linux-kernel - Re: lockdep and threaded IRQs (was: ...)

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Date:	Tue, 3 Mar 2009 11:03:29 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	David Brownell <david-b@...bell.net>,
	Andrew Morton <akpm@...ux-foundation.org>, me@...ipebalbi.com,
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
	felipe.balbi@...ia.com, dmitry.torokhov@...il.com,
	sameo@...nedhand.com, tglx@...utronix.de
Subject: Re: lockdep and threaded IRQs (was: ...)

* Alan Cox <alan@...rguk.ukuu.org.uk> wrote:

> > Therefore IRQF_DISABLED _will_ be forced on everybody some 
> > day soon, and I'll provide an IRQF_ENABLED for use by broken 
> > hardware only (and make a TAINT flag for that too).
> 
> I don't think you understand how the kernel project works. If 
> everyone thinks your change is inappropriate it won't get in.

The change that people had a problem with was the immediate 
removal of IRQF_ENABLED, and that's not on the plate anymore.

I dont think anyone offered any example where IRQF_ENABLED is 
used in a healthy way - they are all legacy or special hw quirks 
where we limp along with enabling IRQs in a hacky way.

Furthermore, even these quirky cases can be supported cleanly 
_without_ IRQF_ENABLED: where an IRQ handler can take a long 
time to execute, the handler can be converted to a threaded IRQ 
handler - where it's fine to enable IRQs as there are no stack 
nesting issues.

So there's no real technical problem here.

	Ingo
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