[ntp:questions] drifting on crystal

prep at prep.synonet.com prep at prep.synonet.com
Fri Jan 21 18:54:11 UTC 2005


Ulrich Windl <Ulrich.Windl at RZ.Uni-Regensburg.DE> writes:

>> It is still possible for Linux to miss a clock interrupt, if some
>> other device switches off the interrupts for an extended period of
>> time.  But I believe such devices are slowly dying unmaintained in
>> the vast plains under /usr/src/linux/drivers/char/*.  In any case
>> it should not bite you if you do not have any such device in your
>> computer.

> It all depends: Usually just test your hardware in a typical
> use-case: if it doesn't loose interrupts the first day, it most
> likely won't the other day.

All the time tick interupt code has to do is increment a counter,
and return.

When the system get back to exit to the user or idle loop, it tests the
tick counter and if it is not zero, runs the `clock tick' code. Wash,
rinse...

This allows you to run with out ever masking out the clock interupt.

-- 
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+61 (08) 9257-1001                           Kalamunda.
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