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authorLinas Vepstas <linas@austin.ibm.com>2006-10-10 16:14:29 -0500
committerJeff Garzik <jeff@garzik.org>2006-10-11 04:04:26 -0400
commit9cc7bf7edf50a8a6b456b337aff97fe780ae369b (patch)
tree9512ef8f08a21ab7fa9398fdd31f1ad1810a4702 /drivers/net/spider_net.c
parent68a8c609b3071c2441fa64f584d15311f2c10e61 (diff)
downloadop-kernel-dev-9cc7bf7edf50a8a6b456b337aff97fe780ae369b.zip
op-kernel-dev-9cc7bf7edf50a8a6b456b337aff97fe780ae369b.tar.gz
[PATCH] powerpc/cell spidernet refine locking
The transmit side of the spider ethernet driver currently places locks around some very large chunks of code. This results in a fair amount of lock contention is some cases. This patch makes the locks much more fine-grained, protecting only the cirtical sections. One lock is used to protect three locations: the queue head and tail pointers, and the queue low-watermark location. Signed-off-by: Linas Vepstas <linas@austin.ibm.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: James K Lewis <jklewis@us.ibm.com> Signed-off-by: Jeff Garzik <jeff@garzik.org>
Diffstat (limited to 'drivers/net/spider_net.c')
-rw-r--r--drivers/net/spider_net.c95
1 files changed, 43 insertions, 52 deletions
diff --git a/drivers/net/spider_net.c b/drivers/net/spider_net.c
index e429abc..f8d7d0d 100644
--- a/drivers/net/spider_net.c
+++ b/drivers/net/spider_net.c
@@ -646,8 +646,9 @@ static int
spider_net_prepare_tx_descr(struct spider_net_card *card,
struct sk_buff *skb)
{
- struct spider_net_descr *descr = card->tx_chain.head;
+ struct spider_net_descr *descr;
dma_addr_t buf;
+ unsigned long flags;
int length;
length = skb->len;
@@ -666,6 +667,10 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
return -ENOMEM;
}
+ spin_lock_irqsave(&card->tx_chain.lock, flags);
+ descr = card->tx_chain.head;
+ card->tx_chain.head = descr->next;
+
descr->buf_addr = buf;
descr->buf_size = length;
descr->next_descr_addr = 0;
@@ -674,6 +679,8 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
descr->dmac_cmd_status =
SPIDER_NET_DESCR_CARDOWNED | SPIDER_NET_DMAC_NOCS;
+ spin_unlock_irqrestore(&card->tx_chain.lock, flags);
+
if (skb->protocol == htons(ETH_P_IP))
switch (skb->nh.iph->protocol) {
case IPPROTO_TCP:
@@ -691,42 +698,17 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
return 0;
}
-/**
- * spider_net_release_tx_descr - processes a used tx descriptor
- * @card: card structure
- * @descr: descriptor to release
- *
- * releases a used tx descriptor (unmapping, freeing of skb)
- */
-static inline void
-spider_net_release_tx_descr(struct spider_net_card *card)
-{
- struct spider_net_descr *descr = card->tx_chain.tail;
- struct sk_buff *skb;
- unsigned int len;
-
- card->tx_chain.tail = card->tx_chain.tail->next;
- descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
-
- /* unmap the skb */
- skb = descr->skb;
- if (!skb)
- return;
- len = skb->len < ETH_ZLEN ? ETH_ZLEN : skb->len;
- pci_unmap_single(card->pdev, descr->buf_addr, len,
- PCI_DMA_TODEVICE);
- dev_kfree_skb(skb);
-}
-
static void
spider_net_set_low_watermark(struct spider_net_card *card)
{
+ unsigned long flags;
int status;
int cnt=0;
int i;
struct spider_net_descr *descr = card->tx_chain.tail;
- /* Measure the length of the queue. */
+ /* Measure the length of the queue. Measurement does not
+ * need to be precise -- does not need a lock. */
while (descr != card->tx_chain.head) {
status = descr->dmac_cmd_status & SPIDER_NET_DESCR_NOT_IN_USE;
if (status == SPIDER_NET_DESCR_NOT_IN_USE)
@@ -746,11 +728,13 @@ spider_net_set_low_watermark(struct spider_net_card *card)
descr = descr->next;
/* Set the new watermark, clear the old watermark */
+ spin_lock_irqsave(&card->tx_chain.lock, flags);
descr->dmac_cmd_status |= SPIDER_NET_DESCR_TXDESFLG;
if (card->low_watermark && card->low_watermark != descr)
card->low_watermark->dmac_cmd_status =
card->low_watermark->dmac_cmd_status & ~SPIDER_NET_DESCR_TXDESFLG;
card->low_watermark = descr;
+ spin_unlock_irqrestore(&card->tx_chain.lock, flags);
}
/**
@@ -769,21 +753,31 @@ static int
spider_net_release_tx_chain(struct spider_net_card *card, int brutal)
{
struct spider_net_descr_chain *chain = &card->tx_chain;
+ struct spider_net_descr *descr;
+ struct sk_buff *skb;
+ u32 buf_addr;
+ unsigned long flags;
int status;
spider_net_read_reg(card, SPIDER_NET_GDTDMACCNTR);
while (chain->tail != chain->head) {
- status = spider_net_get_descr_status(chain->tail);
+ spin_lock_irqsave(&chain->lock, flags);
+ descr = chain->tail;
+
+ status = spider_net_get_descr_status(descr);
switch (status) {
case SPIDER_NET_DESCR_COMPLETE:
card->netdev_stats.tx_packets++;
- card->netdev_stats.tx_bytes += chain->tail->skb->len;
+ card->netdev_stats.tx_bytes += descr->skb->len;
break;
case SPIDER_NET_DESCR_CARDOWNED:
- if (!brutal)
+ if (!brutal) {
+ spin_unlock_irqrestore(&chain->lock, flags);
return 1;
+ }
+
/* fallthrough, if we release the descriptors
* brutally (then we don't care about
* SPIDER_NET_DESCR_CARDOWNED) */
@@ -800,12 +794,25 @@ spider_net_release_tx_chain(struct spider_net_card *card, int brutal)
default:
card->netdev_stats.tx_dropped++;
- if (!brutal)
+ if (!brutal) {
+ spin_unlock_irqrestore(&chain->lock, flags);
return 1;
+ }
}
- spider_net_release_tx_descr(card);
- }
+ chain->tail = descr->next;
+ descr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
+ skb = descr->skb;
+ buf_addr = descr->buf_addr;
+ spin_unlock_irqrestore(&chain->lock, flags);
+
+ /* unmap the skb */
+ if (skb) {
+ int len = skb->len < ETH_ZLEN ? ETH_ZLEN : skb->len;
+ pci_unmap_single(card->pdev, buf_addr, len, PCI_DMA_TODEVICE);
+ dev_kfree_skb(skb);
+ }
+ }
return 0;
}
@@ -857,27 +864,19 @@ spider_net_xmit(struct sk_buff *skb, struct net_device *netdev)
{
struct spider_net_card *card = netdev_priv(netdev);
struct spider_net_descr_chain *chain = &card->tx_chain;
- struct spider_net_descr *descr = chain->head;
- unsigned long flags;
-
- spin_lock_irqsave(&chain->lock, flags);
spider_net_release_tx_chain(card, 0);
if ((chain->head->next == chain->tail->prev) ||
- (spider_net_get_descr_status(descr) != SPIDER_NET_DESCR_NOT_IN_USE) ||
(spider_net_prepare_tx_descr(card, skb) != 0)) {
card->netdev_stats.tx_dropped++;
- spin_unlock_irqrestore(&chain->lock, flags);
netif_stop_queue(netdev);
return NETDEV_TX_BUSY;
}
spider_net_set_low_watermark(card);
spider_net_kick_tx_dma(card);
- card->tx_chain.head = card->tx_chain.head->next;
- spin_unlock_irqrestore(&chain->lock, flags);
return NETDEV_TX_OK;
}
@@ -893,16 +892,11 @@ spider_net_xmit(struct sk_buff *skb, struct net_device *netdev)
static void
spider_net_cleanup_tx_ring(struct spider_net_card *card)
{
- unsigned long flags;
-
- spin_lock_irqsave(&card->tx_chain.lock, flags);
-
if ((spider_net_release_tx_chain(card, 0) != 0) &&
(card->netdev->flags & IFF_UP)) {
spider_net_kick_tx_dma(card);
netif_wake_queue(card->netdev);
}
- spin_unlock_irqrestore(&card->tx_chain.lock, flags);
}
/**
@@ -1930,10 +1924,7 @@ spider_net_stop(struct net_device *netdev)
spider_net_disable_rxdmac(card);
/* release chains */
- if (spin_trylock(&card->tx_chain.lock)) {
- spider_net_release_tx_chain(card, 1);
- spin_unlock(&card->tx_chain.lock);
- }
+ spider_net_release_tx_chain(card, 1);
spider_net_free_chain(card, &card->tx_chain);
spider_net_free_chain(card, &card->rx_chain);
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