On Fri, May 26, 2006 at 05:19:30AM -0700, Boldoo wrote:
> Hi
>
> 1. Does any one could explain me purpose of
> interval_outstanding variable in TimerM component?
> When I look at Clock.fire event, then the HandleFire
> task is only posted if interval_outstanding is equal
> to zero. But I cannot understand how
> interval_outstanding become zero.
It's set zero when the timer event is handled by
HandleFire(). The code is
atomic {
int_out = interval_outstanding;
interval_outstanding = 0;
}
The purpose is, I think, to synchronize the actions
of the HandleFire task and the clock interrupts.
Only when one HandleFire task finishes is another
posted, hence avoiding task queue overflow or
race conditions on mTimerList. I am just guessing,
and the authors (Joe et al.) would have the ultimate
authority explaining this.
> 2. and why counter value is added to interval to
> calculate remained ticks (mTimerList[id].ticksleft) in
> command Timer.start? In my opinion to get the remained
> ticks simply substract counter value from the interval
> value, such as
> remained ticks=interval - counter value
This is also handled in HandleFire. The code reads
if (mState&(0x1L<<i)) {
mTimerList[i].ticksLeft -= int_out;
Cheers,
lin
--
Lin Gu
Department of Computer Science
University of Virginia
Tel: 434-825-3115
Web: http://www.cs.virginia.edu/~lg6e
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