linux-kernel - Re: [patch 0/2] Run interrupt handlers always with interrupts disabled

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Date:	Fri, 26 Mar 2010 10:20:23 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Nicolas Pitre <nico@...xnic.net>,
	Linus Torvalds <torvalds@...l.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Andi Kleen <andi@...stfloor.org>,
	David Miller <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Russell King <rmk@....linux.org.uk>
Subject: Re: [patch 0/2] Run interrupt handlers always with interrupts
 disabled


* Russell King <rmk@....linux.org.uk> wrote:

> On Fri, Mar 26, 2010 at 12:06:44AM -0000, Thomas Gleixner wrote:
> > The following patch series removes the IRQF_DISABLED functionality
> > from the core interrupt code and runs all interrupt handlers with
> > interrupts disabled.
> 
> As was covered in previous discussions, what about drivers such as SMC91x 
> which take a long time to retrieve packets from the hardware? Always running 
> handlers with IRQs disabled will kill things such as serial on these 
> platforms.

As long as it's rare (which it is) i dont see a problem: you can enable 
interrupts in the handler by using local_irq_enable(), like the IDE PIO 
drivers do. That way it's documented a bit better as well, because it shows 
the precise source of the latency, with a big comment explaining it, etc.

Thanks,

	Ingo
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