Re: [PATCH 1/1 v2 net] net: fec: fix kernel oops when plug/unplug cable many times

[Lucas Stach <l.stach@pengutronix.de>]

Hi Frank,

Am Sonntag, den 28.04.2013, 11:08 +0800 schrieb Frank Li:
> reproduce steps
>  1. flood ping from other machine
>  	ping -f -s 41000 IP
>  2. run below script
>     while [ 1 ]; do ethtool -s eth0 autoneg off;
>     sleep 3;ethtool -s eth0 autoneg on; sleep 4; done;
> 
> You can see oops in one hour.
> 
> The reason is fec_restart clear BD but NAPI may use it.
> The solution is disable NAPI and stop xmit when reset BD.
> disable NAPI may sleep, so fec_restart can't be call in
> atomic context.
> 
> Signed-off-by: Frank Li <Frank.Li@freescale.com>
> ---
> 
> Change from V1 to V2
> 	Add netif_tx_lock(ndev) to avoid xmit runing when reset hardware	
> 
>  drivers/net/ethernet/freescale/fec.c |   41 +++++++++++++++++++++++++++++-----
>  drivers/net/ethernet/freescale/fec.h |    3 +-
>  2 files changed, 37 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec.c b/drivers/net/ethernet/freescale/fec.c
> index 73195f6..d140b50 100644
> --- a/drivers/net/ethernet/freescale/fec.c
> +++ b/drivers/net/ethernet/freescale/fec.c
> @@ -403,6 +403,12 @@ fec_restart(struct net_device *ndev, int duplex)
>  	const struct platform_device_id *id_entry =
>  				platform_get_device_id(fep->pdev);
>  	int i;
> +	if (netif_running(ndev)) {
> +		napi_disable(&fep->napi);
> +		netif_stop_queue(ndev);
> +		netif_tx_lock(ndev);
> +	}
> +
>  	u32 temp_mac[2];
>  	u32 rcntl = OPT_FRAME_SIZE | 0x04;
>  	u32 ecntl = 0x2; /* ETHEREN */
> @@ -559,6 +565,12 @@ fec_restart(struct net_device *ndev, int duplex)
>  
>  	/* Enable interrupts we wish to service */
>  	writel(FEC_DEFAULT_IMASK, fep->hwp + FEC_IMASK);
> +
> +	if (netif_running(ndev)) {
> +		napi_enable(&fep->napi);
> +		netif_wake_queue(ndev);
> +		netif_tx_unlock(ndev);
> +	}
>  }
>  
>  static void
> @@ -598,8 +610,20 @@ fec_timeout(struct net_device *ndev)
>  
>  	ndev->stats.tx_errors++;
>  
> -	fec_restart(ndev, fep->full_duplex);
> -	netif_wake_queue(ndev);
> +	fep->timeout = 1;
> +	schedule_delayed_work(&fep->delay_work, msecs_to_jiffies(1));
> +}

Why are you using delayed work here? I don't see a reason why we would
like to defer execution here. Just use schedule_work().

> +
> +static void fec_enet_work(struct work_struct *work)
> +{
> +	struct fec_enet_private *fep =
> +		container_of(work, struct fec_enet_private, delay_work.work);
> +
> +	if (fep->timeout) {
> +		fep->timeout = 0;
> +		fec_restart(fep->netdev, fep->full_duplex);
> +		netif_wake_queue(fep->netdev);
> +	}
>  }
>  
>  static void
> @@ -996,9 +1020,6 @@ static void fec_enet_adjust_link(struct net_device *ndev)
>  			status_change = 1;
>  		}
>  
> -		/* if any of the above changed restart the FEC */
> -		if (status_change)
> -			fec_restart(ndev, phy_dev->duplex);
>  	} else {
>  		if (fep->link) {
>  			fec_stop(ndev);
> @@ -1010,8 +1031,14 @@ static void fec_enet_adjust_link(struct net_device *ndev)
>  spin_unlock:
>  	spin_unlock_irqrestore(&fep->hw_lock, flags);
>  
> -	if (status_change)
> +	if (status_change) {
> +		/* if any of the above changed restart the FEC,
> +		 * fec_restart may sleep. can't call it in spin_lock
> +		 */
> +		if (phy_dev->link)
> +			fec_restart(ndev, phy_dev->duplex);
>  		phy_print_status(phy_dev);
> +	}
>  }

Don't complicate things unnecessarily. Just put a patch in front of this
one to remove the spinlock. As you removed it already from the RX and TX
paths it doesn't protect anything anymore.

>  
>  static int fec_enet_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
> @@ -1882,6 +1909,7 @@ fec_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto failed_register;
>  
> +	INIT_DELAYED_WORK(&fep->delay_work, fec_enet_work);
>  	return 0;
>  
>  failed_register:
> @@ -1918,6 +1946,7 @@ fec_drv_remove(struct platform_device *pdev)
>  	struct resource *r;
>  	int i;
>  
> +	cancel_delayed_work_sync(&fep->delay_work);
>  	unregister_netdev(ndev);
>  	fec_enet_mii_remove(fep);
>  	del_timer_sync(&fep->time_keep);
> diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
> index eb43729..a367b21 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
> @@ -260,7 +260,8 @@ struct fec_enet_private {
>  	int hwts_rx_en;
>  	int hwts_tx_en;
>  	struct timer_list time_keep;
> -
> +	struct delayed_work delay_work;
> +	int timeout;
>  };
>  
>  void fec_ptp_init(struct net_device *ndev, struct platform_device *pdev);

-- 
Pengutronix e.K.                           | Lucas Stach                 |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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