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authorMiroslav Lichvar <mlichvar@redhat.com>2018-03-09 10:42:47 -0800
committerIngo Molnar <mingo@kernel.org>2018-03-10 09:12:41 +0100
commitc2cda2a5bda9f1369c9d1ab54a20571c13cf2743 (patch)
treec15708e16f272c90ec5a2632b4c9c47b11fcdf8f /kernel/time/timekeeping.c
parent27263e8dc0f6fe27540a843611ec14a000591c41 (diff)
downloadlinux-c2cda2a5bda9f1369c9d1ab54a20571c13cf2743.tar.bz2
timekeeping/ntp: Don't align NTP frequency adjustments to ticks
When the timekeeping multiplier is changed, the NTP error is updated to correct the clock for the delay between the tick and the update of the clock. This error is corrected in later updates and the clock appears as if the frequency was changed exactly on the tick. Remove this correction to keep the point where the frequency is effectively changed at the time of the update. This removes a major source of the NTP error. Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com> Signed-off-by: John Stultz <john.stultz@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Stephen Boyd <stephen.boyd@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1520620971-9567-2-git-send-email-john.stultz@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/time/timekeeping.c')
-rw-r--r--kernel/time/timekeeping.c3
1 files changed, 0 insertions, 3 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index cd03317e7b57..c1a0ac17336e 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1860,8 +1860,6 @@ static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
* xtime_nsec_2 = xtime_nsec_1 - offset
* Which simplfies to:
* xtime_nsec -= offset
- *
- * XXX - TODO: Doc ntp_error calculation.
*/
if ((mult_adj > 0) && (tk->tkr_mono.mult + mult_adj < mult_adj)) {
/* NTP adjustment caused clocksource mult overflow */
@@ -1872,7 +1870,6 @@ static __always_inline void timekeeping_apply_adjustment(struct timekeeper *tk,
tk->tkr_mono.mult += mult_adj;
tk->xtime_interval += interval;
tk->tkr_mono.xtime_nsec -= offset;
- tk->ntp_error -= (interval - offset) << tk->ntp_error_shift;
}
/*