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

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Message-ID: <20100326101241.GZ20695@one.firstfloor.org>
Date:	Fri, 26 Mar 2010 11:12:41 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, Ingo Molnar <mingo@...e.hu>,
	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>,
	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

On Fri, Mar 26, 2010 at 11:08:53AM +0100, Peter Zijlstra wrote:
> On Fri, 2010-03-26 at 09:59 +0000, Alan Cox wrote:
> > > 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.
> > 
> > I don't think it's as rare as you think particularly in embedded, and the
> > moment you start explicitly using local_irq_enable() you've simply moved
> > the underlying problem back and made it far harder to grep for.
> 
> We've got local_irq_enable_in_hardirq() which should be used and can
> easily be grep'ed for.
> 
> But yes, I would much prefer to simply convert these known slow handlers
> to threaded interrupts.

That could be potentially hundreds in old obscure drivers all over the tree.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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