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Commit 7dffa3c6 authored by Roman Zippel's avatar Roman Zippel Committed by Linus Torvalds
Browse files

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: default avatarRoman Zippel <zippel@linux-m68k.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8383c423

include/linux/clocksource.h

+2 −0
Original line number Diff line number Diff line
@@ -93,6 +93,8 @@ struct clocksource { 
#endif

};



extern struct clocksource *clock;	/* current clocksource */



/*

 * Clock source flags bits::

 */

include/linux/timex.h

+1 −0
Original line number Diff line number Diff line
@@ -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);



/**

kernel/time/ntp.c

+90 −43
Original line number Diff line number Diff line
@@ -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");

		}

		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");

		}

		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;

}

kernel/time/timekeeping.c

+2 −2
Original line number Diff line number Diff line
@@ -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);