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Date:   Fri, 26 Apr 2019 16:12:00 +0200
From:   Oleksandr Natalenko <oleksandr@redhat.com>
To:     Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc:     netdev@vger.kernel.org, intel-wired-lan@lists.osuosl.org,
        linux-kernel@vger.kernel.org,
        Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
        Sasha Levin <sashal@kernel.org>,
        Joseph Yasi <joe.yasi@gmail.com>,
        Aaron Brown <aaron.f.brown@intel.com>,
        Alexander Duyck <alexander.duyck@gmail.com>,
        e1000-devel@lists.sourceforge.net
Subject: Re: [PATCH 2/2] e1000e: start network tx queue only when link is up
Message-ID: <20190426141159.c5e4t4er4zjry7om@butterfly.localdomain>
References: <155548879651.3454.13167784936351314661.stgit@buzz>
 <155548880068.3454.1621821881762819373.stgit@buzz>
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On Wed, Apr 17, 2019 at 11:13:20AM +0300, Konstantin Khlebnikov wrote:
> Driver does not want to keep packets in tx queue when link is lost.
> But present code only reset NIC to flush them, but does not prevent
> queuing new packets. Moreover reset sequence itself could generate
> new packets via netconsole and NIC falls into endless reset loop.
> 
> This patch wakes tx queue only when NIC is ready to send packets.
> 
> This is proper fix for problem addressed by commit 0f9e980bf5ee
> ("e1000e: fix cyclic resets at link up with active tx").
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
> ---
>  drivers/net/ethernet/intel/e1000e/netdev.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index ba96e52aa8d1..fe643d66aa10 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -4209,7 +4209,7 @@ void e1000e_up(struct e1000_adapter *adapter)
>  		e1000_configure_msix(adapter);
>  	e1000_irq_enable(adapter);
>  
> -	netif_start_queue(adapter->netdev);
> +	/* tx queue started by watchdog timer when link is up */
>  
>  	e1000e_trigger_lsc(adapter);
>  }
> @@ -4607,6 +4607,7 @@ int e1000e_open(struct net_device *netdev)
>  	pm_runtime_get_sync(&pdev->dev);
>  
>  	netif_carrier_off(netdev);
> +	netif_stop_queue(netdev);
>  
>  	/* allocate transmit descriptors */
>  	err = e1000e_setup_tx_resources(adapter->tx_ring);
> @@ -4667,7 +4668,6 @@ int e1000e_open(struct net_device *netdev)
>  	e1000_irq_enable(adapter);
>  
>  	adapter->tx_hang_recheck = false;
> -	netif_start_queue(netdev);
>  
>  	hw->mac.get_link_status = true;
>  	pm_runtime_put(&pdev->dev);
> @@ -5289,6 +5289,7 @@ static void e1000_watchdog_task(struct work_struct *work)
>  			if (phy->ops.cfg_on_link_up)
>  				phy->ops.cfg_on_link_up(hw);
>  
> +			netif_wake_queue(netdev);
>  			netif_carrier_on(netdev);
>  
>  			if (!test_bit(__E1000_DOWN, &adapter->state))
> @@ -5302,6 +5303,7 @@ static void e1000_watchdog_task(struct work_struct *work)
>  			/* Link status message must follow this format */
>  			pr_info("%s NIC Link is Down\n", adapter->netdev->name);
>  			netif_carrier_off(netdev);
> +			netif_stop_queue(netdev);
>  			if (!test_bit(__E1000_DOWN, &adapter->state))
>  				mod_timer(&adapter->phy_info_timer,
>  					  round_jiffies(jiffies + 2 * HZ));
> 

Tested-by: Oleksandr Natalenko <oleksandr@redhat.com>

-- 
  Best regards,
    Oleksandr Natalenko (post-factum)
    Senior Software Maintenance Engineer