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|
/* $OpenBSD: kern_tc.c,v 1.29 2016/07/06 15:53:01 tedu Exp $ */
/*
* Copyright (c) 2000 Poul-Henning Kamp <phk@FreeBSD.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/*
* If we meet some day, and you think this stuff is worth it, you
* can buy me a beer in return. Poul-Henning Kamp
*/
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/timeout.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <sys/timetc.h>
#include <sys/malloc.h>
#include <dev/rndvar.h>
/*
* A large step happens on boot. This constant detects such steps.
* It is relatively small so that ntp_update_second gets called enough
* in the typical 'missed a couple of seconds' case, but doesn't loop
* forever when the time step is large.
*/
#define LARGE_STEP 200
u_int dummy_get_timecount(struct timecounter *);
void ntp_update_second(int64_t *, time_t *);
int sysctl_tc_hardware(void *, size_t *, void *, size_t);
int sysctl_tc_choice(void *, size_t *, void *, size_t);
/*
* Implement a dummy timecounter which we can use until we get a real one
* in the air. This allows the console and other early stuff to use
* time services.
*/
u_int
dummy_get_timecount(struct timecounter *tc)
{
static u_int now;
return (++now);
}
static struct timecounter dummy_timecounter = {
dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000
};
struct timehands {
/* These fields must be initialized by the driver. */
struct timecounter *th_counter;
int64_t th_adjustment;
u_int64_t th_scale;
u_int th_offset_count;
struct bintime th_offset;
struct timeval th_microtime;
struct timespec th_nanotime;
/* Fields not to be copied in tc_windup start with th_generation. */
volatile u_int th_generation;
struct timehands *th_next;
};
static struct timehands th0;
static struct timehands th9 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th0};
static struct timehands th8 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th9};
static struct timehands th7 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th8};
static struct timehands th6 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th7};
static struct timehands th5 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th6};
static struct timehands th4 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th5};
static struct timehands th3 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th4};
static struct timehands th2 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th3};
static struct timehands th1 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th2};
static struct timehands th0 = {
&dummy_timecounter,
0,
(uint64_t)-1 / 1000000,
0,
{1, 0},
{0, 0},
{0, 0},
1,
&th1
};
static struct timehands *volatile timehands = &th0;
struct timecounter *timecounter = &dummy_timecounter;
static struct timecounter *timecounters = &dummy_timecounter;
volatile time_t time_second = 1;
volatile time_t time_uptime = 0;
struct bintime naptime;
static struct bintime boottimebin;
static int timestepwarnings;
void tc_windup(void);
/*
* Return the difference between the timehands' counter value now and what
* was when we copied it to the timehands' offset_count.
*/
static __inline u_int
tc_delta(struct timehands *th)
{
struct timecounter *tc;
tc = th->th_counter;
return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
tc->tc_counter_mask);
}
/*
* Functions for reading the time. We have to loop until we are sure that
* the timehands that we operated on was not updated under our feet. See
* the comment in <sys/time.h> for a description of these 12 functions.
*/
void
binuptime(struct bintime *bt)
{
struct timehands *th;
u_int gen;
do {
th = timehands;
gen = th->th_generation;
*bt = th->th_offset;
bintime_addx(bt, th->th_scale * tc_delta(th));
} while (gen == 0 || gen != th->th_generation);
}
void
nanouptime(struct timespec *tsp)
{
struct bintime bt;
binuptime(&bt);
bintime2timespec(&bt, tsp);
}
void
microuptime(struct timeval *tvp)
{
struct bintime bt;
binuptime(&bt);
bintime2timeval(&bt, tvp);
}
void
bintime(struct bintime *bt)
{
binuptime(bt);
bintime_add(bt, &boottimebin);
}
void
nanotime(struct timespec *tsp)
{
struct bintime bt;
bintime(&bt);
bintime2timespec(&bt, tsp);
}
void
microtime(struct timeval *tvp)
{
struct bintime bt;
bintime(&bt);
bintime2timeval(&bt, tvp);
}
void
getnanouptime(struct timespec *tsp)
{
struct timehands *th;
u_int gen;
do {
th = timehands;
gen = th->th_generation;
bintime2timespec(&th->th_offset, tsp);
} while (gen == 0 || gen != th->th_generation);
}
void
getmicrouptime(struct timeval *tvp)
{
struct timehands *th;
u_int gen;
do {
th = timehands;
gen = th->th_generation;
bintime2timeval(&th->th_offset, tvp);
} while (gen == 0 || gen != th->th_generation);
}
void
getnanotime(struct timespec *tsp)
{
struct timehands *th;
u_int gen;
do {
th = timehands;
gen = th->th_generation;
*tsp = th->th_nanotime;
} while (gen == 0 || gen != th->th_generation);
}
void
getmicrotime(struct timeval *tvp)
{
struct timehands *th;
u_int gen;
do {
th = timehands;
gen = th->th_generation;
*tvp = th->th_microtime;
} while (gen == 0 || gen != th->th_generation);
}
/*
* Initialize a new timecounter and possibly use it.
*/
void
tc_init(struct timecounter *tc)
{
u_int u;
u = tc->tc_frequency / tc->tc_counter_mask;
/* XXX: We need some margin here, 10% is a guess */
u *= 11;
u /= 10;
if (tc->tc_quality >= 0) {
if (u > hz) {
tc->tc_quality = -2000;
printf("Timecounter \"%s\" frequency %lu Hz",
tc->tc_name, (unsigned long)tc->tc_frequency);
printf(" -- Insufficient hz, needs at least %u\n", u);
}
}
tc->tc_next = timecounters;
timecounters = tc;
/*
* Never automatically use a timecounter with negative quality.
* Even though we run on the dummy counter, switching here may be
* worse since this timecounter may not be monotonic.
*/
if (tc->tc_quality < 0)
return;
if (tc->tc_quality < timecounter->tc_quality)
return;
if (tc->tc_quality == timecounter->tc_quality &&
tc->tc_frequency < timecounter->tc_frequency)
return;
(void)tc->tc_get_timecount(tc);
add_timer_randomness(tc->tc_get_timecount(tc));
timecounter = tc;
}
/* Report the frequency of the current timecounter. */
u_int64_t
tc_getfrequency(void)
{
return (timehands->th_counter->tc_frequency);
}
/*
* Step our concept of UTC, aka the realtime clock.
* This is done by modifying our estimate of when we booted.
* XXX: not locked.
*/
void
tc_setrealtimeclock(struct timespec *ts)
{
struct timespec ts2;
struct bintime bt, bt2;
binuptime(&bt2);
timespec2bintime(ts, &bt);
bintime_sub(&bt, &bt2);
bintime_add(&bt2, &boottimebin);
boottimebin = bt;
bintime2timespec(&bt, &boottime);
add_timer_randomness(ts->tv_sec);
/* XXX fiddle all the little crinkly bits around the fiords... */
tc_windup();
if (timestepwarnings) {
bintime2timespec(&bt2, &ts2);
log(LOG_INFO, "Time stepped from %lld.%09ld to %lld.%09ld\n",
(long long)ts2.tv_sec, ts2.tv_nsec,
(long long)ts->tv_sec, ts->tv_nsec);
}
}
/*
* Step the monotonic and realtime clocks, triggering any timeouts that
* should have occurred across the interval.
* XXX: not locked.
*/
void
tc_setclock(struct timespec *ts)
{
struct bintime bt, bt2;
#ifndef SMALL_KERNEL
long long adj_ticks;
#endif
/*
* When we're called for the first time, during boot when
* the root partition is mounted, boottime is still zero:
* we just need to set it.
*/
if (boottimebin.sec == 0) {
tc_setrealtimeclock(ts);
return;
}
add_timer_randomness(ts->tv_sec);
timespec2bintime(ts, &bt);
bintime_sub(&bt, &boottimebin);
bt2 = timehands->th_offset;
timehands->th_offset = bt;
/* XXX fiddle all the little crinkly bits around the fiords... */
tc_windup();
#ifndef SMALL_KERNEL
/* convert the bintime to ticks */
bintime_sub(&bt, &bt2);
bintime_add(&naptime, &bt);
adj_ticks = (uint64_t)hz * bt.sec +
(((uint64_t)1000000 * (uint32_t)(bt.frac >> 32)) >> 32) / tick;
if (adj_ticks > 0) {
if (adj_ticks > INT_MAX)
adj_ticks = INT_MAX;
timeout_adjust_ticks(adj_ticks);
}
#endif
}
/*
* Initialize the next struct timehands in the ring and make
* it the active timehands. Along the way we might switch to a different
* timecounter and/or do seconds processing in NTP. Slightly magic.
*/
void
tc_windup(void)
{
struct bintime bt;
struct timehands *th, *tho;
u_int64_t scale;
u_int delta, ncount, ogen;
int i;
#ifdef leapsecs
time_t t;
#endif
/*
* Make the next timehands a copy of the current one, but do not
* overwrite the generation or next pointer. While we update
* the contents, the generation must be zero.
*/
tho = timehands;
th = tho->th_next;
ogen = th->th_generation;
th->th_generation = 0;
memcpy(th, tho, offsetof(struct timehands, th_generation));
/*
* Capture a timecounter delta on the current timecounter and if
* changing timecounters, a counter value from the new timecounter.
* Update the offset fields accordingly.
*/
delta = tc_delta(th);
if (th->th_counter != timecounter)
ncount = timecounter->tc_get_timecount(timecounter);
else
ncount = 0;
th->th_offset_count += delta;
th->th_offset_count &= th->th_counter->tc_counter_mask;
bintime_addx(&th->th_offset, th->th_scale * delta);
#ifdef notyet
/*
* Hardware latching timecounters may not generate interrupts on
* PPS events, so instead we poll them. There is a finite risk that
* the hardware might capture a count which is later than the one we
* got above, and therefore possibly in the next NTP second which might
* have a different rate than the current NTP second. It doesn't
* matter in practice.
*/
if (tho->th_counter->tc_poll_pps)
tho->th_counter->tc_poll_pps(tho->th_counter);
#endif
/*
* Deal with NTP second processing. The for loop normally
* iterates at most once, but in extreme situations it might
* keep NTP sane if timeouts are not run for several seconds.
* At boot, the time step can be large when the TOD hardware
* has been read, so on really large steps, we call
* ntp_update_second only twice. We need to call it twice in
* case we missed a leap second.
*/
bt = th->th_offset;
bintime_add(&bt, &boottimebin);
i = bt.sec - tho->th_microtime.tv_sec;
if (i > LARGE_STEP)
i = 2;
for (; i > 0; i--)
ntp_update_second(&th->th_adjustment, &bt.sec);
/* Update the UTC timestamps used by the get*() functions. */
/* XXX shouldn't do this here. Should force non-`get' versions. */
bintime2timeval(&bt, &th->th_microtime);
bintime2timespec(&bt, &th->th_nanotime);
/* Now is a good time to change timecounters. */
if (th->th_counter != timecounter) {
th->th_counter = timecounter;
th->th_offset_count = ncount;
}
/*-
* Recalculate the scaling factor. We want the number of 1/2^64
* fractions of a second per period of the hardware counter, taking
* into account the th_adjustment factor which the NTP PLL/adjtime(2)
* processing provides us with.
*
* The th_adjustment is nanoseconds per second with 32 bit binary
* fraction and we want 64 bit binary fraction of second:
*
* x = a * 2^32 / 10^9 = a * 4.294967296
*
* The range of th_adjustment is +/- 5000PPM so inside a 64bit int
* we can only multiply by about 850 without overflowing, but that
* leaves suitably precise fractions for multiply before divide.
*
* Divide before multiply with a fraction of 2199/512 results in a
* systematic undercompensation of 10PPM of th_adjustment. On a
* 5000PPM adjustment this is a 0.05PPM error. This is acceptable.
*
* We happily sacrifice the lowest of the 64 bits of our result
* to the goddess of code clarity.
*
*/
scale = (u_int64_t)1 << 63;
scale += (th->th_adjustment / 1024) * 2199;
scale /= th->th_counter->tc_frequency;
th->th_scale = scale * 2;
/*
* Now that the struct timehands is again consistent, set the new
* generation number, making sure to not make it zero.
*/
if (++ogen == 0)
ogen = 1;
th->th_generation = ogen;
/* Go live with the new struct timehands. */
time_second = th->th_microtime.tv_sec;
time_uptime = th->th_offset.sec;
timehands = th;
}
/* Report or change the active timecounter hardware. */
int
sysctl_tc_hardware(void *oldp, size_t *oldlenp, void *newp, size_t newlen)
{
char newname[32];
struct timecounter *newtc, *tc;
int error;
tc = timecounter;
strlcpy(newname, tc->tc_name, sizeof(newname));
error = sysctl_string(oldp, oldlenp, newp, newlen, newname, sizeof(newname));
if (error != 0 || strcmp(newname, tc->tc_name) == 0)
return (error);
for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
if (strcmp(newname, newtc->tc_name) != 0)
continue;
/* Warm up new timecounter. */
(void)newtc->tc_get_timecount(newtc);
(void)newtc->tc_get_timecount(newtc);
timecounter = newtc;
return (0);
}
return (EINVAL);
}
/* Report or change the active timecounter hardware. */
int
sysctl_tc_choice(void *oldp, size_t *oldlenp, void *newp, size_t newlen)
{
char buf[32], *spc, *choices;
struct timecounter *tc;
int error, maxlen;
spc = "";
maxlen = 0;
for (tc = timecounters; tc != NULL; tc = tc->tc_next)
maxlen += sizeof(buf);
choices = malloc(maxlen, M_TEMP, M_WAITOK);
*choices = '\0';
for (tc = timecounters; tc != NULL; tc = tc->tc_next) {
snprintf(buf, sizeof(buf), "%s%s(%d)",
spc, tc->tc_name, tc->tc_quality);
spc = " ";
strlcat(choices, buf, maxlen);
}
error = sysctl_rdstring(oldp, oldlenp, newp, choices);
free(choices, M_TEMP, maxlen);
return (error);
}
/*
* Timecounters need to be updated every so often to prevent the hardware
* counter from overflowing. Updating also recalculates the cached values
* used by the get*() family of functions, so their precision depends on
* the update frequency.
*/
static int tc_tick;
void
tc_ticktock(void)
{
static int count;
if (++count < tc_tick)
return;
count = 0;
tc_windup();
}
void
inittimecounter(void)
{
#ifdef DEBUG
u_int p;
#endif
/*
* Set the initial timeout to
* max(1, <approx. number of hardclock ticks in a millisecond>).
* People should probably not use the sysctl to set the timeout
* to smaller than its initial value, since that value is the
* smallest reasonable one. If they want better timestamps they
* should use the non-"get"* functions.
*/
if (hz > 1000)
tc_tick = (hz + 500) / 1000;
else
tc_tick = 1;
#ifdef DEBUG
p = (tc_tick * 1000000) / hz;
printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
#endif
/* warm up new timecounter (again) and get rolling. */
(void)timecounter->tc_get_timecount(timecounter);
(void)timecounter->tc_get_timecount(timecounter);
}
/*
* Return timecounter-related information.
*/
int
sysctl_tc(int *name, u_int namelen, void *oldp, size_t *oldlenp,
void *newp, size_t newlen)
{
if (namelen != 1)
return (ENOTDIR);
switch (name[0]) {
case KERN_TIMECOUNTER_TICK:
return (sysctl_rdint(oldp, oldlenp, newp, tc_tick));
case KERN_TIMECOUNTER_TIMESTEPWARNINGS:
return (sysctl_int(oldp, oldlenp, newp, newlen,
×tepwarnings));
case KERN_TIMECOUNTER_HARDWARE:
return (sysctl_tc_hardware(oldp, oldlenp, newp, newlen));
case KERN_TIMECOUNTER_CHOICE:
return (sysctl_tc_choice(oldp, oldlenp, newp, newlen));
default:
return (EOPNOTSUPP);
}
/* NOTREACHED */
}
void
ntp_update_second(int64_t *adjust, time_t *sec)
{
int64_t adj;
/* Skew time according to any adjtime(2) adjustments. */
if (adjtimedelta > 0)
adj = MIN(5000, adjtimedelta);
else
adj = MAX(-5000, adjtimedelta);
adjtimedelta -= adj;
*adjust = (adj * 1000) << 32;
*adjust += timecounter->tc_freq_adj;
}
int
tc_adjfreq(int64_t *old, int64_t *new)
{
if (old != NULL) {
*old = timecounter->tc_freq_adj;
}
if (new != NULL) {
timecounter->tc_freq_adj = *new;
}
return 0;
}
|