linux/kernel/time/ntp.c
Peter Zijlstra ca109491f6 hrtimer: removing all ur callback modes
Impact: cleanup, move all hrtimer processing into hardirq context

This is an attempt at removing some of the hrtimer complexity by
reducing the number of callback modes to 1.

This means that all hrtimer callback functions will be ran from HARD-irq
context.

I went through all the 30 odd hrtimer callback functions in the kernel
and saw only one that I'm not quite sure of, which is the one in
net/can/bcm.c - hence I'm CC-ing the folks responsible for that code.

Furthermore, the hrtimer core now calls callbacks directly with IRQs
disabled in case you try to enqueue an expired timer. If this timer is a
periodic timer (which should use hrtimer_forward() to advance its time)
then it might be possible to end up in an inf. recursive loop due to the
fact that hrtimer_forward() doesn't round up to the next timer
granularity, and therefore keeps on calling the callback - obviously
this needs a fix.

Aside from that, this seems to compile and actually boot on my dual core
test box - although I'm sure there are some bugs in, me not hitting any
makes me certain :-)

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-25 15:45:46 +01:00

454 lines
12 KiB
C

/*
* linux/kernel/time/ntp.c
*
* NTP state machine interfaces and logic.
*
* This code was mainly moved from kernel/timer.c and kernel/time.c
* Please see those files for relevant copyright info and historical
* changelogs.
*/
#include <linux/mm.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/jiffies.h>
#include <linux/hrtimer.h>
#include <linux/capability.h>
#include <linux/math64.h>
#include <linux/clocksource.h>
#include <linux/workqueue.h>
#include <asm/timex.h>
/*
* Timekeeping variables
*/
unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */
unsigned long tick_nsec; /* ACTHZ period (nsec) */
u64 tick_length;
static u64 tick_length_base;
static struct hrtimer leap_timer;
#define MAX_TICKADJ 500 /* microsecs */
#define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \
NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
/*
* phase-lock loop variables
*/
/* TIME_ERROR prevents overwriting the CMOS clock */
static int time_state = TIME_OK; /* clock synchronization status */
int time_status = STA_UNSYNC; /* clock status bits */
static long time_tai; /* TAI offset (s) */
static s64 time_offset; /* time adjustment (ns) */
static long time_constant = 2; /* pll time constant */
long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */
long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */
static s64 time_freq; /* frequency offset (scaled ns/s)*/
static long time_reftime; /* time at last adjustment (s) */
long time_adjust;
static long ntp_tick_adj;
static void ntp_update_frequency(void)
{
u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
<< NTP_SCALE_SHIFT;
second_length += (s64)ntp_tick_adj << NTP_SCALE_SHIFT;
second_length += time_freq;
tick_length_base = second_length;
tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
tick_length_base = div_u64(tick_length_base, NTP_INTERVAL_FREQ);
}
static void ntp_update_offset(long offset)
{
long mtemp;
s64 freq_adj;
if (!(time_status & STA_PLL))
return;
if (!(time_status & STA_NANO))
offset *= NSEC_PER_USEC;
/*
* Scale the phase adjustment and
* clamp to the operating range.
*/
offset = min(offset, MAXPHASE);
offset = max(offset, -MAXPHASE);
/*
* Select how the frequency is to be controlled
* and in which mode (PLL or FLL).
*/
if (time_status & STA_FREQHOLD || time_reftime == 0)
time_reftime = xtime.tv_sec;
mtemp = xtime.tv_sec - time_reftime;
time_reftime = xtime.tv_sec;
freq_adj = (s64)offset * mtemp;
freq_adj <<= NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant);
time_status &= ~STA_MODE;
if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) {
freq_adj += div_s64((s64)offset << (NTP_SCALE_SHIFT - SHIFT_FLL),
mtemp);
time_status |= STA_MODE;
}
freq_adj += time_freq;
freq_adj = min(freq_adj, MAXFREQ_SCALED);
time_freq = max(freq_adj, -MAXFREQ_SCALED);
time_offset = div_s64((s64)offset << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
}
/**
* ntp_clear - Clears the NTP state variables
*
* Must be called while holding a write on the xtime_lock
*/
void ntp_clear(void)
{
time_adjust = 0; /* stop active adjtime() */
time_status |= STA_UNSYNC;
time_maxerror = NTP_PHASE_LIMIT;
time_esterror = NTP_PHASE_LIMIT;
ntp_update_frequency();
tick_length = tick_length_base;
time_offset = 0;
}
/*
* Leap second processing. If in leap-insert state at the end of the
* day, the system clock is set back one second; if in leap-delete
* state, the system clock is set ahead one second.
*/
static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
{
enum hrtimer_restart res = HRTIMER_NORESTART;
write_seqlock(&xtime_lock);
switch (time_state) {
case TIME_OK:
break;
case TIME_INS:
xtime.tv_sec--;
wall_to_monotonic.tv_sec++;
time_state = TIME_OOP;
printk(KERN_NOTICE "Clock: "
"inserting leap second 23:59:60 UTC\n");
hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC);
res = HRTIMER_RESTART;
break;
case TIME_DEL:
xtime.tv_sec++;
time_tai--;
wall_to_monotonic.tv_sec--;
time_state = TIME_WAIT;
printk(KERN_NOTICE "Clock: "
"deleting leap second 23:59:59 UTC\n");
break;
case TIME_OOP:
time_tai++;
time_state = TIME_WAIT;
/* fall through */
case TIME_WAIT:
if (!(time_status & (STA_INS | STA_DEL)))
time_state = TIME_OK;
break;
}
update_vsyscall(&xtime, clock);
write_sequnlock(&xtime_lock);
return res;
}
/*
* this routine handles the overflow of the microsecond field
*
* The tricky bits of code to handle the accurate clock support
* were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
* They were originally developed for SUN and DEC kernels.
* All the kudos should go to Dave for this stuff.
*/
void second_overflow(void)
{
s64 time_adj;
/* Bump the maxerror field */
time_maxerror += MAXFREQ / NSEC_PER_USEC;
if (time_maxerror > NTP_PHASE_LIMIT) {
time_maxerror = NTP_PHASE_LIMIT;
time_status |= STA_UNSYNC;
}
/*
* Compute the phase adjustment for the next second. The offset is
* reduced by a fixed factor times the time constant.
*/
tick_length = tick_length_base;
time_adj = shift_right(time_offset, SHIFT_PLL + time_constant);
time_offset -= time_adj;
tick_length += time_adj;
if (unlikely(time_adjust)) {
if (time_adjust > MAX_TICKADJ) {
time_adjust -= MAX_TICKADJ;
tick_length += MAX_TICKADJ_SCALED;
} else if (time_adjust < -MAX_TICKADJ) {
time_adjust += MAX_TICKADJ;
tick_length -= MAX_TICKADJ_SCALED;
} else {
tick_length += (s64)(time_adjust * NSEC_PER_USEC /
NTP_INTERVAL_FREQ) << NTP_SCALE_SHIFT;
time_adjust = 0;
}
}
}
#ifdef CONFIG_GENERIC_CMOS_UPDATE
/* Disable the cmos update - used by virtualization and embedded */
int no_sync_cmos_clock __read_mostly;
static void sync_cmos_clock(struct work_struct *work);
static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
static void sync_cmos_clock(struct work_struct *work)
{
struct timespec now, next;
int fail = 1;
/*
* If we have an externally synchronized Linux clock, then update
* CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
* called as close as possible to 500 ms before the new second starts.
* This code is run on a timer. If the clock is set, that timer
* may not expire at the correct time. Thus, we adjust...
*/
if (!ntp_synced())
/*
* Not synced, exit, do not restart a timer (if one is
* running, let it run out).
*/
return;
getnstimeofday(&now);
if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
fail = update_persistent_clock(now);
next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
if (next.tv_nsec <= 0)
next.tv_nsec += NSEC_PER_SEC;
if (!fail)
next.tv_sec = 659;
else
next.tv_sec = 0;
if (next.tv_nsec >= NSEC_PER_SEC) {
next.tv_sec++;
next.tv_nsec -= NSEC_PER_SEC;
}
schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
}
static void notify_cmos_timer(void)
{
if (!no_sync_cmos_clock)
schedule_delayed_work(&sync_cmos_work, 0);
}
#else
static inline void notify_cmos_timer(void) { }
#endif
/* adjtimex mainly allows reading (and writing, if superuser) of
* kernel time-keeping variables. used by xntpd.
*/
int do_adjtimex(struct timex *txc)
{
struct timespec ts;
int result;
/* Validate the data before disabling interrupts */
if (txc->modes & ADJ_ADJTIME) {
/* singleshot must not be used with any other mode bits */
if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
return -EINVAL;
if (!(txc->modes & ADJ_OFFSET_READONLY) &&
!capable(CAP_SYS_TIME))
return -EPERM;
} else {
/* In order to modify anything, you gotta be super-user! */
if (txc->modes && !capable(CAP_SYS_TIME))
return -EPERM;
/* if the quartz is off by more than 10% something is VERY wrong! */
if (txc->modes & ADJ_TICK &&
(txc->tick < 900000/USER_HZ ||
txc->tick > 1100000/USER_HZ))
return -EINVAL;
if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
hrtimer_cancel(&leap_timer);
}
getnstimeofday(&ts);
write_seqlock_irq(&xtime_lock);
/* If there are input parameters, then process them */
if (txc->modes & ADJ_ADJTIME) {
long save_adjust = time_adjust;
if (!(txc->modes & ADJ_OFFSET_READONLY)) {
/* adjtime() is independent from ntp_adjtime() */
time_adjust = txc->offset;
ntp_update_frequency();
}
txc->offset = save_adjust;
goto adj_done;
}
if (txc->modes) {
long sec;
if (txc->modes & ADJ_STATUS) {
if ((time_status & STA_PLL) &&
!(txc->status & STA_PLL)) {
time_state = TIME_OK;
time_status = STA_UNSYNC;
}
/* only set allowed bits */
time_status &= STA_RONLY;
time_status |= txc->status & ~STA_RONLY;
switch (time_state) {
case TIME_OK:
start_timer:
sec = ts.tv_sec;
if (time_status & STA_INS) {
time_state = TIME_INS;
sec += 86400 - sec % 86400;
hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS);
} else if (time_status & STA_DEL) {
time_state = TIME_DEL;
sec += 86400 - (sec + 1) % 86400;
hrtimer_start(&leap_timer, ktime_set(sec, 0), HRTIMER_MODE_ABS);
}
break;
case TIME_INS:
case TIME_DEL:
time_state = TIME_OK;
goto start_timer;
break;
case TIME_WAIT:
if (!(time_status & (STA_INS | STA_DEL)))
time_state = TIME_OK;
break;
case TIME_OOP:
hrtimer_restart(&leap_timer);
break;
}
}
if (txc->modes & ADJ_NANO)
time_status |= STA_NANO;
if (txc->modes & ADJ_MICRO)
time_status &= ~STA_NANO;
if (txc->modes & ADJ_FREQUENCY) {
time_freq = (s64)txc->freq * PPM_SCALE;
time_freq = min(time_freq, MAXFREQ_SCALED);
time_freq = max(time_freq, -MAXFREQ_SCALED);
}
if (txc->modes & ADJ_MAXERROR)
time_maxerror = txc->maxerror;
if (txc->modes & ADJ_ESTERROR)
time_esterror = txc->esterror;
if (txc->modes & ADJ_TIMECONST) {
time_constant = txc->constant;
if (!(time_status & STA_NANO))
time_constant += 4;
time_constant = min(time_constant, (long)MAXTC);
time_constant = max(time_constant, 0l);
}
if (txc->modes & ADJ_TAI && txc->constant > 0)
time_tai = txc->constant;
if (txc->modes & ADJ_OFFSET)
ntp_update_offset(txc->offset);
if (txc->modes & ADJ_TICK)
tick_usec = txc->tick;
if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
ntp_update_frequency();
}
txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
NTP_SCALE_SHIFT);
if (!(time_status & STA_NANO))
txc->offset /= NSEC_PER_USEC;
adj_done:
result = time_state; /* mostly `TIME_OK' */
if (time_status & (STA_UNSYNC|STA_CLOCKERR))
result = TIME_ERROR;
txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
(s64)PPM_SCALE_INV, NTP_SCALE_SHIFT);
txc->maxerror = time_maxerror;
txc->esterror = time_esterror;
txc->status = time_status;
txc->constant = time_constant;
txc->precision = 1;
txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
txc->tick = tick_usec;
txc->tai = time_tai;
/* PPS is not implemented, so these are zero */
txc->ppsfreq = 0;
txc->jitter = 0;
txc->shift = 0;
txc->stabil = 0;
txc->jitcnt = 0;
txc->calcnt = 0;
txc->errcnt = 0;
txc->stbcnt = 0;
write_sequnlock_irq(&xtime_lock);
txc->time.tv_sec = ts.tv_sec;
txc->time.tv_usec = ts.tv_nsec;
if (!(time_status & STA_NANO))
txc->time.tv_usec /= NSEC_PER_USEC;
notify_cmos_timer();
return result;
}
static int __init ntp_tick_adj_setup(char *str)
{
ntp_tick_adj = simple_strtol(str, NULL, 0);
return 1;
}
__setup("ntp_tick_adj=", ntp_tick_adj_setup);
void __init ntp_init(void)
{
ntp_clear();
hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
leap_timer.function = ntp_leap_second;
}