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>

2 files changed, 92 insertions, 45 deletions

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index df9718bac8d0..5125ddd8196b 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 @@ 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;
+}
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 7e74d8092067..e91c29f961c9 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -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);