[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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