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rtc: check for backward RTC steps

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When accumulating a new sample, check if the new RTC time is newer the
last sample time. If it is not, discard all previous samples, assuming
something has stepped the RTC, or it's a broken RTC/driver.
This commit is contained in:
Miroslav Lichvar 2017-01-12 13:43:41 +01:00
parent ac0b28cce6
commit e28dfada8c
1 changed files with 5 additions and 0 deletions
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5
rtc_linux.c
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@ -187,6 +187,11 @@ accumulate_sample(time_t rtc, struct timespec *sys)
discard_samples(NEW_FIRST_WHEN_FULL); discard_samples(NEW_FIRST_WHEN_FULL);
} }
/* Discard all samples if the RTC was stepped back (not our trim) */
if (n_samples > 0 && rtc_sec[n_samples - 1] - rtc >= rtc_trim[n_samples - 1]) {
DEBUG_LOG(LOGF_RtcLinux, "RTC samples discarded");
n_samples = 0;
}
/* Always use most recent sample as reference */ /* Always use most recent sample as reference */
/* use sample only if n_sample is not negative*/ /* use sample only if n_sample is not negative*/