netdev - Re: [PATCH net 3/3] eet: ena: invoke netif_carrier

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Message-ID: <20171228234603.436ba946@cakuba.netronome.com>
Date:   Thu, 28 Dec 2017 23:46:03 -0800
From:   Jakub Kicinski <kubakici@...pl>
To:     <netanel@...zon.com>
Cc:     <davem@...emloft.net>, <netdev@...r.kernel.org>, <dwmw@...zon.com>,
        <zorik@...zon.com>, <matua@...zon.com>, <saeedb@...zon.com>,
        <msw@...zon.com>, <aliguori@...zon.com>, <nafea@...zon.com>,
        <evgenys@...zon.com>, <gtzalik@...zon.com>
Subject: Re: [PATCH net 3/3] eet: ena: invoke netif_carrier_off() only after
 netdev registered

On Thu, 28 Dec 2017 21:30:20 +0000, netanel@...zon.com wrote:
> From: Netanel Belgazal <netanel@...zon.com>
> 
> netif_carrier_off() should be called only after register netdev.
> Move the function's call after the registration.

By "should" you mean in your driver, right?  I think calling
netif_carrier_off() on an unregistered netdev is a pretty standard
thing to do for drivers which manage carrier state.

> Signed-off-by: Netanel Belgazal <netanel@...zon.com>
> ---
>  drivers/net/ethernet/amazon/ena/ena_netdev.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> index fbe21a817bd8..ee50c56765a4 100644
> --- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
> +++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
> @@ -3276,14 +3276,14 @@ static int ena_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  
>  	memcpy(adapter->netdev->perm_addr, adapter->mac_addr, netdev->addr_len);
>  
> -	netif_carrier_off(netdev);
> -
>  	rc = register_netdev(netdev);
>  	if (rc) {
>  		dev_err(&pdev->dev, "Cannot register net device\n");
>  		goto err_rss;
>  	}
>  
> +	netif_carrier_off(netdev);
> +
>  	INIT_WORK(&adapter->reset_task, ena_fw_reset_device);

This looks suspicious.  After you call register_netdev() someone can
open the device and link may come up before you clear it again with
carrier off.  Leading to netdev without a carrier until it's reopened.

>  	adapter->last_keep_alive_jiffies = jiffies;