[Xenomai] Can we have nested interrupt handling in Xenomai?

[Xenomai] Can we have nested interrupt handling in Xenomai?

[ali hagigat]

Can we have nested interrupt handling in Xenomai? Suppose we are in
the middle of an interrupt handler and a new interrupt comes in, CPU
will start executing the handler of the new interrupt completely? or
that interrupt is logged only for that domain to be serviced later?

As far as I understood, when an interrupt comes, that interrupt is
disabled and the domain pipeline is stalled and then the interrupt
handler is called.
When the interrupt handler returns, the domain pipeline is unstalled.
Is that correct?

Re: [Xenomai] Can we have nested interrupt handling in Xenomai?

[Gilles Chanteperdrix]

On 08/22/2012 06:28 AM, ali hagigat wrote:
> Can we have nested interrupt handling in Xenomai? Suppose we are in
> the middle of an interrupt handler and a new interrupt comes in, CPU
> will start executing the handler of the new interrupt completely? or
> that interrupt is logged only for that domain to be serviced later?

No, we do not support nested interrupt. You should note that the Linux
kernel has stopped re-enabling hardware interrupts in the middle of the
interrupt handlers for some time now: if an interrupt handler takes a
long time to execute, then there is a bug in the interrupt handler. The
interrupt handler has to be fixed, re-enabling interrupts is a bad
workaround.

> 
> As far as I understood, when an interrupt comes, that interrupt is
> disabled and the domain pipeline is stalled and then the interrupt
> handler is called.
> When the interrupt handler returns, the domain pipeline is unstalled.
> Is that correct?

Not quite, it depends on which domain is current and which domain the
interrupt is for.

-- 
					    Gilles.

Re: [Xenomai] Can we have nested interrupt handling in Xenomai?

[ali hagigat]

Dear Gilles,

Would you please explain when a pipeline stage is stalled/unstalled? I
wonder if you can explain it in more details.
Regards

>> As far as I understood, when an interrupt comes, that interrupt is
>> disabled and the domain pipeline is stalled and then the interrupt
>> handler is called.
>> When the interrupt handler returns, the domain pipeline is unstalled.
>> Is that correct?
>
> Not quite, it depends on which domain is current and which domain the
> interrupt is for.
>
> --
>                                             Gilles.

Re: [Xenomai] Can we have nested interrupt handling in Xenomai?

[Gilles Chanteperdrix]

On 08/22/2012 11:48 AM, ali hagigat wrote:

> Dear Gilles,
> 
> Would you please explain when a pipeline stage is stalled/unstalled? I
> wonder if you can explain it in more details.
> Regards


See __ipipe_dispatch_irq there:
http://git.denx.de/?p=ipipe.git;a=blob;f=kernel/ipipe/core.c;h=182b61c5c294044dde712884a9d3123e393c54a9;hb=refs/heads/core-3.4

Around line 1166.
-- 
                                                                Gilles.