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>
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index df9718b..5125ddd 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -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 @@
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)
@@ -120,6 +123,54 @@
}
/*
+ * 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_irq(&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");
+ leap_timer.expires = ktime_add_ns(leap_timer.expires,
+ 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_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
@@ -139,48 +190,6 @@
}
/*
- * 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");
- }
- 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");
- }
- break;
- case TIME_OOP:
- time_tai++;
- time_state = TIME_WAIT;
- break;
- case TIME_WAIT:
- if (!(time_status & (STA_INS | STA_DEL)))
- time_state = TIME_OK;
- }
-
- /*
* Compute the phase adjustment for the next second. The offset is
* reduced by a fixed factor times the time constant.
*/
@@ -268,7 +277,7 @@
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 @@
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 @@
/* 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 @@
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 @@
}
__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;
+}
