> Robert Kavaler ([EMAIL PROTECTED]) wrote:
> > and realtime tasks?
> >
> > If the interrupt does preempt, is there some easy way to implement
> > queueing where the interrupt "task" can be scheduled with normal task
> > priorities (i.e. create a normal task and have the interrupt wake task)?
>
> In the real-time task, use the following loop:
>
> while (1) {
> pthread_suspend_np(pthread_self());
> // handle the interrupt
> }
>
> Then install a RT interrupt handler using rtl_request_irq (there is a manual
> page in the distribution).
> In the interrupt handler call pthread_wakeup_np(thread) to
> wake the real-time thread up.
>
I noticed that in revisions 2.0 and 3.0 that the wakeup directly sets the
runnable flag of a task and therefore in the code above, if an interrupt
occurs before the suspend, the ISR will wakeup a non-suspended task, and then
the task will be suspended forever. This problem is usually solved by testing
if the interrupt occurs with interrupts OFF before the suspend and then
suspending with interrupts off. The scheduler would then turn interrupts
on and run until the task is woken up at which time the task would re-enable
interrupts and continue. Is this what one should do?
I noticed also that in revision 2.2 that the wakeup does not set the
runnable flag, instead it sets a wakeup flag and clear the suspended flag.
In theory this would get around the problem above assuming that suspend
would set the suspended flag (and not clear the wakeup flag),
and the scheduler would give priority to the wakeup. In this way,
if an interrupt occurs during execution of the task, then suspend would
just essentially be ignored. Unfortunately, when I look at suspend it clears
the wakeup flag and doesn't set the suspended flag. So I'm confused.
How does the task actually get suspended? What is the intent
moving forward, should I protect the suspend by disabling interrupts, or
will this be handled by the scheduler?
(BTW, the 2.1 code appears to half way between 2.0 and 2.2, but functions
more like 2.0 since it sets the runnable flag directly.
Robert Kavaler
[EMAIL PROTECTED]
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