ntp: Add ntp_lock to replace xtime_locking

Use a ntp_lock spin lock to replace xtime_lock locking in ntp.c

CC: Thomas Gleixner <tglx@linutronix.de>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index f131ba6..17fb1b9 100644 (file)
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -22,6 +22,9 @@
  * NTP timekeeping variables:
  */
 
+DEFINE_SPINLOCK(ntp_lock);
+
+
 /* USER_HZ period (usecs): */
 unsigned long                  tick_usec = TICK_USEC;
 
@@ -133,7 +136,7 @@ static inline void pps_reset_freq_interval(void)
 /**
  * pps_clear - Clears the PPS state variables
  *
- * Must be called while holding a write on the xtime_lock
+ * Must be called while holding a write on the ntp_lock
  */
 static inline void pps_clear(void)
 {
@@ -149,7 +152,7 @@ static inline void pps_clear(void)
  * the last PPS signal. When it reaches 0, indicate that PPS signal is
  * missing.
  *
- * Must be called while holding a write on the xtime_lock
+ * Must be called while holding a write on the ntp_lock
  */
 static inline void pps_dec_valid(void)
 {
@@ -341,11 +344,13 @@ static void ntp_update_offset(long offset)
 
 /**
  * ntp_clear - Clears the NTP state variables
- *
- * Must be called while holding a write on the xtime_lock
  */
 void ntp_clear(void)
 {
+       unsigned long flags;
+
+       spin_lock_irqsave(&ntp_lock, flags);
+
        time_adjust     = 0;            /* stop active adjtime() */
        time_status     |= STA_UNSYNC;
        time_maxerror   = NTP_PHASE_LIMIT;
@@ -358,12 +363,20 @@ void ntp_clear(void)
 
        /* Clear PPS state variables */
        pps_clear();
+       spin_unlock_irqrestore(&ntp_lock, flags);
+
 }
 
 
 u64 ntp_tick_length(void)
 {
-       return tick_length;
+       unsigned long flags;
+       s64 ret;
+
+       spin_lock_irqsave(&ntp_lock, flags);
+       ret = tick_length;
+       spin_unlock_irqrestore(&ntp_lock, flags);
+       return ret;
 }
 
 
@@ -375,14 +388,15 @@ u64 ntp_tick_length(void)
 static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
 {
        enum hrtimer_restart res = HRTIMER_NORESTART;
+       unsigned long flags;
+       int leap = 0;
 
-       write_seqlock(&xtime_lock);
-
+       spin_lock_irqsave(&ntp_lock, flags);
        switch (time_state) {
        case TIME_OK:
                break;
        case TIME_INS:
-               timekeeping_leap_insert(-1);
+               leap = -1;
                time_state = TIME_OOP;
                printk(KERN_NOTICE
                        "Clock: inserting leap second 23:59:60 UTC\n");
@@ -390,7 +404,7 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
                res = HRTIMER_RESTART;
                break;
        case TIME_DEL:
-               timekeeping_leap_insert(1);
+               leap = 1;
                time_tai--;
                time_state = TIME_WAIT;
                printk(KERN_NOTICE
@@ -405,8 +419,14 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
                        time_state = TIME_OK;
                break;
        }
+       spin_unlock_irqrestore(&ntp_lock, flags);
 
-       write_sequnlock(&xtime_lock);
+       /*
+        * We have to call this outside of the ntp_lock to keep
+        * the proper locking hierarchy
+        */
+       if (leap)
+               timekeeping_leap_insert(leap);
 
        return res;
 }
@@ -422,6 +442,9 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
 void second_overflow(void)
 {
        s64 delta;
+       unsigned long flags;
+
+       spin_lock_irqsave(&ntp_lock, flags);
 
        /* Bump the maxerror field */
        time_maxerror += MAXFREQ / NSEC_PER_USEC;
@@ -441,23 +464,25 @@ void second_overflow(void)
        pps_dec_valid();
 
        if (!time_adjust)
-               return;
+               goto out;
 
        if (time_adjust > MAX_TICKADJ) {
                time_adjust -= MAX_TICKADJ;
                tick_length += MAX_TICKADJ_SCALED;
-               return;
+               goto out;
        }
 
        if (time_adjust < -MAX_TICKADJ) {
                time_adjust += MAX_TICKADJ;
                tick_length -= MAX_TICKADJ_SCALED;
-               return;
+               goto out;
        }
 
        tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
                                                         << NTP_SCALE_SHIFT;
        time_adjust = 0;
+out:
+       spin_unlock_irqrestore(&ntp_lock, flags);
 }
 
 #ifdef CONFIG_GENERIC_CMOS_UPDATE
@@ -681,7 +706,7 @@ int do_adjtimex(struct timex *txc)
 
        getnstimeofday(&ts);
 
-       write_seqlock_irq(&xtime_lock);
+       spin_lock_irq(&ntp_lock);
 
        if (txc->modes & ADJ_ADJTIME) {
                long save_adjust = time_adjust;
@@ -723,7 +748,7 @@ int do_adjtimex(struct timex *txc)
        /* fill PPS status fields */
        pps_fill_timex(txc);
 
-       write_sequnlock_irq(&xtime_lock);
+       spin_unlock_irq(&ntp_lock);
 
        txc->time.tv_sec = ts.tv_sec;
        txc->time.tv_usec = ts.tv_nsec;
@@ -921,7 +946,7 @@ void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
 
        pts_norm = pps_normalize_ts(*phase_ts);
 
-       write_seqlock_irqsave(&xtime_lock, flags);
+       spin_lock_irqsave(&ntp_lock, flags);
 
        /* clear the error bits, they will be set again if needed */
        time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
@@ -934,7 +959,7 @@ void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
         * just start the frequency interval */
        if (unlikely(pps_fbase.tv_sec == 0)) {
                pps_fbase = *raw_ts;
-               write_sequnlock_irqrestore(&xtime_lock, flags);
+               spin_unlock_irqrestore(&ntp_lock, flags);
                return;
        }
 
@@ -949,7 +974,7 @@ void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
                time_status |= STA_PPSJITTER;
                /* restart the frequency calibration interval */
                pps_fbase = *raw_ts;
-               write_sequnlock_irqrestore(&xtime_lock, flags);
+               spin_unlock_irqrestore(&ntp_lock, flags);
                pr_err("hardpps: PPSJITTER: bad pulse\n");
                return;
        }
@@ -966,7 +991,7 @@ void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
 
        hardpps_update_phase(pts_norm.nsec);
 
-       write_sequnlock_irqrestore(&xtime_lock, flags);
+       spin_unlock_irqrestore(&ntp_lock, flags);
 }
 EXPORT_SYMBOL(hardpps);