[ntp:questions] Linux kernel bug in 3.12, low_latency on serial ports is broken

Brian Inglis Brian.Inglis at SystematicSw.ab.ca
Mon Feb 24 05:46:45 UTC 2014


On 2014-02-20 01:31, Hal Murray wrote:
> Just a heads-up in case you hit this, or want to avoid it.
>
> The symptom is BUG: scheduling while atomic
>    https://bugzilla.redhat.com/show_bug.cgi?id=1065087
>
> The discussion at
>    https://lkml.org/lkml/2014/2/18/77
> confirms that it's the low-latency path that is buggy.
>
> My setup works fine under low load, but hits the BUG when I do something like
> compile the ntp package.
>
> 3.11 works fine.  (for me)  There was major work in the serial area for 3.12
>
> I'll send an update when/if it gets fixed.

I noticed the developer was asking for performance criteria.
How about suggesting no degradation in kernel PPS performance after change?
That should be measurable within the kernel and externally with ntpd.

-- 
Take care. Thanks, Brian Inglis


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