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Message-ID: <3C418CCC.3854D76E@linux-m68k.org>
Date: Sun, 13 Jan 2002 14:34:04 +0100
From: Roman Zippel <zippel@linux-m68k.org>
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: arjan@fenrus.demon.nl, Rob Landley <landley@trommello.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [2.4.17/18pre] VM and swap - it's really unusable
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Hi,

Alan Cox wrote:

> disable_irq only blocks _one_ interrupt line, spin_lock_irqsave locks the
> interrupt off on a uniprocessor, and  50% of the time off on a
> dual processor.
> 
> If I use a spin lock you can't run a modem and an NE2000 card together on
> Linux 2.4. Thats why I had to do that work on the code. Its one of myriads
> of basic obvious cases that the pre-empt patch gets wrong

I wouldn't say it gets it wrong, the driver also has to take a non irq
spinlock anyway, so the window is quite small and even then the packet
is only delayed.
But now I really have to look at that driver and try a more optimistic
irq disabling approach, otherwise it will happily disable the most
important shared interrupt on my Amiga for ages.

bye, Roman
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