16006 Need RFC8106 decode in snoop

[illumos-gate.git] / usr / src / uts / common / os / clock.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
/*        All Rights Reserved   */

/*
 * Copyright (c) 1988, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2013, Joyent, Inc.  All rights reserved.
 * Copyright (c) 2016 by Delphix. All rights reserved.
 * Copyright 2023 Oxide Computer Company
 */

#include <sys/param.h>
#include <sys/t_lock.h>
#include <sys/types.h>
#include <sys/tuneable.h>
#include <sys/sysmacros.h>
#include <sys/systm.h>
#include <sys/cpuvar.h>
#include <sys/lgrp.h>
#include <sys/user.h>
#include <sys/proc.h>
#include <sys/callo.h>
#include <sys/kmem.h>
#include <sys/var.h>
#include <sys/cmn_err.h>
#include <sys/swap.h>
#include <sys/vmsystm.h>
#include <sys/class.h>
#include <sys/time.h>
#include <sys/debug.h>
#include <sys/vtrace.h>
#include <sys/spl.h>
#include <sys/atomic.h>
#include <sys/dumphdr.h>
#include <sys/archsystm.h>
#include <sys/fs/swapnode.h>
#include <sys/panic.h>
#include <sys/disp.h>
#include <sys/msacct.h>
#include <sys/mem_cage.h>

#include <vm/page.h>
#include <vm/anon.h>
#include <vm/rm.h>
#include <sys/cyclic.h>
#include <sys/cpupart.h>
#include <sys/rctl.h>
#include <sys/task.h>
#include <sys/sdt.h>
#include <sys/ddi_periodic.h>
#include <sys/random.h>
#include <sys/modctl.h>
#include <sys/zone.h>

/*
 * for NTP support
 */
#include <sys/timex.h>
#include <sys/inttypes.h>

#include <sys/sunddi.h>
#include <sys/clock_impl.h>

/*
 * clock() is called straight from the clock cyclic; see clock_init().
 *
 * Functions:
 *      reprime clock
 *      maintain date
 *      jab the scheduler
 */

extern kcondvar_t       fsflush_cv;
extern sysinfo_t        sysinfo;
extern vminfo_t vminfo;
extern int      idleswtch;      /* flag set while idle in pswtch() */
extern hrtime_t volatile devinfo_freeze;

/*
 * high-precision avenrun values.  These are needed to make the
 * regular avenrun values accurate.
 */
static uint64_t hp_avenrun[3];
int     avenrun[3];             /* FSCALED average run queue lengths */
time_t  time;   /* time in seconds since 1970 - for compatibility only */

static struct loadavg_s loadavg;
/*
 * Phase/frequency-lock loop (PLL/FLL) definitions
 *
 * The following variables are read and set by the ntp_adjtime() system
 * call.
 *
 * time_state shows the state of the system clock, with values defined
 * in the timex.h header file.
 *
 * time_status shows the status of the system clock, with bits defined
 * in the timex.h header file.
 *
 * time_offset is used by the PLL/FLL to adjust the system time in small
 * increments.
 *
 * time_constant determines the bandwidth or "stiffness" of the PLL.
 *
 * time_tolerance determines maximum frequency error or tolerance of the
 * CPU clock oscillator and is a property of the architecture; however,
 * in principle it could change as result of the presence of external
 * discipline signals, for instance.
 *
 * time_precision is usually equal to the kernel tick variable; however,
 * in cases where a precision clock counter or external clock is
 * available, the resolution can be much less than this and depend on
 * whether the external clock is working or not.
 *
 * time_maxerror is initialized by a ntp_adjtime() call and increased by
 * the kernel once each second to reflect the maximum error bound
 * growth.
 *
 * time_esterror is set and read by the ntp_adjtime() call, but
 * otherwise not used by the kernel.
 */
int32_t time_state = TIME_OK;   /* clock state */
int32_t time_status = STA_UNSYNC;       /* clock status bits */
int32_t time_offset = 0;                /* time offset (us) */
int32_t time_constant = 0;              /* pll time constant */
int32_t time_tolerance = MAXFREQ;       /* frequency tolerance (scaled ppm) */
int32_t time_precision = 1;     /* clock precision (us) */
int32_t time_maxerror = MAXPHASE;       /* maximum error (us) */
int32_t time_esterror = MAXPHASE;       /* estimated error (us) */

/*
 * The following variables establish the state of the PLL/FLL and the
 * residual time and frequency offset of the local clock. The scale
 * factors are defined in the timex.h header file.
 *
 * time_phase and time_freq are the phase increment and the frequency
 * increment, respectively, of the kernel time variable.
 *
 * time_freq is set via ntp_adjtime() from a value stored in a file when
 * the synchronization daemon is first started. Its value is retrieved
 * via ntp_adjtime() and written to the file about once per hour by the
 * daemon.
 *
 * time_adj is the adjustment added to the value of tick at each timer
 * interrupt and is recomputed from time_phase and time_freq at each
 * seconds rollover.
 *
 * time_reftime is the second's portion of the system time at the last
 * call to ntp_adjtime(). It is used to adjust the time_freq variable
 * and to increase the time_maxerror as the time since last update
 * increases.
 */
int32_t time_phase = 0;         /* phase offset (scaled us) */
int32_t time_freq = 0;          /* frequency offset (scaled ppm) */
int32_t time_adj = 0;           /* tick adjust (scaled 1 / hz) */
int32_t time_reftime = 0;               /* time at last adjustment (s) */

/*
 * The scale factors of the following variables are defined in the
 * timex.h header file.
 *
 * pps_time contains the time at each calibration interval, as read by
 * microtime(). pps_count counts the seconds of the calibration
 * interval, the duration of which is nominally pps_shift in powers of
 * two.
 *
 * pps_offset is the time offset produced by the time median filter
 * pps_tf[], while pps_jitter is the dispersion (jitter) measured by
 * this filter.
 *
 * pps_freq is the frequency offset produced by the frequency median
 * filter pps_ff[], while pps_stabil is the dispersion (wander) measured
 * by this filter.
 *
 * pps_usec is latched from a high resolution counter or external clock
 * at pps_time. Here we want the hardware counter contents only, not the
 * contents plus the time_tv.usec as usual.
 *
 * pps_valid counts the number of seconds since the last PPS update. It
 * is used as a watchdog timer to disable the PPS discipline should the
 * PPS signal be lost.
 *
 * pps_glitch counts the number of seconds since the beginning of an
 * offset burst more than tick/2 from current nominal offset. It is used
 * mainly to suppress error bursts due to priority conflicts between the
 * PPS interrupt and timer interrupt.
 *
 * pps_intcnt counts the calibration intervals for use in the interval-
 * adaptation algorithm. It's just too complicated for words.
 */
struct timeval pps_time;        /* kernel time at last interval */
int32_t pps_tf[] = {0, 0, 0};   /* pps time offset median filter (us) */
int32_t pps_offset = 0;         /* pps time offset (us) */
int32_t pps_jitter = MAXTIME;   /* time dispersion (jitter) (us) */
int32_t pps_ff[] = {0, 0, 0};   /* pps frequency offset median filter */
int32_t pps_freq = 0;           /* frequency offset (scaled ppm) */
int32_t pps_stabil = MAXFREQ;   /* frequency dispersion (scaled ppm) */
int32_t pps_usec = 0;           /* microsec counter at last interval */
int32_t pps_valid = PPS_VALID;  /* pps signal watchdog counter */
int32_t pps_glitch = 0;         /* pps signal glitch counter */
int32_t pps_count = 0;          /* calibration interval counter (s) */
int32_t pps_shift = PPS_SHIFT;  /* interval duration (s) (shift) */
int32_t pps_intcnt = 0;         /* intervals at current duration */

/*
 * PPS signal quality monitors
 *
 * pps_jitcnt counts the seconds that have been discarded because the
 * jitter measured by the time median filter exceeds the limit MAXTIME
 * (100 us).
 *
 * pps_calcnt counts the frequency calibration intervals, which are
 * variable from 4 s to 256 s.
 *
 * pps_errcnt counts the calibration intervals which have been discarded
 * because the wander exceeds the limit MAXFREQ (100 ppm) or where the
 * calibration interval jitter exceeds two ticks.
 *
 * pps_stbcnt counts the calibration intervals that have been discarded
 * because the frequency wander exceeds the limit MAXFREQ / 4 (25 us).
 */
int32_t pps_jitcnt = 0;         /* jitter limit exceeded */
int32_t pps_calcnt = 0;         /* calibration intervals */
int32_t pps_errcnt = 0;         /* calibration errors */
int32_t pps_stbcnt = 0;         /* stability limit exceeded */

kcondvar_t lbolt_cv;

/*
 * Hybrid lbolt implementation:
 *
 * The service historically provided by the lbolt and lbolt64 variables has
 * been replaced by the ddi_get_lbolt() and ddi_get_lbolt64() routines, and the
 * original symbols removed from the system. The once clock driven variables are
 * now implemented in an event driven fashion, backed by gethrtime() coarsed to
 * the appropriate clock resolution. The default event driven implementation is
 * complemented by a cyclic driven one, active only during periods of intense
 * activity around the DDI lbolt routines, when a lbolt specific cyclic is
 * reprogramed to fire at a clock tick interval to serve consumers of lbolt who
 * rely on the original low cost of consulting a memory position.
 *
 * The implementation uses the number of calls to these routines and the
 * frequency of these to determine when to transition from event to cyclic
 * driven and vice-versa. These values are kept on a per CPU basis for
 * scalability reasons and to prevent CPUs from constantly invalidating a single
 * cache line when modifying a global variable. The transition from event to
 * cyclic mode happens once the thresholds are crossed, and activity on any CPU
 * can cause such transition.
 *
 * The lbolt_hybrid function pointer is called by ddi_get_lbolt() and
 * ddi_get_lbolt64(), and will point to lbolt_event_driven() or
 * lbolt_cyclic_driven() according to the current mode. When the thresholds
 * are exceeded, lbolt_event_driven() will reprogram the lbolt cyclic to
 * fire at a nsec_per_tick interval and increment an internal variable at
 * each firing. lbolt_hybrid will then point to lbolt_cyclic_driven(), which
 * will simply return the value of such variable. lbolt_cyclic() will attempt
 * to shut itself off at each threshold interval (sampling period for calls
 * to the DDI lbolt routines), and return to the event driven mode, but will
 * be prevented from doing so if lbolt_cyclic_driven() is being heavily used.
 *
 * lbolt_bootstrap is used during boot to serve lbolt consumers who don't wait
 * for the cyclic subsystem to be intialized.
 *
 */
int64_t lbolt_bootstrap(void);
int64_t lbolt_event_driven(void);
int64_t lbolt_cyclic_driven(void);
int64_t (*lbolt_hybrid)(void) = lbolt_bootstrap;
uint_t lbolt_ev_to_cyclic(caddr_t, caddr_t);

/*
 * lbolt's cyclic, installed by clock_init().
 */
static void lbolt_cyclic(void);

/*
 * Tunable to keep lbolt in cyclic driven mode. This will prevent the system
 * from switching back to event driven, once it reaches cyclic mode.
 */
static boolean_t lbolt_cyc_only = B_FALSE;

/*
 * Cache aligned, per CPU structure with lbolt usage statistics.
 */
static lbolt_cpu_t *lb_cpu;

/*
 * Single, cache aligned, structure with all the information required by
 * the lbolt implementation.
 */
lbolt_info_t *lb_info;


int one_sec = 1; /* turned on once every second */
static int fsflushcnt;  /* counter for t_fsflushr */
int     dosynctodr = 1; /* patchable; enable/disable sync to TOD chip */
int     tod_needsync = 0;       /* need to sync tod chip with software time */
static int tod_broken = 0;      /* clock chip doesn't work */
time_t  boot_time = 0;          /* Boot time in seconds since 1970 */
cyclic_id_t clock_cyclic;       /* clock()'s cyclic_id */
cyclic_id_t deadman_cyclic;     /* deadman()'s cyclic_id */

extern void clock_tick_schedule(int);
extern void set_freemem(void);
extern void pageout_deadman(void);

static int lgrp_ticks;          /* counter to schedule lgrp load calcs */

/*
 * for tod fault detection
 */
#define TOD_REF_FREQ            ((longlong_t)(NANOSEC))
#define TOD_STALL_THRESHOLD     (TOD_REF_FREQ * 3 / 2)
#define TOD_JUMP_THRESHOLD      (TOD_REF_FREQ / 2)
#define TOD_FILTER_N            4
#define TOD_FILTER_SETTLE       (4 * TOD_FILTER_N)
static enum tod_fault_type tod_faulted = TOD_NOFAULT;

static int tod_status_flag = 0;         /* used by tod_validate() */

static hrtime_t prev_set_tick = 0;      /* gethrtime() prior to tod_set() */
static time_t prev_set_tod = 0;         /* tv_sec value passed to tod_set() */

/* patchable via /etc/system */
int tod_validate_enable = 1;

/* Diagnose/Limit messages about delay(9F) called from interrupt context */
int                     delay_from_interrupt_diagnose = 0;
volatile uint32_t       delay_from_interrupt_msg = 20;

/*
 * On non-SPARC systems, TOD validation must be deferred until gethrtime
 * returns non-zero values (after mach_clkinit's execution).
 * On SPARC systems, it must be deferred until after hrtime_base
 * and hres_last_tick are set (in the first invocation of hres_tick).
 * Since in both cases the prerequisites occur before the invocation of
 * tod_get() in clock(), the deferment is lifted there.
 */
static boolean_t tod_validate_deferred = B_TRUE;

/*
 * tod_fault_table[] must be aligned with
 * enum tod_fault_type in systm.h
 */
static char *tod_fault_table[] = {
        "Reversed",                     /* TOD_REVERSED */
        "Stalled",                      /* TOD_STALLED */
        "Jumped",                       /* TOD_JUMPED */
        "Changed in Clock Rate",        /* TOD_RATECHANGED */
        "Is Read-Only"                  /* TOD_RDONLY */
        /*
         * no strings needed for TOD_NOFAULT
         */
};

/*
 * test hook for tod broken detection in tod_validate
 */
int tod_unit_test = 0;
time_t tod_test_injector;

#define CLOCK_ADJ_HIST_SIZE     4

static int      adj_hist_entry;

int64_t clock_adj_hist[CLOCK_ADJ_HIST_SIZE];

static void calcloadavg(int, uint64_t *);
static int genloadavg(struct loadavg_s *);
static void loadavg_update();

void (*cmm_clock_callout)() = NULL;
void (*cpucaps_clock_callout)() = NULL;

extern clock_t clock_tick_proc_max;

static int64_t deadman_counter = 0;

static void
clock(void)
{
        kthread_t       *t;
        uint_t  nrunnable;
        uint_t  w_io;
        cpu_t   *cp;
        cpupart_t *cpupart;
        void    (*funcp)();
        int32_t ltemp;
        int64_t lltemp;
        int s;
        int do_lgrp_load;
        int i;
        clock_t now = LBOLT_NO_ACCOUNT; /* current tick */

        if (panicstr)
                return;

        /*
         * Make sure that 'freemem' do not drift too far from the truth
         */
        set_freemem();


        /*
         * Before the section which is repeated is executed, we do
         * the time delta processing which occurs every clock tick
         *
         * There is additional processing which happens every time
         * the nanosecond counter rolls over which is described
         * below - see the section which begins with : if (one_sec)
         *
         * This section marks the beginning of the precision-kernel
         * code fragment.
         *
         * First, compute the phase adjustment. If the low-order bits
         * (time_phase) of the update overflow, bump the higher order
         * bits (time_update).
         */
        time_phase += time_adj;
        if (time_phase <= -FINEUSEC) {
                ltemp = -time_phase / SCALE_PHASE;
                time_phase += ltemp * SCALE_PHASE;
                s = hr_clock_lock();
                timedelta -= ltemp * (NANOSEC/MICROSEC);
                hr_clock_unlock(s);
        } else if (time_phase >= FINEUSEC) {
                ltemp = time_phase / SCALE_PHASE;
                time_phase -= ltemp * SCALE_PHASE;
                s = hr_clock_lock();
                timedelta += ltemp * (NANOSEC/MICROSEC);
                hr_clock_unlock(s);
        }

        /*
         * End of precision-kernel code fragment which is processed
         * every timer interrupt.
         *
         * Continue with the interrupt processing as scheduled.
         */
        /*
         * Count the number of runnable threads and the number waiting
         * for some form of I/O to complete -- gets added to
         * sysinfo.waiting.  To know the state of the system, must add
         * wait counts from all CPUs.  Also add up the per-partition
         * statistics.
         */
        w_io = 0;
        nrunnable = 0;

        /*
         * keep track of when to update lgrp/part loads
         */

        do_lgrp_load = 0;
        if (lgrp_ticks++ >= hz / 10) {
                lgrp_ticks = 0;
                do_lgrp_load = 1;
        }

        if (one_sec) {
                loadavg_update();
                deadman_counter++;
                pageout_deadman();
        }

        /*
         * First count the threads waiting on kpreempt queues in each
         * CPU partition.
         */

        cpupart = cp_list_head;
        do {
                uint_t cpupart_nrunnable = cpupart->cp_kp_queue.disp_nrunnable;

                cpupart->cp_updates++;
                nrunnable += cpupart_nrunnable;
                cpupart->cp_nrunnable_cum += cpupart_nrunnable;
                if (one_sec) {
                        cpupart->cp_nrunning = 0;
                        cpupart->cp_nrunnable = cpupart_nrunnable;
                }
        } while ((cpupart = cpupart->cp_next) != cp_list_head);


        /* Now count the per-CPU statistics. */
        cp = cpu_list;
        do {
                uint_t cpu_nrunnable = cp->cpu_disp->disp_nrunnable;

                nrunnable += cpu_nrunnable;
                cpupart = cp->cpu_part;
                cpupart->cp_nrunnable_cum += cpu_nrunnable;
                if (one_sec) {
                        cpupart->cp_nrunnable += cpu_nrunnable;
                        /*
                         * Update user, system, and idle cpu times.
                         */
                        cpupart->cp_nrunning++;
                        /*
                         * w_io is used to update sysinfo.waiting during
                         * one_second processing below.  Only gather w_io
                         * information when we walk the list of cpus if we're
                         * going to perform one_second processing.
                         */
                        w_io += CPU_STATS(cp, sys.iowait);
                }

                if (one_sec && (cp->cpu_flags & CPU_EXISTS)) {
                        int i, load, change;
                        hrtime_t intracct, intrused;
                        const hrtime_t maxnsec = 1000000000;
                        const int precision = 100;

                        /*
                         * Estimate interrupt load on this cpu each second.
                         * Computes cpu_intrload as %utilization (0-99).
                         */

                        /* add up interrupt time from all micro states */
                        for (intracct = 0, i = 0; i < NCMSTATES; i++)
                                intracct += cp->cpu_intracct[i];
                        scalehrtime(&intracct);

                        /* compute nsec used in the past second */
                        intrused = intracct - cp->cpu_intrlast;
                        cp->cpu_intrlast = intracct;

                        /* limit the value for safety (and the first pass) */
                        if (intrused >= maxnsec)
                                intrused = maxnsec - 1;

                        /* calculate %time in interrupt */
                        load = (precision * intrused) / maxnsec;
                        ASSERT(load >= 0 && load < precision);
                        change = cp->cpu_intrload - load;

                        /* jump to new max, or decay the old max */
                        if (change < 0)
                                cp->cpu_intrload = load;
                        else if (change > 0)
                                cp->cpu_intrload -= (change + 3) / 4;

                        DTRACE_PROBE3(cpu_intrload,
                            cpu_t *, cp,
                            hrtime_t, intracct,
                            hrtime_t, intrused);
                }

                if (do_lgrp_load &&
                    (cp->cpu_flags & CPU_EXISTS)) {
                        /*
                         * When updating the lgroup's load average,
                         * account for the thread running on the CPU.
                         * If the CPU is the current one, then we need
                         * to account for the underlying thread which
                         * got the clock interrupt not the thread that is
                         * handling the interrupt and caculating the load
                         * average
                         */
                        t = cp->cpu_thread;
                        if (CPU == cp)
                                t = t->t_intr;

                        /*
                         * Account for the load average for this thread if
                         * it isn't the idle thread or it is on the interrupt
                         * stack and not the current CPU handling the clock
                         * interrupt
                         */
                        if ((t && t != cp->cpu_idle_thread) || (CPU != cp &&
                            CPU_ON_INTR(cp))) {
                                if (t->t_lpl == cp->cpu_lpl) {
                                        /* local thread */
                                        cpu_nrunnable++;
                                } else {
                                        /*
                                         * This is a remote thread, charge it
                                         * against its home lgroup.  Note that
                                         * we notice that a thread is remote
                                         * only if it's currently executing.
                                         * This is a reasonable approximation,
                                         * since queued remote threads are rare.
                                         * Note also that if we didn't charge
                                         * it to its home lgroup, remote
                                         * execution would often make a system
                                         * appear balanced even though it was
                                         * not, and thread placement/migration
                                         * would often not be done correctly.
                                         */
                                        lgrp_loadavg(t->t_lpl,
                                            LGRP_LOADAVG_IN_THREAD_MAX, 0);
                                }
                        }
                        lgrp_loadavg(cp->cpu_lpl,
                            cpu_nrunnable * LGRP_LOADAVG_IN_THREAD_MAX, 1);
                }
        } while ((cp = cp->cpu_next) != cpu_list);

        clock_tick_schedule(one_sec);

        /*
         * Check for a callout that needs be called from the clock
         * thread to support the membership protocol in a clustered
         * system.  Copy the function pointer so that we can reset
         * this to NULL if needed.
         */
        if ((funcp = cmm_clock_callout) != NULL)
                (*funcp)();

        if ((funcp = cpucaps_clock_callout) != NULL)
                (*funcp)();

        /*
         * Wakeup the cageout thread waiters once per second.
         */
        if (one_sec)
                kcage_tick();

        if (one_sec) {

                int drift, absdrift;
                timestruc_t tod;
                int s;

                /*
                 * Beginning of precision-kernel code fragment executed
                 * every second.
                 *
                 * On rollover of the second the phase adjustment to be
                 * used for the next second is calculated.  Also, the
                 * maximum error is increased by the tolerance.  If the
                 * PPS frequency discipline code is present, the phase is
                 * increased to compensate for the CPU clock oscillator
                 * frequency error.
                 *
                 * On a 32-bit machine and given parameters in the timex.h
                 * header file, the maximum phase adjustment is +-512 ms
                 * and maximum frequency offset is (a tad less than)
                 * +-512 ppm. On a 64-bit machine, you shouldn't need to ask.
                 */
                time_maxerror += time_tolerance / SCALE_USEC;

                /*
                 * Leap second processing. If in leap-insert state at
                 * the end of the day, the system clock is set back one
                 * second; if in leap-delete state, the system clock is
                 * set ahead one second. The microtime() routine or
                 * external clock driver will insure that reported time
                 * is always monotonic. The ugly divides should be
                 * replaced.
                 */
                switch (time_state) {

                case TIME_OK:
                        if (time_status & STA_INS)
                                time_state = TIME_INS;
                        else if (time_status & STA_DEL)
                                time_state = TIME_DEL;
                        break;

                case TIME_INS:
                        if (hrestime.tv_sec % 86400 == 0) {
                                s = hr_clock_lock();
                                hrestime.tv_sec--;
                                hr_clock_unlock(s);
                                time_state = TIME_OOP;
                        }
                        break;

                case TIME_DEL:
                        if ((hrestime.tv_sec + 1) % 86400 == 0) {
                                s = hr_clock_lock();
                                hrestime.tv_sec++;
                                hr_clock_unlock(s);
                                time_state = TIME_WAIT;
                        }
                        break;

                case TIME_OOP:
                        time_state = TIME_WAIT;
                        break;

                case TIME_WAIT:
                        if (!(time_status & (STA_INS | STA_DEL)))
                                time_state = TIME_OK;
                default:
                        break;
                }

                /*
                 * Compute the phase adjustment for the next second. In
                 * PLL mode, the offset is reduced by a fixed factor
                 * times the time constant. In FLL mode the offset is
                 * used directly. In either mode, the maximum phase
                 * adjustment for each second is clamped so as to spread
                 * the adjustment over not more than the number of
                 * seconds between updates.
                 */
                if (time_offset == 0)
                        time_adj = 0;
                else if (time_offset < 0) {
                        lltemp = -time_offset;
                        if (!(time_status & STA_FLL)) {
                                if ((1 << time_constant) >= SCALE_KG)
                                        lltemp *= (1 << time_constant) /
                                            SCALE_KG;
                                else
                                        lltemp = (lltemp / SCALE_KG) >>
                                            time_constant;
                        }
                        if (lltemp > (MAXPHASE / MINSEC) * SCALE_UPDATE)
                                lltemp = (MAXPHASE / MINSEC) * SCALE_UPDATE;
                        time_offset += lltemp;
                        time_adj = -(lltemp * SCALE_PHASE) / hz / SCALE_UPDATE;
                } else {
                        lltemp = time_offset;
                        if (!(time_status & STA_FLL)) {
                                if ((1 << time_constant) >= SCALE_KG)
                                        lltemp *= (1 << time_constant) /
                                            SCALE_KG;
                                else
                                        lltemp = (lltemp / SCALE_KG) >>
                                            time_constant;
                        }
                        if (lltemp > (MAXPHASE / MINSEC) * SCALE_UPDATE)
                                lltemp = (MAXPHASE / MINSEC) * SCALE_UPDATE;
                        time_offset -= lltemp;
                        time_adj = (lltemp * SCALE_PHASE) / hz / SCALE_UPDATE;
                }

                /*
                 * Compute the frequency estimate and additional phase
                 * adjustment due to frequency error for the next
                 * second. When the PPS signal is engaged, gnaw on the
                 * watchdog counter and update the frequency computed by
                 * the pll and the PPS signal.
                 */
                pps_valid++;
                if (pps_valid == PPS_VALID) {
                        pps_jitter = MAXTIME;
                        pps_stabil = MAXFREQ;
                        time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
                            STA_PPSWANDER | STA_PPSERROR);
                }
                lltemp = time_freq + pps_freq;

                if (lltemp)
                        time_adj += (lltemp * SCALE_PHASE) / (SCALE_USEC * hz);

                /*
                 * End of precision kernel-code fragment
                 *
                 * The section below should be modified if we are planning
                 * to use NTP for synchronization.
                 *
                 * Note: the clock synchronization code now assumes
                 * the following:
                 *   - if dosynctodr is 1, then compute the drift between
                 *      the tod chip and software time and adjust one or
                 *      the other depending on the circumstances
                 *
                 *   - if dosynctodr is 0, then the tod chip is independent
                 *      of the software clock and should not be adjusted,
                 *      but allowed to free run.  this allows NTP to sync.
                 *      hrestime without any interference from the tod chip.
                 */

                tod_validate_deferred = B_FALSE;
                mutex_enter(&tod_lock);
                tod = tod_get();
                drift = tod.tv_sec - hrestime.tv_sec;
                absdrift = (drift >= 0) ? drift : -drift;
                if (tod_needsync || absdrift > 1) {
                        int s;
                        if (absdrift > 2) {
                                if (!tod_broken && tod_faulted == TOD_NOFAULT) {
                                        s = hr_clock_lock();
                                        hrestime = tod;
                                        membar_enter(); /* hrestime visible */
                                        timedelta = 0;
                                        timechanged++;
                                        tod_needsync = 0;
                                        hr_clock_unlock(s);
                                        callout_hrestime();

                                }
                        } else {
                                if (tod_needsync || !dosynctodr) {
                                        gethrestime(&tod);
                                        tod_set(tod);
                                        s = hr_clock_lock();
                                        if (timedelta == 0)
                                                tod_needsync = 0;
                                        hr_clock_unlock(s);
                                } else {
                                        /*
                                         * If the drift is 2 seconds on the
                                         * money, then the TOD is adjusting
                                         * the clock;  record that.
                                         */
                                        clock_adj_hist[adj_hist_entry++ %
                                            CLOCK_ADJ_HIST_SIZE] = now;
                                        s = hr_clock_lock();
                                        timedelta = (int64_t)drift*NANOSEC;
                                        hr_clock_unlock(s);
                                }
                        }
                }
                one_sec = 0;
                time = gethrestime_sec();  /* for crusty old kmem readers */
                mutex_exit(&tod_lock);

                /*
                 * Some drivers still depend on this... XXX
                 */
                cv_broadcast(&lbolt_cv);

                vminfo.freemem += freemem;
                {
                        pgcnt_t maxswap, resv, free;
                        pgcnt_t avail =
                            MAX((spgcnt_t)(availrmem - swapfs_minfree), 0);

                        maxswap = k_anoninfo.ani_mem_resv +
                            k_anoninfo.ani_max +avail;
                        /* Update ani_free */
                        set_anoninfo();
                        free = k_anoninfo.ani_free + avail;
                        resv = k_anoninfo.ani_phys_resv +
                            k_anoninfo.ani_mem_resv;

                        vminfo.swap_resv += resv;
                        /* number of reserved and allocated pages */
#ifdef  DEBUG
                        if (maxswap < free)
                                cmn_err(CE_WARN, "clock: maxswap < free");
                        if (maxswap < resv)
                                cmn_err(CE_WARN, "clock: maxswap < resv");
#endif
                        vminfo.swap_alloc += maxswap - free;
                        vminfo.swap_avail += maxswap - resv;
                        vminfo.swap_free += free;
                }
                vminfo.updates++;
                if (nrunnable) {
                        sysinfo.runque += nrunnable;
                        sysinfo.runocc++;
                }
                if (nswapped) {
                        sysinfo.swpque += nswapped;
                        sysinfo.swpocc++;
                }
                sysinfo.waiting += w_io;
                sysinfo.updates++;

                /*
                 * Wake up fsflush to write out DELWRI
                 * buffers, dirty pages and other cached
                 * administrative data, e.g. inodes.
                 */
                if (--fsflushcnt <= 0) {
                        fsflushcnt = tune.t_fsflushr;
                        cv_signal(&fsflush_cv);
                }

                vmmeter();
                calcloadavg(genloadavg(&loadavg), hp_avenrun);
                for (i = 0; i < 3; i++)
                        /*
                         * At the moment avenrun[] can only hold 31
                         * bits of load average as it is a signed
                         * int in the API. We need to ensure that
                         * hp_avenrun[i] >> (16 - FSHIFT) will not be
                         * too large. If it is, we put the largest value
                         * that we can use into avenrun[i]. This is
                         * kludgey, but about all we can do until we
                         * avenrun[] is declared as an array of uint64[]
                         */
                        if (hp_avenrun[i] < ((uint64_t)1<<(31+16-FSHIFT)))
                                avenrun[i] = (int32_t)(hp_avenrun[i] >>
                                    (16 - FSHIFT));
                        else
                                avenrun[i] = 0x7fffffff;

                cpupart = cp_list_head;
                do {
                        calcloadavg(genloadavg(&cpupart->cp_loadavg),
                            cpupart->cp_hp_avenrun);
                } while ((cpupart = cpupart->cp_next) != cp_list_head);

                /*
                 * Wake up the swapper thread if necessary.
                 */
                if (runin ||
                    (runout && (avefree < desfree || wake_sched_sec))) {
                        t = &t0;
                        thread_lock(t);
                        if (t->t_state == TS_STOPPED) {
                                runin = runout = 0;
                                wake_sched_sec = 0;
                                t->t_whystop = 0;
                                t->t_whatstop = 0;
                                t->t_schedflag &= ~TS_ALLSTART;
                                THREAD_TRANSITION(t);
                                setfrontdq(t);
                        }
                        thread_unlock(t);
                }
        }

        /*
         * Wake up the swapper if any high priority swapped-out threads
         * became runable during the last tick.
         */
        if (wake_sched) {
                t = &t0;
                thread_lock(t);
                if (t->t_state == TS_STOPPED) {
                        runin = runout = 0;
                        wake_sched = 0;
                        t->t_whystop = 0;
                        t->t_whatstop = 0;
                        t->t_schedflag &= ~TS_ALLSTART;
                        THREAD_TRANSITION(t);
                        setfrontdq(t);
                }
                thread_unlock(t);
        }
}

void
clock_init(void)
{
        cyc_handler_t clk_hdlr, lbolt_hdlr;
        cyc_time_t clk_when, lbolt_when;
        int i, sz;
        intptr_t buf;

        /*
         * Setup handler and timer for the clock cyclic.
         */
        clk_hdlr.cyh_func = (cyc_func_t)clock;
        clk_hdlr.cyh_level = CY_LOCK_LEVEL;
        clk_hdlr.cyh_arg = NULL;

        clk_when.cyt_when = 0;
        clk_when.cyt_interval = nsec_per_tick;

        /*
         * The lbolt cyclic will be reprogramed to fire at a nsec_per_tick
         * interval to satisfy performance needs of the DDI lbolt consumers.
         * It is off by default.
         */
        lbolt_hdlr.cyh_func = (cyc_func_t)lbolt_cyclic;
        lbolt_hdlr.cyh_level = CY_LOCK_LEVEL;
        lbolt_hdlr.cyh_arg = NULL;

        lbolt_when.cyt_interval = nsec_per_tick;

        /*
         * Allocate cache line aligned space for the per CPU lbolt data and
         * lbolt info structures, and initialize them with their default
         * values. Note that these structures are also cache line sized.
         */
        sz = sizeof (lbolt_info_t) + CPU_CACHE_COHERENCE_SIZE;
        buf = (intptr_t)kmem_zalloc(sz, KM_SLEEP);
        lb_info = (lbolt_info_t *)P2ROUNDUP(buf, CPU_CACHE_COHERENCE_SIZE);

        if (hz != HZ_DEFAULT)
                lb_info->lbi_thresh_interval = LBOLT_THRESH_INTERVAL *
                    hz/HZ_DEFAULT;
        else
                lb_info->lbi_thresh_interval = LBOLT_THRESH_INTERVAL;

        lb_info->lbi_thresh_calls = LBOLT_THRESH_CALLS;

        sz = (sizeof (lbolt_cpu_t) * max_ncpus) + CPU_CACHE_COHERENCE_SIZE;
        buf = (intptr_t)kmem_zalloc(sz, KM_SLEEP);
        lb_cpu = (lbolt_cpu_t *)P2ROUNDUP(buf, CPU_CACHE_COHERENCE_SIZE);

        for (i = 0; i < max_ncpus; i++)
                lb_cpu[i].lbc_counter = lb_info->lbi_thresh_calls;

        /*
         * Install the softint used to switch between event and cyclic driven
         * lbolt. We use a soft interrupt to make sure the context of the
         * cyclic reprogram call is safe.
         */
        lbolt_softint_add();

        /*
         * Since the hybrid lbolt implementation is based on a hardware counter
         * that is reset at every hardware reboot and that we'd like to have
         * the lbolt value starting at zero after both a hardware and a fast
         * reboot, we calculate the number of clock ticks the system's been up
         * and store it in the lbi_debug_time field of the lbolt info structure.
         * The value of this field will be subtracted from lbolt before
         * returning it.
         */
        lb_info->lbi_internal = lb_info->lbi_debug_time =
            (gethrtime()/nsec_per_tick);

        /*
         * lbolt_hybrid points at lbolt_bootstrap until now. The LBOLT_* macros
         * and lbolt_debug_{enter,return} use this value as an indication that
         * the initializaion above hasn't been completed. Setting lbolt_hybrid
         * to either lbolt_{cyclic,event}_driven here signals those code paths
         * that the lbolt related structures can be used.
         */
        if (lbolt_cyc_only) {
                lbolt_when.cyt_when = 0;
                lbolt_hybrid = lbolt_cyclic_driven;
        } else {
                lbolt_when.cyt_when = CY_INFINITY;
                lbolt_hybrid = lbolt_event_driven;
        }

        /*
         * Grab cpu_lock and install all three cyclics.
         */
        mutex_enter(&cpu_lock);

        clock_cyclic = cyclic_add(&clk_hdlr, &clk_when);
        lb_info->id.lbi_cyclic_id = cyclic_add(&lbolt_hdlr, &lbolt_when);

        mutex_exit(&cpu_lock);
}

/*
 * Called before calcloadavg to get 10-sec moving loadavg together
 */

static int
genloadavg(struct loadavg_s *avgs)
{
        int avg;
        int spos; /* starting position */
        int cpos; /* moving current position */
        int i;
        int slen;
        hrtime_t hr_avg;

        /* 10-second snapshot, calculate first positon */
        if (avgs->lg_len == 0) {
                return (0);
        }
        slen = avgs->lg_len < S_MOVAVG_SZ ? avgs->lg_len : S_MOVAVG_SZ;

        spos = (avgs->lg_cur - 1) >= 0 ? avgs->lg_cur - 1 :
            S_LOADAVG_SZ + (avgs->lg_cur - 1);
        for (i = hr_avg = 0; i < slen; i++) {
                cpos = (spos - i) >= 0 ? spos - i : S_LOADAVG_SZ + (spos - i);
                hr_avg += avgs->lg_loads[cpos];
        }

        hr_avg = hr_avg / slen;
        avg = hr_avg / (NANOSEC / LGRP_LOADAVG_IN_THREAD_MAX);

        return (avg);
}

/*
 * Run every second from clock () to update the loadavg count available to the
 * system and cpu-partitions.
 *
 * This works by sampling the previous usr, sys, wait time elapsed,
 * computing a delta, and adding that delta to the elapsed usr, sys,
 * wait increase.
 */

static void
loadavg_update()
{
        cpu_t *cp;
        cpupart_t *cpupart;
        hrtime_t cpu_total;
        int prev;

        cp = cpu_list;
        loadavg.lg_total = 0;

        /*
         * first pass totals up per-cpu statistics for system and cpu
         * partitions
         */

        do {
                struct loadavg_s *lavg;

                lavg = &cp->cpu_loadavg;

                cpu_total = cp->cpu_acct[CMS_USER] +
                    cp->cpu_acct[CMS_SYSTEM] + cp->cpu_waitrq;
                /* compute delta against last total */
                scalehrtime(&cpu_total);
                prev = (lavg->lg_cur - 1) >= 0 ? lavg->lg_cur - 1 :
                    S_LOADAVG_SZ + (lavg->lg_cur - 1);
                if (lavg->lg_loads[prev] <= 0) {
                        lavg->lg_loads[lavg->lg_cur] = cpu_total;
                        cpu_total = 0;
                } else {
                        lavg->lg_loads[lavg->lg_cur] = cpu_total;
                        cpu_total = cpu_total - lavg->lg_loads[prev];
                        if (cpu_total < 0)
                                cpu_total = 0;
                }

                lavg->lg_cur = (lavg->lg_cur + 1) % S_LOADAVG_SZ;
                lavg->lg_len = (lavg->lg_len + 1) < S_LOADAVG_SZ ?
                    lavg->lg_len + 1 : S_LOADAVG_SZ;

                loadavg.lg_total += cpu_total;
                cp->cpu_part->cp_loadavg.lg_total += cpu_total;

        } while ((cp = cp->cpu_next) != cpu_list);

        loadavg.lg_loads[loadavg.lg_cur] = loadavg.lg_total;
        loadavg.lg_cur = (loadavg.lg_cur + 1) % S_LOADAVG_SZ;
        loadavg.lg_len = (loadavg.lg_len + 1) < S_LOADAVG_SZ ?
            loadavg.lg_len + 1 : S_LOADAVG_SZ;
        /*
         * Second pass updates counts
         */
        cpupart = cp_list_head;

        do {
                struct loadavg_s *lavg;

                lavg = &cpupart->cp_loadavg;
                lavg->lg_loads[lavg->lg_cur] = lavg->lg_total;
                lavg->lg_total = 0;
                lavg->lg_cur = (lavg->lg_cur + 1) % S_LOADAVG_SZ;
                lavg->lg_len = (lavg->lg_len + 1) < S_LOADAVG_SZ ?
                    lavg->lg_len + 1 : S_LOADAVG_SZ;

        } while ((cpupart = cpupart->cp_next) != cp_list_head);

        /*
         * Third pass totals up per-zone statistics.
         */
        zone_loadavg_update();
}

/*
 * clock_update() - local clock update
 *
 * This routine is called by ntp_adjtime() to update the local clock
 * phase and frequency. The implementation is of an
 * adaptive-parameter, hybrid phase/frequency-lock loop (PLL/FLL). The
 * routine computes new time and frequency offset estimates for each
 * call.  The PPS signal itself determines the new time offset,
 * instead of the calling argument.  Presumably, calls to
 * ntp_adjtime() occur only when the caller believes the local clock
 * is valid within some bound (+-128 ms with NTP). If the caller's
 * time is far different than the PPS time, an argument will ensue,
 * and it's not clear who will lose.
 *
 * For uncompensated quartz crystal oscillatores and nominal update
 * intervals less than 1024 s, operation should be in phase-lock mode
 * (STA_FLL = 0), where the loop is disciplined to phase. For update
 * intervals greater than this, operation should be in frequency-lock
 * mode (STA_FLL = 1), where the loop is disciplined to frequency.
 *
 * Note: mutex(&tod_lock) is in effect.
 */
void
clock_update(int offset)
{
        int ltemp, mtemp, s;

        ASSERT(MUTEX_HELD(&tod_lock));

        if (!(time_status & STA_PLL) && !(time_status & STA_PPSTIME))
                return;
        ltemp = offset;
        if ((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))
                ltemp = pps_offset;

        /*
         * Scale the phase adjustment and clamp to the operating range.
         */
        if (ltemp > MAXPHASE)
                time_offset = MAXPHASE * SCALE_UPDATE;
        else if (ltemp < -MAXPHASE)
                time_offset = -(MAXPHASE * SCALE_UPDATE);
        else
                time_offset = ltemp * SCALE_UPDATE;

        /*
         * Select whether the frequency is to be controlled and in which
         * mode (PLL or FLL). Clamp to the operating range. Ugly
         * multiply/divide should be replaced someday.
         */
        if (time_status & STA_FREQHOLD || time_reftime == 0)
                time_reftime = hrestime.tv_sec;

        mtemp = hrestime.tv_sec - time_reftime;
        time_reftime = hrestime.tv_sec;

        if (time_status & STA_FLL) {
                if (mtemp >= MINSEC) {
                        ltemp = ((time_offset / mtemp) * (SCALE_USEC /
                            SCALE_UPDATE));
                        if (ltemp)
                                time_freq += ltemp / SCALE_KH;
                }
        } else {
                if (mtemp < MAXSEC) {
                        ltemp *= mtemp;
                        if (ltemp)
                                time_freq += (int)(((int64_t)ltemp *
                                    SCALE_USEC) / SCALE_KF)
                                    / (1 << (time_constant * 2));
                }
        }
        if (time_freq > time_tolerance)
                time_freq = time_tolerance;
        else if (time_freq < -time_tolerance)
                time_freq = -time_tolerance;

        s = hr_clock_lock();
        tod_needsync = 1;
        hr_clock_unlock(s);
}

/*
 * ddi_hardpps() - discipline CPU clock oscillator to external PPS signal
 *
 * This routine is called at each PPS interrupt in order to discipline
 * the CPU clock oscillator to the PPS signal. It measures the PPS phase
 * and leaves it in a handy spot for the clock() routine. It
 * integrates successive PPS phase differences and calculates the
 * frequency offset. This is used in clock() to discipline the CPU
 * clock oscillator so that intrinsic frequency error is cancelled out.
 * The code requires the caller to capture the time and hardware counter
 * value at the on-time PPS signal transition.
 *
 * Note that, on some Unix systems, this routine runs at an interrupt
 * priority level higher than the timer interrupt routine clock().
 * Therefore, the variables used are distinct from the clock()
 * variables, except for certain exceptions: The PPS frequency pps_freq
 * and phase pps_offset variables are determined by this routine and
 * updated atomically. The time_tolerance variable can be considered a
 * constant, since it is infrequently changed, and then only when the
 * PPS signal is disabled. The watchdog counter pps_valid is updated
 * once per second by clock() and is atomically cleared in this
 * routine.
 *
 * tvp is the time of the last tick; usec is a microsecond count since the
 * last tick.
 *
 * Note: In Solaris systems, the tick value is actually given by
 *       usec_per_tick.  This is called from the serial driver cdintr(),
 *       or equivalent, at a high PIL.  Because the kernel keeps a
 *       highresolution time, the following code can accept either
 *       the traditional argument pair, or the current highres timestamp
 *       in tvp and zero in usec.
 */
void
ddi_hardpps(struct timeval *tvp, int usec)
{
        int u_usec, v_usec, bigtick;
        time_t cal_sec;
        int cal_usec;

        /*
         * An occasional glitch can be produced when the PPS interrupt
         * occurs in the clock() routine before the time variable is
         * updated. Here the offset is discarded when the difference
         * between it and the last one is greater than tick/2, but not
         * if the interval since the first discard exceeds 30 s.
         */
        time_status |= STA_PPSSIGNAL;
        time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
        pps_valid = 0;
        u_usec = -tvp->tv_usec;
        if (u_usec < -(MICROSEC/2))
                u_usec += MICROSEC;
        v_usec = pps_offset - u_usec;
        if (v_usec < 0)
                v_usec = -v_usec;
        if (v_usec > (usec_per_tick >> 1)) {
                if (pps_glitch > MAXGLITCH) {
                        pps_glitch = 0;
                        pps_tf[2] = u_usec;
                        pps_tf[1] = u_usec;
                } else {
                        pps_glitch++;
                        u_usec = pps_offset;
                }
        } else
                pps_glitch = 0;

        /*
         * A three-stage median filter is used to help deglitch the pps
         * time. The median sample becomes the time offset estimate; the
         * difference between the other two samples becomes the time
         * dispersion (jitter) estimate.
         */
        pps_tf[2] = pps_tf[1];
        pps_tf[1] = pps_tf[0];
        pps_tf[0] = u_usec;
        if (pps_tf[0] > pps_tf[1]) {
                if (pps_tf[1] > pps_tf[2]) {
                        pps_offset = pps_tf[1];         /* 0 1 2 */
                        v_usec = pps_tf[0] - pps_tf[2];
                } else if (pps_tf[2] > pps_tf[0]) {
                        pps_offset = pps_tf[0];         /* 2 0 1 */
                        v_usec = pps_tf[2] - pps_tf[1];
                } else {
                        pps_offset = pps_tf[2];         /* 0 2 1 */
                        v_usec = pps_tf[0] - pps_tf[1];
                }
        } else {
                if (pps_tf[1] < pps_tf[2]) {
                        pps_offset = pps_tf[1];         /* 2 1 0 */
                        v_usec = pps_tf[2] - pps_tf[0];
                } else  if (pps_tf[2] < pps_tf[0]) {
                        pps_offset = pps_tf[0];         /* 1 0 2 */
                        v_usec = pps_tf[1] - pps_tf[2];
                } else {
                        pps_offset = pps_tf[2];         /* 1 2 0 */
                        v_usec = pps_tf[1] - pps_tf[0];
                }
        }
        if (v_usec > MAXTIME)
                pps_jitcnt++;
        v_usec = (v_usec << PPS_AVG) - pps_jitter;
        pps_jitter += v_usec / (1 << PPS_AVG);
        if (pps_jitter > (MAXTIME >> 1))
                time_status |= STA_PPSJITTER;

        /*
         * During the calibration interval adjust the starting time when
         * the tick overflows. At the end of the interval compute the
         * duration of the interval and the difference of the hardware
         * counters at the beginning and end of the interval. This code
         * is deliciously complicated by the fact valid differences may
         * exceed the value of tick when using long calibration
         * intervals and small ticks. Note that the counter can be
         * greater than tick if caught at just the wrong instant, but
         * the values returned and used here are correct.
         */
        bigtick = (int)usec_per_tick * SCALE_USEC;
        pps_usec -= pps_freq;
        if (pps_usec >= bigtick)
                pps_usec -= bigtick;
        if (pps_usec < 0)
                pps_usec += bigtick;
        pps_time.tv_sec++;
        pps_count++;
        if (pps_count < (1 << pps_shift))
                return;
        pps_count = 0;
        pps_calcnt++;
        u_usec = usec * SCALE_USEC;
        v_usec = pps_usec - u_usec;
        if (v_usec >= bigtick >> 1)
                v_usec -= bigtick;
        if (v_usec < -(bigtick >> 1))
                v_usec += bigtick;
        if (v_usec < 0)
                v_usec = -(-v_usec >> pps_shift);
        else
                v_usec = v_usec >> pps_shift;
        pps_usec = u_usec;
        cal_sec = tvp->tv_sec;
        cal_usec = tvp->tv_usec;
        cal_sec -= pps_time.tv_sec;
        cal_usec -= pps_time.tv_usec;
        if (cal_usec < 0) {
                cal_usec += MICROSEC;
                cal_sec--;
        }
        pps_time = *tvp;

        /*
         * Check for lost interrupts, noise, excessive jitter and
         * excessive frequency error. The number of timer ticks during
         * the interval may vary +-1 tick. Add to this a margin of one
         * tick for the PPS signal jitter and maximum frequency
         * deviation. If the limits are exceeded, the calibration
         * interval is reset to the minimum and we start over.
         */
        u_usec = (int)usec_per_tick << 1;
        if (!((cal_sec == -1 && cal_usec > (MICROSEC - u_usec)) ||
            (cal_sec == 0 && cal_usec < u_usec)) ||
            v_usec > time_tolerance || v_usec < -time_tolerance) {
                pps_errcnt++;
                pps_shift = PPS_SHIFT;
                pps_intcnt = 0;
                time_status |= STA_PPSERROR;
                return;
        }

        /*
         * A three-stage median filter is used to help deglitch the pps
         * frequency. The median sample becomes the frequency offset
         * estimate; the difference between the other two samples
         * becomes the frequency dispersion (stability) estimate.
         */
        pps_ff[2] = pps_ff[1];
        pps_ff[1] = pps_ff[0];
        pps_ff[0] = v_usec;
        if (pps_ff[0] > pps_ff[1]) {
                if (pps_ff[1] > pps_ff[2]) {
                        u_usec = pps_ff[1];             /* 0 1 2 */
                        v_usec = pps_ff[0] - pps_ff[2];
                } else if (pps_ff[2] > pps_ff[0]) {
                        u_usec = pps_ff[0];             /* 2 0 1 */
                        v_usec = pps_ff[2] - pps_ff[1];
                } else {
                        u_usec = pps_ff[2];             /* 0 2 1 */
                        v_usec = pps_ff[0] - pps_ff[1];
                }
        } else {
                if (pps_ff[1] < pps_ff[2]) {
                        u_usec = pps_ff[1];             /* 2 1 0 */
                        v_usec = pps_ff[2] - pps_ff[0];
                } else  if (pps_ff[2] < pps_ff[0]) {
                        u_usec = pps_ff[0];             /* 1 0 2 */
                        v_usec = pps_ff[1] - pps_ff[2];
                } else {
                        u_usec = pps_ff[2];             /* 1 2 0 */
                        v_usec = pps_ff[1] - pps_ff[0];
                }
        }

        /*
         * Here the frequency dispersion (stability) is updated. If it
         * is less than one-fourth the maximum (MAXFREQ), the frequency
         * offset is updated as well, but clamped to the tolerance. It
         * will be processed later by the clock() routine.
         */
        v_usec = (v_usec >> 1) - pps_stabil;
        if (v_usec < 0)
                pps_stabil -= -v_usec >> PPS_AVG;
        else
                pps_stabil += v_usec >> PPS_AVG;
        if (pps_stabil > MAXFREQ >> 2) {
                pps_stbcnt++;
                time_status |= STA_PPSWANDER;
                return;
        }
        if (time_status & STA_PPSFREQ) {
                if (u_usec < 0) {
                        pps_freq -= -u_usec >> PPS_AVG;
                        if (pps_freq < -time_tolerance)
                                pps_freq = -time_tolerance;
                        u_usec = -u_usec;
                } else {
                        pps_freq += u_usec >> PPS_AVG;
                        if (pps_freq > time_tolerance)
                                pps_freq = time_tolerance;
                }
        }

        /*
         * Here the calibration interval is adjusted. If the maximum
         * time difference is greater than tick / 4, reduce the interval
         * by half. If this is not the case for four consecutive
         * intervals, double the interval.
         */
        if (u_usec << pps_shift > bigtick >> 2) {
                pps_intcnt = 0;
                if (pps_shift > PPS_SHIFT)
                        pps_shift--;
        } else if (pps_intcnt >= 4) {
                pps_intcnt = 0;
                if (pps_shift < PPS_SHIFTMAX)
                        pps_shift++;
        } else
                pps_intcnt++;

        /*
         * If recovering from kmdb, then make sure the tod chip gets resynced.
         * If we took an early exit above, then we don't yet have a stable
         * calibration signal to lock onto, so don't mark the tod for sync
         * until we get all the way here.
         */
        {
                int s = hr_clock_lock();

                tod_needsync = 1;
                hr_clock_unlock(s);
        }
}

/*
 * Handle clock tick processing for a thread.
 * Check for timer action, enforce CPU rlimit, do profiling etc.
 */
void
clock_tick(kthread_t *t, int pending)
{
        struct proc *pp;
        klwp_id_t    lwp;
        struct as *as;
        clock_t ticks;
        int     poke = 0;               /* notify another CPU */
        int     user_mode;
        size_t   rss;
        int i, total_usec, usec;
        rctl_qty_t secs;

        ASSERT(pending > 0);

        /* Must be operating on a lwp/thread */
        if ((lwp = ttolwp(t)) == NULL) {
                panic("clock_tick: no lwp");
                /*NOTREACHED*/
        }

        for (i = 0; i < pending; i++) {
                CL_TICK(t);     /* Class specific tick processing */
                DTRACE_SCHED1(tick, kthread_t *, t);
        }

        pp = ttoproc(t);

        /* pp->p_lock makes sure that the thread does not exit */
        ASSERT(MUTEX_HELD(&pp->p_lock));

        user_mode = (lwp->lwp_state == LWP_USER);

        ticks = (pp->p_utime + pp->p_stime) % hz;
        /*
         * Update process times. Should use high res clock and state
         * changes instead of statistical sampling method. XXX
         */
        if (user_mode) {
                pp->p_utime += pending;
        } else {
                pp->p_stime += pending;
        }

        pp->p_ttime += pending;
        as = pp->p_as;

        /*
         * Update user profiling statistics. Get the pc from the
         * lwp when the AST happens.
         */
        if (pp->p_prof.pr_scale) {
                atomic_add_32(&lwp->lwp_oweupc, (int32_t)pending);
                if (user_mode) {
                        poke = 1;
                        aston(t);
                }
        }

        /*
         * If CPU was in user state, process lwp-virtual time
         * interval timer. The value passed to itimerdecr() has to be
         * in microseconds and has to be less than one second. Hence
         * this loop.
         */
        total_usec = usec_per_tick * pending;
        while (total_usec > 0) {
                usec = MIN(total_usec, (MICROSEC - 1));
                if (user_mode &&
                    timerisset(&lwp->lwp_timer[ITIMER_VIRTUAL].it_value) &&
                    itimerdecr(&lwp->lwp_timer[ITIMER_VIRTUAL], usec) == 0) {
                        poke = 1;
                        sigtoproc(pp, t, SIGVTALRM);
                }
                total_usec -= usec;
        }

        /*
         * If CPU was in user state, process lwp-profile
         * interval timer.
         */
        total_usec = usec_per_tick * pending;
        while (total_usec > 0) {
                usec = MIN(total_usec, (MICROSEC - 1));
                if (timerisset(&lwp->lwp_timer[ITIMER_PROF].it_value) &&
                    itimerdecr(&lwp->lwp_timer[ITIMER_PROF], usec) == 0) {
                        poke = 1;
                        sigtoproc(pp, t, SIGPROF);
                }
                total_usec -= usec;
        }

        /*
         * Enforce CPU resource controls:
         *   (a) process.max-cpu-time resource control
         *
         * Perform the check only if we have accumulated more a second.
         */
        if ((ticks + pending) >= hz) {
                (void) rctl_test(rctlproc_legacy[RLIMIT_CPU], pp->p_rctls, pp,
                    (pp->p_utime + pp->p_stime)/hz, RCA_UNSAFE_SIGINFO);
        }

        /*
         *   (b) task.max-cpu-time resource control
         *
         * If we have accumulated enough ticks, increment the task CPU
         * time usage and test for the resource limit. This minimizes the
         * number of calls to the rct_test(). The task CPU time mutex
         * is highly contentious as many processes can be sharing a task.
         */
        if (pp->p_ttime >= clock_tick_proc_max) {
                secs = task_cpu_time_incr(pp->p_task, pp->p_ttime);
                pp->p_ttime = 0;
                if (secs) {
                        (void) rctl_test(rc_task_cpu_time, pp->p_task->tk_rctls,
                            pp, secs, RCA_UNSAFE_SIGINFO);
                }
        }

        /*
         * Update memory usage for the currently running process.
         */
        rss = rm_asrss(as);
        PTOU(pp)->u_mem += rss;
        if (rss > PTOU(pp)->u_mem_max)
                PTOU(pp)->u_mem_max = rss;

        /*
         * Notify the CPU the thread is running on.
         */
        if (poke && t->t_cpu != CPU)
                poke_cpu(t->t_cpu->cpu_id);
}

void
profil_tick(uintptr_t upc)
{
        int ticks;
        proc_t *p = ttoproc(curthread);
        klwp_t *lwp = ttolwp(curthread);
        struct prof *pr = &p->p_prof;

        do {
                ticks = lwp->lwp_oweupc;
        } while (atomic_cas_32(&lwp->lwp_oweupc, ticks, 0) != ticks);

        mutex_enter(&p->p_pflock);
        if (pr->pr_scale >= 2 && upc >= pr->pr_off) {
                /*
                 * Old-style profiling
                 */
                uint16_t *slot = pr->pr_base;
                uint16_t old, new;
                if (pr->pr_scale != 2) {
                        uintptr_t delta = upc - pr->pr_off;
                        uintptr_t byteoff = ((delta >> 16) * pr->pr_scale) +
                            (((delta & 0xffff) * pr->pr_scale) >> 16);
                        if (byteoff >= (uintptr_t)pr->pr_size) {
                                mutex_exit(&p->p_pflock);
                                return;
                        }
                        slot += byteoff / sizeof (uint16_t);
                }
                if (fuword16(slot, &old) < 0 ||
                    (new = old + ticks) > SHRT_MAX ||
                    suword16(slot, new) < 0) {
                        pr->pr_scale = 0;
                }
        } else if (pr->pr_scale == 1) {
                /*
                 * PC Sampling
                 */
                model_t model = lwp_getdatamodel(lwp);
                int result;
#ifdef __lint
                model = model;
#endif
                while (ticks-- > 0) {
                        if (pr->pr_samples == pr->pr_size) {
                                /* buffer full, turn off sampling */
                                pr->pr_scale = 0;
                                break;
                        }
                        switch (SIZEOF_PTR(model)) {
                        case sizeof (uint32_t):
                                result = suword32(pr->pr_base, (uint32_t)upc);
                                break;
#ifdef _LP64
                        case sizeof (uint64_t):
                                result = suword64(pr->pr_base, (uint64_t)upc);
                                break;
#endif
                        default:
                                cmn_err(CE_WARN, "profil_tick: unexpected "
                                    "data model");
                                result = -1;
                                break;
                        }
                        if (result != 0) {
                                pr->pr_scale = 0;
                                break;
                        }
                        pr->pr_base = (caddr_t)pr->pr_base + SIZEOF_PTR(model);
                        pr->pr_samples++;
                }
        }
        mutex_exit(&p->p_pflock);
}

static void
delay_wakeup(void *arg)
{
        kthread_t       *t = arg;

        mutex_enter(&t->t_delay_lock);
        cv_signal(&t->t_delay_cv);
        mutex_exit(&t->t_delay_lock);
}

/*
 * The delay(9F) man page indicates that it can only be called from user or
 * kernel context - detect and diagnose bad calls. The following macro will
 * produce a limited number of messages identifying bad callers.  This is done
 * in a macro so that caller() is meaningful. When a bad caller is identified,
 * switching to 'drv_usecwait(TICK_TO_USEC(ticks));' may be appropriate.
 */
#define DELAY_CONTEXT_CHECK()   {                                       \
        uint32_t        m;                                              \
        char            *f;                                             \
        ulong_t         off;                                            \
                                                                        \
        m = delay_from_interrupt_msg;                                   \
        if (delay_from_interrupt_diagnose && servicing_interrupt() &&   \
            !panicstr && !devinfo_freeze &&                             \
            atomic_cas_32(&delay_from_interrupt_msg, m ? m : 1, m-1)) { \
                f = modgetsymname((uintptr_t)caller(), &off);           \
                cmn_err(CE_WARN, "delay(9F) called from "               \
                    "interrupt context: %s`%s",                         \
                    mod_containing_pc(caller()), f ? f : "...");        \
        }                                                               \
}

/*
 * delay_common: common delay code.
 */
static void
delay_common(clock_t ticks)
{
        kthread_t       *t = curthread;
        clock_t         deadline;
        clock_t         timeleft;
        callout_id_t    id;

        /* If timeouts aren't running all we can do is spin. */
        if (panicstr || devinfo_freeze) {
                /* Convert delay(9F) call into drv_usecwait(9F) call. */
                if (ticks > 0)
                        drv_usecwait(TICK_TO_USEC(ticks));
                return;
        }

        deadline = ddi_get_lbolt() + ticks;
        while ((timeleft = deadline - ddi_get_lbolt()) > 0) {
                mutex_enter(&t->t_delay_lock);
                id = timeout_default(delay_wakeup, t, timeleft);
                cv_wait(&t->t_delay_cv, &t->t_delay_lock);
                mutex_exit(&t->t_delay_lock);
                (void) untimeout_default(id, 0);
        }
}

/*
 * Delay specified number of clock ticks.
 */
void
delay(clock_t ticks)
{
        DELAY_CONTEXT_CHECK();

        delay_common(ticks);
}

/*
 * Delay a random number of clock ticks between 1 and ticks.
 */
void
delay_random(clock_t ticks)
{
        int     r;

        DELAY_CONTEXT_CHECK();

        (void) random_get_pseudo_bytes((void *)&r, sizeof (r));
        if (ticks == 0)
                ticks = 1;
        ticks = (r % ticks) + 1;
        delay_common(ticks);
}

/*
 * Like delay, but interruptible by a signal.
 */
int
delay_sig(clock_t ticks)
{
        kthread_t       *t = curthread;
        clock_t         deadline;
        clock_t         rc;

        /* If timeouts aren't running all we can do is spin. */
        if (panicstr || devinfo_freeze) {
                if (ticks > 0)
                        drv_usecwait(TICK_TO_USEC(ticks));
                return (0);
        }

        deadline = ddi_get_lbolt() + ticks;
        mutex_enter(&t->t_delay_lock);
        do {
                rc = cv_timedwait_sig(&t->t_delay_cv,
                    &t->t_delay_lock, deadline);
                /* loop until past deadline or signaled */
        } while (rc > 0);
        mutex_exit(&t->t_delay_lock);
        if (rc == 0)
                return (EINTR);
        return (0);
}


#define SECONDS_PER_DAY 86400

/*
 * Initialize the system time based on the TOD chip.  approx is used as
 * an approximation of time (e.g. from the filesystem) in the event that
 * the TOD chip has been cleared or is unresponsive.  An approx of -1
 * means the filesystem doesn't keep time.
 */
void
clkset(time_t approx)
{
        timestruc_t ts;
        int spl;
        int set_clock = 0;

        mutex_enter(&tod_lock);
        ts = tod_get();

        if (ts.tv_sec > 365 * SECONDS_PER_DAY) {
                /*
                 * If the TOD chip is reporting some time after 1971,
                 * then it probably didn't lose power or become otherwise
                 * cleared in the recent past;  check to assure that
                 * the time coming from the filesystem isn't in the future
                 * according to the TOD chip.
                 */
                if (approx != -1 && approx > ts.tv_sec) {
                        cmn_err(CE_WARN, "Last shutdown is later "
                            "than time on time-of-day chip; check date.");
                }
        } else {
                /*
                 * If the TOD chip isn't giving correct time, set it to the
                 * greater of i) approx and ii) 1987. That way if approx
                 * is negative or is earlier than 1987, we set the clock
                 * back to a time when Oliver North, ALF and Dire Straits
                 * were all on the collective brain:  1987.
                 */
                timestruc_t tmp;
                time_t diagnose_date = (1987 - 1970) * 365 * SECONDS_PER_DAY;
                ts.tv_sec = (approx > diagnose_date ? approx : diagnose_date);
                ts.tv_nsec = 0;

                /*
                 * Attempt to write the new time to the TOD chip.  Set spl high
                 * to avoid getting preempted between the tod_set and tod_get.
                 */
                spl = splhi();
                tod_set(ts);
                tmp = tod_get();
                splx(spl);

                if (tmp.tv_sec != ts.tv_sec && tmp.tv_sec != ts.tv_sec + 1) {
                        tod_broken = 1;
                        dosynctodr = 0;
                        cmn_err(CE_WARN, "Time-of-day chip unresponsive.");
                } else {
                        cmn_err(CE_WARN, "Time-of-day chip had "
                            "incorrect date; check and reset.");
                }
                set_clock = 1;
        }

        if (!boot_time) {
                boot_time = ts.tv_sec;
                global_zone->zone_boot_time = ts.tv_sec;
                set_clock = 1;
        }

        if (set_clock)
                set_hrestime(&ts);

        mutex_exit(&tod_lock);
}

int     timechanged;    /* for testing if the system time has been reset */

void
set_hrestime(timestruc_t *ts)
{
        int spl = hr_clock_lock();
        hrestime = *ts;
        membar_enter(); /* hrestime must be visible before timechanged++ */
        timedelta = 0;
        timechanged++;
        hr_clock_unlock(spl);
        callout_hrestime();
}

static uint_t deadman_seconds;
static uint32_t deadman_panics;
static int deadman_enabled = 0;
static int deadman_panic_timers = 1;

static void
deadman(void)
{
        if (panicstr) {
                /*
                 * During panic, other CPUs besides the panic
                 * master continue to handle cyclics and some other
                 * interrupts.  The code below is intended to be
                 * single threaded, so any CPU other than the master
                 * must keep out.
                 */
                if (CPU->cpu_id != panic_cpu.cpu_id)
                        return;

                if (!deadman_panic_timers)
                        return; /* allow all timers to be manually disabled */

                /*
                 * If we are generating a crash dump or syncing filesystems and
                 * the corresponding timer is set, decrement it and re-enter
                 * the panic code to abort it and advance to the next state.
                 * The panic states and triggers are explained in panic.c.
                 */
                if (panic_dump) {
                        if (dump_timeleft && (--dump_timeleft == 0)) {
                                panic("panic dump timeout");
                                /*NOTREACHED*/
                        }
                }
                return;
        }

        if (deadman_counter != CPU->cpu_deadman_counter) {
                CPU->cpu_deadman_counter = deadman_counter;
                CPU->cpu_deadman_countdown = deadman_seconds;
                return;
        }

        if (--CPU->cpu_deadman_countdown > 0)
                return;

        /*
         * Regardless of whether or not we actually bring the system down,
         * bump the deadman_panics variable.
         *
         * N.B. deadman_panics is incremented once for each CPU that
         * passes through here.  It's expected that all the CPUs will
         * detect this condition within one second of each other, so
         * when deadman_enabled is off, deadman_panics will
         * typically be a multiple of the total number of CPUs in
         * the system.
         */
        atomic_inc_32(&deadman_panics);

        if (!deadman_enabled) {
                CPU->cpu_deadman_countdown = deadman_seconds;
                return;
        }

        /*
         * If we're here, we want to bring the system down.
         */
        panic("deadman: timed out after %d seconds of clock "
            "inactivity", deadman_seconds);
        /*NOTREACHED*/
}

/*ARGSUSED*/
static void
deadman_online(void *arg, cpu_t *cpu, cyc_handler_t *hdlr, cyc_time_t *when)
{
        cpu->cpu_deadman_counter = 0;
        cpu->cpu_deadman_countdown = deadman_seconds;

        hdlr->cyh_func = (cyc_func_t)deadman;
        hdlr->cyh_level = CY_HIGH_LEVEL;
        hdlr->cyh_arg = NULL;

        /*
         * Stagger the CPUs so that they don't all run deadman() at
         * the same time.  Simplest reason to do this is to make it
         * more likely that only one CPU will panic in case of a
         * timeout.  This is (strictly speaking) an aesthetic, not a
         * technical consideration.
         */
        when->cyt_when = cpu->cpu_id * (NANOSEC / NCPU);
        when->cyt_interval = NANOSEC;
}


void
deadman_init(void)
{
        cyc_omni_handler_t hdlr;

        if (deadman_seconds == 0)
                deadman_seconds = snoop_interval / MICROSEC;

        if (snooping)
                deadman_enabled = 1;

        hdlr.cyo_online = deadman_online;
        hdlr.cyo_offline = NULL;
        hdlr.cyo_arg = NULL;

        mutex_enter(&cpu_lock);
        deadman_cyclic = cyclic_add_omni(&hdlr);
        mutex_exit(&cpu_lock);
}

/*
 * tod_fault() is for updating tod validate mechanism state:
 * (1) TOD_NOFAULT: for resetting the state to 'normal'.
 *     currently used for debugging only
 * (2) The following four cases detected by tod validate mechanism:
 *       TOD_REVERSED: current tod value is less than previous value.
 *       TOD_STALLED: current tod value hasn't advanced.
 *       TOD_JUMPED: current tod value advanced too far from previous value.
 *       TOD_RATECHANGED: the ratio between average tod delta and
 *       average tick delta has changed.
 * (3) TOD_RDONLY: when the TOD clock is not writeable e.g. because it is
 *     a virtual TOD provided by a hypervisor.
 */
enum tod_fault_type
tod_fault(enum tod_fault_type ftype, int off)
{
        ASSERT(MUTEX_HELD(&tod_lock));

        if (tod_faulted != ftype) {
                switch (ftype) {
                case TOD_NOFAULT:
                        plat_tod_fault(TOD_NOFAULT);
                        cmn_err(CE_NOTE, "Restarted tracking "
                            "Time of Day clock.");
                        tod_faulted = ftype;
                        break;
                case TOD_REVERSED:
                case TOD_JUMPED:
                        if (tod_faulted == TOD_NOFAULT) {
                                plat_tod_fault(ftype);
                                cmn_err(CE_WARN, "Time of Day clock error: "
                                    "reason [%s by 0x%x]. -- "
                                    " Stopped tracking Time Of Day clock.",
                                    tod_fault_table[ftype], off);
                                tod_faulted = ftype;
                        }
                        break;
                case TOD_STALLED:
                case TOD_RATECHANGED:
                        if (tod_faulted == TOD_NOFAULT) {
                                plat_tod_fault(ftype);
                                cmn_err(CE_WARN, "Time of Day clock error: "
                                    "reason [%s]. -- "
                                    " Stopped tracking Time Of Day clock.",
                                    tod_fault_table[ftype]);
                                tod_faulted = ftype;
                        }
                        break;
                case TOD_RDONLY:
                        if (tod_faulted == TOD_NOFAULT) {
                                plat_tod_fault(ftype);
                                cmn_err(CE_NOTE, "!Time of Day clock is "
                                    "Read-Only; set of Date/Time will not "
                                    "persist across reboot.");
                                tod_faulted = ftype;
                        }
                        break;
                default:
                        break;
                }
        }
        return (tod_faulted);
}

/*
 * Two functions that allow tod_status_flag to be manipulated by functions
 * external to this file.
 */

void
tod_status_set(int tod_flag)
{
        tod_status_flag |= tod_flag;
}

void
tod_status_clear(int tod_flag)
{
        tod_status_flag &= ~tod_flag;
}

/*
 * Record a timestamp and the value passed to tod_set().  The next call to
 * tod_validate() can use these values, prev_set_tick and prev_set_tod,
 * when checking the timestruc_t returned by tod_get().  Ordinarily,
 * tod_validate() will use prev_tick and prev_tod for this task but these
 * become obsolete, and will be re-assigned with the prev_set_* values,
 * in the case when the TOD is re-written.
 */
void
tod_set_prev(timestruc_t ts)
{
        if ((tod_validate_enable == 0) || (tod_faulted != TOD_NOFAULT) ||
            tod_validate_deferred) {
                return;
        }
        prev_set_tick = gethrtime();
        /*
         * A negative value will be set to zero in utc_to_tod() so we fake
         * a zero here in such a case.  This would need to change if the
         * behavior of utc_to_tod() changes.
         */
        prev_set_tod = ts.tv_sec < 0 ? 0 : ts.tv_sec;
}

/*
 * tod_validate() is used for checking values returned by tod_get().
 * Four error cases can be detected by this routine:
 *   TOD_REVERSED: current tod value is less than previous.
 *   TOD_STALLED: current tod value hasn't advanced.
 *   TOD_JUMPED: current tod value advanced too far from previous value.
 *   TOD_RATECHANGED: the ratio between average tod delta and
 *   average tick delta has changed.
 */
time_t
tod_validate(time_t tod)
{
        time_t diff_tod;
        hrtime_t diff_tick;

        long dtick;
        int dtick_delta;

        int off = 0;
        enum tod_fault_type tod_bad = TOD_NOFAULT;

        static int firsttime = 1;

        static time_t prev_tod = 0;
        static hrtime_t prev_tick = 0;
        static long dtick_avg = TOD_REF_FREQ;

        int cpr_resume_done = 0;
        int dr_resume_done = 0;

        hrtime_t tick = gethrtime();

        ASSERT(MUTEX_HELD(&tod_lock));

        /*
         * tod_validate_enable is patchable via /etc/system.
         * If TOD is already faulted, or if TOD validation is deferred,
         * there is nothing to do.
         */
        if ((tod_validate_enable == 0) || (tod_faulted != TOD_NOFAULT) ||
            tod_validate_deferred) {
                return (tod);
        }

        /*
         * If this is the first time through, we just need to save the tod
         * we were called with and hrtime so we can use them next time to
         * validate tod_get().
         */
        if (firsttime) {
                firsttime = 0;
                prev_tod = tod;
                prev_tick = tick;
                return (tod);
        }

        /*
         * Handle any flags that have been turned on by tod_status_set().
         * In the case where a tod_set() is done and then a subsequent
         * tod_get() fails (ie, both TOD_SET_DONE and TOD_GET_FAILED are
         * true), we treat the TOD_GET_FAILED with precedence by switching
         * off the flag, returning tod and leaving TOD_SET_DONE asserted
         * until such time as tod_get() completes successfully.
         */
        if (tod_status_flag & TOD_GET_FAILED) {
                /*
                 * tod_get() has encountered an issue, possibly transitory,
                 * when reading TOD.  We'll just return the incoming tod
                 * value (which is actually hrestime.tv_sec in this case)
                 * and when we get a genuine tod, following a successful
                 * tod_get(), we can validate using prev_tod and prev_tick.
                 */
                tod_status_flag &= ~TOD_GET_FAILED;
                return (tod);
        } else if (tod_status_flag & TOD_SET_DONE) {
                /*
                 * TOD has been modified.  Just before the TOD was written,
                 * tod_set_prev() saved tod and hrtime; we can now use
                 * those values, prev_set_tod and prev_set_tick, to validate
                 * the incoming tod that's just been read.
                 */
                prev_tod = prev_set_tod;
                prev_tick = prev_set_tick;
                dtick_avg = TOD_REF_FREQ;
                tod_status_flag &= ~TOD_SET_DONE;
                /*
                 * If a tod_set() preceded a cpr_suspend() without an
                 * intervening tod_validate(), we need to ensure that a
                 * TOD_JUMPED condition is ignored.
                 * Note this isn't a concern in the case of DR as we've
                 * just reassigned dtick_avg, above.
                 */
                if (tod_status_flag & TOD_CPR_RESUME_DONE) {
                        cpr_resume_done = 1;
                        tod_status_flag &= ~TOD_CPR_RESUME_DONE;
                }
        } else if (tod_status_flag & TOD_CPR_RESUME_DONE) {
                /*
                 * The system's coming back from a checkpoint resume.
                 */
                cpr_resume_done = 1;
                tod_status_flag &= ~TOD_CPR_RESUME_DONE;
                /*
                 * We need to handle the possibility of a CPR suspend
                 * operation having been initiated whilst a DR event was
                 * in-flight.
                 */
                if (tod_status_flag & TOD_DR_RESUME_DONE) {
                        dr_resume_done = 1;
                        tod_status_flag &= ~TOD_DR_RESUME_DONE;
                }
        } else if (tod_status_flag & TOD_DR_RESUME_DONE) {
                /*
                 * A Dynamic Reconfiguration event has taken place.
                 */
                dr_resume_done = 1;
                tod_status_flag &= ~TOD_DR_RESUME_DONE;
        }

        /* test hook */
        switch (tod_unit_test) {
        case 1: /* for testing jumping tod */
                tod += tod_test_injector;
                tod_unit_test = 0;
                break;
        case 2: /* for testing stuck tod bit */
                tod |= 1 << tod_test_injector;
                tod_unit_test = 0;
                break;
        case 3: /* for testing stalled tod */
                tod = prev_tod;
                tod_unit_test = 0;
                break;
        case 4: /* reset tod fault status */
                (void) tod_fault(TOD_NOFAULT, 0);
                tod_unit_test = 0;
                break;
        default:
                break;
        }

        diff_tod = tod - prev_tod;
        diff_tick = tick - prev_tick;

        ASSERT(diff_tick >= 0);

        if (diff_tod < 0) {
                /* ERROR - tod reversed */
                tod_bad = TOD_REVERSED;
                off = (int)(prev_tod - tod);
        } else if (diff_tod == 0) {
                /* tod did not advance */
                if (diff_tick > TOD_STALL_THRESHOLD) {
                        /* ERROR - tod stalled */
                        tod_bad = TOD_STALLED;
                } else {
                        /*
                         * Make sure we don't update prev_tick
                         * so that diff_tick is calculated since
                         * the first diff_tod == 0
                         */
                        return (tod);
                }
        } else {
                /* calculate dtick */
                dtick = diff_tick / diff_tod;

                /* update dtick averages */
                dtick_avg += ((dtick - dtick_avg) / TOD_FILTER_N);

                /*
                 * Calculate dtick_delta as
                 * variation from reference freq in quartiles
                 */
                dtick_delta = (dtick_avg - TOD_REF_FREQ) /
                    (TOD_REF_FREQ >> 2);

                /*
                 * Even with a perfectly functioning TOD device,
                 * when the number of elapsed seconds is low the
                 * algorithm can calculate a rate that is beyond
                 * tolerance, causing an error.  The algorithm is
                 * inaccurate when elapsed time is low (less than
                 * 5 seconds).
                 */
                if (diff_tod > 4) {
                        if (dtick < TOD_JUMP_THRESHOLD) {
                                /*
                                 * If we've just done a CPR resume, we detect
                                 * a jump in the TOD but, actually, what's
                                 * happened is that the TOD has been increasing
                                 * whilst the system was suspended and the tick
                                 * count hasn't kept up.  We consider the first
                                 * occurrence of this after a resume as normal
                                 * and ignore it; otherwise, in a non-resume
                                 * case, we regard it as a TOD problem.
                                 */
                                if (!cpr_resume_done) {
                                        /* ERROR - tod jumped */
                                        tod_bad = TOD_JUMPED;
                                        off = (int)diff_tod;
                                }
                        }
                        if (dtick_delta) {
                                /*
                                 * If we've just done a DR resume, dtick_avg
                                 * can go a bit askew so we reset it and carry
                                 * on; otherwise, the TOD is in error.
                                 */
                                if (dr_resume_done) {
                                        dtick_avg = TOD_REF_FREQ;
                                } else {
                                        /* ERROR - change in clock rate */
                                        tod_bad = TOD_RATECHANGED;
                                }
                        }
                }
        }

        if (tod_bad != TOD_NOFAULT) {
                (void) tod_fault(tod_bad, off);

                /*
                 * Disable dosynctodr since we are going to fault
                 * the TOD chip anyway here
                 */
                dosynctodr = 0;

                /*
                 * Set tod to the correct value from hrestime
                 */
                tod = hrestime.tv_sec;
        }

        prev_tod = tod;
        prev_tick = tick;
        return (tod);
}

static void
calcloadavg(int nrun, uint64_t *hp_ave)
{
        static int64_t f[3] = { 135, 27, 9 };
        uint_t i;
        int64_t q, r;

        /*
         * Compute load average over the last 1, 5, and 15 minutes
         * (60, 300, and 900 seconds).  The constants in f[3] are for
         * exponential decay:
         * (1 - exp(-1/60)) << 13 = 135,
         * (1 - exp(-1/300)) << 13 = 27,
         * (1 - exp(-1/900)) << 13 = 9.
         */

        /*
         * a little hoop-jumping to avoid integer overflow
         */
        for (i = 0; i < 3; i++) {
                q = (hp_ave[i]  >> 16) << 7;
                r = (hp_ave[i]  & 0xffff) << 7;
                hp_ave[i] += ((nrun - q) * f[i] - ((r * f[i]) >> 16)) >> 4;
        }
}

/*
 * lbolt_hybrid() is used by ddi_get_lbolt() and ddi_get_lbolt64() to
 * calculate the value of lbolt according to the current mode. In the event
 * driven mode (the default), lbolt is calculated by dividing the current hires
 * time by the number of nanoseconds per clock tick. In the cyclic driven mode
 * an internal variable is incremented at each firing of the lbolt cyclic
 * and returned by lbolt_cyclic_driven().
 *
 * The system will transition from event to cyclic driven mode when the number
 * of calls to lbolt_event_driven() exceeds the (per CPU) threshold within a
 * window of time. It does so by reprograming lbolt_cyclic from CY_INFINITY to
 * nsec_per_tick. The lbolt cyclic will remain ON while at least one CPU is
 * causing enough activity to cross the thresholds.
 */
int64_t
lbolt_bootstrap(void)
{
        return (0);
}

/* ARGSUSED */
uint_t
lbolt_ev_to_cyclic(caddr_t arg1, caddr_t arg2)
{
        hrtime_t ts, exp;
        int ret;

        ASSERT(lbolt_hybrid != lbolt_cyclic_driven);

        kpreempt_disable();

        ts = gethrtime();
        lb_info->lbi_internal = (ts/nsec_per_tick);

        /*
         * Align the next expiration to a clock tick boundary.
         */
        exp = ts + nsec_per_tick - 1;
        exp = (exp/nsec_per_tick) * nsec_per_tick;

        ret = cyclic_reprogram(lb_info->id.lbi_cyclic_id, exp);
        ASSERT(ret);

        lbolt_hybrid = lbolt_cyclic_driven;
        lb_info->lbi_cyc_deactivate = B_FALSE;
        lb_info->lbi_cyc_deac_start = lb_info->lbi_internal;

        kpreempt_enable();

        ret = atomic_dec_32_nv(&lb_info->lbi_token);
        ASSERT(ret == 0);

        return (1);
}

int64_t
lbolt_event_driven(void)
{
        hrtime_t ts;
        int64_t lb;
        int ret, cpu = CPU->cpu_seqid;

        ts = gethrtime();
        ASSERT(ts > 0);

        ASSERT(nsec_per_tick > 0);
        lb = (ts/nsec_per_tick);

        /*
         * Switch to cyclic mode if the number of calls to this routine
         * has reached the threshold within the interval.
         */
        if ((lb - lb_cpu[cpu].lbc_cnt_start) < lb_info->lbi_thresh_interval) {

                if (--lb_cpu[cpu].lbc_counter == 0) {
                        /*
                         * Reached the threshold within the interval, reset
                         * the usage statistics.
                         */
                        lb_cpu[cpu].lbc_counter = lb_info->lbi_thresh_calls;
                        lb_cpu[cpu].lbc_cnt_start = lb;

                        /*
                         * Make sure only one thread reprograms the
                         * lbolt cyclic and changes the mode.
                         */
                        if (panicstr == NULL &&
                            atomic_cas_32(&lb_info->lbi_token, 0, 1) == 0) {

                                if (lbolt_hybrid == lbolt_cyclic_driven) {
                                        ret = atomic_dec_32_nv(
                                            &lb_info->lbi_token);
                                        ASSERT(ret == 0);
                                } else {
                                        lbolt_softint_post();
                                }
                        }
                }
        } else {
                /*
                 * Exceeded the interval, reset the usage statistics.
                 */
                lb_cpu[cpu].lbc_counter = lb_info->lbi_thresh_calls;
                lb_cpu[cpu].lbc_cnt_start = lb;
        }

        ASSERT(lb >= lb_info->lbi_debug_time);

        return (lb - lb_info->lbi_debug_time);
}

int64_t
lbolt_cyclic_driven(void)
{
        int64_t lb = lb_info->lbi_internal;
        int cpu;

        /*
         * If a CPU has already prevented the lbolt cyclic from deactivating
         * itself, don't bother tracking the usage. Otherwise check if we're
         * within the interval and how the per CPU counter is doing.
         */
        if (lb_info->lbi_cyc_deactivate) {
                cpu = CPU->cpu_seqid;
                if ((lb - lb_cpu[cpu].lbc_cnt_start) <
                    lb_info->lbi_thresh_interval) {

                        if (lb_cpu[cpu].lbc_counter == 0)
                                /*
                                 * Reached the threshold within the interval,
                                 * prevent the lbolt cyclic from turning itself
                                 * off.
                                 */
                                lb_info->lbi_cyc_deactivate = B_FALSE;
                        else
                                lb_cpu[cpu].lbc_counter--;
                } else {
                        /*
                         * Only reset the usage statistics when we have
                         * exceeded the interval.
                         */
                        lb_cpu[cpu].lbc_counter = lb_info->lbi_thresh_calls;
                        lb_cpu[cpu].lbc_cnt_start = lb;
                }
        }

        ASSERT(lb >= lb_info->lbi_debug_time);

        return (lb - lb_info->lbi_debug_time);
}

/*
 * The lbolt_cyclic() routine will fire at a nsec_per_tick interval to satisfy
 * performance needs of ddi_get_lbolt() and ddi_get_lbolt64() consumers.
 * It is inactive by default, and will be activated when switching from event
 * to cyclic driven lbolt. The cyclic will turn itself off unless signaled
 * by lbolt_cyclic_driven().
 */
static void
lbolt_cyclic(void)
{
        int ret;

        lb_info->lbi_internal++;

        if (!lbolt_cyc_only) {

                if (lb_info->lbi_cyc_deactivate) {
                        /*
                         * Switching from cyclic to event driven mode.
                         */
                        if (panicstr == NULL &&
                            atomic_cas_32(&lb_info->lbi_token, 0, 1) == 0) {

                                if (lbolt_hybrid == lbolt_event_driven) {
                                        ret = atomic_dec_32_nv(
                                            &lb_info->lbi_token);
                                        ASSERT(ret == 0);
                                        return;
                                }

                                kpreempt_disable();

                                lbolt_hybrid = lbolt_event_driven;
                                ret = cyclic_reprogram(
                                    lb_info->id.lbi_cyclic_id,
                                    CY_INFINITY);
                                ASSERT(ret);

                                kpreempt_enable();

                                ret = atomic_dec_32_nv(&lb_info->lbi_token);
                                ASSERT(ret == 0);
                        }
                }

                /*
                 * The lbolt cyclic should not try to deactivate itself before
                 * the sampling period has elapsed.
                 */
                if (lb_info->lbi_internal - lb_info->lbi_cyc_deac_start >=
                    lb_info->lbi_thresh_interval) {
                        lb_info->lbi_cyc_deactivate = B_TRUE;
                        lb_info->lbi_cyc_deac_start = lb_info->lbi_internal;
                }
        }
}

/*
 * Since the lbolt service was historically cyclic driven, it must be 'stopped'
 * when the system drops into the kernel debugger. lbolt_debug_entry() is
 * called by the KDI system claim callbacks to record a hires timestamp at
 * debug enter time. lbolt_debug_return() is called by the sistem release
 * callbacks to account for the time spent in the debugger. The value is then
 * accumulated in the lb_info structure and used by lbolt_event_driven() and
 * lbolt_cyclic_driven(), as well as the mdb_get_lbolt() routine.
 */
void
lbolt_debug_entry(void)
{
        if (lbolt_hybrid != lbolt_bootstrap) {
                ASSERT(lb_info != NULL);
                lb_info->lbi_debug_ts = gethrtime();
        }
}

/*
 * Calculate the time spent in the debugger and add it to the lbolt info
 * structure. We also update the internal lbolt value in case we were in
 * cyclic driven mode going in.
 */
void
lbolt_debug_return(void)
{
        hrtime_t ts;

        if (lbolt_hybrid != lbolt_bootstrap) {
                ASSERT(lb_info != NULL);
                ASSERT(nsec_per_tick > 0);

                ts = gethrtime();
                lb_info->lbi_internal = (ts/nsec_per_tick);
                lb_info->lbi_debug_time +=
                    ((ts - lb_info->lbi_debug_ts)/nsec_per_tick);

                lb_info->lbi_debug_ts = 0;
        }
}