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sys_linux: don't drop PHC samples with zero delay

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When processing data from the PTP_SYS_OFFSET ioctl, the sample is
dropped when an interval between two consecutive readings of the system
clock is negative or zero, assuming the clock has been stepped between
the two readings.

With a real PHC the interval is normally expected to be at least a
microsecond, but with a virtual PHC and a low-resolution system clock
it's possible to get two readings with the same system time. Modify the
check to drop only samples with a negative delay.
This commit is contained in:
Miroslav Lichvar 2017-04-19 12:20:14 +02:00
parent c103bebd9f
commit abb09418b1
1 changed files with 3 additions and 1 deletions
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4
sys_linux.c
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@ -705,9 +705,11 @@ get_phc_sample(int phc_fd, double precision, struct timespec *phc_ts,
phc_tss[i] = ts2;
delays[i] = UTI_DiffTimespecsToDouble(&ts3, &ts1);
if (delays[i] <= 0.0)
if (delays[i] < 0.0) {
/* Step in the middle of a PHC reading? */
DEBUG_LOG("Bad PTP_SYS_OFFSET sample delay=%e", delays[i]);
return 0;
}
if (!i || delays[i] < min_delay)
min_delay = delays[i];