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authorAnton Vorontsov <avorontsov@ru.mvista.com>2009-11-10 14:11:10 +0000
committerDavid S. Miller <davem@davemloft.net>2009-11-11 19:03:36 -0800
commita3bc1f11e9b867a4f49505ecac486a33af248b2e (patch)
tree026512ce0362e0f13f0c35d2fc6bc01d2498a2ed
parent836cf7faf8c75743477ed6ed341cce491f3183fb (diff)
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>
-rw-r--r--drivers/net/gianfar.c31
1 files changed, 19 insertions, 12 deletions
diff --git a/drivers/net/gianfar.c b/drivers/net/gianfar.c
index fde430a0b84b..16def131c390 100644
--- a/drivers/net/gianfar.c
+++ b/drivers/net/gianfar.c
@@ -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;
}
@@ -1999,6 +1996,20 @@ 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
* uncacheable mappings, which eieio doesn't provide and which we
@@ -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;