linux-kernel - Re: [patch 0/2] Add support for threaded interrupt handlers

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Date:	Wed, 25 Mar 2009 08:39:11 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Brownell <david-b@...bell.net>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Arjan van de Veen <arjan@...radead.org>,
	Jon Masters <jonathan@...masters.org>,
	Sven Dietrich <sdietrich@...e.de>
Subject: Re: [patch 0/2] Add support for threaded interrupt handlers - V3

On Tue, 24 Mar 2009, David Brownell wrote:

> On Tuesday 24 March 2009, Thomas Gleixner wrote:
> > On Tue, 24 Mar 2009, David Brownell wrote:
> > > On Monday 23 March 2009, Thomas Gleixner wrote:
> > > > I'm still looking into a clean solution for the threaded demultiplex
> > > > handler case which was brought up by Dave to allow both the handling
> > > > of the demultiplexed devices in the context of the demultiplexer
> > > > interrupt thread and the wakeup of separate handler threads. But this
> > > > is an orthogonal extension of the existing patch set and does not
> > > > change the general design.
> > > 
> > > No comments on the patch I sent?
> > 
> > Looked at it briefly, but I still try to figure out what the best
> > solution for this will be. As I said I'd like to support both
> > variants:
> > 
> > 1) demux handlers run in the primary interrupt thread context
> > 2) demux handlers kick their own handler threads
> 
> I have no need for the latter, at least in current systems.

Groan, the fact that you do not need it is definitely _not_ a good
reason to just add a irq_is_sufficient_for_dave_handler.

> > I don't want to special case that. See above.
> 
> What's a special case though?  If you're serious about
> wanting to support more than one case, it's always going
> to be possible to call some of them "special".  As in,
> "threaded IRQs are a special case in genirq".  That should
> not mean they don't get handled.

I don't like the idea of another action dispatcher in a special case
handler. The goal is to reuse the code i.e. simple_handler and
handle_IRQ_event. It just needs some thoughts to implement it in a
sane way.

Thanks,

	tglx
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