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Date: Thu, 29 Jan 2009 14:58:25 +0200
From: Andriy Gapon <avg@icyb.net.ua>
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To: Ed Schouten <ed@80386.nl>
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Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org>
Subject: Re: INTR_FILTER?
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on 29/01/2009 14:55 Ed Schouten said the following:
> * Andriy Gapon <avg@icyb.net.ua> wrote:
>> INTR_FILTER - what does it do?
>> It doesn't seem to be documented anywhere, but seems to affect interrupt
>> code.
> 
> Not sure, but I think I was once told that FreeBSD has a `two level'
> interrupt handling scheme, where the filter is invoked directly to only
> figure out whether the interrupt is spurious or not. After it has been
> determined it is not, an interrupt thread is scheduled to handle the
> interrupt.
> 
> But as I said, I'm not sure. :-)
> 

This is true and is documented in bus_setup_intr(9).
But INTR_FILTER is a compile-time kernel option.

-- 
Andriy Gapon