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[PATCH] ntp: add time_adjust to tick length 

This folds update_ntp_one_tick() into second_overflow() and adds time_adjust
to the tick length, this makes time_next_adjust unnecessary.  This slightly
changes the adjtime() behaviour, instead of applying it to the next tick, it's
applied to the next second.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Roman Zippel 2006-09-30 23:28:25 -07:00 committed by Linus Torvalds
parent 3d3675cc3d
commit 8f807f8d21
3 changed files with 18 additions and 56 deletions
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1
include/linux/timex.h
View File

@ -217,7 +217,6 @@ extern long time_freq; /* frequency offset (scaled ppm) */
extern long time_reftime; /* time at last adjustment (s) */ extern long time_reftime; /* time at last adjustment (s) */
extern long time_adjust; /* The amount of adjtime left */ extern long time_adjust; /* The amount of adjtime left */
extern long time_next_adjust; /* Value for time_adjust at next tick */
extern void ntp_clear(void); extern void ntp_clear(void);
extern void ntp_update_frequency(void); extern void ntp_update_frequency(void);

71
kernel/time/ntp.c
View File

@ -22,8 +22,9 @@ unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */
unsigned long tick_nsec; /* ACTHZ period (nsec) */ unsigned long tick_nsec; /* ACTHZ period (nsec) */
static u64 tick_length, tick_length_base; static u64 tick_length, tick_length_base;
/* Don't completely fail for HZ > 500. */ #define MAX_TICKADJ 500 /* microsecs */
int tickadj = 500/HZ ? : 1; /* microsecs */ #define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \
TICK_LENGTH_SHIFT) / HZ)
/* /*
* phase-lock loop variables * phase-lock loop variables
@ -40,7 +41,6 @@ long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */
long time_freq; /* frequency offset (scaled ppm)*/ long time_freq; /* frequency offset (scaled ppm)*/
long time_reftime; /* time at last adjustment (s) */ long time_reftime; /* time at last adjustment (s) */
long time_adjust; long time_adjust;
long time_next_adjust;
/** /**
* ntp_clear - Clears the NTP state variables * ntp_clear - Clears the NTP state variables
@ -160,46 +160,19 @@ void second_overflow(void)
time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC); time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC);
time_offset -= time_adj; time_offset -= time_adj;
tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE); tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE);
}
/* if (unlikely(time_adjust)) {
* Returns how many microseconds we need to add to xtime this tick if (time_adjust > MAX_TICKADJ) {
* in doing an adjustment requested with adjtime. time_adjust -= MAX_TICKADJ;
*/ tick_length += MAX_TICKADJ_SCALED;
static long adjtime_adjustment(void) } else if (time_adjust < -MAX_TICKADJ) {
{ time_adjust += MAX_TICKADJ;
long time_adjust_step; tick_length -= MAX_TICKADJ_SCALED;
} else {
time_adjust_step = time_adjust; time_adjust = 0;
if (time_adjust_step) { tick_length += (s64)(time_adjust * NSEC_PER_USEC /
/* HZ) << TICK_LENGTH_SHIFT;
* We are doing an adjtime thing. Prepare time_adjust_step to }
* be within bounds. Note that a positive time_adjust means we
* want the clock to run faster.
*
* Limit the amount of the step to be in the range
* -tickadj .. +tickadj
*/
time_adjust_step = min(time_adjust_step, (long)tickadj);
time_adjust_step = max(time_adjust_step, (long)-tickadj);
}
return time_adjust_step;
}
/* in the NTP reference this is called "hardclock()" */
void update_ntp_one_tick(void)
{
long time_adjust_step;
time_adjust_step = adjtime_adjustment();
if (time_adjust_step)
/* Reduce by this step the amount of time left */
time_adjust -= time_adjust_step;
/* Changes by adjtime() do not take effect till next tick. */
if (time_next_adjust != 0) {
time_adjust = time_next_adjust;
time_next_adjust = 0;
} }
} }
@ -213,14 +186,7 @@ void update_ntp_one_tick(void)
*/ */
u64 current_tick_length(void) u64 current_tick_length(void)
{ {
u64 ret; return tick_length;
/* calculate the finest interval NTP will allow.
*/
ret = tick_length;
ret += (u64)(adjtime_adjustment() * 1000) << TICK_LENGTH_SHIFT;
return ret;
} }
@ -263,7 +229,7 @@ int do_adjtimex(struct timex *txc)
result = time_state; /* mostly `TIME_OK' */ result = time_state; /* mostly `TIME_OK' */
/* Save for later - semantics of adjtime is to return old value */ /* Save for later - semantics of adjtime is to return old value */
save_adjust = time_next_adjust ? time_next_adjust : time_adjust; save_adjust = time_adjust;
#if 0 /* STA_CLOCKERR is never set yet */ #if 0 /* STA_CLOCKERR is never set yet */
time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */ time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */
@ -310,8 +276,7 @@ int do_adjtimex(struct timex *txc)
if (txc->modes & ADJ_OFFSET) { /* values checked earlier */ if (txc->modes & ADJ_OFFSET) { /* values checked earlier */
if (txc->modes == ADJ_OFFSET_SINGLESHOT) { if (txc->modes == ADJ_OFFSET_SINGLESHOT) {
/* adjtime() is independent from ntp_adjtime() */ /* adjtime() is independent from ntp_adjtime() */
if ((time_next_adjust = txc->offset) == 0) time_adjust = txc->offset;
time_adjust = 0;
} }
else if (time_status & STA_PLL) { else if (time_status & STA_PLL) {
ltemp = txc->offset; ltemp = txc->offset;

2
kernel/timer.c
View File

@ -937,8 +937,6 @@ static void update_wall_time(void)
/* interpolator bits */ /* interpolator bits */
time_interpolator_update(clock->xtime_interval time_interpolator_update(clock->xtime_interval
>> clock->shift); >> clock->shift);
/* increment the NTP state machine */
update_ntp_one_tick();
/* accumulate error between NTP and clock interval */ /* accumulate error between NTP and clock interval */
clock->error += current_tick_length(); clock->error += current_tick_length();