linux-kernel - Re: [RFC patch 2/5] genirq: add a quick check handler

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Date:	Fri, 3 Oct 2008 12:37:28 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Christoph Hellwig <hch@...radead.org>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...l.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Arjan van de Veen <arjan@...radead.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jon Masters <jonathan@...masters.org>,
	Sven Dietrich <sdietrich@...e.de>
Subject: Re: [RFC patch 2/5] genirq: add a quick check handler

On Fri, 3 Oct 2008, Christoph Hellwig wrote:

> On Wed, Oct 01, 2008 at 11:02:18PM -0000, Thomas Gleixner wrote:
> > Preparatory patch for threaded interrupt handlers.
> > 
> > Adds a quick check handler which is called before the real handler.
> > The quick check handler can decide whether the interrupt was originated
> > from the device or not. It can also declare the interrupt as handled
> > and subsequently avoid that the real handler is called.
> 
> I'd rather leave the handler as a handle which could return
> IRQ_NEEDS_HANDLING to get a separate thread_fn called.  This seems more
> intuitive and means less mess in the fastpath.

see patch 3/5 :)
 
> Maybe IRQ_NEEDS_HANDLING might better be named IRQ_THREADED os similar,
> but that's really getting into nitpicking..

The reason why I split this out is: when you start to convert your
driver, then you can split out the quick check handler first w/o
making the real handler threaded in the first place. Once you got that
right you can work on moving the real handler into a thread.

Thanks,

	tglx

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