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Message-Id: <1214556862.8011.534.camel@pasglop>
Date: Fri, 27 Jun 2008 18:54:22 +1000
From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
To: SathyaNarayanan <sathyan@...mf1.com>
Cc: Stefan Roese <sr@...x.de>, linuxppc-dev@...abs.org,
netdev@...r.kernel.org
Subject: Re: [PATCH] ibm_newemac: Fixes kernel crashes when speed of cable
connected changes
>
> > for (i = 0; i < NUM_TX_BUFF; ++i) {
> > - if (dev->tx_skb[i]) {
> > + if (dev->tx_skb[i] &&
> dev->tx_desc[i].data_ptr) {
>
>
> Why changing the test above ?
>
> The reason for changing this condition is , In any of the case if
> the dev->tx_skb is not containing valid address, Then while clearing
> it you may be resulted in "address voilations". This additional
> condition ensures that we are clearing the valid skbs.
> Further this condition is not in general data flow, So this additional
> condition should not have any impact on performance.
Do you see -any- case where tx_skb[i] and dev->tx_desc[i].data_ptr would
be out of sync ? If that's the case, shouldn't we cleanup instead of
leaving some kind of stale entry in the ring ?
In addition, in pure theory, data_ptr == 0 is a valid DMA address :-) So
I think that part of the patch shouldn't be there.
>
> > dev_kfree_skb(dev->tx_skb[i]);
> > dev->tx_skb[i] = NULL;
> > if (dev->tx_desc[i].ctrl &
> MAL_TX_CTRL_READY)
> > @@ -2719,6 +2719,10 @@ static int __devinit
> emac_probe(struct of_device *ofdev,
> > /* Clean rings */
> > memset(dev->tx_desc, 0, NUM_TX_BUFF * sizeof(struct
> mal_descriptor));
> > memset(dev->rx_desc, 0, NUM_RX_BUFF * sizeof(struct
> mal_descriptor));
> > + for (i = 0; i <= NUM_TX_BUFF; i++)
> > + dev->tx_skb[i] = NULL;
> > + for (i = 0; i <= NUM_RX_BUFF; i++)
> > + dev->rx_skb[i] = NULL;
>
>
> Why not use memset here too ?
> Yes, It was valid to use memset here. I can send the modified
> patch for it.
Please do, thanks.
Cheers,
Ben.
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