From owner-freebsd-current  Fri Sep 21 23: 4:25 2001
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Date: Fri, 21 Sep 2001 23:05:06 -0700
From: Terry Lambert <tlambert2@mindspring.com>
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To: John Baldwin <jhb@FreeBSD.org>
Cc: Julian Elischer <julian@elischer.org>, current@FreeBSD.org,
	Julian Elischer <julian@FreeBSD.org>,
	Jun Kuriyama <kuriyama@imgsrc.co.jp>,
	Dag-Erling Smorgrav <des@ofug.org>, Josef Karthauser <joe@tao.org.uk>
Subject: Re: Problems with interrupts on -current.
References: <XFMail.010921120014.jhb@FreeBSD.org>
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John Baldwin wrote:
> The problem is that during a fast interrupt handler, we don't acknowledge the
> interrupt until we return from the interrupt handler, so if we preempt it may
> be a while before we get back to the interrupted process so it can finish the
> interrupt handler and ack the interrupt in the PIC.

I think that you're also going to find some overhead problems
related to interrupt threads when it comes to NETISR running
in a seperate thread, as well.  If nothing else, you are going
to be paying an additional context switch overhead to switch
to the NETISR thread that you weren't paying before.

I don't really buy Julian's "IDE stack depth" worst case
argument: the fix for that is to fix the IDE drivers to not
suck up huge chunks of stack to do their work.

-- Terry

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