patches/timekeeping-store-cycle-last-in-timekeeper.patch

Subject: timekeeping: Store cycle_last value in timekeeper struct as well
From: Thomas Gleixner <tglx@linutronix.de>
Date: Fri, 15 Feb 2013 17:15:49 +0100

For implementing a shadow timekeeper and a split calculation/update
region we need to store the cycle_last value in the timekeeper and
update the value in the clocksource struct only in the update region.

Add the extra storage to the timekeeper.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/timekeeper_internal.h |    2 ++
 kernel/time/timekeeping.c           |    4 ++--
 2 files changed, 4 insertions(+), 2 deletions(-)

--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -20,6 +20,8 @@ struct timekeeper {
 	u32			shift;
 	/* Number of clock cycles in one NTP interval. */
 	cycle_t			cycle_interval;
+	/* Last cycle value (also stored in clock->cycle_last) */
+	cycle_t			cycle_last;
 	/* Number of clock shifted nano seconds in one NTP interval. */
 	u64			xtime_interval;
 	/* shifted nano seconds left over when rounding cycle_interval */
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -96,7 +96,7 @@ static void tk_setup_internals(struct ti
 
 	old_clock = tk->clock;
 	tk->clock = clock;
-	clock->cycle_last = clock->read(clock);
+	tk->cycle_last = clock->cycle_last = clock->read(clock);
 
 	/* Do the ns -> cycle conversion first, using original mult */
 	tmp = NTP_INTERVAL_LENGTH;
@@ -247,7 +247,7 @@ static void timekeeping_forward_now(stru
 	clock = tk->clock;
 	cycle_now = clock->read(clock);
 	cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
-	clock->cycle_last = cycle_now;
+	tk->cycle_last = clock->cycle_last = cycle_now;
 
 	tk->xtime_nsec += cycle_delta * tk->mult;