From mboxrd@z Thu Jan  1 00:00:00 1970
Subject: Re: [Adeos-main] End of interrupt scheduling
From: Michael Neuhauser <mike@domain.hid>
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Date: Fri, 10 Dec 2004 14:52:29 +0100
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On Fri, 2004-12-10 at 14:22, Andre Tousch wrote:
> Hi,
> thanks for your reply.

I hope you don't mind when we continue this on the mailing list, other
people might also be interested in it or have something to say on these
matters.

> [...]
> 
> >Maybe I'm overlooking something, but why don't you unstall the pipeline
> >in your interrupt handler? 
>
> Adeos stalls the domain before calling its interrupt handler, and 
> unstalls the domain after the handler returns.
> This prevents reentrance on the interrupt handler.
> If I unstall the pipeline, I make the handler reentrant, while Adeos 
> assumes it is not.

As far as I know, Adeos does not make such an assumption. Take for
instance the Linux timer interrupt. It has SA_INTERRUPT set, therefore
arch/arm/kernel/irq.c:__do_irq() enables interrupts with
local_irq_enable() before calling the real handler. With Adeos this
translates to a pipe unstall inside an irq-handler. This allows *other*
interrupts to occur while the timer irq handler is running. Another
timer interrupt can't happen while the old one is handled: the timer-irq
will be unmasked *after* the handler has finished (see 
arch/arm/kernel/irq.c:do_IRQ()).

Mike
-- 
Dr. Michael Neuhauser                phone: +43 1 789 08 49 - 30
Firmix Software GmbH                   fax: +43 1 789 08 49 - 55
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