netdev - Re: netxen: box stuck in netxen_napi

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Date:	Thu, 22 Jan 2015 09:37:01 +0100
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: netxen: box stuck in netxen_napi_disable()

On Wed, 2015-01-21 at 22:52 -0800, Eric Dumazet wrote: 
> On Thu, 2015-01-22 at 07:15 +0100, Mike Galbraith wrote:
> > On Wed, 2015-01-21 at 21:57 -0800, Eric Dumazet wrote:
> > 
> > > This driver doesn't follow the NAPI model correctly.
> > > 
> > > Please try following fix :
> > 
> > Thanks Eric, I'll plug it in in a bit and poke at it.  No news is good
> > news, as good as news gets for unknown repeatability bugs that is ;-)
> 
> To trigger the bug, all you had to do was to stress the transmit side.

Nope, it's easier than that...

> You could reduce MAX_STATUS_HANDLE from 64 to 4 to trigger it even
> faster.

Wow, that made it amazingly easy to verify.

With MAX_STATUS_HANDLE=4, without your patch applied box hangs as soon
as I bring the network up.  Add your patch on top, all is peachy.  Fresh
boot, or rmmod/modprobe and network restart, doesn't matter, box works
with your patch, is dead without it.

Here's an ornament for the fix if you think it'll look prettier :)

Reported-and-tested-by: Mike Galbraith <umgwanakikbuti@...il.com>

-Mike

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