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Subject: Re: [2.4.17/18pre] VM and swap - it's really unusable
From: Robert Love <rml@tech9.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: arjan@fenrus.demon.nl, Rob Landley <landley@trommello.org>,
        linux-kernel@vger.kernel.org
In-Reply-To: <E16PTIR-0002sL-00@the-village.bc.nu>
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Date: 12 Jan 2002 14:26:27 -0500
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On Sat, 2002-01-12 at 13:54, Alan Cox wrote:
> Another example is in the network drivers. The 8390 core for one example
> carefully disables an IRQ on the card so that it can avoid spinlocking on 
> uniprocessor boxes.
> 
> So with pre-empt this happens
> 
> 	driver magic
> 	disable_irq(dev->irq)
> PRE-EMPT:
> 	[large periods of time running other code]
> PRE-EMPT:
> 	We get back and we've missed 300 packets, the serial port sharing
> 	the IRQ has dropped our internet connection completely.

We don't preempt while IRQ are disabled.

	Robert Love

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