linux-kernel - Re: [PATCH] Fix crash in tg3 when using irqpoll

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Message-ID: <1174601067.9753.42.camel@dell>
Date:	Thu, 22 Mar 2007 14:04:27 -0800
From:	"Michael Chan" <mchan@...adcom.com>
To:	"Bernhard Walle" <bwalle@...e.de>
cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix crash in tg3 when using irqpoll

On Thu, 2007-03-22 at 21:46 +0100, Bernhard Walle wrote:

> 
> This patch makes sure that even the tr32() instruction in the interrupt handler
> is not executed which accesses PCI memory. Accessing PCI memory when
> pci_restore_state() is called is a bad idea because that function modifies
> the BARs of the PCI device.

It is not caused by the BAR as it doesn't get changed in this case.  The
pci_restore_state() call is to restore the memory enable bit in the PCI
command register.  The tr32() call in tg3_interrupt() will cause a
master abort if it is called before the memory enable bit has been
restored.

> --- mainline-msi-init.orig/drivers/net/tg3.c
> +++ mainline-msi-init/drivers/net/tg3.c
> @@ -3561,7 +3561,10 @@ static irqreturn_t tg3_interrupt(int irq
>  	struct net_device *dev = dev_id;
>  	struct tg3 *tp = netdev_priv(dev);
>  	struct tg3_hw_status *sblk = tp->hw_status;
> -	unsigned int handled = 1;
> +	unsigned int handled = 0;
> +
> +	if (tg3_irq_sync(tp))
> +		goto out;

This will break other things.  When we disable interrupts, we set the
irq_sync flag but allow one more interrupt to be generated.  The irq
handler will simply mask off the interrupt when it sees the irq_sync
flag.  With the above change, the irq handler can no longer mask off
this trailing interrupt and you may get screaming interrupts as a
result.

Thanks for reporting this.  I'll try to come up with a good solution.

-
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