netdev - RE: [PATCH] bnx2: turn off the network statck during initialization

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Message-ID: <CEE05A0D7856E14880AD5560634EBEA834DB2ABC@SFO1EXC-MBXP06.nbttech.com>
Date:	Thu, 16 Aug 2012 19:15:30 +0000
From:	Jiang Wang <Jiang.Wang@...erbed.com>
To:	Michael Chan <mchan@...adcom.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Chaitanya Lala <Chaitanya.Lala@...erbed.com>,
	"Francis St. Amant" <Francis.St.Amant@...erbed.com>
Subject: RE: [PATCH] bnx2: turn off the network statck during initialization

Hi Michael,

I just checked the code for netif_carrier_off(), and it will return if the dev is not initialized (registered) as follows:

void netif_carrier_off(struct net_device *dev)
{
        if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
                if (dev->reg_state == NETREG_UNINITIALIZED)
                        return;
                linkwatch_fire_event(dev);
        }
}

So linkwatch_fire_event should not fire in this case, right? Thanks for the quick response.

Regards,

Jiang

-------------------------------------
Jiang Wang
Member of Technical Staff
Riverbed Technology
Tel: (408) 522-5109
Email: Jiang.Wang@...erbed.com
www.riverbed.com


-----Original Message-----
From: Michael Chan [mailto:mchan@...adcom.com] 
Sent: Thursday, August 16, 2012 11:57 AM
To: Jiang Wang
Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Chaitanya Lala; Francis St. Amant; Jiang Wang
Subject: Re: [PATCH] bnx2: turn off the network statck during initialization

On Thu, 2012-08-16 at 11:21 -0700, Jiang Wang wrote: 
> The initialization state of bnx2 driver is wrong. It does not turn of 
> the Linux network stack using netif_carrier_off. This may lead to 
> inconsistent report from ethtool as the link is up but speed is 
> unknown when the cable is not plugged in.
> 
> E.g.
>         Speed: Unknown! (0)<--------------------------------------
>         Duplex: Half       <--------------------------------------
>         MDI: Unknown! (0)
>         Port: Twisted Pair
>         PHYAD: 1
>         Transceiver: internal
>         Auto-negotiation: on
>         Supports Wake-on: g
>         Wake-on: d
>         Link detected: yes <---------------------------------------
> 
> This patches fixed the problem by turning off the network stack during 
> initialization.
> 
> Signed-off-by: Jiang Wang <jwang@...erbed.com>
> ---
>  drivers/net/ethernet/broadcom/bnx2.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/bnx2.c 
> b/drivers/net/ethernet/broadcom/bnx2.c
> index ac7b744..ce4548d 100644
> --- a/drivers/net/ethernet/broadcom/bnx2.c
> +++ b/drivers/net/ethernet/broadcom/bnx2.c
> @@ -8463,6 +8463,10 @@ bnx2_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
>  	dev->features |= dev->hw_features;
>  	dev->priv_flags |= IFF_UNICAST_FLT;
>  
> +	/* tell the stack to leave us alone until bnx2_open() is called */
> +	netif_carrier_off(dev);

We have tried this before and this didn't work.  netif_carrier_off() calls linkwatch_fire_event() to schedule the event.  If
register_netdev() fails for whatever reason, the netdev will be freed but the link_watch event may still be scheduled.

Calling netif_carrier_off() after register_netdev() returns successfully also may not work as it will race with bnx2_open() which enables IRQ.
An linkup IRQ can happen at time and we may end up with the wrong carrier state because of the race condition.

> +	netif_stop_queue(dev);
> +
>  	if ((rc = register_netdev(dev))) {
>  		dev_err(&pdev->dev, "Cannot register net device\n");
>  		goto error;



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