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Subject: Re: [patch 0/2] Run interrupt handlers always with interrupts
 disabled
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>, Nicolas Pitre <nico@fluxnic.net>,
       Linus Torvalds <torvalds@osdl.org>, LKML <linux-kernel@vger.kernel.org>,
       linux-arch@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>, Andi Kleen <andi@firstfloor.org>,
       David Miller <davem@davemloft.net>, Greg Kroah-Hartman <gregkh@suse.de>,
       Arnaldo Carvalho de Melo <acme@redhat.com>,
       Russell King <rmk@arm.linux.org.uk>
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	 <20100326081457.GA23570@flint.arm.linux.org.uk>
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Date: Fri, 26 Mar 2010 10:28:12 +0100
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On Fri, 2010-03-26 at 10:20 +0100, Ingo Molnar wrote:
> * Russell King <rmk@arm.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.

Or alternatively, use threaded interrupts for such slow hardware.