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Re: PATCH 2.4.0.9.2: export ethtool interface

To: "howling@xxxxxxxx" <havanna_moon@xxxxxxx>
Subject: Re: PATCH 2.4.0.9.2: export ethtool interface
From: Andrew Morton <andrewm@xxxxxxxxxx>
Date: Wed, 20 Sep 2000 20:30:55 +1100
Cc: netdev@xxxxxxxxxxx
References: <39C5D263.8DA31C03@xxxxxxxxxxxxxxxx> <39C75CB6.E86C55F@xxxxxxxxxx> <008101c02276$fe4fc5a0$1cac243e@dustin>
Sender: owner-netdev@xxxxxxxxxxx
"howling@xxxxxxxx" wrote:
> 
> Routers have a tendency not to announce routes for networks
> that are physically down, i miss that in linux. Mr. Becker
> suggested using libmii was a no-no-never solution (up to a few
> ms lockup of the machine per poll) for this issue. Select as
> you suggest seems ideal.

mm.. I've clocked an mdio_read() at 300 usecs.   Not a thing you'd want
to poll very frequently, particularly as some drivers are racy in this
area, and the consequences of hitting the race could be quite bad.  
spin_lock_bh() is the correct solution for mdio protection, BTW.

Of course, with many devices you simply _have_ to poll.

But if someone is setting up a multi-node HA system or a router, it's
not unreasonable to expect them to fork out the $$$ for a NIC which
generates link status change interrupts, and to be prepared to use
twisted pair.

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