Re: [Xenomai-help] Handling irq

[Jan Kiszka <jan.kiszka@domain.hid>]

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Gilles Chanteperdrix wrote:
> On Fri, Mar 21, 2008 at 11:50 AM, Bosko Radivojevic
> <bosko.radivojevic@domain.hid> wrote:
>> I have much better results using rtdm_lock_get_irqsave and
>>  rtdm_lock_put_irqrestore. I hope this is the "appropriate method" of
>>  doing it :)
>>
>>  Thanks!
> 
> Shutting interrupts off for long periods of time is not a good idea:
> - it does not scale well, since it does not work for more than one task;
> - it kills the precision of timers by delaying the timer interrupt.
> And I am sure we can find many more drawbacks.

- it only reduces the probability of your problem, it doe not
   eliminate it completely

You can still be interrupted right after task wakeup, before 
rtdm_lock_get_irqsave. And there is still the possibility to be delayed 
by interrupts BEFORE your task is even triggered.

If you cannot live with this conceptual jitter (which you'll find on any 
RTOS with more than one job running), you have to do ahead-of-time 
scheduling with busy waiting until the actual release date. That will 
mean disabling IRQs for a really long time + burning a lot of CPU power. 
Kind of last resort, not generally recommended.

Jan


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