Re: [Rtlinuxgpl] Interrupt Prioritization

On Sat, 31 Dec 2005, Der Herr Hofrat wrote:

>>
>> I forget: Is this actually implemented in RTLinux/Free or RTLinux GPL
>> Free?
>>
> no - the interrupt interception does not prioritize interrupts - I played
> with it as it is fairly simple to implement but it really has close to 0
> advantage as the you simply can run the hig priority ISR with disabled
> interrupts, as it will preempt any other running ISR this de-facto has the
> same effect as if you would prioritize interrupts. The overhead of
> introducing interrupt priorities does not pay off if you keep your ISRs
> short and shedule a "bottom-half" as a regular RT-thread.
>
> In what situation would you need it ?

Well, I am running a periodic task that I want to always run when it is 
supposed to, and to never run late or be preempted in anyway -- but I also 
have a realtime sound driver that feeds sounds to a soundcard to play them 
(by writing to DMA buffers).  Anyway, I want the periodic task to always 
preempt the sound driver ISR.  I suppose it is simple enough -- just run 
the periodic task with interrupts disabled while making sure hard realtime 
interrupts are always enabled when the sound driver ISR is running, right?

I see what you are saying about interrupt prioritization has 0 advantage 
though -- I suppose what I want can be accomplished by the above, right?

-Calin


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