netdev - Re: netconsole system freeze when cable unplugged

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Message-ID: <45F1EE12.2070605@simon.arlott.org.uk>
Date:	Fri, 09 Mar 2007 23:30:26 +0000
From:	Simon Arlott <simon@...e.lp0.eu>
To:	Francois Romieu <romieu@...zoreil.com>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: Re: netconsole system freeze when cable unplugged

On 09/03/07 20:42, Francois Romieu wrote:
> Simon Arlott <simon@...e.lp0.eu> :
>> When I unplug the cable the system just stops responding to anything, 
>> at all. No message is printed to the console when the cable is plugged 
>> back in.
> 
> rtl8139_interrupt (spin_lock(&tp->lock))
> -> rtl8139_weird_interrupt
>    -> rtl_check_media
>       -> mii_check_media (printk(KERN_INFO "%s: link down\n", ...))
>          [netpoll stuff here]
>          -> rtl8139_poll_controller
>             -> rtl8139_interrupt
>                *deadlock*
> 
> See below for my random stuff of the day. Feel free to open a PR at
> bugzilla.kernel.org if the issue does not go away.

The patch doesn't fix it, nothing changes. I'm not sure how this can 
be debugged if printk won't work...

> --------8<-----------------------------------------------------------------
> 
> 8139too: netconsole breakage when link changes
> 
> rtl8139_interrupt is not supposed to be reentrant but its link
> management part can emit printk.
> 
> Signed-off-by: Francois Romieu <romieu@...zoreil.com>
> 
> diff --git a/drivers/net/8139too.c b/drivers/net/8139too.c
> index 99304b2..64467ad 100644
> --- a/drivers/net/8139too.c
> +++ b/drivers/net/8139too.c
> @@ -2215,9 +2215,16 @@ static irqreturn_t rtl8139_interrupt (int irq, void *dev_instance)
>   */
>  static void rtl8139_poll_controller(struct net_device *dev)
>  {
> -	disable_irq(dev->irq);
> +	struct rtl8139_private *tp = netdev_priv(dev);
> +	unsigned long flags;
> +	int rc;
> +
> +	rc = spin_trylock_irqsave(&tp->lock, flags);
> +	if (!rc)
> +		return;
> +	spin_unlock(&tp->lock);
>  	rtl8139_interrupt(dev->irq, dev);
> -	enable_irq(dev->irq);
> +	local_irq_restore(flags);
>  }
>  #endif
>  
> -
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-- 
Simon Arlott
-
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