linux-kernel - Re: [patch 2/3] genirq: warn about IRQF_SHARED|IRQF

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Date:	Fri, 12 Mar 2010 17:14:23 -0500
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	u.kleine-koenig@...gutronix.de, a.p.zijlstra@...llo.nl,
	andrea.gallo@...ricsson.com, dbrownell@...rs.sourceforge.net,
	eric.y.miao@...il.com, hugh.dickins@...cali.co.uk,
	jamie@...reable.org, John Stultz <johnstul@...ibm.com>,
	linux@...mer.net, nico@...vell.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Greg KH <greg@...ah.com>, David Miller <davem@...emloft.net>
Subject: Re: [patch 2/3] genirq: warn about IRQF_SHARED|IRQF_DISABLED at the
 right place

On Sat, 13 Mar 2010 01:59:50 +0100 (CET) Thomas Gleixner <tglx@...utronix.de> wrote:

> 
> I'm simply refusing to apply patches which just shuffle code around to
> warn about obscure use cases instead of tackling the real problem of
> long running irq handlers which prevent us to get rid of IRQF_DISABLED
> and just run all interrupt handlers with irqs disabled.

I'm having trouble agreeing with that aim, really.

We can tweak and tune until we're blue in the face, but the system's
IRQ latency will always be worse if handlers always run with interrupts
disabled.

Plus this approach introduces dependencies between unrelated drivers
(and between _each_ driver and the overall system) which simply don't
exist if those drivers are being nicer to the rest of the system.

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