FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_clock.c
1 /* $NetBSD: kern_clock.c,v 1.90.2.1 2004/09/16 03:23:27 jmc Exp $ */
2
3 /*-
4 * Copyright (c) 2000 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
9 * NASA Ames Research Center.
10 *
11 * Redistribution and use in source and binary forms, with or without
12 * modification, are permitted provided that the following conditions
13 * are met:
14 * 1. Redistributions of source code must retain the above copyright
15 * notice, this list of conditions and the following disclaimer.
16 * 2. Redistributions in binary form must reproduce the above copyright
17 * notice, this list of conditions and the following disclaimer in the
18 * documentation and/or other materials provided with the distribution.
19 * 3. All advertising materials mentioning features or use of this software
20 * must display the following acknowledgement:
21 * This product includes software developed by the NetBSD
22 * Foundation, Inc. and its contributors.
23 * 4. Neither the name of The NetBSD Foundation nor the names of its
24 * contributors may be used to endorse or promote products derived
25 * from this software without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
37 * POSSIBILITY OF SUCH DAMAGE.
38 */
39
40 /*-
41 * Copyright (c) 1982, 1986, 1991, 1993
42 * The Regents of the University of California. All rights reserved.
43 * (c) UNIX System Laboratories, Inc.
44 * All or some portions of this file are derived from material licensed
45 * to the University of California by American Telephone and Telegraph
46 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
47 * the permission of UNIX System Laboratories, Inc.
48 *
49 * Redistribution and use in source and binary forms, with or without
50 * modification, are permitted provided that the following conditions
51 * are met:
52 * 1. Redistributions of source code must retain the above copyright
53 * notice, this list of conditions and the following disclaimer.
54 * 2. Redistributions in binary form must reproduce the above copyright
55 * notice, this list of conditions and the following disclaimer in the
56 * documentation and/or other materials provided with the distribution.
57 * 3. Neither the name of the University nor the names of its contributors
58 * may be used to endorse or promote products derived from this software
59 * without specific prior written permission.
60 *
61 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
62 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
63 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
64 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
65 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
66 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
67 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
68 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
69 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
70 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
71 * SUCH DAMAGE.
72 *
73 * @(#)kern_clock.c 8.5 (Berkeley) 1/21/94
74 */
75
76 #include <sys/cdefs.h>
77 __KERNEL_RCSID(0, "$NetBSD: kern_clock.c,v 1.90.2.1 2004/09/16 03:23:27 jmc Exp $");
78
79 #include "opt_ntp.h"
80 #include "opt_multiprocessor.h"
81 #include "opt_perfctrs.h"
82
83 #include <sys/param.h>
84 #include <sys/systm.h>
85 #include <sys/callout.h>
86 #include <sys/kernel.h>
87 #include <sys/proc.h>
88 #include <sys/resourcevar.h>
89 #include <sys/signalvar.h>
90 #include <sys/sysctl.h>
91 #include <sys/timex.h>
92 #include <sys/sched.h>
93 #include <sys/time.h>
94
95 #include <machine/cpu.h>
96 #ifdef __HAVE_GENERIC_SOFT_INTERRUPTS
97 #include <machine/intr.h>
98 #endif
99
100 #ifdef GPROF
101 #include <sys/gmon.h>
102 #endif
103
104 /*
105 * Clock handling routines.
106 *
107 * This code is written to operate with two timers that run independently of
108 * each other. The main clock, running hz times per second, is used to keep
109 * track of real time. The second timer handles kernel and user profiling,
110 * and does resource use estimation. If the second timer is programmable,
111 * it is randomized to avoid aliasing between the two clocks. For example,
112 * the randomization prevents an adversary from always giving up the CPU
113 * just before its quantum expires. Otherwise, it would never accumulate
114 * CPU ticks. The mean frequency of the second timer is stathz.
115 *
116 * If no second timer exists, stathz will be zero; in this case we drive
117 * profiling and statistics off the main clock. This WILL NOT be accurate;
118 * do not do it unless absolutely necessary.
119 *
120 * The statistics clock may (or may not) be run at a higher rate while
121 * profiling. This profile clock runs at profhz. We require that profhz
122 * be an integral multiple of stathz.
123 *
124 * If the statistics clock is running fast, it must be divided by the ratio
125 * profhz/stathz for statistics. (For profiling, every tick counts.)
126 */
127
128 #ifdef NTP /* NTP phase-locked loop in kernel */
129 /*
130 * Phase/frequency-lock loop (PLL/FLL) definitions
131 *
132 * The following variables are read and set by the ntp_adjtime() system
133 * call.
134 *
135 * time_state shows the state of the system clock, with values defined
136 * in the timex.h header file.
137 *
138 * time_status shows the status of the system clock, with bits defined
139 * in the timex.h header file.
140 *
141 * time_offset is used by the PLL/FLL to adjust the system time in small
142 * increments.
143 *
144 * time_constant determines the bandwidth or "stiffness" of the PLL.
145 *
146 * time_tolerance determines maximum frequency error or tolerance of the
147 * CPU clock oscillator and is a property of the architecture; however,
148 * in principle it could change as result of the presence of external
149 * discipline signals, for instance.
150 *
151 * time_precision is usually equal to the kernel tick variable; however,
152 * in cases where a precision clock counter or external clock is
153 * available, the resolution can be much less than this and depend on
154 * whether the external clock is working or not.
155 *
156 * time_maxerror is initialized by a ntp_adjtime() call and increased by
157 * the kernel once each second to reflect the maximum error bound
158 * growth.
159 *
160 * time_esterror is set and read by the ntp_adjtime() call, but
161 * otherwise not used by the kernel.
162 */
163 int time_state = TIME_OK; /* clock state */
164 int time_status = STA_UNSYNC; /* clock status bits */
165 long time_offset = 0; /* time offset (us) */
166 long time_constant = 0; /* pll time constant */
167 long time_tolerance = MAXFREQ; /* frequency tolerance (scaled ppm) */
168 long time_precision = 1; /* clock precision (us) */
169 long time_maxerror = MAXPHASE; /* maximum error (us) */
170 long time_esterror = MAXPHASE; /* estimated error (us) */
171
172 /*
173 * The following variables establish the state of the PLL/FLL and the
174 * residual time and frequency offset of the local clock. The scale
175 * factors are defined in the timex.h header file.
176 *
177 * time_phase and time_freq are the phase increment and the frequency
178 * increment, respectively, of the kernel time variable.
179 *
180 * time_freq is set via ntp_adjtime() from a value stored in a file when
181 * the synchronization daemon is first started. Its value is retrieved
182 * via ntp_adjtime() and written to the file about once per hour by the
183 * daemon.
184 *
185 * time_adj is the adjustment added to the value of tick at each timer
186 * interrupt and is recomputed from time_phase and time_freq at each
187 * seconds rollover.
188 *
189 * time_reftime is the second's portion of the system time at the last
190 * call to ntp_adjtime(). It is used to adjust the time_freq variable
191 * and to increase the time_maxerror as the time since last update
192 * increases.
193 */
194 long time_phase = 0; /* phase offset (scaled us) */
195 long time_freq = 0; /* frequency offset (scaled ppm) */
196 long time_adj = 0; /* tick adjust (scaled 1 / hz) */
197 long time_reftime = 0; /* time at last adjustment (s) */
198
199 #ifdef PPS_SYNC
200 /*
201 * The following variables are used only if the kernel PPS discipline
202 * code is configured (PPS_SYNC). The scale factors are defined in the
203 * timex.h header file.
204 *
205 * pps_time contains the time at each calibration interval, as read by
206 * microtime(). pps_count counts the seconds of the calibration
207 * interval, the duration of which is nominally pps_shift in powers of
208 * two.
209 *
210 * pps_offset is the time offset produced by the time median filter
211 * pps_tf[], while pps_jitter is the dispersion (jitter) measured by
212 * this filter.
213 *
214 * pps_freq is the frequency offset produced by the frequency median
215 * filter pps_ff[], while pps_stabil is the dispersion (wander) measured
216 * by this filter.
217 *
218 * pps_usec is latched from a high resolution counter or external clock
219 * at pps_time. Here we want the hardware counter contents only, not the
220 * contents plus the time_tv.usec as usual.
221 *
222 * pps_valid counts the number of seconds since the last PPS update. It
223 * is used as a watchdog timer to disable the PPS discipline should the
224 * PPS signal be lost.
225 *
226 * pps_glitch counts the number of seconds since the beginning of an
227 * offset burst more than tick/2 from current nominal offset. It is used
228 * mainly to suppress error bursts due to priority conflicts between the
229 * PPS interrupt and timer interrupt.
230 *
231 * pps_intcnt counts the calibration intervals for use in the interval-
232 * adaptation algorithm. It's just too complicated for words.
233 *
234 * pps_kc_hardpps_source contains an arbitrary value that uniquely
235 * identifies the currently bound source of the PPS signal, or NULL
236 * if no source is bound.
237 *
238 * pps_kc_hardpps_mode indicates which transitions, if any, of the PPS
239 * signal should be reported.
240 */
241 struct timeval pps_time; /* kernel time at last interval */
242 long pps_tf[] = {0, 0, 0}; /* pps time offset median filter (us) */
243 long pps_offset = 0; /* pps time offset (us) */
244 long pps_jitter = MAXTIME; /* time dispersion (jitter) (us) */
245 long pps_ff[] = {0, 0, 0}; /* pps frequency offset median filter */
246 long pps_freq = 0; /* frequency offset (scaled ppm) */
247 long pps_stabil = MAXFREQ; /* frequency dispersion (scaled ppm) */
248 long pps_usec = 0; /* microsec counter at last interval */
249 long pps_valid = PPS_VALID; /* pps signal watchdog counter */
250 int pps_glitch = 0; /* pps signal glitch counter */
251 int pps_count = 0; /* calibration interval counter (s) */
252 int pps_shift = PPS_SHIFT; /* interval duration (s) (shift) */
253 int pps_intcnt = 0; /* intervals at current duration */
254 void *pps_kc_hardpps_source = NULL; /* current PPS supplier's identifier */
255 int pps_kc_hardpps_mode = 0; /* interesting edges of PPS signal */
256
257 /*
258 * PPS signal quality monitors
259 *
260 * pps_jitcnt counts the seconds that have been discarded because the
261 * jitter measured by the time median filter exceeds the limit MAXTIME
262 * (100 us).
263 *
264 * pps_calcnt counts the frequency calibration intervals, which are
265 * variable from 4 s to 256 s.
266 *
267 * pps_errcnt counts the calibration intervals which have been discarded
268 * because the wander exceeds the limit MAXFREQ (100 ppm) or where the
269 * calibration interval jitter exceeds two ticks.
270 *
271 * pps_stbcnt counts the calibration intervals that have been discarded
272 * because the frequency wander exceeds the limit MAXFREQ / 4 (25 us).
273 */
274 long pps_jitcnt = 0; /* jitter limit exceeded */
275 long pps_calcnt = 0; /* calibration intervals */
276 long pps_errcnt = 0; /* calibration errors */
277 long pps_stbcnt = 0; /* stability limit exceeded */
278 #endif /* PPS_SYNC */
279
280 #ifdef EXT_CLOCK
281 /*
282 * External clock definitions
283 *
284 * The following definitions and declarations are used only if an
285 * external clock is configured on the system.
286 */
287 #define CLOCK_INTERVAL 30 /* CPU clock update interval (s) */
288
289 /*
290 * The clock_count variable is set to CLOCK_INTERVAL at each PPS
291 * interrupt and decremented once each second.
292 */
293 int clock_count = 0; /* CPU clock counter */
294
295 #ifdef HIGHBALL
296 /*
297 * The clock_offset and clock_cpu variables are used by the HIGHBALL
298 * interface. The clock_offset variable defines the offset between
299 * system time and the HIGBALL counters. The clock_cpu variable contains
300 * the offset between the system clock and the HIGHBALL clock for use in
301 * disciplining the kernel time variable.
302 */
303 extern struct timeval clock_offset; /* Highball clock offset */
304 long clock_cpu = 0; /* CPU clock adjust */
305 #endif /* HIGHBALL */
306 #endif /* EXT_CLOCK */
307 #endif /* NTP */
308
309
310 /*
311 * Bump a timeval by a small number of usec's.
312 */
313 #define BUMPTIME(t, usec) { \
314 volatile struct timeval *tp = (t); \
315 long us; \
316 \
317 tp->tv_usec = us = tp->tv_usec + (usec); \
318 if (us >= 1000000) { \
319 tp->tv_usec = us - 1000000; \
320 tp->tv_sec++; \
321 } \
322 }
323
324 int stathz;
325 int profhz;
326 int profsrc;
327 int schedhz;
328 int profprocs;
329 int hardclock_ticks;
330 static int psdiv; /* prof => stat divider */
331 int psratio; /* ratio: prof / stat */
332 int tickfix, tickfixinterval; /* used if tick not really integral */
333 #ifndef NTP
334 static int tickfixcnt; /* accumulated fractional error */
335 #else
336 int fixtick; /* used by NTP for same */
337 int shifthz;
338 #endif
339
340 /*
341 * We might want ldd to load the both words from time at once.
342 * To succeed we need to be quadword aligned.
343 * The sparc already does that, and that it has worked so far is a fluke.
344 */
345 volatile struct timeval time __attribute__((__aligned__(__alignof__(quad_t))));
346 volatile struct timeval mono_time;
347
348 void *softclock_si;
349
350 /*
351 * Initialize clock frequencies and start both clocks running.
352 */
353 void
354 initclocks(void)
355 {
356 int i;
357
358 #ifdef __HAVE_GENERIC_SOFT_INTERRUPTS
359 softclock_si = softintr_establish(IPL_SOFTCLOCK, softclock, NULL);
360 if (softclock_si == NULL)
361 panic("initclocks: unable to register softclock intr");
362 #endif
363
364 /*
365 * Set divisors to 1 (normal case) and let the machine-specific
366 * code do its bit.
367 */
368 psdiv = 1;
369 cpu_initclocks();
370
371 /*
372 * Compute profhz/stathz/rrticks, and fix profhz if needed.
373 */
374 i = stathz ? stathz : hz;
375 if (profhz == 0)
376 profhz = i;
377 psratio = profhz / i;
378 rrticks = hz / 10;
379
380 #ifdef NTP
381 switch (hz) {
382 case 1:
383 shifthz = SHIFT_SCALE - 0;
384 break;
385 case 2:
386 shifthz = SHIFT_SCALE - 1;
387 break;
388 case 4:
389 shifthz = SHIFT_SCALE - 2;
390 break;
391 case 8:
392 shifthz = SHIFT_SCALE - 3;
393 break;
394 case 16:
395 shifthz = SHIFT_SCALE - 4;
396 break;
397 case 32:
398 shifthz = SHIFT_SCALE - 5;
399 break;
400 case 50:
401 case 60:
402 case 64:
403 shifthz = SHIFT_SCALE - 6;
404 break;
405 case 96:
406 case 100:
407 case 128:
408 shifthz = SHIFT_SCALE - 7;
409 break;
410 case 256:
411 shifthz = SHIFT_SCALE - 8;
412 break;
413 case 512:
414 shifthz = SHIFT_SCALE - 9;
415 break;
416 case 1000:
417 case 1024:
418 shifthz = SHIFT_SCALE - 10;
419 break;
420 case 1200:
421 case 2048:
422 shifthz = SHIFT_SCALE - 11;
423 break;
424 case 4096:
425 shifthz = SHIFT_SCALE - 12;
426 break;
427 case 8192:
428 shifthz = SHIFT_SCALE - 13;
429 break;
430 case 16384:
431 shifthz = SHIFT_SCALE - 14;
432 break;
433 case 32768:
434 shifthz = SHIFT_SCALE - 15;
435 break;
436 case 65536:
437 shifthz = SHIFT_SCALE - 16;
438 break;
439 default:
440 panic("weird hz");
441 }
442 if (fixtick == 0) {
443 /*
444 * Give MD code a chance to set this to a better
445 * value; but, if it doesn't, we should.
446 */
447 fixtick = (1000000 - (hz*tick));
448 }
449 #endif
450 }
451
452 /*
453 * The real-time timer, interrupting hz times per second.
454 */
455 void
456 hardclock(struct clockframe *frame)
457 {
458 struct lwp *l;
459 struct proc *p;
460 int delta;
461 extern int tickdelta;
462 extern long timedelta;
463 struct cpu_info *ci = curcpu();
464 struct ptimer *pt;
465 #ifdef NTP
466 int time_update;
467 int ltemp;
468 #endif
469
470 l = curlwp;
471 if (l) {
472 p = l->l_proc;
473 /*
474 * Run current process's virtual and profile time, as needed.
475 */
476 if (CLKF_USERMODE(frame) && p->p_timers &&
477 (pt = LIST_FIRST(&p->p_timers->pts_virtual)) != NULL)
478 if (itimerdecr(pt, tick) == 0)
479 itimerfire(pt);
480 if (p->p_timers &&
481 (pt = LIST_FIRST(&p->p_timers->pts_prof)) != NULL)
482 if (itimerdecr(pt, tick) == 0)
483 itimerfire(pt);
484 }
485
486 /*
487 * If no separate statistics clock is available, run it from here.
488 */
489 if (stathz == 0)
490 statclock(frame);
491 if ((--ci->ci_schedstate.spc_rrticks) <= 0)
492 roundrobin(ci);
493
494 #if defined(MULTIPROCESSOR)
495 /*
496 * If we are not the primary CPU, we're not allowed to do
497 * any more work.
498 */
499 if (CPU_IS_PRIMARY(ci) == 0)
500 return;
501 #endif
502
503 /*
504 * Increment the time-of-day. The increment is normally just
505 * ``tick''. If the machine is one which has a clock frequency
506 * such that ``hz'' would not divide the second evenly into
507 * milliseconds, a periodic adjustment must be applied. Finally,
508 * if we are still adjusting the time (see adjtime()),
509 * ``tickdelta'' may also be added in.
510 */
511 hardclock_ticks++;
512 delta = tick;
513
514 #ifndef NTP
515 if (tickfix) {
516 tickfixcnt += tickfix;
517 if (tickfixcnt >= tickfixinterval) {
518 delta++;
519 tickfixcnt -= tickfixinterval;
520 }
521 }
522 #endif /* !NTP */
523 /* Imprecise 4bsd adjtime() handling */
524 if (timedelta != 0) {
525 delta += tickdelta;
526 timedelta -= tickdelta;
527 }
528
529 #ifdef notyet
530 microset();
531 #endif
532
533 #ifndef NTP
534 BUMPTIME(&time, delta); /* XXX Now done using NTP code below */
535 #endif
536 BUMPTIME(&mono_time, delta);
537
538 #ifdef NTP
539 time_update = delta;
540
541 /*
542 * Compute the phase adjustment. If the low-order bits
543 * (time_phase) of the update overflow, bump the high-order bits
544 * (time_update).
545 */
546 time_phase += time_adj;
547 if (time_phase <= -FINEUSEC) {
548 ltemp = -time_phase >> SHIFT_SCALE;
549 time_phase += ltemp << SHIFT_SCALE;
550 time_update -= ltemp;
551 } else if (time_phase >= FINEUSEC) {
552 ltemp = time_phase >> SHIFT_SCALE;
553 time_phase -= ltemp << SHIFT_SCALE;
554 time_update += ltemp;
555 }
556
557 #ifdef HIGHBALL
558 /*
559 * If the HIGHBALL board is installed, we need to adjust the
560 * external clock offset in order to close the hardware feedback
561 * loop. This will adjust the external clock phase and frequency
562 * in small amounts. The additional phase noise and frequency
563 * wander this causes should be minimal. We also need to
564 * discipline the kernel time variable, since the PLL is used to
565 * discipline the external clock. If the Highball board is not
566 * present, we discipline kernel time with the PLL as usual. We
567 * assume that the external clock phase adjustment (time_update)
568 * and kernel phase adjustment (clock_cpu) are less than the
569 * value of tick.
570 */
571 clock_offset.tv_usec += time_update;
572 if (clock_offset.tv_usec >= 1000000) {
573 clock_offset.tv_sec++;
574 clock_offset.tv_usec -= 1000000;
575 }
576 if (clock_offset.tv_usec < 0) {
577 clock_offset.tv_sec--;
578 clock_offset.tv_usec += 1000000;
579 }
580 time.tv_usec += clock_cpu;
581 clock_cpu = 0;
582 #else
583 time.tv_usec += time_update;
584 #endif /* HIGHBALL */
585
586 /*
587 * On rollover of the second the phase adjustment to be used for
588 * the next second is calculated. Also, the maximum error is
589 * increased by the tolerance. If the PPS frequency discipline
590 * code is present, the phase is increased to compensate for the
591 * CPU clock oscillator frequency error.
592 *
593 * On a 32-bit machine and given parameters in the timex.h
594 * header file, the maximum phase adjustment is +-512 ms and
595 * maximum frequency offset is a tad less than) +-512 ppm. On a
596 * 64-bit machine, you shouldn't need to ask.
597 */
598 if (time.tv_usec >= 1000000) {
599 time.tv_usec -= 1000000;
600 time.tv_sec++;
601 time_maxerror += time_tolerance >> SHIFT_USEC;
602
603 /*
604 * Leap second processing. If in leap-insert state at
605 * the end of the day, the system clock is set back one
606 * second; if in leap-delete state, the system clock is
607 * set ahead one second. The microtime() routine or
608 * external clock driver will insure that reported time
609 * is always monotonic. The ugly divides should be
610 * replaced.
611 */
612 switch (time_state) {
613 case TIME_OK:
614 if (time_status & STA_INS)
615 time_state = TIME_INS;
616 else if (time_status & STA_DEL)
617 time_state = TIME_DEL;
618 break;
619
620 case TIME_INS:
621 if (time.tv_sec % 86400 == 0) {
622 time.tv_sec--;
623 time_state = TIME_OOP;
624 }
625 break;
626
627 case TIME_DEL:
628 if ((time.tv_sec + 1) % 86400 == 0) {
629 time.tv_sec++;
630 time_state = TIME_WAIT;
631 }
632 break;
633
634 case TIME_OOP:
635 time_state = TIME_WAIT;
636 break;
637
638 case TIME_WAIT:
639 if (!(time_status & (STA_INS | STA_DEL)))
640 time_state = TIME_OK;
641 break;
642 }
643
644 /*
645 * Compute the phase adjustment for the next second. In
646 * PLL mode, the offset is reduced by a fixed factor
647 * times the time constant. In FLL mode the offset is
648 * used directly. In either mode, the maximum phase
649 * adjustment for each second is clamped so as to spread
650 * the adjustment over not more than the number of
651 * seconds between updates.
652 */
653 if (time_offset < 0) {
654 ltemp = -time_offset;
655 if (!(time_status & STA_FLL))
656 ltemp >>= SHIFT_KG + time_constant;
657 if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE)
658 ltemp = (MAXPHASE / MINSEC) <<
659 SHIFT_UPDATE;
660 time_offset += ltemp;
661 time_adj = -ltemp << (shifthz - SHIFT_UPDATE);
662 } else if (time_offset > 0) {
663 ltemp = time_offset;
664 if (!(time_status & STA_FLL))
665 ltemp >>= SHIFT_KG + time_constant;
666 if (ltemp > (MAXPHASE / MINSEC) << SHIFT_UPDATE)
667 ltemp = (MAXPHASE / MINSEC) <<
668 SHIFT_UPDATE;
669 time_offset -= ltemp;
670 time_adj = ltemp << (shifthz - SHIFT_UPDATE);
671 } else
672 time_adj = 0;
673
674 /*
675 * Compute the frequency estimate and additional phase
676 * adjustment due to frequency error for the next
677 * second. When the PPS signal is engaged, gnaw on the
678 * watchdog counter and update the frequency computed by
679 * the pll and the PPS signal.
680 */
681 #ifdef PPS_SYNC
682 pps_valid++;
683 if (pps_valid == PPS_VALID) {
684 pps_jitter = MAXTIME;
685 pps_stabil = MAXFREQ;
686 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
687 STA_PPSWANDER | STA_PPSERROR);
688 }
689 ltemp = time_freq + pps_freq;
690 #else
691 ltemp = time_freq;
692 #endif /* PPS_SYNC */
693
694 if (ltemp < 0)
695 time_adj -= -ltemp >> (SHIFT_USEC - shifthz);
696 else
697 time_adj += ltemp >> (SHIFT_USEC - shifthz);
698 time_adj += (long)fixtick << shifthz;
699
700 /*
701 * When the CPU clock oscillator frequency is not a
702 * power of 2 in Hz, shifthz is only an approximate
703 * scale factor.
704 *
705 * To determine the adjustment, you can do the following:
706 * bc -q
707 * scale=24
708 * obase=2
709 * idealhz/realhz
710 * where `idealhz' is the next higher power of 2, and `realhz'
711 * is the actual value. You may need to factor this result
712 * into a sequence of 2 multipliers to get better precision.
713 *
714 * Likewise, the error can be calculated with (e.g. for 100Hz):
715 * bc -q
716 * scale=24
717 * ((1+2^-2+2^-5)*(1-2^-10)*realhz-idealhz)/idealhz
718 * (and then multiply by 1000000 to get ppm).
719 */
720 switch (hz) {
721 case 60:
722 /* A factor of 1.000100010001 gives about 15ppm
723 error. */
724 if (time_adj < 0) {
725 time_adj -= (-time_adj >> 4);
726 time_adj -= (-time_adj >> 8);
727 } else {
728 time_adj += (time_adj >> 4);
729 time_adj += (time_adj >> 8);
730 }
731 break;
732
733 case 96:
734 /* A factor of 1.0101010101 gives about 244ppm error. */
735 if (time_adj < 0) {
736 time_adj -= (-time_adj >> 2);
737 time_adj -= (-time_adj >> 4) + (-time_adj >> 8);
738 } else {
739 time_adj += (time_adj >> 2);
740 time_adj += (time_adj >> 4) + (time_adj >> 8);
741 }
742 break;
743
744 case 50:
745 case 100:
746 /* A factor of 1.010001111010111 gives about 1ppm
747 error. */
748 if (time_adj < 0) {
749 time_adj -= (-time_adj >> 2) + (-time_adj >> 5);
750 time_adj += (-time_adj >> 10);
751 } else {
752 time_adj += (time_adj >> 2) + (time_adj >> 5);
753 time_adj -= (time_adj >> 10);
754 }
755 break;
756
757 case 1000:
758 /* A factor of 1.000001100010100001 gives about 50ppm
759 error. */
760 if (time_adj < 0) {
761 time_adj -= (-time_adj >> 6) + (-time_adj >> 11);
762 time_adj -= (-time_adj >> 7);
763 } else {
764 time_adj += (time_adj >> 6) + (time_adj >> 11);
765 time_adj += (time_adj >> 7);
766 }
767 break;
768
769 case 1200:
770 /* A factor of 1.1011010011100001 gives about 64ppm
771 error. */
772 if (time_adj < 0) {
773 time_adj -= (-time_adj >> 1) + (-time_adj >> 6);
774 time_adj -= (-time_adj >> 3) + (-time_adj >> 10);
775 } else {
776 time_adj += (time_adj >> 1) + (time_adj >> 6);
777 time_adj += (time_adj >> 3) + (time_adj >> 10);
778 }
779 break;
780 }
781
782 #ifdef EXT_CLOCK
783 /*
784 * If an external clock is present, it is necessary to
785 * discipline the kernel time variable anyway, since not
786 * all system components use the microtime() interface.
787 * Here, the time offset between the external clock and
788 * kernel time variable is computed every so often.
789 */
790 clock_count++;
791 if (clock_count > CLOCK_INTERVAL) {
792 clock_count = 0;
793 microtime(&clock_ext);
794 delta.tv_sec = clock_ext.tv_sec - time.tv_sec;
795 delta.tv_usec = clock_ext.tv_usec -
796 time.tv_usec;
797 if (delta.tv_usec < 0)
798 delta.tv_sec--;
799 if (delta.tv_usec >= 500000) {
800 delta.tv_usec -= 1000000;
801 delta.tv_sec++;
802 }
803 if (delta.tv_usec < -500000) {
804 delta.tv_usec += 1000000;
805 delta.tv_sec--;
806 }
807 if (delta.tv_sec > 0 || (delta.tv_sec == 0 &&
808 delta.tv_usec > MAXPHASE) ||
809 delta.tv_sec < -1 || (delta.tv_sec == -1 &&
810 delta.tv_usec < -MAXPHASE)) {
811 time = clock_ext;
812 delta.tv_sec = 0;
813 delta.tv_usec = 0;
814 }
815 #ifdef HIGHBALL
816 clock_cpu = delta.tv_usec;
817 #else /* HIGHBALL */
818 hardupdate(delta.tv_usec);
819 #endif /* HIGHBALL */
820 }
821 #endif /* EXT_CLOCK */
822 }
823
824 #endif /* NTP */
825
826 /*
827 * Update real-time timeout queue.
828 * Process callouts at a very low CPU priority, so we don't keep the
829 * relatively high clock interrupt priority any longer than necessary.
830 */
831 if (callout_hardclock()) {
832 if (CLKF_BASEPRI(frame)) {
833 /*
834 * Save the overhead of a software interrupt;
835 * it will happen as soon as we return, so do
836 * it now.
837 */
838 spllowersoftclock();
839 KERNEL_LOCK(LK_CANRECURSE|LK_EXCLUSIVE);
840 softclock(NULL);
841 KERNEL_UNLOCK();
842 } else {
843 #ifdef __HAVE_GENERIC_SOFT_INTERRUPTS
844 softintr_schedule(softclock_si);
845 #else
846 setsoftclock();
847 #endif
848 }
849 }
850 }
851
852 /*
853 * Compute number of hz until specified time. Used to compute second
854 * argument to callout_reset() from an absolute time.
855 */
856 int
857 hzto(struct timeval *tv)
858 {
859 unsigned long ticks;
860 long sec, usec;
861 int s;
862
863 /*
864 * If the number of usecs in the whole seconds part of the time
865 * difference fits in a long, then the total number of usecs will
866 * fit in an unsigned long. Compute the total and convert it to
867 * ticks, rounding up and adding 1 to allow for the current tick
868 * to expire. Rounding also depends on unsigned long arithmetic
869 * to avoid overflow.
870 *
871 * Otherwise, if the number of ticks in the whole seconds part of
872 * the time difference fits in a long, then convert the parts to
873 * ticks separately and add, using similar rounding methods and
874 * overflow avoidance. This method would work in the previous
875 * case, but it is slightly slower and assume that hz is integral.
876 *
877 * Otherwise, round the time difference down to the maximum
878 * representable value.
879 *
880 * If ints are 32-bit, then the maximum value for any timeout in
881 * 10ms ticks is 248 days.
882 */
883 s = splclock();
884 sec = tv->tv_sec - time.tv_sec;
885 usec = tv->tv_usec - time.tv_usec;
886 splx(s);
887
888 if (usec < 0) {
889 sec--;
890 usec += 1000000;
891 }
892
893 if (sec < 0 || (sec == 0 && usec <= 0)) {
894 /*
895 * Would expire now or in the past. Return 0 ticks.
896 * This is different from the legacy hzto() interface,
897 * and callers need to check for it.
898 */
899 ticks = 0;
900 } else if (sec <= (LONG_MAX / 1000000))
901 ticks = (((sec * 1000000) + (unsigned long)usec + (tick - 1))
902 / tick) + 1;
903 else if (sec <= (LONG_MAX / hz))
904 ticks = (sec * hz) +
905 (((unsigned long)usec + (tick - 1)) / tick) + 1;
906 else
907 ticks = LONG_MAX;
908
909 if (ticks > INT_MAX)
910 ticks = INT_MAX;
911
912 return ((int)ticks);
913 }
914
915 /*
916 * Start profiling on a process.
917 *
918 * Kernel profiling passes proc0 which never exits and hence
919 * keeps the profile clock running constantly.
920 */
921 void
922 startprofclock(struct proc *p)
923 {
924
925 if ((p->p_flag & P_PROFIL) == 0) {
926 p->p_flag |= P_PROFIL;
927 /*
928 * This is only necessary if using the clock as the
929 * profiling source.
930 */
931 if (++profprocs == 1 && stathz != 0)
932 psdiv = psratio;
933 }
934 }
935
936 /*
937 * Stop profiling on a process.
938 */
939 void
940 stopprofclock(struct proc *p)
941 {
942
943 if (p->p_flag & P_PROFIL) {
944 p->p_flag &= ~P_PROFIL;
945 /*
946 * This is only necessary if using the clock as the
947 * profiling source.
948 */
949 if (--profprocs == 0 && stathz != 0)
950 psdiv = 1;
951 }
952 }
953
954 #if defined(PERFCTRS)
955 /*
956 * Independent profiling "tick" in case we're using a separate
957 * clock or profiling event source. Currently, that's just
958 * performance counters--hence the wrapper.
959 */
960 void
961 proftick(struct clockframe *frame)
962 {
963 #ifdef GPROF
964 struct gmonparam *g;
965 intptr_t i;
966 #endif
967 struct proc *p;
968
969 p = curproc;
970 if (CLKF_USERMODE(frame)) {
971 if (p->p_flag & P_PROFIL)
972 addupc_intr(p, CLKF_PC(frame));
973 } else {
974 #ifdef GPROF
975 g = &_gmonparam;
976 if (g->state == GMON_PROF_ON) {
977 i = CLKF_PC(frame) - g->lowpc;
978 if (i < g->textsize) {
979 i /= HISTFRACTION * sizeof(*g->kcount);
980 g->kcount[i]++;
981 }
982 }
983 #endif
984 #ifdef PROC_PC
985 if (p && p->p_flag & P_PROFIL)
986 addupc_intr(p, PROC_PC(p));
987 #endif
988 }
989 }
990 #endif
991
992 /*
993 * Statistics clock. Grab profile sample, and if divider reaches 0,
994 * do process and kernel statistics.
995 */
996 void
997 statclock(struct clockframe *frame)
998 {
999 #ifdef GPROF
1000 struct gmonparam *g;
1001 intptr_t i;
1002 #endif
1003 struct cpu_info *ci = curcpu();
1004 struct schedstate_percpu *spc = &ci->ci_schedstate;
1005 struct lwp *l;
1006 struct proc *p;
1007
1008 /*
1009 * Notice changes in divisor frequency, and adjust clock
1010 * frequency accordingly.
1011 */
1012 if (spc->spc_psdiv != psdiv) {
1013 spc->spc_psdiv = psdiv;
1014 spc->spc_pscnt = psdiv;
1015 if (psdiv == 1) {
1016 setstatclockrate(stathz);
1017 } else {
1018 setstatclockrate(profhz);
1019 }
1020 }
1021 l = curlwp;
1022 p = (l ? l->l_proc : 0);
1023 if (CLKF_USERMODE(frame)) {
1024 if (p->p_flag & P_PROFIL && profsrc == PROFSRC_CLOCK)
1025 addupc_intr(p, CLKF_PC(frame));
1026 if (--spc->spc_pscnt > 0)
1027 return;
1028 /*
1029 * Came from user mode; CPU was in user state.
1030 * If this process is being profiled record the tick.
1031 */
1032 p->p_uticks++;
1033 if (p->p_nice > NZERO)
1034 spc->spc_cp_time[CP_NICE]++;
1035 else
1036 spc->spc_cp_time[CP_USER]++;
1037 } else {
1038 #ifdef GPROF
1039 /*
1040 * Kernel statistics are just like addupc_intr, only easier.
1041 */
1042 g = &_gmonparam;
1043 if (profsrc == PROFSRC_CLOCK && g->state == GMON_PROF_ON) {
1044 i = CLKF_PC(frame) - g->lowpc;
1045 if (i < g->textsize) {
1046 i /= HISTFRACTION * sizeof(*g->kcount);
1047 g->kcount[i]++;
1048 }
1049 }
1050 #endif
1051 #ifdef LWP_PC
1052 if (p && profsrc == PROFSRC_CLOCK && p->p_flag & P_PROFIL)
1053 addupc_intr(p, LWP_PC(l));
1054 #endif
1055 if (--spc->spc_pscnt > 0)
1056 return;
1057 /*
1058 * Came from kernel mode, so we were:
1059 * - handling an interrupt,
1060 * - doing syscall or trap work on behalf of the current
1061 * user process, or
1062 * - spinning in the idle loop.
1063 * Whichever it is, charge the time as appropriate.
1064 * Note that we charge interrupts to the current process,
1065 * regardless of whether they are ``for'' that process,
1066 * so that we know how much of its real time was spent
1067 * in ``non-process'' (i.e., interrupt) work.
1068 */
1069 if (CLKF_INTR(frame)) {
1070 if (p != NULL)
1071 p->p_iticks++;
1072 spc->spc_cp_time[CP_INTR]++;
1073 } else if (p != NULL) {
1074 p->p_sticks++;
1075 spc->spc_cp_time[CP_SYS]++;
1076 } else
1077 spc->spc_cp_time[CP_IDLE]++;
1078 }
1079 spc->spc_pscnt = psdiv;
1080
1081 if (l != NULL) {
1082 ++p->p_cpticks;
1083 /*
1084 * If no separate schedclock is provided, call it here
1085 * at ~~12-25 Hz, ~~16 Hz is best
1086 */
1087 if (schedhz == 0)
1088 if ((++ci->ci_schedstate.spc_schedticks & 3) == 0)
1089 schedclock(l);
1090 }
1091 }
1092
1093
1094 #ifdef NTP /* NTP phase-locked loop in kernel */
1095
1096 /*
1097 * hardupdate() - local clock update
1098 *
1099 * This routine is called by ntp_adjtime() to update the local clock
1100 * phase and frequency. The implementation is of an adaptive-parameter,
1101 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
1102 * time and frequency offset estimates for each call. If the kernel PPS
1103 * discipline code is configured (PPS_SYNC), the PPS signal itself
1104 * determines the new time offset, instead of the calling argument.
1105 * Presumably, calls to ntp_adjtime() occur only when the caller
1106 * believes the local clock is valid within some bound (+-128 ms with
1107 * NTP). If the caller's time is far different than the PPS time, an
1108 * argument will ensue, and it's not clear who will lose.
1109 *
1110 * For uncompensated quartz crystal oscillatores and nominal update
1111 * intervals less than 1024 s, operation should be in phase-lock mode
1112 * (STA_FLL = 0), where the loop is disciplined to phase. For update
1113 * intervals greater than thiss, operation should be in frequency-lock
1114 * mode (STA_FLL = 1), where the loop is disciplined to frequency.
1115 *
1116 * Note: splclock() is in effect.
1117 */
1118 void
1119 hardupdate(long offset)
1120 {
1121 long ltemp, mtemp;
1122
1123 if (!(time_status & STA_PLL) && !(time_status & STA_PPSTIME))
1124 return;
1125 ltemp = offset;
1126 #ifdef PPS_SYNC
1127 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
1128 ltemp = pps_offset;
1129 #endif /* PPS_SYNC */
1130
1131 /*
1132 * Scale the phase adjustment and clamp to the operating range.
1133 */
1134 if (ltemp > MAXPHASE)
1135 time_offset = MAXPHASE << SHIFT_UPDATE;
1136 else if (ltemp < -MAXPHASE)
1137 time_offset = -(MAXPHASE << SHIFT_UPDATE);
1138 else
1139 time_offset = ltemp << SHIFT_UPDATE;
1140
1141 /*
1142 * Select whether the frequency is to be controlled and in which
1143 * mode (PLL or FLL). Clamp to the operating range. Ugly
1144 * multiply/divide should be replaced someday.
1145 */
1146 if (time_status & STA_FREQHOLD || time_reftime == 0)
1147 time_reftime = time.tv_sec;
1148 mtemp = time.tv_sec - time_reftime;
1149 time_reftime = time.tv_sec;
1150 if (time_status & STA_FLL) {
1151 if (mtemp >= MINSEC) {
1152 ltemp = ((time_offset / mtemp) << (SHIFT_USEC -
1153 SHIFT_UPDATE));
1154 if (ltemp < 0)
1155 time_freq -= -ltemp >> SHIFT_KH;
1156 else
1157 time_freq += ltemp >> SHIFT_KH;
1158 }
1159 } else {
1160 if (mtemp < MAXSEC) {
1161 ltemp *= mtemp;
1162 if (ltemp < 0)
1163 time_freq -= -ltemp >> (time_constant +
1164 time_constant + SHIFT_KF -
1165 SHIFT_USEC);
1166 else
1167 time_freq += ltemp >> (time_constant +
1168 time_constant + SHIFT_KF -
1169 SHIFT_USEC);
1170 }
1171 }
1172 if (time_freq > time_tolerance)
1173 time_freq = time_tolerance;
1174 else if (time_freq < -time_tolerance)
1175 time_freq = -time_tolerance;
1176 }
1177
1178 #ifdef PPS_SYNC
1179 /*
1180 * hardpps() - discipline CPU clock oscillator to external PPS signal
1181 *
1182 * This routine is called at each PPS interrupt in order to discipline
1183 * the CPU clock oscillator to the PPS signal. It measures the PPS phase
1184 * and leaves it in a handy spot for the hardclock() routine. It
1185 * integrates successive PPS phase differences and calculates the
1186 * frequency offset. This is used in hardclock() to discipline the CPU
1187 * clock oscillator so that intrinsic frequency error is cancelled out.
1188 * The code requires the caller to capture the time and hardware counter
1189 * value at the on-time PPS signal transition.
1190 *
1191 * Note that, on some Unix systems, this routine runs at an interrupt
1192 * priority level higher than the timer interrupt routine hardclock().
1193 * Therefore, the variables used are distinct from the hardclock()
1194 * variables, except for certain exceptions: The PPS frequency pps_freq
1195 * and phase pps_offset variables are determined by this routine and
1196 * updated atomically. The time_tolerance variable can be considered a
1197 * constant, since it is infrequently changed, and then only when the
1198 * PPS signal is disabled. The watchdog counter pps_valid is updated
1199 * once per second by hardclock() and is atomically cleared in this
1200 * routine.
1201 */
1202 void
1203 hardpps(struct timeval *tvp, /* time at PPS */
1204 long usec /* hardware counter at PPS */)
1205 {
1206 long u_usec, v_usec, bigtick;
1207 long cal_sec, cal_usec;
1208
1209 /*
1210 * An occasional glitch can be produced when the PPS interrupt
1211 * occurs in the hardclock() routine before the time variable is
1212 * updated. Here the offset is discarded when the difference
1213 * between it and the last one is greater than tick/2, but not
1214 * if the interval since the first discard exceeds 30 s.
1215 */
1216 time_status |= STA_PPSSIGNAL;
1217 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
1218 pps_valid = 0;
1219 u_usec = -tvp->tv_usec;
1220 if (u_usec < -500000)
1221 u_usec += 1000000;
1222 v_usec = pps_offset - u_usec;
1223 if (v_usec < 0)
1224 v_usec = -v_usec;
1225 if (v_usec > (tick >> 1)) {
1226 if (pps_glitch > MAXGLITCH) {
1227 pps_glitch = 0;
1228 pps_tf[2] = u_usec;
1229 pps_tf[1] = u_usec;
1230 } else {
1231 pps_glitch++;
1232 u_usec = pps_offset;
1233 }
1234 } else
1235 pps_glitch = 0;
1236
1237 /*
1238 * A three-stage median filter is used to help deglitch the pps
1239 * time. The median sample becomes the time offset estimate; the
1240 * difference between the other two samples becomes the time
1241 * dispersion (jitter) estimate.
1242 */
1243 pps_tf[2] = pps_tf[1];
1244 pps_tf[1] = pps_tf[0];
1245 pps_tf[0] = u_usec;
1246 if (pps_tf[0] > pps_tf[1]) {
1247 if (pps_tf[1] > pps_tf[2]) {
1248 pps_offset = pps_tf[1]; /* 0 1 2 */
1249 v_usec = pps_tf[0] - pps_tf[2];
1250 } else if (pps_tf[2] > pps_tf[0]) {
1251 pps_offset = pps_tf[0]; /* 2 0 1 */
1252 v_usec = pps_tf[2] - pps_tf[1];
1253 } else {
1254 pps_offset = pps_tf[2]; /* 0 2 1 */
1255 v_usec = pps_tf[0] - pps_tf[1];
1256 }
1257 } else {
1258 if (pps_tf[1] < pps_tf[2]) {
1259 pps_offset = pps_tf[1]; /* 2 1 0 */
1260 v_usec = pps_tf[2] - pps_tf[0];
1261 } else if (pps_tf[2] < pps_tf[0]) {
1262 pps_offset = pps_tf[0]; /* 1 0 2 */
1263 v_usec = pps_tf[1] - pps_tf[2];
1264 } else {
1265 pps_offset = pps_tf[2]; /* 1 2 0 */
1266 v_usec = pps_tf[1] - pps_tf[0];
1267 }
1268 }
1269 if (v_usec > MAXTIME)
1270 pps_jitcnt++;
1271 v_usec = (v_usec << PPS_AVG) - pps_jitter;
1272 if (v_usec < 0)
1273 pps_jitter -= -v_usec >> PPS_AVG;
1274 else
1275 pps_jitter += v_usec >> PPS_AVG;
1276 if (pps_jitter > (MAXTIME >> 1))
1277 time_status |= STA_PPSJITTER;
1278
1279 /*
1280 * During the calibration interval adjust the starting time when
1281 * the tick overflows. At the end of the interval compute the
1282 * duration of the interval and the difference of the hardware
1283 * counters at the beginning and end of the interval. This code
1284 * is deliciously complicated by the fact valid differences may
1285 * exceed the value of tick when using long calibration
1286 * intervals and small ticks. Note that the counter can be
1287 * greater than tick if caught at just the wrong instant, but
1288 * the values returned and used here are correct.
1289 */
1290 bigtick = (long)tick << SHIFT_USEC;
1291 pps_usec -= pps_freq;
1292 if (pps_usec >= bigtick)
1293 pps_usec -= bigtick;
1294 if (pps_usec < 0)
1295 pps_usec += bigtick;
1296 pps_time.tv_sec++;
1297 pps_count++;
1298 if (pps_count < (1 << pps_shift))
1299 return;
1300 pps_count = 0;
1301 pps_calcnt++;
1302 u_usec = usec << SHIFT_USEC;
1303 v_usec = pps_usec - u_usec;
1304 if (v_usec >= bigtick >> 1)
1305 v_usec -= bigtick;
1306 if (v_usec < -(bigtick >> 1))
1307 v_usec += bigtick;
1308 if (v_usec < 0)
1309 v_usec = -(-v_usec >> pps_shift);
1310 else
1311 v_usec = v_usec >> pps_shift;
1312 pps_usec = u_usec;
1313 cal_sec = tvp->tv_sec;
1314 cal_usec = tvp->tv_usec;
1315 cal_sec -= pps_time.tv_sec;
1316 cal_usec -= pps_time.tv_usec;
1317 if (cal_usec < 0) {
1318 cal_usec += 1000000;
1319 cal_sec--;
1320 }
1321 pps_time = *tvp;
1322
1323 /*
1324 * Check for lost interrupts, noise, excessive jitter and
1325 * excessive frequency error. The number of timer ticks during
1326 * the interval may vary +-1 tick. Add to this a margin of one
1327 * tick for the PPS signal jitter and maximum frequency
1328 * deviation. If the limits are exceeded, the calibration
1329 * interval is reset to the minimum and we start over.
1330 */
1331 u_usec = (long)tick << 1;
1332 if (!((cal_sec == -1 && cal_usec > (1000000 - u_usec))
1333 || (cal_sec == 0 && cal_usec < u_usec))
1334 || v_usec > time_tolerance || v_usec < -time_tolerance) {
1335 pps_errcnt++;
1336 pps_shift = PPS_SHIFT;
1337 pps_intcnt = 0;
1338 time_status |= STA_PPSERROR;
1339 return;
1340 }
1341
1342 /*
1343 * A three-stage median filter is used to help deglitch the pps
1344 * frequency. The median sample becomes the frequency offset
1345 * estimate; the difference between the other two samples
1346 * becomes the frequency dispersion (stability) estimate.
1347 */
1348 pps_ff[2] = pps_ff[1];
1349 pps_ff[1] = pps_ff[0];
1350 pps_ff[0] = v_usec;
1351 if (pps_ff[0] > pps_ff[1]) {
1352 if (pps_ff[1] > pps_ff[2]) {
1353 u_usec = pps_ff[1]; /* 0 1 2 */
1354 v_usec = pps_ff[0] - pps_ff[2];
1355 } else if (pps_ff[2] > pps_ff[0]) {
1356 u_usec = pps_ff[0]; /* 2 0 1 */
1357 v_usec = pps_ff[2] - pps_ff[1];
1358 } else {
1359 u_usec = pps_ff[2]; /* 0 2 1 */
1360 v_usec = pps_ff[0] - pps_ff[1];
1361 }
1362 } else {
1363 if (pps_ff[1] < pps_ff[2]) {
1364 u_usec = pps_ff[1]; /* 2 1 0 */
1365 v_usec = pps_ff[2] - pps_ff[0];
1366 } else if (pps_ff[2] < pps_ff[0]) {
1367 u_usec = pps_ff[0]; /* 1 0 2 */
1368 v_usec = pps_ff[1] - pps_ff[2];
1369 } else {
1370 u_usec = pps_ff[2]; /* 1 2 0 */
1371 v_usec = pps_ff[1] - pps_ff[0];
1372 }
1373 }
1374
1375 /*
1376 * Here the frequency dispersion (stability) is updated. If it
1377 * is less than one-fourth the maximum (MAXFREQ), the frequency
1378 * offset is updated as well, but clamped to the tolerance. It
1379 * will be processed later by the hardclock() routine.
1380 */
1381 v_usec = (v_usec >> 1) - pps_stabil;
1382 if (v_usec < 0)
1383 pps_stabil -= -v_usec >> PPS_AVG;
1384 else
1385 pps_stabil += v_usec >> PPS_AVG;
1386 if (pps_stabil > MAXFREQ >> 2) {
1387 pps_stbcnt++;
1388 time_status |= STA_PPSWANDER;
1389 return;
1390 }
1391 if (time_status & STA_PPSFREQ) {
1392 if (u_usec < 0) {
1393 pps_freq -= -u_usec >> PPS_AVG;
1394 if (pps_freq < -time_tolerance)
1395 pps_freq = -time_tolerance;
1396 u_usec = -u_usec;
1397 } else {
1398 pps_freq += u_usec >> PPS_AVG;
1399 if (pps_freq > time_tolerance)
1400 pps_freq = time_tolerance;
1401 }
1402 }
1403
1404 /*
1405 * Here the calibration interval is adjusted. If the maximum
1406 * time difference is greater than tick / 4, reduce the interval
1407 * by half. If this is not the case for four consecutive
1408 * intervals, double the interval.
1409 */
1410 if (u_usec << pps_shift > bigtick >> 2) {
1411 pps_intcnt = 0;
1412 if (pps_shift > PPS_SHIFT)
1413 pps_shift--;
1414 } else if (pps_intcnt >= 4) {
1415 pps_intcnt = 0;
1416 if (pps_shift < PPS_SHIFTMAX)
1417 pps_shift++;
1418 } else
1419 pps_intcnt++;
1420 }
1421 #endif /* PPS_SYNC */
1422 #endif /* NTP */
Cache object: d3dbc04422d101c65dab07d31a8b9bad
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