ntp: handle leap second via timer
Roman Zippel [Thu, 1 May 2008 11:34:41 +0000 (04:34 -0700)]
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>

include/linux/clocksource.h
include/linux/timex.h
kernel/time/ntp.c
kernel/time/timekeeping.c

index 3509447..55e434f 100644 (file)
@@ -93,6 +93,8 @@ struct clocksource {
 #endif
 };
 
+extern struct clocksource *clock;      /* current clocksource */
+
 /*
  * Clock source flags bits::
  */
index da431f8..fc6035d 100644 (file)
@@ -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);
 
 /**
index df9718b..5125ddd 100644 (file)
@@ -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;
+}
index 7e74d80..e91c29f 100644 (file)
@@ -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);