netdev - Re: netconsole breaks netpoll on bridge

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Message-ID: <20140617113952.GE8539@hmsreliant.think-freely.org>
Date:	Tue, 17 Jun 2014 07:39:52 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
Cc:	Francois Romieu <romieu@...zoreil.com>,
	Cong Wang <cwang@...pensource.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	David Miller <davem@...emloft.net>,
	"bridge@...ts.linux-foundation.org" 
	<bridge@...ts.linux-foundation.org>,
	Linux Netdev List <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: netconsole breaks netpoll on bridge

On Tue, Jun 17, 2014 at 08:06:58AM +0200, Stefan Priebe - Profihost AG wrote:
> Am 16.06.2014 23:30, schrieb Francois Romieu:
> > Stefan Priebe - Profihost AG <s.priebe@...fihost.ag> :
> > [...]
> >> That sounds great! Is there anything I can do or some code I can port to veth?
> > 
> > You may add an empty handler for .ndo_poll_controller in drivers/net/veth.c
> > and give it a try on current kernel.
> > 
> > It should not be too bad.
> > 
> Why is an empty poll controller enough to fix it? This sounds a bit
> crazy to me.
> 
Because the presence of a non-null poll_controller method is how we determine if
a device supports netpoll.  Most devices require a ndo_poll_controller function
to simulate an interrupt for receiving packets, but virtual devices really
don't, so an empty function sufficies to get the device recognized as having
netpoll support.  See tun_poll_controller as an example
Neil

> 
> Greets,
> Stefan
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