On Fri, 31 Aug 2001 [EMAIL PROTECTED] wrote:
>
> > Hmm, does -current even need clkintr_pending anymore? What is its purpose?
>
> There is a problem if i8254_get_timecount locks clock_lock right
> before a rollover but reads the timer right afterwards. In that case,
> a too low value can be returned (resulting in 1/Hz too small time
> value) although the result will still be monotonous.
hmm monotonus? That explains the sudden bursts of sleepiness I
occasionally get when seated in front of the terminal!
(monatomicly increasing maybe?)
Not meant to be a slight on your english, which is excellent,
but just too funny to pass up.
>
> For RELENG_4, which uses Xintr0, this problem is reduced by adding the
> clkintr_pending variable (cf. revision 1.134 of clock.c and revision
> 1.38 of apic_vector.s)
>
> Looking more at the code, I now see that clkintr_pending is never set
> in -current due to Xintr0 not being used (Xfastintr0 is now used).
> Using a fast interrupt for the clock interrupt gives some of the same
> reduction of the race window size as the use of clkintr_pending.
>
> - Tor Egge
>
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