Re: lockups with netconsole on e1000 on media insertion

[Matt Mackall <mpm@selenic.com>]

On Fri, Aug 05, 2005 at 01:45:55PM +0200, Andi Kleen wrote:
> John B?ckstrand <sandos@home.se> writes:
> 
> > I've been trying to hunt down a hard lockup issue with some hardware
> > of mine, but I've possibly hit a kernel bug instead. When using
> > netconsole on my e1000, if I unplug the cable and then re-plug it, the
> > machine locks up hard. It manages to print the "link up" message on
> > the screen, but nothing after that. Now, I wonder if this is supposed
> > to be so? I tried this on 4 different configurations, 2.6.13-rc5 and
> > 2.6.12 with and without "noapic acpi=off", same result on all of
> > them. I've tried with 1 and 3 other NICs in the machine at the same
> > time.
> 
> I ran into the same problem some time ago on e1000. The problem was
> that if the link doesn't come up netconsole ends up waiting forever
> for it.

I still don't like this fix. Yes, you're right, it should eventually
give up. But here it gives up way too easily - 5 could easily
translate to 5 microseconds. This is analogous to giving up on serial
transmit if CTS is down for 5 loops.

I'd be much happier if there were some udelay or the like in here so
that we're not giving up on such a short timeframe.

-- 
Mathematics is the supreme nostalgia of our time.