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ntp: handle leap second via timer

Remove the leap second handling from second_overflow(), which doesn't have to
check for it every second anymore.  With CONFIG_NO_HZ this also makes sure the
leap second is handled close to the full second.  Additionally this makes it
possible to abort a leap second properly by resetting the STA_INS/STA_DEL
status bits.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Roman Zippel authored and torvalds committed May 1, 2008
1 parent 8383c42 commit 7dffa3c673fbcf835cd7be80bb4aec8ad3f51168
Showing with 95 additions and 45 deletions.
  1. +2 −0 include/linux/clocksource.h
  2. +1 −0 include/linux/timex.h
  3. +90 −43 kernel/time/ntp.c
  4. +2 −2 kernel/time/timekeeping.c
@@ -93,6 +93,8 @@ struct clocksource {
#endif
};
extern struct clocksource *clock; /* current clocksource */
/*
* Clock source flags bits::
*/
View
@@ -212,6 +212,7 @@ extern long time_esterror; /* estimated error */
extern long time_adjust; /* The amount of adjtime left */
extern void ntp_init(void);
extern void ntp_clear(void);
/**
View
@@ -16,6 +16,7 @@
#include <linux/hrtimer.h>
#include <linux/capability.h>
#include <linux/math64.h>
#include <linux/clocksource.h>
#include <asm/timex.h>
/*
@@ -26,6 +27,8 @@ 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)
@@ -120,64 +123,70 @@ void ntp_clear(void)
}
/*
* 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.
* 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.
*/
void second_overflow(void)
static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
{
s64 time_adj;
enum hrtimer_restart res = HRTIMER_NORESTART;
/* 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;
}
write_seqlock_irq(&xtime_lock);
/*
* 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. The microtime()
* routine or external clock driver will insure that reported time is
* always monotonic. The ugly divides should be replaced.
*/
switch (time_state) {
case TIME_OK:
if (time_status & STA_INS)
time_state = TIME_INS;
else if (time_status & STA_DEL)
time_state = TIME_DEL;
break;
case TIME_INS:
if (xtime.tv_sec % 86400 == 0) {
xtime.tv_sec--;
wall_to_monotonic.tv_sec++;
time_state = TIME_OOP;
printk(KERN_NOTICE "Clock: inserting leap second "
"23:59:60 UTC\n");
}
xtime.tv_sec--;
wall_to_monotonic.tv_sec++;
time_state = TIME_OOP;
printk(KERN_NOTICE "Clock: "
"inserting leap second 23:59:60 UTC\n");
leap_timer.expires = ktime_add_ns(leap_timer.expires,
NSEC_PER_SEC);
res = HRTIMER_RESTART;
break;
case TIME_DEL:
if ((xtime.tv_sec + 1) % 86400 == 0) {
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");
}
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;
break;
/* fall through */
case TIME_WAIT:
if (!(time_status & (STA_INS | STA_DEL)))
time_state = TIME_OK;
break;
}
update_vsyscall(&xtime, clock);
write_sequnlock_irq(&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;
}
/*
@@ -268,7 +277,7 @@ static inline void notify_cmos_timer(void) { }
int do_adjtimex(struct timex *txc)
{
struct timespec ts;
long save_adjust;
long save_adjust, sec;
int result;
/* In order to modify anything, you gotta be super-user! */
@@ -289,6 +298,10 @@ int do_adjtimex(struct timex *txc)
txc->tick > 1100000/USER_HZ)
return -EINVAL;
if (time_state != TIME_OK && txc->modes & ADJ_STATUS)
hrtimer_cancel(&leap_timer);
getnstimeofday(&ts);
write_seqlock_irq(&xtime_lock);
/* Save for later - semantics of adjtime is to return old value */
@@ -305,6 +318,34 @@ int do_adjtimex(struct timex *txc)
/* 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)
@@ -384,7 +425,6 @@ int do_adjtimex(struct timex *txc)
txc->stbcnt = 0;
write_sequnlock_irq(&xtime_lock);
getnstimeofday(&ts);
txc->time.tv_sec = ts.tv_sec;
txc->time.tv_usec = ts.tv_nsec;
if (!(time_status & STA_NANO))
@@ -402,3 +442,10 @@ static int __init ntp_tick_adj_setup(char *str)
}
__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;
}
@@ -53,7 +53,7 @@ void update_xtime_cache(u64 nsec)
timespec_add_ns(&xtime_cache, nsec);
}
static struct clocksource *clock; /* pointer to current clocksource */
struct clocksource *clock;
#ifdef CONFIG_GENERIC_TIME
@@ -246,7 +246,7 @@ void __init timekeeping_init(void)
write_seqlock_irqsave(&xtime_lock, flags);
ntp_clear();
ntp_init();
clock = clocksource_get_next();
clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);

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