (0 && bootverbose)
 2121                                 printf("cpu_tick increased to %ju Hz\n",
 2122                                     c_delta);
 2123                         cpu_tick_frequency = c_delta;
 2124                 }
 2125         }
 2126         c_last = c_this;
 2127         t_last = t_this;
 2128 }
 2129 
 2130 void
 2131 set_cputicker(cpu_tick_f *func, uint64_t freq, bool isvariable)
 2132 {
 2133 
 2134         if (func == NULL) {
 2135                 cpu_ticks = tc_cpu_ticks;
 2136         } else {
 2137                 cpu_tick_frequency = freq;
 2138                 cpu_tick_variable = isvariable;
 2139                 cpu_ticks = func;
 2140         }
 2141 }
 2142 
 2143 uint64_t
 2144 cpu_tickrate(void)
 2145 {
 2146 
 2147         if (cpu_ticks == tc_cpu_ticks) 
 2148                 return (tc_getfrequency());
 2149         return (cpu_tick_frequency);
 2150 }
 2151 
 2152 /*
 2153  * We need to be slightly careful converting cputicks to microseconds.
 2154  * There is plenty of margin in 64 bits of microseconds (half a million
 2155  * years) and in 64 bits at 4 GHz (146 years), but if we do a multiply
 2156  * before divide conversion (to retain precision) we find that the
 2157  * margin shrinks to 1.5 hours (one millionth of 146y).
 2158  */
 2159 
 2160 uint64_t
 2161 cputick2usec(uint64_t tick)
 2162 {
 2163         uint64_t tr;
 2164         tr = cpu_tickrate();
 2165         return ((tick / tr) * 1000000ULL) + ((tick % tr) * 1000000ULL) / tr;
 2166 }
 2167 
 2168 cpu_tick_f      *cpu_ticks = tc_cpu_ticks;
 2169 
 2170 static int vdso_th_enable = 1;
 2171 static int
 2172 sysctl_fast_gettime(SYSCTL_HANDLER_ARGS)
 2173 {
 2174         int old_vdso_th_enable, error;
 2175 
 2176         old_vdso_th_enable = vdso_th_enable;
 2177         error = sysctl_handle_int(oidp, &old_vdso_th_enable, 0, req);
 2178         if (error != 0)
 2179                 return (error);
 2180         vdso_th_enable = old_vdso_th_enable;
 2181         return (0);
 2182 }
 2183 SYSCTL_PROC(_kern_timecounter, OID_AUTO, fast_gettime,
 2184     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE,
 2185     NULL, 0, sysctl_fast_gettime, "I", "Enable fast time of day");
 2186 
 2187 uint32_t
 2188 tc_fill_vdso_timehands(struct vdso_timehands *vdso_th)
 2189 {
 2190         struct timehands *th;
 2191         uint32_t enabled;
 2192 
 2193         th = timehands;
 2194         vdso_th->th_scale = th->th_scale;
 2195         vdso_th->th_offset_count = th->th_offset_count;
 2196         vdso_th->th_counter_mask = th->th_counter->tc_counter_mask;
 2197         vdso_th->th_offset = th->th_offset;
 2198         vdso_th->th_boottime = th->th_boottime;
 2199         if (th->th_counter->tc_fill_vdso_timehands != NULL) {
 2200                 enabled = th->th_counter->tc_fill_vdso_timehands(vdso_th,
 2201                     th->th_counter);
 2202         } else
 2203                 enabled = 0;
 2204         if (!vdso_th_enable)
 2205                 enabled = 0;
 2206         return (enabled);
 2207 }
 2208 
 2209 #ifdef COMPAT_FREEBSD32
 2210 uint32_t
 2211 tc_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32)
 2212 {
 2213         struct timehands *th;
 2214         uint32_t enabled;
 2215 
 2216         th = timehands;
 2217         *(uint64_t *)&vdso_th32->th_scale[0] = th->th_scale;
 2218         vdso_th32->th_offset_count = th->th_offset_count;
 2219         vdso_th32->th_counter_mask = th->th_counter->tc_counter_mask;
 2220         vdso_th32->th_offset.sec = th->th_offset.sec;
 2221         *(uint64_t *)&vdso_th32->th_offset.frac[0] = th->th_offset.frac;
 2222         vdso_th32->th_boottime.sec = th->th_boottime.sec;
 2223         *(uint64_t *)&vdso_th32->th_boottime.frac[0] = th->th_boottime.frac;
 2224         if (th->th_counter->tc_fill_vdso_timehands32 != NULL) {
 2225                 enabled = th->th_counter->tc_fill_vdso_timehands32(vdso_th32,
 2226                     th->th_counter);
 2227         } else
 2228                 enabled = 0;
 2229         if (!vdso_th_enable)
 2230                 enabled = 0;
 2231         return (enabled);
 2232 }
 2233 #endif
 2234 
 2235 #include "opt_ddb.h"
 2236 #ifdef DDB
 2237 #include <ddb/ddb.h>
 2238 
 2239 DB_SHOW_COMMAND(timecounter, db_show_timecounter)
 2240 {
 2241         struct timehands *th;
 2242         struct timecounter *tc;
 2243         u_int val1, val2;
 2244 
 2245         th = timehands;
 2246         tc = th->th_counter;
 2247         val1 = tc->tc_get_timecount(tc);
 2248         __compiler_membar();
 2249         val2 = tc->tc_get_timecount(tc);
 2250 
 2251         db_printf("timecounter %p %s\n", tc, tc->tc_name);
 2252         db_printf("  mask %#x freq %ju qual %d flags %#x priv %p\n",
 2253             tc->tc_counter_mask, (uintmax_t)tc->tc_frequency, tc->tc_quality,
 2254             tc->tc_flags, tc->tc_priv);
 2255         db_printf("  val %#x %#x\n", val1, val2);
 2256         db_printf("timehands adj %#jx scale %#jx ldelta %d off_cnt %d gen %d\n",
 2257             (uintmax_t)th->th_adjustment, (uintmax_t)th->th_scale,
 2258             th->th_large_delta, th->th_offset_count, th->th_generation);
 2259         db_printf("  offset %jd %jd boottime %jd %jd\n",
 2260             (intmax_t)th->th_offset.sec, (uintmax_t)th->th_offset.frac,
 2261             (intmax_t)th->th_boottime.sec, (uintmax_t)th->th_boottime.frac);
 2262 }
 2263 #endif

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