FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_clock.c

     /*
      * Copyright (c) 2003,2004 The DragonFly Project.  All rights reserved.
      * 
      * This code is derived from software contributed to The DragonFly Project
      * by Matthew Dillon <dillon@backplane.com>
      * 
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in
     *    the documentation and/or other materials provided with the
     *    distribution.
     * 3. Neither the name of The DragonFly Project nor the names of its
     *    contributors may be used to endorse or promote products derived
     *    from this software without specific, prior written permission.
     * 
     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
     * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
     * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     * 
     * Copyright (c) 1997, 1998 Poul-Henning Kamp <phk@FreeBSD.org>
     * Copyright (c) 1982, 1986, 1991, 1993
     *      The Regents of the University of California.  All rights reserved.
     * (c) UNIX System Laboratories, Inc.
     * All or some portions of this file are derived from material licensed
     * to the University of California by American Telephone and Telegraph
     * Co. or Unix System Laboratories, Inc. and are reproduced herein with
     * the permission of UNIX System Laboratories, Inc.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)kern_clock.c        8.5 (Berkeley) 1/21/94
     * $FreeBSD: src/sys/kern/kern_clock.c,v 1.105.2.10 2002/10/17 13:19:40 maxim Exp $
     */
    
    #include "opt_ntp.h"
    #include "opt_ifpoll.h"
    #include "opt_pctrack.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/callout.h>
    #include <sys/kernel.h>
    #include <sys/kinfo.h>
    #include <sys/proc.h>
    #include <sys/malloc.h>
    #include <sys/resource.h>
    #include <sys/resourcevar.h>
    #include <sys/signalvar.h>
    #include <sys/timex.h>
    #include <sys/timepps.h>
    #include <vm/vm.h>
    #include <sys/lock.h>
    #include <vm/pmap.h>
    #include <vm/vm_map.h>
    #include <vm/vm_extern.h>
    #include <sys/sysctl.h>
    
    #include <sys/thread2.h>
    
    #include <machine/cpu.h>
    #include <machine/limits.h>
    #include <machine/smp.h>
    #include <machine/cpufunc.h>
   #include <machine/specialreg.h>
   #include <machine/clock.h>
   
   #ifdef GPROF
   #include <sys/gmon.h>
   #endif
   
   #ifdef IFPOLL_ENABLE
   extern void ifpoll_init_pcpu(int);
   #endif
   
   #ifdef DEBUG_PCTRACK
   static void do_pctrack(struct intrframe *frame, int which);
   #endif
   
   static void initclocks (void *dummy);
   SYSINIT(clocks, SI_BOOT2_CLOCKS, SI_ORDER_FIRST, initclocks, NULL)
   
   /*
    * Some of these don't belong here, but it's easiest to concentrate them.
    * Note that cpu_time counts in microseconds, but most userland programs
    * just compare relative times against the total by delta.
    */
   struct kinfo_cputime cputime_percpu[MAXCPU];
   #ifdef DEBUG_PCTRACK
   struct kinfo_pcheader cputime_pcheader = { PCTRACK_SIZE, PCTRACK_ARYSIZE };
   struct kinfo_pctrack cputime_pctrack[MAXCPU][PCTRACK_SIZE];
   #endif
   
   static int
   sysctl_cputime(SYSCTL_HANDLER_ARGS)
   {
           int cpu, error = 0;
           size_t size = sizeof(struct kinfo_cputime);
   
           for (cpu = 0; cpu < ncpus; ++cpu) {
                   if ((error = SYSCTL_OUT(req, &cputime_percpu[cpu], size)))
                           break;
           }
   
           return (error);
   }
   SYSCTL_PROC(_kern, OID_AUTO, cputime, (CTLTYPE_OPAQUE|CTLFLAG_RD), 0, 0,
           sysctl_cputime, "S,kinfo_cputime", "CPU time statistics");
   
   static int
   sysctl_cp_time(SYSCTL_HANDLER_ARGS)
   {
           long cpu_states[5] = {0};
           int cpu, error = 0;
           size_t size = sizeof(cpu_states);
   
           for (cpu = 0; cpu < ncpus; ++cpu) {
                   cpu_states[CP_USER] += cputime_percpu[cpu].cp_user;
                   cpu_states[CP_NICE] += cputime_percpu[cpu].cp_nice;
                   cpu_states[CP_SYS] += cputime_percpu[cpu].cp_sys;
                   cpu_states[CP_INTR] += cputime_percpu[cpu].cp_intr;
                   cpu_states[CP_IDLE] += cputime_percpu[cpu].cp_idle;
           }
   
           error = SYSCTL_OUT(req, cpu_states, size);
   
           return (error);
   }
   
   SYSCTL_PROC(_kern, OID_AUTO, cp_time, (CTLTYPE_LONG|CTLFLAG_RD), 0, 0,
           sysctl_cp_time, "LU", "CPU time statistics");
   
   /*
    * boottime is used to calculate the 'real' uptime.  Do not confuse this with
    * microuptime().  microtime() is not drift compensated.  The real uptime
    * with compensation is nanotime() - bootime.  boottime is recalculated
    * whenever the real time is set based on the compensated elapsed time
    * in seconds (gd->gd_time_seconds).
    *
    * The gd_time_seconds and gd_cpuclock_base fields remain fairly monotonic.
    * Slight adjustments to gd_cpuclock_base are made to phase-lock it to
    * the real time.
    */
   struct timespec boottime;       /* boot time (realtime) for reference only */
   time_t time_second;             /* read-only 'passive' uptime in seconds */
   time_t time_uptime;             /* read-only 'passive' uptime in seconds */
   
   /*
    * basetime is used to calculate the compensated real time of day.  The
    * basetime can be modified on a per-tick basis by the adjtime(), 
    * ntp_adjtime(), and sysctl-based time correction APIs.
    *
    * Note that frequency corrections can also be made by adjusting
    * gd_cpuclock_base.
    *
    * basetime is a tail-chasing FIFO, updated only by cpu #0.  The FIFO is
    * used on both SMP and UP systems to avoid MP races between cpu's and
    * interrupt races on UP systems.
    */
   #define BASETIME_ARYSIZE        16
   #define BASETIME_ARYMASK        (BASETIME_ARYSIZE - 1)
   static struct timespec basetime[BASETIME_ARYSIZE];
   static volatile int basetime_index;
   
   static int
   sysctl_get_basetime(SYSCTL_HANDLER_ARGS)
   {
           struct timespec *bt;
           int error;
           int index;
   
           /*
            * Because basetime data and index may be updated by another cpu,
            * a load fence is required to ensure that the data we read has
            * not been speculatively read relative to a possibly updated index.
            */
           index = basetime_index;
           cpu_lfence();
           bt = &basetime[index];
           error = SYSCTL_OUT(req, bt, sizeof(*bt));
           return (error);
   }
   
   SYSCTL_STRUCT(_kern, KERN_BOOTTIME, boottime, CTLFLAG_RD,
       &boottime, timespec, "System boottime");
   SYSCTL_PROC(_kern, OID_AUTO, basetime, CTLTYPE_STRUCT|CTLFLAG_RD, 0, 0,
       sysctl_get_basetime, "S,timespec", "System basetime");
   
   static void hardclock(systimer_t info, int, struct intrframe *frame);
   static void statclock(systimer_t info, int, struct intrframe *frame);
   static void schedclock(systimer_t info, int, struct intrframe *frame);
   static void getnanotime_nbt(struct timespec *nbt, struct timespec *tsp);
   
   int     ticks;                  /* system master ticks at hz */
   int     clocks_running;         /* tsleep/timeout clocks operational */
   int64_t nsec_adj;               /* ntpd per-tick adjustment in nsec << 32 */
   int64_t nsec_acc;               /* accumulator */
   int     sched_ticks;            /* global schedule clock ticks */
   
   /* NTPD time correction fields */
   int64_t ntp_tick_permanent;     /* per-tick adjustment in nsec << 32 */
   int64_t ntp_tick_acc;           /* accumulator for per-tick adjustment */
   int64_t ntp_delta;              /* one-time correction in nsec */
   int64_t ntp_big_delta = 1000000000;
   int32_t ntp_tick_delta;         /* current adjustment rate */
   int32_t ntp_default_tick_delta; /* adjustment rate for ntp_delta */
   time_t  ntp_leap_second;        /* time of next leap second */
   int     ntp_leap_insert;        /* whether to insert or remove a second */
   
   /*
    * Finish initializing clock frequencies and start all clocks running.
    */
   /* ARGSUSED*/
   static void
   initclocks(void *dummy)
   {
           /*psratio = profhz / stathz;*/
           initclocks_pcpu();
           clocks_running = 1;
   }
   
   /*
    * Called on a per-cpu basis
    */
   void
   initclocks_pcpu(void)
   {
           struct globaldata *gd = mycpu;
   
           crit_enter();
           if (gd->gd_cpuid == 0) {
               gd->gd_time_seconds = 1;
               gd->gd_cpuclock_base = sys_cputimer->count();
           } else {
               /* XXX */
               gd->gd_time_seconds = globaldata_find(0)->gd_time_seconds;
               gd->gd_cpuclock_base = globaldata_find(0)->gd_cpuclock_base;
           }
   
           systimer_intr_enable();
   
   #ifdef IFPOLL_ENABLE
           ifpoll_init_pcpu(gd->gd_cpuid);
   #endif
   
           /*
            * Use a non-queued periodic systimer to prevent multiple ticks from
            * building up if the sysclock jumps forward (8254 gets reset).  The
            * sysclock will never jump backwards.  Our time sync is based on
            * the actual sysclock, not the ticks count.
            */
           systimer_init_periodic_nq(&gd->gd_hardclock, hardclock, NULL, hz);
           systimer_init_periodic_nq(&gd->gd_statclock, statclock, NULL, stathz);
           /* XXX correct the frequency for scheduler / estcpu tests */
           systimer_init_periodic_nq(&gd->gd_schedclock, schedclock, 
                                   NULL, ESTCPUFREQ); 
           crit_exit();
   }
   
   /*
    * This sets the current real time of day.  Timespecs are in seconds and
    * nanoseconds.  We do not mess with gd_time_seconds and gd_cpuclock_base,
    * instead we adjust basetime so basetime + gd_* results in the current
    * time of day.  This way the gd_* fields are guarenteed to represent
    * a monotonically increasing 'uptime' value.
    *
    * When set_timeofday() is called from userland, the system call forces it
    * onto cpu #0 since only cpu #0 can update basetime_index.
    */
   void
   set_timeofday(struct timespec *ts)
   {
           struct timespec *nbt;
           int ni;
   
           /*
            * XXX SMP / non-atomic basetime updates
            */
           crit_enter();
           ni = (basetime_index + 1) & BASETIME_ARYMASK;
           nbt = &basetime[ni];
           nanouptime(nbt);
           nbt->tv_sec = ts->tv_sec - nbt->tv_sec;
           nbt->tv_nsec = ts->tv_nsec - nbt->tv_nsec;
           if (nbt->tv_nsec < 0) {
               nbt->tv_nsec += 1000000000;
               --nbt->tv_sec;
           }
   
           /*
            * Note that basetime diverges from boottime as the clock drift is
            * compensated for, so we cannot do away with boottime.  When setting
            * the absolute time of day the drift is 0 (for an instant) and we
            * can simply assign boottime to basetime.  
            *
            * Note that nanouptime() is based on gd_time_seconds which is drift
            * compensated up to a point (it is guarenteed to remain monotonically
            * increasing).  gd_time_seconds is thus our best uptime guess and
            * suitable for use in the boottime calculation.  It is already taken
            * into account in the basetime calculation above.
            */
           boottime.tv_sec = nbt->tv_sec;
           ntp_delta = 0;
   
           /*
            * We now have a new basetime, make sure all other cpus have it,
            * then update the index.
            */
           cpu_sfence();
           basetime_index = ni;
   
           crit_exit();
   }
           
   /*
    * Each cpu has its own hardclock, but we only increments ticks and softticks
    * on cpu #0.
    *
    * NOTE! systimer! the MP lock might not be held here.  We can only safely
    * manipulate objects owned by the current cpu.
    */
   static void
   hardclock(systimer_t info, int in_ipi __unused, struct intrframe *frame)
   {
           sysclock_t cputicks;
           struct proc *p;
           struct globaldata *gd = mycpu;
   
           /*
            * Realtime updates are per-cpu.  Note that timer corrections as
            * returned by microtime() and friends make an additional adjustment
            * using a system-wise 'basetime', but the running time is always
            * taken from the per-cpu globaldata area.  Since the same clock
            * is distributing (XXX SMP) to all cpus, the per-cpu timebases
            * stay in synch.
            *
            * Note that we never allow info->time (aka gd->gd_hardclock.time)
            * to reverse index gd_cpuclock_base, but that it is possible for
            * it to temporarily get behind in the seconds if something in the
            * system locks interrupts for a long period of time.  Since periodic
            * timers count events, though everything should resynch again
            * immediately.
            */
           cputicks = info->time - gd->gd_cpuclock_base;
           if (cputicks >= sys_cputimer->freq) {
                   ++gd->gd_time_seconds;
                   gd->gd_cpuclock_base += sys_cputimer->freq;
                   if (gd->gd_cpuid == 0)
                           ++time_uptime;  /* uncorrected monotonic 1-sec gran */
           }
   
           /*
            * The system-wide ticks counter and NTP related timedelta/tickdelta
            * adjustments only occur on cpu #0.  NTP adjustments are accomplished
            * by updating basetime.
            */
           if (gd->gd_cpuid == 0) {
               struct timespec *nbt;
               struct timespec nts;
               int leap;
               int ni;
   
               ++ticks;
   
   #if 0
               if (tco->tc_poll_pps) 
                   tco->tc_poll_pps(tco);
   #endif
   
               /*
                * Calculate the new basetime index.  We are in a critical section
                * on cpu #0 and can safely play with basetime_index.  Start
                * with the current basetime and then make adjustments.
                */
               ni = (basetime_index + 1) & BASETIME_ARYMASK;
               nbt = &basetime[ni];
               *nbt = basetime[basetime_index];
   
               /*
                * Apply adjtime corrections.  (adjtime() API)
                *
                * adjtime() only runs on cpu #0 so our critical section is
                * sufficient to access these variables.
                */
               if (ntp_delta != 0) {
                   nbt->tv_nsec += ntp_tick_delta;
                   ntp_delta -= ntp_tick_delta;
                   if ((ntp_delta > 0 && ntp_delta < ntp_tick_delta) ||
                       (ntp_delta < 0 && ntp_delta > ntp_tick_delta)) {
                           ntp_tick_delta = ntp_delta;
                   }
               }
   
               /*
                * Apply permanent frequency corrections.  (sysctl API)
                */
               if (ntp_tick_permanent != 0) {
                   ntp_tick_acc += ntp_tick_permanent;
                   if (ntp_tick_acc >= (1LL << 32)) {
                       nbt->tv_nsec += ntp_tick_acc >> 32;
                       ntp_tick_acc -= (ntp_tick_acc >> 32) << 32;
                   } else if (ntp_tick_acc <= -(1LL << 32)) {
                       /* Negate ntp_tick_acc to avoid shifting the sign bit. */
                       nbt->tv_nsec -= (-ntp_tick_acc) >> 32;
                       ntp_tick_acc += ((-ntp_tick_acc) >> 32) << 32;
                   }
               }
   
               if (nbt->tv_nsec >= 1000000000) {
                       nbt->tv_sec++;
                       nbt->tv_nsec -= 1000000000;
               } else if (nbt->tv_nsec < 0) {
                       nbt->tv_sec--;
                       nbt->tv_nsec += 1000000000;
               }
   
               /*
                * Another per-tick compensation.  (for ntp_adjtime() API)
                */
               if (nsec_adj != 0) {
                   nsec_acc += nsec_adj;
                   if (nsec_acc >= 0x100000000LL) {
                       nbt->tv_nsec += nsec_acc >> 32;
                       nsec_acc = (nsec_acc & 0xFFFFFFFFLL);
                   } else if (nsec_acc <= -0x100000000LL) {
                       nbt->tv_nsec -= -nsec_acc >> 32;
                       nsec_acc = -(-nsec_acc & 0xFFFFFFFFLL);
                   }
                   if (nbt->tv_nsec >= 1000000000) {
                       nbt->tv_nsec -= 1000000000;
                       ++nbt->tv_sec;
                   } else if (nbt->tv_nsec < 0) {
                       nbt->tv_nsec += 1000000000;
                       --nbt->tv_sec;
                   }
               }
   
               /************************************************************
                *                  LEAP SECOND CORRECTION                  *
                ************************************************************
                *
                * Taking into account all the corrections made above, figure
                * out the new real time.  If the seconds field has changed
                * then apply any pending leap-second corrections.
                */
               getnanotime_nbt(nbt, &nts);
   
               if (time_second != nts.tv_sec) {
                   /*
                    * Apply leap second (sysctl API).  Adjust nts for changes
                    * so we do not have to call getnanotime_nbt again.
                    */
                   if (ntp_leap_second) {
                       if (ntp_leap_second == nts.tv_sec) {
                           if (ntp_leap_insert) {
                               nbt->tv_sec++;
                               nts.tv_sec++;
                           } else {
                               nbt->tv_sec--;
                               nts.tv_sec--;
                           }
                           ntp_leap_second--;
                       }
                   }
   
                   /*
                    * Apply leap second (ntp_adjtime() API), calculate a new
                    * nsec_adj field.  ntp_update_second() returns nsec_adj
                    * as a per-second value but we need it as a per-tick value.
                    */
                   leap = ntp_update_second(time_second, &nsec_adj);
                   nsec_adj /= hz;
                   nbt->tv_sec += leap;
                   nts.tv_sec += leap;
   
                   /*
                    * Update the time_second 'approximate time' global.
                    */
                   time_second = nts.tv_sec;
               }
   
               /*
                * Finally, our new basetime is ready to go live!
                */
               cpu_sfence();
               basetime_index = ni;
           }
   
           /*
            * lwkt thread scheduler fair queueing
            */
           lwkt_schedulerclock(curthread);
   
           /*
            * softticks are handled for all cpus
            */
           hardclock_softtick(gd);
   
           /*
            * ITimer handling is per-tick, per-cpu.
            *
            * We must acquire the per-process token in order for ksignal()
            * to be non-blocking.  For the moment this requires an AST fault,
            * the ksignal() cannot be safely issued from this hard interrupt.
            *
            * XXX Even the trytoken here isn't right, and itimer operation in
            *     a multi threaded environment is going to be weird at the
            *     very least.
            */
           if ((p = curproc) != NULL && lwkt_trytoken(&p->p_token)) {
                   crit_enter_hard();
                   if (frame && CLKF_USERMODE(frame) &&
                       timevalisset(&p->p_timer[ITIMER_VIRTUAL].it_value) &&
                       itimerdecr(&p->p_timer[ITIMER_VIRTUAL], ustick) == 0) {
                           p->p_flags |= P_SIGVTALRM;
                           need_user_resched();
                   }
                   if (timevalisset(&p->p_timer[ITIMER_PROF].it_value) &&
                       itimerdecr(&p->p_timer[ITIMER_PROF], ustick) == 0) {
                           p->p_flags |= P_SIGPROF;
                           need_user_resched();
                   }
                   crit_exit_hard();
                   lwkt_reltoken(&p->p_token);
           }
           setdelayed();
   }
   
   /*
    * The statistics clock typically runs at a 125Hz rate, and is intended
    * to be frequency offset from the hardclock (typ 100Hz).  It is per-cpu.
    *
    * NOTE! systimer! the MP lock might not be held here.  We can only safely
    * manipulate objects owned by the current cpu.
    *
    * The stats clock is responsible for grabbing a profiling sample.
    * Most of the statistics are only used by user-level statistics programs.
    * The main exceptions are p->p_uticks, p->p_sticks, p->p_iticks, and
    * p->p_estcpu.
    *
    * Like the other clocks, the stat clock is called from what is effectively
    * a fast interrupt, so the context should be the thread/process that got
    * interrupted.
    */
   static void
   statclock(systimer_t info, int in_ipi, struct intrframe *frame)
   {
   #ifdef GPROF
           struct gmonparam *g;
           int i;
   #endif
           thread_t td;
           struct proc *p;
           int bump;
           struct timeval tv;
           struct timeval *stv;
   
           /*
            * How big was our timeslice relative to the last time?
            */
           microuptime(&tv);       /* mpsafe */
           stv = &mycpu->gd_stattv;
           if (stv->tv_sec == 0) {
               bump = 1;
           } else {
               bump = tv.tv_usec - stv->tv_usec +
                   (tv.tv_sec - stv->tv_sec) * 1000000;
               if (bump < 0)
                   bump = 0;
               if (bump > 1000000)
                   bump = 1000000;
           }
           *stv = tv;
   
           td = curthread;
           p = td->td_proc;
   
           if (frame && CLKF_USERMODE(frame)) {
                   /*
                    * Came from userland, handle user time and deal with
                    * possible process.
                    */
                   if (p && (p->p_flags & P_PROFIL))
                           addupc_intr(p, CLKF_PC(frame), 1);
                   td->td_uticks += bump;
   
                   /*
                    * Charge the time as appropriate
                    */
                   if (p && p->p_nice > NZERO)
                           cpu_time.cp_nice += bump;
                   else
                           cpu_time.cp_user += bump;
           } else {
                   int intr_nest = mycpu->gd_intr_nesting_level;
   
                   if (in_ipi) {
                           /*
                            * IPI processing code will bump gd_intr_nesting_level
                            * up by one, which breaks following CLKF_INTR testing,
                            * so we substract it by one here.
                            */
                           --intr_nest;
                   }
   #ifdef GPROF
                   /*
                    * Kernel statistics are just like addupc_intr, only easier.
                    */
                   g = &_gmonparam;
                   if (g->state == GMON_PROF_ON && frame) {
                           i = CLKF_PC(frame) - g->lowpc;
                           if (i < g->textsize) {
                                   i /= HISTFRACTION * sizeof(*g->kcount);
                                   g->kcount[i]++;
                           }
                   }
   #endif
   
   #define IS_INTR_RUNNING ((frame && CLKF_INTR(intr_nest)) || CLKF_INTR_TD(td))
   
                   /*
                    * Came from kernel mode, so we were:
                    * - handling an interrupt,
                    * - doing syscall or trap work on behalf of the current
                    *   user process, or
                    * - spinning in the idle loop.
                    * Whichever it is, charge the time as appropriate.
                    * Note that we charge interrupts to the current process,
                    * regardless of whether they are ``for'' that process,
                    * so that we know how much of its real time was spent
                    * in ``non-process'' (i.e., interrupt) work.
                    *
                    * XXX assume system if frame is NULL.  A NULL frame 
                    * can occur if ipi processing is done from a crit_exit().
                    */
                   if (IS_INTR_RUNNING)
                           td->td_iticks += bump;
                   else
                           td->td_sticks += bump;
   
                   if (IS_INTR_RUNNING) {
                           /*
                            * If we interrupted an interrupt thread, well,
                            * count it as interrupt time.
                            */
   #ifdef DEBUG_PCTRACK
                           if (frame)
                                   do_pctrack(frame, PCTRACK_INT);
   #endif
                           cpu_time.cp_intr += bump;
                   } else {
                           if (td == &mycpu->gd_idlethread) {
                                   /*
                                    * Even if the current thread is the idle
                                    * thread it could be due to token contention
                                    * in the LWKT scheduler.  Count such as
                                    * system time.
                                    */
                                   if (mycpu->gd_reqflags & RQF_AST_LWKT_RESCHED)
                                           cpu_time.cp_sys += bump;
                                   else
                                           cpu_time.cp_idle += bump;
                           } else {
                                   /*
                                    * System thread was running.
                                    */
   #ifdef DEBUG_PCTRACK
                                   if (frame)
                                           do_pctrack(frame, PCTRACK_SYS);
   #endif
                                   cpu_time.cp_sys += bump;
                           }
                   }
   
   #undef IS_INTR_RUNNING
           }
   }
   
   #ifdef DEBUG_PCTRACK
   /*
    * Sample the PC when in the kernel or in an interrupt.  User code can
    * retrieve the information and generate a histogram or other output.
    */
   
   static void
   do_pctrack(struct intrframe *frame, int which)
   {
           struct kinfo_pctrack *pctrack;
   
           pctrack = &cputime_pctrack[mycpu->gd_cpuid][which];
           pctrack->pc_array[pctrack->pc_index & PCTRACK_ARYMASK] = 
                   (void *)CLKF_PC(frame);
           ++pctrack->pc_index;
   }
   
   static int
   sysctl_pctrack(SYSCTL_HANDLER_ARGS)
   {
           struct kinfo_pcheader head;
           int error;
           int cpu;
           int ntrack;
   
           head.pc_ntrack = PCTRACK_SIZE;
           head.pc_arysize = PCTRACK_ARYSIZE;
   
           if ((error = SYSCTL_OUT(req, &head, sizeof(head))) != 0)
                   return (error);
   
           for (cpu = 0; cpu < ncpus; ++cpu) {
                   for (ntrack = 0; ntrack < PCTRACK_SIZE; ++ntrack) {
                           error = SYSCTL_OUT(req, &cputime_pctrack[cpu][ntrack],
                                              sizeof(struct kinfo_pctrack));
                           if (error)
                                   break;
                   }
                   if (error)
                           break;
           }
           return (error);
   }
   SYSCTL_PROC(_kern, OID_AUTO, pctrack, (CTLTYPE_OPAQUE|CTLFLAG_RD), 0, 0,
           sysctl_pctrack, "S,kinfo_pcheader", "CPU PC tracking");
   
   #endif
   
   /*
    * The scheduler clock typically runs at a 50Hz rate.  NOTE! systimer,
    * the MP lock might not be held.  We can safely manipulate parts of curproc
    * but that's about it.
    *
    * Each cpu has its own scheduler clock.
    */
   static void
   schedclock(systimer_t info, int in_ipi __unused, struct intrframe *frame)
   {
           struct lwp *lp;
           struct rusage *ru;
           struct vmspace *vm;
           long rss;
   
           if ((lp = lwkt_preempted_proc()) != NULL) {
                   /*
                    * Account for cpu time used and hit the scheduler.  Note
                    * that this call MUST BE MP SAFE, and the BGL IS NOT HELD
                    * HERE.
                    */
                   ++lp->lwp_cpticks;
                   usched_schedulerclock(lp, info->periodic, info->time);
           } else {
                   usched_schedulerclock(NULL, info->periodic, info->time);
           }
           if ((lp = curthread->td_lwp) != NULL) {
                   /*
                    * Update resource usage integrals and maximums.
                    */
                   if ((ru = &lp->lwp_proc->p_ru) &&
                       (vm = lp->lwp_proc->p_vmspace) != NULL) {
                           ru->ru_ixrss += pgtok(vm->vm_tsize);
                           ru->ru_idrss += pgtok(vm->vm_dsize);
                           ru->ru_isrss += pgtok(vm->vm_ssize);
                           if (lwkt_trytoken(&vm->vm_map.token)) {
                                   rss = pgtok(vmspace_resident_count(vm));
                                   if (ru->ru_maxrss < rss)
                                           ru->ru_maxrss = rss;
                                   lwkt_reltoken(&vm->vm_map.token);
                           }
                   }
           }
           /* Increment the global sched_ticks */
           if (mycpu->gd_cpuid == 0)
                   ++sched_ticks;
   }
   
   /*
    * Compute number of ticks for the specified amount of time.  The 
    * return value is intended to be used in a clock interrupt timed
    * operation and guarenteed to meet or exceed the requested time.
    * If the representation overflows, return INT_MAX.  The minimum return
    * value is 1 ticks and the function will average the calculation up.
    * If any value greater then 0 microseconds is supplied, a value
    * of at least 2 will be returned to ensure that a near-term clock
    * interrupt does not cause the timeout to occur (degenerately) early.
    *
    * Note that limit checks must take into account microseconds, which is
    * done simply by using the smaller signed long maximum instead of
    * the unsigned long maximum.
    *
    * If ints have 32 bits, then the maximum value for any timeout in
    * 10ms ticks is 248 days.
    */
   int
   tvtohz_high(struct timeval *tv)
   {
           int ticks;
           long sec, usec;
   
           sec = tv->tv_sec;
           usec = tv->tv_usec;
           if (usec < 0) {
                   sec--;
                   usec += 1000000;
           }
           if (sec < 0) {
   #ifdef DIAGNOSTIC
                   if (usec > 0) {
                           sec++;
                           usec -= 1000000;
                   }
                   kprintf("tvtohz_high: negative time difference "
                           "%ld sec %ld usec\n",
                           sec, usec);
   #endif
                   ticks = 1;
           } else if (sec <= INT_MAX / hz) {
                   ticks = (int)(sec * hz + 
                               ((u_long)usec + (ustick - 1)) / ustick) + 1;
           } else {
                   ticks = INT_MAX;
           }
           return (ticks);
   }
   
   int
   tstohz_high(struct timespec *ts)
   {
           int ticks;
           long sec, nsec;
   
           sec = ts->tv_sec;
           nsec = ts->tv_nsec;
           if (nsec < 0) {
                   sec--;
                   nsec += 1000000000;
           }
           if (sec < 0) {
   #ifdef DIAGNOSTIC
                   if (nsec > 0) {
                           sec++;
                           nsec -= 1000000000;
                   }
                   kprintf("tstohz_high: negative time difference "
                           "%ld sec %ld nsec\n",
                           sec, nsec);
   #endif
                   ticks = 1;
           } else if (sec <= INT_MAX / hz) {
                   ticks = (int)(sec * hz +
                               ((u_long)nsec + (nstick - 1)) / nstick) + 1;
           } else {
                   ticks = INT_MAX;
           }
           return (ticks);
   }
   
   
   /*
    * Compute number of ticks for the specified amount of time, erroring on
    * the side of it being too low to ensure that sleeping the returned number
    * of ticks will not result in a late return.
    *
    * The supplied timeval may not be negative and should be normalized.  A
    * return value of 0 is possible if the timeval converts to less then
    * 1 tick.
    *
    * If ints have 32 bits, then the maximum value for any timeout in
    * 10ms ticks is 248 days.
    */
   int
   tvtohz_low(struct timeval *tv)
   {
           int ticks;
           long sec;
   
           sec = tv->tv_sec;
           if (sec <= INT_MAX / hz)
                   ticks = (int)(sec * hz + (u_long)tv->tv_usec / ustick);
           else
                   ticks = INT_MAX;
           return (ticks);
   }
   
   int
   tstohz_low(struct timespec *ts)
   {
           int ticks;
           long sec;
   
           sec = ts->tv_sec;
           if (sec <= INT_MAX / hz)
                   ticks = (int)(sec * hz + (u_long)ts->tv_nsec / nstick);
           else
                   ticks = INT_MAX;
           return (ticks);
   }
   
   /*
    * Start profiling on a process.
    *
    * Kernel profiling passes proc0 which never exits and hence
    * keeps the profile clock running constantly.
    */
   void
   startprofclock(struct proc *p)
   {
           if ((p->p_flags & P_PROFIL) == 0) {
                   p->p_flags |= P_PROFIL;
   #if 0   /* XXX */
                   if (++profprocs == 1 && stathz != 0) {
                           crit_enter();
                           psdiv = psratio;
                           setstatclockrate(profhz);
                           crit_exit();
                   }
   #endif
           }
   }
   
   /*
    * Stop profiling on a process.
    *
    * caller must hold p->p_token
    */
   void
   stopprofclock(struct proc *p)
   {
           if (p->p_flags & P_PROFIL) {
                   p->p_flags &= ~P_PROFIL;
   #if 0   /* XXX */
                   if (--profprocs == 0 && stathz != 0) {
                           crit_enter();
                           psdiv = 1;
                           setstatclockrate(stathz);
                           crit_exit();
                   }
   #endif
           }
   }
   
   /*
    * Return information about system clocks.
    */
   static int
   sysctl_kern_clockrate(SYSCTL_HANDLER_ARGS)
   {
           struct kinfo_clockinfo clkinfo;
           /*
            * Construct clockinfo structure.
            */
           clkinfo.ci_hz = hz;
           clkinfo.ci_tick = ustick;
           clkinfo.ci_tickadj = ntp_default_tick_delta / 1000;
           clkinfo.ci_profhz = profhz;
           clkinfo.ci_stathz = stathz ? stathz : hz;
           return (sysctl_handle_opaque(oidp, &clkinfo, sizeof clkinfo, req));
   }
   
   SYSCTL_PROC(_kern, KERN_CLOCKRATE, clockrate, CTLTYPE_STRUCT|CTLFLAG_RD,
           0, 0, sysctl_kern_clockrate, "S,clockinfo","");
   
   /*
    * We have eight functions for looking at the clock, four for
    * microseconds and four for nanoseconds.  For each there is fast
    * but less precise version "get{nano|micro}[up]time" which will
   * return a time which is up to 1/HZ previous to the call, whereas
   * the raw version "{nano|micro}[up]time" will return a timestamp
   * which is as precise as possible.  The "up" variants return the
   * time relative to system boot, these are well suited for time
   * interval measurements.
   *
   * Each cpu independantly maintains the current time of day, so all
   * we need to do to protect ourselves from changes is to do a loop
   * check on the seconds field changing out from under us.
   *
   * The system timer maintains a 32 bit count and due to various issues
   * it is possible for the calculated delta to occassionally exceed
   * sys_cputimer->freq.  If this occurs the sys_cputimer->freq64_nsec
   * multiplication can easily overflow, so we deal with the case.  For
   * uniformity we deal with the case in the usec case too.
   *
   * All the [get][micro,nano][time,uptime]() routines are MPSAFE.
   */
  void
  getmicrouptime(struct timeval *tvp)
  {
          struct globaldata *gd = mycpu;
          sysclock_t delta;
  
          do {
                  tvp->tv_sec = gd->gd_time_seconds;
                  delta = gd->gd_hardclock.time - gd->gd_cpuclock_base;
          } while (tvp->tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  tvp->tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          tvp->tv_usec = (sys_cputimer->freq64_usec * delta) >> 32;
          if (tvp->tv_usec >= 1000000) {
                  tvp->tv_usec -= 1000000;
                  ++tvp->tv_sec;
          }
  }
  
  void
  getnanouptime(struct timespec *tsp)
  {
          struct globaldata *gd = mycpu;
          sysclock_t delta;
  
          do {
                  tsp->tv_sec = gd->gd_time_seconds;
                  delta = gd->gd_hardclock.time - gd->gd_cpuclock_base;
          } while (tsp->tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  tsp->tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          tsp->tv_nsec = (sys_cputimer->freq64_nsec * delta) >> 32;
  }
  
  void
  microuptime(struct timeval *tvp)
  {
          struct globaldata *gd = mycpu;
          sysclock_t delta;
  
          do {
                  tvp->tv_sec = gd->gd_time_seconds;
                  delta = sys_cputimer->count() - gd->gd_cpuclock_base;
          } while (tvp->tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  tvp->tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          tvp->tv_usec = (sys_cputimer->freq64_usec * delta) >> 32;
  }
  
  void
  nanouptime(struct timespec *tsp)
  {
          struct globaldata *gd = mycpu;
          sysclock_t delta;
  
          do {
                  tsp->tv_sec = gd->gd_time_seconds;
                  delta = sys_cputimer->count() - gd->gd_cpuclock_base;
          } while (tsp->tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  tsp->tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          tsp->tv_nsec = (sys_cputimer->freq64_nsec * delta) >> 32;
  }
  
  /*
   * realtime routines
   */
  void
  getmicrotime(struct timeval *tvp)
  {
          struct globaldata *gd = mycpu;
          struct timespec *bt;
          sysclock_t delta;
  
          do {
                  tvp->tv_sec = gd->gd_time_seconds;
                  delta = gd->gd_hardclock.time - gd->gd_cpuclock_base;
          } while (tvp->tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  tvp->tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          tvp->tv_usec = (sys_cputimer->freq64_usec * delta) >> 32;
  
          bt = &basetime[basetime_index];
          tvp->tv_sec += bt->tv_sec;
          tvp->tv_usec += bt->tv_nsec / 1000;
          while (tvp->tv_usec >= 1000000) {
                  tvp->tv_usec -= 1000000;
                  ++tvp->tv_sec;
          }
  }
  
  void
  getnanotime(struct timespec *tsp)
  {
          struct globaldata *gd = mycpu;
          struct timespec *bt;
          sysclock_t delta;
  
          do {
                  tsp->tv_sec = gd->gd_time_seconds;
                  delta = gd->gd_hardclock.time - gd->gd_cpuclock_base;
          } while (tsp->tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  tsp->tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          tsp->tv_nsec = (sys_cputimer->freq64_nsec * delta) >> 32;
  
          bt = &basetime[basetime_index];
          tsp->tv_sec += bt->tv_sec;
          tsp->tv_nsec += bt->tv_nsec;
          while (tsp->tv_nsec >= 1000000000) {
                  tsp->tv_nsec -= 1000000000;
                  ++tsp->tv_sec;
          }
  }
  
  static void
  getnanotime_nbt(struct timespec *nbt, struct timespec *tsp)
  {
          struct globaldata *gd = mycpu;
          sysclock_t delta;
  
          do {
                  tsp->tv_sec = gd->gd_time_seconds;
                  delta = gd->gd_hardclock.time - gd->gd_cpuclock_base;
          } while (tsp->tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  tsp->tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          tsp->tv_nsec = (sys_cputimer->freq64_nsec * delta) >> 32;
  
          tsp->tv_sec += nbt->tv_sec;
          tsp->tv_nsec += nbt->tv_nsec;
          while (tsp->tv_nsec >= 1000000000) {
                  tsp->tv_nsec -= 1000000000;
                  ++tsp->tv_sec;
          }
  }
  
  
  void
  microtime(struct timeval *tvp)
  {
          struct globaldata *gd = mycpu;
          struct timespec *bt;
          sysclock_t delta;
  
          do {
                  tvp->tv_sec = gd->gd_time_seconds;
                  delta = sys_cputimer->count() - gd->gd_cpuclock_base;
          } while (tvp->tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  tvp->tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          tvp->tv_usec = (sys_cputimer->freq64_usec * delta) >> 32;
  
          bt = &basetime[basetime_index];
          tvp->tv_sec += bt->tv_sec;
          tvp->tv_usec += bt->tv_nsec / 1000;
          while (tvp->tv_usec >= 1000000) {
                  tvp->tv_usec -= 1000000;
                  ++tvp->tv_sec;
          }
  }
  
  void
  nanotime(struct timespec *tsp)
  {
          struct globaldata *gd = mycpu;
          struct timespec *bt;
          sysclock_t delta;
  
          do {
                  tsp->tv_sec = gd->gd_time_seconds;
                  delta = sys_cputimer->count() - gd->gd_cpuclock_base;
          } while (tsp->tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  tsp->tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          tsp->tv_nsec = (sys_cputimer->freq64_nsec * delta) >> 32;
  
          bt = &basetime[basetime_index];
          tsp->tv_sec += bt->tv_sec;
          tsp->tv_nsec += bt->tv_nsec;
          while (tsp->tv_nsec >= 1000000000) {
                  tsp->tv_nsec -= 1000000000;
                  ++tsp->tv_sec;
          }
  }
  
  /*
   * note: this is not exactly synchronized with real time.  To do that we
   * would have to do what microtime does and check for a nanoseconds overflow.
   */
  time_t
  get_approximate_time_t(void)
  {
          struct globaldata *gd = mycpu;
          struct timespec *bt;
  
          bt = &basetime[basetime_index];
          return(gd->gd_time_seconds + bt->tv_sec);
  }
  
  int
  pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
  {
          pps_params_t *app;
          struct pps_fetch_args *fapi;
  #ifdef PPS_SYNC
          struct pps_kcbind_args *kapi;
  #endif
  
          switch (cmd) {
          case PPS_IOC_CREATE:
                  return (0);
          case PPS_IOC_DESTROY:
                  return (0);
          case PPS_IOC_SETPARAMS:
                  app = (pps_params_t *)data;
                  if (app->mode & ~pps->ppscap)
                          return (EINVAL);
                  pps->ppsparam = *app;         
                  return (0);
          case PPS_IOC_GETPARAMS:
                  app = (pps_params_t *)data;
                  *app = pps->ppsparam;
                  app->api_version = PPS_API_VERS_1;
                  return (0);
          case PPS_IOC_GETCAP:
                  *(int*)data = pps->ppscap;
                  return (0);
          case PPS_IOC_FETCH:
                  fapi = (struct pps_fetch_args *)data;
                  if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
                          return (EINVAL);
                  if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec)
                          return (EOPNOTSUPP);
                  pps->ppsinfo.current_mode = pps->ppsparam.mode;         
                  fapi->pps_info_buf = pps->ppsinfo;
                  return (0);
          case PPS_IOC_KCBIND:
  #ifdef PPS_SYNC
                  kapi = (struct pps_kcbind_args *)data;
                  /* XXX Only root should be able to do this */
                  if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
                          return (EINVAL);
                  if (kapi->kernel_consumer != PPS_KC_HARDPPS)
                          return (EINVAL);
                  if (kapi->edge & ~pps->ppscap)
                          return (EINVAL);
                  pps->kcmode = kapi->edge;
                  return (0);
  #else
                  return (EOPNOTSUPP);
  #endif
          default:
                  return (ENOTTY);
          }
  }
  
  void
  pps_init(struct pps_state *pps)
  {
          pps->ppscap |= PPS_TSFMT_TSPEC;
          if (pps->ppscap & PPS_CAPTUREASSERT)
                  pps->ppscap |= PPS_OFFSETASSERT;
          if (pps->ppscap & PPS_CAPTURECLEAR)
                  pps->ppscap |= PPS_OFFSETCLEAR;
  }
  
  void
  pps_event(struct pps_state *pps, sysclock_t count, int event)
  {
          struct globaldata *gd;
          struct timespec *tsp;
          struct timespec *osp;
          struct timespec *bt;
          struct timespec ts;
          sysclock_t *pcount;
  #ifdef PPS_SYNC
          sysclock_t tcount;
  #endif
          sysclock_t delta;
          pps_seq_t *pseq;
          int foff;
          int fhard;
  
          gd = mycpu;
  
          /* Things would be easier with arrays... */
          if (event == PPS_CAPTUREASSERT) {
                  tsp = &pps->ppsinfo.assert_timestamp;
                  osp = &pps->ppsparam.assert_offset;
                  foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
                  fhard = pps->kcmode & PPS_CAPTUREASSERT;
                  pcount = &pps->ppscount[0];
                  pseq = &pps->ppsinfo.assert_sequence;
          } else {
                  tsp = &pps->ppsinfo.clear_timestamp;
                  osp = &pps->ppsparam.clear_offset;
                  foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
                  fhard = pps->kcmode & PPS_CAPTURECLEAR;
                  pcount = &pps->ppscount[1];
                  pseq = &pps->ppsinfo.clear_sequence;
          }
  
          /* Nothing really happened */
          if (*pcount == count)
                  return;
  
          *pcount = count;
  
          do {
                  ts.tv_sec = gd->gd_time_seconds;
                  delta = count - gd->gd_cpuclock_base;
          } while (ts.tv_sec != gd->gd_time_seconds);
  
          if (delta >= sys_cputimer->freq) {
                  ts.tv_sec += delta / sys_cputimer->freq;
                  delta %= sys_cputimer->freq;
          }
          ts.tv_nsec = (sys_cputimer->freq64_nsec * delta) >> 32;
          bt = &basetime[basetime_index];
          ts.tv_sec += bt->tv_sec;
          ts.tv_nsec += bt->tv_nsec;
          while (ts.tv_nsec >= 1000000000) {
                  ts.tv_nsec -= 1000000000;
                  ++ts.tv_sec;
          }
  
          (*pseq)++;
          *tsp = ts;
  
          if (foff) {
                  timespecadd(tsp, osp);
                  if (tsp->tv_nsec < 0) {
                          tsp->tv_nsec += 1000000000;
                          tsp->tv_sec -= 1;
                  }
          }
  #ifdef PPS_SYNC
          if (fhard) {
                  /* magic, at its best... */
                  tcount = count - pps->ppscount[2];
                  pps->ppscount[2] = count;
                  if (tcount >= sys_cputimer->freq) {
                          delta = (1000000000 * (tcount / sys_cputimer->freq) +
                                   sys_cputimer->freq64_nsec * 
                                   (tcount % sys_cputimer->freq)) >> 32;
                  } else {
                          delta = (sys_cputimer->freq64_nsec * tcount) >> 32;
                  }
                  hardpps(tsp, delta);
          }
  #endif
  }
  
  /*
   * Return the tsc target value for a delay of (ns).
   *
   * Returns -1 if the TSC is not supported.
   */
  int64_t
  tsc_get_target(int ns)
  {
  #if defined(_RDTSC_SUPPORTED_)
          if (cpu_feature & CPUID_TSC) {
                  return (rdtsc() + tsc_frequency * ns / (int64_t)1000000000);
          }
  #endif
          return(-1);
  }
  
  /*
   * Compare the tsc against the passed target
   *
   * Returns +1 if the target has been reached
   * Returns  0 if the target has not yet been reached
   * Returns -1 if the TSC is not supported.
   *
   * Typical use:         while (tsc_test_target(target) == 0) { ...poll... }
   */
  int
  tsc_test_target(int64_t target)
  {
  #if defined(_RDTSC_SUPPORTED_)
          if (cpu_feature & CPUID_TSC) {
                  if ((int64_t)(target - rdtsc()) <= 0)
                          return(1);
                  return(0);
          }
  #endif
          return(-1);
  }
  
  /*
   * Delay the specified number of nanoseconds using the tsc.  This function
   * returns immediately if the TSC is not supported.  At least one cpu_pause()
   * will be issued.
   */
  void
  tsc_delay(int ns)
  {
          int64_t clk;
  
          clk = tsc_get_target(ns);
          cpu_pause();
          while (tsc_test_target(clk) == 0)
                  cpu_pause();
  }

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