Ah, yes, that is it in a nut shell. If you try to put the
high res timers in a "special" list and not in the same list
as the low res stuff, you have ordering issues. It becomes
real easy to have the timers expire in the incorrect order.
As to interrupt source and time, the biggest issue is that
we don't really have timers that interrupt in "nice" units
of time. The PIT, for example, has a tick time (i.e. each
count) of 0.838095239 micro seconds. So how are we to
figure time from such a tick if we want to use an integer
value for HZ.
What my patch suggests is that we use the higher resolution
TSC or pm timer (or what ever is available) and just use the
PIT to remind us to look at the clock, AND that we keep time
in units of that clock. In some ways we already do this,
but we are not consistent. For example we advance the time
by less than 1 ms each tick, but we still assume that a tick
is 1 ms when we set up timers. This leads to standards
failures such as that illustrated by:
time sleep 60
which on a 2.5 system will sleep for less than 60 seconds
because of this.
-- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/