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Date:      Mon, 8 Jul 2002 17:15:08 -0700
From:      David Greenman-Lawrence <dg@root.com>
To:        Peter Wemm <peter@wemm.org>
Cc:        Luigi Rizzo <luigi@FreeBSD.org>, Don Lewis <dl-freebsd@catspoiler.org>, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/dev/fxp if_fxp.c
Message-ID:  <20020708171508.E71311@nexus.root.com>
In-Reply-To: <20020708215808.B34E53808@overcee.wemm.org>; from peter@wemm.org on Mon, Jul 08, 2002 at 02:58:08PM -0700
References:  <20020708145235.I77043@iguana.icir.org> <20020708215808.B34E53808@overcee.wemm.org>

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>Luigi Rizzo wrote:
>> On Mon, Jul 08, 2002 at 02:39:35PM -0700, Don Lewis wrote:
>> ...
>> > I just started seeing fxp timeouts on my -current box since I upgraded
>> > the morning of July  7.
>> 
>> and why is this surprising ? This is the expected behaviour if you
>> cannot transmit a packet within 5 seconds...
>
>I've suddenly started getting them too.
>..
>fxp0: device timeout
>fxp0: device timeout
>..
>
>It is suprising because it appears to be working fine and has been working
>fine for years.  It seems the only relevant thing that has recently changed
>is that you touched the fxp driver..

   I suspect that Luigi doesn't understand how the fxp driver transmit side 
works, especially in the way that transmit interrupts are done. Transmit
interrupts are only generated as a way of garbage collection when there
are no more descriptors available. This is an important optimization and
is a fundamental difference from the way most other drivers work.
   In other words, transmit interrupts don't happen for every packet (or
even set of packets) like I think Luigi is expecting.

-DG

D.G.Lawrence
Download Technologies, Inc. - http://www.downloadtech.com - (866) 399 8500
TeraSolutions, Inc. - http://www.terasolutions.com - (503) 288 9544
The FreeBSD Project - http://www.freebsd.org
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