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Re: True on TRANSMIT ERROR TIMEOUT

To: Andrew Morton <andrewm@xxxxxxxxxx>
Subject: Re: True on TRANSMIT ERROR TIMEOUT
From: Andrey Savochkin <saw@xxxxxxxxxxxxx>
Date: Thu, 15 Jun 2000 12:24:01 +0800
Cc: vortex <vortex@xxxxxxxxx>, eepro100 <eepro100@xxxxxxxxx>, tulip <tulip@xxxxxxxxx>, netdev <netdev@xxxxxxxxxxx>, Bogdan Costescu <Bogdan.Costescu@xxxxxxxxxxxxxxxxxxxxx>
In-reply-to: <39483426.B07E4BA@xxxxxxxxxx>; from "Andrew Morton" on Thu, Jun 15, 2000 at 01:40:54AM
References: <39461BB3.299DD807@xxxxxxxxxx> <Pine.LNX.4.10.10006141420380.370-100000@xxxxxxxxxxxxxxxxxxxxxxxxxxx> <39483426.B07E4BA@xxxxxxxxxx>
Sender: owner-netdev@xxxxxxxxxxx
Hello,

On Thu, Jun 15, 2000 at 01:40:54AM +0000, Andrew Morton wrote:
> Well, I didn't say "let's put in lots of bugs" :)
> 
> My point is very simple:
> 
> - Drivers and/or NICs are hanging
> - The hangs are fixed by down+up or rmmod+insmod
> 
> Hence, the hangs _could_ be unhung by appropriate action
> in the tx timeout!
> 
> This would be a great step forward.  A sub-second hiccup and
> a few dropped packets versus a complete system outage.

The main problem is not the action in timeout routine.
The problem is that these routines should be extensively debugged by the
authors/maintainers of all drivers.

TX timeout routine catches cases that shouldn't happen in real life.
It's a redundant code, and it's pity that it's called so often.
It depends on the hardware what actions should be taken in these "impossible"
cases.

Speaking about eepro100, I initially thought that the restart of the
transmitter unit is meaningful and sufficient.  When I started to debug the
code, artificially trying to cause TX timeouts, I found that it's not true.
The hardware works in a way that receiver problems leads to TX unit stall
after a short time.  I personally consider it as a hardware bug, but I should
cope with it.  Currently, TX timeout routine does full reset, just like for
interface down and up.

If the current timeout handler fails in its mission, I'm fixing it.
I just need user's patience and help.  I have only one head and two hands to
clatter on keyboard, and I can't fix in a flash.

Andrew, you should consider what is appropriate for your driver, basing on
user's reports.  Other drivers are only hints on what may be done.

Best regards
                                        Andrey

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