This is a note to let you know that I've just added the patch titled
time: Avoid making adjustments if we haven't accumulated anything
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
time-avoid-making-adjustments-if-we-haven-t-accumulated-anything.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From [email protected] Thu Sep 27 13:32:31 2012
From: John Stultz <[email protected]>
Date: Tue, 11 Sep 2012 15:04:18 -0400
Subject: time: Avoid making adjustments if we haven't accumulated anything
To: [email protected]
Cc: John Stultz <[email protected]>, Prarit Bhargava <[email protected]>,
Ingo Molnar <[email protected]>, Thomas Gleixner <[email protected]>
Message-ID: <[email protected]>
From: John Stultz <[email protected]>
commit bf2ac312195155511a0f79325515cbb61929898a upstream.
If update_wall_time() is called and the current offset isn't large
enough to accumulate, avoid re-calling timekeeping_adjust which may
change the clock freq and can cause 1ns inconsistencies with
CLOCK_REALTIME_COARSE/CLOCK_MONOTONIC_COARSE.
Signed-off-by: John Stultz <[email protected]>
Cc: Prarit Bhargava <[email protected]>
Cc: Ingo Molnar <[email protected]>
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: John Stultz <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/time/timekeeping.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1057,9 +1057,12 @@ static void update_wall_time(void)
#else
offset = (clock->read(clock) - clock->cycle_last) & clock->mask;
#endif
+ /* Check if there's really nothing to do */
+ if (offset < timekeeper.cycle_interval)
+ goto out;
+
timekeeper.xtime_nsec = (s64)timekeeper.xtime.tv_nsec <<
timekeeper.shift;
-
/*
* With NO_HZ we may have to accumulate many cycle_intervals
* (think "ticks") worth of time at once. To do this efficiently,
Patches currently in stable-queue which might be from [email protected] are
queue-3.4/time-avoid-making-adjustments-if-we-haven-t-accumulated-anything.patch
queue-3.4/time-move-ktime_t-overflow-checking-into-timespec_valid_strict.patch
queue-3.4/time-improve-sanity-checking-of-timekeeping-inputs.patch
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