mirror of
https://github.com/FEX-Emu/linux.git
synced 2024-12-15 05:11:32 +00:00
time: Move xtime_nsec adjustment underflow handling timekeeping_adjust
When we make adjustments speeding up the clock, its possible for xtime_nsec to underflow. We already handle this properly, but we do so from update_wall_time() instead of the more logical timekeeping_adjust(), where the possible underflow actually occurs. Thus, move the correction logic to the timekeeping_adjust, which is the function that causes the issue. Making update_wall_time() more readable. Signed-off-by: John Stultz <johnstul@us.ibm.com> Reviewed-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Prarit Bhargava <prarit@redhat.com> Link: http://lkml.kernel.org/r/1342156917-25092-8-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
parent
f2a5a0854e
commit
2a8c0883c3
@ -980,6 +980,27 @@ static void timekeeping_adjust(s64 offset)
|
||||
timekeeper.xtime_nsec -= offset;
|
||||
timekeeper.ntp_error -= (interval - offset) <<
|
||||
timekeeper.ntp_error_shift;
|
||||
|
||||
/*
|
||||
* It may be possible that when we entered this function, xtime_nsec
|
||||
* was very small. Further, if we're slightly speeding the clocksource
|
||||
* in the code above, its possible the required corrective factor to
|
||||
* xtime_nsec could cause it to underflow.
|
||||
*
|
||||
* Now, since we already accumulated the second, cannot simply roll
|
||||
* the accumulated second back, since the NTP subsystem has been
|
||||
* notified via second_overflow. So instead we push xtime_nsec forward
|
||||
* by the amount we underflowed, and add that amount into the error.
|
||||
*
|
||||
* We'll correct this error next time through this function, when
|
||||
* xtime_nsec is not as small.
|
||||
*/
|
||||
if (unlikely((s64)timekeeper.xtime_nsec < 0)) {
|
||||
s64 neg = -(s64)timekeeper.xtime_nsec;
|
||||
timekeeper.xtime_nsec = 0;
|
||||
timekeeper.ntp_error += neg << timekeeper.ntp_error_shift;
|
||||
}
|
||||
|
||||
}
|
||||
|
||||
|
||||
@ -1105,27 +1126,6 @@ static void update_wall_time(void)
|
||||
/* correct the clock when NTP error is too big */
|
||||
timekeeping_adjust(offset);
|
||||
|
||||
/*
|
||||
* Since in the loop above, we accumulate any amount of time
|
||||
* in xtime_nsec over a second into xtime.tv_sec, its possible for
|
||||
* xtime_nsec to be fairly small after the loop. Further, if we're
|
||||
* slightly speeding the clocksource up in timekeeping_adjust(),
|
||||
* its possible the required corrective factor to xtime_nsec could
|
||||
* cause it to underflow.
|
||||
*
|
||||
* Now, we cannot simply roll the accumulated second back, since
|
||||
* the NTP subsystem has been notified via second_overflow. So
|
||||
* instead we push xtime_nsec forward by the amount we underflowed,
|
||||
* and add that amount into the error.
|
||||
*
|
||||
* We'll correct this error next time through this function, when
|
||||
* xtime_nsec is not as small.
|
||||
*/
|
||||
if (unlikely((s64)timekeeper.xtime_nsec < 0)) {
|
||||
s64 neg = -(s64)timekeeper.xtime_nsec;
|
||||
timekeeper.xtime_nsec = 0;
|
||||
timekeeper.ntp_error += neg << timekeeper.ntp_error_shift;
|
||||
}
|
||||
|
||||
/*
|
||||
* Store only full nanoseconds into xtime_nsec after rounding
|
||||
|
Loading…
Reference in New Issue
Block a user