[LinuxPPS] bouncing primary signals in ntpq -p output, signal loss in pps0 when pps1 is attached.

[Alexander Gordeev]

В Sat, 12 Feb 2011 18:24:19 +0100
Felix Joussein <felix.joussein at gmx.at> пишет:

> Hello List,
> 
> When I attach 2 pps sources to my machine, and run ppstest /dev/pps0 and 
> simultaneously on /dev/pps1, the following happens: (I used gnu screen 
> to monitor the output simultaneously)
> 
> First, I plug the pulse generator to pps0 - everything is perfect, the 
> pulse is retrieved regularly, no loss.
> After a minute or so, I have the insurance, pps0 works fine, so I attach 
> a second pulse generator to pps1: suddenly pps0 looses some pulses, 
> and/or come very irregular.
> Both pulse signals come from an HP atom clock.
> pps1 also retrieves some pules, but far less then pps0 and both sources 
> are irregular and have lot's of loss. As soon as I disconnect the pps1 
> pulse, pps0 returns to normal.
> 
> When I increase the pulse length, to half second up/down, ppstest works 
> great.

How many processors/cores do you have? What interface do you use to
connect pps sources?
This can be a bug in PPS subsystem/clients or maybe a race between two
interrupt handlers. If you have only 1 core then two interrupts cannot
be served at the same time. But this should lead to inaccuracy, not the
loss of signals. Please provide ppstest logs for both sources. 

> The result in ntpd is as follows:
> 
> If I enable 2 pps sources in ntpd.conf with flag3 1.:
> pps pps1: another kernel consumer is already bound
> 
> Does that mean, that I can only use kernel consumer for one attached pps 
> source?

Exactly :)

-- 
  Alexander
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