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gianfar: Revive SKB recycling 

Before calling gfar_clean_tx_ring() the driver grabs an irqsave
spinlock, and then tries to recycle skbs. But since
skb_recycle_check() returns 0 with IRQs disabled, we'll never
recycle any skbs.

It appears that gfar_clean_tx_ring() and gfar_start_xmit() are
mostly idependent and can work in parallel, except when they
modify num_txbdfree.

So we can drop the lock from most sections and thus fix the skb
recycling.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Anton Vorontsov 2009-11-10 14:11:10 +00:00 committed by David S. Miller
parent 836cf7faf8
commit a3bc1f11e9
1 changed files with 19 additions and 12 deletions
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31
drivers/net/gianfar.c
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@ -1928,14 +1928,11 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
/* total number of fragments in the SKB */
nr_frags = skb_shinfo(skb)->nr_frags;
spin_lock_irqsave(&tx_queue->txlock, flags);
/* check if there is space to queue this packet */
if ((nr_frags+1) > tx_queue->num_txbdfree) {
/* no space, stop the queue */
netif_tx_stop_queue(txq);
dev->stats.tx_fifo_errors++;
spin_unlock_irqrestore(&tx_queue->txlock, flags);
return NETDEV_TX_BUSY;
}
@ -1998,6 +1995,20 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
lstatus |= BD_LFLAG(TXBD_CRC | TXBD_READY) | skb_headlen(skb);
/*
* We can work in parallel with gfar_clean_tx_ring(), except
* when modifying num_txbdfree. Note that we didn't grab the lock
* when we were reading the num_txbdfree and checking for available
* space, that's because outside of this function it can only grow,
* and once we've got needed space, it cannot suddenly disappear.
*
* The lock also protects us from gfar_error(), which can modify
* regs->tstat and thus retrigger the transfers, which is why we
* also must grab the lock before setting ready bit for the first
* to be transmitted BD.
*/
spin_lock_irqsave(&tx_queue->txlock, flags);
/*
* The powerpc-specific eieio() is used, as wmb() has too strong
* semantics (it requires synchronization between cacheable and
@ -2225,6 +2236,8 @@ static int gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue)
skb_dirtytx = tx_queue->skb_dirtytx;
while ((skb = tx_queue->tx_skbuff[skb_dirtytx])) {
unsigned long flags;
frags = skb_shinfo(skb)->nr_frags;
lbdp = skip_txbd(bdp, frags, base, tx_ring_size);
@ -2269,7 +2282,9 @@ static int gfar_clean_tx_ring(struct gfar_priv_tx_q *tx_queue)
TX_RING_MOD_MASK(tx_ring_size);
howmany++;
spin_lock_irqsave(&tx_queue->txlock, flags);
tx_queue->num_txbdfree += frags + 1;
spin_unlock_irqrestore(&tx_queue->txlock, flags);
}
/* If we freed a buffer, we can restart transmission, if necessary */
@ -2548,7 +2563,6 @@ static int gfar_poll(struct napi_struct *napi, int budget)
int tx_cleaned = 0, i, left_over_budget = budget;
unsigned long serviced_queues = 0;
int num_queues = 0;
unsigned long flags;
num_queues = gfargrp->num_rx_queues;
budget_per_queue = budget/num_queues;
@ -2568,14 +2582,7 @@ static int gfar_poll(struct napi_struct *napi, int budget)
rx_queue = priv->rx_queue[i];
tx_queue = priv->tx_queue[rx_queue->qindex];
/* If we fail to get the lock,
* don't bother with the TX BDs */
if (spin_trylock_irqsave(&tx_queue->txlock, flags)) {
tx_cleaned += gfar_clean_tx_ring(tx_queue);
spin_unlock_irqrestore(&tx_queue->txlock,
flags);
}
tx_cleaned += gfar_clean_tx_ring(tx_queue);
rx_cleaned_per_queue = gfar_clean_rx_ring(rx_queue,
budget_per_queue);
rx_cleaned += rx_cleaned_per_queue;