netdev - Re: [PATCH] natsemi: netpoll fixes

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Message-ID: <20070305224140.GA16290@sirena.org.uk>
Date:	Mon, 5 Mar 2007 22:41:42 +0000
From:	Mark Brown <broonie@...ena.org.uk>
To:	netdev@...r.kernel.org
Subject: Re: [PATCH] natsemi: netpoll fixes

On Tue, Mar 06, 2007 at 12:10:08AM +0400, Sergei Shtylyov wrote:

>  #ifdef CONFIG_NET_POLL_CONTROLLER
>  static void natsemi_poll_controller(struct net_device *dev)
>  {
> +	struct netdev_private *np = netdev_priv(dev);
> +
>  	disable_irq(dev->irq);
> -	intr_handler(dev->irq, dev);
> +
> +	/*
> +	 * A real interrupt might have already reached us at this point
> +	 * but NAPI might still haven't called us back.  As the interrupt
> +	 * status register is cleared by reading, we should prevent an
> +	 * interrupt loss in this case...
> +	 */
> +	if (!np->intr_status)
> +		intr_handler(dev->irq, dev);
> +
>  	enable_irq(dev->irq);

Is it possible for this to run at the same time as the NAPI poll?  If so
then it is possible for the netpoll poll to run between np->intr_status
being cleared and netif_rx_complete() being called.  If the hardware
asserts an interrupt at the wrong moment then this could cause the 

In any case, this is a problem independently of netpoll if the chip
shares an interrupt with anything so the interrupt handler should be
fixed to cope with this situation instead.

-- 
"You grabbed my hand and we fell into it, like a daydream - or a fever."

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