netdev - Re: [patch 06/10] tulip: fix shutdown DMA/irq race

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Message-ID: <20070327133154.GA7157@colo.lackof.org>
Date:	Tue, 27 Mar 2007 07:31:54 -0600
From:	Grant Grundler <grundler@...isc-linux.org>
To:	akpm@...ux-foundation.org
Cc:	jeff@...zik.org, netdev@...r.kernel.org, grundler@...isc-linux.org,
	val_henson@...ux.intel.com
Subject: Re: [patch 06/10] tulip: fix shutdown DMA/irq race

On Mon, Mar 26, 2007 at 09:47:25PM -0800, akpm@...ux-foundation.org wrote:
> From: Grant Grundler <grundler@...isc-linux.org>
> 
> IRQs are racing with tulip_down().  DMA can be restarted by the interrupt
> handler _after_ we call tulip_stop_rxtx() and the DMA buffers are unmapped.
>  The result is an MCA (hard crash on ia64) because of an IO TLB miss.  The
> long-term fix is to make the interrupt handler shutdown aware.

I don't know why this patch is surfacing again now.
I believe Val has addressed the problem with the "long-term" fix described.

thanks,
grant

> Signed-off-by: Grant Grundler <grundler@...isc-linux.org>
> Acked-by: Valerie Henson <val_henson@...ux.intel.com>
> Cc: Jeff Garzik <jeff@...zik.org>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> 
>  drivers/net/tulip/tulip_core.c |   31 +++++++++++++++++++++----------
>  1 file changed, 21 insertions(+), 10 deletions(-)
> 
> diff -puN drivers/net/tulip/tulip_core.c~tulip-fix-shutdown-dma-irq-race drivers/net/tulip/tulip_core.c
> --- a/drivers/net/tulip/tulip_core.c~tulip-fix-shutdown-dma-irq-race
> +++ a/drivers/net/tulip/tulip_core.c
> @@ -734,23 +734,36 @@ static void tulip_down (struct net_devic
>  #endif
>  	spin_lock_irqsave (&tp->lock, flags);
>  
> +	/*
> +	  FIXME: We should really add a shutdown-in-progress flag and
> +	  check it in the interrupt handler to see whether we should
> +	  reenable DMA or not.  The preferred ordering here would be:
> +
> +	  stop DMA engine
> +	  disable interrupts
> +	  remove DMA resources
> +	  free_irq()
> +
> +	  The below works but is non-obvious and doesn't match the
> +	  ordering of bring-up. -VAL
> +	*/
> +
>  	/* Disable interrupts by clearing the interrupt mask. */
>  	iowrite32 (0x00000000, ioaddr + CSR7);
> +	ioread32 (ioaddr + CSR7);	/* flush posted write */
>  
> -	/* Stop the Tx and Rx processes. */
> -	tulip_stop_rxtx(tp);
> +	spin_unlock_irqrestore (&tp->lock, flags);
>  
> -	/* prepare receive buffers */
> -	tulip_refill_rx(dev);
> +	free_irq (dev->irq, dev);	/* no more races after this */
> +	tulip_stop_rxtx(tp);		/* Stop DMA */
>  
> -	/* release any unconsumed transmit buffers */
> -	tulip_clean_tx_ring(tp);
> +	/* Put driver back into the state we start with */
> +	tulip_refill_rx(dev);		/* prepare RX buffers */
> +	tulip_clean_tx_ring(tp);	/* clean up unsent TX buffers */
>  
>  	if (ioread32 (ioaddr + CSR6) != 0xffffffff)
>  		tp->stats.rx_missed_errors += ioread32 (ioaddr + CSR8) & 0xffff;
>  
> -	spin_unlock_irqrestore (&tp->lock, flags);
> -
>  	init_timer(&tp->timer);
>  	tp->timer.data = (unsigned long)dev;
>  	tp->timer.function = tulip_tbl[tp->chip_id].media_timer;
> @@ -776,7 +789,6 @@ static int tulip_close (struct net_devic
>  		printk (KERN_DEBUG "%s: Shutting down ethercard, status was %2.2x.\n",
>  			dev->name, ioread32 (ioaddr + CSR5));
>  
> -	free_irq (dev->irq, dev);
>  
>  	/* Free all the skbuffs in the Rx queue. */
>  	for (i = 0; i < RX_RING_SIZE; i++) {
> @@ -1747,7 +1759,6 @@ static int tulip_suspend (struct pci_dev
>  		tulip_down(dev);
>  
>  	netif_device_detach(dev);
> -	free_irq(dev->irq, dev);
>  
>  	pci_save_state(pdev);
>  	pci_disable_device(pdev);
> _
-
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