Commit-ID: c2cda2a5bda9f1369c9d1ab54a20571c13cf2743 Gitweb: https://git.kernel.org/tip/c2cda2a5bda9f1369c9d1ab54a20571c13cf2743 Author: Miroslav Lichvar <[email protected]> AuthorDate: Fri, 9 Mar 2018 10:42:47 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Sat, 10 Mar 2018 09:12:41 +0100
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 <[email protected]> Signed-off-by: John Stultz <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Prarit Bhargava <[email protected]> Cc: Richard Cochran <[email protected]> Cc: Stephen Boyd <[email protected]> Cc: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- kernel/time/timekeeping.c | 3 --- 1 file changed, 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; } /*
