FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_tc.c
1 /*-
2 * ----------------------------------------------------------------------------
3 * "THE BEER-WARE LICENSE" (Revision 42):
4 * <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
5 * can do whatever you want with this stuff. If we meet some day, and you think
6 * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
7 * ----------------------------------------------------------------------------
8 */
9
10 #include <sys/cdefs.h>
11 __FBSDID("$FreeBSD: releng/5.2/sys/kern/kern_tc.c 122610 2003-11-13 10:03:58Z phk $");
12
13 #include "opt_ntp.h"
14
15 #include <sys/param.h>
16 #include <sys/kernel.h>
17 #include <sys/sysctl.h>
18 #include <sys/systm.h>
19 #include <sys/timepps.h>
20 #include <sys/timetc.h>
21 #include <sys/timex.h>
22
23 /*
24 * A large step happens on boot. This constant detects such steps.
25 * It is relatively small so that ntp_update_second gets called enough
26 * in the typical 'missed a couple of seconds' case, but doesn't loop
27 * forever when the time step is large.
28 */
29 #define LARGE_STEP 200
30
31 /*
32 * Implement a dummy timecounter which we can use until we get a real one
33 * in the air. This allows the console and other early stuff to use
34 * time services.
35 */
36
37 static u_int
38 dummy_get_timecount(struct timecounter *tc)
39 {
40 static u_int now;
41
42 return (++now);
43 }
44
45 static struct timecounter dummy_timecounter = {
46 dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000
47 };
48
49 struct timehands {
50 /* These fields must be initialized by the driver. */
51 struct timecounter *th_counter;
52 int64_t th_adjustment;
53 u_int64_t th_scale;
54 u_int th_offset_count;
55 struct bintime th_offset;
56 struct timeval th_microtime;
57 struct timespec th_nanotime;
58 /* Fields not to be copied in tc_windup start with th_generation. */
59 volatile u_int th_generation;
60 struct timehands *th_next;
61 };
62
63 extern struct timehands th0;
64 static struct timehands th9 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th0};
65 static struct timehands th8 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th9};
66 static struct timehands th7 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th8};
67 static struct timehands th6 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th7};
68 static struct timehands th5 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th6};
69 static struct timehands th4 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th5};
70 static struct timehands th3 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th4};
71 static struct timehands th2 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th3};
72 static struct timehands th1 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th2};
73 static struct timehands th0 = {
74 &dummy_timecounter,
75 0,
76 (uint64_t)-1 / 1000000,
77 0,
78 {1, 0},
79 {0, 0},
80 {0, 0},
81 1,
82 &th1
83 };
84
85 static struct timehands *volatile timehands = &th0;
86 struct timecounter *timecounter = &dummy_timecounter;
87 static struct timecounter *timecounters = &dummy_timecounter;
88
89 time_t time_second = 1;
90 time_t time_uptime = 0;
91
92 static struct bintime boottimebin;
93 struct timeval boottime;
94 SYSCTL_STRUCT(_kern, KERN_BOOTTIME, boottime, CTLFLAG_RD,
95 &boottime, timeval, "System boottime");
96
97 SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW, 0, "");
98
99 #define TC_STATS(foo) \
100 static u_int foo; \
101 SYSCTL_UINT(_kern_timecounter, OID_AUTO, foo, CTLFLAG_RD, &foo, 0, "");\
102 struct __hack
103
104 TC_STATS(nbinuptime); TC_STATS(nnanouptime); TC_STATS(nmicrouptime);
105 TC_STATS(nbintime); TC_STATS(nnanotime); TC_STATS(nmicrotime);
106 TC_STATS(ngetbinuptime); TC_STATS(ngetnanouptime); TC_STATS(ngetmicrouptime);
107 TC_STATS(ngetbintime); TC_STATS(ngetnanotime); TC_STATS(ngetmicrotime);
108 TC_STATS(nsetclock);
109
110 #undef TC_STATS
111
112 static void tc_windup(void);
113
114 /*
115 * Return the difference between the timehands' counter value now and what
116 * was when we copied it to the timehands' offset_count.
117 */
118 static __inline u_int
119 tc_delta(struct timehands *th)
120 {
121 struct timecounter *tc;
122
123 tc = th->th_counter;
124 return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
125 tc->tc_counter_mask);
126 }
127
128 /*
129 * Functions for reading the time. We have to loop until we are sure that
130 * the timehands that we operated on was not updated under our feet. See
131 * the comment in <sys/time.h> for a description of these 12 functions.
132 */
133
134 void
135 binuptime(struct bintime *bt)
136 {
137 struct timehands *th;
138 u_int gen;
139
140 nbinuptime++;
141 do {
142 th = timehands;
143 gen = th->th_generation;
144 *bt = th->th_offset;
145 bintime_addx(bt, th->th_scale * tc_delta(th));
146 } while (gen == 0 || gen != th->th_generation);
147 }
148
149 void
150 nanouptime(struct timespec *tsp)
151 {
152 struct bintime bt;
153
154 nnanouptime++;
155 binuptime(&bt);
156 bintime2timespec(&bt, tsp);
157 }
158
159 void
160 microuptime(struct timeval *tvp)
161 {
162 struct bintime bt;
163
164 nmicrouptime++;
165 binuptime(&bt);
166 bintime2timeval(&bt, tvp);
167 }
168
169 void
170 bintime(struct bintime *bt)
171 {
172
173 nbintime++;
174 binuptime(bt);
175 bintime_add(bt, &boottimebin);
176 }
177
178 void
179 nanotime(struct timespec *tsp)
180 {
181 struct bintime bt;
182
183 nnanotime++;
184 bintime(&bt);
185 bintime2timespec(&bt, tsp);
186 }
187
188 void
189 microtime(struct timeval *tvp)
190 {
191 struct bintime bt;
192
193 nmicrotime++;
194 bintime(&bt);
195 bintime2timeval(&bt, tvp);
196 }
197
198 void
199 getbinuptime(struct bintime *bt)
200 {
201 struct timehands *th;
202 u_int gen;
203
204 ngetbinuptime++;
205 do {
206 th = timehands;
207 gen = th->th_generation;
208 *bt = th->th_offset;
209 } while (gen == 0 || gen != th->th_generation);
210 }
211
212 void
213 getnanouptime(struct timespec *tsp)
214 {
215 struct timehands *th;
216 u_int gen;
217
218 ngetnanouptime++;
219 do {
220 th = timehands;
221 gen = th->th_generation;
222 bintime2timespec(&th->th_offset, tsp);
223 } while (gen == 0 || gen != th->th_generation);
224 }
225
226 void
227 getmicrouptime(struct timeval *tvp)
228 {
229 struct timehands *th;
230 u_int gen;
231
232 ngetmicrouptime++;
233 do {
234 th = timehands;
235 gen = th->th_generation;
236 bintime2timeval(&th->th_offset, tvp);
237 } while (gen == 0 || gen != th->th_generation);
238 }
239
240 void
241 getbintime(struct bintime *bt)
242 {
243 struct timehands *th;
244 u_int gen;
245
246 ngetbintime++;
247 do {
248 th = timehands;
249 gen = th->th_generation;
250 *bt = th->th_offset;
251 } while (gen == 0 || gen != th->th_generation);
252 bintime_add(bt, &boottimebin);
253 }
254
255 void
256 getnanotime(struct timespec *tsp)
257 {
258 struct timehands *th;
259 u_int gen;
260
261 ngetnanotime++;
262 do {
263 th = timehands;
264 gen = th->th_generation;
265 *tsp = th->th_nanotime;
266 } while (gen == 0 || gen != th->th_generation);
267 }
268
269 void
270 getmicrotime(struct timeval *tvp)
271 {
272 struct timehands *th;
273 u_int gen;
274
275 ngetmicrotime++;
276 do {
277 th = timehands;
278 gen = th->th_generation;
279 *tvp = th->th_microtime;
280 } while (gen == 0 || gen != th->th_generation);
281 }
282
283 /*
284 * Initialize a new timecounter and possibly use it.
285 */
286 void
287 tc_init(struct timecounter *tc)
288 {
289 u_int u;
290
291 u = tc->tc_frequency / tc->tc_counter_mask;
292 /* XXX: We need some margin here, 10% is a guess */
293 u *= 11;
294 u /= 10;
295 if (u > hz && tc->tc_quality >= 0) {
296 tc->tc_quality = -2000;
297 if (bootverbose) {
298 printf("Timecounter \"%s\" frequency %ju Hz",
299 tc->tc_name, (uintmax_t)tc->tc_frequency);
300 printf(" -- Insufficient hz, needs at least %u\n", u);
301 }
302 } else if (tc->tc_quality >= 0 || bootverbose) {
303 printf("Timecounter \"%s\" frequency %ju Hz quality %d\n",
304 tc->tc_name, (uintmax_t)tc->tc_frequency,
305 tc->tc_quality);
306 }
307
308 tc->tc_next = timecounters;
309 timecounters = tc;
310 /*
311 * Never automatically use a timecounter with negative quality.
312 * Even though we run on the dummy counter, switching here may be
313 * worse since this timecounter may not be monotonous.
314 */
315 if (tc->tc_quality < 0)
316 return;
317 if (tc->tc_quality < timecounter->tc_quality)
318 return;
319 if (tc->tc_quality == timecounter->tc_quality &&
320 tc->tc_frequency < timecounter->tc_frequency)
321 return;
322 (void)tc->tc_get_timecount(tc);
323 (void)tc->tc_get_timecount(tc);
324 timecounter = tc;
325 }
326
327 /* Report the frequency of the current timecounter. */
328 u_int64_t
329 tc_getfrequency(void)
330 {
331
332 return (timehands->th_counter->tc_frequency);
333 }
334
335 /*
336 * Step our concept of UTC. This is done by modifying our estimate of
337 * when we booted. XXX: needs further work.
338 */
339 void
340 tc_setclock(struct timespec *ts)
341 {
342 struct timespec ts2;
343
344 nsetclock++;
345 nanouptime(&ts2);
346 boottime.tv_sec = ts->tv_sec - ts2.tv_sec;
347 /* XXX boottime should probably be a timespec. */
348 boottime.tv_usec = (ts->tv_nsec - ts2.tv_nsec) / 1000;
349 if (boottime.tv_usec < 0) {
350 boottime.tv_usec += 1000000;
351 boottime.tv_sec--;
352 }
353 timeval2bintime(&boottime, &boottimebin);
354
355 /* XXX fiddle all the little crinkly bits around the fiords... */
356 tc_windup();
357 }
358
359 /*
360 * Initialize the next struct timehands in the ring and make
361 * it the active timehands. Along the way we might switch to a different
362 * timecounter and/or do seconds processing in NTP. Slightly magic.
363 */
364 static void
365 tc_windup(void)
366 {
367 struct bintime bt;
368 struct timehands *th, *tho;
369 u_int64_t scale;
370 u_int delta, ncount, ogen;
371 int i;
372 time_t t;
373
374 /*
375 * Make the next timehands a copy of the current one, but do not
376 * overwrite the generation or next pointer. While we update
377 * the contents, the generation must be zero.
378 */
379 tho = timehands;
380 th = tho->th_next;
381 ogen = th->th_generation;
382 th->th_generation = 0;
383 bcopy(tho, th, offsetof(struct timehands, th_generation));
384
385 /*
386 * Capture a timecounter delta on the current timecounter and if
387 * changing timecounters, a counter value from the new timecounter.
388 * Update the offset fields accordingly.
389 */
390 delta = tc_delta(th);
391 if (th->th_counter != timecounter)
392 ncount = timecounter->tc_get_timecount(timecounter);
393 else
394 ncount = 0;
395 th->th_offset_count += delta;
396 th->th_offset_count &= th->th_counter->tc_counter_mask;
397 bintime_addx(&th->th_offset, th->th_scale * delta);
398
399 /*
400 * Hardware latching timecounters may not generate interrupts on
401 * PPS events, so instead we poll them. There is a finite risk that
402 * the hardware might capture a count which is later than the one we
403 * got above, and therefore possibly in the next NTP second which might
404 * have a different rate than the current NTP second. It doesn't
405 * matter in practice.
406 */
407 if (tho->th_counter->tc_poll_pps)
408 tho->th_counter->tc_poll_pps(tho->th_counter);
409
410 /*
411 * Deal with NTP second processing. The for loop normally
412 * iterates at most once, but in extreme situations it might
413 * keep NTP sane if timeouts are not run for several seconds.
414 * At boot, the time step can be large when the TOD hardware
415 * has been read, so on really large steps, we call
416 * ntp_update_second only twice. We need to call it twice in
417 * case we missed a leap second.
418 */
419 bt = th->th_offset;
420 bintime_add(&bt, &boottimebin);
421 i = bt.sec - tho->th_microtime.tv_sec;
422 if (i > LARGE_STEP)
423 i = 2;
424 for (; i > 0; i--) {
425 t = bt.sec;
426 ntp_update_second(&th->th_adjustment, &bt.sec);
427 if (bt.sec != t)
428 boottimebin.sec += bt.sec - t;
429 }
430 /* Update the UTC timestamps used by the get*() functions. */
431 /* XXX shouldn't do this here. Should force non-`get' versions. */
432 bintime2timeval(&bt, &th->th_microtime);
433 bintime2timespec(&bt, &th->th_nanotime);
434
435 /* Now is a good time to change timecounters. */
436 if (th->th_counter != timecounter) {
437 th->th_counter = timecounter;
438 th->th_offset_count = ncount;
439 }
440
441 /*-
442 * Recalculate the scaling factor. We want the number of 1/2^64
443 * fractions of a second per period of the hardware counter, taking
444 * into account the th_adjustment factor which the NTP PLL/adjtime(2)
445 * processing provides us with.
446 *
447 * The th_adjustment is nanoseconds per second with 32 bit binary
448 * fraction and we want 64 bit binary fraction of second:
449 *
450 * x = a * 2^32 / 10^9 = a * 4.294967296
451 *
452 * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
453 * we can only multiply by about 850 without overflowing, but that
454 * leaves suitably precise fractions for multiply before divide.
455 *
456 * Divide before multiply with a fraction of 2199/512 results in a
457 * systematic undercompensation of 10PPM of th_adjustment. On a
458 * 5000PPM adjustment this is a 0.05PPM error. This is acceptable.
459 *
460 * We happily sacrifice the lowest of the 64 bits of our result
461 * to the goddess of code clarity.
462 *
463 */
464 scale = (u_int64_t)1 << 63;
465 scale += (th->th_adjustment / 1024) * 2199;
466 scale /= th->th_counter->tc_frequency;
467 th->th_scale = scale * 2;
468
469 /*
470 * Now that the struct timehands is again consistent, set the new
471 * generation number, making sure to not make it zero.
472 */
473 if (++ogen == 0)
474 ogen = 1;
475 th->th_generation = ogen;
476
477 /* Go live with the new struct timehands. */
478 time_second = th->th_microtime.tv_sec;
479 time_uptime = th->th_offset.sec;
480 timehands = th;
481 }
482
483 /* Report or change the active timecounter hardware. */
484 static int
485 sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
486 {
487 char newname[32];
488 struct timecounter *newtc, *tc;
489 int error;
490
491 tc = timecounter;
492 strlcpy(newname, tc->tc_name, sizeof(newname));
493
494 error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
495 if (error != 0 || req->newptr == NULL ||
496 strcmp(newname, tc->tc_name) == 0)
497 return (error);
498 for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
499 if (strcmp(newname, newtc->tc_name) != 0)
500 continue;
501
502 /* Warm up new timecounter. */
503 (void)newtc->tc_get_timecount(newtc);
504 (void)newtc->tc_get_timecount(newtc);
505
506 timecounter = newtc;
507 return (0);
508 }
509 return (EINVAL);
510 }
511
512 SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW,
513 0, 0, sysctl_kern_timecounter_hardware, "A", "");
514
515
516 /* Report or change the active timecounter hardware. */
517 static int
518 sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS)
519 {
520 char buf[32], *spc;
521 struct timecounter *tc;
522 int error;
523
524 spc = "";
525 error = 0;
526 for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) {
527 sprintf(buf, "%s%s(%d)",
528 spc, tc->tc_name, tc->tc_quality);
529 error = SYSCTL_OUT(req, buf, strlen(buf));
530 spc = " ";
531 }
532 return (error);
533 }
534
535 SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD,
536 0, 0, sysctl_kern_timecounter_choice, "A", "");
537
538 /*
539 * RFC 2783 PPS-API implementation.
540 */
541
542 int
543 pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
544 {
545 pps_params_t *app;
546 struct pps_fetch_args *fapi;
547 #ifdef PPS_SYNC
548 struct pps_kcbind_args *kapi;
549 #endif
550
551 switch (cmd) {
552 case PPS_IOC_CREATE:
553 return (0);
554 case PPS_IOC_DESTROY:
555 return (0);
556 case PPS_IOC_SETPARAMS:
557 app = (pps_params_t *)data;
558 if (app->mode & ~pps->ppscap)
559 return (EINVAL);
560 pps->ppsparam = *app;
561 return (0);
562 case PPS_IOC_GETPARAMS:
563 app = (pps_params_t *)data;
564 *app = pps->ppsparam;
565 app->api_version = PPS_API_VERS_1;
566 return (0);
567 case PPS_IOC_GETCAP:
568 *(int*)data = pps->ppscap;
569 return (0);
570 case PPS_IOC_FETCH:
571 fapi = (struct pps_fetch_args *)data;
572 if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
573 return (EINVAL);
574 if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec)
575 return (EOPNOTSUPP);
576 pps->ppsinfo.current_mode = pps->ppsparam.mode;
577 fapi->pps_info_buf = pps->ppsinfo;
578 return (0);
579 case PPS_IOC_KCBIND:
580 #ifdef PPS_SYNC
581 kapi = (struct pps_kcbind_args *)data;
582 /* XXX Only root should be able to do this */
583 if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
584 return (EINVAL);
585 if (kapi->kernel_consumer != PPS_KC_HARDPPS)
586 return (EINVAL);
587 if (kapi->edge & ~pps->ppscap)
588 return (EINVAL);
589 pps->kcmode = kapi->edge;
590 return (0);
591 #else
592 return (EOPNOTSUPP);
593 #endif
594 default:
595 return (ENOTTY);
596 }
597 }
598
599 void
600 pps_init(struct pps_state *pps)
601 {
602 pps->ppscap |= PPS_TSFMT_TSPEC;
603 if (pps->ppscap & PPS_CAPTUREASSERT)
604 pps->ppscap |= PPS_OFFSETASSERT;
605 if (pps->ppscap & PPS_CAPTURECLEAR)
606 pps->ppscap |= PPS_OFFSETCLEAR;
607 }
608
609 void
610 pps_capture(struct pps_state *pps)
611 {
612 struct timehands *th;
613
614 th = timehands;
615 pps->capgen = th->th_generation;
616 pps->capth = th;
617 pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
618 if (pps->capgen != th->th_generation)
619 pps->capgen = 0;
620 }
621
622 void
623 pps_event(struct pps_state *pps, int event)
624 {
625 struct bintime bt;
626 struct timespec ts, *tsp, *osp;
627 u_int tcount, *pcount;
628 int foff, fhard;
629 pps_seq_t *pseq;
630
631 /* If the timecounter was wound up underneath us, bail out. */
632 if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
633 return;
634
635 /* Things would be easier with arrays. */
636 if (event == PPS_CAPTUREASSERT) {
637 tsp = &pps->ppsinfo.assert_timestamp;
638 osp = &pps->ppsparam.assert_offset;
639 foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
640 fhard = pps->kcmode & PPS_CAPTUREASSERT;
641 pcount = &pps->ppscount[0];
642 pseq = &pps->ppsinfo.assert_sequence;
643 } else {
644 tsp = &pps->ppsinfo.clear_timestamp;
645 osp = &pps->ppsparam.clear_offset;
646 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
647 fhard = pps->kcmode & PPS_CAPTURECLEAR;
648 pcount = &pps->ppscount[1];
649 pseq = &pps->ppsinfo.clear_sequence;
650 }
651
652 /*
653 * If the timecounter changed, we cannot compare the count values, so
654 * we have to drop the rest of the PPS-stuff until the next event.
655 */
656 if (pps->ppstc != pps->capth->th_counter) {
657 pps->ppstc = pps->capth->th_counter;
658 *pcount = pps->capcount;
659 pps->ppscount[2] = pps->capcount;
660 return;
661 }
662
663 /* Return if nothing really happened. */
664 if (*pcount == pps->capcount)
665 return;
666
667 /* Convert the count to a timespec. */
668 tcount = pps->capcount - pps->capth->th_offset_count;
669 tcount &= pps->capth->th_counter->tc_counter_mask;
670 bt = pps->capth->th_offset;
671 bintime_addx(&bt, pps->capth->th_scale * tcount);
672 bintime_add(&bt, &boottimebin);
673 bintime2timespec(&bt, &ts);
674
675 /* If the timecounter was wound up underneath us, bail out. */
676 if (pps->capgen != pps->capth->th_generation)
677 return;
678
679 *pcount = pps->capcount;
680 (*pseq)++;
681 *tsp = ts;
682
683 if (foff) {
684 timespecadd(tsp, osp);
685 if (tsp->tv_nsec < 0) {
686 tsp->tv_nsec += 1000000000;
687 tsp->tv_sec -= 1;
688 }
689 }
690 #ifdef PPS_SYNC
691 if (fhard) {
692 u_int64_t scale;
693
694 /*
695 * Feed the NTP PLL/FLL.
696 * The FLL wants to know how many (hardware) nanoseconds
697 * elapsed since the previous event.
698 */
699 tcount = pps->capcount - pps->ppscount[2];
700 pps->ppscount[2] = pps->capcount;
701 tcount &= pps->capth->th_counter->tc_counter_mask;
702 scale = (u_int64_t)1 << 63;
703 scale /= pps->capth->th_counter->tc_frequency;
704 scale *= 2;
705 bt.sec = 0;
706 bt.frac = 0;
707 bintime_addx(&bt, scale * tcount);
708 bintime2timespec(&bt, &ts);
709 hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
710 }
711 #endif
712 }
713
714 /*
715 * Timecounters need to be updated every so often to prevent the hardware
716 * counter from overflowing. Updating also recalculates the cached values
717 * used by the get*() family of functions, so their precision depends on
718 * the update frequency.
719 */
720
721 static int tc_tick;
722 SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0, "");
723
724 void
725 tc_ticktock(void)
726 {
727 static int count;
728
729 if (++count < tc_tick)
730 return;
731 count = 0;
732 tc_windup();
733 }
734
735 static void
736 inittimecounter(void *dummy)
737 {
738 u_int p;
739
740 /*
741 * Set the initial timeout to
742 * max(1, <approx. number of hardclock ticks in a millisecond>).
743 * People should probably not use the sysctl to set the timeout
744 * to smaller than its inital value, since that value is the
745 * smallest reasonable one. If they want better timestamps they
746 * should use the non-"get"* functions.
747 */
748 if (hz > 1000)
749 tc_tick = (hz + 500) / 1000;
750 else
751 tc_tick = 1;
752 p = (tc_tick * 1000000) / hz;
753 printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
754
755 /* warm up new timecounter (again) and get rolling. */
756 (void)timecounter->tc_get_timecount(timecounter);
757 (void)timecounter->tc_get_timecount(timecounter);
758 }
759
760 SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL)
Cache object: 0dcda3999ee9ab2dd232582be1f41c2e
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