Date: Tue, 17 Mar 2009 13:28:20 -0700 (PDT) From: Barney Cordoba <barney_cordoba@yahoo.com> To: Paolo Pisati <p.pisati@oltrelinux.com>, Robert Watson <rwatson@FreeBSD.org> Cc: current@freebsd.org Subject: Re: Interrupt routine usage not shown by top in 8.0 Message-ID: <270142.53274.qm@web63902.mail.re1.yahoo.com> In-Reply-To: <alpine.BSF.2.00.0903171524040.55043@fledge.watson.org>
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--- On Tue, 3/17/09, Robert Watson <rwatson@FreeBSD.org> wrote:
> From: Robert Watson <rwatson@FreeBSD.org>
> Subject: Re: Interrupt routine usage not shown by top in 8.0
> To: "Paolo Pisati" <p.pisati@oltrelinux.com>
> Cc: "Barney Cordoba" <barney_cordoba@yahoo.com>, current@freebsd.org
> Date: Tuesday, March 17, 2009, 11:24 AM
> On Tue, 17 Mar 2009, Paolo Pisati wrote:
>
> > perhaps i misunderstood your question, but i'll
> try to explain a bit:
> >
> > before 7.0, bus_setup_intr() took just one function
> thus you could have an INTR_FAST or an INTR_MPSAFE handler,
> and you choose the kind of handler via a flag (INTR_FAST in
> this case).
> >
> > after 7.0, bus_setup_intr() took 2 functions, thus you
> could have: a fast handler (aka filter), or an ithread
> handler (aka mpsafe), or a fast + ithread handler (available
> only with INTR_FILTER turned on).
> >
> > in bus_setup_intr() the first function pointer is for
> the filter side of the handler, while the second pointer is
> for the ithread part, and if you declare both you can filter
> events (interrupts) and call the rest of the device driver
> (the ithread part) after the filter has recognized and
> acknowledged&masked the interrupt.
>
> This clarifies my misunderstanding, thanks!
>
I'd still be interested in knowing the specific advantage/consequences
of a fast filter vs an MPSAFE ithread?
In what circumstance would using a filter and then launching a task be
advantageous over just using an ithread?
Barney
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