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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
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Date: 13 Jan 2002 13:20:08 -0500
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On Sun, 2002-01-13 at 10:59, Alan Cox wrote:
> > I disable a single specific interrupt, I don't disable the timer interrupt.
> > Your code doesn't seem to handle that.
> 
> It can if we increment the preempt_count in disable_irq_nosync and
> decrement it on enable_irq.

OK, Alan, you spooked me with the disable_irq mess and admittedly my
initial solution wasn't ideal for a few reasons.

But it isn't a problem after all. In hw_irq.h we bump the count in the
interrupt path.  This should handle any handler, however we end up in
it.

I realized it because if we did not have a global solution to interrupt
request handlers, dropping spinlocks in the handler, even with IRQs
disabled, would cause a preemptive schedule.  All interrupts are
properly protected.

	Robert Love

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