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Re: [patch 4/10] s390: network driver.

To: Tommy Christensen <tommy.christensen@xxxxxxxxx>
Subject: Re: [patch 4/10] s390: network driver.
From: jamal <hadi@xxxxxxxxxx>
Date: 10 Jan 2005 08:18:12 -0500
Cc: Jeff Garzik <jgarzik@xxxxxxxxx>, Thomas Spatzier <thomas.spatzier@xxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Hasso Tepper <hasso@xxxxxxxxx>, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>, netdev@xxxxxxxxxxx, Paul Jakma <paul@xxxxxxxx>
In-reply-to: <1105111605.3462.101.camel@tsc-6.cph.tpack.net>
Organization: jamalopolous
References: <OFB7F7E23F.EFB88418-ONC1256F7E.0031769E-C1256F7E.003270AD@de.ibm.com> <1104764710.1048.580.camel@jzny.localdomain> <41DB26A6.2070008@pobox.com> <1104895169.1117.63.camel@jzny.localdomain> <41DC0931.80603@tpack.net> <1105019912.2314.20.camel@jzny.localdomain> <1105023972.3462.48.camel@tsc-6.cph.tpack.net> <1105104757.1046.63.camel@jzny.localdomain> <1105111605.3462.101.camel@tsc-6.cph.tpack.net>
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On Fri, 2005-01-07 at 10:26, Tommy Christensen wrote:
> On Fri, 2005-01-07 at 14:32, jamal wrote:
> > On Thu, 2005-01-06 at 10:06, Tommy Christensen wrote:

[..]

> > reseting qdisc could certainly be part of the device watchdog.
> > Note that once the packets are drained, the next thing that will happen
> > if device is stopped for a dev->timeout period is watchdog kicking in
> > and flushing the DMA. So you could reset your qdisc there though i am
> > not sure it will be needed with that patch.
> 
> Unfortunately the watchdog won't do this when carrier is off, which
> is fair enough since the chip isn't hung as such.

We may have to kick the dog in that path as well then.

> So, we would need another method to flush out stale packets from
> the DMA ring. Some drivers already do this themselves, and some won't
> need it because they keep on running even when link is down.

kicking tx_timeout seems like the right thing to do until i looked at
the drivers. Sigh. I just stared at a few drivers and it is not pleasant
- and they mostly have the same theme (so you cant say they are
inconsistent).
Looking at e1000 for example is quiet interesting - it actually brings
down then up the device ;-> This will both flash the dma and reset qdisc
but also loose any static routes. It will also reschedule the device;-<
So i am not so sure that the dog kicking in a minute later is a good
thing at all. We may need a lot of janitorial work to cleanse the
drivers - something jgarzik is against. 

A qdisc_reset, as you suggest, will probably not cure the problem but
provide some cosmetics. Thoughts?

cheers,
jamal


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