Re: [PATCH] s390 (9/9): no timer interrupts in idle.

From: Martin Schwidefsky
Date: Thu Apr 22 2004 - 08:05:19 EST

> ok maybe I need to word it differently.
> What I'm proposing as alternative is using the one shot mode of the
> on most machines to do teh following:
> when the timer irq hits, you do the business you need to do. And then you
> check all existing timers and the scheduler when the next "virtual tick"
is where
> you're going to do real work. You then set the one-shot counter to that
> amount. This means that in add_timer/mod_timer you will need to check if
> just added timer is before the current one-shot runs out, and if so,
> it. Perhaps in the scheduler too.

You can't do that with the current timer code. A HZ timer interrupt is used
for several things: 1) increase jiffies_64, 2) update the xtime, 3) calculate
the load every 5 seconds, 4) check cpu time limits and send SIGXCPU,
5) do interval timer stuff, 6) run local timer queue and 7) add time slice to
current process. With your one-shot timer you won't do the correct updates
to the jiffies and the xtime.

blue skies,

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