ntp: Correct TAI offset during leap second

This is a backport of dd48d708

When repeating a UTC time value during a leap second (when the UTC
time should be 23:59:60), the TAI timescale should not stop. The kernel
NTP code increments the TAI offset one second too late. This patch fixes
the issue by incrementing the offset during the leap second itself.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

kernel/time/ntp.c

@@ -208,6 +208,7 @@ int second_overflow(unsigned long secs)
 		if (secs % 86400 == 0) {
 			leap = -1;
 			time_state = TIME_OOP;
+			time_tai++;
 			printk(KERN_NOTICE
 				"Clock: inserting leap second 23:59:60 UTC\n");
 		}
@@ -222,7 +223,6 @@ int second_overflow(unsigned long secs)
 		}
 		break;
 	case TIME_OOP:
-		time_tai++;
 		time_state = TIME_WAIT;
 		break;