[apple/xnu.git] / osfmk / kern / clock.c

/*
 * Copyright (c) 2000-2008 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/*
 */
/*-
 * Copyright (c) 1982, 1986, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)time.h      8.5 (Berkeley) 5/4/95
 * $FreeBSD$
 */

#include <mach/mach_types.h>

#include <kern/spl.h>
#include <kern/sched_prim.h>
#include <kern/thread.h>
#include <kern/clock.h>
#include <kern/host_notify.h>
#include <kern/thread_call.h>
#include <libkern/OSAtomic.h>

#include <IOKit/IOPlatformExpert.h>

#include <machine/commpage.h>
#include <machine/config.h>
#include <machine/machine_routines.h>

#include <mach/mach_traps.h>
#include <mach/mach_time.h>

#include <sys/kdebug.h>
#include <sys/timex.h>
#include <kern/arithmetic_128.h>

uint32_t        hz_tick_interval = 1;


decl_simple_lock_data(,clock_lock)
lck_grp_attr_t * settime_lock_grp_attr;
lck_grp_t * settime_lock_grp;
lck_attr_t * settime_lock_attr;
lck_mtx_t settime_lock;

#define clock_lock()    \
        simple_lock(&clock_lock)

#define clock_unlock()  \
        simple_unlock(&clock_lock)

#define clock_lock_init()       \
        simple_lock_init(&clock_lock, 0)

#ifdef kdp_simple_lock_is_acquired
boolean_t kdp_clock_is_locked()
{
        return kdp_simple_lock_is_acquired(&clock_lock);
}
#endif

struct bintime {
        time_t  sec;
        uint64_t frac;
};

static __inline void
bintime_addx(struct bintime *_bt, uint64_t _x)
{
        uint64_t _u;

        _u = _bt->frac;
        _bt->frac += _x;
        if (_u > _bt->frac)
                _bt->sec++;
}

static __inline void
bintime_subx(struct bintime *_bt, uint64_t _x)
{
        uint64_t _u;

        _u = _bt->frac;
        _bt->frac -= _x;
        if (_u < _bt->frac)
                _bt->sec--;
}

static __inline void
bintime_addns(struct bintime *bt, uint64_t ns)
{
        bt->sec += ns/ (uint64_t)NSEC_PER_SEC;
        ns = ns % (uint64_t)NSEC_PER_SEC;
        if (ns) {
                /* 18446744073 = int(2^64 / NSEC_PER_SEC) */
                ns = ns * (uint64_t)18446744073LL;
                bintime_addx(bt, ns);
        }
}

static __inline void
bintime_subns(struct bintime *bt, uint64_t ns)
{
        bt->sec -= ns/ (uint64_t)NSEC_PER_SEC;
        ns = ns % (uint64_t)NSEC_PER_SEC;
        if (ns) {
                /* 18446744073 = int(2^64 / NSEC_PER_SEC) */
                ns = ns * (uint64_t)18446744073LL;
                bintime_subx(bt, ns);
        }
}

static __inline void
bintime_addxns(struct bintime *bt, uint64_t a, int64_t xns)
{
        uint64_t uxns = (xns > 0)?(uint64_t )xns:(uint64_t)-xns;
        uint64_t ns = multi_overflow(a, uxns);
        if (xns > 0) {
                if (ns)
                        bintime_addns(bt, ns);
                ns = (a * uxns) / (uint64_t)NSEC_PER_SEC;
                bintime_addx(bt, ns);
        }
        else{
                if (ns)
                        bintime_subns(bt, ns);
                ns = (a * uxns) / (uint64_t)NSEC_PER_SEC;
                bintime_subx(bt,ns);
        }
}


static __inline void
bintime_add(struct bintime *_bt, const struct bintime *_bt2)
{
        uint64_t _u;

        _u = _bt->frac;
        _bt->frac += _bt2->frac;
        if (_u > _bt->frac)
                _bt->sec++;
        _bt->sec += _bt2->sec;
}

static __inline void
bintime_sub(struct bintime *_bt, const struct bintime *_bt2)
{
        uint64_t _u;

        _u = _bt->frac;
        _bt->frac -= _bt2->frac;
        if (_u < _bt->frac)
                _bt->sec--;
        _bt->sec -= _bt2->sec;
}

static __inline void
clock2bintime(const clock_sec_t *secs, const clock_usec_t *microsecs, struct bintime *_bt)
{

        _bt->sec = *secs;
        /* 18446744073709 = int(2^64 / 1000000) */
        _bt->frac = *microsecs * (uint64_t)18446744073709LL;
}

static __inline void
bintime2usclock(const struct bintime *_bt, clock_sec_t *secs, clock_usec_t *microsecs)
{

        *secs = _bt->sec;
        *microsecs = ((uint64_t)USEC_PER_SEC * (uint32_t)(_bt->frac >> 32)) >> 32;
}

static __inline void
bintime2nsclock(const struct bintime *_bt, clock_sec_t *secs, clock_usec_t *nanosecs)
{

        *secs = _bt->sec;
        *nanosecs = ((uint64_t)NSEC_PER_SEC * (uint32_t)(_bt->frac >> 32)) >> 32;
}

static __inline void
bintime2absolutetime(const struct bintime *_bt, uint64_t *abs)
{
        uint64_t nsec;
        nsec = (uint64_t) _bt->sec * (uint64_t)NSEC_PER_SEC + (((uint64_t)NSEC_PER_SEC * (uint32_t)(_bt->frac >> 32)) >> 32);
        nanoseconds_to_absolutetime(nsec, abs);
}
/*
 *      Time of day (calendar) variables.
 *
 *      Algorithm:
 *
 *      TOD <- bintime + delta*scale
 *
 *      where :
 *      bintime is a cumulative offset that includes bootime and scaled time elapsed betweed bootime and last scale update.
 *      delta is ticks elapsed since last scale update.
 *      scale is computed according to an adjustment provided by ntp_kern.
 */
static struct clock_calend {
        uint64_t                s_scale_ns; /* scale to apply for each second elapsed, it converts in ns */
        int64_t                 s_adj_nsx; /* additional adj to apply for each second elapsed, it is expressed in 64 bit frac of ns */
        uint64_t                tick_scale_x; /* scale to apply for each tick elapsed, it converts in 64 bit frac of s */
        uint64_t                offset_count; /* abs time from which apply current scales */
        struct bintime          offset; /* cumulative offset expressed in (sec, 64 bits frac of a second) */
        struct bintime          bintime; /* cumulative offset (it includes bootime) expressed in (sec, 64 bits frac of a second) */
        struct bintime          boottime; /* boot time expressed in (sec, 64 bits frac of a second) */
        struct bintime          basesleep;
} clock_calend;

static uint64_t ticks_per_sec; /* ticks in a second (expressed in abs time) */

#if DEVELOPMENT || DEBUG
clock_sec_t last_utc_sec = 0;
clock_usec_t last_utc_usec = 0;
clock_sec_t max_utc_sec = 0;
clock_sec_t last_sys_sec = 0;
clock_usec_t last_sys_usec = 0;
#endif

#if     CONFIG_DTRACE

/*
 *      Unlocked calendar flipflop; this is used to track a clock_calend such
 *      that we can safely access a snapshot of a valid  clock_calend structure
 *      without needing to take any locks to do it.
 *
 *      The trick is to use a generation count and set the low bit when it is
 *      being updated/read; by doing this, we guarantee, through use of the
 *      hw_atomic functions, that the generation is incremented when the bit
 *      is cleared atomically (by using a 1 bit add).
 */
static struct unlocked_clock_calend {
        struct clock_calend     calend;         /* copy of calendar */
        uint32_t                gen;            /* generation count */
} flipflop[ 2];

static void clock_track_calend_nowait(void);

#endif

void _clock_delay_until_deadline(uint64_t interval, uint64_t deadline);
void _clock_delay_until_deadline_with_leeway(uint64_t interval, uint64_t deadline, uint64_t leeway);

/* Boottime variables*/
static uint64_t clock_boottime;
static uint32_t clock_boottime_usec;

#define TIME_ADD(rsecs, secs, rfrac, frac, unit)        \
MACRO_BEGIN                                                                                     \
        if (((rfrac) += (frac)) >= (unit)) {                    \
                (rfrac) -= (unit);                                                      \
                (rsecs) += 1;                                                           \
        }                                                                                               \
        (rsecs) += (secs);                                                              \
MACRO_END

#define TIME_SUB(rsecs, secs, rfrac, frac, unit)        \
MACRO_BEGIN                                                                                     \
        if ((int)((rfrac) -= (frac)) < 0) {                             \
                (rfrac) += (unit);                                                      \
                (rsecs) -= 1;                                                           \
        }                                                                                               \
        (rsecs) -= (secs);                                                              \
MACRO_END

/*
 *      clock_config:
 *
 *      Called once at boot to configure the clock subsystem.
 */
void
clock_config(void)
{

        clock_lock_init();

        settime_lock_grp_attr = lck_grp_attr_alloc_init();
        settime_lock_grp = lck_grp_alloc_init("settime grp", settime_lock_grp_attr);
        settime_lock_attr = lck_attr_alloc_init();
        lck_mtx_init(&settime_lock, settime_lock_grp, settime_lock_attr);

        clock_oldconfig();

        ntp_init();

        nanoseconds_to_absolutetime((uint64_t)NSEC_PER_SEC, &ticks_per_sec);
}

/*
 *      clock_init:
 *
 *      Called on a processor each time started.
 */
void
clock_init(void)
{
        clock_oldinit();
}

/*
 *      clock_timebase_init:
 *
 *      Called by machine dependent code
 *      to initialize areas dependent on the
 *      timebase value.  May be called multiple
 *      times during start up.
 */
void
clock_timebase_init(void)
{
        uint64_t        abstime;

        nanoseconds_to_absolutetime(NSEC_PER_SEC / 100, &abstime);
        hz_tick_interval = (uint32_t)abstime;

        sched_timebase_init();
}

/*
 *      mach_timebase_info_trap:
 *
 *      User trap returns timebase constant.
 */
kern_return_t
mach_timebase_info_trap(
        struct mach_timebase_info_trap_args *args)
{
        mach_vm_address_t                       out_info_addr = args->info;
        mach_timebase_info_data_t       info;

        clock_timebase_info(&info);

        copyout((void *)&info, out_info_addr, sizeof (info));

        return (KERN_SUCCESS);
}

/*
 *      Calendar routines.
 */

/*
 *      clock_get_calendar_microtime:
 *
 *      Returns the current calendar value,
 *      microseconds as the fraction.
 */
void
clock_get_calendar_microtime(
        clock_sec_t             *secs,
        clock_usec_t            *microsecs)
{
        clock_get_calendar_absolute_and_microtime(secs, microsecs, NULL);
}

/*
 * get_scale_factors_from_adj:
 *
 * computes scale factors from the value given in adjustment.
 *
 * Part of the code has been taken from tc_windup of FreeBSD
 * written by Poul-Henning Kamp <phk@FreeBSD.ORG>, Julien Ridoux and
 * Konstantin Belousov.
 * https://github.com/freebsd/freebsd/blob/master/sys/kern/kern_tc.c
 */
static void
get_scale_factors_from_adj(int64_t adjustment, uint64_t* tick_scale_x, uint64_t* s_scale_ns, int64_t* s_adj_nsx)
{
        uint64_t scale;
        int64_t nano, frac;

        /*-
         * Calculating the scaling factor.  We want the number of 1/2^64
         * fractions of a second per period of the hardware counter, taking
         * into account the th_adjustment factor which the NTP PLL/adjtime(2)
         * processing provides us with.
         *
         * The th_adjustment is nanoseconds per second with 32 bit binary
         * fraction and we want 64 bit binary fraction of second:
         *
         *       x = a * 2^32 / 10^9 = a * 4.294967296
         *
         * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
         * we can only multiply by about 850 without overflowing, that
         * leaves no suitably precise fractions for multiply before divide.
         *
         * Divide before multiply with a fraction of 2199/512 results in a
         * systematic undercompensation of 10PPM of th_adjustment.  On a
         * 5000PPM adjustment this is a 0.05PPM error.  This is acceptable.
         *
         * We happily sacrifice the lowest of the 64 bits of our result
         * to the goddess of code clarity.
         *
         */
        scale = (uint64_t)1 << 63;
        scale += (adjustment / 1024) * 2199;
        scale /= ticks_per_sec;
        *tick_scale_x = scale * 2;

        /*
         * hi part of adj
         * it contains ns (without fraction) to add to the next sec.
         * Get ns scale factor for the next sec.
         */
        nano = (adjustment > 0)? adjustment >> 32 : -((-adjustment) >> 32);
        scale = (uint64_t) NSEC_PER_SEC;
        scale += nano;
        *s_scale_ns = scale;

        /*
         * lo part of adj
         * it contains 32 bit frac of ns to add to the next sec.
         * Keep it as additional adjustment for the next sec.
         */
        frac = (adjustment > 0)? ((uint32_t) adjustment) : -((uint32_t) (-adjustment));
        *s_adj_nsx = (frac>0)? frac << 32 : -( (-frac) << 32);

        return;
}

/*
 * scale_delta:
 *
 * returns a bintime struct representing delta scaled accordingly to the
 * scale factors provided to this function.
 */
static struct bintime
scale_delta(uint64_t delta, uint64_t tick_scale_x, uint64_t s_scale_ns, int64_t s_adj_nsx)
{
        uint64_t sec, new_ns, over;
        struct bintime bt;

        bt.sec = 0;
        bt.frac = 0;

        /*
         * If more than one second is elapsed,
         * scale fully elapsed seconds using scale factors for seconds.
         * s_scale_ns -> scales sec to ns.
         * s_adj_nsx -> additional adj expressed in 64 bit frac of ns to apply to each sec.
         */
        if (delta > ticks_per_sec) {
                sec = (delta/ticks_per_sec);
                new_ns = sec * s_scale_ns;
                bintime_addns(&bt, new_ns);
                if (s_adj_nsx) {
                        if (sec == 1) {
                                /* shortcut, no overflow can occur */
                                if (s_adj_nsx > 0)
                                        bintime_addx(&bt, (uint64_t)s_adj_nsx/ (uint64_t)NSEC_PER_SEC);
                                else
                                        bintime_subx(&bt, (uint64_t)-s_adj_nsx/ (uint64_t)NSEC_PER_SEC);
                        }
                        else{
                                /*
                                 * s_adj_nsx is 64 bit frac of ns.
                                 * sec*s_adj_nsx might overflow in int64_t.
                                 * use bintime_addxns to not lose overflowed ns.
                                 */
                                bintime_addxns(&bt, sec, s_adj_nsx);
                        }
                }
                delta = (delta % ticks_per_sec);
        }

        over = multi_overflow(tick_scale_x, delta);
        if(over){
                bt.sec += over;
        }

        /*
         * scale elapsed ticks using the scale factor for ticks.
         */
        bintime_addx(&bt, delta * tick_scale_x);

        return bt;
}

/*
 * get_scaled_time:
 *
 * returns the scaled time of the time elapsed from the last time
 * scale factors were updated to now.
 */
static struct bintime
get_scaled_time(uint64_t now)
{
        uint64_t delta;

        /*
         * Compute ticks elapsed since last scale update.
         * This time will be scaled according to the value given by ntp kern.
         */
        delta = now - clock_calend.offset_count;

        return scale_delta(delta, clock_calend.tick_scale_x, clock_calend.s_scale_ns, clock_calend.s_adj_nsx);
}

static void
clock_get_calendar_absolute_and_microtime_locked(
        clock_sec_t             *secs,
        clock_usec_t            *microsecs,
        uint64_t                *abstime)
{
        uint64_t now;
        struct bintime bt;

        now  = mach_absolute_time();
        if (abstime)
                *abstime = now;

        bt = get_scaled_time(now);
        bintime_add(&bt, &clock_calend.bintime);
        bintime2usclock(&bt, secs, microsecs);
}

static void
clock_get_calendar_absolute_and_nanotime_locked(
        clock_sec_t             *secs,
        clock_usec_t            *nanosecs,
        uint64_t                *abstime)
{
        uint64_t now;
        struct bintime bt;

        now  = mach_absolute_time();
        if (abstime)
                *abstime = now;

        bt = get_scaled_time(now);
        bintime_add(&bt, &clock_calend.bintime);
        bintime2nsclock(&bt, secs, nanosecs);
}

/*
 *      clock_get_calendar_absolute_and_microtime:
 *
 *      Returns the current calendar value,
 *      microseconds as the fraction. Also
 *      returns mach_absolute_time if abstime
 *      is not NULL.
 */
void
clock_get_calendar_absolute_and_microtime(
        clock_sec_t             *secs,
        clock_usec_t            *microsecs,
        uint64_t                *abstime)
{
        spl_t                   s;

        s = splclock();
        clock_lock();

        clock_get_calendar_absolute_and_microtime_locked(secs, microsecs, abstime);

        clock_unlock();
        splx(s);
}

/*
 *      clock_get_calendar_nanotime:
 *
 *      Returns the current calendar value,
 *      nanoseconds as the fraction.
 *
 *      Since we do not have an interface to
 *      set the calendar with resolution greater
 *      than a microsecond, we honor that here.
 */
void
clock_get_calendar_nanotime(
        clock_sec_t             *secs,
        clock_nsec_t            *nanosecs)
{
        spl_t                   s;

        s = splclock();
        clock_lock();

        clock_get_calendar_absolute_and_nanotime_locked(secs, nanosecs, NULL);

        clock_unlock();
        splx(s);
}

/*
 *      clock_gettimeofday:
 *
 *      Kernel interface for commpage implementation of
 *      gettimeofday() syscall.
 *
 *      Returns the current calendar value, and updates the
 *      commpage info as appropriate.  Because most calls to
 *      gettimeofday() are handled in user mode by the commpage,
 *      this routine should be used infrequently.
 */
void
clock_gettimeofday(
        clock_sec_t     *secs,
        clock_usec_t    *microsecs)
{
        clock_gettimeofday_and_absolute_time(secs, microsecs, NULL);
}

void
clock_gettimeofday_and_absolute_time(
        clock_sec_t     *secs,
        clock_usec_t    *microsecs,
        uint64_t        *mach_time)
{
        uint64_t                now;
        spl_t                   s;
        struct bintime  bt;

        s = splclock();
        clock_lock();

        now = mach_absolute_time();
        bt = get_scaled_time(now);
        bintime_add(&bt, &clock_calend.bintime);
        bintime2usclock(&bt, secs, microsecs);

        clock_gettimeofday_set_commpage(now, bt.sec, bt.frac, clock_calend.tick_scale_x, ticks_per_sec);

        clock_unlock();
        splx(s);

        if (mach_time) {
                *mach_time = now;
        }
}

/*
 *      clock_set_calendar_microtime:
 *
 *      Sets the current calendar value by
 *      recalculating the epoch and offset
 *      from the system clock.
 *
 *      Also adjusts the boottime to keep the
 *      value consistent, writes the new
 *      calendar value to the platform clock,
 *      and sends calendar change notifications.
 */
void
clock_set_calendar_microtime(
        clock_sec_t             secs,
        clock_usec_t            microsecs)
{
        uint64_t                absolutesys;
        clock_sec_t             newsecs;
        clock_sec_t             oldsecs;
        clock_usec_t            newmicrosecs;
        clock_usec_t            oldmicrosecs;
        uint64_t                commpage_value;
        spl_t                   s;
        struct bintime          bt;
        clock_sec_t             deltasecs;
        clock_usec_t            deltamicrosecs;

        newsecs = secs;
        newmicrosecs = microsecs;

        /*
         * settime_lock mtx is used to avoid that racing settimeofdays update the wall clock and
         * the platform clock concurrently.
         *
         * clock_lock cannot be used for this race because it is acquired from interrupt context
         * and it needs interrupts disabled while instead updating the platform clock needs to be
         * called with interrupts enabled.
         */
        lck_mtx_lock(&settime_lock);

        s = splclock();
        clock_lock();

        commpage_disable_timestamp();

        /*
         *      Adjust the boottime based on the delta.
         */
        clock_get_calendar_absolute_and_microtime_locked(&oldsecs, &oldmicrosecs, &absolutesys);

        if (oldsecs < secs || (oldsecs == secs && oldmicrosecs < microsecs)) {
                // moving forwards
                deltasecs = secs;
                deltamicrosecs = microsecs;

                TIME_SUB(deltasecs, oldsecs, deltamicrosecs, oldmicrosecs, USEC_PER_SEC);
                TIME_ADD(clock_boottime, deltasecs, clock_boottime_usec, deltamicrosecs, USEC_PER_SEC);

                clock2bintime(&deltasecs, &deltamicrosecs, &bt);
                bintime_add(&clock_calend.boottime, &bt);
                bintime_add(&clock_calend.basesleep, &bt);

        } else {
                // moving backwards
                deltasecs = oldsecs;
                deltamicrosecs = oldmicrosecs;

                TIME_SUB(deltasecs, secs, deltamicrosecs, microsecs, USEC_PER_SEC);
                TIME_SUB(clock_boottime, deltasecs, clock_boottime_usec, deltamicrosecs, USEC_PER_SEC);

                clock2bintime(&deltasecs, &deltamicrosecs, &bt);
                bintime_sub(&clock_calend.boottime, &bt);
                bintime_sub(&clock_calend.basesleep, &bt);
        }

        clock_calend.bintime = clock_calend.boottime;
        bintime_add(&clock_calend.bintime, &clock_calend.offset);

        clock2bintime((clock_sec_t *) &secs, (clock_usec_t *) &microsecs, &bt);

        clock_gettimeofday_set_commpage(absolutesys, bt.sec, bt.frac, clock_calend.tick_scale_x, ticks_per_sec);

        commpage_value = clock_boottime * USEC_PER_SEC + clock_boottime_usec;

        clock_unlock();
        splx(s);

        /*
         *      Set the new value for the platform clock.
         *      This call might block, so interrupts must be enabled.
         */
        PESetUTCTimeOfDay(newsecs, newmicrosecs);

        commpage_update_boottime(commpage_value);

        /*
         *      Send host notifications.
         */
        host_notify_calendar_change();
        host_notify_calendar_set();

#if CONFIG_DTRACE
        clock_track_calend_nowait();
#endif

        lck_mtx_unlock(&settime_lock);
}

uint64_t mach_absolutetime_asleep = 0;
uint64_t mach_absolutetime_last_sleep = 0;

void
clock_get_calendar_uptime(clock_sec_t *secs)
{
        uint64_t now;
        spl_t s;
        struct bintime bt;

        s = splclock();
        clock_lock();

        now = mach_absolute_time();

        bt = get_scaled_time(now);
        bintime_add(&bt, &clock_calend.offset);

        *secs = bt.sec;

        clock_unlock();
        splx(s);
}


/*
 * clock_update_calendar:
 *
 * called by ntp timer to update scale factors.
 */
void
clock_update_calendar(void)
{

        uint64_t now, delta;
        struct bintime bt;
        spl_t s;
        int64_t adjustment;

        s = splclock();
        clock_lock();

        now  = mach_absolute_time();

        /*
         * scale the time elapsed since the last update and
         * add it to offset.
         */
        bt = get_scaled_time(now);
        bintime_add(&clock_calend.offset, &bt);

        /*
         * update the base from which apply next scale factors.
         */
        delta = now - clock_calend.offset_count;
        clock_calend.offset_count += delta;

        clock_calend.bintime = clock_calend.offset;
        bintime_add(&clock_calend.bintime, &clock_calend.boottime);

        /*
         * recompute next adjustment.
         */
        ntp_update_second(&adjustment, clock_calend.bintime.sec);

        /*
         * recomputing scale factors.
         */
        get_scale_factors_from_adj(adjustment, &clock_calend.tick_scale_x, &clock_calend.s_scale_ns, &clock_calend.s_adj_nsx);

        clock_gettimeofday_set_commpage(now, clock_calend.bintime.sec, clock_calend.bintime.frac, clock_calend.tick_scale_x, ticks_per_sec);

        clock_unlock();
        splx(s);
}

/*
 *      clock_initialize_calendar:
 *
 *      Set the calendar and related clocks
 *      from the platform clock at boot or
 *      wake event.
 *
 *      Also sends host notifications.
 */

void
clock_initialize_calendar(void)
{
        clock_sec_t             sys;  // sleepless time since boot in seconds
        clock_sec_t             secs; // Current UTC time
        clock_sec_t             utc_offset_secs; // Difference in current UTC time and sleepless time since boot
        clock_usec_t            microsys;  
        clock_usec_t            microsecs; 
        clock_usec_t            utc_offset_microsecs; 
        spl_t                   s;
        struct bintime          bt;

        PEGetUTCTimeOfDay(&secs, &microsecs);

        s = splclock();
        clock_lock();

        commpage_disable_timestamp();

        /*
         *      Calculate the new calendar epoch based on
         *      the platform clock and the system clock.
         */
        clock_get_system_microtime(&sys, &microsys);
        utc_offset_secs = secs;
        utc_offset_microsecs = microsecs;

#if DEVELOPMENT || DEBUG
        last_utc_sec = secs;
        last_utc_usec = microsecs;
        last_sys_sec = sys;
        last_sys_usec = microsys;
        if (secs > max_utc_sec)
                max_utc_sec = secs;
#endif

        /*
         * We normally expect the UTC clock to be always-on and produce
         * greater readings than the tick counter.  There may be corner cases
         * due to differing clock resolutions (UTC clock is likely lower) and
         * and errors reading the UTC clock (some implementations return 0
         * on error) in which that doesn't hold true.  Bring the UTC measurements
         * in-line with the tick counter measurements as a best effort in that case.
         */
        if ((sys > secs) || ((sys == secs) && (microsys > microsecs))) {
                secs = utc_offset_secs = sys;
                microsecs = utc_offset_microsecs = microsys;
        }

        // This macro stores the subtraction result in utc_offset_secs and utc_offset_microsecs
        TIME_SUB(utc_offset_secs, sys, utc_offset_microsecs, microsys, USEC_PER_SEC);

        clock2bintime(&utc_offset_secs, &utc_offset_microsecs, &bt);

        /*
         *      Initialize the boot time based on the platform clock.
         */
        clock_boottime = secs;
        clock_boottime_usec = microsecs;
        commpage_update_boottime(clock_boottime * USEC_PER_SEC + clock_boottime_usec);

        nanoseconds_to_absolutetime((uint64_t)NSEC_PER_SEC, &ticks_per_sec);
        clock_calend.boottime = bt;
        clock_calend.bintime = bt;
        clock_calend.offset.sec = 0;
        clock_calend.offset.frac = 0;

        clock_calend.tick_scale_x = (uint64_t)1 << 63;
        clock_calend.tick_scale_x /= ticks_per_sec;
        clock_calend.tick_scale_x *= 2;

        clock_calend.s_scale_ns = NSEC_PER_SEC;
        clock_calend.s_adj_nsx = 0;

        clock_calend.basesleep = bt;

        commpage_update_mach_continuous_time(mach_absolutetime_asleep);

        clock_unlock();
        splx(s);

        /*
         *      Send host notifications.
         */
        host_notify_calendar_change();
        
#if CONFIG_DTRACE
        clock_track_calend_nowait();
#endif
}


void
clock_wakeup_calendar(void)
{
        clock_sec_t             sys;  // sleepless time since boot in seconds
        clock_sec_t             secs; // Current UTC time
        clock_usec_t            microsys;  
        clock_usec_t            microsecs; 
        spl_t                   s;
        struct bintime          utc_offset_bt, last_sleep_bt;

        PEGetUTCTimeOfDay(&secs, &microsecs);

        s = splclock();
        clock_lock();

        commpage_disable_timestamp();

        /*
         * Calculate the new calendar epoch based on
         * the platform clock and the system clock.
         */
        clock_get_system_microtime(&sys, &microsys);

#if DEVELOPMENT || DEBUG
        last_utc_sec = secs;
        last_utc_usec = microsecs;
        last_sys_sec = sys;
        last_sys_usec = microsys;
        if (secs > max_utc_sec)
                max_utc_sec = secs;
#endif

        /*
         * We normally expect the UTC clock to be always-on and produce
         * greater readings than the tick counter.  There may be corner cases
         * due to differing clock resolutions (UTC clock is likely lower) and
         * errors reading the UTC clock (some implementations return 0 on error)
         * in which that doesn't hold true.  Bring the UTC measurements in-line
         * with the tick counter measurements as a best effort in that case.
         */
        if ((sys > secs) || ((sys == secs) && (microsys > microsecs))) {
                secs = sys;
                microsecs = microsys;
        }

        // This macro stores the subtraction result in secs and microsecs
        TIME_SUB(secs, sys, microsecs, microsys, USEC_PER_SEC);
        clock2bintime(&secs, &microsecs, &utc_offset_bt);

        /*
         * Safety belt: the UTC clock will likely have a lower resolution than the tick counter.
         * It's also possible that the device didn't fully transition to the powered-off state on
         * the most recent sleep, so the tick counter may not have reset or may have only briefly
         * tured off.  In that case it's possible for the difference between the UTC clock and the
         * tick counter to be less than the previously recorded value in clock.calend.basesleep.
         * In that case simply record that we slept for 0 ticks.
         */ 
        if ((utc_offset_bt.sec > clock_calend.basesleep.sec) ||
            ((utc_offset_bt.sec == clock_calend.basesleep.sec) && (utc_offset_bt.frac > clock_calend.basesleep.frac))) {

                last_sleep_bt = utc_offset_bt;
                bintime_sub(&last_sleep_bt, &clock_calend.basesleep);
                clock_calend.basesleep = utc_offset_bt;

                bintime2absolutetime(&last_sleep_bt, &mach_absolutetime_last_sleep);
                mach_absolutetime_asleep += mach_absolutetime_last_sleep;

                bintime_add(&clock_calend.offset, &last_sleep_bt);
                bintime_add(&clock_calend.bintime, &last_sleep_bt);
        } else
                mach_absolutetime_last_sleep = 0;

        KERNEL_DEBUG_CONSTANT(
                  MACHDBG_CODE(DBG_MACH_CLOCK,MACH_EPOCH_CHANGE) | DBG_FUNC_NONE,
                  (uintptr_t) mach_absolutetime_last_sleep,
                  (uintptr_t) mach_absolutetime_asleep,
                  (uintptr_t) (mach_absolutetime_last_sleep >> 32),
                  (uintptr_t) (mach_absolutetime_asleep >> 32),
                  0);

        commpage_update_mach_continuous_time(mach_absolutetime_asleep);
        adjust_cont_time_thread_calls();

        clock_unlock();
        splx(s);

        host_notify_calendar_change();

#if CONFIG_DTRACE
        clock_track_calend_nowait();
#endif
}



/*
 *      clock_get_boottime_nanotime:
 *
 *      Return the boottime, used by sysctl.
 */
void
clock_get_boottime_nanotime(
        clock_sec_t                     *secs,
        clock_nsec_t            *nanosecs)
{
        spl_t   s;

        s = splclock();
        clock_lock();

        *secs = (clock_sec_t)clock_boottime;
        *nanosecs = (clock_nsec_t)clock_boottime_usec * NSEC_PER_USEC;

        clock_unlock();
        splx(s);
}

/*
 *      clock_get_boottime_nanotime:
 *
 *      Return the boottime, used by sysctl.
 */
void
clock_get_boottime_microtime(
        clock_sec_t                     *secs,
        clock_usec_t            *microsecs)
{
        spl_t   s;

        s = splclock();
        clock_lock();

        *secs = (clock_sec_t)clock_boottime;
        *microsecs = (clock_nsec_t)clock_boottime_usec;

        clock_unlock();
        splx(s);
}


/*
 *      Wait / delay routines.
 */
static void
mach_wait_until_continue(
        __unused void   *parameter,
        wait_result_t   wresult)
{
        thread_syscall_return((wresult == THREAD_INTERRUPTED)? KERN_ABORTED: KERN_SUCCESS);
        /*NOTREACHED*/
}

/*
 * mach_wait_until_trap: Suspend execution of calling thread until the specified time has passed
 *
 * Parameters:    args->deadline          Amount of time to wait
 *
 * Returns:        0                      Success
 *                !0                      Not success           
 *
 */
kern_return_t
mach_wait_until_trap(
        struct mach_wait_until_trap_args        *args)
{
        uint64_t                deadline = args->deadline;
        wait_result_t   wresult;

        wresult = assert_wait_deadline_with_leeway((event_t)mach_wait_until_trap, THREAD_ABORTSAFE,
                                                   TIMEOUT_URGENCY_USER_NORMAL, deadline, 0);
        if (wresult == THREAD_WAITING)
                wresult = thread_block(mach_wait_until_continue);

        return ((wresult == THREAD_INTERRUPTED)? KERN_ABORTED: KERN_SUCCESS);
}

void
clock_delay_until(
        uint64_t                deadline)
{
        uint64_t                now = mach_absolute_time();

        if (now >= deadline)
                return;

        _clock_delay_until_deadline(deadline - now, deadline);
}

/*
 * Preserve the original precise interval that the client
 * requested for comparison to the spin threshold.
 */
void
_clock_delay_until_deadline(
        uint64_t                interval,
        uint64_t                deadline)
{
        _clock_delay_until_deadline_with_leeway(interval, deadline, 0);
}

/*
 * Like _clock_delay_until_deadline, but it accepts a
 * leeway value.
 */
void
_clock_delay_until_deadline_with_leeway(
        uint64_t                interval,
        uint64_t                deadline,
        uint64_t                leeway)
{

        if (interval == 0)
                return;

        if (    ml_delay_should_spin(interval)  ||
                        get_preemption_level() != 0                             ||
                        ml_get_interrupts_enabled() == FALSE    ) {
                machine_delay_until(interval, deadline);
        } else {
                /*
                 * For now, assume a leeway request of 0 means the client does not want a leeway
                 * value. We may want to change this interpretation in the future.
                 */

                if (leeway) {
                        assert_wait_deadline_with_leeway((event_t)clock_delay_until, THREAD_UNINT, TIMEOUT_URGENCY_LEEWAY, deadline, leeway);
                } else {
                        assert_wait_deadline((event_t)clock_delay_until, THREAD_UNINT, deadline);
                }

                thread_block(THREAD_CONTINUE_NULL);
        }
}

void
delay_for_interval(
        uint32_t                interval,
        uint32_t                scale_factor)
{
        uint64_t                abstime;

        clock_interval_to_absolutetime_interval(interval, scale_factor, &abstime);

        _clock_delay_until_deadline(abstime, mach_absolute_time() + abstime);
}

void
delay_for_interval_with_leeway(
        uint32_t                interval,
        uint32_t                leeway,
        uint32_t                scale_factor)
{
        uint64_t                abstime_interval;
        uint64_t                abstime_leeway;

        clock_interval_to_absolutetime_interval(interval, scale_factor, &abstime_interval);
        clock_interval_to_absolutetime_interval(leeway, scale_factor, &abstime_leeway);

        _clock_delay_until_deadline_with_leeway(abstime_interval, mach_absolute_time() + abstime_interval, abstime_leeway);
}

void
delay(
        int             usec)
{
        delay_for_interval((usec < 0)? -usec: usec, NSEC_PER_USEC);
}

/*
 *      Miscellaneous routines.
 */
void
clock_interval_to_deadline(
        uint32_t                        interval,
        uint32_t                        scale_factor,
        uint64_t                        *result)
{
        uint64_t        abstime;

        clock_interval_to_absolutetime_interval(interval, scale_factor, &abstime);

        *result = mach_absolute_time() + abstime;
}

void
clock_absolutetime_interval_to_deadline(
        uint64_t                        abstime,
        uint64_t                        *result)
{
        *result = mach_absolute_time() + abstime;
}

void
clock_continuoustime_interval_to_deadline(
        uint64_t                        conttime,
        uint64_t                        *result)
{
        *result = mach_continuous_time() + conttime;
}

void
clock_get_uptime(
        uint64_t        *result)
{
        *result = mach_absolute_time();
}

void
clock_deadline_for_periodic_event(
        uint64_t                        interval,
        uint64_t                        abstime,
        uint64_t                        *deadline)
{
        assert(interval != 0);

        *deadline += interval;

        if (*deadline <= abstime) {
                *deadline = abstime + interval;
                abstime = mach_absolute_time();

                if (*deadline <= abstime)
                        *deadline = abstime + interval;
        }
}

uint64_t
mach_continuous_time(void)
{
        while(1) {      
                uint64_t read1 = mach_absolutetime_asleep;
                uint64_t absolute = mach_absolute_time();
                OSMemoryBarrier();
                uint64_t read2 = mach_absolutetime_asleep;

                if(__builtin_expect(read1 == read2, 1)) {
                        return absolute + read1;
                }
        }
}

uint64_t
mach_continuous_approximate_time(void)
{
        while(1) {
                uint64_t read1 = mach_absolutetime_asleep;
                uint64_t absolute = mach_approximate_time();
                OSMemoryBarrier();
                uint64_t read2 = mach_absolutetime_asleep;

                if(__builtin_expect(read1 == read2, 1)) {
                        return absolute + read1;
                }
        }
}

/*
 * continuoustime_to_absolutetime
 * Must be called with interrupts disabled
 * Returned value is only valid until the next update to
 * mach_continuous_time 
 */
uint64_t
continuoustime_to_absolutetime(uint64_t conttime) {
        if (conttime <= mach_absolutetime_asleep)
                return 0;
        else
                return conttime - mach_absolutetime_asleep;
}

/*
 * absolutetime_to_continuoustime
 * Must be called with interrupts disabled
 * Returned value is only valid until the next update to
 * mach_continuous_time 
 */
uint64_t
absolutetime_to_continuoustime(uint64_t abstime) {
        return abstime + mach_absolutetime_asleep;
}

#if     CONFIG_DTRACE

/*
 * clock_get_calendar_nanotime_nowait
 *
 * Description: Non-blocking version of clock_get_calendar_nanotime()
 *
 * Notes:       This function operates by separately tracking calendar time
 *              updates using a two element structure to copy the calendar
 *              state, which may be asynchronously modified.  It utilizes
 *              barrier instructions in the tracking process and in the local
 *              stable snapshot process in order to ensure that a consistent
 *              snapshot is used to perform the calculation.
 */
void
clock_get_calendar_nanotime_nowait(
        clock_sec_t                     *secs,
        clock_nsec_t            *nanosecs)
{
        int i = 0;
        uint64_t                now;
        struct unlocked_clock_calend stable;
        struct bintime bt;

        for (;;) {
                stable = flipflop[i];           /* take snapshot */

                /*
                 * Use a barrier instructions to ensure atomicity.  We AND
                 * off the "in progress" bit to get the current generation
                 * count.
                 */
                (void)hw_atomic_and(&stable.gen, ~(uint32_t)1);

                /*
                 * If an update _is_ in progress, the generation count will be
                 * off by one, if it _was_ in progress, it will be off by two,
                 * and if we caught it at a good time, it will be equal (and
                 * our snapshot is threfore stable).
                 */
                if (flipflop[i].gen == stable.gen)
                        break;

                /* Switch to the other element of the flipflop, and try again. */
                i ^= 1;
        }

        now = mach_absolute_time();

        bt = get_scaled_time(now);

        bintime_add(&bt, &clock_calend.bintime);

        bintime2nsclock(&bt, secs, nanosecs);
}

static void 
clock_track_calend_nowait(void)
{
        int i;

        for (i = 0; i < 2; i++) {
                struct clock_calend tmp = clock_calend;

                /*
                 * Set the low bit if the generation count; since we use a
                 * barrier instruction to do this, we are guaranteed that this
                 * will flag an update in progress to an async caller trying
                 * to examine the contents.
                 */
                (void)hw_atomic_or(&flipflop[i].gen, 1);

                flipflop[i].calend = tmp;

                /*
                 * Increment the generation count to clear the low bit to
                 * signal completion.  If a caller compares the generation
                 * count after taking a copy while in progress, the count
                 * will be off by two.
                 */
                (void)hw_atomic_add(&flipflop[i].gen, 1);
        }
}

#endif  /* CONFIG_DTRACE */