Re: [chrony-users] Fatal error : adjtimex() failed

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On Tue, Aug 21, 2012 at 06:05:46PM +0100, Tomalak Geret'kal wrote:
> I don't experience this issue at all when "noselect" is used on the
> NMEA/"GPS" source. That is, when I can launch chronyd past my
> adjtimex()/shmget() issues, the PPS has so far lasted up to 16 hours
> (longer tests pending) - far longer than it managed without the
> "noselect".
> Perhaps the PPS is simply not polled any more in such a case?

Were the refclock and tracking logging enabled when that happened?

> I'm not really worried about this case any more - "noselect" on the
> GPS source is doing its job as far as I can tell and my PPS/GPS
> offsets remain sane. Again, longer tests pending.
> It's really just the adjtimex()/shmget() oddity I'm confused about
> now. It really does seem to occur largely randomly and then vanish
> when I replace the binary with a new build which differs only by
> more verbose syslog output; to me, this screams UB in my build, but
> yikes. My investigation continues...!

That sounds like a race condition. Does it work under strace?
Does flushing the kernel cache trigger it again?

echo 3 > /proc/sys/vm/drop_caches

Miroslav Lichvar

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