netdev - Re: [PATCH v5 1/1 net] net: fec: fix kernel oops when plug/unplug cable many times

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Message-ID: <1368559834.4519.23.camel@edumazet-glaptop>
Date:	Tue, 14 May 2013 12:30:34 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Fabio Estevam <festevam@...il.com>
Cc:	Shawn Guo <shawn.guo@...aro.org>,
	Frank Li <Frank.Li@...escale.com>, romieu@...zoreil.com,
	r.schwebel@...gutronix.de, davem@...emloft.net,
	l.stach@...gutronix.de, netdev@...r.kernel.org, lznuaa@...il.com
Subject: Re: [PATCH v5 1/1 net] net: fec: fix kernel oops when plug/unplug
 cable many times

On Tue, 2013-05-14 at 16:27 -0300, Fabio Estevam wrote:
> On Mon, May 13, 2013 at 1:57 AM, Shawn Guo <shawn.guo@...aro.org> wrote:
> 
> > The patch has landed on 3.10-rc1.  Seems that it introduces a lock
> > warning as below.  Turn on CONFIG_PROVE_LOCKING and you will be able
> > to see it.
> 
> This makes the warning goes away on mx28:
> 
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -451,7 +451,6 @@ fec_restart(struct net_device *ndev, int duplex)
>                 netif_device_detach(ndev);
>                 napi_disable(&fep->napi);
>                 netif_stop_queue(ndev);
> -               netif_tx_lock(ndev);
>         }
> 
>         /* Whack a reset.  We should wait for this. */
> @@ -619,7 +618,6 @@ fec_restart(struct net_device *ndev, int duplex)
>                 netif_device_attach(ndev);
>                 napi_enable(&fep->napi);
>                 netif_wake_queue(ndev);
> -               netif_tx_unlock(ndev);
>         }
>  }
> 
> ,but not sure if it looks OK.
> --

Thats because netif_tx_lock_bh() should be used.

And btw, the order of the unlocks should probably be reversed :

              netif_tx_unlock_bh(ndev);
              netif_wake_queue(ndev);
              napi_enable(&fep->napi);
              netif_device_attach(ndev);



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