| Re: [chrony-dev] Chrony stuck in an endless loop |
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It seems that the only place that the RGR_FindBestRobustRegression is used in
in rtc.c and manual.c
It seems that it is estimating the standard deviation of slope and getting
essentially zero for that, which gives a tiny value for incr.
Perhaps the lines setting incr could be changed to
if (sb > tol) {
incr = 3.0 * sb;
} else {
incr = 3.0 * tol;
}
Of course one should check that tol has a reasonable value then (eg not
negative, etc)
Do you boards have an onboard rtc at all?
On Mon, 12 Nov 2012, Hattink, Tjalling [FINT] wrote:
Hi,
Recently I've encountered a lockup of chrony on one of our embedded
boards running Linux. It was consuming all CPU resources and not acting
on any inputs anymore. I was able to attach a gdb debugger to the
process with symbols, so I could see the callstack and where it was
stuck.
The version I was using is 1.24. And it got stuck in the file regress.c,
line 570 to 578. The while loop there never exited. I also checked the
latest regress.c version in git, and I see the same loop at line 600 to
608, so I suspect the latest chrony is still affected by this issue.
The reason for getting stuck was that the blo and bhi variables never
changed. They both contained the same value -1.9333333333334166e-06. The
incr variable contained the value 9.061309612524684e-25. The reason why
blo and bhi didn't change was that incr is so small that it is
insignificant when added/substracted to blo and bhi.
After I changed the incr value to a much bigger number 1.0e-15 using gdb
the loop exited and chrony was working properly again.
The solution is to make sure incr contains a significant value before
going into the loop 570-578. Although I can't think of a good trick yet
to achieve this.
What are your thoughts about this? How should we fix this?
With best regards,
Tjalling Hattink
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