Re: [Patch] netxen_nic: Bugfix for wrong RUNNING status of NX3031 NICs with no link

[Ben Hutchings <bhutchings@solarflare.com>]

On Thu, 2014-01-02 at 17:16 +0800, jiang.biao2@zte.com.cn wrote:
> > You cannot do this, because at the very exact moment you call
> > register_netdevice() the device can be brought up and once the
> > device is up the link can be brought up.
> 
> > Therefore if you invoke netif_carrier_off() right after
> > register_netdevice(), it can cancel out a legitimate
> > netif_carrier_on() call.
> 
> register_netdevice() should be call in probe(), at that time, is
> it impossible to bring up device because the driver loading has
> not finished?

So far as the networking core is concerned, when register_netdevice() is
called the device is ready to use.  But you can do:

rtnl_lock();
register_netdevice();
netif_carrier_off();
rtnl_unlock();

However, as I said before, the current order in netxen_nic works and
only older kernel versions require you to call netif_carrier_off() after
registering the device.

> Even that, the netif_carrier_off() will be called before
> netif_carrier_on(), and that will not be a problem.
> 
> Besides, the other net drivers(e.g igb, e1000, e1000e) I saw all
> call netif_carrier_off() after register_netdev(). There is no such
> problems in these drivers.

It is not easy to hit the race condition but it is real.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.