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time: apply NTP frequency/tick changes immediately 

Since the GENERIC_TIME changes landed, the adjtimex behavior changed
for struct timex.tick and .freq changed. When the tick or freq value
is set, we adjust the tick_length_base in ntp_update_frequency().
However, this new value doesn't get applied to tick_length until the
next second (via second_overflow).

This means some applications that do quick time tweaking do not see the
requested change made as quickly as expected.

I've run a few tests with this change, and ntpd still functions fine.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
john stultz 2009-02-18 16:02:22 -08:00 committed by Ingo Molnar
parent ba95fd47d1
commit fdcedf7b75
1 changed files with 7 additions and 0 deletions
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7
kernel/time/ntp.c
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@ -51,6 +51,7 @@ static long ntp_tick_adj;
static void ntp_update_frequency(void)
{
u64 old_tick_length_base = tick_length_base;
u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
<< NTP_SCALE_SHIFT;
second_length += (s64)ntp_tick_adj << NTP_SCALE_SHIFT;
@ -60,6 +61,12 @@ static void ntp_update_frequency(void)
tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
tick_length_base = div_u64(tick_length_base, NTP_INTERVAL_FREQ);
/*
* Don't wait for the next second_overflow, apply
* the change to the tick length immediately
*/
tick_length += tick_length_base - old_tick_length_base;
}
static void ntp_update_offset(long offset)