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Date:      Wed, 7 Mar 2001 02:25:39 +1100 (EST)
From:      Bruce Evans <bde@zeta.org.au>
To:        Dag-Erling Smorgrav <des@ofug.org>
Cc:        "Peter S. Housel" <housel@acm.org>, John Baldwin <jhb@FreeBSD.org>, cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org
Subject:   Re: cvs commit: src/sys/i386/isa apic_vector.s icu_vector.s
Message-ID:  <Pine.BSF.4.21.0103070204210.11775-100000@besplex.bde.org>
In-Reply-To: <xzpae6zxch6.fsf@flood.ping.uio.no>

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On 6 Mar 2001, Dag-Erling Smorgrav wrote:

> Bruce Evans <bde@zeta.org.au> writes:
> >       [...]  The DDB key would still work if the keyboard interrupt has
> > higher priority than the card interrupt.
> 
> The keyboard interrupt is irq 1, which has higher priority than
> anything except the clock (irq 0).

Er, no.  First, FreeBSD programs the ICU priorities to order 3-7,0-2
in the non-PC98 case.  Thus irq 1 has one of the lowest priorities
(only irq2 and thus irq8-15 are lower).  Second, ICU prioritization
has very little affect on FreeBSD interrupt prioritization.  It
affects fast interrupts but doesn't affect ithreads.  The priorities
in <sys/priority.h> are used for ithreads.  I think the keyboard
ithread has the relatively low priority PI_TTYLOW.  The DDB key
would work better if the ithread had priority PI_TTYHIGH.  The
busy-wait LED setting code in the ithread should be fixed before
raising the priority.

Bruce


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