Re: [WIP] p54: deal with allocation failures in rx path

[Larry Finger <Larry.Finger@lwfinger.net>]

Larry Finger wrote:
> @@ -224,6 +236,7 @@ static void p54_tx_qos_accounting_free(s
>                 struct p54_tx_data *data = (void *) hdr->data;
> 
>                 priv->tx_stats[data->hw_queue].len--;
> +               WARN_ON(priv->tx_stats[data->hw_queue].len < 0);
>         }
>         p54_wake_queues(priv);
>  }
> 

The new WARN_ON did _NOT_ trigger when the len went negative.

The only other place where len could be decremented is through
txhdr->backlog. I noticed that the p54common.c had

txhdr->backlog = current_queue->len;

This was replaced in txrx.c by

txhdr->backlog = priv->tx_stats[queue].len - 1;

Was this intentional?

To test if this is the problem, I added the following hunk:

@@ -840,6 +853,7 @@ int p54_tx_80211(struct ieee80211_hw *de
        txhdr->crypt_offset = crypt_offset;
        txhdr->hw_queue = queue;
        txhdr->backlog = priv->tx_stats[queue].len - 1;
+       WARN_ON(!priv->tx_stats[queue].len);
        memset(txhdr->durations, 0, sizeof(txhdr->durations));
        txhdr->tx_antenna = ((info->antenna_sel_tx == 0) ?
                2 : info->antenna_sel_tx - 1) & priv->tx_diversity_mask;

This WARN_ON did trigger just before txq[6].len went negative. I'm now
testing with that changed as follows:

@@ -839,7 +852,8 @@ int p54_tx_80211(struct ieee80211_hw *de
        }
        txhdr->crypt_offset = crypt_offset;
        txhdr->hw_queue = queue;
-       txhdr->backlog = priv->tx_stats[queue].len - 1;
+       txhdr->backlog = priv->tx_stats[queue].len;
+       WARN_ON(priv->tx_stats[queue].len < 0);
        memset(txhdr->durations, 0, sizeof(txhdr->durations));
        txhdr->tx_antenna = ((info->antenna_sel_tx == 0) ?
                2 : info->antenna_sel_tx - 1) & priv->tx_diversity_mask;

This WARN_ON did not trigger, but I still had the queue len go negative.

One other question: struct p54_burst is defined in lmac.h, but it
doesn't seem to be used anywhere. Will it be needed later?

Larry