Re: Re: [Rtlinuxgpl] Interrupt Prioritization

On Tue, 3 Jan 2006, Victor Yodaiken wrote:

> On Tue, Jan 03, 2006 at 05:48:35PM -0500, Calin A. Culianu wrote:
>> OK.  I get it.  One last question.  "If B is running and C becomes
>> runnable... ".
>>
>> That happens if the timer interrupt fires, right?
>>
>> So that means that the timer interrupt is always on when rt tasks are
>> running?
>>
>> Is that always ok?  I mean doesn't that sort of introduce lots of jitter?
>
> Not on modern machines and the alternative is to let a scheduled high
> priority task wait on a lower priority task.

Ok, I see.  I suppose intercepting the timer interrupt and making a 
decision of what to schedule probably only costs you a few hundred nanos 
anyway.

Hey, thanks so much for explaining this to me.  This sure beats my 
spending a dozen hours poring over the RTLinux sources, and it really 
helps me to understand the design and what can or cannot happen.

Thanks!
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