netdev - Re: [Pv-drivers] [PATCH] vmxnet3: set carrier state properly on probe

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Message-ID: <1359487030.4144.10.camel@bwh-desktop.uk.solarflarecom.com>
Date:	Tue, 29 Jan 2013 19:17:10 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Neil Horman <nhorman@...driver.com>
CC:	Dmitry Torokhov <dtor@...are.com>, <pv-drivers@...are.com>,
	<netdev@...r.kernel.org>, "David S. Miller" <davem@...emloft.net>
Subject: Re: [Pv-drivers] [PATCH] vmxnet3: set carrier state properly on
 probe

On Tue, 2013-01-29 at 14:09 -0500, Neil Horman wrote:
> On Tue, Jan 29, 2013 at 10:54:28AM -0800, Dmitry Torokhov wrote:
> > On Tuesday, January 29, 2013 05:54:11 PM Ben Hutchings wrote:
> > > On Fri, 2013-01-25 at 15:54 -0500, Neil Horman wrote:
> > > > vmxnet3 fails to set netif_carrier_off on probe, meaning that when an
> > > > interface is opened the __LINK_STATE_NOCARRIER bit is already cleared,
> > > > and so /sys/class/net/<ifname>/operstate remains in the unknown state. 
> > > > Correct this by setting netif_carrier_off on probe, like other drivers
> > > > do.
> > > > 
> > > > Also, while we're at it, lets remove the netif_carrier_ok checks from the
> > > > link_state_update function, as that check is atomically contained within
> > > > the netif_carrier_[on|off] functions anyway
> > > > 
> > > > Tested successfully by myself
> > > > 
> > > > Signed-off-by: Neil Horman <nhorman@...driver.com>
> > > > CC: "David S. Miller" <davem@...emloft.net>
> > > > CC: "VMware, Inc." <pv-drivers@...are.com>
> > > > ---
> > > > 
> > > >  drivers/net/vmxnet3/vmxnet3_drv.c | 7 +++----
> > > >  1 file changed, 3 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c
> > > > b/drivers/net/vmxnet3/vmxnet3_drv.c index b1c90f8..66c26a9 100644
> > > > --- a/drivers/net/vmxnet3/vmxnet3_drv.c
> > > > +++ b/drivers/net/vmxnet3/vmxnet3_drv.c
> > > 
> > > [...]
> > > 
> > > > @@ -3067,6 +3065,7 @@ vmxnet3_probe_device(struct pci_dev *pdev,
> > > > 
> > > >  		goto err_register;
> > > >  	
> > > >  	}
> > > > 
> > > > +	netif_carrier_off(netdev);
> > > > 
> > > >  	vmxnet3_check_link(adapter, false);
> > > >  	return 0;
> > > 
> > > You should do this before calling register_netdev(), otherwise the link
> > > state change can race with vmxnet3_open().
> > 
> > Hmm, is it safe to do before the network device is registered? The rest
> > of the drivers (e1000, tg3, etc) seem to be doing netif_carrier_off()
> > in open() rather than probe() and then do link checks.
> > 
> It appears to be safe to me, at least for the netif_carrier_off case, as theres
> a check to effecitvely just set the NOCARRIER bit if the device is in
> UNREGISTERED state.

Right, I made this work properly a little while ago (commit
8f4cccbbd92f).  Previous best practice was to call netif_carrier_off()
after registration, but userland could still see the wrong operstate
because linkwatch updates it asynchronously.

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.

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