From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Thu, 02 Nov 2006 08:54:51 +0100
From: Jan Kiszka <jan.kiszka@domain.hid>
MIME-Version: 1.0
Subject: Re: [Xenomai-help] Propagating interrupts
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To: Jeff Webb <jeff.webb@domain.hid>
Cc: Xenomai help <xenomai@xenomai.org>

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Jeff Webb wrote:
>=20
> I have read that propagating interrupts to Linux is a bad idea for RT
> applications.  I am trying to understand what happens when I install an=

> interrupt handler via the userspace POSIX skin like this:
>=20
>  pthread_intr_attach_np (&ctr_intr, irq_number, PTHREAD_IPROPAGATE);
>=20
> My RT thread waits on this interrupt using:
>=20
>  pthread_intr_wait_np(ctr_intr, NULL);
>=20
> Here is my understanding of what happens when I get an interrupt on thi=
s
> IRQ.  The Xenomai interrupt handler is executed, which wakes up my RT
> thread.  The interrupt remains masked until the Linux interrupt handler=

> is executed.  The linux interrupt handler processes the interrupt, and
> then re-enables the IRQ.  Now the RT thread can receive more interrupts=
=2E
>=20
> Is this basically correct?

Yes, the Linux domain can cause priority inversion /wrt the real-time
domain trying to handle the same IRQ line. That's true for any
deterministic/indeterministic IRQ handler combination, not only under
Xenomai.

Jan


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